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mitchco

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  1. Thanks @sem115 One will require an application to "host" the Dirac Live Processor (DLP) plugin. An oldy but goody is VSTHost on Windows. I just tried loading the DLP VST plugin and was successful. There are several VST host's available, some free, some $$'s, some standalone and some integrated with other music player software. The trick is routing the audio. I ran out of time to try DLP in this configuration. But essentially, you will want to route Qobuz or Roon's output through the application hosting the DLP plugin and then out to the DAC and rest of the system. Perhaps other members here have tried this approach and can assist.
  2. Dirac 2 is the latest version of Dirac’s Digital Room Correction (DRC) technology. In this article, I walk through the steps of using Dirac to optimize the response of the Purifi SPK4 demo kit that I recently reviewed here on Audiophile Style. Can we make an already great sounding speaker sound better in my room? And by better I mean smoothing out the low frequency response below the room’s transition (Schroeder) frequency, making small, broad band tonal adjustments in the midrange and top end to be a bit smoother and finally a timing correction of the impulse response. The short answer is yes we can. We can see the improvement in the measured frequency and timing response. I can also hear an audible difference with a tighter, more clear sounding bass, smoother overall frequency response and a more coherent timing response (i.e. stereo imaging and depth of field) across a larger sweet spot. With Dirac 2, designing and generating a partial correction from about 600 Hz on down below the room’s transition frequency is as simple as it gets. The sonic benefits are instant, much smoother bass response with no huge peaks and dips that plague virtually every room below Schroeder frequency. Full range correction comes with improved phase response (i.e. imaging and depth of field) covering a wider sweet spot, more on that in the subjective listening section. Before the walkthrough, let’s talk a bit about Dirac’s room correction technology. Technology Discussion First, what audio problem is room correction technology designed to solve? The unfortunate reality is that below a room’s transition (a.k.a. Schroder) frequency, the room controls the bass response arriving at your ears, not the loudspeakers. Due to modal resonances we get wildly different bass responses depending on where we place speakers in rooms relative to the listening position: The above chart is from Floyd Toole’s Audio Science Article. As Floyd says, “In the investigation of many rooms over the years, I would estimate that something like 80% have serious bass coloration.” For those of us that take acoustical measurements of audio systems, this comes as no surprise. The peaks and dips in the low frequency response is typical and exists in virtually every room that was not specifically designed using proper room ratios, aside from construction and acoustic treatments. Room modes are calculated based on one’s room dimensions where room resonances take control of the low frequency response regardless of the speakers being used. I like this Room Mode calculator as you can move the cursor along the frequency scale and it will output a tone at that frequency. If your computer is hooked up to your speakers (careful with the volume!), you can hear the resonances in your room by hovering the cursor over the modes in the graph. It is an ear opening experience and great for training ones ears to know what to listen for. Room modes can sound like “one note bass” where the room mode is so bad, all you hear is the single droning bass note that drowns everything else out. Or the “where did the bass go?” when certain bass notes are played. Or simply just uneven bass, some notes are there, some are gone, and some are too loud. Dirac 2 is designed to smooth out the peaks of the low frequency room response and fill in some of the dips across the listening area. Our ears are more sensitive to peaks than dips. A good primer on why we hear what we hear in small room acoustics as it relates to room correction is James (JJ) Johnston’s, “Acoustic and Psychoacoustic Issues in Room Correction.” Download the PowerPoint if you can. The first 31 slides are worth the read. Dirac uses a “mixed phase” filter approach which is a combination of IIR filters and FIR filters for efficiency. The white paper linked goes into detail behind the design, and can be summarized as: “A first main aim is to control not only the frequency domain properties of the system but also the time domain properties: The impulse responses as measured at different listening positions. In particular, we strive to reduce the “pre-ringings” (pre-echoes) that would otherwise result in an un-natural sound experience. Secondly, we use dynamic models of the sound system that are based on measurements at multiple listening positions. This is important for obtaining a robust design that works over an extended region to provide a large spatial area with good sound quality. Third, we may jointly optimize multiple loudspeakers to better control the sound pressures at different listening positions. This is done by precise phase control of the individual loudspeaker transfer functions at low frequencies. Joint optimization of a set of loudspeakers results in more distinct bass performance, better robustness of the compensation and better control of the impulse responses at different listening positions.” Room correction is a complicated (and mostly misunderstood) subject area. If there is interest, I might write another article to discuss this in more detail as it is not just “eq” that is being applied here (i.e. the time domain properties are equally important). Dirac 2 consists of two pieces of software that work together. The Dirac Live Processer (DLP) is a VST plugin that “hosts” the correction filters in a convolution engine. The Dirac Live application is used to measure your loudspeakers in your room, design the filters, and upload the correction filters to the DLP. One interesting difference to other convolution engines is that the DLP accounts for any latency issues, so when switching the DLP on or off, the audio change is instant as opposed to a ¾ second silence gap with a 65K tap FIR filter. There is also no latency when switching between filters, which makes A/B comparisons easy so you can “bracket” in on your preferred frequency response in a shorter period of time. Since the Dirac Live Processor is a VST plugin, any software music player or Digital Audio Workstation (DAW) that supports the VST plugin architecture can simply load the DLP. In this article, I am using JRiver Media Center 64 Bit DSP audio architecture to host the DLP: I clicked on Manage Plug-ins in JRiver and navigated to where the DLP VST was installed and loaded it. Here we are seeing the DLP loaded into JRiver and active with a correction uploaded into the first of eight slots available. The 2nd piece of Dirac Live is an application that you run on your computer that is mostly “wizard” driven, and steps you through the process of: Connecting and configuring audio I/O Adjusting playback and record levels Select the type of measurements you want to take (i.e. chair, couch area, etc.) Taking the measurements Designing a correction filter whether partial or full range using a target of your preference Examining the results of the correction in a simulation Uploading the correction filter to Dirac Processor Managing measurements, targets, corrections, etc. So let’s perform step 1 of the Dirac Live application wizard in the objective measurements section Objective Measurements For the measurements, I moved the couch and coffee table out of the way and the sub woofers are not active. This is the main screen you see once you have downloaded Dirac Live, installed it and connected to the DLP. Note that you are required to login to your Dirac Live account in order to connect to the DLP. Also, in order for the Dirac Live application to communicate with the DLP, the latter needs to be enabled and actively receiving an audio signal. Meaning that the DLP is enabled in JRiver and music is playing through Dirac Live Processor so it is “active.” Without the DLP being active, the Dirac Live application cannot connect to the DLP. Each step of the wizard comes with a help screen of what to do. It is concise and well written so you can quickly get the hang of what to do. Here we are selecting which recording device to use once we clear the instructions: Here I am using my Lynx Hilo ADC with a microphone preamp and calibrated measurement microphone. I have clicked into the area with the red square and loaded my measurement mics calibration file. In my case, the mic calibration file uses comma separated text whereas Dirac is expecting periods. Easy enough to open in a file editor and replace commas with periods. In most case, like using a UMIK-1 mic, the microphone calibration file will load without any calibration file modifications. Next step is to adjust speaker level and microphone gain settings: I wholeheartedly agree with “keep the master volume at the lowest setting and gradually increase it.” I have pressed play on the left channel and adjusting the levels to be in the “green.” If you have a sound level meter, 75 dB SPL C weighting at the listening position is loud enough and I would not go beyond 85 dB SPL, which to our ears, sounds twice as loud as 75 dB SPL. If you don’t have a sound pressure level meter (even a smart phone SPL app will do), then adjust to a comfortable playback volume. If you feel like covering your ears, then it is too loud. Clicking on next brings up the type of measurement you would like to take. These involve taking multiple measurements, the number of which depending on what type of listening arrangement is selected. The wider the listening area to cover the more measurements one needs to take. So it could be as few as 5 measurements and as many as 17: In this walkthrough, I tried two listening arrangements, a single chair with 5 measurements and the sofa wide imaging with 17 measurements. This is so I could also subjectively compare the two corrections. First lets walkthrough the single chair selection. Single Chair Click on Proceed to Measure: I decided to use the minimum amount of measurements for this setup to test out Dirac’s algorithms. Above, I just completed the 5th measurement. The idea is that you move the microphone relative to the placement as indicated in the diagram. In general, the mic placement is 40 to 60cm apart per placement and you can choose whatever order you want take the measurements by clicking into the location on the diagram. Note that the precise placement of the mic to the location is not crucial. As a side note, it is good to temporarily remove any objects between the speakers and the microphone positions, including the chair and or sofa at the listening position. We measure and correct for the loudspeaker and room with an unobstructed path and nothing around the microphone so we are getting a clean as a sound field as possible. We don’t want to correct for any reflections between the speakers and mic due to a coffee table or around the mic itself as that will lead to a colored sound. It is best to measure and correct for the unobstructed sound field first and then return the furniture to its original locations. Finally, I recommend getting a real boom mic stand for taking measurements. You can grab one at your local music store or order online. The little mic stand that comes with the UMIK-1 while cute, is not helpful as you need to place it on something to get ear height, which means reflections (i.e. colorations) are getting into the mic. Each time you take a measurement, Dirac will output a sweep signal starting with the left channel, then the right channel, then back to the left channel. So 3 sweeps per location times 5 locations equals 15 sweeps: Here is the screen you see when taking a measurement, with the abort button in case you need to abort the measurement for whatever reason. Once you are happy with your measurements, click on proceed to filter design: Dirac suggests a target curve based on the measurements you took. Generally speaking, one is looking for a downward tilt of the frequency response at the listening position. This is because most forward firing drivers in loudspeakers start off as omnidirectional at low frequencies and become progressively more directional at higher frequencies. The rising bass energy yields a steady state room curve with a downward tilt. How much tilt? The scientific research that Sean Olive (and earlier Floyd Toole) conducted over years shows that a slope of 20 Hz to around -8 to -10 dB at 20 kHz is what most listeners prefer as neutral sound. A high level overview of that can be found in, The History of the Harman Target. While the overview also discusses headphone target curves, which have the same preferred target (transfer function) as loudspeakers in rooms, it also discusses loudspeaker target preferences. More importantly, there are a listing of AES papers that one can get the details on. One example is the Subjective and Objective Evaluation of Room Correction Products: Of course, you are free to implement any target curve you want, but a good starting place is to use Dirac’s suggestion and if it is a bit too bright or dark sounding, one can always adjust the curve. Note that a flat in-room response is not the ideal target response as it will be exceedingly bright sounding. If you read through Sean Olive’s presentation referenced above, and in these slides, it is actually the tilting frequency response that our ears perceive as flat or neutral sounding at the listening position (see slide 25). Well worth the read. Looking at the analysis chart below, we are seeing the processed 5 measurements down to left and right, plus the suggested target curve: So these wonderful little 15L bookshelf Purifi speakers have a frequency response with the -3dB limits at 25 Hz and 22 kHz. Outstanding for such a small 2 way bookshelf speaker. Ctrl-click both checkboxes, top right to get both curves to display. Note the room resonances showing up below 300 Hz in my room and if I were to choose a partial correction frequency, which I have done a bit later, I would choose 600 Hz and below to be corrected as we can see by 600 Hz the “up and down” peaks and dips are no longer an issue. In fact, having been using room correction since 2011, and having seen many other people’s measurements of loudspeakers in rooms, 600 Hz seems to be the most common point where the room starts to have an influence on the frequency response and gradually taking over completely by the time one reaches the rooms transition frequency, which in my room is at 200 Hz. As linked earlier, you can use this room mode calculator to calculate your room’s transition frequency. See the bottom right panel where it says on one side measured and corrected on the other side? Dirac has already calculated the correction in the background and by unchecking the measurement and checking on the correction, we get: As one can see, a considerably smoother response. So not only smoothing out below 600 Hz, but also bringing down the broadband rise from 2 kHz to 5 kHz when compared to the original measure. Still a little dip left at 100 Hz, but as folks may have read in JJ’s presentation, our ears are not as sensitive to narrow band dips as compared to peaks, so all good. Note the (very) slight channel level difference in the top end frequency response. As @Flavio has commented here, “Dirac Live 2.x algorithm might even slightly compromise on FR response of one of the speakers in favor of the best possible phase coherence between them that is important for imaging.” We will be exploring that in the subjective listening section. Next I clicked on “Proceed to filter export” and here I am exporting the correction filter to DLP. I can give it a name and description: Click on Export filter and Dirac takes a few seconds to upload the filter: Once uploaded, I can navigate to JRiver where I have the DLP VST loaded and enabled: It is recommended to leave the delay and gain compensation on. I also adjusted the gain slider to about -6 dB for headroom management. The meters will peak red if there is any clipping, which I experienced none. I could probably go to 3 dB of headroom management, but I have plenty of power on tap. OK, now listening to music! But before I comment on the sound, I also wanted to try a partial correction to 600 Hz as can be seen as a foreshadow in slot 2 ☺ Partial Correction I can go back to my saved measurements, don’t forget to save! And back to the filter design section. Creating a partial correction is dead easy. All I need to do is grab the right marker that was previously at 22.1 kHz and drag the marker to the left to about 600 Hz: So the frequencies between 25.7 Hz and 587 Hz will be corrected and the rest left alone. Note, if I were using Dirac and Digital Room Correction for the first time, this is where I would suggest starting with a partial correction. This way one can focus your attention on just listening for an improved bass response and not a change in overall frequency response. We proceed to filter export and load the filter into the 2nd slot: As one can see, I have several filter designs loaded, but here we are focused on the partial correction. Let’s move on to the sofa, wide imaging measurements. Sofa Wide Imaging After you have selected Sofa and Wide imaging, proceed to take the measurements: In this screen shot, I am on my last of 17 measurements. 3 sweeps per measurement times 17 measurements = 51 sweeps. Whew, that’s a lot and took me about 15 minutes to get through them all. I did not use a measuring tape. I just took a guess as to where the mic should go at each location, either raising or dropping the mic height and placing the mic at the front or back of my sofa, which I have temporarily moved out of the way. Note these 17 measurements covered a 6ft wide x 2ft deep x 2ft of height variability where my couch is. At any time you can re measure a position. Again we proceed to filter design. I just used the same default target as before and then switching to the corrected filter response: The response is so smooth I need to have a look without the target obscuring the correction: Wowser! That’s based on 17 measurements around my three seat couch area. To give an idea of all of the responses around the area, Dirac has a “spread” feature that allows you to see this if you check the box in the lower right hand: Those are 17 measurements made of left and right channels at the various locations around my 6’ x 2’ couch area. One can see the variability of the measurements based on position and again, by about 500 Hz, there is less variability as the loudspeaker is in control of the frequency response and not so much the room. Switching the view to impulse response: The corrected impulse is on the left and measured impulse on the right. As one can see on the left, the impulse or transient response is a cleaned up version of the measurement. Vertical scale is amplitude and horizontal scale in milliseconds. The big vertical spike is the direct sound from the loudspeaker arriving at the microphone without any reflections. The smaller spikes, after the direct sound are early reflections. The corrected impulse response shows a clean spike and very little spikes (i.e. early reflections) after. Sound travels roughly 1 foot per millisecond, so it becomes easier to understand that right after the direct sound, are the reflections (i.e. diffraction) off the speaker cabinet and then the speaker stand and anything else nearby like floor bounce or front/side wall bounce or ceiling bounce, all of those reflections are contributing to the sound, after the direct sound and our ears have a pattern to integrate those early reflections (i.e. the Haas effect) and understand amplitude and frequency response. It is a complicated topic as it involves so many aspects of why we hear what we hear in small room acoustics; standing waves, room resonances, early reflections, later reflections, room ratios, room construction and treatments, digital filtering, FIR, IIR, our ears non-linear response to both amplitude and frequency response, the Haas Effect, which reflections are good, which are bad, and on it goes. At this stage, I just wanted to show that Dirac works in the time domain. Given multiple measurement locations, one can understand that the sound and reflections arrive at different times and in different ways depending on the mic location relative to the loudspeakers. Using the concept of superposition and what we know about the physics of how standing waves respond in a rooms, we can work out the pattern and therefore correct for a wider sweet spot, which is what the 17 measurements are about. Dirac knows the phase relationships between the measurements plus taking the speakers as a pair into account, is used to calculate the correction filter. A note about target curves. While I have been using Dirac’s suggested target curve based on the measurements, you are free to create your own target curves. As mentioned above in the Subjective and Objective Evaluation of Room Correction products, the most preferred or accurate or neutral response is one that is 20 Hz to about -8 or -9 dB at 20 kHz. Here I have dialed that in the target curve by grabbing the control points of the target and dragging them down a bit to get the desired target response. Of course, one can add and delete control points along the target (right click on the target). One can also save and load targets from the menu at the top left, beside the help icon. I was able to catch Dirac’s old correction computation as it was calculating the new correction along the new target: You can see how much I pulled down the target. It is not a lot, but is an audible difference. Just my personal preference. Of course, export to DLP and start listening: I have 7 of the 8 slots filled with a variety of filters to listen to. Before we get to the subjective listening section, here are a couple of “spot” verification measurements I made with REW. REW Verification Measurements This is just a “spot” verification of the correction. It is a loopback measurement where I am feeding the digital output of REW sweep test tone into the JRiver’s ASIO digital line input and it passing through Dirac Live Processor with the correction engaged and fed out my Hilo DAC to the Purifi amp and speakers, picked up by the measurement mic, through a mic preamp, Hilo ADC and routed to REW’s digital input. Then the measurement can be displayed in a variety of graphs to look at different viewpoints of the acoustic measurement of the room and loudspeakers. This is not a “gated” measurement as we do want the room’s low frequencies in the picture and using REW’s default impulse window of 500 milliseconds. One should note that this is not fully representative as it is one measurement made at the middle listening position. Ideally, I would take 17 measurements at the same or similar locations as I did in Dirac and vector average them in REW. And even then it still will not be quite the same as Dirac is applying more than just a vector average. However, it does verify that Dirac is doing what it is supposed to do: On the top are the Purifi SPK4 speakers measured at the listening position from my previous article and the bottom with the Dirac correction enabled. The speakers are in a 9ft equilateral triangle. I just split the screens apart to make it an easier comparison. Let’s start with the low frequency response and work our way up to the high frequencies, calling out the differences. Dirac was able to extend the low end frequency response in my room to below 30 Hz. -3 dB down at 22 Hz for the left speaker (as it is more in the corner of the room) and 28 Hz for the right speaker, as it is almost center in the room and does not get the corner boundary reinforcement. Compare that to -3 dB down at 32 Hz on the left and 45 Hz for the right speaker without correction. Looking at the 30 Hz to 60 Hz region on the correction, both speakers are matched closer together in amplitude response for a more solid bass response. This is in addition to being smoother and less peaky at 36 Hz for the left uncorrected speaker and 55 Hz for the right uncorrected speaker. Remember, our ears follow the “envelope” of the frequency response with our ears more attuned to peaks rather than narrow dips in frequency response. The big correction comes at 80 and 90 Hz as one can see in the uncorrected response. The total swing from the lowest point at 90 Hz to the highest point at 110 Hz is 23 dB. To our ears, a bass note playing at 90 Hz will be ¼ as loud as compared to a bass note at 110 Hz and vice versa. I.e. a bass note at 110 Hz will sound 4 times as loud as compared to the bass note at 90 Hz. This is classic room modes and we all got em, albeit at different frequencies dependent on one’s room ratio. While the dip is still there, it has been reduced by over 50% to ±5 dB which is very close to studio tolerance of ±3 dB. I suspect it would be in this range if I vector averaged 17 measurements in REW. Good enough for a spot check. Note Dirac pulls downs the peaks at 234 Hz, 461 Hz and 1.2 kHz. We also see a smoother response from 2 kHz to 5 kHz which just pulls down the brightness of the AMT tweeter just a bit. Finally, we extend the response a bit past 10 kHz. From good to great goes the speaker’s in-room frequency response, not only smoother but extended on both ends of the frequency spectrum. Let’s look at the timing or step response. Dirac makes a claim that “misaligned drivers in multi-way loudspeakers can be corrected by automatically applying different delays to different frequency ranges.” So let’s verify this claim by first looking at the step response of the uncorrected Purifi SPK4: So the spike (doublet) at time 0ms on the horizontal scale is the AMT tweeter and the negative going portion is perfectly blended into the start of Purifi’s PTT6.5 woofer. Classic or “textbook” passive crossover design. However, not truly time aligned. Let’s look at the corrected response: Here we see the drivers are perfectly time aligned with the straight vertical “step” as both drivers response are arriving at your ears at the same time. Claim verified. There is just a hint of preringing at the beginning of the step response. I know it is not audible, as I have experimented in detail with greatly exaggerated preringing examples in my book, “Accurate Sound Reproduction using DSP.” Completely innocuous with the main goal of time alignment of drivers achieved. While phase and time alignment are not supposed to be audible, in my listening tests I have performed over the years, they are to my ears. Excess phase correction in the low frequency response is audible to my ears as is time alignment of drivers. Perhaps a future article on more discussion around this, but suffice to say, Dirac is doing its job in the time domain. Subjective Listening Note the dual Rythmik F18 subs were not used in the evaluation. I did have to check a couple of times as the amount of sub 30 Hz output from the Purifi’s PTT6.5” (sub)woofer is astonishing. However, I do intend to use the subs in Part 2 of using Dirac Live Bass Management in an upcoming review. The first thing I wanted to try was use my reference bass recording, Madonna’s, “Power of Goodbye” to test out Dirac’s partial correction up to 600 Hz in my room. The reason I like using this recording for testing bass frequencies is because it has long sustained bass notes. This makes it easier to hear the room’s resonances. As expected, there are some bass notes that practically disappear and other bass notes that dominate the sound in my room. Enabling Dirac brings the level of bass notes to the same amplitude and the bass response is solid and powerful on each sustained note. It is still amazing to me as when I was working in recording studio control rooms, the only way to control room modes was the geometric and acoustic design of the control room. Aside from the room controlling reflections and acoustic treatments, the bass traps required to deal with very low frequencies at long wavelengths meant for a special acoustic design: a room within a room. The bass would pass through the shell of the inner room and be “trapped” in the outer shell so as not to pass back into the inner room. You can imagine the construction costs. Now at the flick of a digital switch, for truly a fraction of the cost, one can have the same smooth solid bass response at every frequency. What a time to be alive! Another fav track I have for listening to bass evenness is Rebecca Pidgeon’s “Spanish Harlem”. A very nice Bob Katz recording and master of an acoustic bass guitar, in addition to Rebecca’s wonderful vocal rendition. Spanish Harlem, in the key of G, uses the classic 1, 4, 5 progression. Here are the frequencies of the fundamental notes of the bass: So without Dirac enabled, the 62 Hz to 82 Hz range of bass notes are really down in sound pressure level and the 110 Hz bass note literally sounds like a “coke bottle” resonance it is so loud and dominating in my room. Enabling Dirac, brings back the proper level balance in the low end where each bass note is heard succinctly and even in level. When your ears starting tuning in, it really becomes apparent the differences. Having nice solid, even sounding bass arriving at your ears is a real treat. The reason why I say our ears need to tune in is because we are so used to listening to uneven bass, we are simply used to it and don’t give it a second thought. Remember JJ’s presentation. But once you hear how smooth it can be with your existing loudspeakers in your room, it is impossible to go back. Just the ability to smooth out the bass response is well worth the price of the software, aside from the additional benefits we are about to discuss. Let’s try the full range correction, but for the single seat. I find it a great boon being able to switch on and off DLP while listening in real time. There is no delay or interruption of sound or glitches of any sort, just a smooth and transparent switch. This makes is really easy to compare uncorrected to corrected or comparing different correction filters. This makes it easy to hear the differences instantly and then appreciate them over a period of time. SRV and Double Trouble’s, “Tin Pan Alley” is one of my favorite blues recordings. It was the first song and first take of the recording for the album that captured the feeling so well. When I was recording, I was always trying to get bands to “practice” before we recorded, but I was secretly recording as invariably the first take is sometimes the best take. Case in point this tune, wow! Great dynamic range that pulses with the emotion of the song. Great bass line that sounds nice and smooth with Dirac enabled. But what really stood out for me is the Stevie’s strat sound with the Fender Leslie Vibrotone giving it that rotating stereo effect. It sounds so clear and precise with Dirac enabled, almost spooky hearing SRV fingers sliding up and down the strings with the Leslie effect enabled. Goosebumps territory. I switched over to the sofa, wide imaging corrections and re-listened to the above tracks, switching from single seat to wide imaging, at the same time moving around on my couch. I wanted to see if the 5 measurements versus 17 measurements were audible in some way to my ears. I found the changes to be subtle with the 17 measurements offering a bit more clarity in the overall sound, especially moving to edges of my couch area. I must say the phantom center image was perfect between the speakers, no wandering of the center image versus frequency. Excellent spatial imaging with a 3D depth of field I only hear from speakers that are time aligned with both channels closely matching in frequency response. Even with the 5 measurements, Dirac’s room correction algorithm appears to be quite robust and does not require an overabundance of measurements to get good even bass and smooth overall frequency response. While I enjoyed the benefits of partial correction, my preference is for the full range correction in two areas. One advantage was smoothing any midrange and high frequency “peaks” which with the Purifi SPK4 demo kit were small, but makes a difference not only in the smoothness of the sound, but also the vocals and instruments in the midrange “sat” in the overall mix where I thought they should be rather than sitting in front of the mix being a bit forward in sound from 2 kHz to 5 kHz region. Finally, I like the full range correction as I can dial in a preferred target of simply what I am used to listening to. Personally, I find most speakers sound too “bright” to my ears and confirmed by my measurements. While I have performed some speaker reviews here on Audiophile Style, I have had many pass through my listening room and all too bright for my tastes. The only one that had the preferred response out of the box is the Dutch and Dutch 8c. The KEF LS50 a very close 2nd, but just voiced a little too bright in the 2 kHz range, but Dirac would do a nice job of toning that back just a bit. Maybe we will see that in a future article. Conclusion Well folks, it is 2020 and if you are not using digital room correction, at least partial correction to smooth the bass frequencies in your listening room, you are missing out on a simple but audible optimization. At a retail price of US $349, coupled with a US $100 calibrated measurement mic like the UMIK-1, this is a “no brainer” upgrade to your existing system that is both measureable and audible in a positive way. For existing Dirac 1.x customers, it is a free upgrade. In fact, while I am biased towards advanced DSP room correction, I know of no other way to achieve this level of sonic improvement for dollars spent. Dirac 2 has made the process of applying room correction as simple as possible. Setup the mic, take measurements and click next, next, next, through the wizard and be listening to the smooth bass tones in the shortest time possible. They have made it difficult for anyone to mess up ☺ It is interesting that Dirac chose the VST plugin route, but I can see that their market is not only audiophiles but also the semi/Pro audio market as virtually every Digital Audio Workstation (DAW) uses Steinberg’s VST software plugin architecture. Dirac also provides AU and AAX plugins for Mac users and for DAW’s that use that plugin architecture like ProTools. You can find Dirac Live on the largest marketplace for plugins at KVRAudio. I have all but given up going to audio shows due to the fact that below the (hotel) room’s transition frequency, the room dominates the bass response regardless of the type of or how expensive the loudspeakers used are. As Floyd Toole’s research shows that bass subjectively accounts for 30% of how we judge speakers sound quality. And “ANY loudspeaker can sound better after room EQ, so long as it competently addresses the bass frequencies - this is not a guarantee, but really is not difficult for at least the prime listener” In the case of Dirac, the sofa, wide imaging selection extends the bass sweet spot across at least three seats. To answer the inevitable question, which sounds better, Acourate, Audiolense or Dirac, since I have evaluated all three. I will say they all improve the low frequency response of virtually any system in any room. One can model the “ideal” loudspeaker in an “ideal” room and then it is a matter of which room reflections and how many are positive for the sound quality and how many are not, are taken care of. There is significant scientific research on this topic and with quite a bit of agreement. Having said that, all three DSP room correction software employ different strategies to arrive at the “ideal” result. In the case of Dirac, if you are looking for the shortest path to the result, this is it. That’s also a limitation. Other than different target responses, everything else is pretty much closed off and taken care for you with no user adjustable controls. I did not try Dirac 1.x, so have no way of comparing other than reading through the Dirac 1.x 42 page manual. I must say Dirac has greatly simplified the use of their room correction software for Dirac 2. I did not have to open a manual, I just started using it. I found the improvements made to my loudspeakers in my room by Dirac were audible to my ears and measurable in a positive way. Recommended. Mitch “Mitchco” Barnett. I love music and audio. I grew up with music around me, as my mom was a piano player (swing) and my dad was an audiophile (jazz). My hobby is building speakers, amps, preamps, etc., and I still DIY today. I mixed live sound for a variety of bands, which led to working full-time in multiple 24-track recording studios. Over 10 years, I recorded, mixed, and sometimes produced over 30 albums. I wrote a book on, “Accurate Sound Reproduction using DSP” and run an Accurate Sound Calibration service.
  3. The good ol Lynx Hilo has an excellent ADC. I can share measurements, but one can also find them here: https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-lynx-hilo-adc-part-2.3596/ Also: https://www.gearslutz.com/board/showpost.php?p=14477582&postcount=1850 The Hilo is still in the top spot for AD DA loop testing linearity. You should be able to find a used one for around the price you are suggesting or maybe a bit more. Good luck!
  4. Thanks Ted! Both sound quite good on the NAD's if I understand your question correctly. If I use the Windows 7.1 config and play each channel individually or listen to Redscapes 7.1 demo, the virtualized locations are exactly to be as expected. Redscapes 2 channel virtualization sounds great too, like being in front of ideal speakers in an ideal room. I enjoy the tone of the NAD's as well as I like the Harman target curve for headphones. Yes, I heard the Smyth Realiser older version some time ago. Does work really well. But as you say, quite the price point difference 🙂 If one can handle a bit of diy, there is the Impulcifer that does what Smyth Realiser does and maybe worth some investigation. Very cool about your music room! I hope you show us when it is done. Kind regards, Mitch
  5. Hi Jeffrey, yes it does work. See attached. As far as I have been able to test, any number of channels up to 7.1 in Roon are mapped exactly up to 7.1 in Redscape. I tried Out Of Your Head and spent literally 30 minutes trying to get it to work to no avail and gave up. Output errors, crashes, lockups, wrong sample rate play speed (chipmunks 🙂 Maybe I am not giving it a fair shake, but I usually can get things to work pretty quickly... Besides, it is missing the head tracker which I think really completes the illusion IMO.
  6. I prefer listening to music (and movies) over loudspeakers rather than headphones. However, I listen to headphones every day, traveling, at the office, or late at night when the family sleeps. I have a love/hate relationship with headphones. I love the personal sound system at my ears, but I hate the “in the head” sound as a result of wearing headphones. Some folks are not bothered by the “in the head” sound or actually prefer it. I appreciate everyone’s preference. For me, Redscape provides an excellent 3D representation of a stereo or multichannel mix similar to sitting in front of stereo speakers or multichannel system, but in an ideal “virtual” room. Coupled with accurate and precision head tracking, the illusion is so real, sometimes I forget I am wearing headphones. The best part? Affordable and easy to use. Part of my loudspeaker bias is spending +10 years as a recording/mixing engineer with speakers in front of me at all times. Folks may realize how many hours go into mixing down tracks using reverb, digital delays, the Haas effect, impulse response of acoustics spaces, and other spatial effects, to create or “paint” a 3D soundscape in “stereo.” This is in addition to adjusting the level and tonal balance for each track. It is all an elaborate illusion. Redscape does a great job, to my ears, at rendering that elaborate illusion convincingly out of my head. Technology Discussion Redscape’s 3D virtualization software can be purchased standalone or with a head tracker. Depending on the listening scenario, I evaluated both. For example, while working in front of the computer, I make use of the 3D virtualization software while listening to music, but with no head tracker. For critical listening and/or watching movies, I am in sitting at my normal listening position in front of the loudspeakers. But rather than listening to the loudspeakers, I am listening over headphones with Redscape on and head tracker engaged. Eyes closed if just listening to music. The software employs a virtual audio device driver that supports low latency WASAPI and ASIO devices. This means that if you are using Windows or a music player or gaming application, you can select the appropriate driver and get low latency audio, which is important in relation to the head tracker. The Redscape software operates at 96 kHz sample rate also to ensure low latency audio. All DSP calculations are performed using 64 bit floating point math. With the head tracker on, I found no lag that I could discern and amazing accuracy and precision where just a degree or two of head movement is tracked. When you move your head even a bit, it tracks with the stereo positioning as if you were sitting in front of your own stereo. To my ears, as I moved my head, the location and tonal changes sounded just like in front of my stereo system. Cool virtualization. I wanted to get a better understanding of how the 3D virtualization technology worked, so I reached out to Ryan, the designer of Redscape’s software. I asked Ryan, "So you are taking discrete channels of audio and using your algorithm, giving it a 3D virtualization mix?" “Yes, exactly. Each discrete channel, of up to 7.1 channels of input, is individually spatialized in the proper location. The Redscape algorithm does this over single driver (per ear) headphones by simulating what your ears hear when sounds come from different directions. It's all based on the Head Related Transfer Function Imagine a loudspeaker that is placed to the right of you. You'd first hear the sound in your right ear, followed by the sound that wrapped around your head at the left ear. There is both a timing and a frequency response difference between the ears (higher frequencies are shaded by your head). In addition to this, Redscape simulates a real room. Direct to reverberant ratio is part of what helps you to determine the distance you are from a sound source. The room simulation helps to get the sound out of your head, floating around you. How quickly a room decays, effectively how damped a room is, can be modified within Redscape. The head tracker attaches to most any pair of headphones. It uses an accelerometer and a gyroscope to track your head orientation. Redscape takes your current head orientation, and renders what each ear would hear from those virtual locations. Movies and games are an obvious use case, where you have 5.1 or 7.1 channels that can be spatialized, but I also really enjoy using Redscape for 2 channel music. I find tracks with fun stereo panning can work really well, like "Whole Lotta Love." Same with the hard-panned stereo Beatles tracks. When listening to 2 channel, Redscape doesn't attempt to turn it into a surround sound experience, it just renders the two channels in front of you as intended by the artist.” I feel the explanation is clear and what differentiates Redscape from other products when taking into account the approach used and what the design goals are. I like that Ryan pointed out for stereo listening this is not a “surround sound” experience. This is key, as the point is to imagine being seated in front of an “ideal” stereo system in an “ideal” room. The virtualization of which is what one is listening to over headphones. So not only includes HRTF, but also room simulation and head tracking. All of which contributes to the 3D virtualization effect. And for the price, makes for an effective solution to eliminate the “in the head” headphone sound. Set up and Configuration Redscape’s help site has step by step instructions on how to install and configure the software and attach the head tracker. I am not going to replicate all the details here, but rather show how my system is setup and configured. The head tracker comes in a small package with numerous straps to secure the tracker to the headphone and clips to secure the 3 meter USB cable to the headphone cable, plus a zipper sleeve to bundle the USB cable with the headphone cable. I fastened the head tracker to my Visio HP50’s with the supplied fasteners and zipper system. Took all of 5 minutes. I downloaded and installed the software which was a simple installation taking a couple of minutes. Launching Redscape software and clicking on the gears icon: The Audio I/O is the first property window we want to configure. Here I have chosen WASAPI input and output. I am using a Lynx Hilo as the converter and we can see the Redscape Virtual Audio Device selected as input and the output going to my Hilo DAC with various latency and buffer settings. That’s pretty low and should not notice any latency between the head tracker and audio (I didn’t notice any latency in use). I can get even lower latency by choosing ASIO and minimum latency in my Lynx Hilo USB Control Panel: And then selecting the gear icon in Redscape and changing the Audio I/O to ASIO, we see the latency reduced next to nothing: Very low audio latency for head tracking accuracy. Great for game mode, but it takes many tens of milliseconds of latency before we start to notice any lag. For now, we can close the Audio I/O window and choose a source. In my case, I configured JRiver and Roon, both worked perfectly with Redscape. Here I am choosing the Redscape ASIO audio device in JRiver: Change JRiver’s output format to 5.1: This is because if the source is two channels, it passes through as stereo. But if I am watching movies, then 5.1 channels are fed directly to Redscape for 3D virtualization. I would select 7.1 if I had any media encoded in 7.1, but the movies I have are Dolby Digital 5.1. This way I can watch or listen to whatever content and not have to adjust any further controls. That’s it, ready to listen! For Roon, from the menu, select Options, then Audio: Enable Redscape. Once enabled, click on Device Setup which will bring up the dialog on the right. However, one needs to scroll down and click on advanced to get to the channel layout. Here I selected 7.1 and is simply mapped to the Redscape 7.1 channels, so no matter what source content I select and how many channels, I am going to get the right channels sent to Redscape. Also note that in Roon I am using WASAPI. Redscape has instructions for setting up 7.1. Channels in Windows: Same as JRiver and Roon, we want to setup for all 7.1 channels to be mapped to Redscape 7.1 virtualization. The only wrinkle here is to click on Properties and then Advanced and set the highest bit rate possible at 44.1 kHz, which is likely 24 or 32 bits. We also need to configure Redscape for WASAPI. Now that Redscape audio is setup and configured on all of my digital sources, we can now calibrate the head tracker. Launch the Redscape application. The head icon on the main page UI should be flashing. The idea is to hold your head still until the flashing stops. This can take 10 seconds. Once the flashing stops, level and center your head between your speakers, imaginary or real, and click on Center on the main UI. You can also click on the head icon and the head tracker window opens. This is useful to ensure your head movements are tracked in the right directions, which depends on how you attached the head tracker, i.e. which side the cable runs down plus the setting in the Head Tracker tab. When you move your head, it should be a real time mirror image of your movements. You may have to flip the switch in the Tracker Orientation if you look up and the head tracker image looks down. The final piece of configuration I performed while listening over a period of time, in addition to adjusting the Room and Volume controls, is fine tuning my HRTF: It is worth doing once you have tuned into the 3D virtualization sound for a while as one can “focus” the 3D virtualization I guess is the best way to describe it. It is amazing how focused in the 3D space in front of you it can be. I left all other controls in their default positions. But a few points should be noted, such as the head tracker tab which has options to swap the left and right channels based on how you attached the head tracker to your headphones and which side the cable is on. The options tab gives you a few choices for swapping the rear channels with side surrounds plus options for putting Redscape in the task bar and showing tooltips. The speakers tab is set to 60 degrees, which is the industry standard for stereo and multichannel mixes. On the main Redscape window there is also an icon for a fully configurable parametric equalizer (PEQ) with 10 PEQ’s so one can tailor the response of your headphones to a preference or follow a set of predetermined PEQ’s for your particular headphones that you may find online. I did not use the PEQ as I am happy with the native response of my headphones as described below. I am using the relatively inexpensive NAD HP50 headphones with Roomfeel. These headphones conform to the Harman Target Curve, in which I have eq’d more or the less the equivalent for my loudspeakers. So it comes as no surprise that the 3D virtualization sounds similar to my speakers, including subs! Sure, I could not “feel” the room shake like I would with the subs turned on, but the virtualization made it sound “like subs” instead of “in the head” bass sound. More on that in the subjective listening. Now that we are all setup and configured, time to listen to some music and other media content. Subjective Listening Astute readers will note that this is my first review that does not contain some form of objective measurements. I could use my binaural mics like I have used before to record what I am hearing, but Redscape has a demo site to try the effect yourself. To tune in, try the Intro demo first as it identifies each 7.1 virtual speaker spatially located in the right position when listening to Redscape 3D over stereo headphones. These are my subjective listening impressions after about 80 hours of media listening spread over a month time frame. It is just a summary with some highlighted content to describe how it sounded to me. On regular rotation, Madonna’s mix sounds great with Redscape. The stereo illusion and depth of field sounds like my speakers in my room, except without the room modes! Not only do you get a sense of speaker directionality, but also the feel of being in a room as the sound is more diffuse. It does not sound “phasey”, but rather that diffuse sound that differentiates being in a room rather than in your head. The bass sounds like it is coming from my subs in the room rather than in my head. While the house isn’t shaking, it is still a convincing effect. When I toggled Redscape off and on during the song, I immediately kept switching it back to the 3D sound. At first it takes a little time to orient yourself to what you are listening to, but now I can’t go back to “in the head” sound. Awolnation, “The Best” is an absolutely crushed DR4 affair. But if you turn it up loud, the +12 dB 36 Hz bass peak should pressurize your room if you have subs or speakers with woofers that can push some air. It blows my mind that the sub bass sounds like it is coming from in front of me and in a room. Redscape has done a great job in balancing low sub bass and room sound with the rest of the tonal range. It is there, really deep sounding but not under or overpowering the rest of the mix. As one can see on the spectral analysis chart, there is a +12 dB peak at 36 Hz relative to other frequencies. Given it is mostly a constant drone is why it should pressurize your room if ones speakers (and headphones) can do it. The HP50’s I use measure flat down to below 20 Hz, and using the Harman target curve, plenty of low frequency response, if you can get a good fit on these un-ergonomic cans. On the right is the end of the waveform display. Can you say clipped! I don’t listen to much classical music, but when I saw 2001: a space odyssey, my mind was blown just sitting there in the theatre as the movie ended. Then The Blue Danube started playing. That did it for me. It was the perfect music ending to a mind blowing film. I had a huge smile on my face. While the original motion picture soundtrack does not have a lot of low end, it makes up for it in the performance and the venue. Turning the volume up on The Blue Danube, the sound stage is like being at the concert hall with the sound floating in front of you with seemingly infinite depth of field with the reverb in the concert hall. Really an amazing recording and performance. The Redscape 3D virtualization was excellent on the 5.1 soundtrack I have on digital video. I can listen to this on repeat for a while ☺ Along the same lines, both Bladerunner soundtracks translate really well with Redscape’s 3D virtualization. I used the original Vangelis soundtrack with the long syth notes to fine tune the HRTF. The movies were excellent as well. Another tune on regular rotation for me, Patricia Barber, Regular Pleasures. A very good recording with wide dynamic range. Patricia’s voice sounds excellent with Redscape enabled. No phasey sound or attempt at a surround sound, but rather listening to ideal stereo speakers in an ideal room. The 3D spatialization effect sounds like you’re at the jazz club listening. I am listening to it right now as I am writing this ☺ Switching back and forth with Redscape on/off, I tried listening for any digital artifacts with Redscape on and could not hear any degradation in sound quality at all. The drums and cymbals sound crisp, the s’s on Patricia’s voice are sharp and clear, even with the room diffusion. The bass and bass drum were solid and extended as there seems to be no limitation in frequency response. Just a wonderful listening experience to my ears. Note that this was with the virtualization only as I was not sitting in front of the speakers, but heads down at a computer station, writing this article. On the other end of the spectrum from Space 2001, comes the fast paced animation and loud “Spider Man into the Spider-Verse.” The Sony Pictures intro is the new THX with killer sound rising to a crescendo that sounds like my room just imploded… over headphones – cool! Look at that sub level on the Redscape LF channel! All I need now is to attach a couple of bass shakers to my couch. Yah, that’s it, shouldn’t wake the family late at night! This film is the epitome of the modern animation genre, so well recorded and mixed, sounds great over Redscape with precision 3D rendering of the scenes. Really well done. Just for fun, sometimes my better half and I watch NFL and NCAA football. Sometimes I watch just to fall asleep 😉 So I wanted to check out what it sounds like over headphones with Redscape engaged. Sounds really good. I found I had to turn down the Room a bit as the broadcast has some effect on it to give it a bit of a room sound, so it was too much room with the default setting. Otherwise, full bandwidth and again, sounds like being in front of the stereo watching the screen. A good sense of being there. I have Qobuz integrated with Roon. So when I remember a tune, I can search it up, like this one. I first heard Chaiyya Chaiyya in the movie, “Inside Man.” A cool Spike Lee joint and this was the intro song. I love the rhythm and the vibe. Towards the middle of the song is the start of low frequency drop kicks. Again sounds like subs in a room. Huge soundstage. Really well mixed. It’s a little long, but gives one time to identify all of the voices and instruments as it is a layered recording. I love rock concerts. Cream Live at Royal Albert Hall has some incredible audio, just an excellent “live” recording. Quite the illusion with the eyes closed. In some ways feels like being at the concert hall sitting in front of the band about halfway back into the hall. The bass is nice and deep, the drums have punch, Eric’s guitar rips and wails and the vocals are spot on plus the “Hall” sounds great! You can hear the trademark “Albert Hall” echo off of Ginger’s drums – great stuff. Conclusion I really enjoy Redscape’s 3D virtualization software and head tracker. I think it is unique from the standpoint of providing a 3D virtualization of an “ideal” stereo or multi-channel system in an “ideal” room that one is sitting in front of. The HRTF algorithm, room simulation and head tracker all contribute to forgetting one is actually listening over headphones. Pretty cool effect. The best part, it is affordable and takes about 5 minutes to get up and running. The “out of the head” effect and virtualization of speakers with a front sound stage is well done to my ears. The ability to fine tune the HRTF to focus the sound really helps to get the last bit of 3D virtualization tuned. It really does sound like you are in a virtualized room listening to a stereo/multi-channel system way beyond what I have experienced before with a variety of virtualization systems, including cross feeds and surround virtualization. I believe the combo of Redscape’s HRTF algorithm, room simulation and accurate/precision head tracker is what gives the 3D virtualization a good sense of realism. I also like the simplicity of set up and not having to calibrate using in-ear microphones or Creative’s approach of taking pictures of ones ears or listening to one’s room/speakers, that maybe not ideal. For example, room modes or slap echo off bare walls or speakers that aren’t up to the task. Redscape’s approach bypasses all of that and makes it easy to just plugin, calibrate the head tracker in a couple of seconds and then you are listening to 3D sound. I did not run into any issues during the evaluation. Everything worked perfectly with JRiver, Roon and Windows audio. I mostly adjusted the amount of Room to taste depending on the source material. Also, I just left the input on WASAPI and output on ASIO, that way I get Win10 sources in addition to JRiver Roon/Qobuz integration without having to do anything in Redscape. For USD $200 for both the 3D virtualization software and head tracker, it is hard to go wrong. You can get a real sense of what it will sound like by trying Redscape’s demo page with your headphones (sans head tracker). I recommend starting with 7.1 Intro as it 3D virtualizes each speaker in the right location in your headphones. This will help orientate what you are hearing as you have now have both a visual and audible cue. For me, no more “in the head” sound! I hope you are enjoying the music in 2020! Mitch “Mitchco” Barnett. I love music and audio. I grew up with music around me, as my mom was a piano player (swing) and my dad was an audiophile (jazz). My hobby is building speakers, amps, preamps, etc., and I still DIY today. I mixed live sound for a variety of bands, which led to working full-time in multiple 24-track recording studios. Over 10 years, I recorded, mixed, and sometimes produced over 30 albums. I am into Digital Signal Processing (DSP) and run an Accurate Sound Calibration service.
  7. Mike, could be... these are as good as it gets for a a small cone driver. Kind regards, Mitch
  8. Satish, thanks! Yes, the PTT6.5 produces low bass at low to medium volumes. You don't need to pump up the volume for it to produce. Extremely linear. Using JRiver's loudness control (which is calibrated and I always use) even at really low background levels sounds "full." Kind regards, Mitch
  9. Hi @Victor Varga Yes. I have been using the headphone output on the Hilo since 2012 in a variety of active 3 way systems. Sometimes on the bass drivers, one time on compression drivers and waveguides. You will either need some cable adaptors or make your own cable with the proper connectors for your setup. I did the latter and have had no issues, sounds very good! Kind regards, Mitch
  10. Hi Jeff, As a side note, Acourate and Audiolense can run on a Mac by using Bootcamp/Windows or by using Parallels+Asio4All (Parallels does not support Asio drivers directly). Some folks borrow a PC laptop to take the measurements, design and generate the FIR correction filters, but then host them on a Mac with a convolution engine. Yes, I am an old school stereo kind of guy, so no surround, except on headphones. Wrt Purifi's drivers and moving mass. You may want to check out Purifi's tech page: https://purifi-audio.com/tech/ and the Dec 10th post on, "A fast driver needs a light cone. Or does it?" Also, Lars had this to say when asked about this, "Essentially, mass mostly affects sensitivity and has nothing to do with speed - a tough myth to bust. The combination of very long stroke and a 4 layer coil adds 10-12g of mass compared to a shorter stroke 2 layer coil. The long stroke surround adds approx 1g more than a conventional shorter stroke half roll and the strengthening of the cone adds perhaps a gram as well. The 4 layer coil increases the motor strength making the driver suitable to work even in small sealed boxes in combination with the strong cone and robust surround (to handle the high back pressure). All of this has not compromised the excellent midrange performance. Or in other words, all of these design choices have resulted in this combination of sub, woofer and mid with ultra low distortion." Hope that helps.
  11. Hi Jeff, I use both Acourate and Audiolense DSP. In my current setup, I am using Audiolense to crossover to my dual subs. Audiolense uses linear phase digital crossovers so that they sum perfectly in both the frequency and time domains. Here is a walkthrough of how I did it: https://audiophilestyle.com/ca/ca-academy/ integrating-subwoofers-with-stereo-mains-using-audiolense-r712/ Audiolense also time aligns the subs to mains. Both Acourate and Audiolense are capable for multichannel setups as well. I would have to find it, but I remember one person who triamped their mains, had multiple subs and multichannel setup using Audiolense. Used something like 16 channels... I have worked in LEDE studio control rooms before and am I fan 🙂 Happy New Year to you as well!
  12. Agreed. When it comes to speakers, there are two main factors based on the current research out there, mainly by Floyd Toole/Sean Olive and team. One is that the speaker should have smooth on and off axis response (which the LS50's have) and the other his how low you want to go. Of course there are other attributes, but these are the main two that make the difference in most systems. According to Toole's research, bass accounts for about 30% of the factor weighting in subjective evaluations of sound quality. Personally, if I have enough room, I can't live without subs 🙂 If you can wait, I would be inclined to see where those Purifi 6.5" woofers end up in a kit and/or commercial product as their woofer is next gen from anything else I have heard. And if it that does not go low/loud enough for you after listening, then maybe subs are in order... Good luck!
  13. Modern DSP software can make it incredibly easy to bi-amp or tri-amp with little error on the behalf of the user if you possess some basic knowledge. I have written a number of articles of doing just that with both Acourate and Audiolense. I have indeed ripped out passive XO's in numerous speakers and achieved better than the passive XO that was in them. This is coming from a diyAudio enthusiast, who spent a great deal of time designing and building passive XO's for years. The reason is that modern DSP software uses linear phase digital XO's. Linear phase XO's sum perfectly in both the frequency and time domains. This short article explains the advantage: http://www.acourate.com/XOWhitePaper.pdf Further, the XO slopes are steep, so the drivers acoustic bandpass is "convolved" with the digital XO slope and therefore the digital XO slope becomes the acoustic slope. Here is a quick example to illustrate the point: While this is a 3-way digital XO'd system, here were are looking at a band-pass digital XO filter (light blue trace) that is set for 45 Hz and 630 Hz. The drivers are JBL 15" woofers and the blue and red traces are the acoustic measurements of both left and right drivers. What you see is that the drivers acoustic response is greater than the digital XO bandpass at both ends of the spectrum. So when the drivers acoustic response is "convolved" with the digital XO bandpass filter, it is a) within the operational limits of the driver and b) the acoustic response is now the digital XO bandpass, which if you have read the linked article above on "thoughts about crossovers", sum perfectly in the frequency and time domain. Both on and off axis from an acoustic perspective. For sure, it take some know how, but for me I would never go back to passive XO's. Aside from the description above, with digital XO's one can then time align the drivers so all of the direct sound from the speaker is arriving at your ears all at the same time. You can also linearize each driver and convolve the linearization into the digital XO before applying an overall frequency response adjustment. This also allows one to put big solid state amps directly connected to the woofer for ultimate low frequency control, but choose a small wattage tube of Class A amp of your choice on the mids and/or tweeter. This is all done in the digital domain and requires multi-channel DAC's depending on bi-amp or tri-amp setup. I currently run a tri-amp setup with dual Rythmik F18 subs crossed to dual 15" JBL woofers per cab and then crossed to a compression driver/waveguide combo using a flea watt Class A Pass amp. So the convolution filter is hosted in JRiver or Roon's convolution engine and I use all 3 stereo analog outputs of my Lynx Hilo connected directly to 6 amps and control the volume inside JRiver and Roon. With some finesse, one can achieve the ideal minimum phase response of a loudspeaker at the listening position with a frequency response tailored to your preference, time aligned drivers, including subs, reduce group delay to below audibility, no extra AD/DA conversion, and flat phase response at the listening position, with both channels perfectly matched in both the frequency and time domains to give you a perfect listening window into one's music. Personally, I love it! Lots of fun. Happy 2020!
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