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Everything posted by mitchco

  1. 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
  2. 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.
  3. 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!
  4. 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!
  5. 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!
  6. Merry Xmas @Abtr As an owner of the KEF LS50's and crossed over to dual Rythmik L12 subs with a digital active XO at 100 Hz, they sound really good! Certainly does offload the IMD. As to which one sounds better is a matter of opinion, and how loud one listens, but it is hard ignore the vanishing low distortion of the PTT6.5 woofer... Looking at the measured distortion spec of the LS50 at Soundstage! it comes on pretty quick at 200 Hz. The Rythmik L12's are a good pairing, but maybe dual Rythmik F8's positioned close to the LS50's would offer better even performance as they can be crossed higher e.g. 200 Hz. Kind regards, Mitch
  7. Merry Xmas @blue2 What I received is a demo kit for the evaluation of the technology. As mentioned above to firedog, I don't think there is "finished kits" for sale. But I could be wrong and worth a note to Purifi to confirm. Kind regards, Mitch
  8. Merry Xmas @firedog As far as I know, Purifi's plan is to OEM drivers, electronics, PSU's and DSP. There wasn't any mention of selling full kits. The SPK4 and SPK5 plans do include everything to build, but like you say not a kit delivered as a "flat pack."
  9. Merry Xmas Bryan. Do you have a box modelling program like Leap or BassBox Pro? Here is a list here if you don't. You would have to enter in the Thiele/Small parameters of the driver into these tools to see if it would work in a sealed box config. Also, you can use Leap to design the crossover to something like an Esotar to see if that would work. Kind regards, Mitch
  10. I enjoy reviewing innovative loudspeakers like the Dutch and Dutch 8c and the Kii THREE. I also spend time on diyAudio’s loudspeaker forums looking at what to build next or modify what I have, essentially looking for the “next big thing.” I noticed Purifi’s woofer getting good reviews on diyAudio and ASR. On Audiophile Style, @DuckToller wrote an article on meeting the folks from Purifi in Munich with @The Computer Audiophile. Reading those really peaked my interest. HiFiCompass’ review of the PTT6.5 shows the woofer measuring considerably better than its competitors, especially in reduced distortion, both THD and IMD. This puts Purifi’s PTT6.5 woofer into a class on to itself. Now I really wanted to hear this woofer! Before I could track down a pair, I received a note from DuckToller asking if I would be interested in evaluating the woofers in kit form. A short while later I received a demo kit and a stereo IET400A amplifier. I must say upfront that this technology represents a major audible improvement in mid/bass clarity and low frequency extension. Meaning, I have not heard a 6.5” woofer go this low or sound this clean, at concert level volumes. To my ears, the Purifi PTT6.5 woofer is the “next big thing” in transducer technology. Coupled with Purifi’s 1ET400A amplifier, this is the lowest distortion sound I have heard from any amp/speaker combo of this size in my listening room. Purifi SPK4 Loudspeaker Demo Kit and 1ET400A stereo amplifier (top view). Technology Discussion Much has been written about the technical aspects of Purifi’s PTT6.5 woofer technology including HiFiCompass’s extensive objective measurements linked above and Amir’s objective measurements of the 1ET400A amplifier. My review will be a combination of a few objective loudspeaker measurements in my room and subjective listening impressions. My review is aimed at the consumer and DIY audio enthusiasts wondering what these technology advancements are and how they translate into a superior listening experience. A 6.5” woofer is not big and has real world limitations on how low of a frequency the driver can realistically reproduce, yet still sound clear in the bass and midrange as volume increases. While our ears are relatively insensitive to low frequency harmonic distortion, they are more sensitive to intermodulation distortion (IMD). How can a small driver output significant low frequency energy yet still sound clean in the lower mids and midrange? This is the crux of the technical dilemma that no loudspeaker designer/manufacturer has been able to crack… until now. I thought I would ask Purifi’s Lars Risbo, one of the brains behind the PTT6.5 woofer, to describe their design approach on how they were able to obtain such low measured intermodulation distortion numbers: “Our PTT6.5 woofer is the result of about 4 years of research. It has been a fruitful teamwork between Bruno, Carsten, Morten, and myself. This has resulted in a design that is vastly different from conventional drivers. In short, we have been on a crusade against all sources of intermodulation distortion. Psychoacoustics has correctly shown that our ears are not that sensitive to pure harmonic distortion – especially in the bass. However, our ears are way less forgiving when it comes to IMD when listening to complex music program material. Since it is impossible to only generate harmonic distortion without IMD, it has been necessary to reduce all nonlinear mechanisms in a speaker. The most known source of IMD is the position dependent force factor Bl(x) which we have made ruler flat over +-6mm excursion (+-10mm at -10% Bl). Less known is the current and frequency dependent modulation of the force factor (aka force factor modulation, flux modulation, reluctance force) which we have reduced by up to 40dB over comparable standard motors. Then we have the position dependent inductance which causes a modulation of the drive current, again reduced by a huge factor. A new (re)discovery is the gain modulation caused by the varying radiating area of conventional surrounds – this can cause an amplitude modulation of the midrange by +-10% easily. This has been reduced by orders of magnitude by our very special surround geometry. Finally, an extremely annoying distortion mechanism is the hysteretic memory of the iron in the motor. This distortion leads to a grainy non dynamic sound and lack of ‘black canvas’. We have managed to reduce this distortion by up to 50dB compared to industry benchmark drivers. Interestingly, the exact same hysteretic distortion can be found in class D amplifier output coils. Our 1ET400A amplifier embeds the coil in a control loop with over 70dB loop gain all the way to 20 kHz which effectively removes this distortion. We believe that the class D coil’s hysteretic distortion has been a large part of the bad reputation of early class D designs.” When I asked Lars about how loud I can turn up the demo kit, he had this to say: “How loud? We always end up playing insanely loud due to the lack of distortion (my ears become the limit). The woofer handles 350W IEC long term and survives bottoming (which of course sounds bad). Actually, the 100 hour power tested units have never had damages to the soft parts which is quite unusual (our special surround works like a dream to stabilize the motion). You have +-14mm of mechanical stroke and with the lowered port tuning to 30Hz it takes quite a bit to bottom it. So just fire it up and ease back if you hear bottoming – mostly because it then suddenly sounds bad, it’s not harmful.” Wow. Usually I am careful not to blow up review speakers, but this sounds like a challenge! Kidding aside, very interesting as I have found most bookshelf speakers don’t go very loud before hearing the onset of cone breakup. For example, I own a pair of KEF LS50’s which have a nice voicing, but don’t go very loud (or very low in frequency) before audible distortion is heard as compared to PTT 6.5 (i.e. demo kit). The traditional approach to combat this is to pair satellite speakers with sub(s) to reduce the low frequency load (and IMD) on the small driver. Or in the case of the Dutch and Dutch 8c’s, put two 8” long stroke subwoofers in the back of the stand mount speaker enclosure operating at 100 Hz and below. The PTT6.5 woofer is unique in being able to reproduce a prodigious amount of low frequency energy (i.e. in the 30 Hz range), yet remain absolutely clean sounding throughout the lower mids and midrange. The only comparison I have is using large, stiff cone, short stroke 15” woofers, which is what I use today in my JBL system, in addition to Rythmik dual 18” subs. The (major) disadvantage is that these cabinets tend to be the size of fridges, look fugly and cost more dollars. Further, the 15” drivers can barely make it to an 800 Hz crossover point, whereas the PTT6.5 is crossed over at 2.5 kHz in the demo kit, but can still hit 32 Hz, all delivered with low distortion. The PTT6.5 is a subwoofer, woofer and midrange to 2.5 kHz all in one unit. Of course, it is all relative to size and SPL’s. There is no “replacement for displacement” and my large JBL’s with dual Rythmik 18” subs can easily outperform the PTT6.5 in sheer SPL’s. But, listening at “reference” level of 83 dB SPL, the PTT6.5 sounds unbelievably clean with good low frequency extension and outstanding clarity in the lower mids and midrange. A wide bandwidth, clean sounding, stand mount audiophile monitor it is. Setup and Configuration You can see the size of the subs (not used) relative to the Purifi SPK4 demo kit. I pushed my large JBL’s out of the way (see “the fridge” far left) and placed the SPK4 in the same location, which is also the same location where I have reviewed other speakers. I set them up in a 9 ft. equilateral triangle, toed in to point right at my ears on axis. The Monoprice 24” steel stands are filled with sand and the speakers are doubly isolated from the floor using Vibrapods. One set under the stands, another set under the speakers. I have attached the PDF sheet for the SPK4 Demo Kit, a ported box tuned to 30Hz, which is the same frequency as the woofers Thiel/Small parameters resonance frequency (i.e. Fs). Thus tuned for maximum low frequency extension in a 15 liter bookshelf enclosure. I have also attached the datasheet for the PTT6.5” woofer and 1ET400A amplifier. Just before publication I received an update that there is a SPK5 demo speaker, which I have also attached the data sheet. The passive crossovers are built using premium parts including Jantzen air core inductors. Due to the extremely low distortion of the PTT6.5 woofer, it is important to choose good crossover filter components. Inductors must by air-core. These are heavy duty crossovers crossing over to the AMT tweeter at 2.5 kHz. The Mundorf Air Motion Transformer (AMT) tweeter is well-known for its excellent transient response and outstanding low distortion. A good match for the PTT6.5 as a demo platform. Amir measured the 1ET400A amplifier to output 257 watts @ 4 ohms with THD+N of 0.0002% and 131 watts @ 8 ohms with 0.00019% THD+N. Looking at the impedance graph in the SPK4 app note, we see impedance as low as 5 ohms in the low frequencies and lower mids. Given Lars said that the PTT6.5 can handle 350 watts and with SPK4 system sensitivity of ~ 82 dB SPL @ 2.83Vrms at 1 meter, we should be able to hit concert levels at the listening position (i.e. ~ 95 dB SPL C weighting, slow response) no problem. I am using a Lynx Hilo DAC which measures around 0.001% THD+N. The Hilo’s ADC measures even better and the main reason I use this converter for my DSP loudspeaker measurements and binaural recordings. Suffice to say, all of these distortion levels are well below our audibility threshold in a typical living room listening environment. I connected the Hilo to the 1ET400A amp via its XLR balanced input connections: Putting my ear literally against the AMT tweeter I hear the faintest hiss, dead silence on the woofer. For critical listening, I listen at reference level (i.e. 83 dB SPL C weighting at the listening position). Here is an excellent article on calibrating for reference level and why we listen at this level. With the higher than normal 6.5” woofer sensitivity of 88 dB @2.83v at 1m and 350 watt power handling rating, this makes for one powerful 6.5” woofer. Note that the PTT6.5 data sheet sensitivity is for infinite baffle (2pi) whereas the usual speaker box sensitivity is stated for free space (4pi) - this tradition is a source of much confusion. This means that one should subtract 6 dB from the data sheet to get the free space sensitivity (i.e. the box baffle step is equalized down to the free field response in the passive xover and the tweeter is attenuated accordingly). I am still amazed how the PTT6.5 can cleanly belt it out without any strain every time I listen. The only other way to get that kind of kick is using what I have now, which are short stroke, large stiff cone area, 15” woofers. The “quality” of bass coming from the PTT6.5 sounds like it should be coming from my large JBL’s. It is quite the audible illusion. Of course this is only up to a certain SPL, but much louder than I expected and certainly louder and cleaner than other similar sized loudspeakers, by a good margin. To switch it around a bit, I ended up listening to the amp/speaker combo for days before I pulled out the measurement gear. In fact, this is the longest I have procrastinated to get the measurement mic out. I just wanted to continue listening. So, let’s begin with the listening impressions first and then look at the measurements to confirm what I am hearing. Subjective Listening I have listened to this demo amp/speaker combo for numerous hours over days using a wide variety of source material. Not only my reference recordings that I have linked to in previous articles, but tunes that have a combination of good low bass and midrange elements that would stress the amp/speaker combo to “give it up” in the bottom end and stress the midrange. Driving loudspeakers towards their limits can result in unexpected failures. I have “popped” woofers right out of their gap and instantly “smoked” tweeters into silence with a clipped amp signal. Sometimes it is good to start with material that is dynamically compromised to test the limits. Yotto’s Radiate (DR6) is a good thumping mix with significant bass centered at 39 Hz and highly compressed. So does it sound good? The PTT6.5 can certainly reproduce the deep bass. I can feel the couch vibrating from the 6.5” woofers. Ridiculous you say! I could not believe it myself. Sounds clean with good transient punch on the kick drum and the throbbing bass sounds solid. I cranked it up until 96 dB SPL C weighting at the listening position 9 feet away in 30” x 16.5’ x 8’ room. At that SPL, I just started to notice bottoming out of the woofers on peaks. That’s +13 dB more SPL than reference level, which to our ears sounds over twice as loud. It’s concert level loud! Very rarely do I listen at this level, but it is fun for short periods 🙂 Up until that point, the amp/demo speaker combo sounds crystal clear without the bass and kick drum losing any articulation and the midrange syths still sounding clear and well defined in the mix. Most speakers will tend to “break up” with distortion before reaching their full limits. Again, the PTT6.5” just kept getting louder, showing no strain, and then the bottoming of the woofer is very brief at the limit. Turn the level down a bit, and back to sounding crystal clear. A unique property that I have not heard from any other small transducer. Above on the left is a spectral analysis of the first couple of minutes of Radiate along with a waveform view on the right. Can you say clipped! Significant energy focused in the 40 Hz region. Madonna’s Power of Goodbye (DR8) has an excellent low frequency bass line with long sustained notes. Literally feels like rolling waves as you can feel each wave that has significant energy down to 3 Hz. With my dual Rythmik F18’s I can make the house, couch, and my body vibrate and pressurize the room with this tune turned up. Makes me smile. The PTT6.5 could indeed pressurize my room and make the couch and room vibrate with some body sensation. Really impressive coming from a 6.5” (sub)woofer! At that level Madonna’s lower mids and midrange from her voice and syths still sound clear as a bell while the woofer is able to shake the room a bit on the low notes. This is unheard of from a 6.5” woofer. Mind blown. We can see in the frequency spectrum above, the wave like pulse below 10 Hz. On the right is the waveform which is compressed, but not horrendously clipped like Radiate. Patricia Barber’s, Regular Pleasures (DR15) is a torture test for amps/loudspeakers with its concussive bass drum and sliding bass line. With the punch of DR15, it is downright dangerous for popping woofer cones. It is another recording with significant low frequency energy focused at 40 Hz and good content down below 10 Hz. On my dual F18’s subs the drop note bass drum shakes the house on its foundations after the initial concussive hit. Obviously not on a 6.5” woofer but within its operational limits, sounds very deep, solid and in balance with the rest of the mix. I can still feel the bass and drums sitting on the couch. I am amazed at how low, loud, and clean these woofers can go. They have the same transient impact like my 15” JBL’s have (up to a certain SPL, but way louder than I expected) and the lower midrange is crystal clear. I mean the cleanest I have ever heard. Patricia’s voice is mixed up in level in the overall mix with the drums and bass. The lower midrange and mids from her voice sounds clear with no modulation that I could hear even when cranked right up. I can hear/feel the resonance of the lower mids of her voice unlike I have heard from many a different speaker. On most speakers I have listened to, Patricia’s voice sounds good, but a bit thin and missing the power of her lower midrange register, which I only hear on the large JBL’s… and now the PTT6.5. I could go on, but the above three examples are representative of the continued enjoyment I get listening to this amp/speaker combo. Even blasting for a period of time only barely warmed up the 1ET400A chassis and case. Not once did I hear any strain from the amplification in any way. The top end sounded transparent with excellent transient response. Well, now I am curious how they measure, up close, and from the listening position. Given what I have heard, I expect good low frequency extension with a smooth lower mid and midrange frequency response. Objective Measurements Here is a video of an REW measurement of the right speaker. Turn your sound down to a safe level if your web browser is hooked up to your sound system. If you look closely at the beginning, you can see how much cone excursion is going on starting from 10 Hz on up. Perfectly linear and clean sounding. The first set of measures are 30cm away from the speaker on-axis with the mic positioned between the two drivers. While the room will have its way below Schroeder, (i.e. the room’s transition frequency), I still want to see some representation of bass output. So I don’t gate my measurements and for sure the room is in the picture, but still a very smooth and extended response at both frequency extremes: My room comes into play from about 300 Hz on down, with some excess room energy at 250 Hz and typical room modes down lower. The -3 dB point measured was about 32 Hz. Wow, this is a small two way with a 32 Hz to 20 kHz full range response. The SPK4 demo speaker has a similar midrange voicing as the KEF LS50 in frequency response, but the LS50 rolls off quickly after 100 Hz. Here is a quick comparo of frequency response measured in the same location and 30cm away. I have offset the measurement pairs so it is easier to compare. Purifi SPK4 Demo Kit on top, KEF LS50 on bottom: As you can see, the response on the LS50 drops quickly after 100 Hz and is -10 dB down at 40 Hz. So this confirms for me what I heard during subjective listening as the Purifi PTT6.5 in the demo kit can put out significant output to 32 Hz, again with the lower mids and midrange sounding crystal clear. Let’s look at the demo speakers step (timing) response. What we are looking for is the “right triangle” shape which denotes an ideal speaker’s minimum phase response: The doublet spike in front is the AMT tweeter which the passive crossover blends perfectly into the Purifi PTT6.5 woofer and has near perfect right triangle step response. Look how smooth the right triangle is with hardly any “bumps” at all which translates into how smooth the woofers frequency response is. I did not take any distortion measurements as I am not setup to perform those. No anechoic or semi-anechoic chamber, unknown distortion contributed by the measurement mic and mic preamp. Plus it’s (really!) hard to do correctly ☺ I would rely on HiFiCompass’s excellent IMD measurements to be representative of the PTT6.5 unit. Here is the frequency response as measured at the listening position: Of course, there is more room in the picture as we know below Schroeder the room is in control of the low frequency response. I have dips at 80Hz and 90Hz and peaks in the low end – classic room modes. Nothing some DSP can’t fix, but my point here is again to show the wide bandwidth coverage of this small two way system with in-room response down to 32 Hz whether near field or far field in my room. Impressive! If you drew a straight horizontal line in-between the peaks and dips and average them across the frequency band, it would be exceptionally flat response with the normal high frequency roll-off. For fun, I hooked up my dual Rythmik F18” subs with a 90 Hz crossover point as you can see in the above chart where I have some major room issues and dialed in some DSP and this is what I got at the listening position: One of the reasons I did this is because I am used to a particular sonic signature that I could only get with subs and large JBL 15” woofers. So I was curious if I could replicate that with the PTT6.5 and maybe lose “the fridges.” I still can’t believe how clean it sounds. Cleaner than my JBL’s… Hmmmm. Do you remember the THX intro? Sony’s intro to Spider-Man into the Spider-verse is the new THX intro. While I linked to the YouTube recordings, hearing it on Blu-ray is mind blowing. With a -3 dB point of 6 Hz in my room with the dual Rythmik F18 subs dialed in, it’s mind blowing. As the intro builds with the volume turned way up, both my daughter wife tried to hide behind the couch because it sounded like the room was going to implode at the climax. The SPK4 handled it with aplomb. Love it!!! Conclusion I must say, I have heard a lot of amp/speaker combos over 50 years in audio, 10 of which being a pro recording/mixing engineer, and have never heard anything like this. Or should I say the lack of distortion and outstanding low frequency extension from a 6.5” woofer. The clarity is stunning. Congrats, truly in a class upon itself. Is the PTT6.5 a subwoofer? A woofer? A midrange driver? Yes, it is all three with a measured nearfield and far field response from 32 Hz to 2.5 kHz in the SPK4 demo package. This really got me to thinking of applications for the driver. Literally makes for a perfect driver for a small format, full range 2 way accurate sound reproduction system. This made me wonder about Purifi’s business strategy. I asked Lar’s about Purifi’s technology roadmap, “Our plan is to become an OEM supplier but also serving the DIY’ers. For larger volumes, we also license our tech like we have done with NAD. The roadmap also calls for DSP and algorithms as well as PSU’s. Our overarching strategy is to go in and overhaul the weakest links in the audio chain and break into new performance territory. Speakers and amplifiers were the natural first points of attack. Exciting to see where all this leads us to.” Makes perfect sense to me and I wish Purifi all the best. They are certainly off to an auspicious start! Purifi web shop. 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.
  11. This is a fun test if you have not tried it already: https://www.audiocheck.net/audiotests_ledr.php
  12. @yyz I have been aware of BACCH DSP for a while. No, I have not tried it, but sure would love to!
  13. Hi @CDJ123 welcome to Audiophile Style! Good question. The Focal's measure pretty good based on Soundstage anechoic measurements. As Floyd Toole says, "Frequency response is the single most important aspect of the performance of any audio device. If it is wrong, nothing else matters." He also says "bass response accounts for 30% of our preference." I would agree with his statements and mirrors my own experiences. I have had the opportunity to review several loudspeakers on this site in my room and "eq" them to be similar. Here is an example of the Kii THREE's and D&D 8c's with their frequency responses overlaid: https://audiophilestyle.com/forums/topic/54065-article-dutch-dutch-8c-loudspeaker-review/page/5/?tab=comments#comment-976157 As Martijn Mensink, the designer of the D&D 8c's says, "With just some subtle EQ the two could be made to sound very similar on most program material - to the extent that I might not be able to distinguish them in a proper blind test." I would also agree, and to my ears, it is difficult to tell the two apart. I have had that experience with a number of other speakers, including comparing large floor standers to small bookshelfs, using the same subs. The loudspeakers directivity index or polar response would be next in line as one of the more important attributes of a loudspeaker besides frequency response. I wish more manufacturers followed the ANSI/CTA 2034 A Standard Method of Measurement for In-Home Loudspeakers that one can download for free or see attached. It gives a good explanation as to why smooth off axis frequency response is important and too long to put in a comment here. The standard report also includes a "predicted in-room response" (see Figure 11) so folks can get an idea of what this may sound like in a typical living room. Of course, it can't account for frequency response below the room's transition frequency, which is why we use DSP in the first place as the room is in control below Schroeder and everyone will suffer from irregular bass response. And given that bass accounts for 30% of our preference, once you have heard optimized bass response from your system, it is hard to go back. While I love the voicing of my KEL LS50's there is not much bass output below 100 Hz, so they sound much better with subs (or even a woofer 🙂 So a long winded answer to say, yes with DSP there is diminishing returns if you already have a full range loudspeaker or sats and sub(s). Whatever one can do to get the full bandwidth with smooth on and off axis response is paramount. Then use DSP to optimise the low frequency response and tailor the HF response, if required, to fully realise the value of your audio investment. ANSI-CTA-2034-A.pdf
  14. Hello. There are 4 common industry standard target frequency responses used to calibrate monitors in sound production control rooms. B&K, Toole and Olive, ITU and EBU 3276. And overlaid on one chart: Given that each target has a +- 3 dB tolerance, effectively each target overlaps one another, all with a downward frequency response at the listening position. This is because loudspeakers are omnidirectional at low frequencies with narrowing directivity at higher frequencies. The rising bass energy yields a steady-state room curve with a downward tilt. This is important to note because ones preference for one target or the other is based on a number of factors, all coming into play at once. Size of listening room, directivity index or polar response of the loudspeakers, distance from speakers to listener (there is a spec with a range), how much direct versus reflected sound is being heard at the listening position based on how lively or dead the listening environment is, also with spec and range of operation. All of these factors play into which target one prefers, with the common theme of how much or little high frequency response is required based on these factors. For example, in my room with narrow directivity loudspeakers and a fairly large and lively room (600 ms broadband decay time) with a 9ft equilateral triangle, I prefer the Toole Olive target response. Sounds neutral to my ears given this combination of loudspeaker/room. On the other hand, Chris's loudspeakers are wider directivity, also larger room. but with a 200ms broadband decay time. In order to hear the same perceived neutral response, more direct high frequency energy is required to arrive at Chris's listening position as compared to my loudspeakers in my room. Normally, I would deliver all 4 target responses at once for your loudspeakers in your room. As Chris has shown in Roon, one can easily flip through different filters as music is playing and choose what sounds best to your ears. Toole and Olive have shown in participant listening studies that as Floyd Toole describes, accurate and preferred are synonymous. Due to schedules, I delivered Chris one filter set at a time, instead of all 4. And started with the target with the most rolled off top end 🙂 LOL! Exactly what he did not need. The 4th target delivered, weeks later, should have been the first. I would hazard a guess that is the frustration.
  15. Hello @johniboy24 The before and after graphs are indeed at the same SPL. I have manually offset the "after" graph by reducing it's gain in REW so it is easier to compare when viewed in REW's overlays chart. We calibrate sound systems at "reference" level, which is approximately 83 dB SPL at the LP. This is because our non-linear ears, relatively speaking, have the flattest frequency response in this SPL range and usually this is the monitoring level set for adjusting the final tonal balance for mixes and masters from the studio. A good reference is Bob Katz, mastering engineer's topic on Level Practices. So for "critical listening" one wants to adjust the SPL to around 77 dB SPL (for highly compressed material) to 83 dB SPL (for wide dynamic range) on a sound pressure level meter at the LP if you want the most accurate playback as far as tonal balance is concerned. If using JRiver, I calibrate the loudness control in this range so when I have music on at "background" level, the loudness control is engaged to boost the bottom end to make up for the ears non-linear frequency response which becomes less sensitive to bass at lower levels than reference. The loudness control restores this balance to make the music sound full at lower listening levels. Hope that helps.
  16. @yyz Agree with @firedog the UMIK-1 USB is great value being able to plug and play and not have to purchase a separate mic preamp and/or ADC. The accuracy of the mic is just fine for taking acoustic measurements. One potential issue is clock rate offset and/or clock drift between the input (i.e. the USB mic with it's own clock) and the output (i.e. DAC). However, John Mulcahy has this fixed in the latest versions of REW. Bernt also has clock drift compensation in Audiolense 6.x and Uli has a special version of Acourate LogSweepRecorder that can be downloaded here for taking measurements with UMIK-1. In the case of Acourate, which uses ASIO, one will need to download Asio4All as well.
  17. Hi @Matias, not directly: https://www.hometheatershack.com/threads/linear-vs-minimum-phase-filters-in-rew-for-minidsp.151513/ Have a look at @SwissBear article on using rePhase and REW together: Also have a look at: https://yabb.jriver.com/interact/index.php/topic,87538.0.html Kind regards, Mitch
  18. HI @Jud Yes, for example Acourate and Audiolense can generate linear phase DSP filters that maintain linear phase throughout. Cheers, Mitch
  19. Mark, not a dumb question. DSP can't absorb or diffuse the sound in a room. So if your room sounds like a bare room echo chamber, DSP can't attenuate the echo or long sound decay at higher frequencies. You need absorption and sometimes a combo of absorption and diffusion. DSP can manipulate the frequency response including the room plus loudspeakers at lower frequencies and just the loudspeaker's direct sound at higher frequencies. DSP can be used for digital crossovers, time alignment of drivers, excess phase correction and the list goes on. DSP can also reduce low frequency room resonances. For living rooms that are fully furnished, drapes, carpet, book cases, etc., it is likely that the rooms decay time falls within the spec as there is a range of operation. So in those cases, acoustic treatments are not likley required. Hope that helps.
  20. Chris, great write up and thanks for the shout out! You have done an excellent job of optimising your audio investment. I am glad you went with 2/3 of the room treatments. Your rooms decay time is right in line with industry standards and any more absorption would likely start absorbing the life out of the music.The Alexia's are indeed full range loudspeakers which allows the DSP to maximise their potential to 20 Hz to 20 kHz frequency response ±3 dB tolerance along the target curve at the listening position. It doesn't get any better than that! I hope you are enjoying the music! Mitch
  21. Here is one, maybe too expensive? https://avahifi.com/products/abx-switch-comparator Maybe you just want a switch box? Parts Express may have a simpler one...
  22. @jaaptina sounds good! Do you have a screen shot to share?
  23. Hello, not to take a away from Chris's nice review of the Lumin X1, but not sure what the issue is here. Chris's response is not flat at the listening position. It follows the EBU 3276 standard of flat to 2 kHz and then slopes down at a rate of 1 dB per octave in the high frequencies. We initially tried the Harman target of 20 Hz to about -10 dB at 20 kHz which was a bit too dull sounding given that Chris's space is large, well damped, and the speakers have wide directivity. This included trying a partial correction to 500 Hz and letting the speakers handle above that. As a side note I have written about the Harman curve for both speakers and headphones in a number of articles on this site. We also tried the ITU, B&K and Bob Katz target, all of which is covered off in the range of operational room response curves. This is part of the process of trying various industry standard room response curves and determining which one is the most preferred given ones speakers and room. As you can see in the testimonials, there are a variety of different high frequency roll offs to accommodate size of room, how damp versus live, how far away from the speakers, etc., all play into what is subjectively heard. This is the balancing act between direct and reflected sound in ones room. More lively rooms tend to favour the Harman target (like mine, which I use), whereas well damped rooms in larger spaces trend towards the EBU target with increased direct sound as there are fewer reflections. both of which arrive at the same neutral tonal response at the listening position. This is why there are a variety of target response, Put the target curves together on overlay like I have done on my site, shows all responses roll off in the high frequencies to varying degrees, but all in tight grouping. A/B switching between all 4 target curves is fun and educational as they sound more alike than different. It boils down to a matter of personal preference given ones room and speakers. To be clear, we are not eq'ing the steady state response to be flat at the listening position. None of the targets are flat and we using frequency dependent windowing to differentiate between room sound included below 500 Hz and direct sound above 500 Hz. See DSP Technical Application Note on my site under DSP tab for an explanation of the approach. Kind regards, Mitch
  24. Hi @PorkChop Yes, this will work on a 2.1 system and yes to taming the bass portion of the total signal.
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