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    Mitch Provides A Unique Perspective Of The Vancouver Audio Show

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    Cones, Domes, and MQA

     

    It has been many years since I have been to an audio show, so I was pretty excited to be invited by Archimago to attend the Vancouver Audio Show. I must say I had a great time! I was very fortunate to be able to sit in the sweet spot for most of the demos, including the MQA demo with the Tidal Sunray G2 loudspeakers and Burmester 909 Mk 5 amp above.

     

    Rather than detailing equipment specifications and prices, I take the approach of how each exhibit sounded to my ears. As a reference, I compare to a sound reproduction system that has been calibrated for accuracy. My definition of accuracy means the frequency and timing response of the music arriving at my ears matches as closely as possible to the content on the recording. I wrote a book on the subject.[PRBREAK][/PRBREAK]

     

     

     

    Listening Guidelines

     

    Speakers and rooms typically have the greatest influence on the tonal response for any given sound reproduction system. Therefore, my review is from this perspective. What do I listen for? If I were to categorize from bass, mids to high frequencies, I listen for smooth bass response (+- 3dB tolerance) and is it balanced with the rest of the frequency band? Does the bass transient response sound tight with no overhang (i.e. narrow impulse response)? Or is it blurry sounding (i.e. non-linear distortion)? Integrating subwoofer(s) without sounding boomy (i.e. peaky room modes) takes considerable skill and effort. I feel this is the primary reason why I did not see any subs on exhibit.

     

    Listening to midrange frequencies, in addition to being balanced with the rest of the frequency range, (i.e. tone) does it sound smooth or nasally sounding (i.e. peaky frequency response)? Does the midrange sound distorted or harsh at program reference level (i.e. non-linear distortion)?

     

    The show was dominated by dome tweeters. To me, the sibilance sound that our voices make when singing an s word is the hardest to reproduce accurately, assuming one prefers accuracy. It can range from real s sounding to overly sibilant SSSsss sound, to slightly rolled off ssshhh sound, to a ssszzz zingy top end at reference program level (i.e. 83 dB SPL C weighting, slow position on a Sound Pressure Level meter measured at the listening position).

     

    Reproducing “s” sounds were further complicated by the number of turntables at the show. I have not seen that many turntables since audio shows in the 70s and 80s. Cartridge and the mastering/pressing of the vinyl vary with respect to how sibilant the sound reproduction is, which may mask what the speaker’s tweeters are capable of. Notwithstanding if the cartage vertical tracking angle was set up right in the first place. Kudos to the all of the exhibitors for carting and setting up the gear – having done it myself, it is a lot of work and hard to get right, especially being room dependent. Which brings me to…

     

    It’s a crying shame man… that the room acoustics of hotel rooms are difficult as they are small, mostly square-ish rooms that typically sound boxy and/or boomy, no matter where the speakers are placed. Naturally, the larger rooms, or rooms with a favorable room ratio, tended to sound better than the boxes.

    I would love to have heard these systems with the rooms neutralized to hear more of the system’s sonic characteristics. I am not talking about anechoic chambers either. Physical room ratios play a large role on how boomy and/or boxy a room will sound. Further complicated by every room at the show had different room ratios, much like our own listening environments.

     

    Want to gain a better understanding of why we hear what we hear in small room acoustics? I recommend James (JJ) Johnston’s presentation on Acoustic and Psychoacoustic Issues in Room Correction, including the Power Point presentation to slide 31.

     

    What to do for future audio shows? One suggestion is for the Vendors to agree on a target frequency response (i.e. tone) and have every system tuned to that response in all demo rooms. That way, I (we) would have a chance to actually hear more of the characteristics of the sound reproduction system that is not being influenced or masked by the room acoustics, or lack thereof. The thing is, the research has shown over 40 some years of objective measurements and subjective listening tests, that the target frequency responses are not only well known, but are also well correlated:

     

    Here is an example of four target frequency response curves that result in the most neutral or balanced sound to one's ears at the listening position:

     

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    The point is that all four target frequency responses are close together gathered from 40 years of research and listening tests. One can read the details for free, including links to the research, by clicking on Look Inside and clicking on Recommended Target Responses in the ToC.

     

    Room acoustics are frequency dependent based on room ratio, construction, and absorption. Given that top-end DSP loudspeaker and room tuning systems use 64 bit calculations, for all practical purposes, are completely transparent, so one would be listening more to the gear than anything else. I know right, a giant leap for many, but once one hears an accurately tuned system, both in the frequency and time domains, it is hard to go back to boomy, boxy, and/or nasally with poor imaging. Bottom line, it would simply be nice to hear more of these systems capabilities with less interference from the hotel room acoustic environment.

     

    What about the timing responses of these speaker systems? From Stereophile, few speakers are time coherent. If you have not heard and lived with a time coherent speaker system before, how can one compare? To me, this is an area where speaker designers should optionally offer time coherent crossovers for their speaker lines for folks that want a more accurate representation of the audio content. There were a few time coherent speakers at the show. Time coherence takes design skill and is expensive to implement with an increase of passive XO parts or active XO with electronics and/or DSP software.

     

    The timing response of loudspeakers also has a tie in with MQA, but I will explain later.

     

     

    Listening Impressions

     

     

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    The ArtVibes Audio are interesting looking speakers that can be ordered with original artwork from select artists. From a sonic perspective, they sounded a bit boxy and somewhat rolled off. Most likely the room… I would love to drop a measurement mic and take some measurements at the listening position to see what I was actually listening to. I think folks would be surprised to see the variance in frequency response. The frequency response is unlikely to be smooth in the bass and typically has a boxy or nasal characteristic which is representative of the rooms influence on the frequency response of the system at the listening position. Nonetheless, they did sound pretty smooth. These are not time coherent speakers.

     

     

     

     

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    Totem’s Element loudspeaker sounded very smooth with good imaging. Not time coherent. Sounded to my ears on the warm side with a bit rolled off top end. I am wondering if I am hearing the natural roll off of the woofer as there is no bass XO on the woofer. Unlikely, but did sound on the warm side, I am not complaining. Very interesting design and implementation.

     

     

     

     

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    Audio Note loudspeakers in a less than ideal room = boom city. Really too bad. If you look closely, there is a Black Sabbath album under the amplifier. Should have played that to take advantage of the boom. The room was so boomy, I could not really hear the balance on the tweeter.

     

     

     

     

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    Wilson Audio Sabrina sounded quite smooth and balanced to my ears. Some room boxiness to the sound, but they imaged incredibly well. I attribute the excellent imaging to Wilson’s claim that the speakers are time coherent. Looking at Stereophile’s measurement of the step response, Figure 6, indeed shows time alignment. I am also impressed to see in Sabrina’s service manual a large section on room acoustics and speaker placement. I have used the Wilson Audio Setup Procedure (WASP) before in lieu of measurement gear with good results. One can never underestimate the value in properly setting up one’s speakers to get the best sound quality for any given room.

     

     

     

     

     

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    Devialet Silver Phantom sound very impressive. I would love to review these in my home environment. Big sound from a small speaker, with excellent imaging. Manufacturer claims they are time coherent, but I could not find anywhere on the net any actual frequency or time response measurements for this DSP speaker system. It would be interesting to see measurements of this speaker, especially their step response.

     

     

     

     

     

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    Kef Blade 2’s hooked up to Naim’s Statement amplifiers. The Statement amplifiers remind me of early Cray computers. The Blade 2’s sounded incredibly smooth to my ears, with very good imaging. Kef makes the claim that these speakers are “single apparent source”, but Stereophile’s step response measurements Figure 9, show that the speakers are technically not time coherent. The tweeter leads first, then the midrange, then the woofer. Compare the step response to the Wilson Sabrina’s above to see what I mean. Aside from that, the speakers measure incredibly smooth and that is how they sounded to my ears. They especially sounded good on the s’s sibilant sound. I remember they image quite well, but something about the depth of field did not sound quite right to me. After looking up the step response (timing) measurement linked above, I can now understand why the depth of field sounded slightly different to my reference. There is a step response measurement below of the reference time alignment that I am referring to in which we will get to a bit later.

     

     

     

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    The Davis Acoustics Renoir sounded really good, even in the smallish room they were in. Smooth and extended in both frequency extremes. These are not time coherent speakers.

     

     

     

     

     

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    A blast from the past, the infamous Speakerlab Super Sevens. When I was in high school, a long time ago, I built a version of these for a friend and they sounded fantastic to rock out on. Even though they are sitting on the floor in this demo, they have a tight acoustic suspension low end response, coupled with what arguably could be the smoothest top end of the show. S’s sounded real, yet not strident sounding like some of the dome tweeters when pushed hard, at least in my experience. Those planar magnetic midrange and tweeter really sounded super smooth and fast in reproducing transients. Best value buy at the show, even with the speakers on the floor. Must have forgot stands, look at that pile of Boulder electronics.

     

     

     

     

     

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    Magico S5 Mk II sounded very flat to my ears, meaning a ruler flat frequency response past audibility. Very revealing highs with extended low frequency response with some room coloration. Not time coherent from any material I could find on the speaker. Would love to see a step response of these ones.

     

     

     

     

     

     

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    Dynaudio Focus xD speakers. Another technically advanced active DSP loudspeakers. Very clean sounding at volume, a trait I note in all bi- tri-amp powered systems, including my own. This is another loudspeaker I would love to measure up and have a look at the step response.

     

     

     

     

     

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    I could not help sneak in a picture of VKMusic’s KT150 push-pull amplifier with micro-controller bias adjust. A combination of old school tubes with modern day micro-controller. Very cool.

     

     

     

    MQA Impressions

     

     

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    Before we get into it, I want to discuss again the timing response of loudspeakers as to how it pertains to MQA. As mentioned in Stereophile, very few loudspeakers are time coherent or time aligned. It is worth reading the entire article to better understand why a step response is used to measure time coherency as opposed to viewing an impulse response.

     

    What does an ideal time coherent loudspeaker step response look like? Pretty easy to model using a digital filter that is flat from 20 Hz to 20 kHz, with the bass rolling off at 15 Hz at some dB per octave as loudspeakers don’t reproduce 0 Hz or DC very well. Here is the step response of the model specifications:

     

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    The vertical “step” represents all frequencies playing at the same time and the downward slope is the corner frequency rolloff of the filter.

     

     

     

     

     

    From the Stereophile article above, here is what a good measured step response of a time coherent speaker looks like:

     

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    Note the vertical step is the tell-tale sign of time coherence, and pretty much matches the shape of the ideal step response above, except that this is a measured response of speaker and room. Below is a step response, from the same article, but representative of a non-time coherent speaker:

     

     

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    Here we see the tweeter arriving first with a positive going step, just after 4 milliseconds, then we see the midrange arriving next, with a negative step, and then finally the woofer arriving with a positive step. This, and variants, are typical step responses of non-time coherent, multiway loudspeakers. Have a look on Stereophile if you can find your speakers measured step response.

     

     

     

    Below is a measured step response of my 3-way, high efficiency speakers. These use a simple 3-way passive crossover, with high quality parts:

     

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    This is a zoomed in view on the time scale. Tweeter arrives first, negative step, then midrange, also negative step, then woofer, positive step. Even with frequency correction for a flat response, the timing response is still representative of the chart above. Meaning these speakers are not time coherent and therefore distort the timing of the music arriving at my ears.

     

     

     

    However, by disconnecting the passive XO and using digital XO and time aligning the drivers, I am able to turn my speakers into time coherent speakers that do not distort the timing response that arrives at my ears:

     

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    I have also overlaid the ideal step response from the beginning of this section to show how close to ideal I was able to transform a typical 3-way speaker system into a time coherent system that can accurately reproduce the timing response that is on the recording. It does make a difference to my ears, especially the transient impact and imaging. Especially the depth of field imaging that make the speakers “disappear.”

     

    What the heck does all of this have to do with MQA? If part of MQA’a claim is to deblur or

    , then what use is it if one’s loudspeakers smear the timing response as demonstrated by the measured step responses above? The fact is that the mass majority of loudspeakers on the market are not time coherent and therefore are smearing the timing arriving at ones ears at the listening position as the loudspeaker is the final output device in the playback chain. The reality is no amount of MQA deblurring is going to fix a non-time coherent loudspeaker. The signal arriving at ones ears is still going to be time distorted.

     

     

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    Photo courtesy of Element Acoustics

     

    With respect to the MQA demo with the Tidal Sunray G2 speakers, Burmester 909 Mk 5 amp, Burmester 111 MusicCenter/preamp and MQA decoding from the Meridian 808 V6 Signature CD/DAC, sounded excellent to my ears.

     

    Disappointingly, there was no comparison between a regular recording and an MQA encoded version of the same recording. Therefore there is no way to detect, determine, or decide MQA’s contribution to the sound quality other than one is listening to a $300K system with excellent recorded, mixed, and mastered source material.

     

    If one’s speakers are not time coherent, and distort the timing response similar to the measured step responses above, then what sonic value is MQA’s deblurring filter? This precludes that one is striving for accurate playback of what’s on the recording. I certainly am interested in playback accuracy, both frequency and timing response to my ears at the listening position. If that is your preference, then either investing in a pair of time coherent speakers or applying frequency and timing correction to an existing pair of speakers by using DSP are the only two ways today to get playback timing accuracy to one’s ears.

     

     

     

    Conclusion

     

    I had a great time at the show. There were only one or two systems that succumbed to hotel room acoustics (i.e. the room was simply too small). Most systems sounded very good, even though I could still hear either boom or boxiness or both depending on the hotel room and speaker setup. Many exhibits sounded excellent despite the acoustics.

     

    What I find fascinating is that the majority of these systems were in the tens of thousands of dollars and with quite a few in the hundreds of thousands. If I were to setup a system worth that amount of money, I would want to neutralize the effects of the room and ensure the interchannel frequency response is as identical between the speakers as one can get across a broad seating area so that the listeners were getting the best representation of the speakers and equipment as possible. While it is ideal to audition audio gear in one’s home, it is often very difficult to make those arrangements. Sometimes the gear one is interested in can only be heard at an audio show.

     

    While loudspeaker and room DSP software is available, not too many use it at these audio shows. In the pro audio market for touring bands that take their speaker rigs from venue to venue, all use some level of speaker and room correction both for frequency and timing response tuning. For sure, other than the push button, auto-tuning correction software, one does need to understand what is going on in order to correct both frequency and timing response effectively across a listening area. I wrote a couple of CA articles on basic DSP and advanced DSP if you want to get a flavor of how it is achieved.

     

    In addition to the skills required to neutralize the effects of a room, there may be fear that if all of the systems were smoothed the same way using the same target fr curves, then the unskilled listener may not be able to tell the difference between systems. However, the referenced target curves are a great place to start, many will fine adjust to one’s own preference, which may bring out the voicing of the speakers even more. That’s the beauty of designing your own custom frequency response and timing correction filter to match one’s own speakers to one’s unique acoustic listening environment.

     

    My preference is for accurate sound reproduction so that the music arriving at my ears is as identical as possible to the music that is on the recording, regardless of format. In my case, I have used loudspeaker and room DSP software, as the number of time-coherent speakers are still far and few between. However, I am excited by the audio show to see the number of speakers that do use DSP, I wish there was more of them correcting the speakers timing response for accuracy.

     

    Enjoy the music!

     

    Thanks to Archimago for letting me use your pics from the show.

     

     

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    About the author

     

     

    Mitch-200.jpgMitch “Mitchco” Barnett

    
I love music and audio. I grew up with music around me and worked ten years as a professional recording/mixing engineer. Recently, I wrote an eBook on Accurate Sound Reproduction Using DSP.

     

     

     

     

     

     

     

     

     

     

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    Brilliant...and this is why it's getting difficult to find a successor for my quad esl.

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    'Speakers and rooms typically have the greatest influence on the tonal response for any given sound reproduction system.'

    This is the most fundamental truth as far as audio systems are concerned. If one doesn't understand it IMHO he either doesn't understand anything about audio or can't hear a ..damn thing..

    A very good article written by a person who both understands and can hear a lot.

    Very appreciated!

    Got no time now but I think I'll be back with a longer comment soon.

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    I attended the show and so very happy to read your report...your experience of the MQA demonstration mirrored mine exactly. The presentation was lacklustre and did nothing to enlighten us as to the merits of MQA and seemed consistent with other reports of similar MQA presentations. I had no preconceptions and was anxious to hear all and everything but if that presentor is indicative of their attempts to enthuse us they could be in deep trouble.

    As you describe; no comparisons, nothing.

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    Hi Mitcho, thanks for this extensive review.

     

    I have one comment with regard to the Time Coherence aspect of Loudspeakers and MQA: It is true that this aspect is of large importance for accurate music reproduction and indeed many loudspeaker do suffer from bade time-incoherent design... DSP is capable to repair a lot of those errors, but with MQA there is something unique involved and that is the capability to repair for both PRE-RINGING and post ringing effects of A?D and D/A converters. As you will agree, no loudspeaker is capable to produce PRE-ringing errors, so this part of time -incoherence is not present in the analog part of the reproduction of the sine wave. But in the digital processing of A/D an dD/A signals, this effect is present and audible. Especially since it is an unnatural effect, it causes fatigue. The MQA DSP is capable to recognize the way the original recording was processed, like Photoshop software is able to correct for lens profiles, chromatic- and geometric errors. The PRE-ringing of past A/D errors can only be corrected in the digital domain when this information is available or recognised by the MQA DSP. So there is a difference which, for the moment, only MQA is able to compensate for.

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    With regard to the fact that MQA demonstrations are unable to demonstrate A/B comparison with original WAV or FLAC files, there is a logical explanation: Any MQA accredited DAC has been measured on a test bench what its intrinsic D/A time smearing effect is and it is being compensated for by the MQA DSP. I suppose (but never received prove or answers yet from anyone..) that the performance of a MQA certified DAC is intrinsically improved with regard to its D/A pre-and post-ringing effects.. this should result in an improved sound quality also when playing non-MQA encoded files. This phenomenon is what I have encountered myself with my NAD C390DD after upgrading it to V 2.89 MQA firmware. The DDFA DAC/Amp sounds even more analog, relaxed than when I prurchased it 3 years ago. When playing MQA authenticated files, the SQ increases a step further. So an objective comparison between MQA and non-MQA can only be done by using 2 the same types of DAC, one which is MQA accredited and one which is 'standard'

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    Sphinxsix, I fully agree with you. Speakers and room acoustics are so tied together...

    I remember a dutch article referring to Peter Walkers " To you speaks the Room '' ... So true.

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    Always an education reading your blog entries, thank you Mitch!

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    So, LINN Product is right all the way

    and Pitch accuracy is related to timing

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    Mitch do you know if Floyd Toole has written anything about time domain speaker response in his books?

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    Mitch,

    Great show report!

     

    I agree that the step response is a good metric. And with passive loudspeakers the step response is used to characterize those minimum phase crossovers to demonstrate crossover integration more so than absolute time coherence.

     

    As you can see from a recent review of the Zu Audio speakers in stereophile, the Zu speakers exhibit a very vertical step impulse. But when one looks more closely at the lateral off-axis, it's clear that the Zu isn't a world beater. I've heard these speakers at shows and they aren't very impressive.

    Zu Audio Soul Supreme loudspeaker Measurements | Stereophile.com

     

    So I think using the step is helpful with DSP software like Acourate and much less helpful to fully characterize passive crossover loudspeaker systems.

     

    Hvbias,

    Floyd Toole would say that lateral off axis smoothness relates much better to stereo imaging and overall musical enjoyment than absolute time cohererence.

    http://seanolive.blogspot.com/2008/12/part-3-relationship-between-loudspeaker.html?m=1

     

    Michael.

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    MikeJazz, sphinxsix, thanks for your comments. wdw, we will have to meet up at the next show!

     

    Hi PeterV, thanks for your comments. Please note that when one is using DSP to correct the timing of loudspeakers, it is also correcting for any (pre)ringing in the DAC and anything else in the measurement/playback chain, and aligning it to a known standard, like the ideal step response in the article. One can also include the digital audio playback software, like JRiver in the measurement chain if desired. The DSP software, in this case, Acourate is working just like in your Photoshop example. Note that Acourate analyzes the full frequency range of the transient behavior and it is this result that is used as the basis for further calculations for frequency and timing corrections.

     

    As a side note, DSP digital filters in loudspeaker correction can cause preringing using a linear phase FIR filter or post ringing in minimum phase FIR or IIR filters. In my eBook, I exaggerate the effects of preringing in the digital filters to orders of magnitude larger than what is measured in a typical D/A converter. With the transient nature of music, I find it very difficult to hear even the exaggerated preringing. You may note in the measured step (timing) responses above, there is no (pre)ringing at all in the step response as there is a preringing compensation applied in the digital correction filter, to not only correct the timing response of the speaker, but also the DAC. So it is not quite true that only MQA can fix a D/A pre and/or post ringing effects.

     

    I would love to objectively compare the digital and analog outputs with/without MQA. My feeling it is likely to come to this:

    Archimago's Musings: MUSINGS: Digital Interpolation Filters and Ringing (plus other Nyquist discussions and "proof" of High-Resolution Audio audibility)

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    Hi Michael and hvbias, step response is one measurement attribute of several used for achieving accurate sound reproduction, if accuracy is one's preference. In my eBook, in addition to frequency and step response, I cover off; group delay, energy time curve, reverb time, polar response and interaural coherence coefficient (i.e., imaging).

     

    Smooth off-axis frequency response, which is polar response in my eBook, is just as important as time coherence, in my opinion. I show in my eBook the smoothness of the response of my loudspeakers across a 6ft x 2ft listening area, which is largely contributed to the constant directivity waveguides I use from 500 Hz up. Michael, I did not see in the article linked that "Floyd Toole would say that lateral off axis smoothness relates much better to stereo imaging and overall musical enjoyment than absolute time coherence" From my read of the artilce, smooth on and off axis frequency response is what trained listeners would prefer, which I am in agreement with, and I presume you are as well, based on the loudspeakers you are listening to :-)

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    Floyd Toole said,"In the design of loudspeaker systems, knowing the phase behavior of transducers is critical to the successful merging of acoustical outputs from multiple drivers in the crossover regions. Beyond that, it appears to be unimportant." Sound Reproduction 2nd ed. p.420.

     

    The translation is that step response is a helpful metric to show how well a passive crossover behaves. I realize Mitch is also referring to absolute time coherence. In the context of loudspeaker design, phase coherence is a big deal due to its direct relationship with the frequency domain. All of the NRC/Harman studies can statistically tie listener preference to smooth frequency response off axis.

     

    I've previously searched the AES library for any study which show the same listener preference for time domain and haven't found anything concrete. Of course, time and frequency are related to each other so step response is still very helpful. But it's not the holy grail. If it were, then Quads would be the perfect loudspeaker. Of course, they aren't, even tho I love how they sound. :-)

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    Yup, agree with Floyd on that one, but that's not the issue I am trying to raise awareness about. I am talking about the acoustic signal arriving at one's ears matches as closely as possible to the waveforms stored in a digital media file. And in the case of this article, specifically, the time domain.

     

    As you have found out, little AES or other research, other than anecdotal evidence, mine included, to suggest that time alignment does make an audible difference. I hope Dr. Toole updates his book to include audibility/listener preference studies around speaker time coherence.

     

    As mentioned before, not many speakers are time aligned as it is technically very difficult to do properly. That's why I believe there is little research on this subject area, especially around audibility. With the advent of powerful DSP software, and new computer aided passive XO designs, like this Danley design, (see how many parts it takes to get a passive XO to be time aligned and many in the industry feel Danley's designs sound the best), I am hopeful that the speaker industry ups it's game around time coherence loudspeakers.

     

    The thing is Michael, unlike many "tweaks", hardware or software, time alignment is easily measured objectively. Therefore, it is simply a matter of time that audibility tests will show whether real time alignment, and not just though the crossover region, is audible or not and what the benefits are. For me, I have spent the last 5 years researching and conducting my own audibility tests and I have my answer.

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    I agree that if there were a way to test listener preference and the listeners could be trained up on soundstage effects I hear with time correction, the evidence would support your experience. I just think that comparing active crossovers and passive ones is really hard to do since there are so many excellent sounding passive speakers with imperfect time performance.

     

    I do wish there were more exhibitors who used DSP in their setups. I try to encourage dealers and distributors to use DSP in the hotel rooms. I'd love to see a multi sub setup at a show with digital crossovers. I think listeners would be shocked at the dynamics; Maybe, for once, an audio show not dominated by boring 3 piece jazz combos or chamber music.

     

    Yup, agree with Floyd on that one, but that's not the issue I am trying to raise awareness about. I am talking about the acoustic signal arriving at one's ears matches as closely as possible to the waveforms stored in a digital media file. And in the case of this article, specifically, the time domain.

     

    As you have found out, little AES or other research, other than anecdotal evidence, mine included, to suggest that time alignment does make an audible difference. I hope Dr. Toole updates his book to include audibility/listener preference studies around speaker time coherence.

     

    As mentioned before, not many speakers are time aligned as it is technically very difficult to do properly. That's why I believe there is little research on this subject area, especially around audibility. With the advent of powerful DSP software, and new computer aided passive XO designs, like this Danley design, (see how many parts it takes to get a passive XO to be time aligned and many in the industry feel Danley's designs sound the best), I am hopeful that the speaker industry ups it's game around time coherence loudspeakers.

     

    The thing is Michael, unlike many "tweaks", hardware or software, time alignment is easily measured objectively. Therefore, it is simply a matter of time that audibility tests will show whether real time alignment, and not just though the crossover region, is audible or not and what the benefits are. For me, I have spent the last 5 years researching and conducting my own audibility tests and I have my answer.

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    Some of the reasoning in the posts above as to why there has been no direct A-B comparisons of MQA to WAV (or FLAC) of the same master at any of the shows so far leads me to believe that they are afraid to do it. Maybe the difference is not as great as some of the wet dream reviews have indicated. If the difference was substantial and repeatable, I would think you would want to flout it.

     

    It may be a moot point for a long time to come if Apple buys Tidal and shuts it down as they have a habit of doing (see MOG/Beats and now Pono). MQA becomes a Knight with no Steed. MQA has always been about streaming something like hi-res with a quasi-DRM infrastructure. MQA downloads will be few and far inbetween as will all downloads.

     

    MQA needs a streaming service (or at least a tier of one) that is dedicated to presenting music in full resolution. That would be expensive and require our community to support it in large numbers. MQA may be a bridge too far but only time will tell.

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    FFS just stand back and listen to yourself "I compare to a sound reproduction system that has been calibrated for accuracy" and "If I were to categorize from bass, mids to high frequencies, I listen for smooth bass response (+- 3dB tolerance)" and "My preference is for accurate sound reproduction so that the music arriving at my ears is as identical as possible to the music that is on the recording, regardless of format." This is writing for writings sake and I'd file it in the category 'the bleeding obvious'. Articles like this remind me of why I'm an infrequent visitor tbh. Back to the music for me I'm afraid.

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    FFS just stand back and listen to yourself "I compare to a sound reproduction system that has been calibrated for accuracy" and "If I were to categorize from bass, mids to high frequencies, I listen for smooth bass response (+- 3dB tolerance)" and "My preference is for accurate sound reproduction so that the music arriving at my ears is as identical as possible to the music that is on the recording, regardless of format." This is writing for writings sake and I'd file it in the category 'the bleeding obvious'. Articles like this remind me of why I'm an infrequent visitor tbh. Back to the music for me I'm afraid.

    Wow. No good deed goes unpunished. can you elaborate on what you don't like about this article?

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    Floyd Toole said,"In the design of loudspeaker systems, knowing the phase behavior of transducers is critical to the successful merging of acoustical outputs from multiple drivers in the crossover regions. Beyond that, it appears to be unimportant." Sound Reproduction 2nd ed. p.420.

     

    Time coherence is distinct from Phase coherence though. You can have a speaker that is phase coherent but not time coherent. A Time Coherent speaker will be both time and phase coherent.

     

     

    "I compare to a sound reproduction system that has been calibrated for accuracy" and "If I were to categorize from bass, mids to high frequencies, I listen for smooth bass response (+- 3dB tolerance)" and "My preference is for accurate sound reproduction so that the music arriving at my ears is as identical as possible to the music that is on the recording, regardless of format." This is writing for writings sake and I'd file it in the category 'the bleeding obvious'. Articles like this remind me of why I'm an infrequent visitor tbh. Back to the music for me I'm afraid.

     

    FWIW ... Mitch was just describing and defining time coherence.

    Many talk about it - just like Meridien - but haven't the faintest idea. And it is true that once you get used to time coherent sound you really can hear "the box" when listening to speakers that are not time coherent.

     

     

    @mitchco: Mitch, great article!

    I also think that the Group Delay of the accompanying gear also add to the problem.

    Would be very interested in your opinion on that aspect.

     

    MQA is a borderline scam. I admire your restraint in the article.

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    Phase is just a relative expression of time at a frequency. Here is a nice conversion tool:

    http://www.sengpielaudio.com/calculator-timedelayphase.htm

     

    If you've read the book I referenced, you would know Toole is talking about both phase and time. There are numerous quotes one could pull from his book saying the same thing. Amir pulls several here:

    Interesting article by Mitchco. | Audio Science Review (ASR) Forum

    You have to remember we are talking about speakers here which can be measured with a microphone. We aren't talking about the usual audiophile jibberish accompanying the latest worthless gadget or new imaginary technology.

     

     

    Time coherence is distinct from Phase coherence though. You can have a speaker that is phase coherent but not time coherent. A Time Coherent speaker will be both time and phase coherent.

     

     

     

     

    FWIW ... Mitch was just describing and defining time coherence.

    Many in audio talk about it just like Meridien but haven't the faintest idea. And it is true that once you get used to time coherent sound you really can hear "the box" when listening to speakers that are not time coherent.

     

     

    @mitchco: Mitch, great article!

    I also think that the Group Delay of the accompanying gear also add to the problem.

    Would be very interested in your opinion on that aspect.

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    It's ironic that Meridian is now presumably interested in time coherence. Their active loudspeakers are anything but time coherent even tho it would have been easy to make them so.

    Meridian DSP8000 digital active loudspeaker Measurements part 2 | Stereophile.com

    I'm not exactly sure what's meant by time coherence, but Meridian did introduce EBA to their DSP range a few years ago, enhanced bass alignment, ie DSP achieved time alignment of delivery of sound to the ear based on speed of travel of the various frequencies. If this is time coherence, then their speakers have been for a number of years?

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    Time coherence is distinct from Phase coherence though. You can have a speaker that is phase coherent but not time coherent. A Time Coherent speaker will be both time and phase coherent.

     

    @mitchco: Mitch, great article!

    I also think that the Group Delay of the accompanying gear also add to the problem.

    Would be very interested in your opinion on that aspect.

     

    MQA is a borderline scam. I admire your restraint in the article.

     

    Nikhil, thanks for the kind words. To expand on your first paragraph, in my case using Acourate DSP, I rotate the signal for 2 out of the three drivers, using one driver for time reference, by the number of samples measured in the z-offset. This lines up the acoustic centers in the vertical plane to form a single point of sound. Using a linear phase crossover, sums perfectly in both the frequency and time domain as illustrated in this article. Thus both time and phase coherent. My preference and I provided a link above to an advanced CA article showing how this is achieved, if folks want to check out the details.

     

    One can use https://sourceforge.net/projects/rephase/ to adjust the amplitude and phase responses of the filter independently for one's loudspeakers to make them phase coherent, but not time aligned. See this article and Example 1: https://www.minidsp.com/applications/advanced-tools/rephase-fir-tool I encourage folks to try it out and see if you can hear a difference.

     

    Nikhil, in the eBook, I dedicate a chapter on Group Delay. D/A converters analog outs, active preamps, amps, may all have some level of high pass filter applied, so as not to pass DC. Depending on the corner frequency, will add group delay in the bottom octave or two. My tests and research shows that my ears are not susceptible to GD below 100 Hz. The research starts at 500 Hz. This is the only article I could find on testing audibility of group delay below 100 Hz: group_delay

     

    Cheers!

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    Hi mitchco, thanks for the inspiring article.

     

    Would you agree or disagree to Benchmark critique of MQA below?

     

    MQA also has an adaptive filter feature that is intended to shorten the rise time of short transients. Benchmark generally avoids these types of filters because we believe they do more damage than good. This is especially true as the sample rate increases.

     

    Any attempts at "time-domain optimization" of the energy envelope will produce aliasing. This aliasing causes timing errors in the onset of transient events. With "time-domain optimization", transients tend to get reproduced in synchronization with the digital samples. The "optimized" digital system no longer has a continuous time response. The optimization removes inaudible ultrasonic pre-ring and creates an artifact that resembles jitter. Benchmark believes that this is a poor trade-off at 44.1 kHz sample rates and a complete mistake for higher sample rates.

    from https://benchmarkmedia.com/blogs/application_notes/163302855-is-mqa-doa

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