Playback Learns About Audyssey DSX: Part 3

Posted by: Chris Martens at 9:09 am, June 29th, 2009

To be perfectly honest, I found the Audyssey DSX demo system sounded better than some surround (and high-end stereo) systems I’ve heard in terms of holistic, holographic imaging, but not by nearly as large a margin as some of my fellow editors seemed to experience. I suspect this may have to do with two factors.

 First, I’m used to hearing some very high-end stereo systems that offer strikingly good resolution, focus, and pinpoint imaging, and that produce extremely wide and deep soundstages. What those stereo systems may give up relative to DSX in terms of producing an all-encompassing “dome of sound” is offset by their almost eerie clarity, imaging precision, and giant soundstages (albeit with no true surround information coming from behind listening position).

Second, I’m very particular about the imaging of my surround sound systems and am used to tweaking them painstakingly until I not only hear a good, coherent front soundstage, but one that also wraps smoothly to the sides of the room. Granted, I sometimes achieve these results by deliberately positioning my front main speakers somewhat more widely angled toward the sides of the listening space than is theoretically correct. (In theory, the front mains should be positioned roughly 30 degrees to the left and right of the centerline of the system, though I’ve been known to position my main speakers at wider angles than that.). But here’s my thought: I’d rather go with a set-up that is a bit wrong in theory yet that sounds right, as opposed to putting up with the opposite situation (i.e., a system that is theoretically correct, but sounds wrong—yuck!).

At the end of the day, I suspect that the Audyssey DSX system may provide a more reliable and foolproof means of achieving the kind of immersive and holographic surround sound environment we all crave.

At the same time, I think you can get many—though perhaps not all—of the core benefits of DSX technology by carefully setting up either 5.1-channel or even 2-channel systems, using high quality components and paying very close attention to speaker placement (not to mention judicious use of acoustic treatments).

 

DSX Caveats and Questions

It perhaps goes without saying that one of the inevitable caveats of setting up a DSX system is complexity. In full-blown configurations, DSX systems require nine (or even 11) speakers, not including subs, which—I suspect—is more than many home owners will want to accommodate (except in full-on, dedicated home theater rooms). Even then, properly positioned height channel speakers may pose a problem in that they may need to be mounted near the ceilings—if not in the ceilings of some rooms. It may be, though, that some accessory-makers will devise tall, attractive stands (perhaps with height-adjustable poles?) for use with height channel speakers, assuming the DSX concept catches on.

An open question is whether or not the DSX system is "sweet spot-centric." I don't know the answer to this question, but it arose in a private talk I had with Tomlinson Holman after hearing the DSX demo in the Audyssey listening room. I had the sense that I had experienced most but perhaps not quite all of the benefits of DSX and I asked Holman about the matter. He asked me, "Were you sitting in one of the center seats?" I replied that I had been seated one chair off from the center position. "Then you should try it from the center," he said. Unfortunately, a glitch in the room's media server prevented us from re-trying the demo, but Holman's comment left me with an open-ended question.

Normally, Audyssey’s MultEQ room/speaker EQ system (which I greatly admire) is all about broadening the sweet spot, so that almost every seat in the room becomes a viable listening position. Wouldn’t it be odd if the DSX system, in sharp contrast to Audyssey’s MultEQ system, made systems more finicky in terms of requiring listeners to sit in the “sweet spot?” Only time (and further listening sessions) will provide answers to this one. 

Comments

jarango@nmia.com -- Thu, 07/02/2009 - 11:49

The original Chesky SACD demo disk has a section of 6.0 music (no center and no LFE), with the extra 2 speakers located in roughly the position recommended by Tomlinson. These tracks clearly produce a more realistic front image. Several of the early Telarc  and DMP SACD's are 6.0, with the LFE channel assigned to a mono height channel. Here, the sense of envelopment is stronger than usual, even though the muscians do not move (as WALL-e does). My experience with the Chesky and Telarc recordings suggests DSX is a good idea.

jarango@nmia.com -- Thu, 07/02/2009 - 11:49

The original Chesky SACD demo disk has a section of 6.0 music (no center and no LFE), with the extra 2 speakers located in roughly the position recommended by Tomlinson. These tracks clearly produce a more realistic front image. Several of the early Telarc  and DMP SACD's are 6.0, with the LFE channel assigned to a mono height channel. Here, the sense of envelopment is stronger than usual, even though the muscians do not move (as WALL-e does). My experience with the Chesky and Telarc recordings suggests DSX is a good idea.

Norman Varney -- Thu, 07/02/2009 - 14:31

As we add more speakers to the system, we add complications. Just from the acoustical side, we add at least 6 more first order reflections with each additional speaker, along with many other boundry effects which will increase spatial and timbre distortions. Though I enjoy multi-channel audio, a two channel system, when set up properly, can offer a very large, holographic soundstage and is much easier to tame. 
 
Sure, add more speakers around and sound comes out of them, but how accurate and reproducable is it?  A good soundstage requires symmetry of acoustics and electronics.  As we add more channels, symmetry becomes less and less likely. Removeing room acoustics from the equation, a good soundstage is obtained by signals converging at a single point in space, at the same time with the same gain.  System calibration is critical. In addition, the system components need to be the same for each channel in order to have the possibility of reproduceing the same.  Adding more channels makes this possiblity much more difficult to achieve.  I wish for a 4.2 system.  With such a system, more people would be able to afford, accomodate, and faithfully reproduce a convicing soundstage.

Norman Varney
A/V RoomService, Ltd.

jarango@nmia.com -- Thu, 07/02/2009 - 14:38

I agree that adding more channels does add spatial and timbre distortions. Fortunately I have a dedicated listening room where I can experiment with multiple channels and diffusion (mostly, LP's and books) and absorption. With a little effort (and not much absorption) nearly all spatial distortions can be tamed, a least at the "sweet spot". I let Audyssey handle timbral problems, which it does very well. The part of your comment that caught my eye was your interest in 4.2 systems. My experience is that it is very difficult--so far for me, impossible--to get truly deep bass (say, below 30 Hz) with more than one subwoofer. Have you set up a system the plays below 30Hz with more than on subwoofer? If so, how did you do it?

Norman Varney -- Fri, 07/03/2009 - 09:10

I'm not sure I understand your question. If you can produce frequencies below 30Hz. with one subwoofer, you can certainly do it with two.  The reason I say .2 is becuase I don't desire a monoral signal from 80Hz. on down.  80Hz. reproduced in a small room is not omni-directional, you can easily perceive where the signal originates, and therefore a single subwoofer draws attention to itself.  It does not integrate with the system as a single voice, rather it sounds like the low frequencies are coming from its location. The illusion is segregated.

Norman Varney
A/V RoomService, Ltd.

vdorta (not verified) -- Thu, 07/02/2009 - 23:05

"My experience is that it is very difficult-so far for me, impossible-to get truly deep bass ..."
Provided your audio system has what it takes, your problem probably has more to do with the room than with the audio system.

jarango@nmia.com -- Fri, 07/03/2009 - 10:33

Since I have three subwoofers (a JL 13" and the two bass units from an Infinity full range that can be separated) and a processor that allows for up to three subwoofers, I've tried one, two and three subwoofers in what I guess is a moderately sized room (19x21x9, roughly). I've used the RPG software to find the best locations and have also tried putting the second subwoofer at the listening position and crawling around to find locations where the signal is reinforced. Invariably, adding a second or a third subwoofer (always equalized to remove room peaks) adds to bass frequencies from about 45 Hz to 100 Hz (that is, lots more bass drum) but subtracts from the signal in the really deep bass. While I agree that, at least on some recordings, deep bass from a single sub can be located, with time it's possible on most recordings to adjust the level so that the deepest bass appears to come from the recorded space even when the sub is located well away from the font speakers.

Norman Varney -- Fri, 07/03/2009 - 11:32

Obtaining somewhat linear bass frequency response shouldn't be too difficult with your equipment. I'm thinking that you might be locating your sub(s) in areas that are problematic pressure peaks. If you locate them in pressure troughs for those frequencies, they will not boost them. Idealy, the sub(s) should be physically time aligned with the mains and placed between them, off the floor, so as to avoid boosting your fundamental axial room modes. After this is done, calibration can be performed.

Norman Varney
A/V RoomService, Ltd.

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