Room correction - what device works best?


Looking at room correction and all the threads I found seem old. What are the current options for excellent 2 channel sound. Comments on DSpeaker, Lyndorf, DEQX, Audessy, Rives and others welcome. I have option for using in digital domain or putting between pre and amps. Would of course prefer great sound at lower price. Also prefer something that does not take a year of obsessive fiddling to get right. Have a very large family room, so room treatment options limited. Current system is Ayon Cd5s (transport, DAC and pre combined), Nuforce Ref 20 mono amps and Von Schweikert VR55 speakers. Is most of the bang for buck in correcting for room modes or is speaker phase issues also necessary? Eventually in may have subs but not now.
Thnaks
gammajo
I think you would be better off not using a correction component. Tune your room instead.
I agree with Zd542 ... if possible. In my case, it was not possible to "correct" my room. As you may already know, I opted for the DEQX PreMATE. It tamed my speakers and room. BUT ... I am not thrilled that it required adding an artifact between my preamp and amp.

As one respected dealer once told me, "sometimes you have to take 2 steps backward to be able to take 5 steps forward."

Ce la vie.
Also be careful not to use too much room correction...
I have found adding reflection absorbing panels and bass traps have made a tremendous improvement. Mostly DIY. A good site for advice is real traps.com.
Just curious why you're considering room correction? Is there a specific room issue you're trying to overcome (let's face it, they all have'em)? Have you heard a system with room correction? I get that you don't want to turn your family room into what looks like an adult daycare center, but I'd still try to do some of the basics like treating first reflections, corners, etc. if at all possible.

I'll just share my experience FWIW. I heard two different corrected systems, one in a hotel room and one in a big buck home system in a well-treated room. In both instances the differences were huge, as in as big or perhaps bigger than a significant speaker upgrade but definitely at that level. Put it this way, after hearing the corrected signal I didn't even want to listen to the un corrected system anymore. I'm with Byfwynne in not wanting to insert anything into my analog signal, but the improvements in these cases were so overwhelming that if it was degrading the signal to any degree it was swamped by all the other benefits.

Anyway, if it's me I'd try the DSpeaker just because it seems to work well and is relatively easy to use -- I'm not into endless fiddling with this stuff either. And it has a built-in display that may even allow you to use it without using a laptop. All that said, every room and system is different and you may or may not get the level of improvement I heard. Maybe you can find a way to demo one? Cable Company sells it so maybe you could return it with a relatively modest restocking fee? Hope this helps somewhat, and best of luck.
As others have stated you should do some physical room correction first.
This is advice based on my experiences;
Treat first reflections, front/back wall, corners and wall ceiling junction.
You will need a measurement device, highly recommend the Omni Mic system.
Bass issues are the most difficult to tame, especially if you have a smaller space that you can't move things around in to get out of the modes.
Bass traps were a no go for me, just not enough space.
I tried the DSpeaker Dual Core in the digital and analog domain, it would correct but I was never satisfied with the end sound.
Any device that worked in the digital domain that I tried always seemed to mess with the sound adversely.
I ended up inserting a Rives Parc just before my mono blocks, pure analog correction.
It is extremely transparent and did the bass correction that I needed without mucking up everything else.
You do not need the Rives software to set the Parc up, just a good measurement tool and enough patience to work through the learning curve, its really not that involved.
It is a shame that they are out of business.
There is a seller with two for sale on Audiogon, I feel that his asking price is too high, but he is taking offers.
Do not be fooled into thinking that you can not correct enough with only 3 bands of parametric correction per channel.
It works extremely well!

Does the Ayon have a digital out or better yet a digital tape loop? If not your system with a room correction device will have an A/D conversion step and you won't be using the D/A converter in the Ayon, but the one in the room correction component.

If your primary goal is to eliminate peaks resulting from bass room nodes than an alternative approach is to use an analog parametric equalizer. A used Rives is a good choice.
I understand that not everyone's significant other is cool with having a lot of tube traps and acoustic wall panels in their living room--and I count my wife among them. That's why I use Lyngdorf's RoomPerfect room correction system and it's simple to set up and use, plus the results are gratifying.

I have also used a fairly basic dbx 31-band stereo graphic equalizer with very good results... but usually you need a way of measuring the resulting response curve and it is done manually, band by band whereas the Lyngdorf does it automatically using measurements you take around your room with the included microphone.

From what I understand the DSpeaker EQ only adjusts frequencies from 500Hz and lower, and the Rives unit, while it is reputed to be fairly transparent, is also limited to what it can do, and I believe it only works in the bass. The Lyngdorf works full-range and reduces room reflections which can improve the fine detailing and imaging quite a bit. There is a lot of flexibility as to the adjustments you can make to the sound via remote control from your listening position, and that's another reason why I like it. It also has a bypass button so you can instantly compare the direct input signal to the EQ settings. For me this makes it a no-brainer.

While the Lyngdorf is not inexpensive, neither are acoustic panels, diffusers, helmholz resonators or tube traps... and none of those devices may work at the specific frequencies that your particular room needs corrected.

Many audiophiles are "purists" at heart, and as such are closed-minded to anything that does not fit their purist mindset. In the case of room acoustics and EQ keep in mind that most of the people giving advise have little or no experience working with electronic EQ. Even if they have tried electronic room equalization, there is a learning curve and they may have given up before they fully understood how to use their device effectively. That said, it's not exactly rocket science.

Everything I read indicates that the Dirac system is the way to go. Do some research and see if you agree...

-RW-
I did my research and I was willing to invest the time and money. I went with DEQX. No regrets.
RW, nevermind the research... have you actually used the product in your own system and if so what was your experience? If not, well, maybe you shouldn't be touting it...
I completely agree with Plato and RW is correct. Audio is technology and must be corrected them with electronic engineering. The last thing I want is to tweak and install Pads on my wall because it just telling people that my system needs help.
As far as I can tell, I have used all of the devices so far mentioned (as well as some others) and, honestly, they all work. The variables are:
1. Bass only or full range.
2. Analog only, analog in/out DSP or digital in/out DSP
3. Automatic implementation of filters from measurements or independent measurement and implementation (more hands on).
4. Single measurement point or multiple measurement points.
5. Single pass listening area measurement/correction or separate near-field correction followed by room correction.
6. Fixed or variable target curves.
7. Stereo or multichannel.
8. Hardware or software.

What device works best? Depends on your choices and your room acoustics.
Post removed 
I grew interested in acoustics and having a technical background and DIY inclinations, studied quite a bit, got a measurement mic, mic amp, REW software, and built a number of tube traps, Helmholtz resomators, etc. also worked a fair bit on layout. The benefit was very apparent, although my wife wasn't as happy with the ugly stuff in the living room. But proved room treatments are worth the effort.

My only source these days is a very optimized PC with hardware and software optimizations, feeding an Audiophilleo and Metrum Octave DAC, a Lamm LL2 pre, a McIntosh Mc275 amp, 3-way speakers and a pair of subs.

Recently I incorporated Acourate software. Along the lines of Dirac, but less automatic and more powerful. So far I have been using it for room correction only and it works wonderfully. Miles' Tutu playing now, sounding as real as ever before in my system. Imaging has improved a lot.

I guess purist is in the eye of the beholder. My purist plan is to go fully active 4-ways and enable Acourate ability to run digital crossovers, driver linearization, and time-alignment. An amp driving directly a speaker driver is as purist as it gets in my view.

A couple of good articles for those who might be interested in learning more, at computeraudiophile.com, by Mitchco:
Introduction to Acourate: explains the basics for a 2-channel system. What I'm doing.
Advanced Acourate: explains how he implemented his 3-way active system, linearized drivers, time-aligned.
"Many audiophiles are "purists" at heart, and as such are closed-minded to anything that does not fit their purist mindset. In the case of room acoustics and EQ keep in mind that most of the people giving advise have little or no experience working with electronic EQ. Even if they have tried electronic room equalization, there is a learning curve and they may have given up before they fully understood how to use their device effectively. That said, it's not exactly rocket science."

I would probably be classified as a purist. At least by your standards. I think you mean purist to be someone doesn't have the same opinion as you.

Lets say that you removed your stereo system from your listening room and put a piano in its place. Like most rooms, its not perfect, so for this example, lets say the room excites a range of frequencies in the upper mids. Those notes sound a little louder than the others due to room acoustics. How would you fix the problem? One way would be to open up the piano and modify it by putting more felt on the hammers to the keys in the problem frequencies. Now all of the notes have the same volume if you hit them with the exact same amount of force. A flat frequency response. Another option would be to just leave everything as is and just live with the problem if its not too bad. And finally, you can fool with the room and not the piano. As a purist, I would go with one of the two latter options. Given the components the OP has, I believe you would do more damage to the systems sound using processing, digital or analog, than choosing another option.

Some may argue that this is just my opinion. That's correct, it is. But I do base my opinion on actual experience, and not just guessing. I have a Behringer 24/96 digital EQ that destroys the sound of my Wadia CD player. I also have a dbx analog EQ that ruins the sound of whatever preamp it gets used with. So, in my opinion, the OP's Ayon CD player is just to nice a player to be run through processing.

One option to consider is if you live near a Guitar Center, they stock the processors I mention, and many more. They have a great return policy so if you try something and it doesn't work out, just return it.
Let's also not overlook the additional benefits of the DEQX compared to other options. The speaker correction that occurs before the room is taken into account. Tho Kal also seemed to find that the room correction wasn't making as significant a difference as the Dirac system did. However he also didn't take advantage of the DEQXpert service to see if that could do more for the speakers and roo effects.
05-08-15: Gammajo
Looking at room correction and all the threads I found seem old.
The "Is DEQX A Game-Changer" thread is essentially current, and is on-going. If you want to consider DEQX, and you haven't already seen that thread, I would consider it to be required reading.

Also, for background on loudspeaker time and phase coherence I would commend last year's "Sloped Baffle" thread to your attention. (Bob R., as you'll realize speaker time and phase coherence, as defined in this post, are unrelated to absolute phase (i.e., polarity), to which you were apparently referring in your post. And time coherence is something that only a very small minority of speakers inherently achieve, and is something DEQX attempts to correct via DSP prior to implementing room corrections).
05-08-15: Zd542
I do base my opinion on actual experience, and not just guessing. I have a Behringer 24/96 digital EQ that destroys the sound of my Wadia CD player. I also have a dbx analog EQ that ruins the sound of whatever preamp it gets used with. So, in my opinion, the OP's Ayon CD player is just to nice a player to be run through processing.
ZD, I would not extrapolate anything regarding DEQX or many of the other processors that have been mentioned from your experience with the Behringer or dbx units. As someone having considerable proficiency with computers, I'm sure you realize more than most that DSP and computer technologies have advanced by leaps and bounds since those devices were introduced. And although I'm usually among the first to caution people that in audio price and performance don't necessarily correlate, I think it says something that the flagship DEQX HDP-5 model costs well over 20 times as much as the Behringer.

I have an HDP-5 on order, BTW, which I will be receiving soon, and which will replace my preamp in addition to providing speaker and room correction functions. I ordered it from Nyal Mellor of AcousticFrontiers.com, who has a great deal of directly relevant expertise, offers a free webinar/walk through on the use of the associated software, as well as unlimited phone and email support. And both he and the DEQXpert service Roscoe mentioned can perform the entire correction process on a paid basis, via Skype. Nyal also provides 30-day return privileges, which I have no expectation of having to utilize. I will be chronicling my progress and findings in the "Game-Changer" thread.

Inputs to that thread from several A'gon members having both extensive DEQX experience and very high quality systems, including Psag who posted above, were among the major factors which have given me sufficient confidence in both the transparency and the effectiveness of DEQX to proceed down that path, given that a hardware solution best suits my particular circumstances. Kal's (Kr4's) review in Stereophile was also helpful.

Regards,
-- Al
Avoid room correction.
Thank you very much everyone - very helpful information. I would have gotten back but I was enjoying music all day through my new speakers! I did have a long talk with Tim at SimpliFi about the DSpeaker - he was very helpful. My Ayon would allow digital in and out after the transport section and back into the Ayon DAC which Tim recommended via glass toslink and an enhanced power supply. I can also go between pre and amps. With all the glass in my room I do like the idea of full range correction in case it is needed. I will check out the threads on DEQX and sloped baffle. Going to research this carefully.
Also Albert Von Schweikert (my speaker guy) likes to do it with 2 quality subs in rear of room attached to the speaker terminals and servo'd back to the main speakers so that the subs track the mains perfectly, plus then parametric equalization to even out bass modes. In some ways this appeals more than messing with the signal digitally, so I guess I lean more toward purist but hearing is believing, so an audition would be very sweet with any product. The two sub idea runs into my wife hating the idea of "any more boxes".
Using two subs is the best way to get a flat frequency response, unless the room is too small to allow the main speakers to be brought well into the room. DEQX will solve the timing and frequency problems of integrating subs with main speakers.
Coli Is that advice form experience with a particular piece of equipment?
Well, I read through the DEQX threads - seems intimidating to have to take the speakers (mine about 300 lbs each) into the yard, and then spend month dialing the thing in to get the best from it. But results seem excellent. My speakers are designed for excellent time and phase response across a wide axis. The Lyndorf idea of not changing the character of the speaker and amps etc, assuming people selected them because they liked them, is also logical to me. I am also wondering about waiting for Meridian's MQA to be incorporated into equipment as it sounds like it may be a game changer.
Some clarifications to some of the comments in Gammajo's post just above, for the benefit of others who may read this thread and want to consider DEQX:
Seems intimidating to have to take the speakers (mine about 300 lbs each) into the yard....
While it is theoretically ideal to do this, it is not necessary. That was clearly stated by experienced DEQX users in the "Game-Changer" thread I linked to.

The goal of the DEQX speaker calibration (aka "speaker correction") process is to make the speakers time-coherent (and therefore also phase coherent) at all frequencies above a lower limit falling in the area of roughly 200 to 500 Hz (our hearing mechanisms being most sensitive to phase and timing issues at mid-range and treble frequencies).

If the speaker calibration process is performed outdoors, so that there are no room reflections to degrade the accuracy of the process, that lower limit of the range of frequencies for which the process is effective will be as low as possible, within that area of 200 Hz to 500 Hz or so.

If the speaker calibration process is performed with the speakers moved to the center of the room, as far away from reflective surfaces as possible, that lower limit will be a bit higher than if the process was performed outdoors.

If the speaker calibration process is performed with the speakers in their normal position, that lower limit will be somewhat higher still.

So which of those three alternatives is chosen will simply affect how low in frequency the benefits of the process will extend. The mid-range and treble will benefit regardless of which alternative is chosen.
...and then spend month dialing the thing in to get the best from it.
My understanding is that if the DEQXpert service is used, or the comparable service provided by Acoustic Frontiers, the speaker and room calibration processes can be accomplished in a matter of hours. Or at most perhaps two sessions of a few hours each.

In my own case, I don't plan to use those services. And working at my own deliberate pace, having no previous experience with the product, and with the time I can devote to it limited to some extent by other activities and by the need to not perturb my wife's activities by playing test tones and loud music through the speakers (I use headphones when I want to listen at those times), I envision taking perhaps a month or so to get it fully dialed in. But that's just me.
My speakers are designed for excellent time and phase response across a wide axis.
Regardless of what manufacturer literature may say about time coherence, time alignment, phase response, phase linearity, etc., if the speaker has a crossover and if the crossover is not first order (meaning 6 db/octave), the speaker is not time coherent. If the speaker has a crossover and is not made by Vandersteen, Thiel, Green Mountain Audio, and perhaps one or two others, it is highly probable that its crossover is not first order, and that the speaker is therefore not time coherent.

For background on the benefits of time coherence (which in turn automatically implies phase coherence), see the "Sloped Baffle" thread I linked to earlier.
The Lyndorf idea of not changing the character of the speaker and amps etc, assuming people selected them because they liked them, is also logical to me.
Of course, with DEQX one could choose to simply not do the speaker calibration process, and just use some or all of its other functions (room correction, equalization, DAC, preamp functionality in some models, USB interface in some models, etc). But one would be losing out on what with many speakers in many rooms may be its most important benefit, that is not provided by most competitive products.

Regards,
-- Al
Almarg,

What a great post. Great synthesis of the potential of a DEQX.

Are you planning to go active with your speakers, getting rid of the passive crossovers?

You might recall I thought about the DEQX HDP-4 (at the time) and eventually opted for Acourate. Yet my end destination seems to be very aligned with yours. I opted to build a system around this concept and will build my own speakers, multi-amp, use active digital crossovers and get a time aligned, linearized, room corrected system.

I am technically inclined, but certainly less experienced/knowledgeable than you. It would be great for me to be able to bounce ideas/questions with you as you also go through this process. Such a fun project!
Thanks very much, Lewinski. Yes, I've followed the posts and threads related to your project, and I'm happy to comment whenever I can contribute anything meaningful.

As you realize, the three independently configurable pairs of output channels provided by the HDP-4 and HDP-5 can support active biamping or triamping, but I have no plans to do that. In part because doing so would entail what to me would be desecration of the fine craftsmanship that went into the construction of my speakers; in part because the innards of my speakers are not readily accessible as practical matter; and in part because in the absence of any knowledge of the design of the speaker's internal crossover I would by no means rule out the possibility that the sonic results would end up being a downgrade rather than an upgrade. And of course there would be a lot of expense for additional amplification.

Based in part on listening comparisons with my Stax electrostatic headphones I'm pretty much convinced that the weak link in my system is presently some combination of room effects (which I can't address with conventional room treatments since it is my living room), and speaker time incoherence. So I'm just looking for some modest improvement in those areas, and in the process perhaps I'll also benefit from substitution of the DEQX for my preamp, and from utilization of the DEQX's DAC function in place of the one that's internal to my CDP.

Yes, as you indicated these are fun projects, and also highly educational. Those are the main reasons I am intending to do it all myself rather than utilizing the DEQXpert or equivalent services. And if it takes a month or even two, I'm fine with that.

Best regards, and continued good luck with your project.
-- Al
Al,

Yes, your speakers are truly of fine craftmanship. I've never heard them, but always found them very appealing from what I read.

Are you sure the DEQX can achieve time alignment among the drivers if you are to keep the passive crossovers in there? My understanding is the time alignment is done between pairs of channels, at the crossover points, through linear phase crossovers. Hence the need for actively amping. Maybe DEQX is different, but I think I did exchange with a user about this. At least on Acourate, I know the system can't time align if it only sees two channels as it can't delay part of the signal within a channel. This is why this decision has been so difficult to make. My system will need to change almost completely.
Thru DEQX time alignment can be achieved with speakers with passive crossovers. As it measures the response to test tones, it digitally adjusts the arrival times of all frequencies measured. So differences between drivers as well as any time arrival differences that might be produced by a particular driver itself.
Lewinski, +1 to Roscoe's response. Some time ago I had read through the 143 page calibration manual and the 36 page user manual for the HDP-4, and I found many indications of various kinds that are consistent with it being able to perform timing corrections on single-amp'd speakers having their internal crossovers in place, and nothing that would indicate to the contrary.

Also, this post by member Drewan77, who as you've seen is extremely knowledgeable and experienced with DEQX, appears to have provided further confirmation with respect to my specific application.

Best regards,
-- Al
I know that with a regular EQ, digital or analog, any adjustments made alter phase of the frequencies adjusted. Can the DEQX get around this problem?
Gammajo: Let me clarify, avoid Auddyssey.

Vandersteen summed up my views quite well after that disaster. See
http://vandersteen.com/support/faqs
ZD, with respect to frequency response equalizations that may be introduced in the speaker calibration process the answer to your good question is certainly yes. I believe the same holds true for equalizations that are introduced in the room correction process, or subsequently by the user, but I can't say that with certainty. Perhaps one of the experienced DEQX users will chime in and confirm that.

Best regards,
-- Al
Thanks Al, Roscoe. I learnt something already.

Cheers!
I just want to thank everyone for making this thread intelligent, informative, encouraging and respectful. I had begun to fade my time on A'gon after too many uninformed opinions delivered with vitriol on too many threads. I am learning something here where the passion for excellent sound is trumping egos.
Bifwynne, did you ever take your preamp out while you used the DEQX?
Going to disagree with the 2 sub suggestion, I had 2 sub at one point, it lead to a worse sound than 1 sub.

Putting speaker right at the corners though, now that is magic.
Unsound ... in a way ... yes. I used my ARC CD-8 CDP as a transport and ran its digital output directly into the DEQX's digital input. On the margin, maybe a little better going "digital" direct as compared to using the CD-8's analogue output into the Ref 5 SE.

Nevertheless, I still use my ARC Ref 5 SE because it is a convenient way to handle other input sources, e.g., phono and TV. IMO, I think the close CDP performance says a lot about ARC gear quality.

Also ... though not logical, I can't bear the thought that my Ref 5 SE may be obsolete. :(
Gentlepeople-
I find this thread to be fascinating because I am not technically inclined but I believe that implementation of digital room and speaker correction may be in my future for several reasons:
1. I'm not a purist.
2. I mostly listen to digital files served wirelessly from a MusicVault server to a Modwright/Logitech Transporter.
3. My Transporter is beginning to fade away, I fear. One of the displays has quit. The work around is to use one of the smartphone/tablet apps, but it reminds me that this is an orphan product with limited; probably very limited repair potential.
4. The dac in the Transporter is limited to 24/96 and while I currently have a relatively low % of hi-rez files I'd like to think that will increase over time.
5. The wireless connection is a weak point because the router and server are upstairs in the SW corner, while the Transporter is downstairs in the NE corner. I know that there are solutions, but still, moving the server so it can be hard-wired to the player/DAC seems like the most foolproof approach.
6. The DEQX or similar device with a DAC could be inserted between the server and my pre-amp w/o having to add an additional A/D step.
7. I am running open baffle speakers w a single driver plus whizzer cone and dual on-baffle subs with the single drivers and subs driven off separate amps. The subs are driven by plate amps which take a speaker level signal from the tube amps that drive the mains. It seems to me that there are ample opportunities for phase and time alignment problems with such a configuration, yet overall, this is the most satisfying system I have had. My system is listed for a more complete description.
8. My system is in my living room, which constrains main speaker placement and rules out any significant room treatments.
9. I don't live too far from Almarg, who has kindly offered to be let me hear for myself what the DEQX product can do, once he gets it dialed in.
10. My speakers do not weigh 300 lbs and I have a large screen porch next to the LR, which I can use for the initial speaker correction analysis.

I'd love to hear thoughts from any of you as to whether or not the DSP approach makes sense under these circumstances. I know there is no substitute for hearing it, but I'm still early in the thinking stage. I'm also curious if anyone has any thoughts about frequency response correction vs. the observations of those who say that a perfectly flat FR sounds "un-natural".
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Michael (Swampwalker), here are my thoughts in response to your post:

Regarding the last question, about flat frequency response, see these paragraphs from the DEQX FAQ. Makes sense to me, and note that DEQX provides a goodly amount of flexibility in that regard, for both the speaker and the room calibration/correction processes. Also, keep in mind that a large number of user-created equalization settings can be set up in the DEQX, and selected among via the remote control.

Regarding the speakers, my instinct would be that the sonics of the 5 inch mains you are presently driving full-range would be likely to benefit from having deep bass frequencies kept out of them. Provided that the plate amps on the subs can accept line-level inputs, you could accomplish that by taking advantage of the DEQX subwoofer integration features.

If you were to do that, and if you were to place the DEQX ahead of the preamp in the signal path as you described, to keep the volume levels of the mains and the subs in sync you would use the DEQX's volume control to adjust volume, with the preamp's volume control set to a fixed position. DEQX volume can be adjusted via both the remote and the front panel.

Regarding item 4, a point to be aware of is that John Atkinson's measurements of the DEQX PreMate that were provided with Kal's review in Stereophile indicated that the DEQX downsamples 192 kHz data to 96 kHz, and 176.4 kHz data to 88.2 kHz. In the comments section following the review JA said the following, which makes sense to me:
Running powerful DSP at 4Fs sample rates is very consuming of resources, so this compromise is not uncommon. It is likely that the benefits of the DSP correction outweigh the potential drop in sound quality due to the downsampling.
(4Fs presumably refers to a sample rate of 4 times the redbook CD rate. 4 x 44.1 kHz = 176.4 kHz)

Best,
-- Al
It is well documented that multiple subs can achieve better results than an equivalent single sub in appropriately sized rooms. Typically smoother frequency response from spreading room nodes and higher output/lower distortion from twice the woofer radiating surface.
"It is well documented that multiple subs can achieve better results than an equivalent single sub in appropriately sized rooms. Typically smoother frequency response from spreading room nodes and higher output/lower distortion from twice the woofer radiating surface."

Onhwy61- I think the key word is CAN. You can definitely get higher output from twice the radiating area (and twice the amplifier power). With careful placement you SHOULD be able to get smoother frequency response. However, it seems to me that it is at least theoretically possible to 1. place the subs so that they reinforce the same room nodes, or 2. create additional nodes. Not likely, but possible. For example, #1 could be achieved by placing both subs in the front corners of the room. If a node were located at the listening position, it would be re-inforced. OTOH, if the subs had a phase switch, setting one to 0 and the other 10 180 might cancel that node. #2 seems least likely but also at least theoretically possible. I'm not an acoustician, so if I am wrong, someone please correct me.
to 180
Al, I agree that the advantages the DEQX bring to the table might (probably) outweigh the down sampling issue, but in that sub $100 DVD players can decode (yes I realize that's all) the native higher sampling rates, it is still somewhat disconcerting that an item that can cost close to $5,000 can't do it all in the native higher sampling rates.
I still wish there were more amps (preferably mono) that could accept direct digital input from devices like the DEQX.
Re: mono subs, I can't help but wonder if a mono sub when being fed summed stereo input might actually find itself competing with channel signals and actually subtracting information in the process. IME, stereo subs have always sounded better than a mono sub when fed stereo signals. But I suppose their could be an exception to my experience that works differently?
05-11-15: Unsound
Al, I agree that the advantages the DEQX bring to the table might (probably) outweigh the down sampling issue, but in that sub $100 DVD players can decode (yes I realize that's all) the native higher sampling rates, it is still somewhat disconcerting that an item that can cost close to $5,000 can't do it all in the native higher sampling rates.
Hi Unsound,

Your reaction is natural and understandable, and as you indicated you recognize that the DEQX processing is much more extensive than what a DVD player has to do. But I think that my use of "much more extensive" understates it considerably. What I envision is that the mathematical computations that are involved in the digital signal processing the DEQX has to perform on the fly, fast enough to keep up with the music data, are HUMONGOUS. My understanding of it is that in real time it has to divide the spectrum into thousands of frequency segments, mathematically determine the contents of each of those segments by converting the series of data samples from the time domain to the frequency domain (that conversion involving a huge amount of mathematics), mathematically adjust the delays and amplitudes of the contents of each of those frequency segments in accordance with the speaker and room calibrations that have been established, as well as in accordance with any additional equalizations that have been programmed, and then put everything back together and convert it back to the time domain (again, a huge amount of mathematics), while digitally adjusting the volume and then converting the data to analog. I think it would not be unfair to characterize the processing a DVD player has to do as not much more than a drop in the ocean compared to that.

I'd imagine that if 24/192 processing could have been implemented in the PreMate which JA measured in a reasonable manner without drastically complicating the design, and/or delaying release of the design considerably (perhaps by lessening the extent to which that design could draw upon their previous design work), and/or making the unit much more expensive, DEQX would have done so.

I don't know, btw, if the design of the more recent HDP-5 which I am getting processes 24/192 as 24/192 or downsamples it similarly. But I'm not concerned either way.

Best regards,
-- Al
Al,

Yes, your speakers are truly of fine craftmanship. I've never heard them, but always found them very appealing from what I read.

Are you sure the DEQX can achieve time alignment among the drivers if you are to keep the passive crossovers in there? My understanding is the time alignment is done between pairs of channels, at the crossover points, through linear phase crossovers. Hence the need for actively amping. Maybe DEQX is different, but I think I did exchange with a user about this. At least on Acourate, I know the system can't time align if it only sees two channels as it can't delay part of the signal within a channel. This is why this decision has been so difficult to make. My system will need to change almost completely.
Al, as usual your points are well taken. The thing is, as I understand it, the <$500 stereo software (sans hardware!) from DIRAC can handle the hi rez stuff.
But is DIRAC computationally doing all that the DEQX is, or is it just a well-implemented digital EQ?
^
http://www.dirac.se/en/online-store.aspx