DRC, Digital Room Correction- is it the poor relation to Room treatments?

[Audiophile Neuroscience]

Greetings all,

Firstly, I am (clearly) not an expert on this topic. Secondly, if DRC sounds better to someone then I am sure not going to try and convince otherwise.

My interest has been piqued by the ever growing DRC software and hardware solutions out there and such things as convolution engines in Jriver. These days it is also relatively common to see "jumpers" on high end speakers whereby you can tweak the speakers output and tonal balance. Similarly, components seem to be more commonly incorporating some form of DSP, whether pre-pros, reconstruction filters on DACS that might alter frequency response etc.

I would like to get your thoughts on any or all of the comments below.

Some people argue that DRC (or any form of DSP) is undesirable. Proponents of this thinking argue that 1) it first and foremost skews or butchers the direct, near field response from the speakers (which you paid good money to get), and 2) best to tamper with the audio signal as little as possible.

There is also the argument that DRC is typically calculated for only one listening position so perhaps not applicable for people that aren't anchored to the sweet spot.

What about the Schroeder frequency? My schoolboy physics interprets this to mean where sound wavelengths start acting more like rays than waves. In home listening environments its difficult to cram large wavelengths (20Hz@60 foot) into small boxes. They get poorly distributed and tend to crash into themselves forming positive (peaks) and destructive (dips) interference ie resonant modes/standing waves, and nulls. Somewhere around 100-200Hz sound waves start ricocheting off walls and spread more evenly. The suggestion is that DRC will do little for these higher frequencies which tend already to be fairly 'flat'. Additionally, it is the harmful first reflections that need taming and this cannot be done by altering the amplitude of the frequency. It is a timing issue not amplitude. Even DRC that adds delay (presumably for phase correction) wont correct this?

Then there is the perceptual element. Work by Sean Olive and Floyd E Toole suggest that not all listeners necessarily prefer DRC eqed sound.

Lastly can anyone explain how "room correction" differs from "speaker correction"? Isnt it the interaction of both whereby only the speakers frequency response is modifiable by DRC ?

Cheers

[Kal Rubinson]

Lastly can anyone explain how "room correction" differs from "speaker correction"? Isnt it the interaction of both whereby only the speakers frequency response is modifiable by DRC ?

Of course, the speaker response is modified by both room correction and by speaker correction and the latter has that as its intent. In products that distinguish the two, e.g., DEQX, the speaker correction is based on measurements which allow the software to distinguish the direct sound of the speaker from the contributions of the room acoustic by gating to exclude all but the early, direct response.

[wgscott]

Secondly, if DRC sounds better to someone then I am sure not going to try and convince otherwise.

 

Why not drop the posturing for a few minutes and download a free trial of Dirac (or whatever else suits you) and simply give it a try?

 

There are at least objective, measurable changes, potentially for the better, that can be introduced, which is more than one can claim for most audiophile tweaks.

[flak]

Hi

let me first make it clear that I'm answering your questions from a possibly biased point of view... Dirac Research

 

 

Some people argue that DRC (or any form of DSP) is undesirable. Proponents of this thinking argue that 1) it first and foremost skews or butchers the direct, near field response from the speakers (which you paid good money to get), and 2) best to tamper with the audio signal as little as possible.

 

Tampering with the audio signal (or butchering it if you want) is what our normal listening rooms do, actually placing a speaker in a room means applying a filter... the speaker position, the listening position and the room determine what this filter will look like.

We speak about it here: http://www.computeraudiophile.com/f23-dsp-room-correction-and-multi-channel-audio/dirac-and-frequency-shifting-19999/index2.html#post318605

 

There is also the argument that DRC is typically calculated for only one listening position so perhaps not applicable for people that aren't anchored to the sweet spot.

 

That happens with some DRC solutions but it is not necessarily true, Dirac Live can successfully correct a listening area as defined by the user.

An extreme example is the Barco cinema processor:

Digital Cinema audio processor - AP24-3D | Barco

 

What about the Schroeder frequency? My schoolboy physics interprets this to mean where sound wavelengths start acting more like rays than waves. In home listening environments its difficult to cram large wavelengths (20Hz@60 foot) into small boxes. They get poorly distributed and tend to crash into themselves forming positive (peaks) and destructive (dips) interference ie resonant modes/standing waves, and nulls. Somewhere around 100-200Hz sound waves start ricocheting off walls and spread more evenly. The suggestion is that DRC will do little for these higher frequencies which tend already to be fairly 'flat'. Additionally, it is the harmful first reflections that need taming and this cannot be done by altering the amplitude of the frequency. It is a timing issue not amplitude. Even DRC that adds delay (presumably for phase correction) wont correct this?

 

Dirac Live as well as a few other mixed-phase solutions do address amplitude but also phase issues in the time domain.

Mixed-phase solutions are quite recent so many don't know much about them... some info here:

http://diracdocs.com/Understanding%20more.pdf

 

Then there is the perceptual element. Work by Sean Olive and Floyd E Toole suggest that not all listeners necessarily prefer DRC eqed sound.

 

Again these mixed-phase solutions have become available in the last few years, the work by Sean Olive and Floyd Toole is antecedent.

 

Lastly can anyone explain how "room correction" differs from "speaker correction"? Isnt it the interaction of both whereby only the speakers frequency response is modifiable by DRC ?

 

It is not true that DRCs can modify only the speakers frequency response, actually good DRCs minimize the effect of the room/speakers interaction where necessary.

 

In a few words you see "ever growing DRC software and hardware solutions" because they are real solutions to a real problem which can be easily heard and compared as well as measured.

 

Ciao, Flavio

[Audiophile Neuroscience]

Hi Kal,thanks for your reply

Of course, the speaker response is modified by both room correction and by speaker correction and the latter has that as its intent. In products that distinguish the two, e.g., DEQX, the speaker correction is based on measurements which allow the software to distinguish the direct sound of the speaker from the contributions of the room acoustic by gating to exclude all but the early, direct response.

 

Okay, thanks. When i saw this done (only once) using a DEQX the 'sound guy' did ineed stick the mic in front of each speaker as well as the listening position. In amongst various technical information there was mention of speaker crossovers but I couldnt see how the DEQX would have a direct influence here (as opposed to boosting or cutting amplitude of frequencies fed to the speaker as a whole).

[Audiophile Neuroscience]

Hi Bill, thanks for your reply

 

Why not drop the posturing for a few minutes and download a free trial of Dirac (or whatever else suits you) and simply give it a try? There are at least objective, measurable changes, potentially for the better, that can be introduced, which is more than one can claim for most audiophile tweaks.

 

As you probably recall, I am a 'trust your ears over measurements' guy, so have no issue with people hearing differences, even if I can't (as yet) explain it.This applies to whether measurements are for or against hearing differences. My "posturing" in this case is to doubt the efficacy of DRC based on other peoples reasoning which make sense to me ( such as arguments forwarded by Barry Diament). The ONE time I have experienced DRC in action, it did not make any difference to my ears. I however remain open to the possibility and am respectful of other peoples opinions that feel DRC (or even a non verifiable "tweak") does make a difference. Its neat if the opinion correlates with measurements but for me its (usually) not a game changer if it does not.

[dallasjustice]

AN,

Can you tell us more about the experience you mentioned with DRC?

 

Michael.

[Kal Rubinson]

The ONE time I have experienced DRC in action, it did not make any difference to my ears.

 

Can you tell us more about the experience you mentioned with DRC?

Yes, please. I know of some who have been unimpressed or, even, negative about the sound with DRC but I have yet to experience a serious listener who did not hear any difference.

[Audiophile Neuroscience]

Hi Flavio, thanks for your reply and the links.I will take a look.

 

Hi

 

Tampering with the audio signal (or butchering it if you want) is what our normal listening rooms do, actually placing a speaker in a room means applying a filter... the speaker position, the listening position and the room determine what this filter will look like.

 

I get that and will read the link also. I still however am disturbed by the presumption that you will still hear the near field, direct sound first, and you want to hear it unaltered (unless the speaker itself is flawed).

 

Dirac Live as well as a few other mixed-phase solutions do address amplitude but also phase issues in the time domain.

Mixed-phase solutions are quite recent so many don't know much about them... some info here:

http://diracdocs.com/Understanding%20more.pdf

 

Again these mixed-phase solutions have become available in the last few years, the work by Sean Olive and Floyd Toole is antecedent.

 

Correcting for phase, I think I can understand but as I previously hypothesized, this would have little influence on first reflections or indeed reverberation times ?? These are the time domain issues I wondered about.

 

In a few words you see "ever growing DRC software and hardware solutions" because they are real solutions to a real problem which can be easily heard and compared as well as measured.

 

I just wondered whether it was becoming seen as a panacea for the treatment of room acoustics whereas I would conjecture (read guess) it has a legitimate place when used judiciously and within its limitations . I have had an audio dealer say to a friend, "If you dont want any room treatments we can fix it all by selling you this room correcting hardware, brand X"

[Audiophile Neuroscience]

Hey Michael,

AN,

Can you tell us more about the experience you mentioned with DRC?

 

Just the one, so the jury for me is still well and truly still out. As mentioned to Kal, it involved a friend who purchased a DEXQ and arranged for a sound guy to set it up. He came with mac laptop, mic stand etc and went through the procedure. he identified a small flaw in the speakers and some relatively minor anomalies in the room.He provided 3 filters as possible corrections which we could toggle through using the remote during listening. It made no difference to my ears but as said the deficiencies identified and corrected were relatively minor. OTOH my friend heard significant differences when listening at the dealer's showroom. he also did not hear much difference at his home.

[dallasjustice]

AN,

It's fun to debate these things. We can talk about minimum phase vs non-minimum phase and other aspect of room acoustics. I had the same "objections" you are stating before I tried DIRAC. I agree that most (not all) you hear at seated position above Schroeder is direct sound. However, using only extreme choices and examples isn't productive and simply demonstrates a lack of experience, IMO. I would say the same thing to Barry Diament as well. I've heard his theoretical objections. But I have never heard any specific experience or examples from whence this supposed experience with DSP is drawn. Until then, it's just debating. I already went to law school, so I don't feel like. Get some real experience. It costs the same as arguing and it's much more fun. :-)

[dallasjustice]

I own and use a DEQX HDP-4. I don't use the PEQ because it sucks. It's old school. Products like DIRAC are light years more advanced.

 

Hey Michael,

 

 

Just the one, so the jury for me is still well and truly still out. As mentioned to Kal, it involved a friend who purchased a DEXQ and arranged for a sound guy to set it up. He came with mac laptop, mic stand etc and went through the procedure. he identified a small flaw in the speakers and some relatively minor anomalies in the room.He provided 3 filters as possible corrections which we could toggle through using the remote during listening. It made no difference to my ears but as said the deficiencies identified and corrected were relatively minor. OTOH my friend heard significant differences when listening at the dealer's showroom. he also did not hear much difference at his home.

[Audiophile Neuroscience]

AN,

Get some real experience. It costs the same as arguing and it's much more fun. :-)

 

cant argue with that ;-)

[Audiophile Neuroscience]

Yes, please. I know of some who have been unimpressed or, even, negative about the sound with DRC but I have yet to experience a serious listener who did not hear any difference.

 

Kal, comparing effectiveness, what is your impression of a software solution like Dirac Live vs Trinnov Audio Optimiser hardware which you reviewed in 2013 ? Irrespective of cost differences I,m thinking this is an area changing potentially way too fast to invest in a hardware solution?

Music in the Round #62 Page 2 | Stereophile.com

[Kal Rubinson]

Kal, comparing effectiveness, what is your impression of a software solution like Dirac Live vs Trinnov Audio Optimiser hardware which you reviewed in 2013 ? Irrespective of cost differences I,m thinking this is an area changing potentially way too fast to invest in a hardware solution?

Music in the Round #62 Page 2 | Stereophile.com

I really cannot answer that yet as I used the Trinnov in one syste/room and the DL in another. Hope to have an answer soon.

 

I have come to prefer, in principle, a software solution.

[Audiophile Neuroscience]

I really cannot answer that yet as I used the Trinnov in one syste/room and the DL in another. Hope to have an answer soon.

 

I have come to prefer, in principle, a software solution.

 

Okay and many thanks.

Kind Regards

David

[Maerten]

I am fully satisfied with my Behringer FBQ2496. All in one solution for me

[S.o.k.]

Hi. I own a Deqx hdp-4 and i am very happy with it's performance. I am not a fan of roomcorrection and if used, i Think it is only usefull in the subregion.. i am useing and still expanding, acustic panels (owens corning 703) in to large panels over and between the listningposistion and the speakers. i have used and Will Again the Deqx roomcorrection to tame my 4 13" corner subs. I Think that higher frequenze correction, as done with for exampel Lyngdorf (perfect room) makes the sound "dead". Sound and ease of use, is more importen for me, then specs. Curves and measurement.

[TraKtorman]

Hi. I own a Deqx hdp-4 and i am very happy with it's performance. I am not a fan of roomcorrection and if used, i Think it is only usefull in the subregion.. i am useing and still expanding, acustic panels (owens corning 703) in to large panels over and between the listningposistion and the speakers. i have used and Will Again the Deqx roomcorrection to tame my 4 13" corner subs. I Think that higher frequenze correction, as done with for exampel Lyngdorf (perfect room) makes the sound "dead". Sound and ease of use, is more importen for me, then specs. Curves and measurement.

 

My take on all this is that DRC can be a very effective complement to room treatments. I have used a DBX PA, a Lyngdorf, and now own a DEQX hdp-4. Used in two different systems all have made an audible improvement to my listening experience. However, the better the speakers and the better the room the less audible improvement is heard as far as equalisation is concerned. That said, the DEQX brings recorded music into focus in a way that equalisers like the DBX cannot. From my experience I would recommend both the Lyngdorf and the DEQX, though the latter, as you know, requires some skill to set up.

[bdiament]

AN,

It's fun to debate these things. We can talk about minimum phase vs non-minimum phase and other aspect of room acoustics. I had the same "objections" you are stating before I tried DIRAC. I agree that most (not all) you hear at seated position above Schroeder is direct sound. However, using only extreme choices and examples isn't productive and simply demonstrates a lack of experience, IMO. I would say the same thing to Barry Diament as well. I've heard his theoretical objections. But I have never heard any specific experience or examples from whence this supposed experience with DSP is drawn. Until then, it's just debating. I already went to law school, so I don't feel like. Get some real experience. It costs the same as arguing and it's much more fun. :-)

 

Hi dallasjustice,

 

If you have never heard of any specific experience or examples from whence my experience with DSP is drawn, either I haven't mentioned it in any recent posts or you haven't read any where I did mention specifics. Would you then draw the conclusion that when I say "in my experience" that I haven't actually experienced any DSP systems? If so, I would submit there is no logical basis for such as it is not based on any data. (Put another way, if I didn't have any experience with them, I wouldn't say "in my experience". ;-})

 

In the past, I've mentioned a number of systems I've heard. I even wrote the user manual for one that is widely used. At this point, I don't like to mention any particular brand names for gear I don't like. (Remember the old adage? "If you don't have something nice to say about someone [or something], don't say anything.")

 

Lastly, I don't debate. I report what I hear. I understand other folks hear things differently and will have their own preferences. I never argue with whatever brings anyone their listening pleasure. All that said, I'll reiterate that *for me* every instance of speaker or room "correction" I've heard (at least half a dozen different approaches from different designers so far) has made for immediate and obvious changes to the sound -- as I hear it, always negative. I believe in correcting problems at their source as it is the only approach I've heard that truly works and further does not actually *add* problems, let alone leave the original issue unfixed.

 

In my view, when/if such a "correction" algorithm can actually shorten decay time and leave the direct response from the speakers unaltered, it *might* work. Meanwhile, I maintain that trying to fix time-based problems with amplitude-based solutions (effected in places *other* than where the problems originate, no less) is like trying to fix a broken arm by wearing a different hat.

 

Just my perspective, of course.

 

Best regards,

Barry

Soundkeeper Recordings

http://www.soundkeeperrecordings.wordpress.com

Barry Diament Audio

[wanta911]

I have a DEQX PreMate which is only used for bass management. It was setup remotely by DEQX and I have 3 room correction settings:

 

1. Up to 200hz

2. Up to 300hz

3. Up to 500hz

 

I basically leave it on option 2. I also use the USB asynchronous DAC which is very good.

 

Before the PreMate I always had at least one major null and one major spike in the LF, moving the speakers just moved where they sat in the frequency range. I have played around with the other EQ features but have decided not to use them, my room is reasonably well treated for mid and high frequencies. I won't "gush" about how good it is, other than to say that a click of a button on the remote reveals what my setup used to sound like and there is no way I ever want to go back to that!

 

So, I am a big fan of room correction in the low frequencies.

[flak]

Meanwhile, I maintain that trying to fix time-based problems with amplitude-based solutions (effected in places *other* than where the problems originate, no less) is like trying to fix a broken arm by wearing a different hat.

 

Just my perspective, of course.

 

Best regards,

Barry

 

Hi Barry,

 

yes, fixing time-based problems with amplitude-based solutions does not work when the system (speakers+room) behaviour is not minimum-phase... you need a mixed-phase solution.

I believe that most, if not all, the DRC solutions that you have tried were minimum-phase so I agree that the results may have been sometimes (but not always) unsatisfactory.

A short explanation of what Dirac Live is doing instead has been posted here:

http://www.computeraudiophile.com/f23-dsp-room-correction-and-multi-channel-audio/drc-versus-equalizing-analogue-or-digital-change-frequency-response-often-be-more-linear-pros-cons-23419/#post397762

 

Best, Flavio

[bdiament]

Hi Barry,

 

yes, fixing time-based problems with amplitude-based solutions does not work when the system (speakers+room) behaviour is not minimum-phase... you need a mixed-phase solution.

I believe that most, if not all, the DRC solutions that you have tried were minimum-phase so I agree that the results may have been sometimes (but not always) unsatisfactory.

A short explanation of what Dirac Live is doing instead has been posted here:

http://www.computeraudiophile.com/f23-dsp-room-correction-and-multi-channel-audio/drc-versus-equalizing-analogue-or-digital-change-frequency-response-often-be-more-linear-pros-cons-23419/#post397762

 

Best, Flavio

 

Hi Flavio,

 

To be clear, as mentioned elsewhere in my post and in other places I have written about the subject, the time-based issues I refer to are *decay* time in the room, not attack time from various drivers in a speaker.

 

While the latter can be dealt with using DSP (although not as well as if the speaker/crossover designer did their job correctly), the former (i.e., decay time in the room) is outside of the realm of current technology as far as I know, unless time travel is somehow built into the algorithm. ;-}

 

This has nothing to do with minimum phase or mixed phase. It *does* have to do with the assumption that speaker response and room response will sum algebraically independent of time (i.e., that we don't hear these as two different things).

 

Again, I understand that some folks like the results of DSP. I prefer a different approach to setting up monitoring and the room.

 

Best regards,

Barry

Soundkeeper Recordings

http://www.soundkeeperrecordings.wordpress.com

Barry Diament Audio

[dallasjustice]

Barry,

Time and frequency are two sides of the same coin, if we are talking about typical minimum phases ringing in a room. So, you ABSOLUTELEY CAN reduce the decay time of said minimum phase ringing with an appropriate EQ adjustment. This isn't my opinion. There are mathematical proofs and real world tests which anyone can do for themselves to demonstrate. IOW, EQ applied to minimum phase phenomen work in BOTH frequency and time domains. Read this thread:

 

Acoustic Measurements: Understanding Time and Frequency

 

 

 

Michael.

 

Hi Flavio,

 

To be clear, as mentioned elsewhere in my post and in other places I have written about the subject, the time-based issues I refer to are *decay* time in the room, not attack time from various drivers in a speaker.

 

While the latter can be dealt with using DSP (although not as well as if the speaker/crossover designer did their job correctly), the former (i.e., decay time in the room) is outside of the realm of current technology as far as I know, unless time travel is somehow built into the algorithm. ;-}

 

This has nothing to do with minimum phase or mixed phase. It *does* have to do with the assumption that speaker response and room response will sum algebraically independent of time (i.e., that we don't hear these as two different things).

 

Again, I understand that some folks like the results of DSP. I prefer a different approach to setting up monitoring and the room.

 

Best regards,

Barry

Soundkeeper Recordings

http://www.soundkeeperrecordings.wordpress.com

Barry Diament Audio

[bdiament]

Barry,

Time and frequency are two sides of the same coin, if we are talking about typical minimum phases ringing in a room. So, you ABSOLUTELEY CAN reduce the decay time of said minimum phase ringing with an appropriate EQ adjustment. This isn't my opinion. There are mathematical proofs and real world tests which anyone can do for themselves to demonstrate. IOW, EQ applied to minimum phase phenomen work in BOTH frequency and time domains. Read this thread:

 

Acoustic Measurements: Understanding Time and Frequency

 

Michael.

 

Hi Michael,

 

Time and frequency are two sides of the same coin, indeed. However we're talking about two different coins: the speakers and the room.

The room's ringing is diminished--somewhatby having the speakers' response diminished at the frequencies in question. This leaves us with a skewed direct response from the speakers. (I'm not so sure the additional processing isn't also imparting its own "color" on top of everything else. Certainly in the systems I've heard, I think that is a part of the problem. Not the main part but a component.)

 

Again, one of several assumptions being made is that the direct response from the speaker and that from the room will sum algebraically as a unit, rather than be heard as two distinct sounds. I'm sure some listeners are not sensitive to this but I'm equally sure other listeners, myself included, are.

 

As I always say, what is "good", "better", or "best" depends entirely on exactly what one is seeking. I understand you like the results you get and I wouldn't argue with that. I'm just saying I prefer a different approach that involves addressing problems at their source. To my ears, this is the only path I've heard that works.

 

Best regards,

Barry

Soundkeeper Recordings

http://www.soundkeeperrecordings.wordpress.com

Barry Diament Audio