Room Correction for 2 Channel?

[FrantzM]

Hi

I am in the 2-channel camp , while, waiting for the MC to become what was/is/has been promised... I don't have extended experiences with Room Correction Systems. I have heard the Tact in several occasions, dabble some with the RDP-1 and heard a Sigtech .. That's all. I can't talk with any semblance of authority on the subject. I can only say that it is the future...
Now about signal purity. I am one of those purists too. I had a "clean" system based on minimalist interference with the electronics.. Down to my power which had ABSOLUTELY nothing to do with the commercial grid. I will explain my approach to power in another post, if there is any interest in this, to me, important subject ... What I've come to understand these past few years more so than before, I would say these past 5 years, is that the speakers-Room interface is messing up with the signals in the medium in ways the cheapest electronics don't .. I don't mean by that to acquire a top of the line speaker and throwing a cheap Magnavox HTB receiver to drive it ..No ! Simply that the signal that we so lovingly try to maintain "pure" is very often a poor reflection (pun-intended) of itself when it arrives at our ears; courtesy of our speakers and our, in many cases not all mind you, poorly-treated rooms and far-from perfect speakers... That is a fact that only recently audiophiles have beginning to grapple with...
DRC can take care of certain aspects of this interface, the Room-Speaker interface, in ways that good old analog EQ can't ... For a system in an optimum room, Digital Correction may not be at all necessary, if all we are thinking is ROOM correction. However these systems are capable of much more: They can correct speaker drivers aberrations. Systems like the DEQX allow us to implement all kind of impossible to implement crossover order ,slopes and driver correction in an almost transparent way ... So I don't seem these anathema to signal purity if what arrives at the ear, what finally counts, is a better approximation of the source signal ..
As a final thought we do try to maintain signal purity but often we mess up with the signal in the most basic way.. Several cables have network which sole purpose is to change what passes through them: one of the most expensive cable even has an "Articulation Control" built-in ... So I am not too sure the signal that comes out of it is "pure" anymore, it may (and that is debatable) do less harm than the ealry DRC, I wouldn't know, but harm, it inflicts to the signal ...

Frantz

 

[amirm]

You know, I would love to see the response of a "well corrected" room. Some of the ones I have seen still have fluctuations of 5 db. Typical room probably has 20 to 30db deviation from flat response! Would you buy a CD player which had that kind of response? I suspect not. So why is it OK for the room+speaker to impart such large variations?

In video, we have a reference we apply to make sure we are compliant with the standard. In audio, it seems far more ad-hoc but perhaps achieving a linear response would be the closest to it. So unless one has at least measured the room, one cannot say that the room is well corrected and optimized. I suspect small rooms are rarely if ever well corrected.

To be sure, the processing can also do bad things. They are black boxes with unknown functionality at the detail level so it is hard to say that they are not damaging things in other ways. But they do take out a large chunk of response anomalies.

 

[Kal Rubinson]

You know, I would love to see the response of a "well corrected" room. Some of the ones I have seen still have fluctuations of 5 db. Typical room probably has 20 to 30db deviation from flat response! Would you buy a CD player which had that kind of response? I suspect not. So why is it OK for the room+speaker to impart such large variations?

Well, it ain't but +/-5dB is better than 20-30dB of variation, depending, of course on where those variations are. In addition, a decent EQ will also make for more uniform decay. But I do agree that "seeing" the results as objective measurements is important.

In video, we have a reference we apply to make sure we are compliant with the standard. In audio, it seems far more ad-hoc but perhaps achieving a linear response would be the closest to it. So unless one has at least measured the room, one cannot say that the room is well corrected and optimized. I suspect small rooms are rarely if ever well corrected.

"Well corrected" is a relative term and flat, in a small room, may not be psychoacoustically ideal, but I hope you agree that reducing FR variations is advantageous, all other things being equal.

To be sure, the processing can also do bad things. They are black boxes with unknown functionality at the detail level so it is hard to say that they are not damaging things in other ways. But they do take out a large chunk of response anomalies.

As ever, it is a question of trade-offs in the real world.

 

[amirm]

but I hope you agree that reducing FR variations is advantageous, all other things being equal.

Absolutely. And if a sub is used, proper blending of it. The only time I have heard a sub integrated perfectly with the rest of the speakers is with some processor involved. Not saying it can't be done otherwise but I have not heard it. Yes, a normal configuration might sound fine but then you put that one other CD in there and then all of a sudden, the bass is overbearing.

 

[audioguy]

In an ideal world, digital room correction (hereafter referred to as DRC) would not be necessary because we would all have our dedicated rooms built from scratch, designed by competent engineers and have appropriately used passive room treatment.

But VERY few audiophiles are fortunate enough to have that kind of setup. In the 10 years I visited homes to demonstrate or install SigTechs probably less than 20% even had dedicated spaces. And theses systems in most cases were placed in ordinary living spaces and had limited passive treatment (WAF?). So a digital room corrections device was the ONLY way they could extract reasonable sound out of their systems. And even in those non-dedicated spaces that did have room treatments, digital room correction made a huge improvement. Since the device I was selling ranged in price from $7K to $13K, all of the systems we visited would certainly be classified as high end: The Big Wilsons, Genesis, Avalons, Dunlavy, etc.

And in the dedicated spaces we visited, the benefits of DRC still far outweighed any "potential" signal degradation that may or may not have been audible. I can say categorically that I have only been in ONE room where room correction did ZERO. It was, as was Mike Lavigns, a level III Rives room, built from the ground up specifically for the purpose of two channel audio and HT. So if my sample rates are even close, maybe 1/3 of 1% have rooms that would get zero benefit from room correction. Actually, there was one other room. That room had three walls of solid glass, no treatment and sounded absolutely awful before and after DRC.

Admittedly, some rooms benefit a lot more than others, but most room do benefit. And just to make sure all understand, I am talking about an impulse driven, time domain based solution --- NOT frequency based EQ, parametric or otherwise.

A small example: Even in a "perfectly" symmetrical room, the measured impulse is usually not identical for the two channels...and hence the FR is not identical either. So, continuing with that example, if one channel has a slight (a db or so) peak (as compared to the other channel) at, say, 1K, there represents the real possibility that some level of image instability will occur. The more identical the FR, the more stable the image...and in my experience the only way to get that in most rooms is through DRC.

As to the detrimental effect of processing required to have a DRC in the system, there are a couple of ways to look at that.

(a) Audibility: Some time ago, Michael Fremer made some CDR's from his Rockport turntable to use as references when listening to other systems. I don't remember the name or model number of the device he used but IIRC, it had a a fairly high resolution sampling rate. While he said he thought he could hear slight differences between the original LP and his copies, he was clear that he would not want to try to hear those differences in a blind test. I have done the blind testing doing on the fly conversion of LP"s to digital and back and while I won't say there was no difference, there was none we could consistently pick blindly.

As to doing digital correction on a digital signal that can then be passed to an external high quality DAC, I would LOVE anyone to take that double blind test if the correction system were put into bypass.

(b) Practicality: But even if one could consistently pick, either from an analog source or digital source that the signal quality had been degraded at some level, I STILL maintain, with LOTS and LOT and LOTS of examples to prove it, that the room distortions with NO DRC were many, many orders of magnitude higher than any distortions that may be present within the processing itself.

I don't pretend to be familiar with all of the high end DRC products on the market, but I do know that when implemented correctly, in MOST cases, the musical significance of the improvements wrought are far above any downside that may exist.

While I currently have 4 SigTechs (one of which is still working), a Tact 2.0, and Audyssey SubEQ, I have just ordered a Tact 2.2XP to put into my system. Can't imagine audio life without it!

 

[Mike Lavigne]

In an ideal world, digital room correction (hereafter referred to as DRC) would not be necessary because we would all have our dedicated rooms built from scratch, designed by competent engineers and have appropriately used passive room treatment.

But VERY few audiophiles are fortunate enough to have that kind of setup. In the 10 years I visited homes to demonstrate or install SigTechs probably less than 20% even had dedicated spaces. And theses systems in most cases were placed in ordinary living spaces and had limited passive treatment (WAF?). So a digital room corrections device was the ONLY way they could extract reasonable sound out of their systems. And even in those non-dedicated spaces that did have room treatments, digital room correction made a huge improvement. Since the device I was selling ranged in price from $7K to $13K, all of the systems we visited would certainly be classified as high end: The Big Wilsons, Genesis, Avalons, Dunlavy, etc.

And in the dedicated spaces we visited, the benefits of DRC still far outweighed any "potential" signal degradation that may or may not have been audible. I can say categorically that I have only been in ONE room where room correction did ZERO. It was, as was Mike Lavigns, a level III Rives room, built from the ground up specifically for the purpose of two channel audio and HT. So if my sample rates are even close, maybe 1/3 of 1% have rooms that would get zero benefit from room correction. Actually, there was one other room. That room had three walls of solid glass, no treatment and sounded absolutely awful before and after DRC.

Admittedly, some rooms benefit a lot more than others, but most room do benefit. And just to make sure all understand, I am talking about an impulse driven, time domain based solution --- NOT frequency based EQ, parametric or otherwise.

A small example: Even in a "perfectly" symmetrical room, the measured impulse is usually not identical for the two channels...and hence the FR is not identical either. So, continuing with that example, if one channel has a slight (a db or so) peak (as compared to the other channel) at, say, 1K, there represents the real possibility that some level of image instability will occur. The more identical the FR, the more stable the image...and in my experience the only way to get that in most rooms is through DRC.

As to the detrimental effect of processing required to have a DRC in the system, there are a couple of ways to look at that.

(a) Audibility: Some time ago, Michael Fremer made some CDR's from his Rockport turntable to use as references when listening to other systems. I don't remember the name or model number of the device he used but IIRC, it had a a fairly high resolution sampling rate. While he said he thought he could hear slight differences between the original LP and his copies, he was clear that he would not want to try to hear those differences in a blind test. I have done the blind testing doing on the fly conversion of LP"s to digital and back and while I won't say there was no difference, there was none we could consistently pick blindly.

As to doing digital correction on a digital signal that can then be passed to an external high quality DAC, I would LOVE anyone to take that double blind test if the correction system were put into bypass.

(b) Practicality: But even if one could consistently pick, either from an analog source or digital source that the signal quality had been degraded at some level, I STILL maintain, with LOTS and LOT and LOTS of examples to prove it, that the room distortions with NO DRC were many, many orders of magnitude higher than any distortions that may be present within the processing itself.

I don't pretend to be familiar with all of the high end DRC products on the market, but I do know that when implemented correctly, in MOST cases, the musical significance of the improvements wrought are far above any downside that may exist.

While I currently have 4 SigTechs (one of which is still working), a Tact 2.0, and Audyssey SubEQ, I have just ordered a Tact 2.2XP to put into my system. Can't imagine audio life without it!

blind testing, double-blind testing, or any such approach to decision making for system development is dubious at best IMHO. i know that many do place ultimate faith in the results of that type approach as gospel......but i only have confidence in extended listening in my environment for system development decisions.

i'm only speaking for myself here and am not trying to say what the ultimate truth is. everyone is entitled to their own opinion.

 

[audioguy]

blind testing, double-blind testing, or any such approach to decision making for system development is dubious at best IMHO. i know that many do place ultimate faith in the results of that type approach as gospel......but i only have confidence in extended listening in my environment for system development decisions.

i'm only speaking for myself here and am not trying to say what the ultimate truth is. everyone is entitled to their own opinion.

The emphasis of my response was not meant to be a proclamation of blind testing versus long term listening. I was trying to emphasize (apparently unsuccessfully) the magnitude of the distortions introduced by the room vis-a-vis the distortions potentially introduced by the digital processing, and that in my experience and that of many, many others, it was pretty easy to pick a winner.

But I am not unbiased in this issue. As noted, I have heard hundreds and hundreds of rooms with and without DRC in a direct, real-time comparison and in long term listening. For the majority of rooms/systems, DRC is a plus. But clearly not for everybody

 

[FrantzM]

Several interesting threads in Audiophiles forums have been destroyed by trolls .. shouting “Blind Tests!” at any mention of subjective impressions or opinions. The very notion of Blind Testing has become anathema to audiophile sensibilities.

Let’s conduct a thought experiment here :
On one side a Tube Audiophile Caliber but not Stratospheric system: Preamp , Phono Stage and Mono-block amplifiers… On the other side : A Receiver driving a decent but efficient speaker, again not stratospheric speaker…. Most audiophiles (Myself included) will assume… before hearing one note that the tubes contraption is better … That is why removing some knowledge of what is being played, increases the accuracy of the observation and the chances of making a more objective and ultimately better decisions , opinions or observations; and that is what blind testing, sometimes brings to the table … Some make of it a gospel, often people who do not even begin to understand the logistics involved in a true blind test , nor its limitations.. But it is a good tool and can help. It is unfortunate that Audiophiles have, removed it from their testing methodologies. I believe it has its place, coupled with long term evaluation.
I am always amused by what I have termed the audiophile cowboys, those who will make a decision after having heard a few notes, often without any prior reference to what they heard ought to sound, pronounce a quasi-permanent verdict ..
Now I have also seen and measured rooms which distorts the sound much more than any cable or any amplifier could. I have seen audiophiles in very bad rooms going toward ever more expensive or eccentric gears while their room remained untreated and bad in itself, producing gross, spatial and frequency aberrations only a 64 Kb/s mp3 encoder could be proud of … I have heard audiophile systems , some of them quite expensive which made a cello sound like a bassoon while their owners were marveling at the glorious midrange (which was the ONLY range this system did not distort absurdly) … It has dawned to me that for too long audiophiles have paid attention to the wrong things, while leaving the fundamentals inadequate. The room is the key. It starts with good rooms then good speakers, the rest is icing on the cake .. Any cake starts with FLOUR and Butter the rest is added-on, no flour and butter (or margarine for those who want to destroy their health) no Cake,.. same with audio, gross frequency aberrations in a room result in a faulty, FUNDAMENTALLY flawed system . It could be that one enjoy his or her system the way it is.. And that is fine, the same way some people prefer Tang to real Orange Juice but they should at least know they are not drinking OJ when consuming Tang. They should know that their system does not in any way simulate the real thing …
I also was quite interested with Michael Fremer comments on the capture of his Sirius TT by a digital system. He pondered if he could reliably recognize his TT .. IOW without the knowledge of which is which, it would be difficult for him to pronounce, to recognize … He is not alone , many would be quite surprised by how they would fare in such tests .
If it is about trying to reproduce the real thing it seems that DRC could profit most systems. Now for those with well designed and / or treated rooms it is a different issue and DRC may create more problems than it solves but for a good portion of audiophiles, some would say majority, DRC holds the key to more enjoyment.

Frantz

 

[amirm]

I think the problem most audiophiles have with room treatment is that there are neither clear or definitive answers. Check into one of the long, long threads on other forums and you see experts engaged in cat-fights, each taking opposing views! "Bass trap works. No, Bass trap doesn't. You need diffuser in the front wall. No you don't diffuser there. Pressure is zero at the corner. No, pressure is not zero." It goes on and on and on.

In contrast, the person seems more confident going and upgrading to a different speaker hoping to get a better sound.

This is where room correction comes in. It deals with room effects without you having to know much. If you have a room that is untreated more mostly untreated, the difference RC makes is incredible. I remember reading the 10/10 review of TacT some decade ago and even that review did not convey the message until I powered it on. No amount of reading "the room walls go away" did justice to it until well, my room walls went away . You get a relaxed, articulate sound that is just hard to describe.

Yes, yes, there is no perfection. I sometimes sense something is not right with the sound. But there is far more right than wrong with room correction in majority of rooms. At least in my experience with TacT.

 

[audioguy]

My response to both Amir and Frantz echoes the occassional outburst in our church: "Amen, Amen and Amen"

 

[brianherlihy]

i have found this thread very interesting. i think Amirm captures this process best in stating that it is intimidating. i am in Vienna for holiday and wandered into a hi-fi store this morning, where the owner was going through a demo with a client for the new B&W digital sources with built in DRC. [i have little experience with DRC beyond some experiences in friends HT (i am purely a 2 channel guy and presumed i didn't need it)] - back to my experience in Vienna, i was very surprised by the sound produced. what surprised me, was that the hi-fi shop did not have a 'good' listening room, rather he had a large rectangular room that was set up with two listening areas going across the width (imagine multiple youth soccer games being played across the field), effectively creating an irregular listening room (3 walls and an open space). he was raving about the new B&W system and they invited me to a listen. i only had an hour but i was impressed (these were monitor b&w's with decent cabling) but a real full sound and 'even' across the room. he went on and on about room correction, so i sought this thread out when i got back to the hotel. Anyway, my point is this, i am intrigued - i have an irregular room in a loft with Rives level 2 treatment, which is still under construction. i will move the whole system in by end of July. i have several upgrades in the work as a coincidence of the renovation. i will not do anything till i am set up but i would like to get better educated on DRC as a matter of curiosity. My question then is what are the options? i am sure this is a loaded questions as there are many ways to go about it, but where do you start? i do have subs (2 x F113 JL Audio - coupled with on order Magico Q5's). but would i be looking at a digital cross over, an EQ, a system between line amp and monoblocks? maybe too broad a question, but am curious to get your guys input.
[as a qualifier, i wont do anything till i have my room up and running - i am in the curious mode] i should also note that i am a believer that it is near impossible to damp below 80 Hz. the waves are too long- i have built an isolated floor, and gone to great lengths to decouple my system from the room (this is a practical issue too as i live in a four story brick loft building and don't want neighbors complaining about bass reverb) - so i am really curious about input on bass here --> i would love to have gothams or F212 but am afraid to for this reason.

 

[Steve williams]

Brian

If you are decoupling the room and you are on the top floor do you think your neighbors below will feel the bass reverb

BTW if they can, don't be so sure that your F113's won't contribute as they are very powerful subs.

 

[brianherlihy]

we'll see Steve. i am hoping not, or that it will be minimized. it is a beam and post building, in other words, it is a brick building that is supported through the middle with old pine posts and beams. these post and beams, as well as the brick, cannot be decoupled floor to floor (obvious i guess) so the bass will travel down these structures. i am hoping not too much, the whole floor (3600 sq ft) is on a floating floor system that is decoupled (i.e. doesn't touch the walls or posts) with sound absorption into the floor. This was done to help the music as well as kids running around situation.

on the F113 - i hear you! i guess my neighbor will have to live with it to a certain degree - i didn't have to do any of the above work but did it at a high $$$ to help her situation.

 

[Steve williams]

Just make sure she likes music and invite her up often for a listen

 

[brianherlihy]

hahaha...good advice!

 

[RUR]

... i would like to get better educated on DRC as a matter of curiosity. My question then is what are the options? i am sure this is a loaded questions as there are many ways to go about it, but where do you start? i do have subs (2 x F113 JL Audio - coupled with on order Magico Q5's). but would i be looking at a digital cross over, an EQ, a system between line amp and monoblocks? maybe too broad a question, but am curious to get your guys input.

Brian, anything you might consider using with your gear will either replace your preamp or be inserted between preamp and monoblocks. Every full FR product I can think of will provide both variable crossover and DRC. Like everal other members, I use one of the TacT pre/pros, which provide up to full-range DRC and handle two subs, including delays. They're not particularly difficult to set up, though there are some non-obvious tricks to getting the best performance. Do be advised that it's a single measurement position device i.e. it optimizes for a single sweetspot. Its close cousins, made by Lyngdorf, do provide for multiple measurement positions, but have other tradeoffs as regards curve "tweakability" IIRC.

Speaking for myself, full-frequency DRC made a huge difference in soundstage coherence/instrument separation, even in my well-treated room. Don't think I can ever go back.

Ken

 

[Steve williams]

Speaking for myself, full-frequency DRC made a huge difference in soundstage coherence/instrument separation, even in my well-treated room. Don't think I can ever go back.

Ken

I would love to try TacT because I know for sure it would better help to integrate my subs into the system as well as DRC BUT based on everyone who knows TacT and who has heard my system tell me that indeed it will sound better BUT at the expense of the wonderful midrange and highs that the Lamm produces. I am not prepared to give that up

Suggestions anyone

 

[brianherlihy]

thanks Ken, i will be interested to hear about comments on Steve's question. i like the idea of an 'on-off' switch - pass-through option. i presume this means i would put DRC between my existing pre amp and monoblocks?

 

[RUR]

Suggestions anyone

You can but try it. Are any of our users near you, Steve? If I were driving up for BAAS, I'd schlep mine.

thanks Ken, i will be interested to hear about comments on Steve's question. i like the idea of an 'on-off' switch - pass-through option. i presume this means i would put DRC between my existing pre amp and monoblocks?

Brian, yes, there's a bypass button. You'd put the TacT unit between preamp and amps, which involves an additional A/D/A step or you replace your existing preamp with the TacT. Marty favors the former in his system, I favor the latter in mine. Easy enough to try both approaches, if you've got an analog preamp already.

 

[brianherlihy]

AUDIOGUY QUOTE -

That said, I have taken three different progressions, all of which improved the bass response. (1) added Audyssey Pro to my pre-pro and the bass became much tighter and better defined and the slam factor improved (2) I then added delay to the rear subs, utilizing a QSC DSP30 so that the time arrival matched the front speakers and the bass improved even further and (3) I finally added the Audyssey Bass EQ product (and removed the QSC DSP30 as the Audyssey Bass solution addressed the delay issue) which took the bass to a far more refined level with virtually no bass overhang/ringing. I have only heard bass like that in one other place (and that was in the room that needed no DRC!).

Hi Audioguy, do you have any experience with Audyssey vs. TacT