Room Correction for 2 Channel?

josh358 · Feb 2, 2012

ironmine said:
Thanks for advice! Do these mics require some additional equipment (such as microphone amplifiers, etc.?) And, if yes, wouldn't it be easier buy a simple USB microphone - such as MXL Studio 24 USB ?
which can be connected directly to a PC ??

Cardioid mics are better for recording than for room measurements. Also, you need a microphone that's individually calibrated, or you need to have someone calibrate it. The Behringer requires a mic pre with phantom power, I assume the Dayton does as well.

It's also possible to make a super-cheap mic with the Panasonic mic capsule that is I think used in these inexpensive measurement mics, if you do a search you can find some how-to's. But with a calibrated Dayton being so cheap, I think it's a much better deal.

DonH50 · Feb 2, 2012

The mics Bruce listed are measurement mics, designed to have flat frequency response over a wide range of frequency and dynamics, much more so than a typical recording mic. They require a preamp with phantom power and ideally with high gain, flat response, and low noise.

I have an earthworks M-30 now; still sorry I sold my old Sennheiser (or B&K, been so long I have forgotten).

audioguy · Feb 2, 2012

Bruce B said:
The only way to get rid of null is either move your seating position or build a new room.

Or .... my null (about 12 db between 100 and 300) was caused by the floor/ceiling interaction (as easily shown by moving the measuring mic around and got huge changes when moving vertical). I suspended bass traps from the ceiling and ....no more null. So now there are three choices :b

NorthStar · Feb 2, 2012

Wow Bruce, some of those mics are quite expensive!

Bruce B · Feb 2, 2012

LordoftheRingsEE said:
Wow Bruce, some of those mics are quite expensive!

Yeah, this befuddles me.... people spend thousands or even hundreds of thousands on equipment, but when it comes to room acoustics/analysis, people balk. Room acoustics are the biggest bang for the buck out there.

People can get a Josephson C550H, an M-Audio Pro Track and the free software Room EQ Wizard and you'd have an awesome setup for under $600

NorthStar · Feb 2, 2012

Excellent point Bruce, and very well 'microphoned' (recorded, registered, taken). :b

josh358 · Feb 3, 2012

I think for many without dedicated listening rooms, WAF precludes acoustic treatment. I'm not sure why people won't measure, though. They'll spend hours tube rolling or what have you. Maybe they just find it intimidating.

audioguy · Feb 3, 2012

josh358 said:
I think for many without dedicated listening rooms, WAF precludes acoustic treatment. I'm not sure why people won't measure, though. They'll spend hours tube rolling or what have you. Maybe they just find it intimidating.

When I tired to use REW, I had all kinds of issues (and I was using a very expensive mic). I just couldn't get REW to work consistently (my issues, not REW issues) . But with products like OmniMic, there is no excuse to not use measuring tools. For $250, you get a calibrated mic and software that virtually anyone can use.

I agree with Bruce and others. You can have a multi-hundred thousand dollar system, but without measuring tools, some form of room treatment and an investment of time, you will never get the maximum out of your investment.

And while WAF is critical in a non-dedicated space, there are even solutions for that. GIK (and others) make acoustic panels that double as artwork (or maybe it's the other way around)

http://www.gikacoustics.com/images/art_panel_300.jpg

josh358 · Feb 3, 2012

I agree too, acoustical treatment is critical if you want the best results. Unfortunately while those decorative panels are better than nothing many guys have a struggle just to get a couple of speakers in the room. For (most) women, appearance seems to come first, unless it's something that's important to them -- which, it seems, is anything in the world that doesn't have knobs on it.

I think you're right too that measurement requires something more turnkey than REW. I've never used Omnimic. Does it provide guidance about what to do with the measurements once people have them? At this point, I think most audiophiles either have to be willing to read something about acoustics, or hire a consultant. Or maybe go to the forums and ask for advice. The level of knowledge seems to be along the lines of "put some tube traps in the corners," and that's actually on the advanced side. A lot of people seem to think that you can achieve diffusion with books, don't understand that household materials won't absorb low frequencies, etc. Yet these same people can tell you that the KT-88's made in Slovenia in 1968 are less microphonic than the ones that were made in Serbia.

audioguy · Feb 3, 2012

josh358 said:
I agree too, acoustical treatment is critical if you want the best results. Unfortunately while those decorative panels are better than nothing many guys have a struggle just to get a couple of speakers in the room. For (most) women, appearance seems to come first, unless it's something that's important to them -- which, it seems, is anything in the world that doesn't have knobs on it.

That may be the most insightful comment I have ever read on the typical spouse response to high end audio :b

At this point, I think most audiophiles either have to be willing to read something about acoustics, or hire a consultant. Or maybe go to the forums and ask for advice. The level of knowledge seems to be along the lines of "put some tube traps in the corners," and that's actually on the advanced side. A lot of people seem to think that you can achieve diffusion with books, don't understand that household materials won't absorb low frequencies, etc. Yet these same people can tell you that the KT-88's made in Slovenia in 1968 are less microphonic than the ones that were made in Serbia.

So true.

As to the issue of treating a room: There is a HUGE amount of information available on forums like this, AVS, the web sites of companies like RealTraps, GIK, etc. And the Master Handbook of Acoustics is a great tool. If one is so inclined and willing to learn and ask questions and more questions, they can accomplish a LOT without hiring an outside consultant. I am not slamming outside consultants and IF you can find a REALLY good one, they can be quite helpful. But for some situations, one can make great sonic improvements if one is willing to invest some time and energy.

mojave · Feb 3, 2012

Bruce, thanks for the mic chart.

For those interested in a mic, the Behringer and Dayton mics are available calibrated from 5Hz-25kHz from Cross-Spectrum Labs. A premium calibrated Dayton mic is $85 and includes polar response, sensitivity, noise floor, frequency response, and a mini-CD with the data.

josh358 · Feb 3, 2012

audioguy said:
There is a HUGE amount of information available on forums like this, AVS, the web sites of companies like RealTraps, GIK, etc. And the Master Handbook of Acoustics is a great tool. If one is so inclined and willing to learn and ask questions and more questions, they can accomplish a LOT without hiring an outside consultant. I am not slamming outside consultants and IF you can find a REALLY good one, they can be quite helpful. But for some situations, one can make great sonic improvements if one is willing to invest some time and energy.

Agree completely. I've noticed though that when I recommend a book, most people don't read it. :-| They do seem to appreciate tips, e.g., try a diffuser here, etc. But few seem to want to learn enough to make full use of the available tools, or maybe it wouldn't matter anyway because of the WAF problem.

NorthStar · Feb 4, 2012

The best recommendations are the ones we are willing to practice ourselves.

* I am recommending that you read this thread right here. :b

** I am recommending that you listen to Jazz as a soul relaxer. :b

igufi · Feb 5, 2012

LordoftheRingsEE said:
I see ...

* I guess we'll have to wait till next Summer before we finally find out about the new Multichannel pre/pro from Emotiva, the XMC-1, with integrated TacT Correction & EQ System (RCS flavor; but I'm not sure if it is the 2.2XP version, or perhaps an even more improved version).

Here: http://emotiva.com/xmc1/spec_sheet.pdf

And the main thread from over at the Emotiva Lounge:
http://emotivalounge.proboards.com/index.cgi?action=display&board=updates&thread=22367&page=1#364886

And finally the Podcast: http://emotiva.com/podcasts/012712/EmoCastMix.mp3
{Taken from here: http://emotiva.com/news/ }

The spec sheet does state the TacT version being "TCS 3e Dynamic Room Correction", so it should be the mkIII of Theater System Control-series?

NorthStar · Feb 5, 2012

I'm not sure, as this is totally new for TacT and Emotiva
to join forces together in this new alliance partnership.

It is mentioned some places about RCS, but our guess is that it is:
TacT Multichannel (7.2) Room Correction System.

* I did ask Emotiva more precise details regarding TacT implementation
in the XMC-1, plus other things like DACs (how many of them), etc.,
but they are not responding to our questions just right now.

Cheers,
Bob

P.S. TCS mkIII makes a lot of sense. :b
{Theater Control System.}

ironmine · Feb 6, 2012

FrantzM said:
Iron (you don't mind me shortening your name?)

I am not (yet) entirely convinced by DRC for reasons I will post on later but would like to understand what you're curently doing with Foobar and you PC .. Very interesting..

Frantz,

I just placed a microphone in my sweet spot and measured first the "left channel+sub" using Room EQ Wizard, then for the "right channel+sub", separately. For each channel I did a total of 5 measurements - in the initial strictly central position of the mic, then moving it 5 cm to the right, 5 cm to the left, 5 cm to the front and 5 cm to the rear. I used for each channel the results averaged from these 5 locations. The measurements were done with sweep tones from 15 Hz to 250 Hz.

Thus, I got two measurement files, which showed to me the problematic areas. REW offers filters (settings for different EQ types) to counteract the resonances, but you can adjust them manually, if you wish. Then you export filter impulse responses to wav files. After than you can upload them to any convolver which you use in Foobar, or you can program your favorite equalizer instead (REW shows how to do it).

When Foobar plays, room correction happens "on the fly".

I do not aim to correct anything above 250 Hz. Even in the range below 250 Hz, I apply filters which do not fully eliminate the resonances (the resulting sound would be too sterile and boring), they just bring them 4-8 dB down and usually it is enough.

Initially, I wanted to have only "passive" room correction, and I built 7 DIY bass traps (10-15 cm, made of rock wool) and 2 5-cm side panels and 2 10-cm SBIR panels and 2 5-cm ceiling clouds. But, much to my reget, they turned out not to be enough for bass problems (even though they fixed nicely other acoustic issues). And so, I had to study and implement the above described "active" DRC. I am quite pleased with this "active+passive" combination, so far. Of course, as an audiophile, I always want even better sound, so I gravitated to this forum

I have an idea that cannot leave my mind already for quite a while. Do you think that we should try to measure/correct each channel separately, or perhaps the better approach would be to try and measure/correct mid/side channels? The thinking is that music always plays through 2 channels simulateneously...

edorr · Feb 6, 2012

ironmine said:
Frantz,

I just placed a microphone in my sweet spot and measured first the "left channel+sub" using Room EQ Wizard, then for the "right channel+sub", separately. For each channel I did a total of 5 measurements - in the initial strictly central position of the mic, then moving it 5 cm to the right, 5 cm to the left, 5 cm to the front and 5 cm to the rear. I used for each channel the results averaged from these 5 locations. The measurements were done with sweep tones from 15 Hz to 250 Hz.

Thus, I got two measurement files, which showed to me the problematic areas. REW offers filters (settings for different EQ types) to counteract the resonances, but you can adjust them manually, if you wish. Then you export filter impulse responses to wav files. After than you can upload them to any convolver which you use in Foobar, or you can program your favorite equalizer instead (REW shows how to do it).

When Foobar plays, room correction happens "on the fly".

I do not aim to correct anything above 250 Hz. Even in the range below 250 Hz, I apply filters which do not fully eliminate the resonances (the resulting sound would be too sterile and boring), they just bring them 4-8 dB down and usually it is enough.

Initially, I wanted to have only "passive" room correction, and I built 7 DIY bass traps (10-15 cm, made of rock wool) and 2 5-cm side panels and 2 10-cm SBIR panels and 2 5-cm ceiling clouds. But, much to my reget, they turned out not to be enough for bass problems (even though they fixed nicely other acoustic issues). And so, I had to study and implement the above described "active" DRC. I am quite pleased with this "active+passive" combination, so far. Of course, as an audiophile, I always want even better sound, so I gravitated to this forum

I have an idea that cannot leave my mind already for quite a while. Do you think that we should try to measure/correct each channel separately, or perhaps the better approach would be to try and measure/correct mid/side channels? The thinking is that music always plays through 2 channels simulateneously...

You can do the same using Amarra's build in equalizer on a Mac. However this equalizer works in stereo only.

josh358 · Feb 6, 2012

ironmine said:
I have an idea that cannot leave my mind already for quite a while. Do you think that we should try to measure/correct each channel separately, or perhaps the better approach would be to try and measure/correct mid/side channels? The thinking is that music always plays through 2 channels simulateneously...

Because of interference between the speakers, you'll get frequency combing if you try to measure more than one channel simultaneously. Since this is highly dependent on the position of the listener and even where a sound is panned, and since it apparently doesn't occur in quite the same way with a human head present as with a microphone -- and since different channels have different response aberrations -- I think it makes more sense to measure the channels one at a time. It also differs between the ears thanks to interaural crosstalk, which isn't necessarily a bad thing since the brain tends to reject response aberrations that differ between the ears (or interpret them as spatial information -- HRTF effects and combing from room surfaces).

One of the advantages of surround is that it minimizes combing, particularly in the all-important center channel.

audioguy · Feb 8, 2012

I just learned that I am a Beta Tester for DiracLive software. I will be running it in my Music Server PC. If this works the way I hope it will, no more TacT 2.2XP.

RBFC · Feb 8, 2012

I am definitely paying attention to this one. Please let us know when you've had a chance to run it through its paces. Will it be available for Mac?

Lee

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