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Topic: PEQ and Room correction (Read 18095 times) previous topic - next topic
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PEQ and Room correction

What PEQ systems or bass correction systems do you guys use in your system and do you think it is necessary to achieve high-fidelity sound in the room?

Just to give you some background on my own room. I live in a flat, and I have acoustic treatment on the ceiling, rear wall and front wall. Absorption is 4" thick fiberglass with a 2" air gap spaced from the wall. My listening space is very long, but I'm sitting the short way, and I can't do anything about it. I'm sitting about half of a meter from the rear wall, so my listening space is very compromised for sound quality, but after installing the panels, the sound is very, very nice .... except for the bass. It sounds boomy and muddy. Just takes long to decay.

Now I've emailed a few acoustic companies who tell me that PEQ systems will not address bass decay in a room, and that I need to install thicker bass traps, and I can't afford to do this in my room as I just don't have the space. So the only alternative I have is to think about correcting the bass with some kind of bass correction. I don't want to use Audyssey because it corrects the full frequency range. I only want to address the bass range 125 hz or so and down.

What do you guys recommend as a comprehensive, powerful solution that can address bass issues in a room that doesn't cost the earth? Any suggestions that you think would work well would be appreciated. If you guys use anything that has worked for you, please let me know! Thanks.

PEQ and Room correction

Reply #1 –
Sorry, just to add, I only have one large couch, so I'm not trying to correct for multiple locations, if that helps at all.

PEQ and Room correction

Reply #3 –
I recommend Audiolense. It can easily fix your bass issues - they are trivial with digital room correction. Most users discover that they prefer full range correction. I have used Audiolense for some 5 years now and I will never go back to uncorrected sound.

Audiolense is commercial software, but there is a demo version that can give you an idea of what you can expect. There is also a satisfied-or-money-back period.

There are commercial alternatives like Acourate and Dirac that should be quite good too, but I have never tried those.

Finally there is the free DRC-fir, but you may need to be a computer expert to use it.

What they all have in common is a significant learning period. There are guides available on the net and the commercial companies all offer personal support and advice.

PEQ and Room correction

Reply #4 –
Quote from: sshd on
I recommend Audiolense. It can easily fix your bass issues - they are trivial with digital room correction. Most users discover that they prefer full range correction. I have used Audiolense for some 5 years now and I will never go back to uncorrected sound.

Audiolense is commercial software, but there is a demo version that can give you an idea of what you can expect. There is also a satisfied-or-money-back period.

There are commercial alternatives like Acourate and Dirac that should be quite good too, but I have never tried those.

Finally there is the free DRC-fir, but you may need to be a computer expert to use it.

What they all have in common is a significant learning period. There are guides available on the net and the commercial companies all offer personal support and advice.


Thank you for the suggestions! I've never heard of the Audiolense, but I have heard of Minidsp. I have no idea how that works, or if there is a steep learning curve to getting optimal results from it. So I have to connect to a notebook or PC to run the software, sort of like REW?

Have you heard of the Anti-mode correction products? I've heard OF them, but I've never seen one, or heard one in action, but it claims to correct issues in the frequency and time domain.

The nice thing I like about this is that apparently you just need to hold in a button and it does everything automatically. The only thing I don't like is that you can't see the before and after measured results.

PEQ and Room correction

Reply #5 –
IMO - The best starting point for learning about room treatment is RealTraps.com.    Of course they are trying to sell you stuff, but there is a lot of good information and Ethan Winer (one of RealTrap's founders) has an article about building your own bass traps on his personal website.    (There is also lots of other interesting reading about audio on his website.)

If you really want to get "serious" about this, you should probably start by getting a measurement microphone and some software to make some room measurements.    A acoustics expert would start by measuring and diagnosing the room, and of course making measurements afterwards to check & tweak the changes/improvements.  (As well as checking with real music.  ) 

Equalization can certainly help but it doesn't solve all of the problems...    Reflections create standing waves that result in bass build-up at at some frequencies and some room locations and (anti-nodes) reduction/cancellation at other frequencies & locations (nodes).  EQ can bring-down the bass where it builds-up, but at cancellation frequencies it takes an infinite amount of boost, and an infinite amount of power to overcome the cancellation.    Of course the cancellation isn't really complete, so it doesn't really take infinite power, but it can take an impractical amount of power and impractically large subwoofers.

By absorbing the otherwise reflected bass, bass traps will actually boost the bass at the cancellation/node frequencies while taming the build-up at anti-node frequencies.

You also cannot remove reverb, although reducing the ringing/resonating frequencies (with EQ) will reduce the build-up related to resonant frequencies and that will help the overall sound.     

Quote
My listening space is very long, but I'm sitting the short way, and I can't do anything about it. I'm sitting about half of a meter from the rear wall, so my listening space is very compromised for sound quality
When you walk around the room, are there places where it sounds better?  It sounds like your listening position is fixed, but can you move the speakers around?    It might be worth experimenting with speaker placement.  Just a couple of feet might make a difference.


Quote
...and I have acoustic treatment on the ceiling, rear wall and front wall. Absorption is 4" thick fiberglass with a 2" air gap spaced from the wall.
Do you think the acoustic treatment has made the room more boomy?    Maybe you are absorbing too much of the mid & high frequencies?    Maybe you'll get better results with fewer panels, or possibly replacing some of the absorption with diffusion.


BTW - Most of us don't have perfect rooms!    I don't have any acoustic treatment....

PEQ and Room correction

Reply #6 –
There's a reputable school of thought that says electronic "room correction'  should only be applied in the modal range (standing waves, 'bass'), where correction is relatively straighforward and predictable, not  the upper frequencies (above the 'transition' or Schroder frequency) , where you are dealing with direct and reflected sound.  Problems in the latter range are best dealt with using physical room treatment. 

And it's true that even digital EQ won't fix a big 'dip' in the modal range, for reason DVDdoug describes.  But sometimes that can be fixed by moving the subwoofer or  listening position, and/or adding subwoofers.

I use my AVR's Audyssey MultiXT32  DSP which unfortunately (because I would like the option of having modal-only) is full range correction.

PEQ and Room correction

Reply #7 –
Quote from: DVDdoug on
If you really want to get "serious" about this, you should probably start by getting a measurement microphone and some software to make some room measurements.    A acoustics expert would start by measuring and diagnosing the room, and of course making measurements afterwards to check & tweak the changes/improvements.  (As well as checking with real music.  )


My room is treated with GIK traps. While the room has not been measured, I've treated the early reflection points on the walls and ceiling at my sweet spot creating a 'reflection-free zone' as Ethan calls it. So I've adopted his approach and the difference the panels have made, especially treating the reflections off the ceiling reflection points has obviously dramatically improved the sound quality compared to what it was before. Before, it sounded like a jumbled mess.

Quote
b]Equalization can certainly help[/b] but it doesn't solve all of the problems...    Reflections create standing waves that result in bass build-up at at some frequencies and some room locations and (anti-nodes) reduction/cancellation at other frequencies & locations (nodes).  EQ can bring-down the bass where it builds-up, but at cancellation frequencies it takes an infinite amount of boost, and an infinite amount of power to overcome the cancellation.    Of course the cancellation isn't really complete, so it doesn't really take infinite power, but it can take an impractical amount of power and impractically large subwoofers.


I understand that EQ can't cure all problems, but I can't physically place more traps in my room unless I want it to look like a studio. My only course of action is to employ some digital correction at low frequencies, at least this is my reasoning.


Quote
When you walk around the room, are there places where it sounds better?  It sounds like your listening position is fixed, but can you move the speakers around?    It might be worth experimenting with speaker placement.  Just a couple of feet might make a difference.


Yes, moving around changes the bass, but it really only seems to affect the levels in-room. Not the decay, which is what I want to have addressed, as the physical treatment in my small room is just not sufficient for dealing with frequencies lower than 80 Hz.

Quote
Maybe you are absorbing too much of the mid & high frequencies?  Maybe you'll get better results with fewer panels, or possibly replacing some of the absorption with diffusion.


Unlikely, as I'm only covering about a 30% wall coverage. Remember, I'm only addressing the early reflections for my couch area. The bass has certainly improved over what it was, but I'm living in a flat, in a small space, and my back is close up against the rear wall, so I'm in a bit of a predicament. As far as diffusion goes, that won't work because I need a certain amount of distance for it to work effectively. As I said, I'm very close to the rear wall.

Quote
Most of us don't have perfect rooms!    I don't have any acoustic treatment....


Well I decided that in order to improve on my sound I should invest in some acoustic treatment panels so I did. While the sound isn't perfect, I'm very happy for the most part, except for the lower bass which my panels unfortunately just can't do too much about. So digital correction is my only option, hence my asking questions about it.

PEQ and Room correction

Reply #8 –
Quote
There's a reputable school of thought that says electronic "room correction' should only be applied in the modal range (standing waves, 'bass'), where correction is relatively straighforward and predictable, not the upper frequencies (above the 'transition' or Schroder frequency) , where you are dealing with direct and reflected sound. Problems in the latter range are best dealt with using physical room treatment.


That's what I've been told, so my thinking is to keep things simple - address the bass range, and only the bass range and not try to create more problems by treating other things.

Quote
And it's true that even digital EQ won't fix a big 'dip' in the modal range, for reason DVDdoug describes. But sometimes that can be fixed by moving the subwoofer or listening position, and/or adding subwoofers.


I don't think dips are a big deal. You probably will never notice if there are dips, but peaks are a different story. When the bass just sounds louder at some frequencies, and lingers on, that's a problem and one that I think impacts sound quality more than a few dips here and there that you won't miss, unless you measure for it.

PEQ and Room correction

Reply #10 –
Quote
I don't have any acoustic treatment....


Don't you think you should treat your room? You're missing out.

PEQ and Room correction

Reply #11 –
Quote from: Rich B on
Quote
There's a reputable school of thought that says electronic "room correction' should only be applied in the modal range (standing waves, 'bass'), where correction is relatively straighforward and predictable, not the upper frequencies (above the 'transition' or Schroder frequency) , where you are dealing with direct and reflected sound. Problems in the latter range are best dealt with using physical room treatment.


That's what I've been told, so my thinking is to keep things simple - address the bass range, and only the bass range and not try to create more problems by treating other things.



Keep  in mind that there is a reputable school of thought (Ethan disagrees with it, btw) that says 1st reflections aren't all bad.  See Floyd Toole's book for discussion and citations.


Quote
Quote
And it's true that even digital EQ won't fix a big 'dip' in the modal range, for reason DVDdoug describes. But sometimes that can be fixed by moving the subwoofer or listening position, and/or adding subwoofers.


I don't think dips are a big deal. You probably will never notice if there are dips, but peaks are a different story. When the bass just sounds louder at some frequencies, and lingers on, that's a problem and one that I think impacts sound quality more than a few dips here and there that you won't miss, unless you measure for it.




What makes you think you wouldn't  notice dips in bass response?  It really depends on how deep and broad they are, as well as where.  I certainly wouldn't dismiss them out of hand.

PEQ and Room correction

Reply #12 –
Quote from: Rich B on
... I have heard of Minidsp. I have no idea how that works, or if there is a steep learning curve to getting optimal results from it. So I have to connect to a notebook or PC to run the software, sort of like REW?

...


MiniDSP is just a DSP device (digital/analog-in-->(ADC)-->DSP-->(DAC)-->digital/analog out) which can be run even as standalone DSP so you don't necessarily need computer for other but to adjust the preferred EQ for it.

Not much to learn ... you could start by connecting computer to your Hi-Fi system, install some software that has support for DSP (For Windows: EqualizerAPO is a system wide DSP for Windows Vista/7/8 (command line processor + few GUI's available). VST world has much to offer so you could install say VSTHost + some suitable plug-ins listed at KVR database (asio4all driver is needed if no native ASIO available). For REW you need suitable microphone for measurements. Results got from REW can be used with MiniDSP and EqualizerAPO).

PEQ and Room correction

Reply #13 –
Quote from: krabapple on
Quote from: Rich B on
Quote
There's a reputable school of thought that says electronic "room correction' should only be applied in the modal range (standing waves, 'bass'), where correction is relatively straighforward and predictable, not the upper frequencies (above the 'transition' or Schroder frequency) , where you are dealing with direct and reflected sound. Problems in the latter range are best dealt with using physical room treatment.


That's what I've been told, so my thinking is to keep things simple - address the bass range, and only the bass range and not try to create more problems by treating other things.



Keep  in mind that there is a reputable school of thought (Ethan disagrees with it, btw) that says 1st reflections aren't all bad.  See Floyd Toole's book for discussion and citations.


I've heard of it. But in my small room, absorption was my only course of action. I'm not talking about treating all the walls, floor and ceiling, but just enough of it to bring the reverb down to manageable levels. I've been in rooms where the whole room has been treated with fiberglass and it sounded dreadful to me.

Quote
What makes you think you wouldn't  notice dips in bass response?  It really depends on how deep and broad they are.  I certainly wouldn't dismiss them out of hand.


Because the dips are not as noticeable to the ear. When there are peaks, it's hard to miss it. It sticks out like a sore thumb. If you had dips in your room, and you never measured your room, and you just listened to music, you probably wouldn't be able to AB it in a blind test.

PEQ and Room correction

Reply #14 –
The good thing about digital room correction (drc) is that is works very well with ordinary room threatment. The better the room and placement of speakers/listening position the better the result after drc. A good drc product will make any ordinary room with reasonable placement sound quite good.

Audiolense will correct frequencies, time and phase. It can even be used as a crossover/drc combo, which will time align the drivers as well. The latter is a major upgrade to any passive speaker, but requires modification and additional amplification.

Drc is a wonderful thing, but there is no easy way past the learning curve:

- You have to learn how to meassure your room with a microphone. This sounds quite easy, but you need a stable platform to place your microphone on. Then you need to listen to the room for things that play along. Glass that vibrates, lamps , loose screw in your speakers etc. You probably won't notice these when playing normal music, but they will show up when doing a frequency sweep.

- You need to find out how you like music to sound. Most commercial speakers comes with a bass hump. You can get this hump if you like or you can get perfectly flat sound. Flat sound may sound very strange/wrong at first. It is a major operation to determine your preference - took me 4 years.

PEQ and Room correction

Reply #15 –
You live in a "flat"? Across the pond are we?
Quote from: Rich B on
I only want to address the bass range 125 hz or so and down.
What do you guys recommend as a comprehensive, powerful solution that can address bass issues in a room that doesn't cost the earth? Any suggestions that you think would work well would be appreciated. If you guys use anything that has worked for you, please let me know! Thanks.

DIY first order gradient subwoofers. Or for you Rich, Dipoles and/or Cardioids  .
Inject 6db less power into the room to begin with. Do not maximally excite all modes at once, for them to all have to decay in time.
You already have monopole subs?

cheers,

AJ
Loudspeaker manufacturer

PEQ and Room correction

Reply #16 –
Quote
DIY first order gradient subwoofers. Or for you Rich, Dipoles and/or Cardioids smile.gif.


I have no DIY experience making subwoofers. Kind of an odd suggestion, don't you think?

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Inject 6db less power into the room to begin with. Do not maximally excite all modes at once, for them to all have to decay in time.


How about a digital correction system in the bass range?

Quote
You already have monopole subs?


Yes, I have *a* monopole sub, but then most subs on the market are monopole subs, aren't they?

PEQ and Room correction

Reply #17 –
Quote from: Rich B on
I have no DIY experience making subwoofers. Kind of an odd suggestion, don't you think?

As noted previously, I'm neither magician, seer or scryer. So I have no idea what your DIY experiences or capabilities are. I simply offered a solution to a problem, with the low cost stipulation.

Quote from: Rich B on
How about a digital correction system in the bass range?

Yes, that too. But not only by itself, which will be ineffective for ringing. Anything that is <500hz should be fine. The MiniDSP mentioned solution is quite cost effective.

Quote from: Rich B on
Yes, I have *a* monopole sub, but then most subs on the market are monopole subs, aren't they?

Yep, therein lies the problem. Works great for car audio boom, boom, boom, not so much at home eh?
You need more than one if you're going to stick with monopoles. 2 bare minimum, 3+ better yet, unless you're a big classical/acoustic music fan. Then it can  get dicey. If not, multi monopoles will at least get you smoother amplitude and less boom. Measuring capability will be essential, not "by ear" only.

cheers,

AJ

Loudspeaker manufacturer

PEQ and Room correction

Reply #18 –
Quote from: ajinfla on
As noted previously, I'm neither magician, seer or scryer. So I have no idea what your DIY experiences or capabilities are. I simply offered a solution to a problem, with the low cost stipulation.


Sorry, when I replied I was not in the best of moods.

Quote
Yes, that too. But not only by itself, which will be ineffective for ringing. Anything that is <500hz should be fine. The MiniDSP mentioned solution is quite cost effective.


I have several panels that are the equivalent of 4" thick OC 705 fiberglass (with a 2" air gap built into the panel) with a bonded membrane, and the panels are spaced off the walls by around 2". I have 4 panels behind me handling SBIR, and I have two panels behind the speakers, same design.

Two panels on the ceiling, with custom brackets that drop the panels 4". I really need to measure my room to know exactly what is going on, but given the thickness of the panels alone, I should be getting good absorption to at least 100 Hz.

The major problem areas that I can hear in my room are bass frequencies well below 100 Hz. As far as bass absorption, I think I think I've maximised what I can do in the room, given the compromised layout I have, so I'm hoping that active EQ will sort out any ringing issues I have at low frequencies.

Quote
Yep, therein lies the problem. Works great for car audio boom, boom, boom, not so much at home eh?


So its not possible to have one sub in the room with good results over a small listening area? I don't think it would be practical to add a second sub in my small space. I also have neighbors to consider. 

Quote
If not, multi monopoles will at least get you smoother amplitude and less boom. Measuring capability will be essential, not "by ear" only.


How do multiple subs give less boom? Wouldn't the decay remain the same, but the frequencies may be reduced, or 'filled' in? I've never heard of multiple subs reducing ringing before.

And wouldn't it be more cost effective to add active EQ to reduce frequency and ringing issues that bass traps and subs can't address? Or are you not a big fan of active EQ for low bass frequencies?

BTW, what acoustic treatment do you have, and do you employ any EQ in your room?

PEQ and Room correction

Reply #19 –
Quote from: Rich B on
I should be getting good absorption to at least 100 Hz.

Yes, which will accentuate you problems <100hz, further mangling the spectral imbalance. Unless the absorbers are covered with reflective and/or diffusive elements, you should also have about zero spaciousness/realism, but if that's what you prefer...
Btw, are you measuring, or is this all "specs" or "by ear"?

Quote from: Rich B on
The major problem areas that I can hear in my room are bass frequencies well below 100 Hz. As far as bass absorption, I think I think I've maximised what I can do in the room, given the compromised layout I have, so I'm hoping that active EQ will sort out any ringing issues I have at low frequencies.

EQ will lower the intensity of the peaks at the LP, thus the strength of the ringing at those peaks. That's it.
It won't fill holes, nor should attempt be made to do so with EQ.

Quote from: Rich B on
So its not possible to have one sub in the room with good results over a small listening area?

Sure, nearfield solves your modal issues (at the LP), but creates integration with mains issues...and mono bass issues...which may, or may not be an issue, for you/your tastes.

Quote from: Rich B on
I also have neighbors to consider.

Right. That's precisely why I suggested (DIY) 1st order gradients. Bass for you, without maximal modal excitement and around 6db less bass for your neighbors. But you don't DIY....

Quote from: Rich B on
How do multiple subs give less boom? Wouldn't the decay remain the same, but the frequencies may be reduced, or 'filled' in? I've never heard of multiple subs reducing ringing before.
And wouldn't it be more cost effective to add active EQ to reduce frequency and ringing issues that bass traps and subs can't address? Or are you not a big fan of active EQ for low bass frequencies?

Spatial averaging out the peaks/dips in pressure response, along with EQ. Smooth amplitude will sound less boomy. The only "ringing" you should be concerned with, is audible ringing. <50hz, should be largely benign. >50hz, yes, lossy walls help, but you're maxed out, so you may have to try just EQ and see if the improvement is sufficient. I am a fan of using as little active EQ as necessary. Only to "fix" listener room/speaker interaction issues, not speaker issues.

Quote from: Rich B on
BTW, what acoustic treatment do you have, and do you employ any EQ in your room?

Like every show I demonstrate at, for all the world to hear, including prospective customers, my room(s) are "treated" with furniture/furnishings.
Zero so called "room treatments". I go green. 
Yes, I will apply EQ <500hz if needed. I'm not against diffusion, especially on the rear wall, either.
Nor do I deny that ultimately, preference rules. I attend live acoustic performances at a local concert hall. That's the sound I prefer, so no iso-wards for me.  YMMV.

cheers,

AJ
Loudspeaker manufacturer

PEQ and Room correction

Reply #20 –
Quote
Unless the absorbers are covered with reflective and/or diffusive elements, you should also have about zero spaciousness/realism, but if that's what you prefer...


As I said, I'm not covering the entire wall surface with absorption, so it's not acoustically dead. I reckon about +- 30% of the wall coverage. I feel the sound is reasonably spacious and I've been in rooms that were lined with foam over the walls and ceiling and it sounded dreadful - just bass booming with a loss of high frequency energy.

Quote
Btw, are you measuring, or is this all "specs" or "by ear"?


I think I said earlier that I have not measured the room. But in terms of what 4" fiberglass can do directly on a wall with no air-gap:

http://www.bobgolds.com/AbsorptionCoefficients.htm

My panels have a built-in 2" air gap, a membrane on the front to reflect some of the higher frequencies back into the room, and the panel is further spaced away from the wall. So I don't think it is too much of a stretch to say that my panels are addressing reflections to at least 100 Hz.

I will be measuring my room in the near future. Just need to buy myself the UMIK so I can plug-and-play with REW.

Quote
Like every show I demonstrate at, for all the world to hear, including prospective customers, my room(s) are "treated" with furniture/furnishings.


What do you do? Are you an acoustics expert?

PEQ and Room correction

Reply #21 –
Quote from: Rich B on
I think I said earlier that I have not measured the room.
I will be measuring my room in the near future. Just need to buy myself the UMIK so I can plug-and-play with REW.

Sorry I missed that. UMIK w/REW should work nicely, but be careful interpreting the measurements. Btw, I moderate at HTShack, so I'll keep an eye out.

Quote from: Rich B on
What do you do? Are you an acoustics expert?

No, but I play one on TV.
I'm a loudspeaker manufacturer. 

cheers,

AJ
Loudspeaker manufacturer

PEQ and Room correction

Reply #22 –
Quote
No, but I play one on TV.
I'm a loudspeaker manufacturer.


So you build speakers? What speakers? And are they considered to be high fidelity?

PEQ and Room correction

Reply #23 –
Quote from: Rich B on
So you build speakers? What speakers?

Yes, as indicated in my Profile, Soundfield Audio. I don't sell subs. 

Quote from: Rich B on
And are they considered to be high fidelity?

I suppose that depends on who you ask and what their definition/interpretation of that term is.

When you acquire the UMIK, post your measurements here too. Should be interesting.

cheers,

AJ
Loudspeaker manufacturer

PEQ and Room correction

Reply #24 –
Quote from: ajinfla link=msg=0 date=
I suppose that depends on who you ask and what their definition/interpretation of that term is.


I thought there was a universally agreed on definition for high fidelity. So it's really subjective then? Then anything goes? I see Ethan sometimes throws the term around, but if no one really agrees on what it means or what criteria is required to meet that definition then it doesn't really mean anything.

Quote
When you acquire the UMIK, post your measurements here too. Should be interesting.


Thanks. Although I haven't decided whether I should go for the UMIK-1or the Dayton UMM-6. Do you have any preferences for one over the other? Is one better, or easier to use?

Thanks.