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Compensating room acoustic by EQ Studio Monitors
Old 24th May 2006
  #1
Gear Maniac
 

Compensating room acoustic by EQ

Hello, are here anybody who using this technique? Record sound from your monitors, analyse it, make an inverse EQ curve and set the master equaliser with this setting... I'm thinking about this. Is it a good idea? EQ should be Algorhitmix LinearPhase EQ or something like this...
Old 24th May 2006
  #2
Gear Addict
 

Have you treated your room?

This is will make an enourmous and invaluable difference and is really cheap as if you put the effort in! Read about DIY and DON'T use foam.

If you've already treated your room, then maybe tweak the treatment to deal with the frequency issues you're having. Also placement of your monitors in the room and your position relative to the monitors... these are all things you need to get right before you start using eq.

Personally, I wouldn't use eq the way you've described - but I'm still a n00b so I'll let someone else chip in.

Rez
Old 24th May 2006
  #3
Gear Maniac
 

RainbowStorm> I meant mixing INTO this EQ, which is linear phase and high quality (no coloring)...
Old 24th May 2006
  #4
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Quote:
Originally Posted by siegfried
RainbowStorm> I meant mixing INTO this EQ, which is linear phase and high quality (no coloring)...
Sorry, I misunderstood it...

Here are some reasons why this is not a good approach:

- You will negatively compensate the track EQ/mic/pre-amp during the tracking process

- The mastering engineer will likely negatively compensate these EQ settings later

- To create room size you will negatively compensate reverb/delay effect wetness

- ITB it means additional errors with the EQ on the mix bus

- You are limited to a certain mix volume, which is unefficient

The sum of it all means a lot of lost signal.

The most efficient way of doing this is to get a great set of monitors and treat the control room so that the truth is reveiled. The best is of course when the recording room and the control room/monitors match well and when that is very accurate against the overall listening perspective.
Old 24th May 2006
  #5
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seaneldon's Avatar
 

no no no no no no no don't do that no no no no no no no
Old 24th May 2006
  #6
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Glenn Kuras's Avatar
Quote:
Originally Posted by seaneldon
no no no no no no no don't do that no no no no no no no

That is the best advice you will ever get.

Glenn
Old 24th May 2006
  #7
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Quote:
Originally Posted by myfipie
That is the best advice you will ever get.

Glenn
thanks. it's good to finally get some recognition.
Old 24th May 2006
  #8
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Not a great idea for a mix environment although it is done everyday to some extent in live and cinema environments. Yes I know different environments and different criteria of success. Live guys have to compensate for some very wild acoustic responses among other things. In cinema both mix and playback environments are tweaked via EQ. No matter how fabulously designed the mix stage is the room is EQ'd to that Dolby curve. While most theaters are acoustically designed and treated to varying degrees I'd love to see the theater where their eq racks are flat if they have them.

So how to do it before why not to do it. You're going to need some test equipment. GOOD test equipment. Rent it. 1 (or more) SDC measurement mic and an RTA are the down and dirty ways of doing it. Dolby uses 4 mics multiplexed across the mix position going into their own RTA with their curve painted across the display. You'll then need a good pink noise source either provided by the test equipment or if you're doing it guerilla your DAW. Keep in mind that the pink generated by various DAWS may only be a psuedo pink noise. It's best to either get some known pink audio files or make sure your test equipment provides it. Best is from the test equipment straight into your monitor system. Bring the vol of the pink up to your reference playback SPL then tweak away to as close to desired response. As for EQ's some good Weiss units would be ideal in this scenario but it looks like you are going in the box. If that's the case you will want to use pink noise audio files or a trusted software generator ITB. Forget what I said about an external generator.

Ok. now why you don't want to do this for a mix room. 1-your room response will vary according to SPL. You can EQ to one level but you probably will not listen at that level all the time. 2-you will be equalizing for one small point in the room. The same thing that affects mic placement applies to your head and the two things hanging on the sides of them. Moving (or angling) a mic even a little bit can change what is picked up (sometimes dramatically). Now unless you have your head in a vise at the tested and eq'd mix position you could be in for some serious weirdness possibly even to the point of seasickness. 3-Sort of related to point 1 is the fact that when you are getting sounds or tweaking individual sounds you may be fighting against the playback system EQ and the room. That's just too many variables to consider when you're say eq'ing a guitar track or tweaking vocal record path. You may be tweaking yourself in circles.

As everyone else will say fix the room not the system. Even if this is your living room/bedroom 1 room apartment some modest treatment will go a lot farther than EQ'ing your speakers. You don't have to go crazy with bass traps and diffusors. A small investment in buying or building some rigid fiberglass panels and improvised touches such as rugs and book cases can get you something that should be workable at low to moderate listening levels. The internet audio Dr. Spocks may give you a laundry list and science lesson on why you need a floated room and tuned absorbers but if you were in the position to do that you wouldn't be asking about EQ'ing your speakers. A very famous producer (think U2, Bob Dylan) known for gorgeous sounding records is a big fan of combined mix/tracking rooms and improvised recording locations with no more treament than carpets and furniture placements.

Good luck.

p.s. if you do go the EQ route remember to make very small adjustments. No big +/- 12db adjustments at one freq point. Better to use several tiny boosts and cuts to get where your going.
Old 24th May 2006
  #9
Gear Maniac
 

I will have small home project "studio", maybe in my living room, and 8" woofer...
Old 24th May 2006
  #10
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Ethan Winer's Avatar
 

Lightbulb

Siegfried,

> Record sound from your monitors, analyse it, make an inverse EQ curve and set the master equaliser with this setting. <

That doesn't work, even though it seems like it might. The text below is from my Acoustics FAQ. This is also why those new monitors that claim to be able to counter room acoustics using built-in EQ don't work either.

--Ethan

Quote:
Another common misconception is that equalization can be used to counter the effects of acoustic problems. But since every location in the room responds differently, no single EQ curve can give a flat response everywhere. Over a physical span of just a few inches the frequency response can vary significantly. Even if you aim to correct the response only where you sit, there's a bigger problem: It's impossible to counter very large cancellations. If acoustic interference causes a 25 dB dip at 60 Hz, adding that much boost with an equalizer to compensate will reduce the available volume (headroom) by the same amount. Such an extreme boost will increase low frequency distortion in the loudspeakers too. And at other room locations where 60 Hz is already too loud, applying EQ boost will make the problem much worse.

Even if EQ could successfully raise a null, the large high-Q boost needed will create electrical ringing at that frequency. Likewise, EQ cut to reduce a peak will not reduce the peak's acoustic ringing. EQ cannot always help at higher frequencies either. If a room has ringing tones that continue after the sound source stops, EQ might make the ringing a little softer but it will still be present. However, equalization can help a little to tame low frequency peaks (only) caused by natural room resonance, as opposed to peaks and nulls due to acoustic interference, if used in moderation.
Old 24th May 2006
  #11
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Quote:
Originally Posted by Ethan Winer
Siegfried,

> Record sound from your monitors, analyse it, make an inverse EQ curve and set the master equaliser with this setting. <

That doesn't work, even though it seems like it might. The text below is from my Acoustics FAQ. This is also why those new monitors that claim to be able to counter room acoustics using built-in EQ don't work either.

--Ethan
Very interesting stuff...
Old 24th May 2006
  #12
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Quote:
Originally Posted by Ethan Winer
Siegfried,

> Record sound from your monitors, analyse it, make an inverse EQ curve and set the master equaliser with this setting. <

That doesn't work, even though it seems like it might. The text below is from my Acoustics FAQ. This is also why those new monitors that claim to be able to counter room acoustics using built-in EQ don't work either.

--Ethan
Ethan, I'm currently thinking a little about the theories behind the "optimal" acoustic environment related to different music genres. A big part of acoustics is the "damp" factor. A very well treated acoustic room can sometimes sound good but be much too quiet for the kind of sound that is needed on the record. For instance in rock and country music a lot of the records are quite open, which is not possible if the room would be too damped. How should recording engineers deal with this effectively? Are there any ways of "changing" the acoustics to fit certain genres or should you choose a certain recording studio based on a certain genre and realise you can't really record both genres very effectively without additional processing?
Old 16th May 2007
  #13
TMI
Gear Head
 

Did everyone forget about the time domain?

In theater as well as live sound, the majority of the audience is beyond the "critical distance" where RTAs and 1/3 octave EQs actually work, somewhat. In studio monitoring, direct sound is dominant. The RTA integrates the direct sound and the room sound into a single reading. EQ adjustments made from this measurement upset the balance of the monitors in an attempt to correct room anomalies.

EQ should only be used to correct monitor problems.

Room treatments must be used to address room problems.

A LARS like, time domain correction system would be needed to address room problems electronically. You would also need the additional dynamic range to support the corrections. This can be a really big number that is cost and space prohibitive.

I have used inverse EQ corrections to recover recordings made with defective microphones. This actually works.

If you must have a reliable source of reference for EQ, get a pair of really good electrostatic headphones. I don't suggest you mix on cans mind you, but they do offer a reliable, consistent frequency and time domain response. EQs and even RTAs are totally valid for headphones but to be accurate, you'll need an ear coupler.

Mix on the speakers, then tweak the EQ on the cans or go for the room corrections.

Tom Maguire

tutt
Old 16th May 2007
  #14
Gear Nut
 

"In theater as well as live sound, the majority of the audience is beyond the "critical distance" where RTAs and 1/3 octave EQs actually work, somewhat."

I agree and dissagree with that statement. As far as I am concerned, the cinema IS a far-field environment (though Dolby will argue that point ad nauseum...), and as such, the process of using eqs and pink noise is futile b/c the issue is, in fact with the time domain. The same effects are seen near-field in the studio. This is why Ethan and everyone else who knows anything about acoustics frowns on the use of such tools for this purpose. Getting a short and even RT across the spectrum will yeild far better results than using an eq. Using an eq to correct room anomolies is like trying to remove a screw with a hammer. Wrong tool.
Old 16th May 2007
  #15
F5D
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I have a room with minimal threatment because I will move soon. No bass traps at all. I have to suck several decibels around 120Hz. Otherwise the sound is full of horrible boom and ringing. I use sony oxford eq for this. It's in the master bus all the time. I also route all system sounds thru logic that all sounds which I hear go thru the sony oxford eq. The problem comes from my new big workstation desk and that I have placed my BM15 monitors on top of the workstation's top racks. I will get primacoustic isoplane foams on friday. I hope they will help.

I wouldn't use an eq to boost any frequencies but it helps alot if you only attenuate some bass frequencies to reduce ringing. I wouldn't touch high frequencies at all with eq. They are easy to fix with already minimal acoustic threatment.
Old 16th May 2007
  #16
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Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by F5D View Post
I have a room with minimal threatment because I will move soon.
Is that like not buying monitor speakers or microphones because you'll move soon? heh

Quote:
I wouldn't use an eq to boost any frequencies but it helps alot if you only attenuate some frequencies to reduce ringing.
I agree it can help a little, but not a lot. Yes, the peaks are reduced, which is good, but the ringing (extended decay time) is not improved, and the flatter response is highly localized. Also, nulls are even more damaging than peaks in many rooms, and EQ cannot help that.

--Ethan
Old 16th May 2007
  #17
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Glenn Kuras's Avatar
IMO, the ringing is a MUCH bigger harm in a room and EQ does NOTHING for it. Do youself a real favor and just treat the room. EQing the room seems to be this "every 5 years lets try it" kind of thing that always ends up being the wrong thing to do.

Glenn
Old 16th May 2007
  #18
F5D
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F5D's Avatar
 

Quote:
Originally Posted by Ethan Winer View Post
Is that like not buying monitor speakers or microphones because you'll move soon? heh
heh In fact a better acoustic threatment is the next step which I will make. I have spent money more on gear lately. I will order some bass traps and other panels when I have moved to a new apartment.

Quote:
I agree it can help a little, but not a lot. Yes, the peaks are reduced, which is good, but the ringing (extended decay time) is not improved, and the flatter response is highly localized. Also, nulls are even more damaging than peaks in many rooms, and EQ cannot help that.

--Ethan
The eq is only a temporary fix for me. The sound is alot better if the eq is turned on and I can even listen to the monitors and do something but the 120hz attenuation doesn't fully fix the problem. It also seems like I also loose some information which is on that frequency. I will probably get separate monitor stands later... when I have moved. heh
Old 16th May 2007
  #19
TMI
Gear Head
 

What????

I can' resolve what you are trying to say at all.

There is a time domain component in everything. In the far field, there is substantial integration. Using EQ is at least semi-valid here, using RTA measurements. In a near field studio environment, the opposite is true and direct sound makes the greatest contribution. What you said makes no sense as I am reading it. A theater is as far from a nearfield control room situation as you can get. Far field is the only place RTA/EQ makes sense and is what it was originally developed for.

As a point of fact, I never recommend 1/3 octave EQ anywhere. I generally use my Ivie as a front end for FFT measurements. By extracting the direct sound component, a valid EQ for the early arrival sounds can be extrapolated. This is the only valid setting as far as I am concerned.

I completely agree that EQ is not for room anomalies and thought I said that clearly. In a stadium, MSG or similar venue, it is not as bad but correcting the acoustics is the way to go even there.

On the other hand, have you ever looked at a proposal for treating a place the size of Madison Square Garden?

Tom Maguire


Quote:
Originally Posted by Monsterlab View Post
"In theater as well as live sound, the majority of the audience is beyond the "critical distance" where RTAs and 1/3 octave EQs actually work, somewhat."

I agree and dissagree with that statement. As far as I am concerned, the cinema IS a far-field environment (though Dolby will argue that point ad nauseum...), and as such, the process of using eqs and pink noise is futile b/c the issue is, in fact with the time domain. The same effects are seen near-field in the studio. This is why Ethan and everyone else who knows anything about acoustics frowns on the use of such tools for this purpose. Getting a short and even RT across the spectrum will yeild far better results than using an eq. Using an eq to correct room anomolies is like trying to remove a screw with a hammer. Wrong tool.
Old 16th May 2007
  #20
TMI
Gear Head
 

120hz and BM 15s

This is likely a boundry issue. I've seen it with BM 15s before. I really think they should be flush mounted in the front wall.

Tom Maguire


Quote:
Originally Posted by F5D View Post
I have a room with minimal threatment because I will move soon. No bass traps at all. I have to suck several decibels around 120Hz. Otherwise the sound is full of horrible boom and ringing. I use sony oxford eq for this. It's in the master bus all the time. I also route all system sounds thru logic that all sounds which I hear go thru the sony oxford eq. The problem comes from my new big workstation desk and that I have placed my BM15 monitors on top of the workstation's top racks. I will get primacoustic isoplane foams on friday. I hope they will help.

I wouldn't use an eq to boost any frequencies but it helps alot if you only attenuate some bass frequencies to reduce ringing. I wouldn't touch high frequencies at all with eq. They are easy to fix with already minimal acoustic threatment.
Old 16th May 2007
  #21
Gear Nut
 

Tom, I was agreeing with you, I thought.

"In theater as well as live sound, the majority of the audience is beyond the "critical distance" where RTAs and 1/3 octave EQs actually work, somewhat. In studio monitoring, direct sound is dominant. The RTA integrates the direct sound and the room sound into a single reading. EQ adjustments made from this measurement upset the balance of the monitors in an attempt to correct room anomalies."

I used Cinema as an example, as that is my main area of expertise. Near-field and far-field can never be completely separated, which is why I used the word 'futile' to describe the use of eqs in this manner, even in the control room (why build anechoic chambers, then?). Perhaps I should have said something like 'mostly futile.' Real-world application (as in your Madison Square Garden example) dictate otherwise. As you said, electronic time-domain correction is available, cost-prohibitive in most cases, so we correct in the frequency domain to minimize these issues, or we employ methods that actually acoustically correct the RT issues. To clarify, I guess I was saying that eqs do not work at all to correct the issues, regardless of where in the field you place yourself. They are a band-aid that can be used to minimize the symptoms of the underlying issues.
Old 16th May 2007
  #22
Gear Nut
 

ahh - just re-read my post - I can see where you take issue with my statements - they are a bit contradictory. I should have clarified that the RTA, multiplexed or not can't distinguish between direct or indirect sounds. For that reason I don't think steady-state measurements are the best way to go in terms of separating room issues from speaker issues. RTA's can't separate time-domain anomalies from frequency domain issues. Nearfield or far. Sorry. Bit scattered today.
Old 16th May 2007
  #23
F5D
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Quote:
Originally Posted by TMI View Post
This is likely a boundry issue. I've seen it with BM 15s before. I really think they should be flush mounted in the front wall.

Tom Maguire
In fact I earlier used monitor stands for my bm15's and the boost at around 120hz wasn't too big but still audible. The problem became 3 times worse when I put the monitors on my new workstation. Now I have to attenuate almost 9dB compared to earlier 3dB. However, I sold the stands before my new workstation arrived so I didn't know that the problem would become worse. I will purchase new monitor stands and some acoustic threatment stuff after I've moved.
Old 17th May 2007
  #24
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T_R_S's Avatar
If you a have a phase cancellation in your room of say 45dB at say 2K, How are you going to fix that with an EQ?
Old 17th May 2007
  #25
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octatonic's Avatar
... is the recording studio equivalent of using leaches as a medical cure.
Old 17th May 2007
  #26
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swankdoc's Avatar
 

How about using a bus para EQ to make corrections to what Im hearing in my mixing room when compared to reference CDs?
ie matching my EQ curves to various reference CDs in my mixing space.
Seem to work OK for me. OF course Im doing 90% of the EQ tweeks on the indivual tracks, and just small tweeks on the bus EQ.

One thing Ive not done is to compare reference CD corrections to a series of white noise corrections. That would be intresting.
Old 17th May 2007
  #27
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Quote:
Originally Posted by T_R_S View Post
If you a have a phase cancellation in your room of say 45dB at say 2K, How are you going to fix that with an EQ?
3 EQs in series, each with 15db boosts at 2k. Believe it or not it sounds great
I did that once at a session with......now...who was that again?
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