Room Treatment/Monitor EQ

[philbagg]

Ok, I'm gonna take a plunge here and try to deal with the bashings (go easy fellers ).

Some steps you take in treating your room are getting an omni mic and a room analyser and measuring the differences between the signal audio and the room sound right?

So let's say you have bumps at 40Hz, 80Hz, 160Hz etc. What are the problems in using an EQ with a really high Q on using your master bus and pulling down the offending frequencies by the amount given on your graph, in an attempt to even things out?

Now I know if you left this EQ on during the final mixdown, those frequencies would be lost on other systems. But, this is purely for a monitoring situation, so you'd bypass it on the final mixdown.

I'm just curious as to what you guys think about this.

 

[bouldersoundguy]

The eq processor should only affect your monitors. Using a hardware eq between your interface and your monitors seems simpler than trying to do it ITB. Digital units are more precise and consistent, and can have presets.

Try to address problems acoustically before resorting to signal processing. The sound will be improved all over the room rather than at just one spot. Once you've done all that's practical and affordable with acoustic treatment then you might finish up with some eq.

It's a bit more subtle than "an omni mic and an analyzer". An actual measurement mic would be preferable to any old omni. The problem with an RTA is that it can't distinguish direct from reflected sound. You need something that not only measures how much of each frequency but how long it took to get back to the mic. This will tell you much more about the room than an RTA.

A starter setup would be a Behringer measurement mic ($50), an interface with two inputs and outputs and REW. Get the latest non-beta version. What you do is feed one output back into one input while the second output goes through the system, out the speakers and into the mic. The software compares the two in a way that's more sophisticated than a simple RTA. It seems simple enough, but the setup and interpretation can be challenging.

 

[philbagg]

It's a bit more subtle than "an omni mic and an analyzer". An actual measurement mic would be preferable to any old omni. The problem with an RTA is that it can't distinguish direct from reflected sound. You need something that not only measures how much of each frequency but how long it took to get back to the mic. This will tell you much more about the room than an RTA.

Some steps you take in treating your room are getting an omni mic and a room analyser and measuring the differences between the signal audio and the room sound right?

I was thinking along the lines of REW or even SMAART (pfft, like I have that kinda money ) so I know that it compares the two.

Just wondering, why would you suggest hardware rather than software EQ for this type of thing?

 

[SouthSIDE Glen]

A couple of the difficulties in using EQ to combat problems in room acoustics:

1.) The room response, especially in a room with some real problems, can be a pretty complex curve. It would take more than four or five bands of parametric to smooth out many typical acoustic problems, especially when dealing with harmonics or with cancellations.

2.) When one has acoustic problems that create significant phase cancellations or even more simple bass nulls, even extreme EQ boost isn't going to help much at those canceled or nulled frequencies; i.e. you can't really boost what's not really there.

3.) Unless you're using a linear phase EQ - and sometimes even then - you're adding the distortions of the EQ itself to the monitoring chain.

But, by addressing the problem itself at the source - i.e. by taming the room and adjusting the monitoring setup physically within the room, all three of those problems can potentially be avoided (to more or less of a degree, depending upon the severity of the problems.)

And keep in mind, many room problems can be tamed without having to go out and buy or build actual bass traps and diffuser panels and such. Sometimes all you really need to do is move your mix desk, rearrange furniture, add a few cushions, replace blinds with drapes (or even just partially open some blinds and windows), etc. You may not wind up with The Record Plant control room, but it can often be at least enough to make your monitoring good enough to be nicely translatable.

G.

 

[philbagg]

A couple of the difficulties in using EQ to combat problems in room acoustics:

1.) The room response, especially in a room with some real problems, can be a pretty complex curve. It would take more than four or five bands of parametric to smooth out many typical acoustic problems, especially when dealing with harmonics or with cancellations.

2.) When one has acoustic problems that create significant phase cancellations or even more simple bass nulls, even extreme EQ boost isn't going to help much at those canceled or nulled frequencies; i.e. you can't really boost what's not really there.

3.) Unless you're using a linear phase EQ - and sometimes even then - you're adding the distortions of the EQ itself to the monitoring chain.

But, by addressing the problem itself at the source - i.e. by taming the room and adjusting the monitoring setup physically within the room, all three of those problems can potentially be avoided (to more or less of a degree, depending upon the severity of the problems.)

And keep in mind, many room problems can be tamed without having to go out and buy or build actual bass traps and diffuser panels and such. Sometimes all you really need to do is move your mix desk, rearrange furniture, add a few cushions, replace blinds with drapes (or even just partially open some blinds and windows), etc. You may not wind up with The Record Plant control room, but it can often be at least enough to make your monitoring good enough to be nicely translatable.

G.

Cheers Glen, always good advice

 

[kentheriot]

Heh. I tried that before. It's like trying to catch a greased pig (not that I've tried). Once you "fix" the problem frequencies, different problems seem to show up. You try to fix those too, and eventually everything sounds like doodoo. I think the reason for this is that different spots in the room where waves are crashing into each other, canceling each other or feeding off one another, cause rises and dips sometimes at the same frequency in a different spot! I suppose if you were able to bolt your head to the same spot in space, and correct just what was being lost or gained right there, it might work. But then there is the problem Glen talked about where no amount of EQ can correct a wave that has been totally canceled out. So...there's my 2 pence.

Jake

 

[miroslav]

It's like trying to catch a greased pig...

Yeah...that's a good analogy.

I was going to say it's like trying to guess what's on a woman's mind...and when you do...she changes it!

 

[Massive Master]

To go along with Glen, etc. --

EQ'ing the problems out of a room isn't going to happen. You can EQ the space to death to get rid of a problem that occurs at your left ear that isn't happening (or is twice as bad) at your right ear. Or a foot away. Or several inches higher or lower or off to the side.

If you want to EQ your monitors "for reasons of taste" that's one thing - But trying to EQ room issues out of a room isn't going to happen...

 

[bouldersoundguy]

Just wondering, why would you suggest hardware rather than software EQ for this type of thing?

Because then you don't ever have to remember to bypass it when bouncing/rendering your mix, and it doesn't mess with your metering or anything else having to do with you production process. Keep production and reproduction separate.

I basically agree with the warnings about using eq, that you can't expect it to be the main solution. Cancellation can be infinitely deep and no amount of filtering will bring it back. Fix as much acoustically as possible. Applying eq is okay to even out any response issues inherent to the speakers themselves and I've found it useful to deal with bass peaks at the sweet spot. The "room" eq you do for one position will not be correct away from that one spot, but bass corrections will work over an area large enough to include both ears.

 

[bouldersoundguy]

3.) Unless you're using a linear phase EQ - and sometimes even then - you're adding the distortions of the EQ itself to the monitoring chain.

Aren't speakers minimum phase devices? It seems at least possible that corrective eq (for the speaker, not the room) would also be corrective in terms of phase. But that's several notches above my level of knowledge.

 

[Ethan Winer]

Aren't speakers minimum phase devices?

Maybe, but the problems are caused by the room which is not so easily controlled. All the advice from Glenn and Massive applies. I've seen all sorts of technical gobbledygook that "proves" EQ can reduce peaks and ringing, but when actually tested they're all shown to be wrong:

Audyssey Report

Further, even if EQ could reduce peaks perfectly well around the room, which it can't, EQ cannot deal with nulls or ringing which are just as damaging as peaks.

--Ethan

 

[SouthSIDE Glen]

Aren't speakers minimum phase devices? It seems at least possible that corrective eq (for the speaker, not the room) would also be corrective in terms of phase. But that's several notches above my level of knowledge.

If I understand you correctly, there's a couple of different points brought up there.

First, you're right, many speakers nowadays are minimum phase devices. But as I understand it, they can't do much to correct phase issues already inherent in the signal, they are really designed not to introduce phase issues of their own.

I was referring to the basic concept of "keep the signal chain short". That is, non-linear phase equalizers can theoretically introduce their own phase vs. frequency issues, And since they are really inadequate at adequately solving many acoustic environment issues, the addition of such potential issues - and other potential self-noise from the EQ device itself - tends to null the advantage of using EQ in the monitoring chain just that much more.

And finally, when I was referring to phase cancellation problems, I was not referring to those caused by the loudspeakers themselves, but rather those caused by rogue room reflections. No EQ or speaker can really address those because they are inherent properties of the physical room configuration itself. Changing those properties through the use of diffusers/absorbers or even simple movement of the loudspeakers to better locations within the room (or any combo of the above) is th only sure way of dealing with that.

G.

 

[bouldersoundguy]

Well, I won't force it on anyone. I did start with the suggestion to do all one can with acoustic treatment before anything electronic when making the room usable. My experience is that mixes done after measurement and eq were easier to get right and more consistent on various systems. Maybe it's pure coincidence.

 

[SouthSIDE Glen]

Well, I won't force it on anyone. I did start with the suggestion to do all one can with acoustic treatment before anything electronic when making the room usable. My experience is that mixes done after measurement and eq were easier to get right and more consistent on various systems. Maybe it's pure coincidence.

I won't say that it is impossible for EQ on the monitoring chain to help some folks.

I liken it as being similar to the question of mixing in headphones; there are more than a handful of folks out there that can get along just fine mixing in headphones, though it's typically not something most of us would recommend as a preferred M.O. (not to bring that can o' subject up here, gang; there's another fairly current thread for that )

I just seems to me that if one needs EQ on the monitoring chain to get good mixes in reasonable time, there's probably something else fairly simple within the room setup that they missed. If all other bases have been covered as much as is reasonable for the situation, and if EQ an help at all as a last resort, then by all means, do it. But if someone sticks their mixing desk in a corner of a glorified closet, IMHO don't expect EQ to bail you out because it probably won't.

G.