Poor man's room EQ.

[bodega.]

Hi all,

Just thought I'd share a little experiment I just finished whipping up.

The other day I bought the excellent and cheap ($10!!!) Strobe Tuner by Katsura software, which not only gives you the note name of the sound coming into your computer but also the exact frequency.

Using my modular synth as a frequency generator, I started doing sweeps of the audible spectrum and found that from 120-134Hz, centred at 127, there was a 7dB hump and from 49-64Hz, centred at 54 there was a 8.6dB dip in the response of this room. Big dips, obviously!

So, lacking a room eq before my monitors (Mackie HR824s), I whipped up an UAD-1 Cambridge EQ template in Cubase that has sharp curves to counter those dips.

Even though this is a slightly sloppy way to work, it means I can produce tracks with the EQ engaged on the main bus, then when I want to mix down, I can disable that and I'll have something ready for mass consumption.

Of course, ideally the EQ would come right before the speakers and I wouldn't have to disable anything, but there you go. As a temporary measure, I think it should work fairly well. There's really no more adjusting I can do to this room - it's essentially an oversized bedroom.

Just figured I'd throw that idea out there. Has anyone else done the same thing? Has it worked for you?

cheers,
Matthew

[Ethan Winer]

Matthew,

> ideally the EQ would come right before the speakers <

Ideally you'd treat your room with bass traps and other acoustic treatment.

Not to burst any bubbles, but EQ does not work for a variety of reasons. I expect half a dozen other slutz will be along soon to offer their opinions too. But in the mean time, the text below is from my Acoustics FAQ explaining some of the problems with trying to use an EQ to fix room acoustics.

--Ethan

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.

[bodega.]

Originally Posted by Ethan Winer

> ideally the EQ would come right before the speakers <

Ideally you'd treat your room with bass traps and other acoustic treatment.

I wasn't kidding when I said "There's really no more adjusting I can do to this room - it's essentially an oversized bedroom" - the only place to put a bass trap would be on top of my bed. So, not an option.

In this case I'm not fixing large cancellations - while 8.5dB is big, 25dB is truly ridiculous, I wouldn't try to fix that - and I'm adjusting for one place only: directly in front of the workstation.

There really is no substitute for a good, well-treated room - obviously - but barring any other solution, I don't see why a bit of room-treating EQ would be *worse*. The freq's where I've eq'd out the room curve certainly don't sound as "clean" as the surrounding freq ranges - this I'm very conscious of - but hearing the freqs slightly dirty must be better than not hearing them at all. And in any event, that's why the bypass switch was made, to compare both, so as to avoid surprises.

Just my $.02,
Matthew

[Ethan Winer]

Matthew,

> the only place to put a bass trap would be on top of my bed. <

The corners where the walls meet the ceiling are just as good as any other corners.

> I don't see why a bit of room-treating EQ would be *worse* <

If you ask the pros who have tried and rejected EQ, that's exactly what they'll tell you. Here's another way to look at the problem. The frequency response in an untreated room varies significantly over very small distances. So it's not possible even to get the response correct at both ears at the same time. And as soon as you turn your head even a small amount, any improvement is now a detriment because the EQ was adjusted for a different location.

Again, my point is not to be a buzz-kill. By all means try it and live with it for a while. In the mean time, if you have a chance to hear someone else's small room that has been treated well with bass traps, I promise that will be a very useful experience.

--Ethan

[bodega.]

Originally Posted by Ethan Winer

In the mean time, if you have a chance to hear someone else's small room that has been treated well with bass traps, I promise that will be a very useful experience.

Says the guy who sells the bass traps.

;)

But seriously, I do see your point. I'll give it a few weeks and see if, by the end, the slight sloppiness that I can hear now sounds unacceptable. If so, I'll look into some major room-related surgery.

Thanks for the replies, guys.

[gfx]

Theres a reason why Ethan sells bass traps.

He knows what hes talking about and besides its not in his interests to tell you buy something then to not have it work and for you to complain.

What Ethan has stated is absolutely correct.

If Room Eq worked then everyone would be using it.

It is used in live sound as a way to get more gain before feedback.

You cannot compensate in the Frequency domain events which happen in the time domain. If you dont understand that statement you really should be prepared to listen to good advice when its presented to you.

Ethan has told you the truth and the facts of the matter.

Ignore at your peril!

GFX

[Ethan Winer]

> If Room Eq worked then everyone would be using it. <

That one point is just as good as all those I made.