How linear should a room be?

[peder]

Hello there

i have recently with some help from this page (and realtraps.com) and a SPL meter started to move things around in my studio (not the booth, but where i sit and mix and work)

and i'm wondering how "linear" (not sure if thats what its called in english)
should my room be.. meaning how large can the peaks be on the graph that I make from all my metering..

hope you understand what i mean and can help :)

.peder

[Weasel9992]

+/- 3dB is considered "flat" by today's standards. A bad room could have a 30dB or greater difference between peaks and nulls. Have you taken any measurements yet? Any idea where you're at?

Frank

[peder]

as i remember i did pretty good after moving around a little bit..

i think around 85db (plus/minus 5 db) :)

[Weasel9992]

What you need to know is the number indicating the difference between the biggest peak and the lowest valley in a particular part of the spectrum. So, you might have a big 98dB peak at 100Hz, then a 70dB valley at 140Hz, for a difference of 28dB. Any measurements like that?

Frank

[peder]

hello again frank

thanks for helping..
this is a (poor) photo i took of the graph

the high is 94db
and the low is 78db

before i moved my basstrap around i had a massive peak around 70-80, but i think it looks decent now. what do you think????

i dont have a subwoofer and my speakers dont really play under 40khz (adam A7) so there's no curve under that..

.peder

(myspace.com/djpeder)

[Weasel9992]

That's still pretty rough man...you've got a big null at 70Hz followed by a huge peak at 120Hz...20dB difference. Where do you have your treatment positioned now? How are you situated in your room? What are the dimensions of the room?

Frank

[peder]

i'll try to sketch it out and post it for you ..

have to figure out how to do that though :)

[peder]

allright here's a photo - hope you can make some sense of it..

size of the room is around 3.5meters x 4 meters

the wall (the grey one) is carpet..
the side wall (the white one) is painted and fairly thin..

on the left side is 2 big windows..
the back wall (the one where the photographer is standing) is some sort of basstrap (haven't tested it yet so know sure what it does)

any ideas what i can do so far or do you need af photo of something else????

thanks for pitching in :)

[avare]

Is your measurement mic in the middle vertically? this would cause the 70 Hz dip. Modal or LBIR (Listener Boundary Interference Region, which I just made up) effects.

Andre

[jwl]

That response graph is fairly typical for a small room -- actually it looks pretty good, as if it's been smoothed out some, because of the test procedure.

I recommend using a measurement program, something like Room EQ Wizard or ETF. This will give you more detail.

But even after testing, for small studios the solution is always the same: add bass traps to flatten the room response.

[Weasel9992]

Originally Posted by jwl

That response graph is fairly typical for a small room -- actually it looks pretty good, as if it's been smoothed out some, because of the test procedure.

Well, let's call a spade a spade...while that reading maybe typical, it's still pretty bad in the low end. It's definitely smoother up higher, which is predictable given his treatment arrangement. I will agree with jwl though that the cure for that illness is more bass trapping.

The question is, how are your mixes translating? Are they coming out thin on other systems? How's your imaging? Are you heavier on the right or the left?

Frank

[peder]

i have just started "fixing" the room and i feel that my mixes come out way better than before but haven't really tested this out yet...

i have done the graph and test with a spl meter (a pro one) i put it on the table right about where my ears are :)

any suggestions what kind of bass trap to work on for my back wall???

i'll take a photo of the one i have and maybe it can work better some how...

thanks a lot for your input :)

[Weasel9992]

Originally Posted by peder

i have just started "fixing" the room and i feel that my mixes come out way better than before but haven't really tested this out yet...

i have done the graph and test with a spl meter (a pro one) i put it on the table right about where my ears are :)

any suggestions what kind of bass trap to work on for my back wall???

i'll take a photo of the one i have and maybe it can work better some how...

thanks a lot for your input :)

4" or 6"...either one would be fine. You said in an earlier post that you had some sort of bass trap on the back wall..?

Frank

[peder]

here's some photos of the alleged basstrap :)

its not attached to the wall and some of the back has "rockfon" attached..

any idea what i could with that to help my room out????

thanks

.peder

[Weasel9992]

Yeah...that's not doing much back there. The front isn't nearly porous enough, and even if it was, it doesn't have rigid fiberglass behind it. It's basically just another wall. I'd just dismantle it...maybe use the frame for a thicker absorber with more insulating material. You need either 4" or 6" panels on the back wall.

Frank

[peder]

Originally Posted by avare

Is your measurement mic in the middle vertically? this would cause the 70 Hz dip. Modal or LBIR (Listener Boundary Interference Region, which I just made up) effects.

Andre

hello andre

could you please elaborate..
how should i hold the mic..
i have put it on the table in front of me .. the mic i pointing towards the ceiling..
should it point towards the speakers???
as i write this i start to think i might have a kind of stupid question on my hands, but please answer anyhoo

.peder

[Ethan Winer]

Using a small diaphragm omni, point it up. Do not have a table under it as that causes comb filtering from reflections. Best is an upright stand. Pull your chair back and put the stand so the top of the microphone is about where your head would be. But also move the mike around within a 12-inch area too, just so you can see how the response changes.

--Ethan

[peder]

i use a proffesional SPL meter i borrowed, i guess its a small omni..

when you say point it up, what do you mean??

shouldn't it point towards the speakers???

[Ethan Winer]

An omni microphone is, well, omni. So in theory it shouldn't matter. But no microphone is perfect, especially at higher frequencies where the capsule and body dimensions are similar to the wavelengths being captured. So pointing up is better when measuring two or more speakers with the same microphone placement because the body won't cast different "shadows" for sounds arriving from different directions. When it's pointing up, and assuming all tweeters are at the same height, sound from all angles strikes the capsule equally.

--Ethan

[peder]

hello everyone again..

i have now treated the 2 corners with deeper basstraps (i guess around 4 inches)

the graph now has a dip at around 80 and goes up around 120 ..

any ideas what kind af basstrapping or diffusion i need for that ..

the back wall has nothing (only a basstrap in the corner)

.peder

[Weasel9992]

Originally Posted by peder

hello everyone again..

i have now treated the 2 corners with deeper basstraps (i guess around 4 inches)

the graph now has a dip at around 80 and goes up around 120 ..

any ideas what kind af basstrapping or diffusion i need for that ..

the back wall has nothing (only a basstrap in the corner)

.peder

Regular old 4" or 6" bass traps on the back wall is what I'd do next. Some of your deepest nulls and highest peaks will come off an untreated back wall.

Frank

[peder]

allright sounds good..

i have the materials tp make one .. would you place in the same height as the speakers???