How do I test for room treatment ?

[twostone]

I was scanning thru the different post and seen a post about room acoustics. What I was wondering how do you measure the room acoustics I have free shareware for testing and what am I testing for or should I say what is the flat freqz. I'm testing for. I'll be using Audio test bench. I'll be testing a room 13.5X10.5 with 10' ceilings also has a 4X5 window in center of room any and all suggestions welcome, thanks.

[bubbagump]

Well, the most basic way is to use a measurement microphone. You can either use a Real Time Analyzer or record pink noise played into the room and then use your software to see where your peaks and valleys are. You usually want to place your measurement mic at the place you will be listening at as you will get different readings at different parts of the room. Of course you want to have a reading and treat for the place you will be listening.

[twostone]

I know about the test mic. I have a Behr. test mic but WTF am I measuring with a pink noise I don't understand the readings I have all peaks no valley WTF this mean I'm getting is their a reference chart for flat frqz. I'm confused.

[rayc]

Go to the RealTraps site & download their free graph & sound source - it works well. You'll need to borrow or buy a SPL meter - they're pretty cheap though.
You save the download to a cd. play the CD in the room with the SPL at ear height in the listening/mastering position & record the SPL on the accompanying graph. This'll show you where you have peaks & throughs in specific frequencies which you can then address with bass traps etc etc etc.

[twostone]

Thanks rayc you da man, I appreciate the web link, reaally helped me out.

[fraserhutch]

Originally Posted by rayc

Go to the RealTraps site & download their free graph & sound source - it works well. You'll need to borrow or buy a SPL meter - they're pretty cheap though.
You save the download to a cd. play the CD in the room with the SPL at ear height in the listening/mastering position & record the SPL on the accompanying graph. This'll show you where you have peaks & throughs in specific frequencies which you can then address with bass traps etc etc etc.

Speaking of SPL meters, anyone got a good recommendation on an accurate one?

[c7sus]

Stand in the middle of your room and clap your hands.

Hear that quick echo???

It's called slap. You don't want that in your mics.

That's the most simple test of all.

Does your mix have LESS BASS on other systems??? Like your car, a stereo, etc.

That's the result of bass buildup.

the fix for that is treating the corners of your room with rigid fiberglass soundboard.

Every room has resonant frequencies. It's a physics thing. The idea is to minimize those resonant frequencies, knock them back into line with the rest of the spectrum.

Check out John Sayers' site and Ethan Winer for a couple different takes on how to address these issues.

[c7sus]

Originally Posted by fraserhutch

Speaking of SPL meters, anyone got a good recommendation on an accurate one?

Radio Shack supposedly markets a cheap SPL meter that works well.

[bubbagump]

Yeah, the Radio Shack SPL meter is as good as any.

[fraserhutch]

Hmmm, I've heard that the Radio Shck meter is wildly inaccurate in the higher frequencies.

I guess it wouldn't hurt to try it at the price.

[bubbagump]

For basic SPL of pink noise to calibrate against (or to use to measure the kids next door because you are a fuddy can want to call the cops ) , it is fine... Most computer based RTAs and measurement softwares want to calibrate the pink noise it puts out so it knows that X db out translates to 85db or whatever other value at the listening positon in the room. But no, you don't want to use it for really critical stuff that is high frequency heavy. And really, for room treatment purposes, we are much more concerned about the low end as the high end is controlled pretty easily.

[bennychico11]

like bubba said, I wouldn't use an SPL meter when concerned about treating the room....it really isn't going to show much. It will just tell you how loud the sound is coming out of your speakers at that position...it's not going to tell you where the problematic frequencies are unless you test each and every individual frequency. And even then, the mic isn't the greatest at all frequencies (I think I read it doesn't go beyong 8kHz?). Plus, the SPL meter only gives whole numbers.
Also, if you plan on analyzing your room using software and a test microphone...you need to keep in mind the effect the converters/preamps will have on the signal going into the computer. It can give you a unreliable reading, especially if using a typical sound blaster card. Take a look at this calculator to help with information on a typical rectangular room before doing a RTA test.
http://realtraps.com/modecalc.htm