[Danberg]

I am looking for a source and recommendation of a 20Hz to 20kHz CD to analyze the sonics in my listening room.  As a newbie to this, I was going to set up a meter (such as Radio shack) to observe the various standing waves and their db changes by frequency.  Am I going down the correct path to determine what frequencies are most troublesome and need to be corrected?
Are there any CD's out there that vocally state what frequency tone that is playing?  How many frequencies / tones are necessary to get a proper picture of the rooms acoustic weaknesses?
Any general help will be appreciated!

[JLM]

Stereophile offers 3 different test CD's that have a variety of identified tones to do exactly that.

IMO you are on the exactly right course.

Beyond learning your speakers/room (which will probably drive you crazy trying to it flatten out), you'll find out just how loud you listen.

Regarding various sound pressure levels (spl):
1. Extended exposure to 85 dB or more will cause permanent hearing loss.  
2. Most audiophiles listen at 70 - 80 dB average levels.
3. 105 dB is symphonic peaks

To calculate power vs. dB:
1. It's a logrthymic relationship.
2. So twice as loud = 10 dB of gain and takes 10 times the watts.
3. Half again as loud = 3 dB of gain and takes twice the power.
4. Example, if you have 90 dB/w/m efficiency speakers and want to reach 105 dB peaks you need 15 dB of gain or 50 watts.
5. Two speakers/channels doubles the power.
6. Speaker efficiencies are rates at only 1 meter away, doubling the distance costs 3 dB.
7. As rooms reflect much of the sound you don't lose as much spls as the straight theory would suggest, in fact for a 12 ft x 20 ft room in a typical speaker/listening setup you can simply use the speaker efficiency rating (gain from two channels plus room reflection = increased distance loss).

[PhilNYC]

Rives Audio has a good one, including Radio Shack-corrected tracks:

http://www.rivesaudio.com/software/softframes.html

[JoshK]

Thanks for the link Phil, I just picked up one of them.  Looks pretty useful!

[Ethan Winer]

Dan,

> Am I going down the correct path to determine what frequencies are most troublesome and need to be corrected? <

I don't think so. All rooms have peaks and nulls at all frequencies, not just those related to the room dimensions, and not just those you measure at one particular location. Moving the measuring microphone even a few inches can give very different results. Even more important, to truly assess the response in a room requires measuring at very fine intervals. In the past I used sine waves 1 Hz apart, and now I use the ETF program from www.acoustisoft.com which can resolve to even finer than 1 Hz.

You are correct to be concerned about acoustic problems - that puts you way ahead of most audiophiles - but the best solution is broadband absorption that works to as low a frequency as possible. That way you'll solve all the problems, not just those you think you measured.

--Ethan

[JLM]

Ethan, thanks for clarifying what I tried to say (in a hurry).

It's far better to fix the room than to try an equalizer bandaid.  As you indicated, moving a few inches would nullify any benefits from an equalizer.  (Brian Cheney from VMPS has said the same thing.)

[ctviggen]

Ethan,

What mic do you use with that?  

Thanks.

[Ethan Winer]

Bob,

> What mic do you use with that? <

I have an expensive AKG small diaphragm condenser mike with a calibrated omni capsule, but I also have the standard Radio Shack SPL meter. Both give similar results at low frequencies, deviating more and more at higher frequencies. Unless you're prepared to spend a lot of money on this, the RS meter makes the most sense.

--Ethan

[ctviggen]

That makes it easy!

[8thnerve]

You guys are strange.  When I am looking to get a full range room anal on, I look to something a little funkier, like Enigma for DRIVING beats, or maybe some Ottmar Liebert if you are going for that passionate latino vibe.

I just can't imagine using a test CD.  "Hey honey, here comes the white noise!!!"

Sorry, I couldn't resist.  I have been laughing my ass off at this subject line for days...

[Ethan Winer]

Nathan,

> I just can't imagine using a test CD.  "Hey honey, here comes the white noise!!!" <

ROF,L.

I agree that test tones and pink noise do not give a very satisfying listening experience. And how music sounds is of course the ultimate test. But without a steady sound source there's no way to measure the room's true response or reverb time, or directly assess the effectiveness of a trial placement or treatment.

--Ethan

[woodsyi]

Here is what I am playing with.  This was recommended by a resident guru on Outlaw forum:

http://www.trueaudio.com/
Level 4 software give 1/24th octave resolution

http://www.musiciansfriend.com/srs7/sid=040628070915066245196102702682/g=home/search/detail/base_pid/270400/

http://www.musiciansfriend.com/srs7/sid=040628070915066245196102702682/g=live/search/detail/base_pid/701368/

Xlr microphone cable and a boom stand all come to $225.  Of course, you have to bring your own computer with a soundcard.

I just got them and hooking up to a notebook was a breeze.  I have just begun to experiment with it.  There is not enough time in a day........

[8thnerve]

I agree that test tones and pink noise do not give a very satisfying listening experience. And how music sounds is of course the ultimate test. But without a steady sound source there's no way to measure the room's true response or reverb time, or directly assess the effectiveness of a trial placement or treatment.

--Ethan

Completely agree.  And just in case anyone didn't get where I was coming from (I just kill myself), I wasn't talking about room analysis.

[Carlman]

I've been waiting for someone to comment on a "recommendation for a room anal".  I know room acostics can be a pain in the ass... but sheesh!