Can you overdamp the front wall?

The Stereophile CD has music as well as test tones. I found myself only using the test tones, but did not like the way they were configured. They use indexing (rather than tracks) for the individual test tones. This is okay for measuring the room initially, but it makes finding the "hot spots" in the room rather difficult. As to the accuracy, my understanding is that it is a flat response and while I haven't measured it I would be surprised if it were not flat. We made our own Test CD's with a series of flat response tones and then another series with a compensated response tones for use with the Radio Shack meter. I think ours is a more useful CD, but of course I'm heavily biased here.

Rives,

Your perspective on the CARA CD piqued my interest. Any comments on the usefulness/accuracy of the Stereophile Test CDs?

Clueless: I like your question about Studio vs Listening room. There's a world of difference. The tools used to acheive the sound are the same (or at least should be) but the result is entirely different. Everest talks about this in his books to some degree, but to sum it up in a nutshell (I will try anyway):

Studio's are designed to give back to the recording engineer an uncolored (also unflattering) presentation of what is/was being recorded and mixed. Studios are often heavily damped and in general operate with much lower RT-60 (this is the time for a 60 dB drop in sound). Studios sound "sterile" for the most part and are not engaging or involving. Studios tend to be small environments with monitors designed for nearfield listening. Please keep in mind these comments are generalized; there are absolutely studios that exist that would not fit into this category.

Listening rooms should be designed to some degree to add to the musical experience. I have listened to "dead" rooms that cost upwards of $150k to build. I personally thought they sounded dreadful as a listening room, but might make a good recording studio. The biggest difference is the reverberation times. They should be longer and create a spaciousness that envelopes the listener and recreates a soundstage and the experience of "being there". It is my opinion that the listening room is part of the equipment so to speak. It can have as much to do or more than any individual component and unlike most components, it can be tuned like an instrument. You wouldn't play a musical instrument way out of tune, but so many listening rooms are played that way.

All of that being said, you might find it intersting that our companies products are engineered by those in the professional (studio) world and some of our acoustical engineers have more than 20 years experience in designing studios--but they fully understand the difference in both--as I said the tools are the same, but the goals are different.

As to the CARA test CD, it is very good. I have used it myself, but keep in mind it only goes up to 200 Hz. I felt that was a bit limiting, so we manufactured our own for the full band width and even put in tracks to compensate for the non-linearities of the Radio Shack analog meter.

Hi:
Good points all around.

Tom has recommended Alton Everest's "Sound Studio Construction on a Budget" and Everest's "Master Handbook". Danner has mentioned his recording studio and his listening room.

Should a recording room and a listening room be approached in the same manner? What have you guys found to be the fundamental differences and/or similarities, if any?

Also the CARA 2.1 PLUS ($50), that Rives mentions, is excellent. The CARA test disk is excellent too at around $20. I haven't had the chance to demo much of the other room software around but, together, IMHO it is hard to figure a better way to spend 70 bucks on audio. It also got an excellent review from AudioXpress Magazine recently (August 2002)

Thanks in advance.

I remain,

Like most things, It's a matter of taste. I have a project studio where I have an LEDE (live end dead end) setup where the entire third of the studio with the monitors (front wall, ceiling, & side walls) is covered with absorptive material (and carpet on the foor) and the back has diffusion. This minimizes the effect of early reflections and allows you to hear 'into' the room where the recording was made. Imagining is amazing with pinpoint accuracy but it has a character unlike any other listening room. In my music listening room (where I listen to classical music) I have two 2'x4' absorbtive panels mounted horizontally behind the speakers with about .5' between them - works for me. Try different amounts in different locations (as well as diffusion) and see what you like best.

Tom's comments are correct, and the references are excellent as well. However, one aspect that Everest does not address (and rightfully so as these books have to have their limit) is how to handle this issue with different types of speakers. Planers, bi-pole, di-pole, and rear ported speakers all react differently to front wall diffusion and absorption. The front wall can actually be used almost as a tuning device. When you get the correct balance of diffusion, reflection, and absoption it can be bliss. The reference is very good on discussing how to calculate the total room absoption and diffusion and discusses how to balance it very well. Most people tend to overdamp rooms thinking that getting rid of more reflected sound will leave the sound that was intended by the speaker (or other) manufacturer. This rarely (virtually never) works as there must be an appropriate balance of frequency attenuation and diffusion over the entire frequency spectrum. There are also some good software programs that can help with this as well, such as the CARA 2.1 (which our company does sell, so I do have a vested interest there).

I recommend buying F. Alton Everest's "Sound Studio Construction on a Budget" (covers all kinds of rooms) or the 4th edition of his "Master Handbook ogf Acoustics". You'll see that he advocates diffusion rather than absorption for front and back walls. RPG's Skyline diffusor is a favorite of his. I have a DIY diffusor based on the same theory, if you can saw 2" Styrofoam into strips, then short pieces. I have Skylines on my back walls and my DIY's on the front, and the room remains lively enough, not overdamped (though Styrofoam does some absorbing too). I think you certainly can overdamp a front or back wall, or a side wall too, come to that. If you can try diffusion, I'm sure you'll like it. Please get in touch if you should want DIY plans.