Looking for a CD to test room acoustics...

[michele]

I am looking for a basic CD that will help me giagnose the most obvious acoustic problems in my office/media room. (a friend of mine has the meeter from Radio Shack).


Thanks
Michele

[Dusty Chalk]

link

[nightflier]

Sort of on the topic...

How about a CD with music & instructions and what to listen for in evaluating a sound system (sibilance, dynamic range, tight vs. loose bass, compression arificats, phase, etc.)? Something available commercially, maybe? I used to have an LP for setting up phono cartridges, but it has disappeared. My own music is OK for this, but I think these disks would emphasize the errors so that they would be easier to make out. Any suggestions?

[E-Stat]

I am looking for a basic CD that will help me giagnose the most obvious acoustic problems in my office/media room. (a friend of mine has the meeter from Radio Shack)

I use the Stereophile Test CDs. The first one has all sorts of useful tests. The warble tone decade is great for setting speaker position for the flattest overall bass response.

Stereophile Test CD

Follow the "Click here for more information" to get descriptions of the various tracks. Not free, but I find indispensible.

rw

[Dusty Chalk]

Here is another one. (Doesn't come with instructions.)

[bfalls]

Stereophile used to give the CDs away with new subscriptions. I believe I still have two or three different versions. They have good test and alignment tones as well as some very well recorded music. Many of the home theater test discs have utilities for audio as well as video. Video Essentials and Avia both have audio and video tutorials.

I'm guessing since this is in an office, you're talking two-channel. Depending on how serious your listening and what equipment you have, you may want to google setup considerations for subwoofers, or speaker placement, since the room is a major part of the setup process.

[nightflier]

E-Stat,

That was the one: Stereophile. I'll have to check those out.

Dusty,

Bink wasn't exactly what I was loking for, but it definitely will be added to my toolbelt. Excellent resource. Thanks!

[E-Stat]

Here is another one. (Doesn't come with instructions.)

That is a nice link for a freebie. And yes, it seems there is a Word document that provides some documentation.

rw

[audio_dude]

dusty: isn't it great when my old threads get dug up over and over again for the same reason?

[Woochifer]

Surprised that nobody has mentioned the Rives Audio test CD yet. The key advantage of this CD is that it comes with a set of test tones that are calibrated to the accuracy of the Radio Shack analog SPL meter (which decreases as it goes further down into the bass range). It also has some test tracks that are purportedly mastered in different ways for you to check the phase accuracy.

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

Another set of downloadable test tones come from Real Traps, which markets some highly recommended acoustic paneling systems. These are spaced at 1 Hz intervals, which allows you to more add more data points to your response charts.

http://www.realtraps.com/test-cd.htm

Yet another tool for room measurement that I recently started using is the Room EQ Wizard (REW) application. It can plot out the in-room frequency response as well as time domain effects in much the same way as a real time analyzer program. This is pretty advanced stuff and you have to register in order to download the application. But, it has a lot of functionality to it, it can be calibrated to the Radio Shack SPL meters, and it has a MIDI controller for the Behringer Feedback Destroyer, which many of us on this board use for subwoofer equalization. As with the BFD, the REW application has quite a learning curve and I'm still in the beginning stages with the program. And because my laptop only has a microphone input, I need to get an external soundcard with a line level input and connect it to the SPL meter's external output.

http://www.hometheatershack.com/roomeq/

[michele]

Hey thanks much guys.

Lots of good information/link/leads.
I am going to begin by d/l'ing some of those file and take a look into it. (I will probably end
up getting a full CD however)

This is going to help me setup the speakers I have and then move on to the acoustic panels.
It seems I read somewhere I should begin with the floor and ceiling, is that true?

(floor is carpetting so the ceiling is next for me)

Thanks.

Michele

[PeruvianSkies]

So I just tested out that tracks by realtraps and was amazingly impressed with how my speakers performed on all Hz levels. I wasn't expecting them to perfectly handle all levels and I could feel the tones at my inner core that's how impressive they were executed. I would be interested to see what others say about how their system did with those tones.

[Woochifer]

This is going to help me setup the speakers I have and then move on to the acoustic panels.
It seems I read somewhere I should begin with the floor and ceiling, is that true?

(floor is carpetting so the ceiling is next for me)

Thanks.

Michele

Actually, any hard flat reflective surface can create acoustical issues, as will the room dimensions (i.e., the shorter the room dimensions, the more problems they create in the bass range).

I would definitely start with the floor first. Simply laying down a thick rug will help tame the echoes quite a bit.

In general though, you'll want a combination of absorption and diffusion. Fortunately, you can accomplish a lot of this by simply filling your room with furniture and other normal household items. The placement will naturally affect the sound, but you don't necessarily have to turn your living room into a recording studio.

One approach to room acoustics entails putting absorption panels at the "reflection points" along the side walls and the ceiling (identify these by having someone move a mirror -- wherever you can see the tweeters reflecting in the mirror from your seated position is where you should position the absorption panels), using diffusors along the backwall, using bass traps in the corners, and using absorption along the front wall behind the main speakers (unless you use dipolar or bipolar speakers that reflect the sound off the front wall).

If you don't want to go with absorption panels, you can also tame the first reflections by simply hanging quilts or cloth coverings on the side walls. Sir Terrence has also noted that thick blackout curtains also work very effectively at reducing the reflected sound. Generally, acoustic panels are the way to go because they can absorb sound further into the midrange, and their absorptive characteristics are more uniform from frequency to frequency.

With diffusion, you can use commercial products or simply line up some bookcases that are filled with books of varying sizes. These irregular surfaces will break up the sound waves. Also, if you live in a house built in the 60s and 70s, you might have one of those acoustic "popcorn" ceilings. Those spackled ceilings work very well at taming echoes and keeping sound from traveling to adjacent rooms at full volume.

You don't need to overdo it. An overly absorptive room can drain the life out of the music. Just tame the extremes and fine tune any remaining problems. The most difficult area to control with just room treatments is the bass. You can optimize the bass with careful speaker and/or subwoofer placement, and bass traps. But, small to medium sized rooms will still create wave interactions that cause unevenness in the bass response. Any remaining issues with the bass can be controlled by using a parametric equalizer with your subwoofer. We've had plenty of prior discussions on parametric equalization, and the Behringer Feedback Destroyer in particular, if you're interested in doing a thread search.

[E-Stat]

I would definitely start with the floor first...

Great summary, Wooch. I use all those strategies in my main listening room. My room required a forest of traps in the back corners. Regarding bipolars, some absorption on the wall behind the 'stats can be helpful. You want to minimize reflections caused by the rear wave from confusing the frontal image. I use fake ficus trees at the first reflection points. Or at least my approximation since the entire diaphragm surface is a "tweeter".

Also thanks for reminding me of the compensation curves available for the Radio Shack meter. Googling the topic yielded these two useful tools. The first is an Excel spread sheet that plots the correction factor into a smooth graph. The second is a set of adjusted compensation values because the newer digital unit like mine behaves differently than the original.

Excel spreadsheet

Scroll down for appropriate table

It appears the newer meter is more accurate with the larger (>1 db) errors found largely below 30 hz. I'll have to measure my room again using the corrections if for no other reason than to get the cool graph.

rw