Test Tones CD/DVD or Analyzer Rental - AVS Forum
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post #1 of 12 Old 05-13-2001, 09:07 PM - Thread Starter
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Hi everyone,

I've looked in few places, but I haven't come across a DVD or CD that will generate the pink noise, 1/3 octave test tones that will allow me to config my eq. Can somebody recommend one?

Anybody in northwestern NJ area that will rent a decent spectrum analyzer?

Thanks,
Mike
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post #2 of 12 Old 05-14-2001, 03:59 AM
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hi mike,

seen someone ask this before, and the answer was to use cool edit on a pc to generate tones.

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post #3 of 12 Old 05-14-2001, 07:34 AM - Thread Starter
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Hmmm...

I have a CD-RW drive, but I don't have a DVD player that will read CD-R's.

Should I just use the line-out on my audio card? Use a cable that's 1/8" on one end that splits into phono plugs on the other? (This is kind of a bummer because it will be a pain to drag my PC into my HT equipment room and set it up there. Limited maneuverability.)

Thanks, Simon!
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post #4 of 12 Old 05-14-2001, 07:41 AM
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The "Video Essentials" DVD (available at Amazon and elsewhere) has more video test signals than audio, but I believe it does have pink noise test tones for each speaker. I am not sure what you mean about 1/3 octave tones. Hope that helps.
Dan
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post #5 of 12 Old 05-14-2001, 08:02 AM - Thread Starter
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I want to calibrate my eq by measuring the SPL of 1/3 octave bands, rather than using a pink noise test tone that covers the entire frequency spectrum. I have the Avia DVD, which provides the latter.

Why do I want to do this? I can't find a local shop that rents spectrum analyzers and I certainly don't want to buy one. With my Radio Shack SPL meter and 1/3 octave test tones, I can plot the frequency response of my HT without using a spectrum analyzer. The procedure will be more cumbersome and the results not quite as accurate, but they should suffice.

Thanks, Dan!
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post #6 of 12 Old 05-14-2001, 08:17 AM
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Hi Mike,

I have been after the same goal (renting an RTA)!

How are you going to use the 1/3 octave test tones and SPL meter? Can you post details?

I have these cd's sitting in the rack I think they are what your after, I am against the computer thing since I want to calibrate the real path (digital from dvd to processor) and not an analog computer connection.

https://secure.rt66.com/stereophile/new/recordings.shtml
http://www.stereophile.com/showarchives.cgi?176 http://www.stereophile.com/showarchives.cgi?338

I was thinking of buying a used RTA off of ebay...


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post #7 of 12 Old 05-14-2001, 12:00 PM
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If it's of any use and you have broadband access, I've got a CD I created with stereo, 1/3 octave warble test tones from 12Hz to 20kHz. It also has flat tones from 12Hz to 150Hz. There are also pink and white noise tracks. I'll put it up for FTP or something if anyone is interested.

-will

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post #8 of 12 Old 05-14-2001, 12:12 PM
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Replying to myself here...

Keep in mind, the disk I have is only stereo, so I don't know how much use it would be for you.

A quick 30-second Google search turned up this freeware 1/3 octave RTA program. I haven't looked at it yet, but it may work out for you: http://www.jdbsound.com/art/downloads.html
Of course, I guess you need a decent microphone too. Assuming it's a full-spectrum RTA, you could just generate pink noise and get an analysis that way.

-will

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post #9 of 12 Old 05-14-2001, 03:04 PM - Thread Starter
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Thanks, Will.

Your CD seems like a good fit, but I don't have a broadband connection at this time. Plus, I'm still trying to keep my PC out of the picture here. I don't want to cram it into my small HT equipment area. If my DVD player would read CD-R's, I'd have more options, but it does not.

Stereophile Test CD 2 looks like it will do the job. No 1/6 octave bands for bass, but I suppose that's ok. Test CD 3 is probably better, but I can't find any detailed info on it.

Thanks again for your help.

Mike
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post #10 of 12 Old 05-14-2001, 08:04 PM
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I think using the RCA line out on the RS SPL meter into a PC program like ETF that doesn't require a test CD (because it generates it's own impulse) is fundamentally a better methodology for room tuning. This includes speaker placement, sub crossover integration, and acoustic wall treatments.

website is www.etfacoustic.com

The website also has a complete example demo room for use of the product that explains a lot about what happens in small rooms. I'm just a happy user and have no connection with ETF. Program is $149



[This message has been edited by BruceD (edited 05-14-2001).]

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post #11 of 12 Old 05-14-2001, 09:26 PM - Thread Starter
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Hi David,

I wish I could tell you that I'm a sonic guru, but that would be WAY off the mark. However, I'll gladly let you know what I'm thinking. Then, if any of the gurus who peruse this forum see that I'm off the mark, they will hopefully chime in.

For L, C, R, speakers: My intention is to play each 1/3 octave tone, from approx. 80Hz to approx. 800Hz, sequentially through each speaker, taking an SPL measurement for each. The SPL meter will first be located at my primary listening position (in the first row) and pointing at the ceiling. I'll set it for slow response, C-weighting. I'll probably find something tall and thin to double as a tripod for the meter. I'll repeat the whole procedure at my secondary listening position in the first row. Then I'll repeat it two more times for two locations in the second row.

For LS and RS speakers: I'll take measurements from approx. 100Hz to 6.3kHz.

For LR and RR speakers: I'll do nothing. No equalization here.

For the sub: I'll take measurements from 22.4Hz to 80Hz using 1/6 octave bands of pink noise. (Well, probably not... depending on whether I can find a source that will accomplish this.) I have a Bijou eq that provides the ability to adjust within 1/6 octave bands in the sub's THX frequency range. Measurements will only be taken at primary listening position. I'll mess around with playing tones simultaneously through some combo of L,C,R, and sub to ensure a smooth crossover at 80Hz.

I'll average my four measurements for each speaker at each band and attempt to flatten the response. Cuts get preference over boosts. When I am done, I will repeat the procedure for the primary listening position only, to see to what extent corrections in one frequency range have affected other adjacent ranges. I'm hoping that my corrections will not so drastically affect adjacent ranges that I will want to jettison my SPL meter out the window. AudioControl, the makers of the Bijou, advertise a Constant-Q feature that supposedly minimizes this problem.

I haven't decided what I will use as a reference level. Anywhere from 75dB to 90dB. Might depend on what time of day I do this!

I've purchased a few things from ebay, including my projector! That was scary, but everything worked out fine. (So far...)

Thanks for the links! I'm going to check them out.

Mike
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post #12 of 12 Old 05-15-2001, 04:52 AM
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As a friend confirmed there is certain software available for a PC that will not only work as an RTA but also for the very important in room impulse-response measurements.

To have a flat frequency response, in other words to prevent "colorations" (a coloration width of one Terz, which is 1/3rd of an Octave, is what I hear most often to be the smallest width the human ear is sensitive to), is just one aspect. The next step is still to listen to room modes and echos/high-reverb (impulse fall times), which tend to make a certain frequency last for a too long period in the room.

Another friend did have a very long, almost endless, reverb time in the low bass freqeuncies, due to his giant windows and old house construction. So everything worked like a passive membrane and kept "singing" for ever.

You want a flat frequency response coupled with a very fast stopping impulse response. I think a reverb (I always mix up the proportions) of 0,3 sec. is the goal over the entire frequency spectrum, which tends to become impossible in low frequencies (or you have alot of room or cash http://www.avsforum.com/ubb/wink.gif).

Have fun.

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[This message has been edited by Andreas (edited 05-15-2001).]

Cheers, Andreas
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