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Old 17th January 2005, 11:25 AM   #21
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All that is too hard for me.

I just burn a CD with white noise (NOT pink) noise and play it on my system while recording it with a microphone into the soundcard using CoolEdit '96 or whatever. Then I do a Frequency Analysis of the recording. Easy-peasy.

Make sure your microphone input on the soundcard is actually flat though.
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Old 17th January 2005, 11:30 AM   #22
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If you use white noise as a test source I'd be worried about putting excess power into the tweeter. If use use an RTA then a pink noise source will give a flat response, and is much less likely to do any tweeter damage.

I use TrueRTA in its 1/24th octave mode, with an ECM8000 and a home made pre-amp/phantom power source and it works extremely well.
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Old 17th January 2005, 11:47 AM   #23
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Quote:
Originally posted by Ouroboros
If you use white noise as a test source I'd be worried about putting excess power into the tweeter. If use use an RTA then a pink noise source will give a flat response, and is much less likely to do any tweeter damage.

I use TrueRTA in its 1/24th octave mode, with an ECM8000 and a home made pre-amp/phantom power source and it works extremely well.
there ya go. white noise is not flat...

basically, if you are willing to spend any more you can get a much quicker, more accurate system.

true RTA w/ 1/24th octave capability = $100, ECM8000 = $50, mic pre w/ phantom = $50(home brew) - $!!! sound card = $30-$80...

as usual, you get what you pay for...but that's damn good bang for the buck....
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Old 17th January 2005, 12:24 PM   #24
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White noise is flat, but if you measure white noise with a system that measures in fractional octave bands, you'll get a response that rises at 3dB/octave.

Use white noise if you're measuring with a spectrum analyzer, but pink noise if you're measuring with an RTA.
(But then this is basic textbook stuff, so I'd assumed everyone knew this.)

I'd still recommend the $99 version of TrueRTA, 1/24th octave analysis can be quite useful.
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Old 17th January 2005, 01:01 PM   #25
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Quote:
Originally posted by Ouroboros
Use white noise if you're measuring with a spectrum analyzer, but pink noise if you're measuring with an RTA.
(But then this is basic textbook stuff, so I'd assumed everyone knew this.)

.
yes indeed i should have said not flat w/ an rta...

which i assumed is what we were talking about, my bad
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Old 17th January 2005, 09:35 PM   #26
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Quote:
Originally posted by Ouroboros
Use white noise if you're measuring with a spectrum analyzer, but pink noise if you're measuring with an RTA.
(But then this is basic textbook stuff, so I'd assumed everyone knew this.)
Took =me= a little while to figure it out at first.

Pink for Pieces of spectrum.
Whitle for Whole spectrum.
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Old 17th January 2005, 11:07 PM   #27
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Default Re: Radio Shack 33-2050 and 33-4050

Quote:
Originally posted by noisenyc
my point was this: the only thing you can accomplish with the correction table is third octave centers, which you already have on the cd,

the frequency centers are identical on the cd and correction table.
Exactly! So why buy the CD when you can download a free single generator and accomplish the exact same thing with the correction table.

Gio.
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Old 17th January 2005, 11:11 PM   #28
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Default Re: Re: Radio Shack 33-2050 and 33-4050

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Originally posted by gmilitano


Exactly! So why buy the CD when you can download a free single generator and accomplish the exact same thing with the correction table.

Gio.
yes, now i get ya.

it's not a very convenient method either way, but those values vary quite a bit and the meter is kinda hard to read...it's just a lot easier for me to center around 0 vu than hop all around...i'd go 21 for the added ease
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Old 17th January 2005, 11:23 PM   #29
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Default Re: Re: Re: Radio Shack 33-2050 and 33-4050

Quote:
Originally posted by noisenyc


yes, now i get ya.

it's not a very convenient method either way, but those values vary quite a bit and the meter is kinda hard to read...it's just a lot easier for me to center around 0 vu than hop all around...i'd go 21 for the added ease

Agreed, but I am cheap and this is after all DIY audio!

I got an SPL meter a while back, but have yet to make any real good use out of it. I want to try some measurements with a tube and SS amp on the same speaker and compare the results. It will be somewhat crude, but may have some interesting results.

BTW - how long are the tone tracks and break between tracks on the CD?

Cheers,
Gio.
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Old 18th January 2005, 03:39 AM   #30
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Default DIY 3rd Octave RTA

I put together an RTA 3rd octave CD. I will try do some measurements this weekend.

I can hear 16kHz, but not 20kHz. I know 20kHz is there as the SPL meter picks it up.

Cheers,
Gio.
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