Where can I find subwoofer harmonic distortion and CSD plots? - diyAudio
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Old 13th January 2006, 05:54 PM   #1
owdi is offline owdi  United States
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Default Where can I find subwoofer harmonic distortion and CSD plots?

Where can I find subwoofer harmonic distortion and CSD plots? I'm not looking for information on any specific driver, just some charts that cover 20-200hz. Frequency response charts are easy enough to find, but harmonic distortion and CSD seem impossible.

Bonus points for plots that show distortion at high power levels.

Dan
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Old 13th January 2006, 06:42 PM   #2
simon5 is offline simon5  Canada
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I know Aurasound show THD, but CSD never seen a subwoofer manufacturer publishing that data.

http://www.aurasound.com/

Someone else?
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Old 16th January 2006, 11:19 PM   #3
mike.e is offline mike.e  New Zealand
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You request too much
JBL tends to measure distortion at 1w and 10% Pe I think..

http://www.mfk-projects.com

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Old 17th January 2006, 06:43 PM   #4
owdi is offline owdi  United States
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mike.e - you are THE man. That is exactly what I have been looking for. The price/performance ratio of the Dayton RS sub is intimidating. I'm surprised just how much distortion all subwoofers generate, especially down in the 20 - 40hz region. This makes me question whether I've truly heard a 30hz tone, or just the harmonics.

Dan
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Old 20th January 2006, 03:39 AM   #5
mike.e is offline mike.e  New Zealand
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Bear in mind that with music present,you can not notice that distortion. For example I had a 96kbps mp3,that was a recording off a cassette,which was in turn off the radio. When I down 'rated' it to 8bit audio,I couldnt hear any difference

You probably havent heard a proper 30hz tone - You have to hear a decent reproduction of it ,and then youl know that you mainly feel it ;-)

Brings up an interesting issue - because everyone(well 90%) of people havent heard it,they dont know what they are missing.

The few that do,have only made a small investment too,and try to encourage the rest

Driving a sub free air gives an indication of cleanliness,my 2226JBL was silent to my ears(absence of gross distortion).

Mike.e
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Old 20th January 2006, 04:24 PM   #6
owdi is offline owdi  United States
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Quote:
Originally posted by mike.e
You probably havent heard a proper 30hz tone - You have to hear a decent reproduction of it ,and then youl know that you mainly feel it ;-)
Whenever I find the time, I'm going to try a 4th order bandpass that goes from 20 to 60hz. Harmonic distortion should be much lower than sealed, since there is an acoustic filter blocking high order harmonics.

Dan
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Old 22nd January 2006, 02:08 AM   #7
mike.e is offline mike.e  New Zealand
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Youd think so. But I dont know how effective it will be at 'blocking' since the chambers are normally not THAT large. I think of it in terms of gradually reducing output,so the distortion will decrease too,but its no magic bullet. Its just like putting an electrical filter there with say a bass reflex sub,except it is there physically.

Sure,there is definately a filtering effect,when combined with a decent active filter could result in a 4th order LR type of response.

Ive seen in an acoustics textbook some kind of FEA predicting higher port modes on a BP4due to physical dimensions and driver placements,but have never seen anything solid on the matter.

Check out beyma and JBL drivers for their distortion plots.
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