Test tones for listening tests

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I have some test tones which were downloaded from an mp3 source.

The thing I noticed in the lower and lowest freq tests was:

1.) lots of Xmax activity by the driver itself

2.) some tone change as the sound played. The only analog I can think of is a transmission change in a car like the speaker was 'warming up' and changing pitch without changing the frequency on the player setting.


I cannot ascribe it to my hearing. It seems to be a mechanical thing.
 
Test tones

Test tones can test for enclosure integrity...some years ago a buddy of mine who was in the DJ business neede his speakers rebuilt,,,we changed drivers for a more balanced (Accurate) response & made a new enclosure. We did an A-B test at thirty hertz with the old against the new...the old set was merely vibrating the enclosure to death complete with air-leaks, resonances, and harmonics.
The old set would not propagate the low frequency,,,the new one on the otherhand set the windows in motion quite well.
____________________________________Rick..........
 
loninappleton said:
<snip>
The test tones gave so much excursion I thought the
surround was going to fly off.

The sound is sort of like a balloon being flapped by a bicycle wheel.

I have another test going today with less batting inside and covering just 2 walls.
In most enclosure designs the air in the chamber acts as a spring against the cone. In a ported design, the enclosure spring disappears below the port resonance frequency. At or below this frequency the woofer cone is un-damped, causing it to flop about kind of like a balloon being flapped by a bicycle wheel.

Don't test woofers blow their cutoff point, it provides no information and can damage the woofer. Do not operate woofers beyond the Xmax rating, either by too low a frequency or too high a drive level.
 

ronc

Member
2003-03-08 2:22 pm
I am a bit old fashioned in this subject. All i use or have ever used is a signal generator and an old RS analog meter (corrected) and a dual trace O scope.
You can learn/see a great deal by doing a study between the input signal (lower trace) and the recieved signal (upper trace). The ability to actually see the combined signal responses(different frequencies) occuring at the same time is a very good learning tool. However you actually realize more when watching the display and playing music. With a gate system you freeze the display and can actually study the responses.

ron
 
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