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Old 23rd December 2007, 01:06 AM   #1
tolits is offline tolits  Philippines
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Default Asymmetric drive to asymmetric loudspeaker

Hi,

I would like to ask your opinions regarding this idea. It probably accomplishes the push pull effect with out inverting physically the woofer. Right now , I am applying it to an open back arrays.I have place a tube limiter(12ax7) before the power amp that limits the negative going cycle. I do this because of the asymmetric shape of the cone of the speaker aside from the asymmetric magnetic forces. From side view perspective, the cone is spearlike in the negative going signal but on the positive going signal, it has a higher drag owing to the parachute effect of the cone. I have attached the negative limiter I am using. The effect reduces some distortions which the DCX is not capable of removing and the difference significant particularly with the open back arrays.Without it, I cannot listen to the arrays. I have applied it to the array midbass (open back) and the array woofers(open back). TIA

http://picasaweb.google.com/bernardo...OpenBackArrays


Lito
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Old 23rd December 2007, 02:03 AM   #2
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Default negative assymetry

So what you're saying is that the rarefaction drag on the "parachute" side, as you put it, is lower than the compression stroke, and vice versa? And that this effect is remedied by "cancelling" the negative half of the waveform, essentially rectifying the signal? If you have a planar driver, this shouldn't be a problem, no? Maybe you could show that with your setup.

have you made any measurements that show any of this to be true, or is this improvement based on hearing only?

John L.
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Old 23rd December 2007, 03:37 AM   #3
AJinFLA is offline AJinFLA  United States
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Default Re: negative assymetry

Quote:
Originally posted by auplater
have you made any measurements that show any of this to be true, or is this improvement based on hearing only?
I'm going to take a wild guess here.....

cheers,

AJ
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Old 9th January 2008, 06:45 AM   #4
tolits is offline tolits  Philippines
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Default Is this test valid?

I tried measuring 2nd order distortion of my open back array using a tube limiter which reduces the negative going signal and Speaker Workshop to measure it and these are the result. Frequency at 1 power.When there is no limiting, this the value I get from the graph 2nd harmonic distortion at 200 HZ. My stimulus is 100 HZ sine. As I increase the limiting of the signal, it goes down to 1.4db , 1.22, 1.011, .537 , .357 . I am new to this software and it is quite difficult to use. Apparently any limiting to the negative going signal reduces 2nd order distortion ? What do you think? TIA
Lito

http://picasaweb.google.com/bernardo...OpenBackArrays
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Old 10th January 2008, 04:45 PM   #5
sreten is offline sreten  United Kingdom
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Hmmm.......

Tests at one frequency do not mean a lot. A tube limiter set to
cancel 2nd harmonic at 100Hz at a particular level will significantly
increase 2nd harmonic distortion above this frequency and at
other power levels.

/sreten.
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Old 11th January 2008, 05:14 PM   #6
tolits is offline tolits  Philippines
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Default checked 3rd & 4 th harmonic

Checked 3rd & 4th harmonic distortion and there was an apparent reduction too.. 678 to .65 and .8 to .7 .I changed to the stimulus to 200 hz and again , as I trimmed the negative cycle, the 2nd harmonic decreased from 1.559, 1.28 , .99 , .42
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