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Old 11th August 2009, 03:58 PM   #1
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Default Martin Logan CLX distortion

Just noticed that the July issue of Hi-Fi World has a review of the CLX which includes some measurements.

The review is currently a free download here: (2nd down on list)
http://www.absolutesounds.com/index....ategory=review

What caught my eye was this comment:
“…Distortion levels were a little above conventional loudspeakers and varied across the bass panel area below 100Hz, falling from 3% at 40 Hz down to 1% or so at 100Hz, then around 0.3% upt to 1kHz, falling to 0.1% to 6kHz.”

The SPL is not specified, but my guess would be 90dB @ 1m as is typically used. In any case, 1% distortion at 100Hz is not what I would have expected. Is it typical for low frequency distortion to be this high in an ESL? I haven't had access to any "full range" ESLs to measure.
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Old 11th August 2009, 05:55 PM   #2
Few is offline Few  United States
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I wonder if the double diaphragm, triple stator construction of the bass panel increases the bass distortion for some reason. I can't come up with a mechanism that would explain that, at least not at the moment, but it is an unusual feature of the CLX.

Few
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Old 11th August 2009, 06:55 PM   #3
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Hi,

there is nothing dramatic or unusual regarding distortion levels of the CLX.

Like all fullrange ESL the excursion of the membrane causes higher K2 distortion which isn't critical for the ear

More important is K3, which is lower for good ESL if compared to dynamic woofers.

Unfortunately most testing magazines only take a look on K2.

A fullrange ESL can end up with 10-20% K2 at higher sound pressure without any sound coloration. But if an dynamic woofer exceeds 3% K3, it sounds compressed, limited........



Capaciti
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Old 11th August 2009, 07:29 PM   #4
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Quote:
Originally posted by Capaciti
Hi,

there is nothing dramatic or unusual regarding distortion levels of the CLX.

Like all fullrange ESL the excursion of the membrane causes higher K2 distortion which isn't critical for the ear

More important is K3, which is lower for good ESL if compared to dynamic woofers.

Unfortunately most testing magazines only take a look on K2.

A fullrange ESL can end up with 10-20% K2 at higher sound pressure without any sound coloration. But if an dynamic woofer exceeds 3% K3, it sounds compressed, limited........



Capaciti
I am unfamiliar with the K2, K3 termonology.
Does K2 mean 2nd harmonic? and K3 mean 3rd harmonic?
If that is the case, I have a couple questions.

1)
From what I have read concerning symmetric ESLs at low frequencies, 3rd harmonic(K3) results from membrane excursion due to charge migration(when surface resistance in not high enough) and nonlinear compliance(diaphragm tension increases nonlinearly for large excursions). Is this correct?

2)
Assuming construction of the ESL is perfectly symmetric is there any mechanism for 2nd harmonic? or is the 2nd harmonic contribution completely due to imperfection in the construction. The only thing I could come up with is the fact that when charged the diaphragm assumes a steady state position that is away from the center position no matter how perfect the constuction is.

You mention excursion of the membrane causing 2nd harmonic(K2) distortion. I don't understand how excursion of the membrane in flat symmetric ESL panels could cause 2nd harmonic(K2) distortion since the compliance nonlinearity is the same for motion on either side of the center point which would result in 3rd harmonic(K3). Curved panels are another matter.
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Old 12th August 2009, 01:24 AM   #5
Few is offline Few  United States
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I should be able to figure this out but my brain seems to have stalled. What's the relationship between the symmetry of the restoring force and the presence of even or odd harmonics? It "feels" (always dangerous) like nonlinear but symmetric forces should yield even harmonics while nonlinear and antisymmetric forces should yield odd harmonics. Is that the case or do I have this exactly wrong?

Few
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Old 12th August 2009, 01:53 AM   #6
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Quote:
Originally posted by Few
I should be able to figure this out but my brain seems to have stalled. What's the relationship between the symmetry of the restoring force and the presence of even or odd harmonics? It "feels" (always dangerous) like nonlinear but symmetric forces should yield even harmonics while nonlinear and antisymmetric forces should yield odd harmonics. Is that the case or do I have this exactly wrong?

Few

Exactly opposite actually. I remember by visualizing square waves which are built up from the fundamental plus odd harmonics.

For 2nd harmonic, think of the transfer curves for a single ended tube voltage amplifier...how it amplifiers one half of a sine wave more than the other.

Hope this helps rather than confusing things for ya...
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Old 12th August 2009, 06:07 AM   #7
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Even a panel is made prefectly, the membrane always bends towards one stator. In addition the movement is never like a flat sheet, but in different swinging modes, which are caused by the memrane frame and supports. Take a look to the movement when the membrane moves by using a light reflecting into it. Especially in the lower frequency range, more modes are present. Thats the reason for increased second harmonic K2. The higher the frequency the more those modes are not present and K2 reduces.

At frequencies higher than e.g. 100 Hz ESL-K2 is better than most other drivers

For my experience K3 depends on the quality of the stepup transformer and and possibly required passive network for frequncy compensation.

Capaciti
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