so you think loudspeakers are linear eh!

Nice paper, thanks for posting it! I've found the klippel data very interesting in the Vance Dickason speaker test articles and this paper has made them even more interesting now that I have keys to really understand what the data is all about :D

Klippel has developed some technology to address these nonlinearities in realtime! Don't know when an actual products are available... Very cool new tech though, Klippel Controlled Sound : Cancellation of Nonlinear Distortion Be sure to check them demo videos!:)
 
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BradH

Member
2019-07-13 10:35 pm
Klippel goes into some nice details and I appreciate his use of illustrations and graphs. I'll add another good read which is Geddes chapter on the subject from his book Audio Transducers. He discusses the measurment of nonlinearities via nonlinear transfer functions expanded into polynomial orders in a way that's eloquent and easy to follow. He also goes into the psychoacoustic perception of distortion which Klippel's paper does not cover.

http://www.gedlee.com/downloads/AT/Chapter_10.pdf
 
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BradH

Member
2019-07-13 10:35 pm
This is semantics. Calling speakers linear devices is not a declaration that they are not non-linear, it classifies their primary behaviour for the purpose of analysis. This technical term has been misinterpreted.

Agreed.

This applies not just to lab analysis but to your living room as well. When properly designed and operated as intended, speakers behave as linear devices.
 
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AllenB

Moderator
Paid Member
2008-10-18 11:31 am
Even still (to be pedantic), even when they are showing non-linear behaviour, they are also linear devices.

The point is these are separate things. They can be talked about in isolation regardless of the other one.

As it turns out it is simpler to do linear analysis when non-linearity is lowest, but to read anyhting into this would be a red herring.
 

AllenB

Moderator
Paid Member
2008-10-18 11:31 am
You could talk about the performance of a car in a straight line, then introduce the fact that it also turns corners. You could point out that even for a given speed, the velocity changes when turning. This doesn't invalidate straight line performance, it merely complicates the analysis of it.
 
Measure the frequency response of any driver at at least three different drive levels 10dB apart from each other. The measured level differences between the three different curves will be exactly 10dB at frequencies where there are peaks in the impedance curve.

At frequencies where the driver has an impedance minimum, there will be less than 10dB between each of the curves. This is going to be due to thermal power compression from the increased heating from the increased current flow at this frequency.

At the very low end of the drivers response, there will be less than 10dB between each of the curves because the suspension will be limiting the excursion of the driver as level increases more and more.

You can also measure the driver's impedance curve at different drive levels. This makes it very easy to see some on the nonlinearities in the driver.
 
a question if i may, does a speaker's frequency response vary with volume?

Yes, but only if you're hammering it.

I took a Faital 10HX230, a passive crossover, a mic that's happy up to 140dB, and a [email protected] amplifier.

I then ran a sweep with REW, increased the levels by 3dB, and ran the sweep again. And again. And again. And then some more times until the speaker started to show real signs of stress.

The final sweep recorded around 125dB, which is impressive for sine tones. Harmonic distortion got as high as 50% in places, and there was a few dB of compression above 10kHz.

Interestingly, the 3" port coped fine with the air flow, but there was a 100Hz highpass.
Driven with more bass, I'd expect the usual port compression to show up at the bottom of the range.

Chris
 
so no appreciable or measurable changes until this condition was met?

There was the gradual distortion rise with level, as you'd expect from flux modulation, suspension non-linearities etc.

However, the frequency response only changed at extreme levels. The 10" cone is rated for 250w long-term, and the HF driver more like 30w, so to dump a 1KW sine sweep in there is seriously abusive.

Chris
 

turk 182

Member
2012-10-26 3:03 pm
Pano sorry not seeing any response v level comparisons (but i may not be looking in the right place)


does anyone know of any previous work or studies on this very subject?


i understand that the absence of previous work in no way constitutes a confirmation of response variability with volume, but for me it does raise the question is this something overlooked?


i wish i could go back in time to analyze the conditions of measurement i've done in the past as the response variations which i've seen are what led to the perhaps erroneous conclusion that frequency response varies with volume.
 
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Pano

Administrator
Paid Member
2004-10-07 6:05 am
Panama
Turk, if you pick a driver and look at it's axial FR you'll see buttons for different drive levels. See screenshot below.
 

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