Subwoofer Tests - Fall 2007 - Page 11 - Home Theater Forum and Systems - HomeTheaterShack.com
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post #101 of 475 Old 10-13-07, 03:17 PM
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Re: Subwoofer Tests - Fall 2007

WillyD,

Actually, that is purely coincidental. Unibox doesn't have a significant amount of nonlinear modeling capability and even if it did you'd need more information than just small signal parameters and a simplified excursion model.

My guess is that TC-2K does quite well down low due to a linear suspension and pretty good motor and not as good up high due to high inductance and big coil (i.e. modulation distortion and eddy currents in the steel etc.). I don't see how Unibox could be predicting this.

-Chris
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post #102 of 475 Old 10-13-07, 04:43 PM
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Re: Subwoofer Tests - Fall 2007

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I don't see how Unibox could be predicting this.

Actualy even far more sophisticated softwares can't predict it. Aside from Linearx's LEAP 5 wich seems to be the best modeling product, I don't see any other soft that can actualy ''see'' or predict nonlinear behavior/compresion at high power levels. TS data of course would be absolutly insufficient for that matter.
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post #103 of 475 Old 10-13-07, 04:55 PM
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Re: Subwoofer Tests - Fall 2007

I never said it wasn't coincidental. I was just making an observation. Of course I know that Unibox or any other simulation program can't accurate predict distortion limited output...who do you take me for?

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I don't see how Unibox could be predicting this.
Unibox actually does have the ability to use a couple non-linear parameters, such as L2 and R2, which allow an "improved model of voice coil inductance simulating Eddy currents". So of course Unibox can help to predict how the inductance affects the output in the higher frequencies.
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post #104 of 475 Old 10-13-07, 08:10 PM Thread Starter
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Re: Subwoofer Tests - Fall 2007

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WillyD wrote: View Post
Unibox actually does have the ability to use a couple non-linear parameters, such as L2 and R2, which allow an "improved model of voice coil inductance simulating Eddy currents". So of course Unibox can help to predict how the inductance affects the output in the higher frequencies.
L2 and R2 aren't non-linear parameters per se.
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post #105 of 475 Old 10-13-07, 08:12 PM Thread Starter
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Re: Subwoofer Tests - Fall 2007

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Hi Ilkka,

You didn't happen to measure the amplifier output voltage during the distortion test sweeps, did you? While you are already doing a massive amount of work, this would help settle the debate about how much power is required to really push these DIY sub drivers tot their CEA-2010 distortion limits etc.
Unfortunately not. That would require more sophisticated hardware than just a simple DMM due to burst signals.
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post #106 of 475 Old 10-13-07, 08:43 PM Thread Starter
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Re: Subwoofer Tests - Fall 2007

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For sweeps, I would definitely agree. For 6 cycle bursts like were used (I believe?) for the CEA testing, I'm not so sure. Ilkka - was power the limiting factor for the TC2k CEA test above 25hz, or was it distortion?
For both TC2k and SDX15 it was power (but only at and above 50 Hz actually).

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From sweeps or from bursts?
Both but it's more obvious when looking at the THD sweeps.

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Isn't burst testing more representative of real world material reproduction?
Yes.
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post #107 of 475 Old 10-13-07, 08:46 PM Thread Starter
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Re: Subwoofer Tests - Fall 2007

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I know the amp clipped during the sweep testing, but I don't believe it clipped during the burst testing. If that's the case, then more power wouldn't necessarily add much to the burst test.
Both the T.Amp TA2400 and the Crown CE4000 clipped during the burst testing at 50 Hz and above. I wasn't able to clip the CE4000 during the sweeps though.
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post #108 of 475 Old 10-13-07, 08:51 PM Thread Starter
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Re: Subwoofer Tests - Fall 2007

Guys,

I'm not any more following some of the reasoning done by a few of you. That's maybe because I have seen all the data and you haven't.

But when it comes to TC2k/SDX15/LMS-5400 distortion, it's already posted here. Nothing actually changed during the GP/high power measurements. You can see the "pattern" already there.

The TC2k is more cleaner, has less compression and has more output than the SDX15, at every frequency (assuming same amp is used of course).

Now can you please stop fighting until you see the rest of the data?
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post #109 of 475 Old 10-13-07, 09:55 PM
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Re: Subwoofer Tests - Fall 2007

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Ilkka wrote: View Post
L2 and R2 aren't non-linear parameters per se.
I read this in a paper by Klippel.

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To investigate the effect of each nonlinearity separately and to find
the dominant source of distortion the following nonlinearities
might be switched on and off during simulation:
• motor nonlinearity due to Bl(x)
• mechanical suspension nonlinearity due to Cms(x)
• inductance nonlinearity due to Le(x)
• para-inductance nonlinearity due to L2(x)
• losses from eddy currents due to R2(x)
• reluctance force (electromagnetic drive)
• adiabatic compression in enclosure CAB(Pbox)
• adiabatic compression of rear enclosure CR(Prear)
• radiation distortion (Doppler effect)
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post #110 of 475 Old 10-13-07, 09:57 PM
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Re: Subwoofer Tests - Fall 2007

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Now can you please stop fighting until you see the rest of the data?
Not fighting, just discussing. I'll stop though. You've told me what I wanted to know anyways.
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