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Old 8th July 2012, 11:07 AM   #11
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Someone referred to Douglas Self book. I assume he had developed speaker load simulation circuit for his own amps. May be someone call recall in which particular book he had described this circuit?
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Old 8th July 2012, 11:31 AM   #12
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Quote:
Originally Posted by Jay View Post
Thanks for the link, but i couldn't find the most important information: how much does the modelling help in simulation? When they are most needed? And so on (I'm not gonna do the experiment for sure)
Truly speaking I didn't bother for " how much does the modelling help in simulation? When they are most needed? " Linuxguru wanted a spice simulation of speaker and I too am working on spice simulation of speakers. But my purpose is different. and is still on anvil. so I provided the link as a pointer.

Me too is working on the simulation and would like to have a complete spice models for speakers. that would simulate like a real speaker load.
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Old 8th July 2012, 12:22 PM   #13
tvrgeek is offline tvrgeek  United States
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Or a model where we could plug in the driver parameters. A little script that could calculate them from the TS electrical measurements would be handy.
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Old 8th July 2012, 01:46 PM   #14
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Stereophile magazine use this to simulate a speaker:

Real-Life Measurements | Stereophile.com

Quote:
...the general point that an amplifier should be measured into a load similar to that of a real loudspeaker is a valid one. Loudspeakers can be much more demanding than resistive loads, as evidenced by Eric Benjamin's 1993 AES paper, "Audio Power Amplifiers for Loudspeaker Loads." We had been thinking about how to implement this for some time, when, as a result of a chance conversation, Ken Kantor of NHT and International Jensen sent us a speaker simulator he had been using.

Its circuit diagram is shown in fig.1. Combinations of resistors, inductors, and capacitors produce a load with an impedance magnitude and phase plot (fig.2) intended to represent a typical two-way, sealed-box, 8 ohm loudspeaker. (The small-value resistors shown are the measured series resistances of the coils.) The impedance peak in the bass is the equivalent of the woofer's enclosure resonance; the peak in the low treble is identical to that produced by a crossover filter. The phase angles are also typical; note that the worst-case phase never coincides with the lowest magnitude.
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Old 8th July 2012, 01:49 PM   #15
sreten is offline sreten  United Kingdom
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Hi,

I can't see the point. You can model a typical basic drivers impedance,
You can model typical midranges and tweeters also. You would then
need to model a typical 2 or 3 way x/o to use with your models.

For what purpose ? A typical speaker model won't tell you
anything useful from testing / simulation that I am aware of.

Some say you should design amplifiers for up to 45 degrees reactance,
some say up to 60 degrees. Basically those loads are more thermally
onerous on the amplifier than pure resistance because the "power"
not dissipated in the load needs to be dissipated in the amplifier.

4 ohms at 60 degrees is a punishing load for an amplifier. The SOA
calculations if your designing output protection are very different
to the 4R case, often not mentioned or covered in textbooks.

But as I said, assuming 4R as the load for an 8ohm amplifier, and
2R as the load for a 4 ohm amplifier usually covers the worst case.

rgds, sreten.
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Last edited by sreten; 8th July 2012 at 01:54 PM.
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Old 8th July 2012, 02:16 PM   #16
dlp4341 is offline dlp4341  United States
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A few years back I was testing power amps with four output transistors. I studied the SOA, Safe Operating Area of the transistors with real speakers as the amp load. The transistors were rated 150 watts, 15 amps, 100 volts. The power was derated to 75 watts to allow the heat sinks to run hot. Using an XY scope I monitored the current and voltage of each output device. The protection ckt limited the current to 3 amps when the amp was driven with a short circuit load (zero ohms).
The SOA was +/_ 50 vdc and +/_3 amps. This "Box" was my operating window.
At idle the CRT spot sits at zero amps 50 volts. Dead center of the Box. With program signals and real speaker loads the Box is filled with traces. With sine wave test tones and 8 ohm loads, the traces are just a line. I hope this helps you to understand what is happening.
Don
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Old 8th July 2012, 02:48 PM   #17
tvrgeek is offline tvrgeek  United States
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I found a good model. It is in D'Appolito's book on page 15 with the equations to fill it in if you have FULL T/S parameters. Dr. Joe rides to the rescue again.
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Old 8th July 2012, 03:00 PM   #18
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dear tvrgeek, pl can you tell which book is it? or refer me to some online shop selling the book.
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Old 8th July 2012, 03:28 PM   #19
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Quote:
Originally Posted by Aucosticraft View Post
dear tvrgeek, pl can you tell which book is it? or refer me to some online shop selling the book.
I assume this one, the one he is most known for:
Testing Loudspeakers Book 500-030
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Old 8th July 2012, 03:56 PM   #20
jcx is offline jcx  United States
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Speaker load medel

my implementatin of Graham's Areil model:
Audibility of output coils
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