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LinuksGuru 7th July 2012 07:30 PM

Speaker Load Simulation
 
Hi, folks,

Can anyone please share speaker load simulation circuits(s) used for amplifier testing?
Both real circuits and SPICE simulations are very welcome.

Thanks in advance.

1audiohack 7th July 2012 10:18 PM

Are you looking for something to dump power into while testing an amp or something more complex?

LinuksGuru 7th July 2012 10:24 PM

Quote:

Originally Posted by 1audiohack (Post 3084951)
Are you looking for something to dump power into while testing an amp or something more complex?

I'm looking to examine behavior and stability of amplifier at high power and complex load.
Power dumper I already have - several 25W/16 Ohm wire-wound resistors.

jcx 7th July 2012 10:49 PM

typical complex load at audio frequency isn't a linear stability problem - maybe clipping/current limitng and protection circuit activation/recovery could be

if wanted there are spice models of driver and crossover

cable C load ~ O(1 MHz) loop gain untiy intercept can be a amp stability issue - isolating series L, Zobel load are used for decoupling for linear stability with uncertain load Z

usually lumped nF C directly on the amp output is adequate to explore cable loading stability effects

tvrgeek 7th July 2012 11:30 PM

Where have you found decent spice models for drivers? I came up with my own, but looking at the models Linkwitz discusses, mine are far short of a realistic electrical model. I just use a resistor with a series inductor. Not good enough.

To the OP. From what I have learned so far, two issues for your tests. Low resistance, i.e what does it do at 3 or 2 Ohms, and capacitance. That's what makes amps go crazy. How much? Don't know. Might punch your amp into SPICE and see what it takes to turn it into an oscillator. I can tell you how to do that with a DH-120!

sreten 8th July 2012 01:35 AM

Hi,

You don't need to simulate loudspeaker loads. You just apply rules of thumb.
4R testing should deal with any difficult 8 ohm speaker and 2R testing should
deal with any difficult 4 ohm speaker in reality. Modelling a specific real load
doesn't really help at all as they are all different. Some go for 6R for 8 ohm
and 3R for 4 ohm, as acceptable, probably is, better than AV specifications.

Point is reactive loads are basically equivalent to lower load resistance.

rgds, sreten.

Jay 8th July 2012 06:51 AM

In terms of stability (i.e. inductive/capacitive load) I don't think it is necessary to model the speaker accurately as Sreten has noted.

But may be there is a little use (I've never tried such as I think it is also unnecessary) when you design the amp for best performance against varying impedance (with changing frequency).

Speakers typical impedance are well known. And especially when you know your speaker impedance chart/behaviour.

You can model the load with LCR traps and such, which is not a difficult thing to do. You may need it for example to simulate THD20? Nothing to loose imho.

Aucosticraft 8th July 2012 08:20 AM

North Reading Engineering
http://www.integracoustics.com/MUG/MUG/articles/woofer/

Did the links help you ?

tvrgeek 8th July 2012 09:27 AM

Problem is, all speakers are not typical or that well behaved, and some "exotic" wire is very difficult. It may depend on the amps output filters, or lack of them, it's compensation margin etc. I remember some discussion of a load box HK built that was highly regarded by some of the gentlemen here who design amps for a living. No idea what was in it.

Jay 8th July 2012 10:30 AM

Quote:

Originally Posted by Aucosticraft (Post 3085195)

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)


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