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measurements

thornclaw

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when taking measurements of an amplifier like THD, it appears the measurement is taken in a vacuum. is there a method that takes the variable load of the speaker in to account? in real life, the speaker sends electricity back to the amplifier so there is an interaction at play between speaker and amp
 

egellings

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I think the problem is that different models of speakers exhibit so many different load characteristics that it would be difficult to select some common standard to use for a measurement load.
 

Wes

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automated load controller & measurement system
 

LTig

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Either this, or test with different ohmic loads down to 1 Ohm and note the clipping points. An amp which behaves well at 2 Ohm or below is able to handle any load - except maybe a full range electrostatic speaker.
 

LTig

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I think the problem is that different models of speakers exhibit so many different load characteristics that it would be difficult to select some common standard to use for a measurement load.
One can use a simulated "standard load" like Stereophile does, to measure the deviation from flat FR depending on the output impedance of the amp. OTOH if we measure the output impedance directly we can calculate this deviation for any speaker with known impedance curve.
 

LTig

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when taking measurements of an amplifier like THD, it appears the measurement is taken in a vacuum. is there a method that takes the variable load of the speaker in to account? in real life, the speaker sends electricity back to the amplifier so there is an interaction at play between speaker and amp
This interaction is minimized by the output impedance of the amp. Only amps with high output impedance fail to so, but since those usually show high distortion values due to low global feedback the distortion may swamp this effect. One should stay well clear of such amps anyway.
 

Vini darko

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One can use a simulated "standard load" like Stereophile does, to measure the deviation from flat FR depending on the output impedance of the amp. OTOH if we measure the output impedance directly we can calculate this deviation for any speaker with known impedance curve.
Amir did experiment with a simulated load for a while. Can't remember why it was dropped.
Edit : Found where it started with the Behringer A800
https://www.audiosciencereview.com/...behringer-a800-stereo-amplifier-review.10499/
 

egellings

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It's not only the DC ohms (real) part, but the reactive (imaginary) part that makes up the impedance of a speaker load. You would need to standardize on some accepted complex impedance, rather than on just a resistive one. How you would choose that, I dunno.
 
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thornclaw

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as well as changing resistance, the movement of the cone generates a current that the amplifier would have to deal with. i dont know if the standard testing equipment simulates this
 

pozz

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as well as changing resistance, the movement of the cone generates a current that the amplifier would have to deal with. i dont know if the standard testing equipment simulates this
Back EMF? Damping factor, i.e., a measurement of the ratio between the amp's output impedance and the speaker impedance. This is not really relevant for modern SS amps.
 

restorer-john

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Part of the reason is complexity and cost to build a high powered version of the simulated speaker load.

As Amir wrote "Note that neither my load, nor stereophile's are high power ones. So I cannot plot full power graphs and such. Above measurements were at 5 watts."
 
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