Stereophile has started calculating EPDR.

[SIY]

Like I said your the only one so far that doesn't believe in EPDR as being a real load value to amplifiers.

Ahem.

And cool story, bro.

 

[audio2design]

I am the only one? You really are totally lacking in amplifier knowledge. Ralph at Atmosphere and a number of other amps designers called out your errors. You have made this EPDR crusade before but have yet to justify your claims.

Please explain EPDR effects on a class D amp in your own words. You are the self proclaimed expert on EPDR. In your own words how does it effect a class D amp. Now, tell me how EPDR effects the peak current draw on a traditional class AB amp in your own words. That should be easy for you.

 

[georgehifi]

Ralph at Atmosphere

Your quoting a OTL amp maker!!!!!!!! Of course Ralph is going to deny it exists, he wants to sell amps too, and now he trying to manufacture a class-D and they won't cut it either into that Alexia EPDR load either. (and get that right too it's Atmasphere)

 

[audio2design]

Still waiting for you to explain in your own words ....


How many amps you have on the market? He has designed and is selling an OTL amp. I don't agree with him on everything but he has a very solid grasp of amplifier design and makes no blind wild claims about tube amps.


Again, waiting for you to explain in your own words.

 

[georgehifi]

and makes no blind wild claims about tube amps

Your blind, if you see it that way, or maybe your in with the class-D project

 

[audio2design]

Okay George, I am trying to help you out here. Please explain how EPDR impacts Class-D in your own words. Then do the same for Class-AB as it applies to the peak current. I don't understand your resistance to doing this. It my be of benefit to others. I am hoping that you will realize the error of your understanding when you do it.

 

[georgehifi]

Okay George, I am trying to help you out here.

Quite the opposite your ragging and demeaning on everything said. Show quotes from "known hiend designers" of SS amps that back you.
Especially when we tried it on Edgar Kramer's Soundstage resident speaker Wilson Alexia's. A 400w Class-D just didn't cut it in the low bass even though it was stable, compared to a 100w Gryphon.

 

[amirm]

Especially when we tried it on Edgar Kramer's Soundstage resident speaker Wilson Alexia's. A 400w Class-D just didn't cut it in the low bass even though it was stable, compared to a 100w Gryphon.

Didn't cut it how? Which class-D amp?

 

[georgehifi]

Didn't cut it how?

Drive, dynamics and depth of the lows, the Class-D just sounded thin and un-dynamic, like they were running out of steam even though they were 400w, compared to the 120w Gryphon

One he may have been reviewing Amir can't remember what is was, going back to his old house a couple of years ago.
His old house setup https://ibb.co/92z436h

 

[amirm]

Drive, dynamics and depth of the lows, the Class-D just sounded thin and un-dynamic, like they were running out of steam even though they were 400w, compared to the 120w Gryphon

Those are subjective remarks that can't be verified. If the amplifier shut down, damaged, etc., then there would be something. That is the context for EPDR anyway. In other words, this is no evidence one way or the other.

 

[audio2design]

Quite the opposite your ragging and demeaning on everything said. Show quotes from "known hiend designers" of SS amps that back you.
Especially when we tried it on Edgar Kramer's Soundstage resident speaker Wilson Alexia's. A 400w Class-D just didn't cut it in the low bass even though it was stable, compared to a 100w Gryphon.

George there are many actual amplifier designers on this forum. You will note the ahem above. They are not rushing to defend you because you are wrong. EPDR - Equivalent Peak Dissipation Resistance. Dissipation as in power dissipation. Why can't you explain in your own words what EPDR means for a class D amp? Why don't you explain how EPDR pacts peak current in a class AB amp? I am not being demeaning simply stating you are wrong and my position is the one of someone who has designed amps. Here this will help you. Without EPDR, at a signal output of 16v into 8 ohms with a 24v rail, you will have 2A with a dissipation in the amp of (24-16) * 2 = 16 watt at the peak. Lets say for that magical speaker the impedance is flat 8 ohms at all frequencies. Now let's say it has an EPDR at some frequency of 4 ohms. The peak current will still be 2A as that is defined by the impedance and voltage (AC). However because of reactive components this will happen at an instantaneous output voltage of 8V due current leading or lagging voltage due to phase shift. The dissipation in the amp is now (24-8)*2 = 32W peak. That is how EPDR works and how it is intended to be used. It is intended to show potential thermal dissipation issues in an amplifier that works in the linear region. This is most important with BJT amps due to secondary breakdown mechanisms.

 

[georgehifi]

George there are many actual amplifier designers on this forum. You will note the ahem above. They are not rushing to defend you because you are wrong.

And they don't rush to defend you either, we know what we heard and we go with what Stereophile describes EPDR is as load seen by an amplifier, and it worse than just low impedance alone if combined with high negative phase angle. As as it sounded just like it on the Alexia's when it was driven by 400w Class-D
Goodbye

 

[JSmith]

the Class-D just sounded thin and un-dynamic

What sort of test was done to confirm this assertion? Would be interested to see the results of same if available.

Goodbye

JSmith

 

[audio2design]

And they don't rush to defend you either, we know what we heard and we go with what Stereophile describes EPDR is as load seen by an amplifier, and it worse than just low impedance alone if combined with high negative phase angle. As as it sounded just like it on the Alexia's when it was driven by 400w Class-D
Goodbye

George this is a technical site and I provided a simple but detailed explanation complete with example and numbers to support my assertion. Making a hand wave to Stereophile (whose explanation actually matches what I have wrote) does not advance your argument.


From Stereophile:

Taken together, these figures confirm that the orders of EPDR identified in figs. 8–10 are of real, practical significance when playing music signals: speakers really can make these high demands of amplifier output-device dissipation in normal use. If the amplifier's protection is invoked as a result, then its output will be clipped, even though the speaker's voltage and current demands may be within its capability.

https://www.stereophile.com/reference/707heavy/index.html

 

[BoredErica]

There's a significant flaw in this metric. I'm currently (ouch!) working on a better method. Initial results look interesting.

I think that it will likely be complete and published by December.

Any news?

 

[SIY]

Any news?

Looks like I'll have the article out in about a month or two.

 

[Ingenieur]

https://www.stereophile.com/content/goldenear-brx-bookshelf-reference-x-loudspeaker-measurements
And he is going back to previous reviews and adding this in.

EPDR (Equivalent Peak Dissipation Resistance) takes the impedance and phase data and computes a new impedance that shows what equivalent load the amplifier will see. This takes the guesswork out of knowing how an amplifier will handle a given speaker if we have measurements of that amp into low impedance.

For example, in the BRX link above, here is the raw impedance & phase:

The raw impedance never goes past 3ohm. However, at 135Hz where the impedance is ~5ohm and the phase around -45°, the EPDR is 1.53ohm, over 3x lower.

This is something that I believe would greatly benefit Amir’s reviews, we just need to know the calculation.

For those providing EQ adjustments to speakers measured here, it would also be interesting to see how they effect the EDPR.

This is supposed to represent the power dissipated/produced by the amplifier,
I question the relevance.

Z = impedance
R = resistance
X = reactance
Phase = angle V to I in degrees
Z = R + jX
phase a = arctan(X/R)
R = |Z| cos a
X = |Z| sin a
It can also be expressed as |Z| / a

Let's pick a point on the graph,
We'll use his : "minimum EPDRs of 2.15 ohms at 59Hz"

From graph:
These are eye-balled estimates
Z = 5.6 Ohm at 59 Hz
phase ~ 34 deg
R = 5.6 cos 34 = 4.64 Ohm
EPDR ~ sqrt(R) ~ 2.155 Ohm
Close to the quoted 2.15

The square root is due to P being proportional to V squared.

At least my understanding.
Edit: scaled it

 

[peng]

Sorry you are the only one so far I've seen denying the exitance of EPDR as a real load presented to an amp, especially in the bass where it demands big current delivery if it's low impedance as the 0.9ohm EPDR of the Wilson Alexia's.

Are you saying you would use the EPDR value to calculate the actual current draw by a speaker load? I think audio2design is trying to tell you the actual/real current flow is still calculate based on the actual impedance, not the EPDR (Equivalent Peak Dissipation Resistance). If EPDR is half that of the actual impedance, the current draw will still be determined by the actual impedance value, but the heat dissipation in the amp could be estimated by inflating the current, using the lower EPDR value. If the concern is about current capability of the amp, EPDR can be ignored, if the concern is about heat, then EPDR could be useful.

 

[valerianf]

"if the concern is about heat, then EPDR could be useful"
But only in the case of a classic class A, A/B, G or H.
The EPDR does not apply to the heat dissipation of class D amps that have a pulse modulated output.

 

[Head_Unit]

Never minding EPDR for a moment, shouldn't it be possible to just calculate how a complex impedance would equate to a simple resistive load from a current draw perspective? Or does that make no sense/not really possible without referencing an output topology?
(It's been too long since I took those classes, so forgive my incomprehension).

Likewise to

The EPDR does not apply to the heat dissipation of class D amps that have a pulse modulated output.

How DOES complex impedance related to heat dissipation in class D amps?