[geoff]

On 4/05/2017 12:51 p.m., Scott Dorsey wrote:
geoff wrote:
On 4/05/2017 11:48 a.m., Scott Dorsey wrote:
I think today most speaker designers are assuming zero source impedance and
amplifier designers are assuming simple resistive loads (maybe checking
out either side of the nyquist plot to make sure things are stable into a
simple reactive load), and in the end neither of those is necessarily a
good assumption to make.

And of course the speaker isn't even linear and time-invariant.

... but what else could you do that the average consumer could
understand ?
You could say "voiced to sound best with amplifier type X" at the very least.
--scott

Probably fall foul of anti-competition watchdogs, or would be
suspected of dodginess by most consumers.


Generally speaking 8 ohm ratings for amps requiring higher loads than
those rated 4 ohms has worked sufficiently OK for most users since
solid-sate amps became common.

geoff

[Ron C[_2_]]

On 5/3/2017 8:51 PM, Scott Dorsey wrote:
geoff wrote:
On 4/05/2017 11:48 a.m., Scott Dorsey wrote:

I think today most speaker designers are assuming zero source impedance and
amplifier designers are assuming simple resistive loads (maybe checking
out either side of the nyquist plot to make sure things are stable into a
simple reactive load), and in the end neither of those is necessarily a
good assumption to make.

And of course the speaker isn't even linear and time-invariant.

... but what else could you do that the average consumer could
understand ?

You could say "voiced to sound best with amplifier type X" at the very least.
--scott

IMHO, most consumers wouldn't understand "voiced" let alone what various
amplifier "types" even exist.
==
Later...
Ron Capik
--

[Don Pearce[_3_]]

On Wed, 3 May 2017 17:33:57 -0700 (PDT), Phil Allison
wrote:

Scott Dorsey wrote:

It's not unusual for a load to be mostly resistive at one frequency,
mostly capacitive at another, and mostly inductive at a third.

** Which merely equates to flat, falling or rising impedance curves at particular frequencies - something nearly every speaker on the planet exhibits but is harmless.

Yes, exactly! And with a well-designed amplifier, it _is_ harmless.


** It is harmless to *any* amplifer.



YOU claimed the ESL63 was a capacitive load that caused problems - which is false.

" It's actually pretty capacitive, enough to blow up the Dynaco ST120.
I don't recall where the poles and zeroes fall but it wasn't good. "

I did make that claim, because I have seen ST120s blow up and I have plotted
the poles and zeroes for both.

For capacitance to cause amplifier failure, it has to be severe with impedance falling to near zero at supersonic frequencies.

That's making a big assumption about the amplifier.


** Prey tell - what assumption am I making?



Clearly, the ESL63 does not do anything like this.

It's very happy into an ST70 in spite of the higher source impedance of the
ST70. But the ST120 is rather touchy about loads... doesn't take much of
a shift to the left of the plane to cause issues.


** The ESL63 is not capacitive, it is a benign load.

Amplifiers do not go unstable with such loads.

If all you have for proof is an isolated anecdote, we are done.

Bye....


..... Phil




As long as a speaker makes a noise it will not look like a capacitor,
although the impedance vector may be negative on the imaginary axis.
The fact that a sound is coming out means that real, in-phase current
is flowing. My measurements in the complex plane indicate that a
typical speaker does not come even close to looking like a capacitor.
Although I have not subjected an ESL63 to the same testing, it is
clear from the normal modulus plot that the same applies.

In a vector impedance plot, such as I posted earlier, when the curve
moves above the line the speaker looks inductive, and when it moves
below it looks capacitive. Both those conditions apply at multiple
points in the frequency range, and the main consideration for any
amplifier is that it remain stable under all those load conditions.

In the audio range this is normally simple, but that stability
criterion must be met at higher frequencies too - right up to the
frequency at which the amplifier gain falls below 1. That is where
some designs in the past have come undone.

d

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

[Phil Allison[_4_]]

Don Pearce wrote:


Phil Allison


** The ESL63 is not capacitive, it is a benign load.

Amplifiers do not go unstable with such loads.

If all you have for proof is an isolated anecdote, we are done.

Bye....


As long as a speaker makes a noise it will not look like a capacitor,
although the impedance vector may be negative on the imaginary axis.



** Yep - capacitors are notoriously poor audio transducers.



My measurements in the complex plane indicate that a
typical speaker does not come even close to looking like a capacitor.



** With all that wound copper and steel who would expect otherwise ??


Although I have not subjected an ESL63 to the same testing, it is
clear from the normal modulus plot that the same applies.


** Of course, the impedance rises sharply just above 10kHz.



In a vector impedance plot, such as I posted earlier, when the curve
moves above the line the speaker looks inductive, and when it moves
below it looks capacitive. Both those conditions apply at multiple
points in the frequency range, and the main consideration for any
amplifier is that it remain stable under all those load conditions.


** A simple task that nearly all amps can easy perform.


In the audio range this is normally simple, but that stability
criterion must be met at higher frequencies too - right up to the
frequency at which the amplifier gain falls below 1.



** Shame published speaker impedance cures never include frequencies in the long wave band.

Must be a reason for that ..........


..... Phil

[[email protected]]

On Wednesday, May 3, 2017 at 7:32:22 PM UTC-4, Phil Allison wrote:
wrote:


Show me a complex impedance plot, then.



** So you can post even more of your gobbledegook.


Darn, Phil slapping Scott around.



** Actually, I am trying very hard not to do that.

Scott is a well respected person and definitely means well.

FYI:

The topic of speaker / load impedance and its possible interaction with various commercial amplifiers is a very complicated PLUS like most things in audio has generated a considerable mythology over the years.

Fact is, amp makers and speaker makers are at odds with each other. There are no recognised rules for either to follow so that the two products are compatible.

I wrote this article back in 2000 to cover just one aspect of the issue:

http://sound.whsites.net/vi.htm

Phil, I am IMPRESSED!

Never knew speaker impedance varied as much from what I seen.
But, I guess a lot of factors have to be considered, maybe even CEMF.
I don't see capacitance enter into the picture, maybe at high frequencies, you know, capacitance between turns of the voice-coil.

Nice.

Thank you!

Jack


.... Phil

[Scott Dorsey]

geoff wrote:
On 4/05/2017 12:51 p.m., Scott Dorsey wrote:
geoff wrote:
On 4/05/2017 11:48 a.m., Scott Dorsey wrote:
I think today most speaker designers are assuming zero source impedance and
amplifier designers are assuming simple resistive loads (maybe checking
out either side of the nyquist plot to make sure things are stable into a
simple reactive load), and in the end neither of those is necessarily a
good assumption to make.

And of course the speaker isn't even linear and time-invariant.

... but what else could you do that the average consumer could
understand ?
You could say "voiced to sound best with amplifier type X" at the very least.

Probably fall foul of anti-competition watchdogs, or would be
suspected of dodginess by most consumers.

Generally speaking 8 ohm ratings for amps requiring higher loads than
those rated 4 ohms has worked sufficiently OK for most users since
solid-sate amps became common.

Hopefully true, although there are still a lot of folks selling speakers that
are voiced for use with tube amps.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Phil Allison[_4_]]

wrote:

Phil Allison wrote:



** So you can post even more of your gobbledegook.


Darn, Phil slapping Scott around.



** Actually, I am trying very hard not to do that.

Scott is a well respected person and definitely means well.

FYI:

The topic of speaker / load impedance and its possible interaction
with various commercial amplifiers is a very complicated PLUS
like most things in audio has generated a considerable mythology
over the years.

Fact is, amp makers and speaker makers are at odds with each other.
There are no recognised rules for either to follow so that the two
products are compatible.

I wrote this article back in 2000 to cover just one aspect of the issue:

http://sound.whsites.net/vi.htm


Phil, I am IMPRESSED!


** Why?


Never knew speaker impedance varied as much from what I seen.
But, I guess a lot of factors have to be considered, maybe even CEMF.
I don't see capacitance enter into the picture, maybe at high frequencies,
you know, capacitance between turns of the voice-coil.

Nice.



** You know, a British guitarist pretty much summed up this kind of situation a few decades ago in a simple pop song he wrote called " Substitute".

His name was Pete and he wrote:

" The simple things you see are all complicated ... "

Hard to argue with that.

See Vid:

https://www.youtube.com/watch?v=ts9-4jbFWGg


BTW,

the drummer and bassist earned their pay...



.... Phil

[[email protected]]

Fact is, amp makers and speaker makers are at odds with each other.
There are no recognised rules for either to follow so that the two
products are compatible.


There are at least two different ways a reactive load can damage an amp.

1) The feedback loop can go unstable usually causing a high level ultrasonic oscillation that may damage the speaker or amp or both. This can happen even with no program material. If the feedback loop is designed with adequate margin, this should not happen.

2) The reactive load causes the voltage and current to be out of phase and this can cause the transistors to exceed their voltage or current or power safe operating area ratings. This usually takes loud program material.
If the device ratings have adequate margin, this should not happen.

Sometimes the oscillation in #1 can provide the "loud program material".

A well designed amp with proper current limiting protection can survive driving a short.

m

[[email protected]]

On Thursday, May 4, 2017 at 8:59:40 AM UTC-4, Phil Allison wrote:
wrote:

Phil Allison wrote:



** So you can post even more of your gobbledegook.


Darn, Phil slapping Scott around.



** Actually, I am trying very hard not to do that.

Scott is a well respected person and definitely means well.

FYI:

The topic of speaker / load impedance and its possible interaction
with various commercial amplifiers is a very complicated PLUS
like most things in audio has generated a considerable mythology
over the years.

Fact is, amp makers and speaker makers are at odds with each other.
There are no recognised rules for either to follow so that the two
products are compatible.

I wrote this article back in 2000 to cover just one aspect of the issue:

http://sound.whsites.net/vi.htm


Phil, I am IMPRESSED!


** Why?


Never knew speaker impedance varied as much from what I seen.
But, I guess a lot of factors have to be considered, maybe even CEMF.
I don't see capacitance enter into the picture, maybe at high frequencies,
you know, capacitance between turns of the voice-coil.

Nice.



** You know, a British guitarist pretty much summed up this kind of situation a few decades ago in a simple pop song he wrote called " Substitute".

His name was Pete and he wrote:

" The simple things you see are all complicated ... "

Hard to argue with that.

See Vid:

https://www.youtube.com/watch?v=ts9-4jbFWGg


BTW,

the drummer and bassist earned their pay...



... Phil

Impressed you published something.

I feel differently from that song, allow me to explain, all occurred during Winter...

A.) At Mom's, HVAC stopped working in middle of Winter. Checked breaker box, all okay. Gas heat, didn't want to screw with it. Finally called for emergency service.

B.) Mom's garage, went to turn on garage light, no go. Replaced bulb, no go.

C.) At work, Emergency exit signs came on for no good reason.

How quickly could you fix all? You'd probably say, you need to troubleshoot first. Could be complicated.

What was common with all of them in one season, electrical switches and circuit breakers. Aged components, I guess metal contracts (shrinks) during the cold, and it's just a matter of turning them off and on and everything comes to life.
Granted, the aged components should be replaced.

It just amazed me how all these occurred about the same time.

Jack
p.s. There is a two way light switch in garage, never even knew of the second (defective) light switch!

[PStamler]

Back in the 1970s, didn't the Acouetical Manufacturing Company (makers of Q..U.A.D. speakers) publish an equivalent circuit for the speaker we know as the ESL-57? I remember seeing it in one of the British hi-fi mags; it included a shunt 2µF capacitor with nothing in series with it.

Peace,
Paul

[Phil Allison[_4_]]

wrote:



There are at least two different ways a reactive load can damage an amp.

1) The feedback loop can go unstable usually causing a high level ultrasonic oscillation that may damage the speaker or amp or both. This can happen even with no program material. If the feedback loop is designed with adequate margin, this should not happen.


** Meaningless drivel.

Amps do not oscillate just because the speaker is reactive.



2) The reactive load causes the voltage and current to be out of phase and this can cause the transistors to exceed their voltage or current or power safe operating area ratings.

** The word "can" make the info meaningless.



...... Phil

[Phil Allison[_4_]]

PStamler wrote:


Back in the 1970s, didn't the Acouetical Manufacturing Company
(makers of Q.U.A.D. speakers) publish an equivalent circuit for
the speaker we know as the ESL-57?


** Don't think so.

I remember seeing it in one of the British hi-fi mags;


** Very reliable - not.


it included a shunt 2µF capacitor with nothing in series with it.


** As the speaker's impedance rises above 20Khz, that is dead wrong.


A Quad ESL57 has a impedance of 6 ohms at 20Hz, rising smoothly to its maximum of 30ohms resistive at 100Hz then falling gradually to 12 ohms at 5kHz. Above 5Khz it falls smoothly to 2ohms resistive at 18kHz - then rises steadily beyond that.

Connecting a 2uF cap directly across the output of an amplifier is an absurd test.


..... Phil

[Trevor]

On 2/05/2017 4:14 AM, Don Pearce wrote:
I am able to measure speaker impedances both as modulus (total
impedance) and in the complex plane. Here is a Mission 774 which
advertises itself as 8 ohms

http://www.soundthoughts.co.uk/look/mission_imp.png

http://www.soundthoughts.co.uk/look/Mission_complex.png

In the complex plane it is a bit easier to see where the problems
lie.The blue marker is at 1.5kHz The loops of impedance do indeed
centre on 8 ohms, even though the speaker is never particularly close.


But clearly a 4ohm speaker when choosing an amplifier, which of course
is the problem for all single figure specs.

Trevor.