[Phil Allison[_4_]]

geoff wrote:




But what ARE the specs on such a vague spec.

Try this:

B&W 800 D3
Nominal Impedence 8 ohms (minimum 3.0 ohms)



** Can you post an impedance curve for the model ?

The maker says 8 ohms nominal and B&W are not likely to be liars.

Bet that 3 ohm minimum is way outisde the power band of music programme.

FYI:

The Quad ESL57 is quoted as nominal 16ohm, with a minimum of 1.7 ohms.

1.7ohms at 18kHz, only.


Here's the best that google can find on B&W 800 Z (for an older lesser
version).

http://www.stereophile.com/content/b...lSCLXF6qtJv.97



** The reviewer is right - that is a nominal 4ohm speaker and nasty example at that. I know quite a few high powered amps that could misbehave badly with it.

The Phase Linear 400 mkII, the Yamaha P2200 and early examples the Quad 405 need not apply.



..... Phil

[Scott Dorsey]

geoff wrote:

Obey the specs!


But what ARE the specs on such a vague spec.

Try this:

B&W 800 D3
Nominal Impedence 8 ohms (minimum 3.0 ohms)
http://www.bowers-wilkins.net/Speake...nd/800-D3.html

See, I'd call that a 3 ohm speaker.

Here's the actual impedance of the thing:
http://www.stereophile.com/images/511B800fig1.jpg

That'll be fine on a modern Hafler amp but on a tube amp with a commparatively
high source impedance, the load impedance variations are going to affect
response a lot.

As I recall the old B&W 801 monitors didn't have quite as ugly a plot.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

geoff wrote:
The Quad ESL57 is quoted as nominal 16ohm, with a minimum of 1.7 ohms.

1.7ohms at 18kHz, only.

I used to run 2 pairs, 2 in series each side, which made things a little
easier.

Now I have (stored away somewhere) a pair of ESL-63s, plus a scrap one
for parts, that are a pretty constant 8 ohms which comes across as
pretty much purely resistive.

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.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[[email protected]]

On Monday, May 1, 2017 at 9:40:58 AM UTC-4, Scott Dorsey wrote:
geoff wrote:

Obey the specs!


But what ARE the specs on such a vague spec.

Try this:

B&W 800 D3
Nominal Impedence 8 ohms (minimum 3.0 ohms)
http://www.bowers-wilkins.net/Speake...nd/800-D3.html

See, I'd call that a 3 ohm speaker.

Here's the actual impedance of the thing:
http://www.stereophile.com/images/511B800fig1.jpg

Looks pretty flat to me! :-)

Jack

That'll be fine on a modern Hafler amp but on a tube amp with a commparatively
high source impedance, the load impedance variations are going to affect
response a lot.

As I recall the old B&W 801 monitors didn't have quite as ugly a plot.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Don Pearce[_3_]]

On 1 May 2017 09:42:44 -0400, (Scott Dorsey) wrote:

geoff wrote:
The Quad ESL57 is quoted as nominal 16ohm, with a minimum of 1.7 ohms.

1.7ohms at 18kHz, only.

I used to run 2 pairs, 2 in series each side, which made things a little
easier.

Now I have (stored away somewhere) a pair of ESL-63s, plus a scrap one
for parts, that are a pretty constant 8 ohms which comes across as
pretty much purely resistive.

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.
--scott

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.

d

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[geoff]

On 2/05/2017 1:40 a.m., Scott Dorsey wrote:
See, I'd call that a 3 ohm speaker.




Maybe an extreme example (or not ?).

But then you would presumably have less 'nominal' impedances specified
for pretty much all speakers ?

geoff

[Scott Dorsey]

geoff wrote:
On 2/05/2017 1:40 a.m., Scott Dorsey wrote:
See, I'd call that a 3 ohm speaker.

Maybe an extreme example (or not ?).

I don't think it really is. I have seen speakers that were better, sure, but
I have seen plenty whose impedance curves looked worse.

And... in the end... if you have a good amp and good cables, it doesn't really
matter what the impedance plot looks like, just as long as the end result is
good coming out, and the lowest point on the curve isn't _too_ low.

But then you would presumably have less 'nominal' impedances specified
for pretty much all speakers ?

I think a minimum impedance would be far better than a nominal impedance.
If we specified a minimum, we wouldn't have people blowing amps up with
Apogee Scintillas anymore.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[geoff]

On 2/05/2017 1:42 a.m., Scott Dorsey wrote:
geoff wrote:
The Quad ESL57 is quoted as nominal 16ohm, with a minimum of 1.7 ohms.

1.7ohms at 18kHz, only.
I used to run 2 pairs, 2 in series each side, which made things a little
easier.

Now I have (stored away somewhere) a pair of ESL-63s, plus a scrap one
for parts, that are a pretty constant 8 ohms which comes across as
pretty much purely resistive.
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.
--scott

Presumably behaves OK with the recommended Classe amps , which one could
presumably afford if one could afford the speakers.

Sorry Jack-off, I don't have the B&W , just my old KEF R107s, Tannoy
DMT-12s, and some home-made LS3-5As. Unless you count my PA stuff.

geoff

[[email protected]]

On Monday, May 1, 2017 at 6:08:01 PM UTC-4, geoff wrote:
On 2/05/2017 1:42 a.m., Scott Dorsey wrote:
geoff wrote:
The Quad ESL57 is quoted as nominal 16ohm, with a minimum of 1.7 ohms.

1.7ohms at 18kHz, only.
I used to run 2 pairs, 2 in series each side, which made things a little
easier.

Now I have (stored away somewhere) a pair of ESL-63s, plus a scrap one
for parts, that are a pretty constant 8 ohms which comes across as
pretty much purely resistive.
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.
--scott

Presumably behaves OK with the recommended Classe amps , which one could
presumably afford if one could afford the speakers.

Sorry Jack-off, I don't have the B&W , just my old KEF R107s

Whoa! They have *gasp* gold plated terminals! I bet that makes them sound great!!

, Tannoy
DMT-12s, and some home-made LS3-5As. Unless you count my PA stuff.

geoff

Decades ago, hi-fi magazine, Altec Lansing had HUGE speakers, shown in a home, they were HUGE. You know why? Housed a 30 inch woofer!! Required like 100W min. just to move the damn things! :-)

I'll stick with my Sony headphone, if you recommended, you did well, you guys can speak about your speakers and voice about your coils!

Jack

[[email protected]]

On Monday, May 1, 2017 at 2:14:33 PM UTC-4, Don Pearce wrote:
On 1 May 2017 09:42:44 -0400, (Scott Dorsey) wrote:

geoff wrote:
The Quad ESL57 is quoted as nominal 16ohm, with a minimum of 1.7 ohms.

1.7ohms at 18kHz, only.

I used to run 2 pairs, 2 in series each side, which made things a little
easier.

Now I have (stored away somewhere) a pair of ESL-63s, plus a scrap one
for parts, that are a pretty constant 8 ohms which comes across as
pretty much purely resistive.

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.
--scott

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.

Hmmm? So we take(12 (high Z) + 3 (low Z)) / 2 = 7.5 Ohms average!!

Jack


d

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[Phil Allison[_4_]]

Scott Dorsey wrote:

geoff


Now I have (stored away somewhere) a pair of ESL-63s, plus a scrap one
for parts, that are a pretty constant 8 ohms which comes across as
pretty much purely resistive.

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.


** Completely benign impedance curve:

http://user.tninet.se/~vhw129w/mt_au..._impedance.jpg


The triac protection system could be triggerd with amps over 100wpc and Quad advised NOT using an amplifier that did not have adequate current limiting.


...... Phil

[PStamler]

So that B&W hits a minimum impedance of 3 ohms at around 650Hz. That could be a nasty load to drive.

QUAD ESL-63s are famous for being easy loads to drive, unlike the original QUAD ESL, now dubbed the ESL-57, which was essentially a shunt capacitor. As Scott said, it could provoke oscillation in marginally-stable amplifiers.

To go back to the original poster's question: what you need to understand is that impedances in parallel add *down*, not up. The formula is, for two speakers A & B hooked up in parallel:

1/total = 1/A + 1/B

So let's say speakers A & B are 4 ohms and 6 ohms respectively, 1/A = 0.25, 1/6 = 0.166..., . Add those two fractions, and you get 0.41666... Since 1/total equals that, the total will be 1/0.416666..., or 2.4 ohms. which can cause problems on most power amplifiers.

What that somewhat mysterious graphic on the back of his amplifier means is that if he connects only one speaker it can have a nominal impedance as low as 4 ohms (it can be higher, but 4 ohms is a minimum), but if he connects more than one speaker, each has to be a minimum of 8 ohms (two of those in parallel work out to 4 ohms total). Which implies a not-super-robust power amplifier in his receiver, which is par for the course for consumer gear.

There's a lot more complexity than that (which other posters have alluded to), but that's the basic story.

Peace,
Paul

[Phil Allison[_4_]]

PStamler wrote:



QUAD ESL-63s are famous for being easy loads to drive, unlike the
original QUAD ESL, now dubbed the ESL-57, which was essentially a shunt
capacitor.

** Hardly.

The impedance is 14 ohms out to 5kHz then drops to 1.7 ohms at 17kHz rising sharply above. It's actually a very easy load to drive.

The issue is with large sub-sonic frequencies that overdrive and saturate the input transformer. This will instantly fry output transistors in an unprotected amplifier.

Used to be a problem in the vinyl era, not so much now.


...... Phil

[[email protected]]

The issue is with large sub-sonic frequencies that overdrive and saturate the input transformer. This will instantly fry output transistors in an unprotected amplifier.

Used to be a problem in the vinyl era, not so much now.


..... Phil

input transformer?

the speakers had a transformer?

m

[Scott Dorsey]

Phil Allison wrote:
Scott Dorsey wrote:

geoff


Now I have (stored away somewhere) a pair of ESL-63s, plus a scrap one
for parts, that are a pretty constant 8 ohms which comes across as
pretty much purely resistive.

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.


** Completely benign impedance curve:

http://user.tninet.se/~vhw129w/mt_au..._impedance.jpg

This is the absolute value. What causes the problem with poorly designed
amplifiers is the reactive part. (Which is still pretty benign, it just
runs to the other side of the plane a bit.)

The triac protection system could be triggerd with amps over 100wpc and Quad advised NOT using an amplifier that did not have adequate current limiting.

Sadly, the ST120 has no triac protection, no thermal runaway protection,
really no protection at all. The only thing that keeps it under control
with a capacitive load is the series inductor on the output (which quite
unfortunately is wrapped around a power supply capacitor to save space
which is another issue).
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

wrote:

The issue is with large sub-sonic frequencies that overdrive and saturate the input transformer. This will instantly fry output transistors in an unprotected amplifier.

Used to be a problem in the vinyl era, not so much now.

input transformer?

the speakers had a transformer?

Yes, step-up transformer.... the electrostatic element is a big capacitor
whose plates move back and forth with charge because they attract and repel.
In order to do this on a large scale you need comparatively high voltages,
so there's a step up transformer and a bias supply inside the box.

(The transformer reflects the capacitive load back to the amplifier, which
sees the element shunt capacitance divided by the transformer turns ratio,
and that's why these speakers are difficult to drive for typical hi-fi amps.)

Now.... if you're thinking about this at all, you'll think "why do I have
a step-down transformer on my tube amplifier and then a step-up transformer
in the amp? Why not just use a high voltage transmitting tube as a final
and drive the electrostat directly off the plate?" A number of people have
had that idea over the years, most notably Acoustat, and they found that
overload protection was a difficult issue.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[[email protected]]

In the case of consumer speakers,
when the impedance is labeled on
the back, is it the lowest measurement,
or an average? Does such procedure
vary by mfg?

[[email protected]]

On Monday, May 1, 2017 at 8:01:06 PM UTC-4, Phil Allison wrote:
Scott Dorsey wrote:

geoff


Now I have (stored away somewhere) a pair of ESL-63s, plus a scrap one
for parts, that are a pretty constant 8 ohms which comes across as
pretty much purely resistive.

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.


** Completely benign impedance curve:

http://user.tninet.se/~vhw129w/mt_au..._impedance.jpg


The triac protection system could be triggerd with amps over 100wpc and Quad advised NOT using an amplifier that did not have adequate current limiting.

Triac!!?? Haven't heard about those in ages!!!! Old tech stuff.

Jack



..... Phil

[Scott Dorsey]

In article ,
wrote:
In the case of consumer speakers,
when the impedance is labeled on
the back, is it the lowest measurement,
or an average? Does such procedure
vary by mfg?

It is a "nominal" value pulled out of someone in the marketing department's
rear end. It bears little connection to actual measurements.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Don Pearce[_3_]]

On 2 May 2017 14:06:03 -0400, (Scott Dorsey) wrote:

In article ,
wrote:
In the case of consumer speakers,
when the impedance is labeled on
the back, is it the lowest measurement,
or an average? Does such procedure
vary by mfg?

It is a "nominal" value pulled out of someone in the marketing department's
rear end. It bears little connection to actual measurements.
--scott

Actually I know the procedure for defining speaker impedance. Think of
a number between 1 and 5. Add your birthday and the number of socks in
your sock drawer. Subtract 13.....


d

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[geoff]

On 3/05/2017 4:59 AM, wrote:
In the case of consumer speakers,
when the impedance is labeled on
the back, is it the lowest measurement,
or an average? Does such procedure
vary by mfg?



"Nominal', and very nominal at that. Describes the amplifier output Z
that *should* be OK with the speake.

geoff

[Scott Dorsey]

Don Pearce wrote:
On 2 May 2017 14:06:03 -0400, (Scott Dorsey) wrote:
In article ,
wrote:
In the case of consumer speakers,
when the impedance is labeled on
the back, is it the lowest measurement,
or an average? Does such procedure
vary by mfg?

It is a "nominal" value pulled out of someone in the marketing department's
rear end. It bears little connection to actual measurements.

Actually I know the procedure for defining speaker impedance. Think of
a number between 1 and 5. Add your birthday and the number of socks in
your sock drawer. Subtract 13.....

Likely that's where consumer speaker power "ratings" come from.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[[email protected]]

On Tuesday, May 2, 2017 at 2:51:24 PM UTC-4, Don Pearce wrote:
On 2 May 2017 14:06:03 -0400, km (Scott Dorsey) wrote:

In article ,
tl.com wrote:
In the case of consumer speakers,
when the impedance is labeled on
the back, is it the lowest measurement,
or an average? Does such procedure
vary by mfg?

It is a "nominal" value pulled out of someone in the marketing department's
rear end. It bears little connection to actual measurements.
--scott

Actually I know the procedure for defining speaker impedance. Think of
a number between 1 and 5. Add your birthday and the number of socks in
your sock drawer. Subtract 13.....


d

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I ask a serious question on here
and all I get is a bunch of silly
answers.

[[email protected]]

Went to computer show. Found new JVC Speakers, like $10. Complete with bass & treble controls. DC supply is massive. Bottom line, they are nice. Wish I bought a dozen!

Jack

[Phil Allison[_4_]]

Scott Dorsey wrote:

Phil Allison




Now I have (stored away somewhere) a pair of ESL-63s, plus a scrap one
for parts, that are a pretty constant 8 ohms which comes across as
pretty much purely resistive.

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.


** Completely benign impedance curve:

http://user.tninet.se/~vhw129w/mt_au..._impedance.jpg

This is the absolute value. What causes the problem with poorly designed
amplifiers is the reactive part. (Which is still pretty benign, it just
runs to the other side of the plane a bit.)


** Sorry, that is gobbledegook.

The impedance never drops below 4 ohms and is rising above 20kHz.

The low end rise is just like a woofer in a sealed box.

So there is no stability or other amp related issue.



The triac protection system could be triggerd with amps over 100wpc
and Quad advised NOT using an amplifier that did not have adequate
current limiting.

Sadly, the ST120 has no triac protection, no thermal runaway protection,
really no protection at all. The only thing that keeps it under control
with a capacitive load is the series inductor on the output (which quite
unfortunately is wrapped around a power supply capacitor to save space
which is another issue).


** Quad ESLs are not capacitive loads, that idea is a silly myth that probably derives form the once common practice of testing amp stability by connecting a 2uF film cap across the output while looking at a 10kHz square wave on a scope.

No real speaker anything like a 2uF cap.



..... Phil

[Phil Allison[_4_]]

Scott Dorsey wrote:



input transformer?

the speakers had a transformer?

Yes, step-up transformer.... the electrostatic element is a big capacitor
whose plates move back and forth with charge because they attract and repel.



** Well, that's the popular misconception.

The driven plates of an ESL are always *fixed* in place.

The high DC voltage is applied to the plastic diaphragm which crucially is coated in a HIGH resistance material.

The presence of the moving diaphragm acts as a load on the capacitor formed by the fixed drive plates - making it very lossy.

The famous Quad ESL63 ( and later marks) uses a multi section delay line operating at high voltage which has the additional effect of ELIMINATING the capacitance effect at high frequencies seen with other designs.

It presents a near resistive load over the mid and high frequency ranges.

http://user.tninet.se/~vhw129w/mt_au..._impedance.jpg


.... Phil

[geoff]

On 3/05/2017 8:48 PM, Phil Allison wrote:


The famous Quad ESL63 ( and later marks) uses a multi section delay
line operating at high voltage which has the additional effect of
ELIMINATING the capacitance effect at high frequencies seen with
other designs.

It presents a near resistive load over the mid and high frequency
ranges.

And simulates a point-source.

geoff

[Phil Allison[_4_]]

geoff wrote:

Phil Allison wrote:


The famous Quad ESL63 ( and later marks) uses a multi section delay
line operating at high voltage which has the additional effect of
ELIMINATING the capacitance effect at high frequencies seen with
other designs.

It presents a near resistive load over the mid and high frequency
ranges.

And simulates a point-source.




** Indeed, that is the main purpose.

A smallish source positioned about 30cm behind the geometric centre of the panel. The net result is, very arguably, the world's most accurate loudspeaker.

Not that anybody really cares ...




...... Phil

[Scott Dorsey]

wrote:

I ask a serious question on here
and all I get is a bunch of silly
answers.

Unfortunately, they are the correct ones. Because consumer electronics
manufacturers don't take their customers seriously and they don't provide
actual measurements of products. Instead, they provide numbers that are
frequently worse than no specifications at all.

I like measurements and specifications. What I don't like are numbers that
are supposed to look like measurements and specifications but actually are not.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Scott Dorsey]

Phil Allison wrote:
Scott Dorsey wrote:
** Completely benign impedance curve:

http://user.tninet.se/~vhw129w/mt_au..._impedance.jpg

This is the absolute value. What causes the problem with poorly designed
amplifiers is the reactive part. (Which is still pretty benign, it just
runs to the other side of the plane a bit.)

** Sorry, that is gobbledegook.

The impedance never drops below 4 ohms and is rising above 20kHz.

The impedance is a complex number. You are showing the absolute value of it,
or if you prefer to call it that, the magnitude.

The impedance never drops below 4 ohms, yes. But what your plot does not
show is that it is capacitive in much of the audio band.

** Quad ESLs are not capacitive loads, that idea is a silly myth that probably derives form the once common practice of testing amp stability by connecting a 2uF film cap across the output while looking at a 10kHz square wave on a scope.

No real speaker anything like a 2uF cap.

Show me a complex impedance plot, then.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Phil Allison[_4_]]

Scott Dorsey wrote:
Phil Allison


** Completely benign impedance curve:

http://user.tninet.se/~vhw129w/mt_au..._impedance.jpg

This is the absolute value. What causes the problem with poorly designed
amplifiers is the reactive part. (Which is still pretty benign, it just
runs to the other side of the plane a bit.)

** Sorry, that is gobbledegook.

The impedance never drops below 4 ohms and is rising above 20kHz.


The impedance is a complex number. You are showing the absolute value of it,
or if you prefer to call it that, the magnitude.

The impedance never drops below 4 ohms, yes. But what your plot does not
show is that it is capacitive in much of the audio band.


** It does not show that simply because it is not true.

FYI:

A capacitive load has a constantly falling impedance with frequency, dropping to a very low value at supersonic frequencies.



** Quad ESLs are not capacitive loads, that idea is a silly myth
that probably derives form the once common practice of testing
amp stability by connecting a 2uF film cap across the output while
looking at a 10kHz square wave on a scope.

No real speaker is anything like a 2uF cap.


Show me a complex impedance plot, then.



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

No thanks.



..... Phil

[[email protected]]

On Wednesday, May 3, 2017 at 5:51:26 PM UTC-4, Phil Allison wrote:
Scott Dorsey wrote:
Phil Allison


** Completely benign impedance curve:

http://user.tninet.se/~vhw129w/mt_au..._impedance.jpg

This is the absolute value. What causes the problem with poorly designed
amplifiers is the reactive part. (Which is still pretty benign, it just
runs to the other side of the plane a bit.)

** Sorry, that is gobbledegook.

The impedance never drops below 4 ohms and is rising above 20kHz.


The impedance is a complex number. You are showing the absolute value of it,
or if you prefer to call it that, the magnitude.

The impedance never drops below 4 ohms, yes. But what your plot does not
show is that it is capacitive in much of the audio band.


** It does not show that simply because it is not true.

FYI:

A capacitive load has a constantly falling impedance with frequency, dropping to a very low value at supersonic frequencies.



** Quad ESLs are not capacitive loads, that idea is a silly myth
that probably derives form the once common practice of testing
amp stability by connecting a 2uF film cap across the output while
looking at a 10kHz square wave on a scope.

No real speaker is anything like a 2uF cap.


Show me a complex impedance plot, then.



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

Darn, Phil slapping Scott around.

Love it! :-)

Jack

No thanks.



.... Phil

[Scott Dorsey]

Phil Allison wrote:

A capacitive load has a constantly falling impedance with frequency, dropping to a very low value at supersonic frequencies.

That is a tremendous, tremendous oversimplification.

It's not unusual for a load to be mostly resistive at one frequency,
mostly capacitive at another, and mostly inductive at a third. This
isn't a simple lumped-sum device.

Again, check out an actual plot of the Quads, they are very interesting loads.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Phil Allison[_4_]]

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

[Scott Dorsey]

Phil Allison wrote:
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.
Agreed, and even in the simple case of just resistive damping it's a big
deal.

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.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Phil Allison[_4_]]

Scott Dorsey wrote:

Phil Allison

A capacitive load has a constantly falling impedance with
frequency, dropping to a very low value at supersonic frequencies.

That is a tremendous, tremendous oversimplification.


** No, it is a simple fact.



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.

FYI:

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. "

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

Clearly, the ESL63 does not do anything like this.



..... Phil

[Scott Dorsey]

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.

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.

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.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[geoff]

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.
--scott

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

geoff

[Phil Allison[_4_]]

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

[Scott Dorsey]

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
--
"C'est un Nagra. C'est suisse, et tres, tres precis."