Eiron wrote:



Because of the Australian fashion for designing speakers with impedances
that drop to zero at the crossover frequencies.



** Not afraid of making a gross overstatement - are you ?

FYI:

There are far more examples of bad loudspeaker x-over design from the USA.

How about the once popular Acoustic Research AR11 model ??

http://www.classicspeakerpages.net/I...1251408626.jpg

All three drivers used are 4 ohms types with the dome mid and tweeter operating in *parallel* over the range above 2kHz - making the impedance 2 to 2.5 ohms in that range.



..... Phil

In article , Trevor Wilson
wrote:

**This one:

http://me-au.com/me850data2.jpg

It will even survive the crowbar protection system (until that
protection system is destroyed).

FWIW The Armstrong 732 is also "safe" for this... in the sense that the
amplifier will survive driving the 63/57 beyond their limits. Afraid I did
once set fire to a 57 when testing the 732. The amp was fine, but Quad were
somewhat surprised by the state of the 57 when I sent it for repair.

But I do agree with Phil's general point. It can often be quite hard to use
published specs for such matters. That's why "prohibiting" giving details
seems a really weird idea. It made sense to mandate how the 'rated' power
should be measured and specified. But it doesn't make sense to try and
'ban' any further details being given in addition.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
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Audio Misc http://www.audiomisc.co.uk/index.html

In article , Don Pearce
wrote:

Why would anyone design that amplifier and say it is for music? One of
the most pointless specs I've ever read. You're just ****ing your money
away if you buy that.

Remember that some of us had to design amps in the era of some really
'demanding' speaker loadings like the old maggies. The problem became that
some speakers needed very high outputs into nastly loadings whilst others
were vulnerable. Some people using some speakers will want an amp that
would destroy another speaker. In the end, you have to choose what is
appropriate. This is why detailed info for users is important.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

On 5/05/2016 5:37 PM, Phil Allison wrote:
Eiron wrote:



Because of the Australian fashion for designing speakers with impedances
that drop to zero at the crossover frequencies.



** Not afraid of making a gross overstatement - are you ?

FYI:

There are far more examples of bad loudspeaker x-over design from the USA.

How about the once popular Acoustic Research AR11 model ??

http://www.classicspeakerpages.net/I...1251408626.jpg

All three drivers used are 4 ohms types with the dome mid and tweeter operating in *parallel* over the range above 2kHz - making the impedance 2 to 2.5 ohms in that range.


**Or the Infinty 4.5. Two 4 Ohm voice coils in parallel, with another
pair of 2 Ohm voice coils operating in the low bass in parallel with
them. Back in the late 1970s, I was called in to investigate why the
speakers were destroying so many big amplifiers. I guess the 0.75 Ohm
load in the bass region had a lot to do with it. Even Peter Stein's
ME100 only lasted a few weeks (which is a lot longer than any Phase
Linear did), causing him to revise the VI limiting in that model to
cope. Apparently, the current limiting transistors over-dissipated, then
failed, leading to the eventual destruction of the output devices. Peter
always ensured his big amps could deal with such loads from that time on.


--
Trevor Wilson
www.rageaudio.com.au

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On 5/05/2016 5:13 PM, Phil Allison wrote:
Trevor Wilson wrote:

Phil Allison wrote:



** Yes, reactive load and low impedance behaviour is often important
to know - but to this day requires test results that very few makers
publish.

Using only published information, can you say which modern amps are
safe to use with a Quad ESL57 or 63?


**This one:

http://me-au.com/me850data2.jpg

It will even survive the crowbar protection system (until that
protection system is destroyed).


** Using the advice published by Quad, that old ME model is not suitable for use with either Quad ESL. Too many volts for the '57 and too many amps for the '63.

Quad advise the '57 is safe up to 33V peak ( 68 watts at 8 ohms) and the '63 should only be use with amplifiers that have VI limiting.

In both cases, the amplifier should also have good sub-sonic filtering - not flat response down to DC !!!



**Ah, I misinterpreted the term: "safe". I thought you indicated that
the amplifier could be damaged. That said, sub-sonic filtering can
easily be placed on the preamp and the ME850 has excellent VI limiting.
It is quite difficult to damage. But yes, I would never use the ME850
with the ESL57, but it sounds astonishingly good on the ESL63. I've
never damaged a pair, nor triggered the protection system (on the
speakers) using the pairing and I've done so many times (I used to sell
the ESL63).


--
Trevor Wilson
www.rageaudio.com.au

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On 5/05/2016 4:44 PM, Eiron wrote:
On 05/05/2016 07:17, Don Pearce wrote:
On Thu, 5 May 2016 15:12:49 +1000, Trevor Wilson
wrote:


http://me-au.com/me850data2.jpg

It will even survive the crowbar protection system (until that
protection system is destroyed).

Why would anyone design that amplifier and say it is for music? One of
the most pointless specs I've ever read. You're just ****ing your
money away if you buy that.

Because of the Australian fashion for designing speakers with impedances
that drop to zero at the crossover frequencies.


**As PA has indicated, that type of speaker is commonly manufactured by
Americans, not Australians. Here are the impedance plots of two old
American speakers:

Infinity Kappa 9:

http://www.rageaudio.com.au/modules/...656_kappa9.jpg

Acoustat (I can't recall the model - Spectra something-or-other):

http://www.rageaudio.com.au/modules/...05452_accu.jpg

I ran the impedance curve of the infamous Infinity 4.5 many years ago,
but it was long before computerised test equipment and the curve
(primitive that it was) has long since vanished. The impedance fell to
around 0.75 Ohms in the bass region. I'll dig out the crossover
schematic provide a link. Be very careful when you examine it. Make
certain you are sitting down with a nice cool beverage (alcoholic). It
is a truly scary stuff.


--
Trevor Wilson
www.rageaudio.com.au

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In article , Trevor Wilson
wrote:
**Ah, I misinterpreted the term: "safe". I thought you indicated that
the amplifier could be damaged. That said, sub-sonic filtering can
easily be placed on the preamp and the ME850 has excellent VI limiting.
It is quite difficult to damage. But yes, I would never use the ME850
with the ESL57, but it sounds astonishingly good on the ESL63. I've
never damaged a pair, nor triggered the protection system (on the
speakers) using the pairing and I've done so many times (I used to sell
the ESL63).

The above was alwas a dilemma for me. I've happily used 732s for decades
without any harm to a succession of ESLs or the amps. And I think the
combination sounds better than using a quad amp limited as relevant. But
I've been far from sure the combination would be 'safe' for others unless
they knew what they were doing and could avoid driving the speakers too
hard.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

In article , Trevor Wilson
wrote:
I ran the impedance curve of the infamous Infinity 4.5 many years ago,
but it was long before computerised test equipment and the curve
(primitive that it was) has long since vanished. The impedance fell to
around 0.75 Ohms in the bass region. I'll dig out the crossover
schematic provide a link. Be very careful when you examine it. Make
certain you are sitting down with a nice cool beverage (alcoholic). It
is a truly scary stuff.

This was the kind of dilemma faced by amp designers of the period. A
variety of highly regarded ( or at least highly hyped! ;- ) 'super
speakers' appeared. Some needed a hell of an amplifier to drive them
because they were inefficient had awful impedance behaviour. Yet others
could be toasted by an amp designed to drive the awkward squad. Limiting
the amp then limited its use.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

On Thu, 05 May 2016 09:14:27 +0100, Jim Lesurf
wrote:

In article , Don Pearce
wrote:

Why would anyone design that amplifier and say it is for music? One of
the most pointless specs I've ever read. You're just ****ing your money
away if you buy that.

Remember that some of us had to design amps in the era of some really
'demanding' speaker loadings like the old maggies. The problem became that
some speakers needed very high outputs into nastly loadings whilst others
were vulnerable. Some people using some speakers will want an amp that
would destroy another speaker. In the end, you have to choose what is
appropriate. This is why detailed info for users is important.

Jim

It isn't just the basic spec, but things like the power supply,
designed clearly to permit full power sine wave drive, ignoring the
peaky nature of music (then at any rate - maybe they anticipated the
highly-compressed pop of today).

d

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In article , Don Pearce
wrote:

It isn't just the basic spec, but things like the power supply, designed
clearly to permit full power sine wave drive, ignoring the peaky nature
of music (then at any rate - maybe they anticipated the
highly-compressed pop of today).

Agreed. FWIW being able to deliver high peaks was why I avoided using a
stabilised PSU for a power amp. And - coming back to the idea of
'prohibiting' anything other than the sinewave rated power - that mean an
amp that had to be 'rated' as 200wpc but could play much bigger peaks Some
measure of 'dynamic headroom' is clearly useful, therefore.

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html