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On Sun, 2 Jan 2005 19:20:45 +0200, "Iain M Churches"
wrote:

"Jim Lesurf" wrote in message
...
In article , Iain M Churches
wrote:

You will find that all the above makers, and the great majority of the
others, conform to IEC/EN/BS EN 60268-5

No, the 'great majority' of makers do not in fact subscribe to that
standard. Do not attempt to translate the standards of the
professional market to domestic products.

It stipulates that impedance may fall to 80% of the nominal rated value,
i.e. 6.4 ohms for an '8 ohm' product. A manufacturer may specify the
nominal impedance

There is no limit on the amount that it may exceed the rated value.
Normally, there would be no point in such a limit, because the
loudspeaker gives its designed frequency response with constant applied
voltage. The impedance is relevant only for determining whether the
loudspeaker can demand more current than the amplifier can supply.

Alas, the problem is slightly different....

I'd agree that when makers like B&W, etc, specify nominal speaker
impedances they will follow the standards. The snag is that this does notr
mean that all speakers are '8 Ohm'. Nor does it mean that people only buy
'8 Ohm' speakers for domestic use.

The critical factor here is not the nominal impedance, which can be anything the
manufacturer states it to be, but the deviation in a downward direction
from that nominal impedance.

And the vast majority of domestic speakers in 2005 are *not* nominally
8-ohm, although *amplifier* manufacturers continue to assume this as a
reference, allowing them to cut corners in the power supply.

Indeed, many reviews in magazines, and I
suspect sales/listening sessions in shops, do not mention impedance or
give
useful values.

Caveat Emptor:-)
This explains why Tannoy, JBL, B+W have a professional division. You
can bet your bottom Euro that the products they produce for professional
use meet the standard.

Quite so, but those products are in almost all cases not supplied to
the consumer market, and are hence irrelevant to this newgroup.

Hence an undetermined number of people will be buying and using speakers
for domestic use which would not be classificiable as '8 Ohms' and they
have no idea of this, nor will it have occurred to them as an issue.

Then one would have thought that the onus would be upon the hifi press
to dig a little deeper in review. Professional magazines such as Studio Sound
certainly do this.

One might have thought that we should all be Lottery winners......

You'll find that the odds are about the same.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

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"Stewart Pinkerton" wrote in message
...
On Sun, 2 Jan 2005 19:20:45 +0200, "Iain M Churches"
wrote:

"Jim Lesurf" wrote in message
...
In article , Iain M Churches
wrote:

You will find that all the above makers, and the great majority of the
others, conform to IEC/EN/BS EN 60268-5

No, the 'great majority' of makers do not in fact subscribe to that
standard. Do not attempt to translate the standards of the
professional market to domestic products.

I am sorry Stewart, but your statement is incorrect.
The recommendation is, and always has been, for *all* loudspeakers
not just professional products, but as the list carefully prepared and
posted by Jim elsewhere in this thread clearly shows, manufacturers
who build professional monitors and also loudspeakers intended for
domestic use, adhere to the recommendation.
The Tannoy M1 is a good example of a speaker often found in studios
and used to give the client some idea what his recording may sound
like in a domestic, end user environment.



The critical factor here is not the nominal impedance, which can be
anything the manufacturer states it to be, but the deviation in a
downward direction from that nominal impedance.


Caveat Emptor:-)
This explains why Tannoy, JBL, B+W have a professional division. You
can bet your bottom Euro that the products they produce for professional
use meet the standard.

Quite so, but those products are in almost all cases not supplied to
the consumer market.

Oh, but they are. You will find as many pairs of B+W Nautilus in use
in the domestic environment as in studios. The same goes for Tannoy and
JBL products, and also the ubiquitous Genelec (which are active, and so
perhaps are not totally relevant to this discussion, although they do
represent a speaker found in both professional and domestic
applications)

Hence an undetermined number of people will be buying and using speakers
for domestic use which would not be classificiable as '8 Ohms' and they
have no idea of this, nor will it have occurred to them as an issue.

Then one would have thought that the onus would be upon the hifi press
to dig a little deeper in review. Professional magazines such as Studio
Sound certainly do this.

One might have thought that we should all be Lottery winners......

????

As Jim points out elsewhere, it may be that dealers who sell
loudspeakers for the domestic market are not aware of the
impedance issue, and the buyers either don't know or don't care.

This may well be a subject on which the hifi press should play a
much more informative role. A technical writer for a magazine here in
Scandinavia tells me that a magzine is only as good as the readership
requires it to be. So in the case of the UK hifi magazines maybe a large
number of "Letters to the Editor" are required?

Domestic hifi certainly seems to be a minefield:-)
I am thankful to be working in an AES/EBU digital,
and balanced line XLR analogue environment where
(to misquote Gilbert and Sullivan):
"Things are always what they seem"

:-)))

Iain

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In article , Iain M Churches
wrote:

"Jim Lesurf" wrote in message
...
In article , Iain M Churches
wrote:


I'd agree that when makers like B&W, etc, specify nominal speaker
impedances they will follow the standards. The snag is that this does
notr mean that all speakers are '8 Ohm'. Nor does it mean that people
only buy '8 Ohm' speakers for domestic use.

The critical factor here is not the nominal impedance, which can be
anything the manufacturer states it to be, but the deviation in a
downward direction from that nominal impedance.

I would put it slightly differently. :-)

The critical factor seems to me to be the extent to which the speaker
impedance variations may cause a change in the frequency/phase response.
(And possibly other things like the distortion.)

Hence we have to compare the variation in speaker impedance with the actual
(or probable) amp (and lead) series impedance.

To show what this means, take two examples of a speaker whose impedance
varies by +50/-10 percent from a nominal value, combined with two examplles
of amp+cables with different o/p impedance.

LS1) "16 Ohm" speaker. Max 24.0 Min 14.4

LS2) "4 Ohm" speaker. Max 6.0 Min 3.6

Amp1) 0.5 Ohm o/p impedance

Amp2) 0.05 Ohm o/p impedance

For each possible combination we get a range of interaction loss which is
as follows:

LS1 and Amp 1 -0.18 dB to -0.30 dB i.e. response variation 0.12 dB

LS2 and Amp1 -0.69 dB to -1.13 dB = variation of 0.44 dB

LS1 and Amp2 -0.03 dB to -0.02 dB = variation of 0.01 dB

LS2 and Amp2 -0.07 dB to -0.12 dB = variation of 0.05 dB

Did the above quite quickly with a spreadsheet and typed them in above, so
I may have made a numerical error or typo somewhere! However I made up the
amps and speakers purely for the sake of illustration, so the exact
resulting values aren't important, What matters is that a given fractional
or percentage variation in speaker impedance has an effect which is then
scaled by the relative values of the speaker impedance and the amp o/p
impedance. Hence I'd say that it is not the deviation of the speaker
impedance down from its nominal value that is critical, but this variation
down to a minimum value compared with the amp's o/p impedance.


Indeed, many reviews in magazines, and I suspect sales/listening
sessions in shops, do not mention impedance or give useful values.

Caveat Emptor:-) This explains why Tannoy, JBL, B+W have a professional
division. You can bet your bottom Euro that the products they produce
for professional use meet the standard.

Alas, the problem is that this can't be assumed for domestic audio.

I feel it is somewhat unfair on domestic customers to expect them to be
aware of this when the magazines never make an issue of it. Indeed, they
often give no info that would allow the reader to assess this for a
specific speaker even if they are aware of the problem and know the o/p
impedance of their power amps. (That said, how many people even reading
this newsgroup know the complex o/p impedance of the power amps they are
using as a function of frequency?)

OK, sometimes a magazine comments that a speaker is a 'difficult' load, or
that it is low impedance. But the way this is presented is generally in
terms of implying the amp has to have a suitable current capability.
However this is not the same as the amp having a low output impedance.



Hence an undetermined number of people will be buying and using
speakers for domestic use which would not be classificiable as '8
Ohms' and they have no idea of this, nor will it have occurred to them
as an issue.

Then one would have thought that the onus would be upon the hifi press
to dig a little deeper in review. Professional magazines such as Studio
Sound certainly do this.

One would have thought so. :-) Alas, when reading the consumer magazines
you rapidly realise how useless many 'reviews' are. Many give no real data.
Others give plots and values, but no real explanations. Where you know
something about the items in question you will often also find errors of
fact or misleading/incorrect 'explanations'.

Having read your posting my curiousity got the better of me and I
looked through the reviews in a few issues of HFN. I chose these 'at
random' purely on the basis that they were the first few issues I
picked up. The following summarises the results I found in the reviews:

(snip)

Looking at the above we can see that many can be assumed to be '8
Ohms' according to the AES spec. However some reviews simply make a
statement which I assume just reports the maker's claim, so might be
incorrect or 'optimistic'. And some speakers either have a nominal
value of less that 8 Ohms stated, or have no nominal value given, but
have a min value below 6.4 Ohms.

Interestingly enough,. Tannoy, B+W and JBL all meet the requirements
relative to their specified nominal impedance.

Agreed. I don't think LS makers are breaking the specs/standards they
publish. Where a speaker would not meet an AES 8 Ohm spec, they do not
claim that it does. But alas this does not mean that whenever we encounter
a domestic speaker we can assume it is 8 Ohm - some clearly are not.


As indicated above, my personal concern here is not with professional
users and professional monitors. I expect in that situation those
involved will know the specs, and know what they are doing. I am,
however, much less confident about this for many domestic setups. My
main interest here in what effect this may have when people listen to
consumer domestic audio equipment at home.

Yes indeed. This makes in-depth review and evaluation from the popular
hifi press even more important.

Yes. Alas, all too often, this is what we do not get!

FWIW I have a back-collection domestic audio mags, and I would say that, in
general, the actual standards of reviewing were often better in the 1970's
than nowdays. There are some good writers still, who understand the
technical side and its relevance. But some 'reviews' are now little more
than "I liked it" comments which seem to be written with "I am being paid
by the page" in mind. Technical "howlers" also appear with depressing
regularity.

Alas, if most of those reading the magazines have no independently gained
knowledge of engineering or physics, they are not always in a position to
notice that they are not being given the information and understanding they
would find useful. Instead they are simply led into thinking "If 'X' likes
it and says so, it must be good" where 'X' is the relevant guru's name.
Argument by authority, not by evidence or understanding. :-/

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

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On Mon, 3 Jan 2005 11:19:53 +0200, "Iain M Churches"
wrote:


"Stewart Pinkerton" wrote in message
.. .
On Sun, 2 Jan 2005 19:20:45 +0200, "Iain M Churches"
wrote:

"Jim Lesurf" wrote in message
...
In article , Iain M Churches
wrote:

You will find that all the above makers, and the great majority of the
others, conform to IEC/EN/BS EN 60268-5

No, the 'great majority' of makers do not in fact subscribe to that
standard. Do not attempt to translate the standards of the
professional market to domestic products.

I am sorry Stewart, but your statement is incorrect.
The recommendation is, and always has been, for *all* loudspeakers
not just professional products,

Only if the manufacturers choose to adhere to this *voluntary*
standard. Besides, the real point is that there are *very* few modern
speakers which count as 8-ohm.

but as the list carefully prepared and
posted by Jim elsewhere in this thread clearly shows, manufacturers
who build professional monitors and also loudspeakers intended for
domestic use, adhere to the recommendation.

Sure, never argued - and they're mostly not 8-ohm nominal.

The Tannoy M1 is a good example of a speaker often found in studios
and used to give the client some idea what his recording may sound
like in a domestic, end user environment.

And the one normally used is the *active* version.

The critical factor here is not the nominal impedance, which can be
anything the manufacturer states it to be, but the deviation in a
downward direction from that nominal impedance.

Caveat Emptor:-)
This explains why Tannoy, JBL, B+W have a professional division. You
can bet your bottom Euro that the products they produce for professional
use meet the standard.

Quite so, but those products are in almost all cases not supplied to
the consumer market.

Oh, but they are. You will find as many pairs of B+W Nautilus in use
in the domestic environment as in studios.

That's because the Nautilus series are *domestic* speakers, of which
the largest models happen to be good enough for monitoring. You don't
build studio monitors with beautifully veneered cabinets! Further,
those are definitely *not* 8-ohm speakers, which was my point.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

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In article , Iain M Churches
wrote:

[snip]

This may well be a subject on which the hifi press should play a much
more informative role. A technical writer for a magazine here in
Scandinavia tells me that a magzine is only as good as the readership
requires it to be. So in the case of the UK hifi magazines maybe a
large number of "Letters to the Editor" are required?

FWIW I have in the past tried that route. I've also seen some of the
results when others do so. The snags a

1) Letters which carefully point out the errors or failures of
understanding of a 'well regarded contributor' may simply be ignored or
given a dismissive response by the editor - and not published.

2) When actually published, a 'critical' letter is often immediately
followed by a 'reaction' by the writer whose work is being criticised. This
may simply reject what has been written in the letter and make further
claims.

3) When something is published it may be 'edited' so as to omit some points
which you may feel are the crux of the critical comments.

FWIW both (1) and (3) have happened to me. And I have seen many instances
of (2) over the years.

Having worked as a designer of domestic kit in the past I have been aware
of (and sometimes involved in) 'behind the scenes' discussions that have
stemmed from factual errors in reviews - sometimes quite serious errors
that have a large impact on possible sales. Yet these also rarely see the
'light of day' in the relevant magazine in a form that would cause readers
to realise what had been going on hidden from their view...

Of course, when such errors boost sales, the makers are less likely to get
involved in demanding a correction. ;-

I have also known of cases where there has been 'unhealthy' relationships
between some reviewers and some writers/magazines.

So the problem is that what the magazines print is sometimes highly
'selective' and - until the internet - people found it hard to get around
this. I suspect if you chat to designers/makers of domestic kit who have
been around for long enough they would often give you similar comments
about the magazines.

Domestic hifi certainly seems to be a minefield:-)

To some extent it always has been a sort of "jewellery for boys". :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

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"Stewart Pinkerton" wrote in message
...
On Mon, 3 Jan 2005 11:19:53 +0200, "Iain M Churches"
wrote:
I am sorry Stewart, but your statement is incorrect.
The recommendation is, and always has been, for *all* loudspeakers
not just professional products,

Only if the manufacturers choose to adhere to this *voluntary*
standard.

??? Its a recommendation, like most of those made by the AES.

Besides, the real point is that there are *very* few modern
speakers which count as 8-ohm.

Please get a copy of IEC/EN/BS EN 60268-5 and read
it carefully for yourself. As has been stated many times, there
is no 8 Ohms standard. What we are concerned with is
deviation from a nominal impedance.


but as the list carefully prepared and
posted by Jim elsewhere in this thread clearly shows, manufacturers
who build professional monitors and also loudspeakers intended for
domestic use, adhere to the recommendation.

Sure, never argued - and they're mostly not 8-ohm nominal.

No-one ever suggested they we-) but they do adhere to
IEC/EN/BS EN 60268-5

That's because the Nautilus series are *domestic* speakers, of which
the largest models happen to be good enough for monitoring

You are probably not aware that Decca, who were closely involved
in their development and evaluation, bought the first production run
of twenty pairs of Nautilus long before they were available to the
general public. Their use for monitoring is often credited on the
inlay cards of Decca CD's.

You don't
build studio monitors with beautifully veneered cabinets!

You have clearly never seen an Eastlake or LEDE control room
You really must get out mo-)))

Further,
those are definitely *not* 8-ohm speakers, which was my point.

Please read IEC/EN/BS EN 60268-5 and try to get this
erroneous fixation with 8 Ohms out of your head.

Cordially,


Iain

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"Jim Lesurf" wrote in message
...

(huge snip for later deliberation)


Agreed. I don't think LS makers are breaking the specs/standards they
publish. Where a speaker would not meet an AES 8 Ohm spec, they do not
claim that it does. But alas this does not mean that whenever we encounter
a domestic speaker we can assume it is 8 Ohm - some clearly are not.

There is no 8 Ohm spec as such. The recommendation refers to the deviation
from the nominal impedance which is not fixed at 8 Ohms, so a speaker
manufacturer may choose a value at will.

You make a very valid point, also mentioned earlier by Stewart, that
amplifier manufacturers assume that their amplifiers will be terminated
with a loudspeaker of 8 Ohms nominal impedance,
which in the domestic sector seems often not to be the case.

My
main interest here in what effect this may have when people listen to
consumer domestic audio equipment at home.

Yes indeed. This makes in-depth review and evaluation from the popular
hifi press even more important.

Yes. Alas, all too often, this is what we do not get!


FWIW I have a back-collection domestic audio mags, and I would say that,
in
general, the actual standards of reviewing were often better in the 1970's
than nowdays. There are some good writers still, who understand the
technical side and its relevance. But some 'reviews' are now little more
than "I liked it" comments which seem to be written with "I am being paid
by the page" in mind. Technical "howlers" also appear with depressing
regularity.

Alas, if most of those reading the magazines have no independently gained
knowledge of engineering or physics, they are not always in a position to
notice that they are not being given the information and understanding
they
would find useful. Instead they are simply led into thinking "If 'X' likes
it and says so, it must be good" where 'X' is the relevant guru's name.
Argument by authority, not by evidence or understanding. :-/

But surely, for the sake of clarity, hi-fi magazines would wish to make
comparisons using a common set of statistics, comparing apples with
apples, and when asking loudspeaker manufacturers to submit
speakers for test or data for publication, would want to present
this data in a format which allows clear comparison.

Iain

Tube amplifiers
 

On Mon, 3 Jan 2005 15:16:08 +0200, "Iain M Churches"
wrote:

Please get a copy of IEC/EN/BS EN 60268-5 and read
it carefully for yourself. As has been stated many times, there
is no 8 Ohms standard. What we are concerned with is
deviation from a nominal impedance.

If you do a full vector measurement of a speaker in the complex plane,
you will see that the main part of the range from the upper bass
resonance to the point where the tweeter inductance starts running
away is a pretty good circle. The centre of that circle is typically
the "nominal" impedance of the speaker, even though the actual
impedance is nowhere near it at any point. You can't see this on a
normal rectangular plot, so without the full vector data it doesn't
seem to make much sense.

d

Pearce Consulting
http://www.pearce.uk.com

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In article , Iain M Churches
wrote:

"Jim Lesurf" wrote in message
...

(huge snip for later deliberation)


Agreed. I don't think LS makers are breaking the specs/standards they
publish. Where a speaker would not meet an AES 8 Ohm spec, they do not
claim that it does. But alas this does not mean that whenever we
encounter a domestic speaker we can assume it is 8 Ohm - some clearly
are not.

There is no 8 Ohm spec as such.

But there is an "AES 8 Ohm spec" when I am using that phrase to mean a
speaker which would accord with the spec you mention with a nominal quoted
value of 8 Ohms. I was however trying to keep my sentence short. :-)

The recommendation refers to the deviation from the nominal impedance
which is not fixed at 8 Ohms, so a speaker manufacturer may choose a
value at will.

Agreed. The snag being that in many cases no-one bothers to mention any
value at all. Hence leaving the (prospective/actual) buyer in ignorance of
the actual impedance properties of the speakers in question.


[snip my comments on the consumer audio mags]


But surely, for the sake of clarity, hi-fi magazines would wish to make
comparisons using a common set of statistics, comparing apples with
apples, and when asking loudspeaker manufacturers to submit speakers for
test or data for publication, would want to present this data in a
format which allows clear comparison.

Would be nice, wouldn't it. :-)

Alas, what they publish rarely considers what data might aid clear and
reliable comparisons from one review to another. Their methods, and what
they report, varies from one review to another. I'm afraid that a lot of
what appears is almost 'content free' in technical terms, and consists of
someone saying how they liked a given item.

One prime example was a set of 'reviews' in HFW which discussed the 'sound'
of various cables, but said nothing about the music used, the equipment
used, the room, etc. Hence even accepting that the perceived differences
were not imaginary we have no idea if anyone else would have come to the
same conclusions using their own ears, choice of music, etc, etc. These
reviews stuck in my mind as they didn't even give the name of the reviewer.
Hence you couldn't even try to guess on the basis of any prior experience
of how your own views of past comments by the writer agreed (or not) with
your own.

And if you want to know what sometimes passes for 'technical' reports in
the magazines, have a look at the 'Current dependent phase effects in
cables' example I have analysed in the 'analog and audio' section of the
'Scots Guide'. This was a set of articles reporting a startling new
'discovery' that would have revolutionised our understanding of cables.

Or it would have done it it hadn't been nonsense based on incorrectly
carried out and wildly misinterpreted measurements. :-)

The above was featured in Hi Fi News some years ago, and so far as I know,
no comment correcting or retracting it has ever appeared there. Yet I'd say
that overall Hi Fi News is of a much higher standard than the other
consumer audio magazines.

I've encountered similar technobabble in the mags on many occasions. e.g.
more cable nonsense, this time by Hawksford in HFN many years ago. I long
ago lost track of how often this happens - and in Electronics World as
well, which you might hope was better. :-/

Iain, I'd recommend you buy a few copies of mags like Hi Fi News and Hi Fi
World. You will find some useful info in them, but I fear you will be
puzzled/surprised by quite a lot of what you see! Not for the
faint-hearted, though... :-/

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

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In article , Don Pearce
wrote:
On Mon, 3 Jan 2005 15:16:08 +0200, "Iain M Churches"
wrote:

Please get a copy of IEC/EN/BS EN 60268-5 and read it carefully for
yourself. As has been stated many times, there is no 8 Ohms standard.
What we are concerned with is deviation from a nominal impedance.

If you do a full vector measurement of a speaker in the complex plane,
you will see that the main part of the range from the upper bass
resonance to the point where the tweeter inductance starts running away
is a pretty good circle. The centre of that circle is typically the
"nominal" impedance of the speaker, even though the actual impedance is
nowhere near it at any point. You can't see this on a normal rectangular
plot, so without the full vector data it doesn't seem to make much sense.

That's an interesting point. Maybe LS impedances and amp o/p impedance
should routinely be plotted on Smith charts in the reviews... :-)

The last Smith chart I can recall offhand in HFN is - I think - in one of
the Radford articles on his power amp kit back circa 1960-ish. Must check
to see if my memory is playing tricks on me!

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html