wrote in message
oups.com...
Every year or two CU tests popular speakers, and while most speakers
claim to be 8 ohms, CU finds most to measure 4 ohms. Although CU's
opinions should to be taken with a grain of salt, measurements are
measurments, and not opinions.

I don't read CU so I can't comment on their alleged "4 ohm" claim.
However, the key word is "nominal" that should precede "8 ohms".
Another point is minimum impedance. Nominally 8 ohms speakers can go
as low as 4 ohms at some frequencies, putting a bit of a strain on
cheap amplifiers that can't deliver the required current. Ideally,
you need the whole impedance vs. frequency graph, complete with phase
angle.
Cheers.
Roger

"Engineer" schreef in bericht
...
wrote in message
oups.com...
Every year or two CU tests popular speakers, and while most speakers
claim to be 8 ohms, CU finds most to measure 4 ohms. Although CU's
opinions should to be taken with a grain of salt, measurements are
measurments, and not opinions.

I don't read CU so I can't comment on their alleged "4 ohm" claim.
However, the key word is "nominal" that should precede "8 ohms".
Another point is minimum impedance. Nominally 8 ohms speakers can go
as low as 4 ohms at some frequencies, putting a bit of a strain on
cheap amplifiers that can't deliver the required current. Ideally,
you need the whole impedance vs. frequency graph, complete with phase
angle.
According to DIN standardisation the minimum impedance is 0.8 x nominal
impedance or the nominal impedance is 1.25 x the minimum impedance.
Consequently a speaker with a nominal impedance of 8 Ohm will have a minimum
impedance not lower than 6.4 Ohm and a 4 Ohm speaker 3.2 Ohm. Thus a speaker
with a minimum impedance of 4 Ohm has a nominal impedance of 1.25 x 4 Ohm =
5 Ohm and could never be an 8 Ohm speaker (according to DIN).
Ronald Berger

"r.berger" wrote in message
...
According to DIN standardisation the minimum impedance is 0.8 x nominal
impedance or the nominal impedance is 1.25 x the minimum impedance.
Consequently a speaker with a nominal impedance of 8 Ohm will have a
minimum
impedance not lower than 6.4 Ohm and a 4 Ohm speaker 3.2 Ohm. Thus a
speaker
with a minimum impedance of 4 Ohm has a nominal impedance of 1.25 x 4 Ohm
=
5 Ohm and could never be an 8 Ohm speaker (according to DIN).

Unfortunately I can't remember the last time I saw a speaker impedance
quoted according to DIN spec.
Maybe in Europe?

TonyP.

"TonyP" schreef in bericht
...

"r.berger" wrote in message
...
According to DIN standardisation the minimum impedance is 0.8 x nominal
impedance or the nominal impedance is 1.25 x the minimum impedance.
Consequently a speaker with a nominal impedance of 8 Ohm will have a
minimum
impedance not lower than 6.4 Ohm and a 4 Ohm speaker 3.2 Ohm. Thus a
speaker
with a minimum impedance of 4 Ohm has a nominal impedance of 1.25 x 4
Ohm
=
5 Ohm and could never be an 8 Ohm speaker (according to DIN).

Unfortunately I can't remember the last time I saw a speaker impedance
quoted according to DIN spec.
Maybe in Europe?

Yes, that is right.
The DIN standardisation for the nominal and minimum impedance is commonly
used in the European Union. But there are brands who apparently have their
"own
standards" which seem to vary to fit the design of the speaker. They seem to
think flattery will get them everywhere.
Most experienced European audio reviewers disapprove of this behaviour.
People who
know about this fiddling with figures experience it as misleading.
Ronald Berger.

spironical wrote ...
Every year or two CU tests popular speakers, and while most speakers claim
to be 8 ohms, CU finds most to measure 4 ohms. Although CU's opinions
should to be taken with a grain of salt, measurements are measurments, and
not opinions.

"8 ohms" sounds like the "nominal rating". While the speaker is
likely actually 8 ohms at some point, the impedance is never
uniform across the whole frequency spectrum. Nominal ratings
are just a guide to tell you what the design impedance was.

CU's measurement of 4 ohms sounds like the minimum impedance
at some (unspecified) frequency. This seems normal to me. Look
at any impedance curve and you can see that the variation between
minimum and maximum impedance can sometimes be 2x or even 4x.

The fact that CU is reporting the minimum impedance (without any
apparent explanation or context) is just indicative of their questionable
understanding, judgement, and reliability in technical areas.

No offense, but the notion that "measurements are measurements
not opinions" is not a safe world-view to subscribe to. ALWAYS
question how the measurements were made and what is the hidden
agenda of the person reporting them. In CU's case, reporting 4 ohms
for nominally-rated 8 ohm speakers makes them look like consumer
champions giving you valuable information worth paying for. While
in reality, they are reporting perfectly normal phenomenon.

"Richard Crowley" schreef in bericht
...
spironical wrote ...
Every year or two CU tests popular speakers, and while most speakers
claim
to be 8 ohms, CU finds most to measure 4 ohms. Although CU's opinions
should to be taken with a grain of salt, measurements are measurments,
and
not opinions.

"8 ohms" sounds like the "nominal rating". While the speaker is
likely actually 8 ohms at some point, the impedance is never
uniform across the whole frequency spectrum. Nominal ratings
are just a guide to tell you what the design impedance was.

CU's measurement of 4 ohms sounds like the minimum impedance
at some (unspecified) frequency. This seems normal to me. Look
at any impedance curve and you can see that the variation between
minimum and maximum impedance can sometimes be 2x or even 4x.

Or much more, according measurements I have taken.

The fact that CU is reporting the minimum impedance (without any
apparent explanation or context) is just indicative of their questionable
understanding, judgement, and reliability in technical areas.

No offense, but the notion that "measurements are measurements
not opinions" is not a safe world-view to subscribe to. ALWAYS
question how the measurements were made and what is the hidden
agenda of the person reporting them. In CU's case, reporting 4 ohms
for nominally-rated 8 ohm speakers makes them look like consumer
champions giving you valuable information worth paying for. While
in reality, they are reporting perfectly normal phenomenon.


I don't know CU but to me the minimum impedance is much more important than
the (fake) nominal impedances the brands state. Because along with the
electrical phase behaviour, this is one of the most important indications of
how difficult the speaker load will be for the (power/integrated)amplifier.
Many tube amplyfiers with very low damping factors in particular, the Audio
Note single ended amplifiers for instance, can be very sensitive for hefty
impedance curves with very low dips and tall highs. They will audibly affect
the frequency curve. High impedances are an easy load for tube amplifiers
and semi-conductor amplifiers as wel. I always try to design the minimum
impedance as high as possible. In my opinion it sounds better on many
amplifiers, including semi-conductor amplifiers.
Ronald Berger

"Richard Crowley" wrote in message
...
CU's measurement of 4 ohms sounds like the minimum impedance
at some (unspecified) frequency. This seems normal to me. Look
at any impedance curve and you can see that the variation between
minimum and maximum impedance can sometimes be 2x or even 4x.

Or 10x!.

The fact that CU is reporting the minimum impedance (without any
apparent explanation or context) is just indicative of their questionable
understanding, judgement, and reliability in technical areas.

Very true.

No offense, but the notion that "measurements are measurements
not opinions" is not a safe world-view to subscribe to.

It's quite correct. It's when you are basing an opinion on questionable
measurements that problems arise.
Only when you know exactly what is being measured, and the uncertainty of
those measurements, is it is possible to arrive at a valid conclusion.

ALWAYS
question how the measurements were made and what is the hidden
agenda of the person reporting them. In CU's case, reporting 4 ohms
for nominally-rated 8 ohm speakers makes them look like consumer
champions giving you valuable information worth paying for.

Well spotted.:-)

TonyP.