The 2 regular amps I use in my room are a Yamaha 100w A/V receiver (used for
DVD video movies) and a home brew 37W P/P Ultralinear EL34s (used for music
listening CD & vinyl).
I recently purchased on ebay, an Infinity RS IIIB pair of speakers. I don't
know the SPL, but I imagine it's not too high. My other speakers had an SPL
of 95.
Well to my surprise, the Infinity's on the Yamaha, blew away my other
speakers on the EL34s. Yes here was a transistorized A/V receiver
outperforming my tube amp.
I concluded that the Infinitys like more power. They sounded OK with the
tube amp at low volumes and provided there was no transient demands, in
which they clipped shamefully.
Almost all of my experience (& not that much. I learn most of it from
rec.audio.tubes and reading) with tube amps is low power (35-60watts).
Now I want to keep the Infinitiys, but I'll have to have more power. I can
buy a SS (gasp!) power amp and use it with a lush tube preamp that hopefully
will give me a warm tube sound or build a higher powered tube amp.
What I asking fellow Rodents is how much power do you think I'll need in a
tube amp? Are there any models that you recommend? Like I said almost all of
my experience is with low powered tube stuff. Ideas?
Cordially,
west

west wrote:

The 2 regular amps I use in my room are a Yamaha 100w A/V receiver (used for
DVD video movies) and a home brew 37W P/P Ultralinear EL34s (used for music
listening CD & vinyl).
I recently purchased on ebay, an Infinity RS IIIB pair of speakers. I don't
know the SPL, but I imagine it's not too high. My other speakers had an SPL
of 95.
Well to my surprise, the Infinity's on the Yamaha, blew away my other
speakers on the EL34s. Yes here was a transistorized A/V receiver
outperforming my tube amp.
I concluded that the Infinitys like more power. They sounded OK with the
tube amp at low volumes and provided there was no transient demands, in
which they clipped shamefully.
Almost all of my experience (& not that much. I learn most of it from
rec.audio.tubes and reading) with tube amps is low power (35-60watts).
Now I want to keep the Infinitiys, but I'll have to have more power. I can
buy a SS (gasp!) power amp and use it with a lush tube preamp that hopefully
will give me a warm tube sound or build a higher powered tube amp.
What I asking fellow Rodents is how much power do you think I'll need in a
tube amp? Are there any models that you recommend? Like I said almost all of
my experience is with low powered tube stuff. Ideas?
Cordially,
west

Measure how much power is used to make the nice SS sound with
the Infinitys.
Get a peak and hold meter, and put some busy music on and measure of a 5 minute
time
for the highest peak voltage.
You need to know the speaker impedance.

Get back to us about it.


Patrick Turner.

I have a similar problem with my electrostats (80 dB). I'm working on a PP
amp using the SV811-10 triode, hoping to get 110W from class AB2 operation.
In Your case I suppose it will take a parallel PP using KT88s or eq. in UL
mode, with a sensible amount of feedback and big output iron, bursting out
some 250W, to be sure to get the job done.
By the way, this amp is made of two mono frames in order to save my aching
spine when moving them (65 pounds each, imagine to double this!).

Ciao

Fabio


"west" ha scritto nel messaggio
.. .
The 2 regular amps I use in my room are a Yamaha 100w A/V receiver (used
for
DVD video movies) and a home brew 37W P/P Ultralinear EL34s (used for
music
listening CD & vinyl).
I recently purchased on ebay, an Infinity RS IIIB pair of speakers. I
don't
know the SPL, but I imagine it's not too high. My other speakers had an
SPL
of 95.
Well to my surprise, the Infinity's on the Yamaha, blew away my other
speakers on the EL34s. Yes here was a transistorized A/V receiver
outperforming my tube amp.
I concluded that the Infinitys like more power. They sounded OK with the
tube amp at low volumes and provided there was no transient demands, in
which they clipped shamefully.
Almost all of my experience (& not that much. I learn most of it from
rec.audio.tubes and reading) with tube amps is low power (35-60watts).
Now I want to keep the Infinitiys, but I'll have to have more power. I can
buy a SS (gasp!) power amp and use it with a lush tube preamp that
hopefully
will give me a warm tube sound or build a higher powered tube amp.
What I asking fellow Rodents is how much power do you think I'll need in a
tube amp? Are there any models that you recommend? Like I said almost all
of
my experience is with low powered tube stuff. Ideas?
Cordially,
west

Wessel Dirksen wrote:

Hi West,

The whole Infinity RS Series, particularly the RS-III's and II's were
notorius for being hard to drive. The reason for this is that the EMIT
ribbon tweeters of the time (which had to be used there because they were
Infinity's pride and joy back then) were quite capacitive as all ribbons
tend to be.

I thought ribbons were mainly resistive, and one of the most resistive
of all types of speakers, but usually they are low resistance,
so a decent step down matching tranny is needed.

This is particularly in the lower stop band where it takes, yes

give me some more, capacitance to filter the business. Not only that but the
Emit I's and II's have an absurd Rdc of 3.4 ohms, so they are also hard to
drive in the pass band. In later models they series wired EMIT tweeters but
sonically it isn't beneficial. The FR of your tube amp running the
Infinity's will probably look pretty terrible. I'm afraid it will reamin a
miserable match with your tube amp unless you mod the speakers.

Maybe a simple 8 ohm to 3 ohm tranny would suffice.



Alot can be acheived by making modifications on the filters. I have done a
few RS-II's revisions a long time ago and most of the customers choose for
an extreme makeover of the filters. If you choose for an "abstinance"
route, you can wire impedance compensation networks parallel on the inputs
without even touching the X-over. This doesn't change the transfer function
of the filter but does improve the loudspeakers performance as a load for
your tube amp which will always be more senstive to this than a SS amp. Also
back then unit ot unit variability of the FR out the box was not that great
so just individual TLC tweeking without a topology change can really shape
things up with Z compensation with only a slight reduction of Zmin.

One really has to know what one is doing to achieve the wanted outcome.
Some decent measuring method would be nice.

If speakers are hard to drive due to low impedance,
change the amp outlet to the 4 ohms.
If the sensitivity of the speakers is to low, then no amount of tweaking
will allow a low power amp to be used with power hungry speakers.

Patrick Turner.



Hope this helps, By the way, which series from which year?

Wessel

Fabio Berutti wrote:

I have a similar problem with my electrostats (80 dB). I'm working on a PP
amp using the SV811-10 triode, hoping to get 110W from class AB2 operation.
In Your case I suppose it will take a parallel PP using KT88s or eq. in UL
mode, with a sensible amount of feedback and big output iron, bursting out
some 250W, to be sure to get the job done.
By the way, this amp is made of two mono frames in order to save my aching
spine when moving them (65 pounds each, imagine to double this!).

for speakers with 96 dB/W/M, a pair of EL84 in UL or a 16 watt
Williamson triode is OK, as 108 dB can be achieved with 16 watts.
But 8 watts is plenty.

But for 90dB speakers, you need about 32 watts,

And for 80 dB speakers, you need 128 watts.

This assumes the load is resistive.

But for ESL, the load is somewhat capacitive,
so you need the current abity for the HF, and the voltage ability
for the LF, which may well exceed the voltage into say 8 ohms at 1 kHz,
and so maybe 80 dB ESL need a 250 watt able to power any load between
3 and 16 ohms and give a voltage max of about 44 vrms.
44v into 3 ohms is 645 watts, and 44v into 16 ohms is 121 watts.

If you want a reliable 250 watt capability, try using a dozen 6550/KT88,
and then you get an effortless 100 watts of class A into 8 ohms
with the rest as class AB.
ESL are "funny" loads though, but maybe you have to consider
current and voltage needs carefully.

I can never find an impedance curve for the largest model of Martin Logan.
It maybe is horrible, but whatever the horrinility factor,
a tube amp will cut the mustard if you have a decent OPT
with good load matching, and enough tubes to do the business.

I had a customer with 80 dB ATC floor standers, and he liked the
dozen 6550.

A dozen 6L6 will also make about 300 watts,
but you just won't get as much class A because there isn't
as much idle power dissipation.

Patrick Turner.







Ciao

Fabio

"west" ha scritto nel messaggio
.. .
The 2 regular amps I use in my room are a Yamaha 100w A/V receiver (used
for
DVD video movies) and a home brew 37W P/P Ultralinear EL34s (used for
music
listening CD & vinyl).
I recently purchased on ebay, an Infinity RS IIIB pair of speakers. I
don't
know the SPL, but I imagine it's not too high. My other speakers had an
SPL
of 95.
Well to my surprise, the Infinity's on the Yamaha, blew away my other
speakers on the EL34s. Yes here was a transistorized A/V receiver
outperforming my tube amp.
I concluded that the Infinitys like more power. They sounded OK with the
tube amp at low volumes and provided there was no transient demands, in
which they clipped shamefully.
Almost all of my experience (& not that much. I learn most of it from
rec.audio.tubes and reading) with tube amps is low power (35-60watts).
Now I want to keep the Infinitiys, but I'll have to have more power. I can
buy a SS (gasp!) power amp and use it with a lush tube preamp that
hopefully
will give me a warm tube sound or build a higher powered tube amp.
What I asking fellow Rodents is how much power do you think I'll need in a
tube amp? Are there any models that you recommend? Like I said almost all
of
my experience is with low powered tube stuff. Ideas?
Cordially,
west

Wessel Dirksen wrote:

"Patrick Turner" wrote in message
...


Wessel Dirksen wrote:

Hi West,

The whole Infinity RS Series, particularly the RS-III's and II's were
notorius for being hard to drive. The reason for this is that the EMIT
ribbon tweeters of the time (which had to be used there because they were
Infinity's pride and joy back then) were quite capacitive as all ribbons
tend to be.

. . . down low.

Well why?



I thought ribbons were mainly resistive, and one of the most resistive
of all types of speakers, but usually they are low resistance,
so a decent step down matching tranny is needed.

This is particularly in the lower stop band where it takes, yes

right


give me some more, capacitance to filter the business. Not only that but
the
Emit I's and II's have an absurd Rdc of 3.4 ohms, so they are also hard
to
drive in the pass band. In later models they series wired EMIT tweeters
but
sonically it isn't beneficial. The FR of your tube amp running the
Infinity's will probably look pretty terrible. I'm afraid it will reamin
a
miserable match with your tube amp unless you mod the speakers.

Maybe a simple 8 ohm to 3 ohm tranny would suffice.

You mean the OPT in the amp, right?

Not necessarily.
If you have only an 8 ohm outlet, and the speakers dip to
2.5 ohms or some low Z, then a separate 8 ohm to 3 ohm
tranny will change the Z that the amp sees.

The tranny can be used just for the midrange/tweeters if that is the low Z.
Depends on exactly what impedance you have to drive.
But low Z trannies can be wound to overcome the mismatch if there is one.
Such trannies are not available off the shelf; its a special item,
but its all thick wire, and easy to wind.



Alot can be acheived by making modifications on the filters. I have done
a
few RS-II's revisions a long time ago and most of the customers choose
for
an extreme makeover of the filters. If you choose for an "abstinance"
route, you can wire impedance compensation networks parallel on the
inputs
without even touching the X-over. This doesn't change the transfer
function
of the filter but does improve the loudspeakers performance as a load for
your tube amp which will always be more senstive to this than a SS amp.
Also
back then unit ot unit variability of the FR out the box was not that
great
so just individual TLC tweeking without a topology change can really
shape
things up with Z compensation with only a slight reduction of Zmin.

One really has to know what one is doing to achieve the wanted outcome.
Some decent measuring method would be nice.

True. this sort of assumes you can find a tweeker in the area.


If speakers are hard to drive due to low impedance,
change the amp outlet to the 4 ohms.
If the sensitivity of the speakers is to low, then no amount of tweaking
will allow a low power amp to be used with power hungry speakers.

I forgot to mention the sensitivity issue. I have not worked on or measured
any RS-III's but I have seen measured factory data from all of them (a long
time ago) and have had a few EMIT's in my hands through the years. Overall
sensitivity is low because the EMIT I's are somewhere in the mid to low 80's
dB/W/m, and the rest of the system is attenuated (sometimes castrated) to
suit. As I recall the 3's and the 4's have similar basic driver arrangements
with the 4's having 2x 6.5 PP woofers and the III's 2x 8's (or 10's?), both
wired in parallel. Both use a PP 50mm dome midrange which was a very cool
Infinity driver of the day. On both there was a Zmin well into the mid 3 ohm
range in the low hundreds of hertz with a rather large bandwidth under 4
ohms, close to an octave as I recall. On both they do not compensate Z in
the X-over regions with a huge impedance swing up to 30 to 40 or so ohms I
think; so concurrently negative Z phase angles abound there.

Not much fun for amps. These speakers were designed for moderately priced SS
muscle amps of the day (Hafler, Adcom). RS-II's in original spec sounded
quite good on Aragon or Krell. They flatout sucked on Carver amp's.

They seem to have a substantial amount of Z below 4 ohms.

But if you have decent impedance matching, a tube amp will cope.
It just needs to have lots of tubes to get the power if the sensitivity low 80s,

if one likes loud levels.
I also like to impedance equalise all speakers.
The high impedance peaks of the woofers isn't a problem though.

Patrick Turner.






Patrick Turner.



Hope this helps, By the way, which series from which year?

Wessel

Hi Patrick,
What do you mean... "I like to equalize each speaker." How do you do that?
Also where can I get a hold of a Peak & Hold meter? Thanks.
west

"Patrick Turner" wrote in message
...


west wrote:

The 2 regular amps I use in my room are a Yamaha 100w A/V receiver (used
for
DVD video movies) and a home brew 37W P/P Ultralinear EL34s (used for
music
listening CD & vinyl).
I recently purchased on ebay, an Infinity RS IIIB pair of speakers. I
don't
know the SPL, but I imagine it's not too high. My other speakers had an
SPL
of 95.
Well to my surprise, the Infinity's on the Yamaha, blew away my other
speakers on the EL34s. Yes here was a transistorized A/V receiver
outperforming my tube amp.
I concluded that the Infinitys like more power. They sounded OK with the
tube amp at low volumes and provided there was no transient demands, in
which they clipped shamefully.
Almost all of my experience (& not that much. I learn most of it from
rec.audio.tubes and reading) with tube amps is low power (35-60watts).
Now I want to keep the Infinitiys, but I'll have to have more power. I
can
buy a SS (gasp!) power amp and use it with a lush tube preamp that
hopefully
will give me a warm tube sound or build a higher powered tube amp.
What I asking fellow Rodents is how much power do you think I'll need in
a
tube amp? Are there any models that you recommend? Like I said almost
all of
my experience is with low powered tube stuff. Ideas?
Cordially,
west

Measure how much power is used to make the nice SS sound with
the Infinitys.
Get a peak and hold meter, and put some busy music on and measure of a 5
minute
time
for the highest peak voltage.
You need to know the speaker impedance.

Get back to us about it.


Patrick Turner.

Patrick Turner wrote:
Wessel Dirksen wrote:

"Patrick Turner" wrote in message
...


Wessel Dirksen wrote:

Hi West,

The whole Infinity RS Series, particularly the RS-III's and II's
were
notorius for being hard to drive. The reason for this is that
the EMIT
ribbon tweeters of the time (which had to be used there because
they were
Infinity's pride and joy back then) were quite capacitive as all
ribbons
tend to be.

. . . down low.

Well why?

I have no idea why actually. Older ribbons and also to an extent
electrostatics tend to have this characteristic below the pass band. It
certainly makes sense from an inheirant 1st order HP filter standpoint,
but I just see it. I prefer good old electromagnetic drivers myself.



I thought ribbons were mainly resistive, and one of the most
resistive
of all types of speakers, but usually they are low resistance,
so a decent step down matching tranny is needed.

This is particularly in the lower stop band where it takes, yes

right


give me some more, capacitance to filter the business. Not only
that but
the
Emit I's and II's have an absurd Rdc of 3.4 ohms, so they are
also hard
to
drive in the pass band. In later models they series wired EMIT
tweeters
but
sonically it isn't beneficial. The FR of your tube amp running
the
Infinity's will probably look pretty terrible. I'm afraid it
will reamin
a
miserable match with your tube amp unless you mod the speakers.

Maybe a simple 8 ohm to 3 ohm tranny would suffice.

You mean the OPT in the amp, right?

Not necessarily.
If you have only an 8 ohm outlet, and the speakers dip to
2.5 ohms or some low Z, then a separate 8 ohm to 3 ohm
tranny will change the Z that the amp sees.

The tranny can be used just for the midrange/tweeters if that is the
low Z.
Depends on exactly what impedance you have to drive.
But low Z trannies can be wound to overcome the mismatch if there is
one.
Such trannies are not available off the shelf; its a special item,
but its all thick wire, and easy to wind.

Well I was reluctantly thinking you meant this Patrick. I can't comment
from experience but a tranny in the loudspeaker after amplification
just feels bad to me but that could be superstition on my part. Now
that I am just beginning to understand tube amplification I can
understand why you mentioned this as an option. You may be right, but
it just seems weird to me. 100V tranny systems never sound good but of
course aren't meant to sound good.


Alot can be acheived by making modifications on the filters. I
have done
a
few RS-II's revisions a long time ago and most of the customers
choose
for
an extreme makeover of the filters. If you choose for an
"abstinance"
route, you can wire impedance compensation networks parallel on
the
inputs
without even touching the X-over. This doesn't change the
transfer
function
of the filter but does improve the loudspeakers performance as a
load for
your tube amp which will always be more senstive to this than a
SS amp.
Also
back then unit ot unit variability of the FR out the box was not
that
great
so just individual TLC tweeking without a topology change can
really
shape
things up with Z compensation with only a slight reduction of
Zmin.

One really has to know what one is doing to achieve the wanted
outcome.
Some decent measuring method would be nice.

True. this sort of assumes you can find a tweeker in the area.


If speakers are hard to drive due to low impedance,
change the amp outlet to the 4 ohms.
If the sensitivity of the speakers is to low, then no amount of
tweaking
will allow a low power amp to be used with power hungry speakers.

I forgot to mention the sensitivity issue. I have not worked on or
measured
any RS-III's but I have seen measured factory data from all of them
(a long
time ago) and have had a few EMIT's in my hands through the years.
Overall
sensitivity is low because the EMIT I's are somewhere in the mid to
low 80's
dB/W/m, and the rest of the system is attenuated (sometimes
castrated) to
suit. As I recall the 3's and the 4's have similar basic driver
arrangements
with the 4's having 2x 6.5 PP woofers and the III's 2x 8's (or
10's?), both
wired in parallel. Both use a PP 50mm dome midrange which was a
very cool
Infinity driver of the day. On both there was a Zmin well into the
mid 3 ohm
range in the low hundreds of hertz with a rather large bandwidth
under 4
ohms, close to an octave as I recall. On both they do not
compensate Z in
the X-over regions with a huge impedance swing up to 30 to 40 or so
ohms I
think; so concurrently negative Z phase angles abound there.

Not much fun for amps. These speakers were designed for moderately
priced SS
muscle amps of the day (Hafler, Adcom). RS-II's in original spec
sounded
quite good on Aragon or Krell. They flatout sucked on Carver amp's.

They seem to have a substantial amount of Z below 4 ohms.

Measured data rarely went higher than 20 kHz in the day, but the
overall Z stays low above 10Khz (little inductance) and yo can bet that
the EMIT's stay at a low impedance even higher.


But if you have decent impedance matching, a tube amp will cope.
It just needs to have lots of tubes to get the power if the
sensitivity low 80s,

if one likes loud levels.
I also like to impedance equalise all speakers.
The high impedance peaks of the woofers isn't a problem though.

This is a good point. Just a matter of curiosity. This happens more
often that non-compensated capacitive loads occur in the x-over region
of production loudspeakers. It seems that "good" amps tend to sound
better with these types of loads. So how much is a negative phase
impedance load less of a crucial factor when the Z magnitude is higher?
(as it often is)

Wessel


Patrick Turner.






Patrick Turner.



Hope this helps, By the way, which series from which year?

Wessel

Patrick Turner wrote:
Wessel Dirksen wrote:

"Patrick Turner" wrote in message
...


Wessel Dirksen wrote:

Hi West,

The whole Infinity RS Series, particularly the RS-III's and II's
were
notorius for being hard to drive. The reason for this is that
the EMIT
ribbon tweeters of the time (which had to be used there because
they were
Infinity's pride and joy back then) were quite capacitive as all
ribbons
tend to be.

. . . down low.

Well why?

I have no idea why actually. Older ribbons and also to an extent
electrostatics tend to have this characteristic below the pass band. It
certainly makes sense from an inheirant 1st order HP filter standpoint,
but I just see it. I prefer good old electromagnetic drivers myself.



I thought ribbons were mainly resistive, and one of the most
resistive
of all types of speakers, but usually they are low resistance,
so a decent step down matching tranny is needed.

This is particularly in the lower stop band where it takes, yes

right


give me some more, capacitance to filter the business. Not only
that but
the
Emit I's and II's have an absurd Rdc of 3.4 ohms, so they are
also hard
to
drive in the pass band. In later models they series wired EMIT
tweeters
but
sonically it isn't beneficial. The FR of your tube amp running
the
Infinity's will probably look pretty terrible. I'm afraid it
will reamin
a
miserable match with your tube amp unless you mod the speakers.

Maybe a simple 8 ohm to 3 ohm tranny would suffice.

You mean the OPT in the amp, right?

Not necessarily.
If you have only an 8 ohm outlet, and the speakers dip to
2.5 ohms or some low Z, then a separate 8 ohm to 3 ohm
tranny will change the Z that the amp sees.

The tranny can be used just for the midrange/tweeters if that is the
low Z.
Depends on exactly what impedance you have to drive.
But low Z trannies can be wound to overcome the mismatch if there is
one.
Such trannies are not available off the shelf; its a special item,
but its all thick wire, and easy to wind.

Well I was reluctantly thinking you meant this Patrick. I can't comment
from experience but a tranny in the loudspeaker after amplification
just feels bad to me but that could be superstition on my part. Now
that I am just beginning to understand tube amplification I can
understand why you mentioned this as an option. You may be right, but
it just seems weird to me. 100V tranny systems never sound good but of
course aren't meant to sound good.


Alot can be acheived by making modifications on the filters. I
have done
a
few RS-II's revisions a long time ago and most of the customers
choose
for
an extreme makeover of the filters. If you choose for an
"abstinance"
route, you can wire impedance compensation networks parallel on
the
inputs
without even touching the X-over. This doesn't change the
transfer
function
of the filter but does improve the loudspeakers performance as a
load for
your tube amp which will always be more senstive to this than a
SS amp.
Also
back then unit ot unit variability of the FR out the box was not
that
great
so just individual TLC tweeking without a topology change can
really
shape
things up with Z compensation with only a slight reduction of
Zmin.

One really has to know what one is doing to achieve the wanted
outcome.
Some decent measuring method would be nice.

True. this sort of assumes you can find a tweeker in the area.


If speakers are hard to drive due to low impedance,
change the amp outlet to the 4 ohms.
If the sensitivity of the speakers is to low, then no amount of
tweaking
will allow a low power amp to be used with power hungry speakers.

I forgot to mention the sensitivity issue. I have not worked on or
measured
any RS-III's but I have seen measured factory data from all of them
(a long
time ago) and have had a few EMIT's in my hands through the years.
Overall
sensitivity is low because the EMIT I's are somewhere in the mid to
low 80's
dB/W/m, and the rest of the system is attenuated (sometimes
castrated) to
suit. As I recall the 3's and the 4's have similar basic driver
arrangements
with the 4's having 2x 6.5 PP woofers and the III's 2x 8's (or
10's?), both
wired in parallel. Both use a PP 50mm dome midrange which was a
very cool
Infinity driver of the day. On both there was a Zmin well into the
mid 3 ohm
range in the low hundreds of hertz with a rather large bandwidth
under 4
ohms, close to an octave as I recall. On both they do not
compensate Z in
the X-over regions with a huge impedance swing up to 30 to 40 or so
ohms I
think; so concurrently negative Z phase angles abound there.

Not much fun for amps. These speakers were designed for moderately
priced SS
muscle amps of the day (Hafler, Adcom). RS-II's in original spec
sounded
quite good on Aragon or Krell. They flatout sucked on Carver amp's.

They seem to have a substantial amount of Z below 4 ohms.

Measured data rarely went higher than 20 kHz in the day, but the
overall Z stays low above 10Khz (little inductance) and yo can bet that
the EMIT's stay at a low impedance even higher.


But if you have decent impedance matching, a tube amp will cope.
It just needs to have lots of tubes to get the power if the
sensitivity low 80s,

if one likes loud levels.
I also like to impedance equalise all speakers.
The high impedance peaks of the woofers isn't a problem though.

This is a good point. Just a matter of curiosity. This happens more
often that non-compensated capacitive loads occur in the x-over region
of production loudspeakers. It seems that "good" amps tend to sound
better with these types of loads. So how much is a negative phase
impedance load less of a crucial factor when the Z magnitude is higher?
(as it often is)

Wessel


Patrick Turner.






Patrick Turner.



Hope this helps, By the way, which series from which year?

Wessel

Wessel Dirksen wrote:

Patrick Turner wrote:
Wessel Dirksen wrote:

"Patrick Turner" wrote in message
...


Wessel Dirksen wrote:

Hi West,

The whole Infinity RS Series, particularly the RS-III's and II's
were
notorius for being hard to drive. The reason for this is that
the EMIT
ribbon tweeters of the time (which had to be used there because
they were
Infinity's pride and joy back then) were quite capacitive as all
ribbons
tend to be.

. . . down low.

Well why?

I have no idea why actually. Older ribbons and also to an extent
electrostatics tend to have this characteristic below the pass band. It
certainly makes sense from an inheirant 1st order HP filter standpoint,
but I just see it. I prefer good old electromagnetic drivers myself.

See the ribbon speakers made in Oz at

http://www.ambiencespeakers.com.au/

These all have bass speakers attached, hence
their Z character becomes like a capacitor at some low F
The interaction of speaker to the box causes the Z to change
to largle reactive.
If a speaker Z rises and is reactive it does not matter if the sensitivity
is maintained,
since the amp will always cope.
But where a speaker's reactance, L or C reduces the Z to a low value,
then the amp may have trouble maintaining the output voltage.

Electrostats are large capacitors, but with some series R and
parallel R across them.




If you have only an 8 ohm outlet, and the speakers dip to
2.5 ohms or some low Z, then a separate 8 ohm to 3 ohm
tranny will change the Z that the amp sees.

The tranny can be used just for the midrange/tweeters if that is the
low Z.
Depends on exactly what impedance you have to drive.
But low Z trannies can be wound to overcome the mismatch if there is
one.
Such trannies are not available off the shelf; its a special item,
but its all thick wire, and easy to wind.

Well I was reluctantly thinking you meant this Patrick. I can't comment
from experience but a tranny in the loudspeaker after amplification
just feels bad to me but that could be superstition on my part.

All ESL have step up transformers, Martin Logan, Quad, etc.
These are regarded by many as extremely good speakers.
The extra distortions added by the transformers don't seem to wreck the
music.

Now
that I am just beginning to understand tube amplification I can
understand why you mentioned this as an option. You may be right, but
it just seems weird to me. 100V tranny systems never sound good but of
course aren't meant to sound good.

Most 100v systems are used in PA work.

A purpose wound 8 ohm to 4 ohm tranny will have a
turn ratio of 1.41 : 1.0, and if wound to
to saturate at full powwer at less than 14 Hz and wound with
a many interleavings, the bw can be 400 kHz.
if the core is GOSS, the thd will be quite negligible.



But if you have decent impedance matching, a tube amp will cope.
It just needs to have lots of tubes to get the power if the
sensitivity low 80s,

if one likes loud levels.
I also like to impedance equalise all speakers.
The high impedance peaks of the woofers isn't a problem though.

This is a good point. Just a matter of curiosity. This happens more
often that non-compensated capacitive loads occur in the x-over region
of production loudspeakers.

Midranges appear as a capacitor load at LF.
Its not a worry.

ESL are mainly capacitive for their whole range.


It seems that "good" amps tend to sound
better with these types of loads.

A well made amp isn't upset by capacitor loads.

So how much is a negative phase
impedance load less of a crucial factor when the Z magnitude is higher?
(as it often is)

If Z goes high, the current is low, and the amp copes fine.
A 10 uF cap at 100 Hz is a 159 ohm reactive load.
Conecting it across the output terminals with a 100 Hz signal
cannot do any damage, and a low current flows
even at clipping.
But at 10 kHz, the same 10 uF becomes 1.59 ohms, and
most amps will poop themselves if asked to
maintain the mid band power levels.
50 watts into 8 ohms is 20 vrms, and I = 2.5 amps rms.
4 vrms vrms into 1.59 ohms = 2.5 amps rms.
20 vrms would mean I = 12.5 amps, and
this current flows in the output devices will cause gross
overheating if maintained for some time.

But levels of HF in music decline rapidly above 5 kHz, so
strapping a 10 uF across the output of a 50 watt
amp playing music at an average 1 watt level
won't usually have much effect on the sound if the amp has
a low Rout.
If you don't think so, try it with an old amp.
Just don't do it for longer than 10 seconds to see that not much happens.

Patrick Turner.