[[email protected]]

Serge Auckland wrote:

It's not so much that the old amplifier is incompatible; it is, of
course, by today's standards, but perhaps not at the time.

The AR3As have an impedance that drops below 3 ohms, and few 8 ohm rated
solid-state power amps of the period were happy into 3 ohms, let alone
less.

Actually, something on the order of 1.8 ohms at certain frequencies.
And, you are correct that few SS amps of the time could do this at
length without blowing a gasket (output transistor) or two. And why I
picked (and pick) my equipment with some care as I keep several pairs
of 3as and have for years.

Now, as to tube equipment, I have typically used the nominally higher
taps, e.g. the 8-ohm taps for the 3as from my ST-70 and LK-150. This
gives less power, but also less distortion and more stability, as well
as a slightly higher damping factor, all good things.

But the Citation 16 and the ST-416 (both 'happy' down to 1 ohm dynamic
load) do best on these beasts. Lots-O-Headroom.

Now as a completely random historical aside, the Dynaco ST-120 was
purportedly developed directly for the 3a, or so local legend has it.
It very nearly mimicked the AR Integrated Amp circuit design excepting
the interstage transformers and choice of driver transistors. But,
apart from sounding like glass in a blender, it blew up regularly,
sometimes spectacularly. After several years worth of changes and
modifications, it ultimately became relatively stable - except for the
fact that by then the 3a was no longer the _only_ top-end speaker _AND_
most such were a nominal 8 ohms. I no longer keep a 120, I guess I
would not turn one down if it were left on my porch, but I would not
seek one out. I have done the mods on a few which are still playing
after some years... but not into AR speakers and not in my house.

The AR amp did have bias stability problems, but once those were solved
it was and remains a fine integrated amp well matched to the 3as. I
keep two that have all the factory-designed mods (both did not and were
not working when I got them) as well as a few tweaks of my own. They
have taken all sorts of use and abuse without a single quiver. Go
figure.

Peter Wieck
Wyncote, PA

[[email protected]]

wrote:
Serge Auckland wrote:

It's not so much that the old amplifier is incompatible; it is, of
course, by today's standards, but perhaps not at the time.

The AR3As have an impedance that drops below 3 ohms, and few 8 ohm rated
solid-state power amps of the period were happy into 3 ohms, let alone
less.

Actually, something on the order of 1.8 ohms at certain frequencies.

No. I have now been able to obtain, from a number of
sources, detailed impedance data on the AR3a to
complement the measurement data I made some years
ago. Across all this data, the lowest impedance over the
range 10 to about 40 kHz occurs around 780 Hz
and of all the sample, the lowest is 2.8 ohms, and this
is only with the level control set to one extreme. The only
other place it exhibits anything that low is around 110
Hz, where it's about 2.83 ohms. It remains above 3 ohms
from 10 Hz to about 85 Hz, from 145 Hz to abou 670 Hz,
and from 940 Hz on up.

The region which was MOST difficult for most solid state
amplifier in terms of driving low impedances was at the
higher frequencies, because of their severely limited
open-loop bandwidth (often less than 1 Hz) that lead
to both increased output impedance and reduced stability
margins at higher frequencies. In that case, the AR3a
presented a completely benign load, having no severe
dips in impedance and presented a very modest
impedance phase above 1 kHz. Above about 1300 Hz,
the AR3a essentially never goes below 4 ohms.

Now, the whole issue of the low impedance and
contemporary solid state amplifiers was really only
a factor when one tried to drive the amps to their
extremes. If our friend's claim is correct that he does
most of his listening at or near 1 watt, which is perfectly
believable, then the whole issue of power supply rail
voltage and current capability is simply irrelevant.

What is interesting is that if you do a wee bit of
digging on the performance of the AR-1500, you
start to find a LOT people bitching about how truly
awful it is: how unstable, how unreliable, basically
how wretched a unit it is. Come on, folks, IT WAS A
FREAKIN' KIT!

Our friend seems to have no interest in pursuing all
the possible explanations of why he ended up with
what he did. There is no attempt at all to in any way
independently and objectively verify or refute his
chosen theory. I have seen no small number of
people do pretty much what he describes and end
up with results that end up, no doubt, sounding
"stunningly" different (that is, "different"). When
explored in more detail, we find a much simpler
explanation is to be obtined, such as the two
amplfier chosen had 4-5 dB different gain, resulting
in a frequency response that's radically different, or
on amplifier was inverting, tho other non-inverting,
and half-octave wide, 20 dB deep hole ended up
in the response, or the tone control "crossover"
ended up affecting amuch wider band than
assumed; or one amp that was essentially unstable
was now a little happier, and so on.

[[email protected]]

wrote:
wrote:
Serge Auckland wrote:

It's not so much that the old amplifier is incompatible; it is, of
course, by today's standards, but perhaps not at the time.

The AR3As have an impedance that drops below 3 ohms, and few 8 ohm rated
solid-state power amps of the period were happy into 3 ohms, let alone
less.

Actually, something on the order of 1.8 ohms at certain frequencies.

No. I have now been able to obtain, from a number of
sources, detailed impedance data on the AR3a to
complement the measurement data I made some years
ago. Across all this data, the lowest impedance over the
range 10 to about 40 kHz occurs around 780 Hz
and of all the sample, the lowest is 2.8 ohms, and this
is only with the level control set to one extreme. The only
other place it exhibits anything that low is around 110
Hz, where it's about 2.83 ohms. It remains above 3 ohms
from 10 Hz to about 85 Hz, from 145 Hz to abou 670 Hz,
and from 940 Hz on up.

If you say so. But as you are taking your data off a sheet vs. in the
field, permit me to merely suggest differently based on field
experience.

IT WAS A
FREAKIN' KIT!

Lemme see... so was the Dynaco ST-70, Scott LK 150, Dynaco ST416,
Hafler DH200,500 and so forth. Nothing wrong with a well-built,
well-designed kit. Nothing at all. I know nothing about Heath products
other than their (pretty good) mid-grade test instruments. But that it
was a kit is meaningless.

And so it goes.

Peter Wieck
Wyncote, PA

[[email protected]]

wrote:
wrote:
wrote:

Actually, something on the order of 1.8 ohms at certain frequencies.

No. I have now been able to obtain, from a number of
sources, detailed impedance data on the AR3a to
complement the measurement data I made some years
ago.

If you say so. But as you are taking your data off a sheet vs. in the
field, permit me to merely suggest differently based on field
experience.

Let's try this onmce again. I said:

"No. I have now been able to obtain, from a number of
sources, detailed impedance data on the AR3a to
complement the measurement data I made some years
ago."

I HAVE measured the AR3a, in addition to a number of
people who have also measured them. Not a single one
shows the data you're suggesting.

[Jerry]

Peter wrote on 8/23/2006:

Actually, something on the order of 1.8 ohms at certain frequencies.
And, you are correct that few SS amps of the time could do this at
length without blowing a gasket (output transistor) or two. And why I
picked (and pick) my equipment with some care as I keep several pairs
of 3as and have for years.

Now, as to tube equipment, I have typically used the nominally higher
taps, e.g. the 8-ohm taps for the 3as from my ST-70 and LK-150. This
gives less power, but also less distortion and more stability, as well
as a slightly higher damping factor, all good things.

Peter, why you NOT choose the taps that are closest to the actual impedance?
When the impedance matches don't we get better power transmission and less
power dissipation in our amp?

Your ST-70??? Was this a Dynaco or and Eico? Reason I ask is that I built
an Eico ST-70 and I read somewhere (actually I think it was in this group)
that the Eico unit is a copy/clone of the Dynaco.

I only keep it a year or two and traded up to an Eico solid state receiver.
Now, this ss unit was similar in design to the AR amp. It had an
inter-stage transformer, but direct output to the speakers.

As I recall the Dynaco ST-120 was capacitively coupled to the speakers. Is
this correct, Peter?

Regards,
Jerry

[Jerry]

Dick wrote on 8/23/2006

No. I have now been able to obtain, from a number of
sources, detailed impedance data on the AR3a to
complement the measurement data I made some years
ago. Across all this data, the lowest impedance over the
range 10 to about 40 kHz occurs around 780 Hz
and of all the sample, the lowest is 2.8 ohms, and this
is only with the level control set to one extreme. The only
other place it exhibits anything that low is around 110
Hz, where it's about 2.83 ohms. It remains above 3 ohms
from 10 Hz to about 85 Hz, from 145 Hz to abou 670 Hz,
and from 940 Hz on up.

Wow!! Dick, this is the first confirmation that my measurements are in the
right ballpark. Now, we are NOT in total sync on the frequencies, but
remember those blasted pots (there are two of them) will cause minor shifts
in the xover frequencies. I'd say we are pretty close!

The region which was MOST difficult for most solid state
amplifier in terms of driving low impedances was at the
higher frequencies, because of their severely limited
open-loop bandwidth (often less than 1 Hz) that lead
to both increased output impedance and reduced stability
margins at higher frequencies. In that case, the AR3a
presented a completely benign load, having no severe
dips in impedance and presented a very modest
impedance phase above 1 kHz. Above about 1300 Hz,
the AR3a essentially never goes below 4 ohms.

Now, the whole issue of the low impedance and
contemporary solid state amplifiers was really only
a factor when one tried to drive the amps to their
extremes. If our friend's claim is correct that he does
most of his listening at or near 1 watt, which is perfectly
believable, then the whole issue of power supply rail
voltage and current capability is simply irrelevant.

What is interesting is that if you do a wee bit of
digging on the performance of the AR-1500, you
start to find a LOT people bitching about how truly
awful it is: how unstable, how unreliable, basically
how wretched a unit it is. Come on, folks, IT WAS A
FREAKIN' KIT!

And what's wrong with a kit??? If the kit is designed conservatively,
assembled properly and all final adjustments made, there is no reason the
kit shouldn't perform as well as an assembled product. Now, I realize
there are a few "if's" there.

I did NOT assemble my AR1500, I bought it cheap from a hacker who really
messed it up . but good! Just about every board had some problems, but they
were all fixed and when I made the final adjustments, everything fell right
within the design range.

The last maintenance I performed on it was over 30 years ago, and I use it
daily, so .. I have NO complaints.

Here is a review:

http://www.ckopfell.com/HeathkitAR1500.htm

Our friend seems to have no interest in pursuing all
the possible explanations of why he ended up with
what he did. There is no attempt at all to in any way
independently and objectively verify or refute his
chosen theory. I have seen no small number of
people do pretty much what he describes and end
up with results that end up, no doubt, sounding
"stunningly" different (that is, "different"). When
explored in more detail, we find a much simpler
explanation is to be obtined, such as the two
amplfier chosen had 4-5 dB different gain, resulting
in a frequency response that's radically different, or
on amplifier was inverting, tho other non-inverting,
and half-octave wide, 20 dB deep hole ended up
in the response, or the tone control "crossover"
ended up affecting amuch wider band than
assumed; or one amp that was essentially unstable
was now a little happier, and so on.

Dick, see my new post on impedance to see how radically different the
impedance seen by the two amps differs from than seen by a single amp.

Regards,

Jerry

[Jerry]

Peter wrote on 8/24/2006:

No. I have now been able to obtain, from a number of
sources, detailed impedance data on the AR3a to
complement the measurement data I made some years
ago. Across all this data, the lowest impedance over the
range 10 to about 40 kHz occurs around 780 Hz
and of all the sample, the lowest is 2.8 ohms, and this
is only with the level control set to one extreme. The only
other place it exhibits anything that low is around 110
Hz, where it's about 2.83 ohms. It remains above 3 ohms
from 10 Hz to about 85 Hz, from 145 Hz to abou 670 Hz,
and from 940 Hz on up.

If you say so. But as you are taking your data off a sheet vs. in the
field, permit me to merely suggest differently based on field
experience.

Actually, Peter, except for some fairly minor shifts in frequency, my
measurements and Dick's are pretty darn close. (See new post titled
"Impedance maps")

Now what can really screw things up are those blasted pots. Peter, please
don't misunderstand. I am NOT saying you are wrong, because depending upon
the position of the pots, you might get a different answer.

I want to be totally honest here and admit that I have a problem with the
mid-range pot on my left speaker. About once a month I totally lose ALL
mid-range. So, what I do is move the pot back and forth a few times and the
mid-range starts working again.

As an aside, I've been reading about the various options to clean, repair or
replace those blasted pots. Nothing sounds like a great solution (with the
possible exception of JoeB's). Even JoeB's idea of the multi-position
switch can give problems at some time in the future . well maybe a very
distant future.

Anyhow, for me the ideal solution (and my next project) is to REMOVE the
pots!!! Not replace .. REMOVE!!

For me, the pot on the mid-range has already been replaced by the volume
control on the amp driving the mid-range/tweeter. I mean, I HAVE to decide
how much high frequency content I want ALL of the time.

Next, the pots on the tweeters are already at or near max.

So for me in my bi-amp configuration, the speaker pots are really redundant.
Shortly, they'll be history and . no more problems with lost mid-range!!

IT WAS A
FREAKIN' KIT!

Lemme see... so was the Dynaco ST-70, Scott LK 150, Dynaco ST416,
Hafler DH200,500 and so forth. Nothing wrong with a well-built,
well-designed kit. Nothing at all. I know nothing about Heath products
other than their (pretty good) mid-grade test instruments. But that it
was a kit is meaningless.

Peter, well said!!!

Don't forget the 1000's upon 1000's of armature radio folks who built and
still use today ... Heath's amateur gear. Heath knew how to design
product, to package in a kit with a clear instruction manual, and to develop
good final adjustment scripts. It's kind of interesting how the armature
radio guy's wouldn't even think of using their gear WITHOUT performing ALL
of those final adjustments.

Unfortunately, we don't see that same "zeal" in the audio kit builders.
It's my guess this is part of the reason audio kits get a "bad rap".

Peter, I'm sure you did all those final tests and adjustments and so did I,
but I know many who skipped those "tedious" steps.

Regards,
Jerry

[[email protected]]

Jerry wrote:

Peter, why you NOT choose the taps that are closest to the actual impedance?
When the impedance matches don't we get better power transmission and less
power dissipation in our amp?

Yes but... I seldom demand the full output of the amp, so being able to
enjoy lower distortion and a higher damping factor into the 3as is a
good thing, as I noted before.

Your ST-70??? Was this a Dynaco or and Eico? Reason I ask is that I built
an Eico ST-70 and I read somewhere (actually I think it was in this group)
that the Eico unit is a copy/clone of the Dynaco.

Dynaco, with good Mullard 6CA7s matched on my Hickok 539B. Note that
the "matching" lasted about 30 hours and then drifted into "close
enough", something that is far more typical than not. As long as the
bias remains rock-steady, things usually are fine.

I only keep it a year or two and traded up to an Eico solid state receiver.
Now, this ss unit was similar in design to the AR amp. It had an
inter-stage transformer, but direct output to the speakers.

As I recall the Dynaco ST-120 was capacitively coupled to the speakers. Is
this correct, Peter?

Yes, the same as the ST-80, but with the regulated power-supply.

Now, it is my personal belief that kit-building gives one confidence to
learn about the actual workings of these things, and to try a few
experiments. Furthermore, seeing makers re-design their products based
on real-world results can be fascinating, especially looking at those
companies that both had some longevity and also kept products in the
line for many years. The original AR line of products (tuner,
integrated amp, receiver) lasted about six years in production (?? Any
confirmation?) and they continued to support the product until their
ultimate demise. I have the latest version of their factory service
manual, printed in 1982, with multiple modifications to each piece.
Dynaco modified their ST-120, ultimately devolving to the ST-80, no
less than 11 times that I can count.. OK, perhaps fewer, but there are
11 obvious changes not counting the Q versions of the SCA-80. On the
other hand, it can be a bear getting the 'correct' manual for any of
the above... which version is it? Generally, I rebuild to the latest
version and add a few tweeks of my own. This does mean drilling the
driver boards and adding a few bits, but no big deal.

Cutting to the chase, having made a kit or three in my time, I gained
the confidence to tear into other equipment that came to me in various
stages of failure... usually with pretty good results. And certainly a
well designed kit properly assembled will give exactly the same results
as an equally well-designed 'factory' item properly assembled. In point
of fact, Dynaco did not even have a "factory" until they were purchased
by Tyco... their assembly line was Drexel students on piecework. I
visited the Hafler 'factory' in Pennsauken, NJ.... it was tiny,
consisted of a grade-level receiving dock, a small warehouse area
(maybe 1800 square feet), two offices and a lab/test bench. Period.
When I asked where their 'factory assembled' items were made, they
laughed and said: "Oh, various places nearby".

With Pacific Rim stuff, the models change so fast that there is none of
this continuity or ability to compare differences in result. And robot
assembly onto breakaway boards does not lead to easy troubleshooting.

Peter Wieck
Wyncote, PA

p.s: There are at least four variants of the 3a out there (_not
counting the earlier AR3_), five if one counts the revival version.
These variations affect both the driver manufacture and composition as
well as the crossover assemblies. I have two versions. Perhaps this
could account for the variations in measured impedance?

[[email protected]]

wrote:
wrote:

No. I have now been able to obtain, from a number of
sources, detailed impedance data on the AR3a to
complement the measurement data I made some years
ago. Across all this data, the lowest impedance over the
range 10 to about 40 kHz occurs around 780 Hz
and of all the sample, the lowest is 2.8 ohms, and this
is only with the level control set to one extreme. The only
other place it exhibits anything that low is around 110
Hz, where it's about 2.83 ohms. It remains above 3 ohms
from 10 Hz to about 85 Hz, from 145 Hz to abou 670 Hz,
and from 940 Hz on up.

If you say so. But as you are taking your data off a sheet vs. in the
field, permit me to merely suggest differently based on field
experience.

To amplify, I am NOT taking "my data off of a sheet." Rather,
I have gathered, from a number of associates in the
loudspeaker business, their MEASUREMENTS along with
my MEASUREMENTS. The data I described above comes
directly from those measurements, not "off of a sheet."

Pray tell, where does YOUR data come from?

[[email protected]]

wrote:
Now, as to tube equipment, I have typically used the
nominally higher taps, e.g. the 8-ohm taps for the 3as
from my ST-70 and LK-150. This gives less power,
but also less distortion and more stability, as well
as a slightly higher damping factor, all good things.

No, it doesn't, on the assumption that "damping factor"
is important, which it isn't.

The 8-ohm tap has a HIGHER output impedance and it
has a HIGHER output resistance than the 4-ohm tap. In
fact, the series output resistance of the transformer is
about 40% higher on the 8-ohm tap than it is on the 4-
ohm tap.

GIven that the "damping factor" is DEFINED as:

DF = Zload / Rsource

and since Rsource is 40% HIGHER on the 8 ohm tap
than on the 4, that measn the "damping factor: is about
30% LOWER.

Now as a completely random historical aside, the Dynaco ST-120 was
purportedly developed directly for the 3a, or so local legend has it.

Yes, that is a legend.

[Jerry]

Peter wrote on 8/25/2006:

Peter, why you NOT choose the taps that are closest to the actual
impedance?
When the impedance matches don't we get better power transmission and
less
power dissipation in our amp?

Yes but... I seldom demand the full output of the amp, so being able to
enjoy lower distortion and a higher damping factor into the 3as is a
good thing, as I noted before.

Yep, me too! I rarely listen to music at volume levels exceeding 1 watt
and most of the time I'm between .2 and .4 watts.

By the way, Peter, if you ever try horizontal bi-amping on your AR's pay
particular attention to music at LOW levels (.2 to .4 watts) as this is
where the changes are most pronounced.

Your ST-70??? Was this a Dynaco or and Eico? Reason I ask is that I
built
an Eico ST-70 and I read somewhere (actually I think it was in this
group)
that the Eico unit is a copy/clone of the Dynaco.

Dynaco, with good Mullard 6CA7s matched on my Hickok 539B. Note that
the "matching" lasted about 30 hours and then drifted into "close
enough", something that is far more typical than not. As long as the
bias remains rock-steady, things usually are fine.

On a conservative design "matching" should NOT make any difference as long
as the components are not way, way off.

I only keep it a year or two and traded up to an Eico solid state
receiver.
Now, this ss unit was similar in design to the AR amp. It had an
inter-stage transformer, but direct output to the speakers.

As I recall the Dynaco ST-120 was capacitively coupled to the speakers.
Is
this correct, Peter?

Yes, the same as the ST-80, but with the regulated power-supply.

Now, it is my personal belief that kit-building gives one confidence to
learn about the actual workings of these things, and to try a few
experiments. Furthermore, seeing makers re-design their products based
on real-world results can be fascinating, especially looking at those
companies that both had some longevity and also kept products in the
line for many years. The original AR line of products (tuner,
integrated amp, receiver) lasted about six years in production (?? Any
confirmation?) and they continued to support the product until their
ultimate demise.

AR amp was introduced in 1967 with a list price of $225 and I believe was
still in production up to the mid 70's. It's a fairly nice unit with driect
coupled output. Only thing between the output and the speakers is a fuse
(another good idea).

I have the latest version of their factory service
manual, printed in 1982, with multiple modifications to each piece.
Dynaco modified their ST-120, ultimately devolving to the ST-80, no
less than 11 times that I can count.. OK, perhaps fewer, but there are
11 obvious changes not counting the Q versions of the SCA-80. On the
other hand, it can be a bear getting the 'correct' manual for any of
the above... which version is it? Generally, I rebuild to the latest
version and add a few tweeks of my own. This does mean drilling the
driver boards and adding a few bits, but no big deal.

Cutting to the chase, having made a kit or three in my time, I gained
the confidence to tear into other equipment that came to me in various
stages of failure... usually with pretty good results. And certainly a
well designed kit properly assembled will give exactly the same results
as an equally well-designed 'factory' item properly assembled. In point
of fact, Dynaco did not even have a "factory" until they were purchased
by Tyco... their assembly line was Drexel students on piecework. I
visited the Hafler 'factory' in Pennsauken, NJ.... it was tiny,
consisted of a grade-level receiving dock, a small warehouse area
(maybe 1800 square feet), two offices and a lab/test bench. Period.
When I asked where their 'factory assembled' items were made, they
laughed and said: "Oh, various places nearby".

With Pacific Rim stuff, the models change so fast that there is none of
this continuity or ability to compare differences in result. And robot
assembly onto breakaway boards does not lead to easy troubleshooting.

Well, Peter, no question it is easier for the kit builder to apply
"upgrades". For one, the kit manufacturers would offer for sale revision
kits. You rarely see this in the Pacific Rim stuff.

Further, the very idea that someone who assembles for $'s is going to care
that much about the final product is ludicrous. Kit builders are interested
in more than just $'s and strive for the highest quality.


p.s: There are at least four variants of the 3a out there (_not
counting the earlier AR3_), five if one counts the revival version.
These variations affect both the driver manufacture and composition as
well as the crossover assemblies. I have two versions. Perhaps this
could account for the variations in measured impedance?

Absolutely, but never underestimate those blasted pots. They can account
for a lot of variation.

BTW, I finally solved the pot problem. They are gone!! Not in the circuit
anymore.

Regards,
Jerry

[---MIKE---]

I have two AR-3As. The woofers appear to have rubber surrounds. Is
that true of all of them or did some have foam surrounds?

---MIKE---
In the White Mountains of New Hampshire
(44° 15' N - Elevation 1580')

[Jerry]

Peter wrote on 8/25/2006:

Dynaco, with good Mullard 6CA7s matched on my Hickok 539B. Note that
the "matching" lasted about 30 hours and then drifted into "close
enough", something that is far more typical than not. As long as the
bias remains rock-steady, things usually are fine.


As I recall the Dynaco ST-120 was capacitively coupled to the speakers.
Is
this correct, Peter?

Yes, the same as the ST-80, but with the regulated power-supply.

Now, it is my personal belief that kit-building gives one confidence to
learn about the actual workings of these things, and to try a few
experiments. Furthermore, seeing makers re-design their products based
on real-world results can be fascinating, especially looking at those
companies that both had some longevity and also kept products in the
line for many years. The original AR line of products (tuner,
integrated amp, receiver) lasted about six years in production (?? Any
confirmation?) and they continued to support the product until their
ultimate demise. I have the latest version of their factory service
manual, printed in 1982, with multiple modifications to each piece.
Dynaco modified their ST-120, ultimately devolving to the ST-80, no
less than 11 times that I can count.. OK, perhaps fewer, but there are
11 obvious changes not counting the Q versions of the SCA-80. On the
other hand, it can be a bear getting the 'correct' manual for any of
the above... which version is it? Generally, I rebuild to the latest
version and add a few tweeks of my own. This does mean drilling the
driver boards and adding a few bits, but no big deal.

Cutting to the chase, having made a kit or three in my time, I gained
the confidence to tear into other equipment that came to me in various
stages of failure... usually with pretty good results. And certainly a
well designed kit properly assembled will give exactly the same results
as an equally well-designed 'factory' item properly assembled. In point
of fact, Dynaco did not even have a "factory" until they were purchased
by Tyco... their assembly line was Drexel students on piecework. I
visited the Hafler 'factory' in Pennsauken, NJ.... it was tiny,
consisted of a grade-level receiving dock, a small warehouse area
(maybe 1800 square feet), two offices and a lab/test bench. Period.
When I asked where their 'factory assembled' items were made, they
laughed and said: "Oh, various places nearby".

With Pacific Rim stuff, the models change so fast that there is none of
this continuity or ability to compare differences in result. And robot
assembly onto breakaway boards does not lead to easy troubleshooting.

Peter Wieck
Wyncote, PA

Peter, I have a terrific idea for you to try. Horizontal bi-amping your
AR-3a's with:

ST-80 powering the woofer
ST-70 powering mid-range and tweeter

I checked the schematics and both have common ground speaker outputs.

Peter the advantage of this arrangement is you let each amp perform in the
area they excel. That is, the ST-80 will have no problem with the 4 ohm
woofer load and the ST-70 should produce that "silky" upper range that folks
love.

Peter, this combination ought to produce a portfolio of sound that will be
hard to match.

Regards,
Jerry

[[email protected]]

---MIKE--- wrote:
I have two AR-3As. The woofers appear to have rubber surrounds. Is
that true of all of them or did some have foam surrounds?

Some had cloth surrounds.

[Jerry]

"---MIKE---" wrote in message
...
I have two AR-3As. The woofers appear to have rubber surrounds. Is
that true of all of them or did some have foam surrounds?

---MIKE---

Mike, when you say "rubber surrounds" do you mean the rather standard foam
rubber surrounds or the butyl rubber surrounds?

see below for a pic with butyl rubber surrounds:

http://cgi.ebay.com/Philips-6-inch-s...QQcmdZViewItem

If you have this type of surround in your AR-3a's it did NOT come that way
from AR. AR used initially a "coated" cloth surround and eventually
migrated to the ubiquitous foam surrounds.

Regards,
Jerry