[GerryE123]

Hi:

When I purchased my tube amp from a friend, I was told that it was set up
for the 8-ohm taps of the output transformers (5K primary and 4, 8 and 16
secondary). My speakers are rated at 8 ohms so I was all set.

I just found out that the amp is in fact set up for the 16 ohm taps. My
question is what are the theoretical sonic effects of using 16 ohm taps on 8
ohm speakers?

It's a SE 45 amp and of course there's no NFB. A person I talked to said
that it would effectively lower the load impedance that the output tubes see
and may attenuate the high frequencies. Does that sound right and would
there be any other effects? Thanks!

Gerry
P.S. Of course I'm going to change it to the 8 ohm taps.

[Phil Allison]

"GerryE123"

When I purchased my tube amp from a friend, I was told that it was set up
for the 8-ohm taps of the output transformers (5K primary and 4, 8 and 16
secondary). My speakers are rated at 8 ohms so I was all set.

I just found out that the amp is in fact set up for the 16 ohm taps. My
question is what are the theoretical sonic effects of using 16 ohm taps on
8 ohm speakers?

It's a SE 45 amp and of course there's no NFB. A person I talked to said
that it would effectively lower the load impedance that the output tubes
see and may attenuate the high frequencies. Does that sound right and
would there be any other effects? Thanks!


** There is no such thing as an 8 ohm speaker - there are only * nominal *
8 ohms speakers.

The effect of an impedance mismatch ( in either direction) is to reduce the
AVAILABLE power output of the amp.

Now, if you can tell us what the impedance of your speaker REALLY is at
each point in the audio band - a more precise reply is possible.



....... Phil

[GerryE123]

"Phil Allison" wrote:

** There is no such thing as an 8 ohm speaker - there are only * nominal
* 8 ohms speakers.

The effect of an impedance mismatch ( in either direction) is to reduce
the AVAILABLE power output of the amp.

Now, if you can tell us what the impedance of your speaker REALLY is at
each point in the audio band - a more precise reply is possible.

Fair enough Phil and thank you for the response. However, I did write "My
speakers are rated at 8 ohms...". The operative word being "rated". I
can't answer your question. The only other information I can suppy is that
both drivers measure 5.3 ohms DCR.

Gerry

[Phil Allison]

"GerryE123"
"Phil Allison"
** There is no such thing as an 8 ohm speaker - there are only *
nominal * 8 ohms speakers.

The effect of an impedance mismatch ( in either direction) is to reduce
the AVAILABLE power output of the amp.

Now, if you can tell us what the impedance of your speaker REALLY is at
each point in the audio band - a more precise reply is possible.

Fair enough Phil and thank you for the response. However, I did write "My
speakers are rated at 8 ohms...". The operative word being "rated". I
can't answer your question. The only other information I can supply is
that both drivers measure 5.3 ohms DCR.


** Suppose it is too much to ask you to supply the make and model.

Or are they home made junk like the amp.



....... Phil

[Patrick Turner]

GerryE123 wrote:

"Phil Allison" wrote:

** There is no such thing as an 8 ohm speaker - there are only * nominal
* 8 ohms speakers.

The effect of an impedance mismatch ( in either direction) is to reduce
the AVAILABLE power output of the amp.

Now, if you can tell us what the impedance of your speaker REALLY is at
each point in the audio band - a more precise reply is possible.

Fair enough Phil and thank you for the response. However, I did write "My
speakers are rated at 8 ohms...". The operative word being "rated". I
can't answer your question. The only other information I can suppy is that
both drivers measure 5.3 ohms DCR.

Gerry

The words "ratedat 8 ohms" means they should average 8 ohms across at
least the main
band of frequencies where most musical power resides, ie, 100Hz to 1kHz.

But very few "8 ohm" speakers have an average where the variation is
between 6 and 10 ohms.
There can be variations between 3 and 33 ohms.
The high Z won't matter at all because its easy to drive from the amp's
point of view,
but the 3 ohms could be a bother. So how come 3 ohms?
It can be because of the crossovers involved where the Z falls to say 6
ohms
for both the filters for bass and for midrange and at about the same F,
typically say 250Hz
where a lot is going on, and the two filters thus impose a load on the
amp of 3 ohms.

So you NEED to KNOW what the impedance curve is for the speakers if you
are concerned with good load matching.
AND you need to know the power curve for your amp for clipping into
various loadings.

Some tube amps have 4 outut terminals, Common, 2 ohms, 4 ohms, and 8
ohms.

If you test the clipping power from the 8 ohm outlet,
maybe you'll find maximum PO at no more than 1% THD occurs with 8 ohms,
falling each side in PO
as load is made more or less.

Sometimes the peak in PO occurs with say 6 ohms, or even lower, but many
makers ensure
an 8 ohm load tied to the 8 ohm outlet produces the maximum and
advertised rated PO for the amp.
Often in many amps, its a bad situation, because the load reflected to
the tubes is one for
nearly all class B operation.
The better sounding amps have the max PO produced at 4 ohms when using
the 8 ohm outlet, allowing a lower
PO into 8, but with lower THD and better DF.

But if your speakers have dips to 3 ohms, DON'T use the 8 ohm outlet,
because
the load on the tubes is too low, DF is poor, distortion is high.
Try the 2 ohm outlet. This is at the CT of the OPT secondary where the
full winding = 8 ohms.
Half the 8 ohm voltage is available at the 2 ohm outlet, and if there is
enough volume for you, stay
with this, because DF will be highest, and TH lowest, and tubes will
make the most class A PO.
the 4 ohm outlet if there is one is at 0.7 of the whole 8 ohm winding,
so
0.7 times the 8 ohm voltage is available, and if your speakers don't
have dips
below 4 ohms, I recommend it be used, if higher volume is wanted.

The amp must unconditionally stable, ie, able to drive any load, or not
be loaded at all,
and not oscillate. It doesn't mean a 1 ohm load is OK on the 8 ohm
outlet.
But it could indeed be used if the level is very low, and in most cases
where PO 0.5W,
a 1 ohm load won't sound different to when it was connected to the 4 or
2 ohm outlet.

Speaker loads vary widely with frequency, and when in doubt about the
actual Z, always use the lowest ohm outlet on the tube amp
which will be the least likely one to offer smoke instead of music.

Many people have not the slightest idea how to set up their tube amps
and speakers
to get a good load match. Its because they have no clue about impedance,
and even less about amplifier operation.

They often think 4 ohms is "easier" to drive than 16 ohms, but for a
given applied voltage,
4 times the current is needed for the 4 ohms, and so 4 ohms is harder to
drive.
1 ohm produces smoke very easily.
The more bricks you load on the truck, the harder it is to drive up the
hill with them.
Hence people get confused over ohms because its the opposite to common
sense.
Trying to explain the pros and cons of amplifier outlet Z figures is
often like
talking to a tree with many people. They just don't get it.

Patrick Turner.

[Patrick Turner]

GerryE123 wrote:

Hi:

When I purchased my tube amp from a friend, I was told that it was set up
for the 8-ohm taps of the output transformers (5K primary and 4, 8 and 16
secondary). My speakers are rated at 8 ohms so I was all set.

I just found out that the amp is in fact set up for the 16 ohm taps. My
question is what are the theoretical sonic effects of using 16 ohm taps on 8
ohm speakers?

It's a SE 45 amp and of course there's no NFB. A person I talked to said
that it would effectively lower the load impedance that the output tubes see
and may attenuate the high frequencies. Does that sound right and would
there be any other effects? Thanks!

Gerry
P.S. Of course I'm going to change it to the 8 ohm taps.

I should have read this before my last post, but the principles I
mentioned
are applicable.

Try the 4 ohm outlet first for your speakers.

If the sound is fine, and doesn't clip, then that's the best sound you
will get from a lone 45
with no loop NFB.

If it does clip too easily, moving to 8 ohms may not help much.

Either buy more powerful amps or get more **sensitive** speakers.

Using "8 ohm" speakers which may have a Z range of 3 to 33 ohms
on the 16 ohm outlet will dramatically increase THD, probably reduce PO
maximum available
without clipping, and make the Damping Factor as poor as possible.

And give a greater HF loss, but that's not your main bother.

Patrick Turner.

[GerryE123]

Phil Allison" wrote:

Suppose it is too much to ask you to supply the make and model.

Or are they home made junk like the amp.

Au contraire Phil. Only one of the top five cone drivers ever made:

http://i27.photobucket.com/albums/c1.../ob-woofer.jpg

For an update on this, see my response to Patrick

Gerry

[GerryE123]

"Patrick Turner" wrote:

I should have read this before my last post, but the principles I
mentioned
are applicable.

Try the 4 ohm outlet first for your speakers.

If the sound is fine, and doesn't clip, then that's the best sound you
will get from a lone 45
with no loop NFB.

If it does clip too easily, moving to 8 ohms may not help much.

Either buy more powerful amps or get more **sensitive** speakers.

Using "8 ohm" speakers which may have a Z range of 3 to 33 ohms
on the 16 ohm outlet will dramatically increase THD, probably reduce PO
maximum available
without clipping, and make the Damping Factor as poor as possible.

And give a greater HF loss, but that's not your main bother.

Thank you Patrick. My amp is driving the bass/mid-range driver directly, no
crossover in the way. The output transformers have 4, 8 and 16 ohm taps. I
switched them from the 16 ohm taps to the 8 ohm taps.

What stood out after the change is that any sonic differences were much less
than I expected! The sound *might* be just a bit smoother (less
distortion?) and that's about it! The speaker sensitivity is about 96db and
I also use a powered sub to fill in the last two octaves.

Gerry

[Patrick Turner]

GerryE123 wrote:

"Patrick Turner" wrote:

I should have read this before my last post, but the principles I
mentioned
are applicable.

Try the 4 ohm outlet first for your speakers.

If the sound is fine, and doesn't clip, then that's the best sound you
will get from a lone 45
with no loop NFB.

If it does clip too easily, moving to 8 ohms may not help much.

Either buy more powerful amps or get more **sensitive** speakers.

Using "8 ohm" speakers which may have a Z range of 3 to 33 ohms
on the 16 ohm outlet will dramatically increase THD, probably reduce PO
maximum available
without clipping, and make the Damping Factor as poor as possible.

And give a greater HF loss, but that's not your main bother.

Thank you Patrick. My amp is driving the bass/mid-range driver directly, no
crossover in the way. The output transformers have 4, 8 and 16 ohm taps. I
switched them from the 16 ohm taps to the 8 ohm taps.

What stood out after the change is that any sonic differences were much less
than I expected! The sound *might* be just a bit smoother (less
distortion?) and that's about it! The speaker sensitivity is about 96db and
I also use a powered sub to fill in the last two octaves.


You could even try the 4 ohm tap.

96dB is very sensitive compared to most modern speakers at about
88dB/W/M.

Does the the Altec driver in the image include treble?
guess it does because you say you have no crossovers, and a dedicated
treble should always have at least a capacitor in series.

Getting a sub to do below 80Hz does not relieve the
45 from making bass below 80Hz unless you have filtered it out.
If the 45 had its bass content filtered out before the amp,
then the mid-HF power range slightly increases, and IMD is much reduced,
because most SE amps produce most IMD because of their OPT character
struggling to stay clean at bass F.

Subs are terribly difficult to make bass sound real.


At very low power outputs, and with class A amps, load changes and
mismatches
don't make much difference to the sound.
If the distortion has gone from say 1% to 0.5% because you have moved
the speaker from
the 16 to the 8 outlet, then that THD reduction isn't going to be very
noticeable.

Remember, THD and IMD only reach alarming levels when the amp gets
towards clipping.
You probably have fine sound at PO = 1/20 of clipping levels.
THD varies as 1/VO, so that at 1/10 of say 2 watts, you have 1/3 of the
max VO,
so about 1/3 of the THD, and if THD max was 4%, then at 0.2W, THD =
1.3%,
and at lower levels it gets below 0.5%.

0.5% was regarded as the level at which THD became audible with a full
range system.


The spectral content of THD and IMD produced by a single class A triode
happens to be the least objectionable to most ppl's ears, and some folks
adore the resulting euphonic and rosy sound.

But I like the tube sound you get when THD and IMD
is very much lower than the 0.5% audible threshold.

I quite like the 2A3 which I think gives the nicest 4 watts you'll ever
get.

Patrick Turner.


Gerry

[John Byrns]

In article ,
"GerryE123" wrote:

Phil Allison" wrote:

Suppose it is too much to ask you to supply the make and model.

Or are they home made junk like the amp.

Au contraire Phil. Only one of the top five cone drivers ever made:

http://i27.photobucket.com/albums/c1.../ob-woofer.jpg

I am curious what the other four top cone drivers ever made are? I have a
nomination for one of them.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/

[GerryE123]

"John Byrns" wrote:

I am curious what the other four top cone drivers ever made are? I have a
nomination for one of them.

Not counting Jensen/Western Electric 18" woofers, my top five would be WE
728, 750, 754, 755, 756. These are "full-range", high sensitivity drivers
made with a special silk and cotton cone material. Sure, they are more
"wide-range" than "full-range" but they all cover the important range.

I'm curious, what's your nomination? BTW, I have owned 728, 755; I'm
currently using 756; and I have a pair of 754s on the way.

Gerry

[GerryE123]

"Patrick Turner" wrote:

You could even try the 4 ohm tap.

96dB is very sensitive compared to most modern speakers at about
88dB/W/M.

Does the the Altec driver in the image include treble?
guess it does because you say you have no crossovers, and a dedicated
treble should always have at least a capacitor in series.

Getting a sub to do below 80Hz does not relieve the
45 from making bass below 80Hz unless you have filtered it out.
If the 45 had its bass content filtered out before the amp,
then the mid-HF power range slightly increases, and IMD is much reduced,
because most SE amps produce most IMD because of their OPT character
struggling to stay clean at bass F.

Subs are terribly difficult to make bass sound real.


At very low power outputs, and with class A amps, load changes and
mismatches
don't make much difference to the sound.
If the distortion has gone from say 1% to 0.5% because you have moved
the speaker from
the 16 to the 8 outlet, then that THD reduction isn't going to be very
noticeable.

Remember, THD and IMD only reach alarming levels when the amp gets
towards clipping.
You probably have fine sound at PO = 1/20 of clipping levels.
THD varies as 1/VO, so that at 1/10 of say 2 watts, you have 1/3 of the
max VO,
so about 1/3 of the THD, and if THD max was 4%, then at 0.2W, THD =
1.3%,
and at lower levels it gets below 0.5%.

0.5% was regarded as the level at which THD became audible with a full
range system.


The spectral content of THD and IMD produced by a single class A triode
happens to be the least objectionable to most ppl's ears, and some folks
adore the resulting euphonic and rosy sound.

But I like the tube sound you get when THD and IMD
is very much lower than the 0.5% audible threshold.

I quite like the 2A3 which I think gives the nicest 4 watts you'll ever

Patrick:

I do use a "helper" tweeter as can be seen he

http://i27.photobucket.com/albums/c1...b-drivers1.jpg

Still, the 756B runs full-range and there's no xover between it and the amps
output transformers. I will give the 4-ohm taps a try. I need to do this
anyway because I have a pair of 754As on the way and they are 4-ohm speakers
(2.8 ohms DCR). The 754As are supposed to be even more sensitive than the
756s (significantly so), but I will have to verify that.

I have run 2A3s before and I agree, they are also very nice. Thanks.

Gerry

[tubegarden]

Hi RATs!

I like to listen to music. It is fun, occasionally, to listen to the
system, directly, ignoring content, like with test tones and pink and
white and rainbow noise, but as soon as anything vaguely rhythmic
starts, I am lost to cold reason.

I use woofers built by Nick McKinney, back when he was Lambda
Acoustics. He built some 15" for Dr, Bruse Edgar to use in his 80 Hz
horns. The work very well. The voice coil is rated "4 ohm" but when
measured installed in the horn, the impedance of the system is much
higher is much higher.

It is wonderful to build circuits as well as I am able.

It is insane to think I am doing it "correctly".

I am having as much fun as I can.

I trust my feeble ears

Trust yours 8^D

Happy Ears!
Al

[Patrick Turner]

GerryE123 wrote:

"Patrick Turner" wrote:

You could even try the 4 ohm tap.

96dB is very sensitive compared to most modern speakers at about
88dB/W/M.

Does the the Altec driver in the image include treble?
guess it does because you say you have no crossovers, and a dedicated
treble should always have at least a capacitor in series.

Getting a sub to do below 80Hz does not relieve the
45 from making bass below 80Hz unless you have filtered it out.
If the 45 had its bass content filtered out before the amp,
then the mid-HF power range slightly increases, and IMD is much reduced,
because most SE amps produce most IMD because of their OPT character
struggling to stay clean at bass F.

Subs are terribly difficult to make bass sound real.


At very low power outputs, and with class A amps, load changes and
mismatches
don't make much difference to the sound.
If the distortion has gone from say 1% to 0.5% because you have moved
the speaker from
the 16 to the 8 outlet, then that THD reduction isn't going to be very
noticeable.

Remember, THD and IMD only reach alarming levels when the amp gets
towards clipping.
You probably have fine sound at PO = 1/20 of clipping levels.
THD varies as 1/VO, so that at 1/10 of say 2 watts, you have 1/3 of the
max VO,
so about 1/3 of the THD, and if THD max was 4%, then at 0.2W, THD =
1.3%,
and at lower levels it gets below 0.5%.

0.5% was regarded as the level at which THD became audible with a full
range system.


The spectral content of THD and IMD produced by a single class A triode
happens to be the least objectionable to most ppl's ears, and some folks
adore the resulting euphonic and rosy sound.

But I like the tube sound you get when THD and IMD
is very much lower than the 0.5% audible threshold.

I quite like the 2A3 which I think gives the nicest 4 watts you'll ever

Patrick:

I do use a "helper" tweeter as can be seen he

http://i27.photobucket.com/albums/c1...b-drivers1.jpg

Still, the 756B runs full-range and there's no xover between it and the amps
output transformers. I will give the 4-ohm taps a try. I need to do this
anyway because I have a pair of 754As on the way and they are 4-ohm speakers
(2.8 ohms DCR). The 754As are supposed to be even more sensitive than the
756s (significantly so), but I will have to verify that.

I have run 2A3s before and I agree, they are also very nice. Thanks.

Gerry

You do have a cap in front of the tweeter, and it does constitute a
filter element
and there is therefore a crossover, if I was being strict.

Just as well you do have that cap there, because without it the tweeter
cops a lot of LF signal which does the tweeter no good, and
could ruin the HF sound with IMD products. But its not obvious of course
if the tweeter
begins to operate above say 3 kHz.

A simple cap is better than none, but IMHO, you'd do better to have
impedance equalisation R&C across the tweeter as well, and have an over
damped second
order filter ahead of the tweeter, ie, series C followed with shunt L so
that the
tweeter Z is lower than the critical R value required for a non peaked F
response
at cut off.
Tweeters have a peak in the Z at their Fo, maybe 1.2kHz, where Z is
high,
and as cap reactance rises as F falls, it still transfers energy into
the Z at Fo.
So the actual roll off of F going into the tweeter isn't like a cap
feeding an R;
there maybe a peak there.

Many people don't like crossovers filters, but once you understand them,
then you do get good sounding results, but to achieve this you need good
measuring gear,
ie, pink noise, good mic, and a 1/3 octave switchable filter with Q
about 12.
But that's old fashioned, and better is to have a PC program that
digitises the mic signal and applies analysis,
and instantly displays a mic response and saves it after each change of
the mic position
in a room. After say 4 takes, they can be averaged, and its a good
indicator of what you really have.
When you change L or C or R values, you can watch how the response
changes.
And sometimes a small change of L, C, or R can cause a phase change that
makes a serious peak or dip appear in the response.

Without measurements that are fairly good, you'll never get the best
sound you could get from a given
choice of drivers arrayed together.

And measuremens show what happens if you try to reverse phase connect a
tweeter
in respect to a midrange; and again you could get an unwanted peak or
null
and probably, the peaks between 2 and 7khz have the worst effect to make
sound a bit harsh
and bright.
So you should know what the midrange is doing at the top end of its BW.
And filter it out to allow the tweeter to work without competition.

Its luck alone if you get two drivers that measure and sound are best
with a bare minimum of
filtering as you have.


Patrick Turner.

[John Byrns]

In article ,
"GerryE123" wrote:

"John Byrns" wrote:

I am curious what the other four top cone drivers ever made are? I have a
nomination for one of them.

Not counting Jensen/Western Electric 18" woofers, my top five would be WE
728, 750, 754, 755, 756. These are "full-range", high sensitivity drivers
made with a special silk and cotton cone material. Sure, they are more
"wide-range" than "full-range" but they all cover the important range.

I'm curious, what's your nomination? BTW, I have owned 728, 755; I'm
currently using 756; and I have a pair of 754s on the way.

My nomination is the STEPHENS TRUSONIC 80FR. They are a fantastic full range
driver. I have measured the T/S properties of mine. The efficiency is about 96
dB/Watt/Meter. The rated impedance is 16 Ohms, but mine look more like 8 Ohm
drivers.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/

[GerryE123]

"John Byrns" wrote:

My nomination is the STEPHENS TRUSONIC 80FR. They are a fantastic full
range
driver. I have measured the T/S properties of mine. The efficiency is
about 96
dB/Watt/Meter. The rated impedance is 16 Ohms, but mine look more like 8
Ohm
drivers.

Very good John. I have no personal experience with the 80FR, but I have
heard people say it's competitive with the Altec 755A. Given that 755As
have doubled (or even tripled) in price over the last five years or so, if
the 80FR is even close to the 755A, it could be the VALUE leader of vintage
"full-range" speakers. What's the Qts? Also, have you tried it on an open
baffle?

Gerry

[John Byrns]

In article ,
"GerryE123" wrote:

"John Byrns" wrote:

My nomination is the STEPHENS TRUSONIC 80FR. They are a fantastic full
range
driver. I have measured the T/S properties of mine. The efficiency is
about 96
dB/Watt/Meter. The rated impedance is 16 Ohms, but mine look more like 8
Ohm
drivers.

Very good John. I have no personal experience with the 80FR, but I have
heard people say it's competitive with the Altec 755A. Given that 755As
have doubled (or even tripled) in price over the last five years or so, if
the 80FR is even close to the 755A, it could be the VALUE leader of vintage
"full-range" speakers. What's the Qts?

Qts = 0.50

Also, have you tried it on an open baffle?

I use them in sealed boxes, I like the sound of sealed boxes. I tried them in
reflex enclosures but I don't like the reflex sound, plus the high air velocity
in the port caused noise. I haven't tried an open baffle, I have a second pair,
perhaps I should try them in some sort of an open baffle.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/

[GerryE123]

"John Byrns" wrote:

Qts = 0.50

I use them in sealed boxes, I like the sound of sealed boxes. I tried
them in
reflex enclosures but I don't like the reflex sound, plus the high air
velocity
in the port caused noise. I haven't tried an open baffle, I have a second
pair,
perhaps I should try them in some sort of an open baffle.

JB:

You must try that second pair on OBs! That's a very good Qts for open
baffles.

I originally I had my 756Bs in WE designed 2.5 cubic ft. slant-baffle,
sealed box cabinets. As a lark, I tried them on OBs. They never did make
it back to the sealed boxes.

You can use the JE Labs design for your OBs (a copy of a Japanese design):

http://members.myactv.net/~je2a3/open.htm

I'll end this on a related funny note. I wanted nice open baffles so I had
them professionally built by an expert cabinet maker. When I brought them
home, my wife took one look at them and said these have to be the dumbest
thing you ever did related to audio!

I had the last laugh when she heard the 756Bs on them for the first time and
she stood there in amazement!

Gerry

[John Byrns]

In article ,
"GerryE123" wrote:

"John Byrns" wrote:

Qts = 0.50

I use them in sealed boxes, I like the sound of sealed boxes.
I tried them in reflex enclosures but I don't like the reflex
sound, plus the high air velocity in the port caused noise.
I haven't tried an open baffle, I have a second pair, perhaps
I should try them in some sort of an open baffle.

JB:

You must try that second pair on OBs! That's a very good Qts for open
baffles.

I originally I had my 756Bs in WE designed 2.5 cubic ft. slant-baffle,
sealed box cabinets. As a lark, I tried them on OBs. They never did make
it back to the sealed boxes.

You can use the JE Labs design for your OBs (a copy of a Japanese design):

http://members.myactv.net/~je2a3/open.htm

That's a fascinating article; it was interesting to read that G.A. Briggs didn't
get the idea for his baffle until 1956, and that his inspiration was the Quad
electrostatic speaker. The article has one problem, it references the "Piano
Chart, Fig. 9/1" but Fig. 9/1 is nowhere to be seen. I built one of Briggs'
"sand baffles" while I was in High School, after reading about it in a book he
had written, it was a large magazine size paper back book about 3/4 inch thick,
although the name of the book escapes me now. The interesting thing is that I
built the speaker system in the summer of either 1957 or 1958, I forget which,
and Briggs had already written about it in a book, I assumed that its roots went
further back. The system used two drivers, a 12-inch driver and an 8-inch
driver with a slot to increase the horizontal dispersion at high frequencies.

Perhaps I should try a pair for old times sake, although their size is really
too large to be practical for me today. Today I prefer sealed boxes tuned for a
Q of about 0.707, which is a more practical size and easier to place in a room,
especially now that two are needed for stereo.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/

[Andre Jute[_2_]]

On Sep 21, 12:15 am, John Byrns wrote:
In article ,



"GerryE123" wrote:
"John Byrns" wrote:

Qts = 0.50

I use them in sealed boxes, I like the sound of sealed boxes.
I tried them in reflex enclosures but I don't like the reflex
sound, plus the high air velocity in the port caused noise.
I haven't tried an open baffle, I have a second pair, perhaps
I should try them in some sort of an open baffle.

JB:

You must try that second pair on OBs! That's a very good Qts for open
baffles.

I originally I had my 756Bs in WE designed 2.5 cubic ft. slant-baffle,
sealed box cabinets. As a lark, I tried them on OBs. They never did make
it back to the sealed boxes.

You can use the JE Labs design for your OBs (a copy of a Japanese design):

http://members.myactv.net/~je2a3/open.htm

That's a fascinating article; it was interesting to read that G.A. Briggs didn't
get the idea for his baffle until 1956, and that his inspiration was the Quad
electrostatic speaker. The article has one problem, it references the "Piano
Chart, Fig. 9/1" but Fig. 9/1 is nowhere to be seen.

The so-called article is the entire chapter on Baffles from the book
Loudspeakers by G A Briggs, from p169 forward in the final edition.
The Piano Chart belongs to another chapter. I have photographed it and
posted it to the Discussion Circuits Page of Jute on Amps:
http://members.lycos.co.uk/fiultra/D...20Circuits.htm
The photo is not brilliant but there is nothing here that the average
RAT doesn't daily do as mental arithmetic. The illustration shows a
piano keyboard with next to it columns for the frequency of each key,
the wavelength in inches or feet of each frequency, and the minimum
diameter of an open baffle suspended in free air to reproduce down to
the frequency involved. The diameter is the same as the room length
required to reproduce down to the frequecy involved. The piano runs
from the A below bottom C, 27.5Hz, 40ft wave, 20ft minimum diameter
through the C above middle C, 523Hz, 2ft wave, 1ft diam OB, to top C,
4186 cycles, wavelength 3.25in, no OB too small to reproduce it, so
the Diameter column is blank.

I built one of Briggs'
"sand baffles" while I was in High School, after reading about it in a book he
had written, it was a large magazine size paper back book about 3/4 inch thick,
although the name of the book escapes me now.

Briggs wrote many books and it is possible that his American
publishers jazzed up his presentation or layout for their own market.
The format you describe sounds suspiciously American to me, unlikely
to have originated in the first instance at Rank Wharfedale,
considering the period and indeed Mr Brigg's age and background.

The interesting thing is that I
built the speaker system in the summer of either 1957 or 1958, I forget which,
and Briggs had already written about it in a book, I assumed that its roots went
further back. The system used two drivers, a 12-inch driver and an 8-inch
driver with a slot to increase the horizontal dispersion at high frequencies.

Loudspeakers, first published in 1948, features many designs. What you
describe is shown at p181 as Figure 17/10 and should be in the
material referred to above which has been copied. I'm surprised that
you didn't recognize it.

Perhaps I should try a pair for old times sake, although their size is really
too large to be practical for me today. Today I prefer sealed boxes tuned for a
Q of about 0.707, which is a more practical size and easier to place in a room,
especially now that two are needed for stereo.

I'm not so sure that mono is all that much inferior if you have a
really good loudspeaker that couples well to the walls and other
surfaces of your room. Horns and all kinds of panel speakers
(electrostats, open baffles) really lend themselves to mono
reproduction.

One thing about open baffles which hasn't been mentioned yet (because
you guys both already own elite speakers for the lucky few) is that
they can make cheap drivers sound very good indeed, because you can
just pile on cheap drivers, each operating in a noiseless low-output
band, and build up enough decibels by weight of numbers, much like a
poor man's Bessel Array. About ten years ago I published a 7/11 scheme
in Glass Audio to use four little ali drivers that cost about five
bucks each at Mouser, and they made a really super speaker; Dan
Schmalle of Elecronic Tonalities in Poulsbo, WA, published several
designs for them in VALVE.

Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review

[John Byrns]

In article ,
Andre Jute wrote:

On Sep 21, 12:15 am, John Byrns wrote:
In article ,

"GerryE123" wrote:
"John Byrns" wrote:

Qts = 0.50

I use them in sealed boxes, I like the sound of sealed boxes.
I tried them in reflex enclosures but I don't like the reflex
sound, plus the high air velocity in the port caused noise.
I haven't tried an open baffle, I have a second pair, perhaps
I should try them in some sort of an open baffle.

JB:

You must try that second pair on OBs! That's a very good Qts for open
baffles.

I originally I had my 756Bs in WE designed 2.5 cubic ft. slant-baffle,
sealed box cabinets. As a lark, I tried them on OBs. They never did
make
it back to the sealed boxes.

You can use the JE Labs design for your OBs (a copy of a Japanese
design):

http://members.myactv.net/~je2a3/open.htm

That's a fascinating article; it was interesting to read that G.A. Briggs
didn't
get the idea for his baffle until 1956, and that his inspiration was the
Quad
electrostatic speaker. The article has one problem, it references the
"Piano
Chart, Fig. 9/1" but Fig. 9/1 is nowhere to be seen.

The so-called article is the entire chapter on Baffles from the book
Loudspeakers by G A Briggs, from p169 forward in the final edition.
The Piano Chart belongs to another chapter. I have photographed it and
posted it to the Discussion Circuits Page of Jute on Amps:
http://members.lycos.co.uk/fiultra/D...20Circuits.htm
The photo is not brilliant but there is nothing here that the average
RAT doesn't daily do as mental arithmetic.

That is certainly an understatement!

The illustration shows a
piano keyboard with next to it columns for the frequency of each key,
the wavelength in inches or feet of each frequency, and the minimum
diameter of an open baffle suspended in free air to reproduce down to
the frequency involved. The diameter is the same as the room length
required to reproduce down to the frequecy involved. The piano runs
from the A below bottom C, 27.5Hz, 40ft wave, 20ft minimum diameter
through the C above middle C, 523Hz, 2ft wave, 1ft diam OB, to top C,
4186 cycles, wavelength 3.25in, no OB too small to reproduce it, so
the Diameter column is blank.

I built one of Briggs'
"sand baffles" while I was in High School, after reading about it in a book
he
had written, it was a large magazine size paper back book about 3/4 inch
thick,
although the name of the book escapes me now.

Briggs wrote many books and it is possible that his American
publishers jazzed up his presentation or layout for their own market.
The format you describe sounds suspiciously American to me, unlikely
to have originated in the first instance at Rank Wharfedale,
considering the period and indeed Mr Brigg's age and background.

The interesting thing is that I
built the speaker system in the summer of either 1957 or 1958, I forget
which,
and Briggs had already written about it in a book, I assumed that its roots
went
further back. The system used two drivers, a 12-inch driver and an 8-inch
driver with a slot to increase the horizontal dispersion at high
frequencies.

Loudspeakers, first published in 1948, features many designs. What you
describe is shown at p181 as Figure 17/10 and should be in the
material referred to above which has been copied. I'm surprised that
you didn't recognize it.

Actually I did recognize it, I just didn't mention it. Presumably this baffle
design wasn't included in the 1948 edition, as Chapter 17 says it wasn't until
1956 that he came up with the design after he was inspired by seeing the QUAD
electrostatic panel.

--
Regards,

John Byrns

Surf my web pages at, http://fmamradios.com/

[Andre Jute[_2_]]

On Sep 24, 12:42*am, John Byrns wrote:
In article ,
*Andre Jute wrote:



On Sep 21, 12:15 am, John Byrns wrote:
In article ,

*"GerryE123" wrote:
"John Byrns" wrote:

Qts = 0.50

I use them in sealed boxes, I like the sound of sealed boxes.
I tried them in reflex enclosures but I don't like the reflex
sound, plus the high air velocity in the port caused noise.
I haven't tried an open baffle, I have a second pair, perhaps
I should try them in some sort of an open baffle.

JB:

You must try that second pair on OBs! *That's a very good Qts for open
baffles.

I originally I had my 756Bs in WE designed 2.5 cubic ft. slant-baffle,
sealed box cabinets. *As a lark, I tried them on OBs. *They never did
make
it back to the sealed boxes.

You can use the JE Labs design for your OBs (a copy of a Japanese
design):

http://members.myactv.net/~je2a3/open.htm

That's a fascinating article; it was interesting to read that G.A. Briggs
didn't
get the idea for his baffle until 1956, and that his inspiration was the
Quad
electrostatic speaker. *The article has one problem, it references the
"Piano
Chart, Fig. 9/1" but Fig. 9/1 is nowhere to be seen.

The so-called article is the entire chapter on Baffles from the book
Loudspeakers by G A Briggs, from p169 forward in the final edition.
The Piano Chart belongs to another chapter. I have photographed it and
posted it to the Discussion Circuits Page of Jute on Amps:
http://members.lycos.co.uk/fiultra/D...20Circuits.htm
The photo is not brilliant but there is nothing here that the average
RAT doesn't daily do as mental arithmetic.

That is certainly an understatement!



The illustration shows a
piano keyboard with next to it columns for the frequency of each key,
the wavelength in inches or feet of each frequency, and the minimum
diameter of an open baffle suspended in free air to reproduce down to
the frequency involved. The diameter is the same as the room length
required to reproduce down to the frequecy involved. *The piano runs
from the A below bottom C, 27.5Hz, 40ft wave, 20ft minimum diameter
through the C above middle C, 523Hz, 2ft wave, 1ft diam OB, to top C,
4186 cycles, wavelength 3.25in, no OB too small to reproduce it, so
the Diameter column is blank.

I built one of Briggs'
"sand baffles" while I was in High School, after reading about it in a book
he
had written, it was a large magazine size paper back book about 3/4 inch
thick,
although the name of the book escapes me now.

Briggs wrote many books and it is possible that his American
publishers jazzed up his presentation or layout for their own market.
The format you describe sounds suspiciously American to me, unlikely
to have originated in the first instance at Rank Wharfedale,
considering the period and indeed Mr Brigg's age and background.

The interesting thing is that I
built the speaker system in the summer of either 1957 or 1958, I forget
which,
and Briggs had already written about it in a book, I assumed that its roots
went
further back. *The system used two drivers, a 12-inch driver and an 8-inch
driver with a slot to increase the horizontal dispersion at high
frequencies.

Loudspeakers, first published in 1948, features many designs. What you
describe is shown at p181 as Figure 17/10 and should be in the
material referred to above which has been copied. I'm surprised that
you didn't recognize it.

Actually I did recognize it, I just didn't mention it. *Presumably this baffle
design wasn't included in the 1948 edition, as Chapter 17 says it wasn't until
1956 that he came up with the design after he was inspired by seeing the QUAD
electrostatic panel.

"Revised and enlarged" new editions can mean anything, and in a few
years can make a book still bearing the same title a very different
animal. I imagine Mr Briggs was human, and wanted to put his latest
invention in the latest edition of his book, and that's what you saw,
hot off the press.

However that may be, Gilbert Brigg's Loudspeakers in any edition is
one of the very best books an audiophile can have on his shelves.

Andre Jute
Name recognition is the name of the fame game -- Hollywood saw