[Carey Carlan]

A program on TV about refrigeration with sound waves got me reading.

A navy project has created a refrigeration system that uses acoustic waves
to move heat down a tube, creating a warm end and a cold end, IOW a
refrigerator. One example used a device that produced an effective 190 dB
level within the tube. Another, more current, device uses 10 KW of power
at an 85% electric to audio (electracoustic) conversion efficiency. Damn.

There's absolutely no link between our speaker drivers and these devices
beyond the fundamental physics, but wouldn't it be cool to have a speaker
work at 85% efficiency? You could practically run your stereo off a 9V
battery.

[Scott Dorsey]

Carey Carlan wrote:
A program on TV about refrigeration with sound waves got me reading.

A navy project has created a refrigeration system that uses acoustic waves
to move heat down a tube, creating a warm end and a cold end, IOW a
refrigerator. One example used a device that produced an effective 190 dB
level within the tube. Another, more current, device uses 10 KW of power
at an 85% electric to audio (electracoustic) conversion efficiency. Damn.

There's absolutely no link between our speaker drivers and these devices
beyond the fundamental physics, but wouldn't it be cool to have a speaker
work at 85% efficiency? You could practically run your stereo off a 9V
battery.

I can build you a speaker with very high efficiency indeed, if it only
has to work at a single frequency.

Even better, if it can be very large with respect to a wave, you can do
a whole lot.

Efficiency on narrowband piezo transducers used for ultrasonic stuff is
very, very good compared with the efficiency of a Baby Advent.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Chris Hornbeck]

On Sun, 16 Mar 2008 00:49:54 GMT, Carey Carlan
wrote:

A program on TV about refrigeration with sound waves got me reading.

There's absolutely no link between our speaker drivers and these devices
beyond the fundamental physics, but wouldn't it be cool to have a speaker
work at 85% efficiency? You could practically run your stereo off a 9V
battery.

One thing about loudspeakers pretty much buzz-kills it though.
Radiation to one side of a moving diaphragm is half of its
energy, so unless ya can count the rear radiation, max
efficiency is fi'ty percent.

The big magnet compression drivers, (JBL 2445, etc.) with horn
loading, actually deliver about 30% conversion efficiency over
their optimal and resistively loaded range, which is pretty great
for a real-word transducer.

I've heard KlipschHorns run from an old-fashioned transistor
radio - plenty of volume. Their 104dB SPL/1W/1M sensitivity
(actually a pretty good estimate) and their estimated 8-ish-%
conversion efficiency is near the limit of "full-range"
conventional box speakers, depending on definitions.

One perhaps surprising counter-example is an electrostatically
driven light-weight diaphragm (the case only requires the
diaphragm to be light in relation to surrounding air, not
difficult to manage) and either a definition of efficiency
that doesn't include reactive losses, or a driving amplifier
that can re-use the reactive currents (do-able in modern
contexts).

And, at another level, anytime some TV show starts talking
about 50% efficiencies, I start to squirm. Most of the
world lives in Carnot cycle limits and most of the rest is two-
sided, and has fi'ty percent limits. Lots is both.

You raise a cool parallel to the Zoom threads; where do we
go from here, two decades down the road? (When the world
looks like an early Mel Gibson movie, or, who knows ....?)


Much thanks, as always,

Chris Hornbeck
"It's for compatibility with 8-Track."
--scott

[Chris Hornbeck]

On Sun, 16 Mar 2008 00:44:39 -0400, "Soundhaspriority"
wrote:

You raise a cool parallel to the Zoom threads; where do we
go from here, two decades down the road? (When the world
looks like an early Mel Gibson movie, or, who knows ....?)

An industrial air conditioning system that's been outside for a few years
DOES look like a Mad Max contraption

Air conditioning, such a mundane, pedestrian thing
(as we were raised, anywho) is now turning out to be
one the most important things in the world. At least,
as far as it effects our grandchildren. Who knew?

But who'd have predicted that gasoline would cost
half a minimum-wage-hour per gallon? And that some
folks (me included) would believe that the price is
still too low? It's Mad Max, only moreso. Classically
true for science fiction; it's always optimistic; see
_2001_ for an especially depressingly optimistic example.

Our responsibilities to future generations seem almost
unattainable, given all current circumstances. Bums me
the **** out.

Through most of recorded history, there was only one real
civilization, and that was in China. They're back, over
a billion strong and we'd better look out. Adaptation
isn't an option. Threats aren't an option when they're buying
our paper (debt). The only option is enlightenment, here
and there. Fat chance.


Bitch, bitch, bitch. Sorry.

Chris Hornbeck
"It's for compatibility with 8-Track."
--scott

[Chris Hornbeck]

On Sun, 16 Mar 2008 01:36:02 -0400, "Soundhaspriority"
wrote:

The future is Malthusian.

Finally, I'm sure you're right. It's just that I was raised
to expect more. I got it all, but don't have it to leave to
children and grandchildren.


Feel fortunate you lived in the one
golden moment, in the one golden place, in the history of the world.

I've always said that the only important thing that I ever
did was to be born male in America in 1950 and passable as white.
It's been downhill all the rest of the way.

I've never been ungrateful (and seldom dead), and I try to
appreciate my circumstance, at least as well as a mortal can
(which isn't all that much, historically speaking).

But yeah, I feel fortunate every single day. Come to think
of it. I really do.


And make merriment with music, because you are not obliged to suffer
your soul with the mistakes of mankind.


Of course I'm obliged to suffer@! It's in the secret blood
ceremony that all bleeding-heart liberals must endure. Oh,
wait. You haven't done that....


OOps, sorry. Forget about the ceremony stuff. Just kidding.
Ha, ha,

Just our little joke, okay?


Chris Hornbeck
"It's for compatibility with 8-Track."
--scott

[geezer[_2_]]

On Mar 15, 11:33*pm, Chris Hornbeck
wrote:
On Sun, 16 Mar 2008 00:49:54 GMT, Carey Carlan
wrote:

I've heard KlipschHorns run from an old-fashioned transistor
radio - plenty of volume.


Yeah, I remember my first exposure to the classic KlipschHorn about 30
years ago... The only positive thing I could say about them was
'plenty of volume'. I'd heard so much about them, it was damn near
discouraging how bad I thought they sounded, especially compared to my
recently acquired Avid 103s which had been a fraction of the
price... boy, I wish I still had them around.

-glenn

[Chris Hornbeck]

On Sat, 15 Mar 2008 23:26:50 -0700 (PDT), geezer
wrote:

Yeah, I remember my first exposure to the classic KlipschHorn about 30
years ago... The only positive thing I could say about them was
'plenty of volume'. I'd heard so much about them, it was damn near
discouraging how bad I thought they sounded, especially compared to my
recently acquired Avid 103s which had been a fraction of the
price... boy, I wish I still had them around.

There's no doubt that the K horns had/have all kinds of
fatal flaws. 2mS delay errors between tweeter and midrange,
another 2mS between midrange and woofer, just for starters.

A fatally flawed conception of horn flare areas (based on
the historically ubiquitous but brain-dead assumption of
flat/planar wavefronts) for another.

The contemporary (when we were in some kinda school) idea
that on-axis response was a total-enough picture, encouraging
horn designs with narrowing axis' with frequency above
the driver's mass rolloff. This was not common - it was
universal! - at the time. For another.


But, weirdly, even today they have lower amplitude
distortions than most contemporary loudspeakers. Lots
of "issues", yeah, but not a lot of extra notes.

To use them happily in a modern home setting is very difficult,
but not impossible. Tri-amping with time delays and steeper
crossovers is a good start, and a "comfortable" listening
distance, reflecting the interdriver distances, helps.

Also, with modern subwoofers, the LaScala model is
maybe more appropriate. This is IMO the best midrange
(100-2500 Hz) driver available, to some perverted definition
of "best", anyway. And allows easier, but not easy, placement.

The antique Heil AMT tweeters are an appropriate match,
both in radiation pattern and sensitivity (ain't THAT
a surprise?), and you might strongly prefer them to
the factory T35's. It's especially important to move
the crossover down about an octave - maybe 2500 or
3KHz.

LaScala's also "stack" well, with the "top" upside-down.
This is probably more than most folks want to know about
loudspeaker sex....

Sorry for the NC17 stuff, but the world needs to know,
or maybe not,

But much thanks, as always,

Chris Hornbeck
"It's for compatibility with 8-Track."
--scott

[William Sommerwerck]

"Carey Carlan" wrote in message
...

There's absolutely no link between our speaker drivers and these
devices beyond the fundamental physics, but wouldn't it be cool
to have a speaker work at 85% efficiency? You could practically
run your stereo off a 9V battery.

Why would you want to?

I believe horn systems have efficiencies in the range of 10% to 25%, which
is much higher than the 1% to 3% of box systems. They require only a few
watts to play at high levels.

[William Sommerwerck]

"Soundhaspriority" wrote in message
...

S'ats alright. The future is Malthusian. Feel fortunate you lived
in the one golden moment, in the one golden place, in the history
of the world. And make merriment with music, because you are not
obliged to suffer your soul with the mistakes of mankind.

When I think of such things, I'm grateful that I'll live probably no longer
than another 20 years, and won't have to suffer much through the horrible
disaster we will experience.

[Arny Krueger]

"Chris Hornbeck" wrote in
message


But who'd have predicted that gasoline would cost
half a minimum-wage-hour per gallon? And that some
folks (me included) would believe that the price is
still too low? It's Mad Max, only moreso. Classically
true for science fiction; it's always optimistic; see
_2001_ for an especially depressingly optimistic example.

Hmm, when minimum wage was $0.65 per hour, gas didn't miss being half a
minimum-wage hour by that much.

Been there, done that!

[Arny Krueger]

"Chris Hornbeck" wrote in
message
On Sun, 16 Mar 2008 00:49:54 GMT, Carey Carlan

Radiation to one side of a moving diaphragm is
half of its energy, so unless ya can count the rear radiation, max
efficiency is fi'ty percent.

Just because you trap the back wave, doesn't mean that the energy is lost.
If you use it to compress air and then allow the air to expand, you get most
of the energy back.

The big magnet compression drivers, (JBL 2445, etc.) with
horn loading, actually deliver about 30% conversion
efficiency over their optimal and resistively loaded
range, which is pretty great for a real-word transducer.

Furthermore, if you design the waveguide right, you can use compression
driver technology to produce a darn good-sounding speaker.

I've heard KlipschHorns run from an old-fashioned
transistor radio - plenty of volume. Their 104dB SPL/1W/1M
sensitivity (actually a pretty good estimate) and their
estimated 8-ish-% conversion efficiency is near the limit
of "full-range" conventional box speakers, depending on
definitions.

Live sound, anybody?

That's where drivers like the 2445 are still used. If you want to make a big
enough sound, the economies of scale are pretty good.

And, at another level, anytime some TV show starts talking
about 50% efficiencies, I start to squirm. Most of the
world lives in Carnot cycle limits and most of the rest
is two- sided, and has fi'ty percent limits. Lots is both.

Agreed.

[Andy[_5_]]

"William Sommerwerck" wrote:

When I think of such things, I'm grateful that I'll live probably no longer
than another 20 years, and won't have to suffer much through the horrible
disaster we will experience.

Like neural computer hacking and floating car smash-ups ?

"I didn't hear him coming Robocop A7, honest, please, don't phaze me, Robo...".

[Scott Dorsey]

Chris Hornbeck wrote:
There's no doubt that the K horns had/have all kinds of
fatal flaws. 2mS delay errors between tweeter and midrange,
another 2mS between midrange and woofer, just for starters.

A fatally flawed conception of horn flare areas (based on
the historically ubiquitous but brain-dead assumption of
flat/planar wavefronts) for another.

"They made my guitar go straight ahead for miles and sound like
it was coming through a telephone."
-- Steve Miller on the La Scala


--
"C'est un Nagra. C'est suisse, et tres, tres precis."