I'm preparing to build a subwoofer, using two 12" drivers. Is the internal
enclosure volume double the speaker maker's specification for a single unit?
TIA

"François Yves Le Gal" wrote in message
...
On Thu, 16 Mar 2006 09:42:37 -0600, "PanHandler"
wrote:

I'm preparing to build a subwoofer, using two 12" drivers. Is the internal
enclosure volume double the speaker maker's specification for a single
unit?

If they aren't mounted "Isobarik" style, yes.

Thank you. Additionally, how do I determine the volume of the drivers
themselves? My understanding is that this spec must be added to the
enclosure volume recommended by the driver manufacturer. Or is this taken
into consideration when they determine their recommended volume?

"François Yves Le Gal" wrote in message
...
On Thu, 16 Mar 2006 11:08:54 -0600, "PanHandler"
wrote:

Additionally, how do I determine the volume of the drivers
themselves?

Simple geometry. Simplify the shape, consider the driver a truncated cone
and calculate it's volume.

My understanding is that this spec must be added to the
enclosure volume recommended by the driver manufacturer.

Not needed in this context : if you go for a set volume, it'll be quite
approximative when compared to an optimized alignment.

What speakers are you planning to use ?

They're Logic CLX 12's, rated at 4ohms, 600W max, 300W RMS. The amp is a
Logic 4 channel PLX 4800, 350W/ch 2 ohms, 175W/ch 4 ohms. bridgeable, H/L
variable bandpass, usual bells and whistles. Went with Logic based on good
past performance of older equipment.
I appreciate your attention!
Joe Arnold


http://www.logicsoundlab.com/CLX12.html Drivers
No URL for Amp - it was just released, not on website yet.

"PanHandler" wrote in message
...
I'm preparing to build a subwoofer, using two 12" drivers. Is the internal
enclosure volume double the speaker maker's specification for a single
unit?
TIA

BTW, I should have mentioned that it will be a sealed box.
Joe

In article , "PanHandler" wrote:

"François Yves Le Gal" wrote in message
.. .
On Thu, 16 Mar 2006 11:08:54 -0600, "PanHandler"
wrote:

Additionally, how do I determine the volume of the drivers
themselves?

Simple geometry. Simplify the shape, consider the driver a truncated cone
and calculate it's volume.

My understanding is that this spec must be added to the
enclosure volume recommended by the driver manufacturer.

Not needed in this context : if you go for a set volume, it'll be quite
approximative when compared to an optimized alignment.

What speakers are you planning to use ?

They're Logic CLX 12's, rated at 4ohms, 600W max, 300W RMS. The amp is a
Logic 4 channel PLX 4800, 350W/ch 2 ohms, 175W/ch 4 ohms. bridgeable, H/L
variable bandpass, usual bells and whistles. Went with Logic based on good
past performance of older equipment.
I appreciate your attention!
Joe Arnold


http://www.logicsoundlab.com/CLX12.html Drivers
No URL for Amp - it was just released, not on website yet.
\

Very small voice coil for that much power!! But the efficiency rating is high.
1.5 inches.

greg

"GregS" wrote in message
...

Very small voice coil for that much power!! But the efficiency rating is
high.
1.5 inches.

Pros and cons regarding series or parallel wiring of them?
Joe

In article , "PanHandler" wrote:

"GregS" wrote in message
...

Very small voice coil for that much power!! But the efficiency rating is
high.
1.5 inches.

Pros and cons regarding series or parallel wiring of them?
Joe

Its mostly just getting them to match with the amplifier.
You mostly series them for bridging applications.

Adding stuffing into a sealed box makes magic by enlarging the effective
box volume. When space is premium, the box can be made smaller.
Its easy to gain 10%. I have got near the theoretical 40% under the right
conditions using the right stuff.

greg

PanHandler wrote:

"GregS" wrote in message
...


Very small voice coil for that much power!! But the efficiency rating is
high.
1.5 inches.


Pros and cons regarding series or parallel wiring of them?

Parallel: result is 2 ohm load, which may be a problem for some amps.

Series: result is 8 ohm load, which most any amp will drive. But amps
that are capable of driving a 2 ohm load will *usualy* be able to put
more power into 2 ohms than 8 ohms.

So, check your amp. Will it be happy driving a 2 ohm load? (and
remember that this is "nominal" load, it may be lower at some
frequencies depending on the speaker and the enclosure.) What's it's
rated output at 2 vs 8 ohms. Is this reduction in power important?

If you're planning on hooking it up to different amps, the series wiring
will make this more trouble free.

//Walt

"GregS" wrote in message
...

Adding stuffing into a sealed box makes magic by enlarging the effective
box volume. When space is premium, the box can be made smaller.
Its easy to gain 10%. I have got near the theoretical 40% under the right
conditions using the right stuff.

I have a bunch of polyfill at my disposal to experiment with. This whole
project is primarily for parties, indoors and out. The equipment rack
(cabinet) and sub/satellites will be on dolly wheels, with quick-connect
speaker cable. The amplifier and head unit will be powered by a 35 amp
Pyramid supply. I have a 'test bench' setup in my shop to check everything
out, at the moment mostly using alligator clips. Aside from CD's, I have
over 32,000 mp3's on an external HDD, running through my laptop to feed the
head unit aux in. Next will be to investigate something better than the
laptop's integrated sound chip. I'm considering a Creative Extigy external
USB unit.

BTW - so far the Pyramid has peaked at 15 amps, but things got too loud for
comfort.

"Walt" wrote in message
...
PanHandler wrote:

"GregS" wrote in message
...


Very small voice coil for that much power!! But the efficiency rating is
high.
1.5 inches.


Pros and cons regarding series or parallel wiring of them?

Parallel: result is 2 ohm load, which may be a problem for some amps.

Series: result is 8 ohm load, which most any amp will drive. But amps
that are capable of driving a 2 ohm load will *usualy* be able to put more
power into 2 ohms than 8 ohms.

So, check your amp. Will it be happy driving a 2 ohm load? (and remember
that this is "nominal" load, it may be lower at some frequencies depending
on the speaker and the enclosure.) What's it's rated output at 2 vs 8
ohms. Is this reduction in power important?

If you're planning on hooking it up to different amps, the series wiring
will make this more trouble free.

The amps is stable to 2 ohms. It's rated at 350 Watts/channel into 2 ohms,
175 at 4 ohms. It's a 4 channel unit and is bridgeable.

"François Yves Le Gal" wrote in message
...
On Thu, 16 Mar 2006 13:11:57 -0600, "PanHandler"
wrote:

They're Logic CLX 12's

I don't have this driver in my database and could only find sparse and
unconfirmed data:

Fs: 25hz
Qts. 0.3
Qms: 3.27
Qes: 0.34
Vas: 6.594 ft3 / 186.72 l

For a single driver, anything around 0,8 ft3 / 22 l will be fine for a
closed box (those values yield a B2 alignment).

So the recommended 1 ft3 is OK : you'll have a lower Qts at 0,644.

Two drivers will of course require around 2 ft3. As the drivers are 4-ohm,
you should be careful if you wire them in parallel : the resulting
impedance
will be 2 ohms and could drop below this already low value, something most
amps don't like at all.

600W max, 300W RMS.

I very much doubt that a USD 45.00 driver fitted with a 1,5" voice coil
can
handle this level of power...
:-)

Me too! That's why it won't be bridged.
Joe

PanHandler wrote:

"Walt" wrote in message
...

PanHandler wrote:


"GregS" wrote in message
.. .



Very small voice coil for that much power!! But the efficiency rating is
high.
1.5 inches.


Pros and cons regarding series or parallel wiring of them?

Parallel: result is 2 ohm load, which may be a problem for some amps.

Series: result is 8 ohm load, which most any amp will drive. But amps
that are capable of driving a 2 ohm load will *usualy* be able to put more
power into 2 ohms than 8 ohms.

So, check your amp. Will it be happy driving a 2 ohm load? (and remember
that this is "nominal" load, it may be lower at some frequencies depending
on the speaker and the enclosure.) What's it's rated output at 2 vs 8
ohms. Is this reduction in power important?

If you're planning on hooking it up to different amps, the series wiring
will make this more trouble free.

The amps is stable to 2 ohms. It's rated at 350 Watts/channel into 2 ohms,
175 at 4 ohms. It's a 4 channel unit and is bridgeable.

Do you have all four channels available for the bass bin you're
building? Then you might want to wire each speaker separately and
bridge each one across two amp channels.

Heck, now that I've thought about it for more than a minute, I'd
probably just wire each speaker up to it's own jack and be done with it.
You can go parallel, or have a dedicated amp channel per driver.

//Walt

In article , "PanHandler" wrote:

"GregS" wrote in message
...

Adding stuffing into a sealed box makes magic by enlarging the effective
box volume. When space is premium, the box can be made smaller.
Its easy to gain 10%. I have got near the theoretical 40% under the right
conditions using the right stuff.

I have a bunch of polyfill at my disposal to experiment with. This whole
project is primarily for parties, indoors and out. The equipment rack
(cabinet) and sub/satellites will be on dolly wheels, with quick-connect
speaker cable. The amplifier and head unit will be powered by a 35 amp
Pyramid supply. I have a 'test bench' setup in my shop to check everything
out, at the moment mostly using alligator clips. Aside from CD's, I have
over 32,000 mp3's on an external HDD, running through my laptop to feed the
head unit aux in. Next will be to investigate something better than the
laptop's integrated sound chip. I'm considering a Creative Extigy external
USB unit.

BTW - so far the Pyramid has peaked at 15 amps, but things got too loud for
comfort.

It may be hard to measure actual peak. For portable use extra stuffing is not necessary
and for all practical purposes, somewhat hinders performance when your really
stuffing hard. Hard stuffing is when your hand has great difficulty pushing through the fibers.
Stick with your polyfill, though fiberglass is the only thing to use for maximun change
in box size. If there is a vent on the rear of the driver, keep it open for air flow.

greg

"GregS" wrote in message
...
In article , "PanHandler"
wrote:

"GregS" wrote in message
...

Very small voice coil for that much power!! But the efficiency rating is
high.
1.5 inches.

Pros and cons regarding series or parallel wiring of them?
Joe

Its mostly just getting them to match with the amplifier.
You mostly series them for bridging applications.

Adding stuffing into a sealed box makes magic by enlarging the effective
box volume. When space is premium, the box can be made smaller.
Its easy to gain 10%. I have got near the theoretical 40% under the right
conditions using the right stuff.

greg

How does adding stuffing increase the box volume?

In article , "PanHandler" wrote:

"GregS" wrote in message
...

Adding stuffing into a sealed box makes magic by enlarging the effective
box volume. When space is premium, the box can be made smaller.
Its easy to gain 10%. I have got near the theoretical 40% under the right
conditions using the right stuff.

I have a bunch of polyfill at my disposal to experiment with. This whole
project is primarily for parties, indoors and out. The equipment rack
(cabinet) and sub/satellites will be on dolly wheels, with quick-connect
speaker cable. The amplifier and head unit will be powered by a 35 amp
Pyramid supply. I have a 'test bench' setup in my shop to check everything
out, at the moment mostly using alligator clips. Aside from CD's, I have
over 32,000 mp3's on an external HDD, running through my laptop to feed the
head unit aux in. Next will be to investigate something better than the
laptop's integrated sound chip. I'm considering a Creative Extigy external
USB unit.

BTW - so far the Pyramid has peaked at 15 amps, but things got too loud for
comfort.


15 amps times 13 volts is over 195 watts into the amplifier. There is less power
out. What it means, if the amplifier was peaking 1400 watts, you would need well over
107 amps to power it to full. Don't get excited though, things will work out
OK. Its this problem though, which makes using car audio amplifiers
unpractical for saving money.

greg

In article , "Doug Kanter" wrote:

"GregS" wrote in message
...
In article , "PanHandler"
wrote:

"GregS" wrote in message
.. .

Very small voice coil for that much power!! But the efficiency rating is
high.
1.5 inches.

Pros and cons regarding series or parallel wiring of them?
Joe

Its mostly just getting them to match with the amplifier.
You mostly series them for bridging applications.

Adding stuffing into a sealed box makes magic by enlarging the effective
box volume. When space is premium, the box can be made smaller.
Its easy to gain 10%. I have got near the theoretical 40% under the right
conditions using the right stuff.

greg

How does adding stuffing increase the box volume?

There is some mix as to theory, but the most accepted one is
thermal conversion. I'll let others explain it in detail, but when air
expands and contracts the intantanious temperature changes, and
the fibers act as a heat sink, lowering the temperatur change, in others
words, acting as though there is less pressure being created, like in a bigger
box.

greg

"GregS" wrote in message
...
In article , "Doug Kanter"
wrote:

"GregS" wrote in message
...
In article , "PanHandler"
wrote:

"GregS" wrote in message
. ..

Very small voice coil for that much power!! But the efficiency rating
is
high.
1.5 inches.

Pros and cons regarding series or parallel wiring of them?
Joe

Its mostly just getting them to match with the amplifier.
You mostly series them for bridging applications.

Adding stuffing into a sealed box makes magic by enlarging the effective
box volume. When space is premium, the box can be made smaller.
Its easy to gain 10%. I have got near the theoretical 40% under the
right
conditions using the right stuff.

greg

How does adding stuffing increase the box volume?

There is some mix as to theory, but the most accepted one is
thermal conversion. I'll let others explain it in detail, but when air
expands and contracts the intantanious temperature changes, and
the fibers act as a heat sink, lowering the temperatur change, in others
words, acting as though there is less pressure being created, like in a
bigger
box.

greg

Weird. I have a rather nice speaker design book at home which never
mentioned this. I'll look again. I'm aware of how ducting & porting make
magic, though.

Doug Kanter wrote:
"GregS" wrote in message
Adding stuffing into a sealed box makes magic by enlarging the effective
box volume. When space is premium, the box can be made smaller.
Its easy to gain 10%. I have got near the theoretical 40% under the right
conditions using the right stuff.

How does adding stuffing increase the box volume?

If the system is completely lossless, in other words, the energy
you put into the box by compressing it, or remove from it by exanding
it doesn't go anywhere except into the air in the box, (this is called
"adiabatic", or constant energy), then that energy changes the
temperature of the air in the box accordingly. If, for example, you
compress the air in then box, it raises the temperature. The rise
in temperature means there is more force due to kinetic impacts
on the diaphragm.

However, contrive some way of removing that excess energy, and now
there is less force due to the somewhat lower temperature (no longer
adiabatic, but "isothermal," same temperature).

Now, the "size" of the box is significant in this respect in that the
volume of trapped air determines basically how much force it
takes to move the diaphragm a specific distance, i.e., the "spring
constant" of the box. A smaller box is compressed more quickly
by any given movement of the diaphragm, and thus requires more
force for a given diaphragm excursion: it's spring constant is
higher (or, conversely, it's compliance is lower). A larger box
is compressed less for the same movement and requires less
force for that movement: it's spring constant is lower (or its
compliance is higher.

By removing some of the thermal ebergy through the use of a fibrous
tangle (i.e., "stuffing"), you end up having less force pushing back
on the cone, and the box, therefore appears larger.

Or, succinctly, the compression of a given volume of air is different
depending upon whether the compression is adiabatic or isothermal.
And the differences is determined by the ratio of the specific heat
due to adiabatic vs isothermal expansions, and, for diatomic gases
(of which air is an excellent example, being composed primarily
of a mixture of N2 and O2 with trace amounts of C02 and H20, which
behave very nearly like diatomic gases), the ratio of the specific
heat due to adiabatic to the specific heat due to isothermal
is about 1.4.

So, the VERY best you could achieve, by absorbing ALL the
change in temperature on compressions (and releasing
ALL of it again on expansion) fis an increase in apparent box
size of 1.4 times the physical box size.

This will be on Monday's quiz.

wrote in message
oups.com...

Doug Kanter wrote:
"GregS" wrote in message
Adding stuffing into a sealed box makes magic by enlarging the
effective
box volume. When space is premium, the box can be made smaller.
Its easy to gain 10%. I have got near the theoretical 40% under the
right
conditions using the right stuff.

How does adding stuffing increase the box volume?

If the system is completely lossless, in other words, the energy
you put into the box by compressing it, or remove from it by exanding
it doesn't go anywhere except into the air in the box, (this is called
"adiabatic", or constant energy), then that energy changes the
temperature of the air in the box accordingly. If, for example, you
compress the air in then box, it raises the temperature. The rise
in temperature means there is more force due to kinetic impacts
on the diaphragm.

However, contrive some way of removing that excess energy, and now
there is less force due to the somewhat lower temperature (no longer
adiabatic, but "isothermal," same temperature).

Now, the "size" of the box is significant in this respect in that the
volume of trapped air determines basically how much force it
takes to move the diaphragm a specific distance, i.e., the "spring
constant" of the box. A smaller box is compressed more quickly
by any given movement of the diaphragm, and thus requires more
force for a given diaphragm excursion: it's spring constant is
higher (or, conversely, it's compliance is lower). A larger box
is compressed less for the same movement and requires less
force for that movement: it's spring constant is lower (or its
compliance is higher.

By removing some of the thermal ebergy through the use of a fibrous
tangle (i.e., "stuffing"), you end up having less force pushing back
on the cone, and the box, therefore appears larger.

Or, succinctly, the compression of a given volume of air is different
depending upon whether the compression is adiabatic or isothermal.
And the differences is determined by the ratio of the specific heat
due to adiabatic vs isothermal expansions, and, for diatomic gases
(of which air is an excellent example, being composed primarily
of a mixture of N2 and O2 with trace amounts of C02 and H20, which
behave very nearly like diatomic gases), the ratio of the specific
heat due to adiabatic to the specific heat due to isothermal
is about 1.4.

So, the VERY best you could achieve, by absorbing ALL the
change in temperature on compressions (and releasing
ALL of it again on expansion) fis an increase in apparent box
size of 1.4 times the physical box size.

This will be on Monday's quiz.


The quiz will be trying this idea on a bass guitar cabinet with 15" JBL
speaker, the sound of which I've never been entirely pleased with. :-)

Doug Kanter wrote:
Weird. I have a rather nice speaker design book at home which never
mentioned this. I'll look again. I'm aware of how ducting & porting make
magic, though.

Pop quiz: how?

In article , "Doug Kanter" wrote:

wrote in message
roups.com...

Doug Kanter wrote:
"GregS" wrote in message
Adding stuffing into a sealed box makes magic by enlarging the
effective



is about 1.4.

So, the VERY best you could achieve, by absorbing ALL the
change in temperature on compressions (and releasing
ALL of it again on expansion) fis an increase in apparent box
size of 1.4 times the physical box size.

This will be on Monday's quiz.


The quiz will be trying this idea on a bass guitar cabinet with 15" JBL
speaker, the sound of which I've never been entirely pleased with. :-)

A bass guitar cab is more likely to be a vented system. While
there is action of fibers in an ported cab, it still has an effect. A
closed box sounds like a good idea for performance, but the
specs of the woofer usually determine box type.

greg

wrote in message
ps.com...

Doug Kanter wrote:
Weird. I have a rather nice speaker design book at home which never
mentioned this. I'll look again. I'm aware of how ducting & porting make
magic, though.

Pop quiz: how?


Why do you ask?

Doug Kanter wrote:
wrote in message
ps.com...

Doug Kanter wrote:
Weird. I have a rather nice speaker design book at home which never
mentioned this. I'll look again. I'm aware of how ducting & porting make
magic, though.

Pop quiz: how?

Why do you ask?

Because, to be frank, most people who think they know how
vented systems work have it wrong. This is not to say that
you're one of them, rather, I'm merely asking the question.

wrote in message
ups.com...

Doug Kanter wrote:
wrote in message
ps.com...

Doug Kanter wrote:
Weird. I have a rather nice speaker design book at home which never
mentioned this. I'll look again. I'm aware of how ducting & porting
make
magic, though.

Pop quiz: how?

Why do you ask?

Because, to be frank, most people who think they know how
vented systems work have it wrong. This is not to say that
you're one of them, rather, I'm merely asking the question.


OK. I was just wondering. My information came from a great book: "Hi-Fi
Loudspeakers and Enclosures", by Abraham B. Cohen.
ISBN# 0-8104-0721-3
Publisher: Hayden Book Company, Rochelle Park NJ

Doug Kanter wrote:
wrote in message
Because, to be frank, most people who think they know how
vented systems work have it wrong. This is not to say that
you're one of them, rather, I'm merely asking the question.

OK. I was just wondering. My information came from a great book: "Hi-Fi
Loudspeakers and Enclosures", by Abraham B. Cohen.
ISBN# 0-8104-0721-3
Publisher: Hayden Book Company, Rochelle Park NJ

Cohen is most certainly not the best informed of the myriad sources
out there when I lasted visited his work a few years ago. I don't have
his book in front of me, so, if you'd like, summarize what you think
he said and let's see how close he got.

In article , (GregS) wrote:
In article , "PanHandler"
wrote:

"GregS" wrote in message
...

Adding stuffing into a sealed box makes magic by enlarging the effective
box volume. When space is premium, the box can be made smaller.
Its easy to gain 10%. I have got near the theoretical 40% under the right
conditions using the right stuff.

I have a bunch of polyfill at my disposal to experiment with. This whole
project is primarily for parties, indoors and out. The equipment rack
(cabinet) and sub/satellites will be on dolly wheels, with quick-connect
speaker cable. The amplifier and head unit will be powered by a 35 amp
Pyramid supply. I have a 'test bench' setup in my shop to check everything
out, at the moment mostly using alligator clips. Aside from CD's, I have
over 32,000 mp3's on an external HDD, running through my laptop to feed the
head unit aux in. Next will be to investigate something better than the
laptop's integrated sound chip. I'm considering a Creative Extigy external
USB unit.

BTW - so far the Pyramid has peaked at 15 amps, but things got too loud for
comfort.


15 amps times 13 volts is over 195 watts into the amplifier. There is less
power
out. What it means, if the amplifier was peaking 1400 watts, you would need
well over
107 amps to power it to full. Don't get excited though, things will work out
OK. Its this problem though, which makes using car audio amplifiers
unpractical for saving money.

I was thinking this over yesterday. I guess its sort of strange that no car amps
I'm aware of, are adaptable to home use. All the amplifier
needs is a different switched power supply. Instead of going
up in volts, you go down in volts. The cost would be the same.
How many would they sell?? Seems like there would be a market
for them.

greg

I've hear of a few different types of fibers being used to stuff boxes; like
real wool, polyester and glass. My first thought is that none of these
materials are very thermally conductive ~ as a matter of fact, they are
quite the opposite. Has there ever been any development of fibers that are
much more conductive and therefore a better heat sink? It would seem to me
that a fine metal wool that wouldn't rust into dust would be better for this
purpose.

James. )

In article , "James Lehman" wrote:
I've hear of a few different types of fibers being used to stuff boxes; like
real wool, polyester and glass. My first thought is that none of these
materials are very thermally conductive ~ as a matter of fact, they are
quite the opposite. Has there ever been any development of fibers that are
much more conductive and therefore a better heat sink? It would seem to me
that a fine metal wool that wouldn't rust into dust would be better for this
purpose.

James. )

I don't know of any myself. I do know, regular type foam is good to being the best
at this. Trouble is, its too dense, and need to have holes in it. or some kind of matrix.
I wanted to see the difference between polyfills myself, and to see the difference
between wool, polyester (Dacron), foam, cotton, so I did a test.

http://www.pitt.edu/~szekeres/relay.htm

In article , "James Lehman" wrote:
I've hear of a few different types of fibers being used to stuff boxes; like
real wool, polyester and glass. My first thought is that none of these
materials are very thermally conductive ~ as a matter of fact, they are
quite the opposite. Has there ever been any development of fibers that are
much more conductive and therefore a better heat sink? It would seem to me
that a fine metal wool that wouldn't rust into dust would be better for this
purpose.

James. )

There were some speakers that use heavier than air gases, which
seemed to work OK for increasing box size, until the gas escaped.

greg

James Lehman wrote:
I've hear of a few different types of fibers being used to stuff boxes; like
real wool, polyester and glass. My first thought is that none of these
materials are very thermally conductive ~ as a matter of fact, they are
quite the opposite. Has there ever been any development of fibers that are
much more conductive and therefore a better heat sink? It would seem to me
that a fine metal wool that wouldn't rust into dust would be better for this
purpose.

Thernal conductivity has little if anything to do with the process..
The air
is flowing through the fibers, all the fiber gets air around it,
conductivity
just isn't inportant. On the other hand, factros such as the
material's
speicific heat, the diameter of the fiber, it's surface roughness, the
fiber density and such. All of these, for one reason or another suggest
that manmade fibers aren't quite as effective as natrual fibers, and
empirical data concurs somewhat.

James Lehman wrote:
I've hear of a few different types of fibers being used to stuff boxes; like
real wool, polyester and glass. My first thought is that none of these
materials are very thermally conductive ~ as a matter of fact, they are
quite the opposite. Has there ever been any development of fibers that are
much more conductive and therefore a better heat sink? It would seem to me
that a fine metal wool that wouldn't rust into dust would be better for this
purpose.

One other point on this: the thermal conducivity is pretty irrelevant,
as
I mentioned. One of the reasons is that you are not at all concerned
about conducting the heat somewhere else: there's fibers all over the
place. Fiberglass wool, for example, as a bulk material, has very good
thermal conducivity. As a fiberous tangle, it''s a MUCH different
issue.
The idea to using fiberous tangles as a thermal insulator is that the
tangle dramatically reduces the AIR'S ability to transport heat by
primarily
convection (air itself is not so good at conducting heat by
conduction).

The reason, for our purposes, that conduction is irrelevant, is that
the
fibers are everywhere, and it can be show that they pretty much change
temperature simultaneously, for all intents and purposes. Since two
parts of teh fiber are at the same tempoerature, heat conduction isn't
going to happen anyway, so heat conductivity is of no consequence.
The only place the heat has to conduct to and from is the fivber itself
to and from the air around it.

Fibers with coarse surfaces (like lamb's wool) generate more
turbulance as air passes by than fibers with smooth surfaces
(like dacron, polyester or glass), thus convert more of the kinetic
energy of the fluid motion into heat that raises the temeprature of
the fiber. Fibers such as steel wool tend to have very smooth
surfaces and thus are less effective than rougher materials.
Plus the fact they tend not to stay in place in the presence of
large magnets :-).

In article .com, wrote:

James Lehman wrote:
I've hear of a few different types of fibers being used to stuff boxes; like
real wool, polyester and glass. My first thought is that none of these
materials are very thermally conductive ~ as a matter of fact, they are
quite the opposite. Has there ever been any development of fibers that are
much more conductive and therefore a better heat sink? It would seem to me
that a fine metal wool that wouldn't rust into dust would be better for this
purpose.

One other point on this: the thermal conducivity is pretty irrelevant,
as
I mentioned. One of the reasons is that you are not at all concerned
about conducting the heat somewhere else: there's fibers all over the
place. Fiberglass wool, for example, as a bulk material, has very good
thermal conducivity. As a fiberous tangle, it''s a MUCH different
issue.
The idea to using fiberous tangles as a thermal insulator is that the
tangle dramatically reduces the AIR'S ability to transport heat by
primarily
convection (air itself is not so good at conducting heat by
conduction).

This just reminded me of when I last insulated a house. I learned that fiberglass
as used in for insulation purposes is really not considered a good
barrier against air currents, or at least newspaper fibers, as used in blown in insulation,
have a better barrier against air currents. When there is an extreme temperature
differential, fiberglass performance decreases, where the newspaper fibers outperform
fiberglass. So I'm wondering how this stuff stacks up. Perhaps air currents,
or at least with any distance, are not really important. Pressure fronts through the enclosure
will force their way through the fibers anyway.

greg

"GregS" wrote in message
...

I was thinking this over yesterday. I guess its sort of strange that no
car amps
I'm aware of, are adaptable to home use. All the amplifier
needs is a different switched power supply. Instead of going
up in volts, you go down in volts. The cost would be the same.
How many would they sell?? Seems like there would be a market
for them.

The 1400 Watt 4 Channel amp, two 12" woofers, two 6" mids, two 1" dome
tweeters, Pyramid power supply, mp3 capable head unit w/remote, proper
wiring and connectors, shrink tubing, etc. set me back a little over $500.
All that's left to buy is MDF board, protective metal cabinet corners and
dolly wheels for portability and I'm ready to party. Not a bad deal in my
opinion!
Joe

In article , "PanHandler" wrote:

"GregS" wrote in message
...

I was thinking this over yesterday. I guess its sort of strange that no
car amps
I'm aware of, are adaptable to home use. All the amplifier
needs is a different switched power supply. Instead of going
up in volts, you go down in volts. The cost would be the same.
How many would they sell?? Seems like there would be a market
for them.

The 1400 Watt 4 Channel amp, two 12" woofers, two 6" mids, two 1" dome
tweeters, Pyramid power supply, mp3 capable head unit w/remote, proper
wiring and connectors, shrink tubing, etc. set me back a little over $500.
All that's left to buy is MDF board, protective metal cabinet corners and
dolly wheels for portability and I'm ready to party. Not a bad deal in my
opinion!
Joe

Thats very good. I'm just wondering. I myself would use plywood
for less transport weight, but if I was on a budget, particle board for sure.
And you can always use a battery in a pinch!

greg

"GregS" wrote in message
...

This just reminded me of when I last insulated a house. I learned that
fiberglass
as used in for insulation purposes is really not considered a good
barrier against air currents, or at least newspaper fibers, as used in
blown in insulation,
have a better barrier against air currents. When there is an extreme
temperature
differential, fiberglass performance decreases, where the newspaper fibers
outperform
fiberglass. So I'm wondering how this stuff stacks up. Perhaps air
currents,
or at least with any distance, are not really important. Pressure fronts
through the enclosure
will force their way through the fibers anyway.

This is degenerating into something like a Monster Wire discussion! :-)
Joe

"GregS" wrote in message
...

Thats very good. I'm just wondering. I myself would use plywood
for less transport weight, but if I was on a budget, particle board for
sure.
And you can always use a battery in a pinch!

I do have a full sheet of 3/4 ply, but it's C/D grade - too rough, although
I'll probably cover everything with carpet after the dust settles. Cosmetics
aside, I wonder what a commercial home system with similar specs would cost.