I've got a Raspberry Pi 3 and the official Raspberry Pi Touchscreen that
I'm working on building a case for. I've come across a design decision I'd
like a little input on.

I have an amplifier and speaker arrangement to give me basic sound. I'm
using 2 small speakers, about 1" by 2". The speakers are in their own
plastic enclosure with a provision to mount the speaker using a
sufficiently small screw, probably 2-56 maybe 1-72. FWIW, the case will
probably be pine.

It makes sense to make some form of grill or hole in the wood to make sure
the sound can pass unobstructed. I could possibly cut 1/8" wide slots with
an endmill or drill a series of holes. Which would be better, or does it
matter?

Also, I'd like to keep little bits of debris from sticking to the speaker
cone. Would a piece of cotton cloth or something similar work as "speaker
fabric" without affecting the sound too much?

Thanks,

Puckdropper

"Puckdropper" wrote in message
b.com...

It makes sense to make some form of grill or hole in the wood to make sure
the sound can pass unobstructed. I could possibly cut 1/8" wide slots with
an endmill or drill a series of holes. Which would be better, or does it
matter?

Also, I'd like to keep little bits of debris from sticking to the speaker
cone. Would a piece of cotton cloth or something similar work as "speaker
fabric" without affecting the sound too much?

Puckdropper

Simplest might be to just bore a hole a little smaller than the diameter of
the speaker cone, and glue a very light piece of cloth across the opening
between the wood and the speaker. Shouldn't have much of an effect on the
sound, if any. Maybe your wife or girlfriend has a pair of black nylons
she's about ready to throw away ;-)

Tom

On 3/28/2016 5:46 PM, tdacon wrote:


"Puckdropper" wrote in message
b.com...

It makes sense to make some form of grill or hole in the wood to make
sure
the sound can pass unobstructed. I could possibly cut 1/8" wide slots
with
an endmill or drill a series of holes. Which would be better, or does it
matter?

Also, I'd like to keep little bits of debris from sticking to the speaker
cone. Would a piece of cotton cloth or something similar work as
"speaker
fabric" without affecting the sound too much?

Puckdropper

Simplest might be to just bore a hole a little smaller than the diameter
of the speaker cone, and glue a very light piece of cloth across the
opening between the wood and the speaker. Shouldn't have much of an
effect on the sound, if any. Maybe your wife or girlfriend has a pair of
black nylons she's about ready to throw away ;-)

For that application (all things considered) he could probably glue a
piece of cheese cloth over the opening and never know the difference
other than a VERY slight degradation in volume. In short, most anything
would work. Nylons would work but I'd have some concerns about longevity.

On Mon, 28 Mar 2016 18:32:45 -0500, Unquestionably Confused
wrote:

On 3/28/2016 5:46 PM, tdacon wrote:


"Puckdropper" wrote in message
b.com...

It makes sense to make some form of grill or hole in the wood to make
sure
the sound can pass unobstructed. I could possibly cut 1/8" wide slots
with
an endmill or drill a series of holes. Which would be better, or does it
matter?

Also, I'd like to keep little bits of debris from sticking to the speaker
cone. Would a piece of cotton cloth or something similar work as
"speaker
fabric" without affecting the sound too much?

Puckdropper

Simplest might be to just bore a hole a little smaller than the diameter
of the speaker cone, and glue a very light piece of cloth across the
opening between the wood and the speaker. Shouldn't have much of an
effect on the sound, if any. Maybe your wife or girlfriend has a pair of
black nylons she's about ready to throw away ;-)

For that application (all things considered) he could probably glue a
piece of cheese cloth over the opening and never know the difference
other than a VERY slight degradation in volume. In short, most anything
would work. Nylons would work but I'd have some concerns about longevity.


Cheesecloth is too pores (SP) too soft/stretchy. Nylon's would be
better and have a sexy sound. (g) but the best would be a stiffer
cloth.

If the speaker is going in a box the harder the wood the more it
reflects sound. Also drill a small hole for the back side of the
speaker to allow the diaphragm to fluctuate freely, you can tune the
speaker by the size of the hole.

On 3/29/2016 2:03 AM, OFWW wrote:
On Mon, 28 Mar 2016 18:32:45 -0500, Unquestionably Confused
wrote:

On 3/28/2016 5:46 PM, tdacon wrote:


"Puckdropper" wrote in message
b.com...

It makes sense to make some form of grill or hole in the wood to make
sure
the sound can pass unobstructed. I could possibly cut 1/8" wide slots
with
an endmill or drill a series of holes. Which would be better, or does it
matter?

Also, I'd like to keep little bits of debris from sticking to the speaker
cone. Would a piece of cotton cloth or something similar work as
"speaker
fabric" without affecting the sound too much?

Puckdropper

Simplest might be to just bore a hole a little smaller than the diameter
of the speaker cone, and glue a very light piece of cloth across the
opening between the wood and the speaker. Shouldn't have much of an
effect on the sound, if any. Maybe your wife or girlfriend has a pair of
black nylons she's about ready to throw away ;-)

For that application (all things considered) he could probably glue a
piece of cheese cloth over the opening and never know the difference
other than a VERY slight degradation in volume. In short, most anything
would work. Nylons would work but I'd have some concerns about longevity.


Cheesecloth is too pores (SP) too soft/stretchy. Nylon's would be
better and have a sexy sound. (g) but the best would be a stiffer
cloth.

If the speaker is going in a box the harder the wood the more it
reflects sound. Also drill a small hole for the back side of the
speaker to allow the diaphragm to fluctuate freely, you can tune the
speaker by the size of the hole.

All valid points but in this instance he refers to 1/8" slots covering
the speaker opening. I wouldn't be worried too much about the
"stretchiness" of the cloth nor, for that matter, the porosity (read:
Acoustic Transparency) of that material. Likewise, if we go away from
1/8" slots, we may find that SWMBO's used panty hose will not be
sufficiently strong to withstand repeated finger pokes after x number of
months of exposure to UV light, etc.

OFWW wrote in
:

Cheesecloth is too pores (SP) too soft/stretchy. Nylon's would be
better and have a sexy sound. (g) but the best would be a stiffer
cloth.

This sort of depends on how concerned you are with the sound
quality. A soft, porous cloth will attenuate the sound, and
affect the tone. If you want good acoustics, use a stiff cloth.
If you just want to keep debris out, use whatever's handy.

If the speaker is going in a box the harder the wood the more it
reflects sound. Also drill a small hole for the back side of the
speaker to allow the diaphragm to fluctuate freely, you can tune the
speaker by the size of the hole.

This is important - not the tuning, but having some sort of
vent on the backside of the speaker. A speaker makes sound
by pushing air forwards and back, and if there's no way for
air to move behind the speaker, it's not going to move much
air in front either. Result - not much sound. (this is
assuming the box is smallish - a big box with small speakers
has enough volume inside it won't need a vent).

Also, since you have two speakers, make sure they are phased
correctly. If you connect them out of phase, they will cancel
each other, and again you get not much sound. This is more
of a problem with big bass speakers, but even with small ones
it's worth checking the plug is right way round.

John

Unquestionably Confused wrote in
eb.com:


All valid points but in this instance he refers to 1/8" slots covering
the speaker opening. I wouldn't be worried too much about the
"stretchiness" of the cloth nor, for that matter, the porosity (read:
Acoustic Transparency) of that material. Likewise, if we go away from
1/8" slots, we may find that SWMBO's used panty hose will not be
sufficiently strong to withstand repeated finger pokes after x number
of months of exposure to UV light, etc.


I'm thinking about just gluing the fabric to the backside of the speaker
grill, which should take care of things nicely. I'm not worried about
fingers or stuff like that getting in, just the annoying little bits of
debris that these things tend to collect and can sometimes be a pain to
remove.

The speaker has its own enclosure, and the enclosure will be mounted to the
case.

Puckdropper

On 3/29/2016 10:43 AM, John McCoy wrote:
OFWW wrote in
:

Cheesecloth is too pores (SP) too soft/stretchy. Nylon's would be
better and have a sexy sound. (g) but the best would be a stiffer
cloth.

This sort of depends on how concerned you are with the sound
quality. A soft, porous cloth will attenuate the sound, and
affect the tone. If you want good acoustics, use a stiff cloth.
If you just want to keep debris out, use whatever's handy.

FWIW I have not ever witnessed this. Maybe a little if the cloth is
denser/thicker than the length of the sound waves and that is more if a
concern for higher notes where the sound is more directional. But I
used drapery material in from of my L?R and center speakers and you can
not tell if the material/door is open or closed.







If the speaker is going in a box the harder the wood the more it
reflects sound. Also drill a small hole for the back side of the
speaker to allow the diaphragm to fluctuate freely, you can tune the
speaker by the size of the hole.

This is important - not the tuning, but having some sort of
vent on the backside of the speaker. A speaker makes sound
by pushing air forwards and back, and if there's no way for
air to move behind the speaker, it's not going to move much
air in front either. Result - not much sound. (this is
assuming the box is smallish - a big box with small speakers
has enough volume inside it won't need a vent).

That is not true either. Long ago many speakers were built to be air
tight. Case in point many subwolfers use a driver speaker and a slave
speaker inside the same enclosure. The whole speaker assembly is
dependent on being air tight for the slave speaker to function and
produce sound.

And the speakers do not move enough to be hampered by air that easily
compressed or expands from the movement of the speaker. I have a
totally enclosed 12" subwolfer with no issues.



Also, since you have two speakers, make sure they are phased
correctly. If you connect them out of phase, they will cancel
each other, and again you get not much sound. This is more
of a problem with big bass speakers, but even with small ones
it's worth checking the plug is right way round.

John



Swingman would be the one to consult here, he has built, owned and
operated recording studios. He told me that the material would not
matter when covering my entertainment center doors with drapery
material, and you cannot tell the difference. My only concern was that
the weave was not so dense that IR light would not pass through. I
simply held the material up to a light to see if the light penetrated.

Leon lcb11211@swbelldotnet wrote in news:d-ednSYZkf_9JmfLnZ2dnUU7-
:

*snip & trim*


That is not true either. Long ago many speakers were built to be air
tight. Case in point many subwolfers use a driver speaker and a slave
speaker inside the same enclosure. The whole speaker assembly is
dependent on being air tight for the slave speaker to function and
produce sound.

And the speakers do not move enough to be hampered by air that easily
compressed or expands from the movement of the speaker. I have a
totally enclosed 12" subwolfer with no issues.

What would the slave speaker tend to look like? Basically like a speaker
without a magnet? I picked up a speaker from Walmart that had one real
speaker and one that kinda looked like a decoy or fake speaker.

*snip & trim*

Puckdropper

Puckdropper puckdropper(at)yahoo(dot)com wrote in
b.com:

Leon lcb11211@swbelldotnet wrote in news:d-ednSYZkf_9JmfLnZ2dnUU7-
:

That is not true either. Long ago many speakers were built to be air
tight. Case in point many subwolfers use a driver speaker and a
slave speaker inside the same enclosure. The whole speaker assembly
is dependent on being air tight for the slave speaker to function and
produce sound.

What would the slave speaker tend to look like? Basically like a
speaker without a magnet? I picked up a speaker from Walmart that had
one real speaker and one that kinda looked like a decoy or fake
speaker.

Slave speaker is a special case - in that case the slave is
moving outward when the driven speaker is moving inward, and
vice-versa, so the volume of air inside the enclosure doesn't
change.

With two driven speakers, if the enclosure is airtight you're
compressing (or decompressing) the air in the enclosure, which
is generating a force opposing the way the speaker is being
driven. How much force depends on how big the speaker is, and
how much volume is in the enclosure. If your enclosure is
small, it can have an appreciable effect.

John

On 3/29/2016 1:05 PM, Puckdropper wrote:
Leon lcb11211@swbelldotnet wrote in news:d-ednSYZkf_9JmfLnZ2dnUU7-
:

*snip & trim*


That is not true either. Long ago many speakers were built to be air
tight. Case in point many subwolfers use a driver speaker and a slave
speaker inside the same enclosure. The whole speaker assembly is
dependent on being air tight for the slave speaker to function and
produce sound.

And the speakers do not move enough to be hampered by air that easily
compressed or expands from the movement of the speaker. I have a
totally enclosed 12" subwolfer with no issues.

What would the slave speaker tend to look like? Basically like a speaker
without a magnet? I picked up a speaker from Walmart that had one real
speaker and one that kinda looked like a decoy or fake speaker.

That would be it! If you dare thump the driven speaker the slave should
move a bit.






*snip & trim*

Puckdropper

On 3/29/2016 1:20 PM, John McCoy wrote:
Puckdropper puckdropper(at)yahoo(dot)com wrote in
b.com:

Leon lcb11211@swbelldotnet wrote in news:d-ednSYZkf_9JmfLnZ2dnUU7-
:

That is not true either. Long ago many speakers were built to be air
tight. Case in point many subwolfers use a driver speaker and a
slave speaker inside the same enclosure. The whole speaker assembly
is dependent on being air tight for the slave speaker to function and
produce sound.

What would the slave speaker tend to look like? Basically like a
speaker without a magnet? I picked up a speaker from Walmart that had
one real speaker and one that kinda looked like a decoy or fake
speaker.

Slave speaker is a special case - in that case the slave is
moving outward when the driven speaker is moving inward, and
vice-versa, so the volume of air inside the enclosure doesn't
change.


The air volume does not change in a sealed speaker either. The pressure
does change but not the volume.





With two driven speakers, if the enclosure is airtight you're
compressing (or decompressing) the air in the enclosure, which
is generating a force opposing the way the speaker is being
driven.

Not so if the speakers are air tight in their own compartments inside
the speaker housing, which apparently is how my center speaker with 2,
5" speakers is set up.


How much force depends on how big the speaker is, and
how much volume is in the enclosure. If your enclosure is
small, it can have an appreciable effect.

John

On Tue, 29 Mar 2016 15:43:40 -0000 (UTC), John McCoy
wrote:

OFWW wrote in
:

Cheesecloth is too pores (SP) too soft/stretchy. Nylon's would be
better and have a sexy sound. (g) but the best would be a stiffer
cloth.

This sort of depends on how concerned you are with the sound
quality. A soft, porous cloth will attenuate the sound, and
affect the tone. If you want good acoustics, use a stiff cloth.
If you just want to keep debris out, use whatever's handy.

If the speaker is going in a box the harder the wood the more it
reflects sound. Also drill a small hole for the back side of the
speaker to allow the diaphragm to fluctuate freely, you can tune the
speaker by the size of the hole.

This is important - not the tuning, but having some sort of
vent on the backside of the speaker. A speaker makes sound
by pushing air forwards and back, and if there's no way for
air to move behind the speaker, it's not going to move much
air in front either. Result - not much sound. (this is
assuming the box is smallish - a big box with small speakers
has enough volume inside it won't need a vent).

That depends on the speaker. "Acoustic suspension" speakers aren't
ported. They rely on the back pressure to return the speaker to its
midpoint.

Also, since you have two speakers, make sure they are phased
correctly. If you connect them out of phase, they will cancel
each other, and again you get not much sound. This is more
of a problem with big bass speakers, but even with small ones
it's worth checking the plug is right way round.

On Tue, 29 Mar 2016 14:12:26 -0500, Leon lcb11211@swbelldotnet
wrote:

On 3/29/2016 1:20 PM, John McCoy wrote:
Puckdropper puckdropper(at)yahoo(dot)com wrote in
b.com:

Leon lcb11211@swbelldotnet wrote in news:d-ednSYZkf_9JmfLnZ2dnUU7-
:

That is not true either. Long ago many speakers were built to be air
tight. Case in point many subwolfers use a driver speaker and a
slave speaker inside the same enclosure. The whole speaker assembly
is dependent on being air tight for the slave speaker to function and
produce sound.

What would the slave speaker tend to look like? Basically like a
speaker without a magnet? I picked up a speaker from Walmart that had
one real speaker and one that kinda looked like a decoy or fake
speaker.

Slave speaker is a special case - in that case the slave is
moving outward when the driven speaker is moving inward, and
vice-versa, so the volume of air inside the enclosure doesn't
change.


The air volume does not change in a sealed speaker either. The pressure
does change but not the volume.

The volume of air obviously changes as the volume increases. ;-) The
quantity of air is constant, the pressure is changing, so the volume
must change (inversely). Remember, the speaker cone is moving.



With two driven speakers, if the enclosure is airtight you're
compressing (or decompressing) the air in the enclosure, which
is generating a force opposing the way the speaker is being
driven.

Not so if the speakers are air tight in their own compartments inside
the speaker housing, which apparently is how my center speaker with 2,
5" speakers is set up.


How much force depends on how big the speaker is, and
how much volume is in the enclosure. If your enclosure is
small, it can have an appreciable effect.

John

On Tue, 29 Mar 2016 07:32:52 -0500, Unquestionably Confused
wrote:

On 3/29/2016 2:03 AM, OFWW wrote:
On Mon, 28 Mar 2016 18:32:45 -0500, Unquestionably Confused
wrote:

On 3/28/2016 5:46 PM, tdacon wrote:


"Puckdropper" wrote in message
b.com...

It makes sense to make some form of grill or hole in the wood to make
sure
the sound can pass unobstructed. I could possibly cut 1/8" wide slots
with
an endmill or drill a series of holes. Which would be better, or does it
matter?

Also, I'd like to keep little bits of debris from sticking to the speaker
cone. Would a piece of cotton cloth or something similar work as
"speaker
fabric" without affecting the sound too much?

Puckdropper

Simplest might be to just bore a hole a little smaller than the diameter
of the speaker cone, and glue a very light piece of cloth across the
opening between the wood and the speaker. Shouldn't have much of an
effect on the sound, if any. Maybe your wife or girlfriend has a pair of
black nylons she's about ready to throw away ;-)

For that application (all things considered) he could probably glue a
piece of cheese cloth over the opening and never know the difference
other than a VERY slight degradation in volume. In short, most anything
would work. Nylons would work but I'd have some concerns about longevity.


Cheesecloth is too pores (SP) too soft/stretchy. Nylon's would be
better and have a sexy sound. (g) but the best would be a stiffer
cloth.

If the speaker is going in a box the harder the wood the more it
reflects sound. Also drill a small hole for the back side of the
speaker to allow the diaphragm to fluctuate freely, you can tune the
speaker by the size of the hole.

All valid points but in this instance he refers to 1/8" slots covering
the speaker opening. I wouldn't be worried too much about the
"stretchiness" of the cloth nor, for that matter, the porosity (read:
Acoustic Transparency) of that material. Likewise, if we go away from
1/8" slots, we may find that SWMBO's used panty hose will not be
sufficiently strong to withstand repeated finger pokes after x number of
months of exposure to UV light, etc.

Yeah, you are right about that, I was not even thinking of the fact
that it is a plastic material.

On Tue, 29 Mar 2016 21:48:19 -0400, krw wrote:

On Tue, 29 Mar 2016 14:12:26 -0500, Leon lcb11211@swbelldotnet
wrote:

On 3/29/2016 1:20 PM, John McCoy wrote:
Puckdropper puckdropper(at)yahoo(dot)com wrote in
b.com:

Leon lcb11211@swbelldotnet wrote in news:d-ednSYZkf_9JmfLnZ2dnUU7-
:

That is not true either. Long ago many speakers were built to be air
tight. Case in point many subwolfers use a driver speaker and a
slave speaker inside the same enclosure. The whole speaker assembly
is dependent on being air tight for the slave speaker to function and
produce sound.

What would the slave speaker tend to look like? Basically like a
speaker without a magnet? I picked up a speaker from Walmart that had
one real speaker and one that kinda looked like a decoy or fake
speaker.

Slave speaker is a special case - in that case the slave is
moving outward when the driven speaker is moving inward, and
vice-versa, so the volume of air inside the enclosure doesn't
change.


The air volume does not change in a sealed speaker either. The pressure
does change but not the volume.

The volume of air obviously changes as the volume increases. ;-) The
quantity of air is constant, the pressure is changing, so the volume
must change (inversely). Remember, the speaker cone is moving.

Yet if there is no vent the volume of air does not change, only the
pressure changes. So the sound is dampened in that the speaker is not
free to fully travel, unless it is a metal coned speaker. I believe
that is what Leon was referring to.




With two driven speakers, if the enclosure is airtight you're
compressing (or decompressing) the air in the enclosure, which
is generating a force opposing the way the speaker is being
driven.

Not so if the speakers are air tight in their own compartments inside
the speaker housing, which apparently is how my center speaker with 2,
5" speakers is set up.


How much force depends on how big the speaker is, and
how much volume is in the enclosure. If your enclosure is
small, it can have an appreciable effect.

John

On 28 Mar 2016 22:10:44 GMT, Puckdropper
puckdropper(at)yahoo(dot)com wrote:

I've got a Raspberry Pi 3 and the official Raspberry Pi Touchscreen that
I'm working on building a case for. I've come across a design decision I'd
like a little input on.

I have an amplifier and speaker arrangement to give me basic sound. I'm
using 2 small speakers, about 1" by 2". The speakers are in their own
plastic enclosure with a provision to mount the speaker using a
sufficiently small screw, probably 2-56 maybe 1-72. FWIW, the case will
probably be pine.

It makes sense to make some form of grill or hole in the wood to make sure
the sound can pass unobstructed. I could possibly cut 1/8" wide slots with
an endmill or drill a series of holes. Which would be better, or does it
matter?

Also, I'd like to keep little bits of debris from sticking to the speaker
cone. Would a piece of cotton cloth or something similar work as "speaker
fabric" without affecting the sound too much?

Thanks,

Puckdropper

I'm curious, is your Pi for a special purpose or experimentation? How
did you get one so fast?

OFWW wrote in
:


I'm curious, is your Pi for a special purpose or experimentation? How
did you get one so fast?


It's mainly for playing with right now. I've got a Pi 2 that I'm hooking
up my Digitrax PR3 programmer to, and may do so with the Pi 3.

I got lucky, I guess. I ordered the official touch screen from MCM and
preordered a Pi 3 about 3 weeks before it was available. They delayed
shipping the touch screen until the Pi 3 was available.

The touch screen is a nice bit of hardware, I've played with it for several
hours already and the only problems I have are basically Fitt's Law
related... Kinda hard to hit a 5-pixel by 10-pixel target with your huge
50x50 pixel fingers.

Puckdropper

OFWW wrote in
:

On Tue, 29 Mar 2016 21:48:19 -0400, krw wrote:

On Tue, 29 Mar 2016 14:12:26 -0500, Leon lcb11211@swbelldotnet
wrote:

The air volume does not change in a sealed speaker either. The
pressure does change but not the volume.

The volume of air obviously changes as the volume increases. ;-) The
quantity of air is constant, the pressure is changing, so the volume
must change (inversely). Remember, the speaker cone is moving.

Yet if there is no vent the volume of air does not change, only the
pressure changes. So the sound is dampened in that the speaker is not
free to fully travel, unless it is a metal coned speaker. I believe
that is what Leon was referring to.

Eh? You guys are trying to re-write the laws of physics here.
Boyle's gas law applies, p1v1 = p2v2, just as krw said.

This is not complicated - assume there is a speaker in a
sealed box. The speaker cone moves as it's being driven with
the audio signal. As the cone moves outward, the volume
inside the box increases, and the pressure decreases. As
it moves inwards, the volume in the box decreases and the
pressure increases.

As noted (several times) whether these changes are significant
depends on the size of the box relative to the speaker.

John

On 3/29/2016 8:48 PM, krw wrote:
On Tue, 29 Mar 2016 14:12:26 -0500, Leon lcb11211@swbelldotnet
wrote:

On 3/29/2016 1:20 PM, John McCoy wrote:
Puckdropper puckdropper(at)yahoo(dot)com wrote in
b.com:

Leon lcb11211@swbelldotnet wrote in news:d-ednSYZkf_9JmfLnZ2dnUU7-
:

That is not true either. Long ago many speakers were built to be air
tight. Case in point many subwolfers use a driver speaker and a
slave speaker inside the same enclosure. The whole speaker assembly
is dependent on being air tight for the slave speaker to function and
produce sound.

What would the slave speaker tend to look like? Basically like a
speaker without a magnet? I picked up a speaker from Walmart that had
one real speaker and one that kinda looked like a decoy or fake
speaker.

Slave speaker is a special case - in that case the slave is
moving outward when the driven speaker is moving inward, and
vice-versa, so the volume of air inside the enclosure doesn't
change.


The air volume does not change in a sealed speaker either. The pressure
does change but not the volume.

The volume of air obviously changes as the volume increases. ;-) The
quantity of air is constant, the pressure is changing, so the volume
must change (inversely). Remember, the speaker cone is moving.

The volume remains the same, where does it go when it is in a sealed
container? Would volume and quantity be the same measurement?
Now if the speaker has an opening the volume does change. Speaker
movement in a sealed cabinet would simply increase and decrease
pressure. We are measuring air, not displacement. Displacement would
certainly change.







With two driven speakers, if the enclosure is airtight you're
compressing (or decompressing) the air in the enclosure, which
is generating a force opposing the way the speaker is being
driven.

Not so if the speakers are air tight in their own compartments inside
the speaker housing, which apparently is how my center speaker with 2,
5" speakers is set up.


How much force depends on how big the speaker is, and
how much volume is in the enclosure. If your enclosure is
small, it can have an appreciable effect.

John

On 3/30/2016 9:47 AM, John McCoy wrote:
OFWW wrote in
:

On Tue, 29 Mar 2016 21:48:19 -0400, krw wrote:

On Tue, 29 Mar 2016 14:12:26 -0500, Leon lcb11211@swbelldotnet
wrote:

The air volume does not change in a sealed speaker either. The
pressure does change but not the volume.

The volume of air obviously changes as the volume increases. ;-) The
quantity of air is constant, the pressure is changing, so the volume
must change (inversely). Remember, the speaker cone is moving.

Yet if there is no vent the volume of air does not change, only the
pressure changes. So the sound is dampened in that the speaker is not
free to fully travel, unless it is a metal coned speaker. I believe
that is what Leon was referring to.

Eh? You guys are trying to re-write the laws of physics here.
Boyle's gas law applies, p1v1 = p2v2, just as krw said.

This is not complicated - assume there is a speaker in a
sealed box. The speaker cone moves as it's being driven with
the audio signal. As the cone moves outward, the volume
inside the box increases, and the pressure decreases. As
it moves inwards, the volume in the box decreases and the
pressure increases.

Nope, in a sealed speaker the same amount of air is in the enclosure
regardless if the speaker cone is moving in or out. What you are
confusing is displacement. The measurable area, not air volume, inside
the speaker changes but not the volume of air. Air easily compressed
and decompresses, that does not decrease the volume of air.




As noted (several times) whether these changes are significant
depends on the size of the box relative to the speaker.

John

On 3/30/2016 1:48 AM, OFWW wrote:
On Tue, 29 Mar 2016 21:48:19 -0400, krw wrote:

On Tue, 29 Mar 2016 14:12:26 -0500, Leon lcb11211@swbelldotnet
wrote:

On 3/29/2016 1:20 PM, John McCoy wrote:
Puckdropper puckdropper(at)yahoo(dot)com wrote in
b.com:

Leon lcb11211@swbelldotnet wrote in news:d-ednSYZkf_9JmfLnZ2dnUU7-
:

That is not true either. Long ago many speakers were built to be air
tight. Case in point many subwolfers use a driver speaker and a
slave speaker inside the same enclosure. The whole speaker assembly
is dependent on being air tight for the slave speaker to function and
produce sound.

What would the slave speaker tend to look like? Basically like a
speaker without a magnet? I picked up a speaker from Walmart that had
one real speaker and one that kinda looked like a decoy or fake
speaker.

Slave speaker is a special case - in that case the slave is
moving outward when the driven speaker is moving inward, and
vice-versa, so the volume of air inside the enclosure doesn't
change.


The air volume does not change in a sealed speaker either. The pressure
does change but not the volume.

The volume of air obviously changes as the volume increases. ;-) The
quantity of air is constant, the pressure is changing, so the volume
must change (inversely). Remember, the speaker cone is moving.

Yet if there is no vent the volume of air does not change, only the
pressure changes. So the sound is dampened in that the speaker is not
free to fully travel, unless it is a metal coned speaker. I believe
that is what Leon was referring to.

Yes, speaker cone movement in a sealed enclosure neither creates or
eliminates air. It simply compresses and decompress the air.

On 3/29/2016 8:43 PM, krw wrote:
On Tue, 29 Mar 2016 15:43:40 -0000 (UTC), John McCoy
wrote:

OFWW wrote in
:

Cheesecloth is too pores (SP) too soft/stretchy. Nylon's would be
better and have a sexy sound. (g) but the best would be a stiffer
cloth.

This sort of depends on how concerned you are with the sound
quality. A soft, porous cloth will attenuate the sound, and
affect the tone. If you want good acoustics, use a stiff cloth.
If you just want to keep debris out, use whatever's handy.

If the speaker is going in a box the harder the wood the more it
reflects sound. Also drill a small hole for the back side of the
speaker to allow the diaphragm to fluctuate freely, you can tune the
speaker by the size of the hole.

This is important - not the tuning, but having some sort of
vent on the backside of the speaker. A speaker makes sound
by pushing air forwards and back, and if there's no way for
air to move behind the speaker, it's not going to move much
air in front either. Result - not much sound. (this is
assuming the box is smallish - a big box with small speakers
has enough volume inside it won't need a vent).

That depends on the speaker. "Acoustic suspension" speakers aren't
ported. They rely on the back pressure to return the speaker to its
midpoint.


AKA Air Suspension speakers.

Leon wrote:


Yes, speaker cone movement in a sealed enclosure neither creates or
eliminates air. It simply compresses and decompress the air.


Not really Leon. The front of the speaker enclosure is open - or else
you wouldn't hear the sound. Volume does change instantaneously as the
cone moves. When you are pushing air out, you can't be sucking air in
at the same time if the enclosure is sealed and the only opening is
where the air is being pushed out. Compressing air if it can't escape
to the outside world would not create sound in the outside world.


--
-Mike-

On 3/30/2016 1:27 PM, Mike Marlow wrote:
Leon wrote:


Yes, speaker cone movement in a sealed enclosure neither creates or
eliminates air. It simply compresses and decompress the air.


Not really Leon. The front of the speaker enclosure is open - or else
you wouldn't hear the sound. Volume does change instantaneously as the
cone moves. When you are pushing air out, you can't be sucking air in
at the same time if the enclosure is sealed and the only opening is
where the air is being pushed out. Compressing air if it can't escape
to the outside world would not create sound in the outside world.

\

Naturally the front of the speaker cone is open, but the back is/was
often ins an air tight environment.


I hate looking the info up but this kinda supports my comments.

http://www.audioholics.com/loudspeak...aled-vs-ported

Leon wrote:


Naturally the front of the speaker cone is open, but the back is/was
often ins an air tight environment.


I hate looking the info up but this kinda supports my comments.


Well... not so much. If I understand your earlier comments correctly,
you are interpreting a sealed chamber to mean an completely sealed
chamber. That's the point I commented on. It's not completely sealed
as long as the front of the speaker is open. The balance of the speaker
cabinet is neutralized to atmospheric pressure by that opening. It's
only that sound is directed by that sealed back. Not that volume and/or
pressure remain constant.


--
-Mike-

On 3/30/2016 4:51 PM, Mike Marlow wrote:
Leon wrote:


Naturally the front of the speaker cone is open, but the back is/was
often ins an air tight environment.


I hate looking the info up but this kinda supports my comments.


Well... not so much. If I understand your earlier comments correctly,
you are interpreting a sealed chamber to mean an completely sealed
chamber. That's the point I commented on. It's not completely sealed
as long as the front of the speaker is open. The balance of the speaker
cabinet is neutralized to atmospheric pressure by that opening. It's
only that sound is directed by that sealed back. Not that volume and/or
pressure remain constant.



No the front of the speaker is open, obviously but the box in many cases
is air tight. You probably came into the conversation late and are
missing the key points.

Previous posts indicated the need for a vented port so that the speaker
would operate. I said that this was not true. There seemed to be some
thoughts that a speaker would not operate if it had a sealed compartment
behind it, which is not true.

Leon wrote:
On 3/30/2016 4:51 PM, Mike Marlow wrote:
Leon wrote:


Naturally the front of the speaker cone is open, but the back is/was
often ins an air tight environment.


I hate looking the info up but this kinda supports my comments.


Well... not so much. If I understand your earlier comments correctly,
you are interpreting a sealed chamber to mean an completely sealed
chamber. That's the point I commented on. It's not completely sealed
as long as the front of the speaker is open. The balance of the speaker
cabinet is neutralized to atmospheric pressure by that opening. It's
only that sound is directed by that sealed back. Not that volume and/or
pressure remain constant.



No the front of the speaker is open, obviously but the box in many cases
is air tight. You probably came into the conversation late and are
missing the key points.

Previous posts indicated the need for a vented port so that the speaker
would operate. I said that this was not true. There seemed to be some
thoughts that a speaker would not operate if it had a sealed compartment
behind it, which is not true.

Agreed Leon - I did come into it late and maybe I misunderstood some
points from the time I came in. I picked up on it where I thought I
read that a sealed cabinet had a constant volume and that's where my
initial comment entered. Sealed backs are one thing but there is no
such thing as a speaker cabinet with a sealed compartment. At the very
least, atmospheric pressure enters the chamber through the speaker cone.

--
-Mike-

Mike Marlow wrote:
Leon wrote:
On 3/30/2016 4:51 PM, Mike Marlow wrote:
Leon wrote:


Naturally the front of the speaker cone is open, but the back is/was
often ins an air tight environment.


I hate looking the info up but this kinda supports my comments.


Well... not so much. If I understand your earlier comments correctly,
you are interpreting a sealed chamber to mean an completely sealed
chamber. That's the point I commented on. It's not completely sealed
as long as the front of the speaker is open. The balance of the speaker
cabinet is neutralized to atmospheric pressure by that opening. It's
only that sound is directed by that sealed back. Not that volume and/or
pressure remain constant.



No the front of the speaker is open, obviously but the box in many cases
is air tight. You probably came into the conversation late and are
missing the key points.

Previous posts indicated the need for a vented port so that the speaker
would operate. I said that this was not true. There seemed to be some
thoughts that a speaker would not operate if it had a sealed compartment
behind it, which is not true.

Agreed Leon - I did come into it late and maybe I misunderstood some
points from the time I came in. I picked up on it where I thought I
read that a sealed cabinet had a constant volume and that's where my
initial comment entered. Sealed backs are one thing but there is no
such thing as a speaker cabinet with a sealed compartment. At the very
least, atmospheric pressure enters the chamber through the speaker cone.


On second thought - maybe I really do not understand enough about
speaker design to make the statement that I made above...

--
-Mike-

On 2016-03-30, Mike Marlow wrote:

On second thought - maybe I really do not understand enough about
speaker design to make the statement that I made above...

BUT!!! ....we cannot possibly extend such an equally forgiving POV to
ol' notbob. He's obviously wrong and not deserving of our
forgiveness. Die, notbob! Die!

(c'mon, Mike, ya' know you wanna say it)

We having fun, yet?

nb

notbob wrote:
On 2016-03-30, Mike Marlow wrote:

On second thought - maybe I really do not understand enough about
speaker design to make the statement that I made above...

BUT!!! ....we cannot possibly extend such an equally forgiving POV to
ol' notbob. He's obviously wrong and not deserving of our
forgiveness. Die, notbob! Die!

(c'mon, Mike, ya' know you wanna say it)

We having fun, yet?


Dude - you are one sick puppy.


--
-Mike-

On 2016-03-30, Mike Marlow wrote:

Dude - you are one sick puppy.

Mike - I'm too old to be a "Dude" and I've never been a "puppy". I
will admit my being "sick" is still in question, though. OTOH, if you
wanna dog me in this newsgroup, I'm up for it.

Despite having givin up this nonsense, years ago, the diminishing size
of usenet has made me long for more interaction. Wanna be my dance
partner?

nb

Leon lcb11211@swbelldotnet wrote in news:RZadnZ9w85XqcWbLnZ2dnUU7-
:


Nope, in a sealed speaker the same amount of air is in the enclosure
regardless if the speaker cone is moving in or out.

Not to beat a dead horse, but you are the one confused.
Go look up Boyle's Law on Wikipedia.

John

On Tue, 29 Mar 2016 23:48:46 -0700, OFWW wrote:

On Tue, 29 Mar 2016 21:48:19 -0400, krw wrote:

On Tue, 29 Mar 2016 14:12:26 -0500, Leon lcb11211@swbelldotnet
wrote:

On 3/29/2016 1:20 PM, John McCoy wrote:
Puckdropper puckdropper(at)yahoo(dot)com wrote in
b.com:

Leon lcb11211@swbelldotnet wrote in news:d-ednSYZkf_9JmfLnZ2dnUU7-
:

That is not true either. Long ago many speakers were built to be air
tight. Case in point many subwolfers use a driver speaker and a
slave speaker inside the same enclosure. The whole speaker assembly
is dependent on being air tight for the slave speaker to function and
produce sound.

What would the slave speaker tend to look like? Basically like a
speaker without a magnet? I picked up a speaker from Walmart that had
one real speaker and one that kinda looked like a decoy or fake
speaker.

Slave speaker is a special case - in that case the slave is
moving outward when the driven speaker is moving inward, and
vice-versa, so the volume of air inside the enclosure doesn't
change.


The air volume does not change in a sealed speaker either. The pressure
does change but not the volume.

The volume of air obviously changes as the volume increases. ;-) The
quantity of air is constant, the pressure is changing, so the volume
must change (inversely). Remember, the speaker cone is moving.

Yet if there is no vent the volume of air does not change, only the
pressure changes. So the sound is dampened in that the speaker is not
free to fully travel, unless it is a metal coned speaker. I believe
that is what Leon was referring to.

If there is no vent, of course the volume changes. The speaker cone
moves, so the volume *has* to change. The air trapped inside the box
is the spring for the cone. This is an "acoustic suspension" speaker
(and they work quite well).



With two driven speakers, if the enclosure is airtight you're
compressing (or decompressing) the air in the enclosure, which
is generating a force opposing the way the speaker is being
driven.

Not so if the speakers are air tight in their own compartments inside
the speaker housing, which apparently is how my center speaker with 2,
5" speakers is set up.


How much force depends on how big the speaker is, and
how much volume is in the enclosure. If your enclosure is
small, it can have an appreciable effect.

John

On Wed, 30 Mar 2016 10:09:55 -0500, Leon lcb11211@swbelldotnet
wrote:

On 3/30/2016 9:47 AM, John McCoy wrote:
OFWW wrote in
:

On Tue, 29 Mar 2016 21:48:19 -0400, krw wrote:

On Tue, 29 Mar 2016 14:12:26 -0500, Leon lcb11211@swbelldotnet
wrote:

The air volume does not change in a sealed speaker either. The
pressure does change but not the volume.

The volume of air obviously changes as the volume increases. ;-) The
quantity of air is constant, the pressure is changing, so the volume
must change (inversely). Remember, the speaker cone is moving.

Yet if there is no vent the volume of air does not change, only the
pressure changes. So the sound is dampened in that the speaker is not
free to fully travel, unless it is a metal coned speaker. I believe
that is what Leon was referring to.

Eh? You guys are trying to re-write the laws of physics here.
Boyle's gas law applies, p1v1 = p2v2, just as krw said.

This is not complicated - assume there is a speaker in a
sealed box. The speaker cone moves as it's being driven with
the audio signal. As the cone moves outward, the volume
inside the box increases, and the pressure decreases. As
it moves inwards, the volume in the box decreases and the
pressure increases.

Nope, in a sealed speaker the same amount of air is in the enclosure
regardless if the speaker cone is moving in or out. What you are
confusing is displacement. The measurable area, not air volume, inside
the speaker changes but not the volume of air. Air easily compressed
and decompresses, that does not decrease the volume of air.

The same "amount" of air is in the box but the *volume* is not
constant. The pressure is the inverse of the volume (for the given
"amount" of air trapped in the box.




As noted (several times) whether these changes are significant
depends on the size of the box relative to the speaker.

John

Mike Marlow wrote in
:

Mike Marlow wrote:

Agreed Leon - I did come into it late and maybe I misunderstood some
points from the time I came in. I picked up on it where I thought I
read that a sealed cabinet had a constant volume and that's where my
initial comment entered. Sealed backs are one thing but there is no
such thing as a speaker cabinet with a sealed compartment. At the
very least, atmospheric pressure enters the chamber through the
speaker cone.


On second thought - maybe I really do not understand enough about
speaker design to make the statement that I made above...


I do know that Soundtraxx Mini-oval speakers have an enclosure that the
speaker fits tightly into, magnet side out. There is no hole for a vent
in that enclosure, nor is one needed. At the same time, though, realize
the dimensions of the speaker & enclosure are only about 8mm by 20mm.
Sometimes rules change as things get smaller.

Puckdropper

John McCoy wrote:
Leon lcb11211@swbelldotnet wrote in news:RZadnZ9w85XqcWbLnZ2dnUU7-
:


Nope, in a sealed speaker the same amount of air is in the enclosure
regardless if the speaker cone is moving in or out.

Not to beat a dead horse, but you are the one confused.
Go look up Boyle's Law on Wikipedia.

John


Regardless, boules law has nothing to do with a speaker working correctly
whether it is ported or whether it is an air suspension/acoustical style
speaker.
Your earlier comments indicated that speakers had to be ported to equalize
air pressure on both sides of the speaker unless the enclosure was large
and the speakers were small. That simply is not true.

On 3/30/2016 5:40 PM, Mike Marlow wrote:

On second thought - maybe I really do not understand enough about
speaker design to make the statement that I made above...

Yep, and I built my own bass cabinets, as well as a few for others back
when I was young, and sexy, enough to lug an Ampex SVT head around.

Most of the speaker cabinets I built contained 15" woofers, moved a lot
of air, and were baffled/ported" very precisely according to speaker
cabinet gurus I knew when doing studio work, as well as some being
direct copies of well known speaker cabinets ... much like I would
reproduce a chair for someone these days.

There is ton of physics that goes into designing a pleasing sounding
speaker ... with a bit of magic thrown. My studio was a (paid) test bed
for many of the more well known studio speakers down through the years.

I can say yeah or nay for the sound, but certainly wouldn't presume to
expound definitely on the physics, particularly when it comes to the
highly dynamic volume/pressures of air, inside and out, therefore the
precise "porting" requirements, in order to tune certain types of
speakers to a very specific frequency for desired bass reproduction.

--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://www.google.com/+eWoodShop
https://plus.google.com/+KarlCaillouet/posts
http://www.custommade.com/by/ewoodshop/
https://www.facebook.com/eWoodShop-206166666122228
KarlCaillouet@ (the obvious)

On 3/30/2016 5:24 PM, Leon wrote:

No the front of the speaker is open, obviously but the box in many cases
is air tight. You probably came into the conversation late and are
missing the key points.

Yep ... the idea of sealed enclosure speakers, a very specific type of
speaker design, is to allow the air behind the speaker to act pretty
much like a spring, which helps control the movement of the speaker
within its design limits.

It would have to be (relatively) "sealed" in order to do so.

--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://www.google.com/+eWoodShop
https://plus.google.com/+KarlCaillouet/posts
http://www.custommade.com/by/ewoodshop/
https://www.facebook.com/eWoodShop-206166666122228
KarlCaillouet@ (the obvious)

Leon wrote in
:

Your earlier comments indicated that speakers had to be ported to
equalize air pressure on both sides of the speaker unless the
enclosure was large and the speakers were small. That simply is not
true.

What I actually said (regardless of what you think I
"indicated") was that you won't get as much sound if the
case isn't vented. Which is simply true and always will
be (except, as krw pointed out, in the special case of
air suspension speakers).

Actually, there is another special case - if the enclosure
is thin enough to flex. In that case the enclosure itself
will act like a slave speaker. This tends to sound really
awful.

John