[Zilog]

Hi,
I need a chamber where amps (guitar, PA) are tested at full power and
with a real life signal.
I need to make it "sound proof" and there must be a method to get rid
of the excessive heat generated by the amp under test.
Of course a few speakers are placed in this room.
What do we have:
A room with a surface area of about 3 by 2 meters and 2.5 meters high.
Floor is concrete, walls are of concrete blocs 14 cm thick.
Of course I do not have an arm or a leg to pay for materials so it has
to be fairly cheap.

Where do I start?

Thanks,

Zilog

[Scott Dorsey]

Zilog wrote:
I need a chamber where amps (guitar, PA) are tested at full power and
with a real life signal.
I need to make it "sound proof" and there must be a method to get rid
of the excessive heat generated by the amp under test.
Of course a few speakers are placed in this room.
What do we have:
A room with a surface area of about 3 by 2 meters and 2.5 meters high.
Floor is concrete, walls are of concrete blocs 14 cm thick.
Of course I do not have an arm or a leg to pay for materials so it has
to be fairly cheap.

Where do I start?

1. Get more money.

2. Build a room within a room, floated on doughnut mounts.

3. Remote the amplifier stages and put only the speaker cabinets in the room.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Ethan Winer]

Zilog,

A room with a surface area of about 3 by 2 meters and 2.5 meters high.

Besides Scott's good advice, understand that a "room" like this is horribly
boxy sounding. The only way you'll get a decent sound that's not riddled
with comb filtering peaks and nulls is to add absorption a foot thick all
around on every surface.

--Ethan

[Richard Crowley]

"Zilog" wrote ...
I need a chamber where amps (guitar, PA) are tested at full power and with
a real life signal.
I need to make it "sound proof" and there must be a method to get rid of
the excessive heat generated by the amp under test.
Of course a few speakers are placed in this room.
What do we have:
A room with a surface area of about 3 by 2 meters and 2.5 meters high.
Floor is concrete, walls are of concrete blocs 14 cm thick.
Of course I do not have an arm or a leg to pay for materials so it has to
be fairly cheap.

Not clear what the room and speakers are for if you are only testing "amps"?

Perhaps you should better define your terms...

Does "amps" just mean the electronic amplifiers, or do you mean
some kind of integrated product with both amplifier and speakers?
Amplifiers are typically tested with "dummy loads" (resistors of
the same impedance as the speakers would be).

Does "test" mean just measuring what the amplifier will do (how
much power, how much distortion, etc.), or does it include how
it "sounds" through speakers?

Is your concrete floor on the ground, or is it an upper floor?
Do your concrete blocks have open spaces inside, or are they
filled with concrete?
What is the ceiling/roof?
Can you test off-hours (when lack of isolation is not so much
a problem)?
Does your test room have to "sound" reasonable, will you have
humans inside it during testing? or is it intended only to contain
the noise?

[Zilog]

Ethan Winer wrote:
Zilog,

A room with a surface area of about 3 by 2 meters and 2.5 meters high.

Besides Scott's good advice, understand that a "room" like this is horribly
boxy sounding. The only way you'll get a decent sound that's not riddled
with comb filtering peaks and nulls is to add absorption a foot thick all
around on every surface.

--Ethan


Thanks for the replies.

I do not want to take acoustic measurements.
The main purpose is the testing of guitar amplifiers and check their
behavior at full power.
I then can find and eliminate resonance problems to start with but also
"strange" noises when played at high volumes either from the instrument
or by the amp or cabinet.

A thing I can not do without such a room. (The whole street will hang at
my doorbell because of the noise)
Today I do these test for a very short time. It's not so good for my
hearing... And from time to time I can't find the problem as the level
where the problem occurs is to high.

I understand that I have to make a room inside the room and isolate it
properly.

But we are getting close now.
What material should I use to isolate this room?
How to get rid of the generated heath?

Taking in to account a limited budget...

Links to materials, examples, experience etc is very much appreciated.

Cheers,

Zilog

[Zilog]

Richard Crowley wrote:
"Zilog" wrote ...
I need a chamber where amps (guitar, PA) are tested at full power and with
a real life signal.
I need to make it "sound proof" and there must be a method to get rid of
the excessive heat generated by the amp under test.
Of course a few speakers are placed in this room.
What do we have:
A room with a surface area of about 3 by 2 meters and 2.5 meters high.
Floor is concrete, walls are of concrete blocs 14 cm thick.
Of course I do not have an arm or a leg to pay for materials so it has to
be fairly cheap.

Not clear what the room and speakers are for if you are only testing "amps"?

Perhaps you should better define your terms...
These amps and speakers are tested with real live signals. Coming either
from an audio source, such as a cd player, or from a guitar.

Does "amps" just mean the electronic amplifiers, or do you mean
some kind of integrated product with both amplifier and speakers?
Amplifiers are typically tested with "dummy loads" (resistors of
the same impedance as the speakers would be).
Amps mean the integrated ones, called "Combo"
The amps are tested on dummy loads outside of the "sound proof" room.
That's the electrical test.


Does "test" mean just measuring what the amplifier will do (how
much power, how much distortion, etc.), or does it include how
it "sounds" through speakers?
The "sound" has to be checked.
Distortion is not a real issue; ratling noise and intermittent pops and
cracks at full power is the real reason.
Some amps emit a particular noise, crack, pop, etc when played with a
guitar at a certain level and certain frequency.
Asking wich frequency and wich volume, you can understand that such a
room is needed do find out what the problem can be.

Is your concrete floor on the ground, or is it an upper floor?
It's on the ground.

Do your concrete blocks have open spaces inside, or are they
filled with concrete?
Thes blocks are hollow inside.

What is the ceiling/roof?
From outside to the inside: Metal roof, air, wooden structure with 12
cm of fiberglass insulation

Can you test off-hours (when lack of isolation is not so much
a problem)?
I can test off- hours but it's in a residential erea, so it has to be
"sound proof"

Does your test room have to "sound" reasonable,
I would like it but not nesecary

will you have humans inside it during testing?
That can happen but it's very, very rare.

or is it intended only to contain the noise?
Yep, mainly



Thanks for the further questions,

Zilog

[Kevin T]

Zilog wrote:
Richard Crowley wrote:
"Zilog" wrote ...
I need a chamber where amps (guitar, PA) are tested at full power and with
a real life signal.
I need to make it "sound proof" and there must be a method to get rid of
the excessive heat generated by the amp under test.
Of course a few speakers are placed in this room.
What do we have:
A room with a surface area of about 3 by 2 meters and 2.5 meters high.
Floor is concrete, walls are of concrete blocs 14 cm thick.
Of course I do not have an arm or a leg to pay for materials so it has to
be fairly cheap.

Not clear what the room and speakers are for if you are only testing "amps"?

Perhaps you should better define your terms...
These amps and speakers are tested with real live signals. Coming either
from an audio source, such as a cd player, or from a guitar.

Does "amps" just mean the electronic amplifiers, or do you mean
some kind of integrated product with both amplifier and speakers?
Amplifiers are typically tested with "dummy loads" (resistors of
the same impedance as the speakers would be).
Amps mean the integrated ones, called "Combo"
The amps are tested on dummy loads outside of the "sound proof" room.
That's the electrical test.


Does "test" mean just measuring what the amplifier will do (how
much power, how much distortion, etc.), or does it include how
it "sounds" through speakers?
The "sound" has to be checked.
Distortion is not a real issue; ratling noise and intermittent pops and
cracks at full power is the real reason.
Some amps emit a particular noise, crack, pop, etc when played with a
guitar at a certain level and certain frequency.
Asking wich frequency and wich volume, you can understand that such a
room is needed do find out what the problem can be.

Is your concrete floor on the ground, or is it an upper floor?
It's on the ground.

Do your concrete blocks have open spaces inside, or are they
filled with concrete?
Thes blocks are hollow inside.

What is the ceiling/roof?
From outside to the inside: Metal roof, air, wooden structure with 12
cm of fiberglass insulation

Can you test off-hours (when lack of isolation is not so much
a problem)?
I can test off- hours but it's in a residential erea, so it has to be
"sound proof"

Does your test room have to "sound" reasonable,
I would like it but not nesecary

will you have humans inside it during testing?
That can happen but it's very, very rare.

or is it intended only to contain the noise?
Yep, mainly



Thanks for the further questions,

Zilog

How many times will you do this testing 10? 100?
How much Profits involved in this busness model?
Who's paying to remove pops during EVH "eruption" solos?

If this is just for fun / hobbie The answers you seek are very
different .

Kevin T

[Richard Crowley]

"Zilog" wrote ...
I can test off- hours but it's in a residential erea,
so it has to be "sound proof"

In a residential area, "off-hours" may mean in the
middle of the day when most people are at work
or school, or whatever.

[Rob Reedijk]

Zilog wrote:
Hi,
I need a chamber where amps (guitar, PA) are tested at full power and
with a real life signal.
I need to make it "sound proof" and there must be a method to get rid
of the excessive heat generated by the amp under test.
Of course a few speakers are placed in this room.
What do we have:
A room with a surface area of about 3 by 2 meters and 2.5 meters high.
Floor is concrete, walls are of concrete blocs 14 cm thick.
Of course I do not have an arm or a leg to pay for materials so it has
to be fairly cheap.

Where do I start?

If it's allowed to be ugly, this can be done cheap. I assume it's
temporary. Build a box in a box. Each box will have a plywood floor
and drywall walls. Fill the walls, floor and ceiling with insulation.
Try to have almost no solid contact between the two boxes. You will have
it through the floor since one must rest on the other. Use the pucks that
Scott mentioned for this and to rest the whole thing on your floor.
I would avoid the ventilation issue by making it large enough that you
can operate the amp for short periods without over-heating. You will
need to have two doors---one for each box lined up on the same side, with
a piece of insulation that you move in and out. Also, you will need
a conduit for cables. I would just put one in with enough line, mic
and power lines that you won't have to worry about it later. Make the
walls and floor thick. 8 inches? Use staggered 2x4s. Double up the
drywall for more isolation. Mass is your friend.

total cost? Couple hundred bucks.

Rob R.

[Zilog]

Rob Reedijk wrote:
Zilog wrote:
Hi,
I need a chamber where amps (guitar, PA) are tested at full power and
with a real life signal.
I need to make it "sound proof" and there must be a method to get rid
of the excessive heat generated by the amp under test.
Of course a few speakers are placed in this room.
What do we have:
A room with a surface area of about 3 by 2 meters and 2.5 meters high.
Floor is concrete, walls are of concrete blocs 14 cm thick.
Of course I do not have an arm or a leg to pay for materials so it has
to be fairly cheap.

Where do I start?

If it's allowed to be ugly, this can be done cheap. I assume it's
temporary. Build a box in a box. Each box will have a plywood floor
and drywall walls. Fill the walls, floor and ceiling with insulation.
Try to have almost no solid contact between the two boxes. You will have
it through the floor since one must rest on the other. Use the pucks that
Scott mentioned for this and to rest the whole thing on your floor.
I would avoid the ventilation issue by making it large enough that you
can operate the amp for short periods without over-heating. You will
need to have two doors---one for each box lined up on the same side, with
a piece of insulation that you move in and out. Also, you will need
a conduit for cables. I would just put one in with enough line, mic
and power lines that you won't have to worry about it later. Make the
walls and floor thick. 8 inches? Use staggered 2x4s. Double up the
drywall for more isolation. Mass is your friend.

total cost? Couple hundred bucks.

Rob R.

The construction has a permanent character and it's solely purpose is
testing amps and speakers at their max volume.

Can Fiberglass or rock wool be used for insulation?

I think if drywall is used I have to isolate it with acoustical foam
sheets to avoid to much reflections. These can make the "rattling" test
unreliable.

Ventilation I still see as a problem.
First for the equipment if it's on for some time (30 minutes)
and secondly, if a live test is done with a guitar and amp under test.
It will be very hot in there...

But maybe that can be solved with a microphone and monitor amp with
speakers outside the chamber.

The doors can swing the opposite way so that's solved to. (I forgot
about the doors...)
To insulate the inner box from the floor I have a box full of rubber
disks about 2 cm thick and 10 cm in diameter.
Is a pointed cone maybe a better solution to isolate the inner cabinet
from the floor; you know these thingies that are placed under turntables
or loudspeaker cabinets. Only bigger in size.

well, it's taking form.

More reactions are welcome and very much appreciated.

Zilog

[Rob Reedijk]

Zilog wrote:
Rob Reedijk wrote:
Zilog wrote:
Hi,
I need a chamber where amps (guitar, PA) are tested at full power and
with a real life signal.
I need to make it "sound proof" and there must be a method to get rid
of the excessive heat generated by the amp under test.
Of course a few speakers are placed in this room.
What do we have:
A room with a surface area of about 3 by 2 meters and 2.5 meters high.
Floor is concrete, walls are of concrete blocs 14 cm thick.
Of course I do not have an arm or a leg to pay for materials so it has
to be fairly cheap.

Where do I start?

If it's allowed to be ugly, this can be done cheap. I assume it's
temporary. Build a box in a box. Each box will have a plywood floor
and drywall walls. Fill the walls, floor and ceiling with insulation.
Try to have almost no solid contact between the two boxes. You will have
it through the floor since one must rest on the other. Use the pucks that
Scott mentioned for this and to rest the whole thing on your floor.
I would avoid the ventilation issue by making it large enough that you
can operate the amp for short periods without over-heating. You will
need to have two doors---one for each box lined up on the same side, with
a piece of insulation that you move in and out. Also, you will need
a conduit for cables. I would just put one in with enough line, mic
and power lines that you won't have to worry about it later. Make the
walls and floor thick. 8 inches? Use staggered 2x4s. Double up the
drywall for more isolation. Mass is your friend.

total cost? Couple hundred bucks.

Rob R.

The construction has a permanent character and it's solely purpose is
testing amps and speakers at their max volume.

Can Fiberglass or rock wool be used for insulation?

Don't know about rock wool, but yes to fiberglass. If you want to spend
more money, you can buy special types designed for absorbing sound.

I think if drywall is used I have to isolate it with acoustical foam
sheets to avoid to much reflections. These can make the "rattling" test
unreliable.

I forgot about this...

Ventilation I still see as a problem.
First for the equipment if it's on for some time (30 minutes)
and secondly, if a live test is done with a guitar and amp under test.
It will be very hot in there...

But maybe that can be solved with a microphone and monitor amp with
speakers outside the chamber.

Yup.

The doors can swing the opposite way so that's solved to. (I forgot
about the doors...)
To insulate the inner box from the floor I have a box full of rubber
disks about 2 cm thick and 10 cm in diameter.
Is a pointed cone maybe a better solution to isolate the inner cabinet
from the floor; you know these thingies that are placed under turntables
or loudspeaker cabinets. Only bigger in size.

These are metal, no? I think part of their use is that they hold the speaker
tightly in place which is a good thing for speakers but maybe not a good
thing for isolation.

Rob R.

[Laurence Payne]

On Wed, 16 Aug 2006 18:00:29 +0200, Zilog wrote:

Hi,
I need a chamber where amps (guitar, PA) are tested at full power and
with a real life signal.
I need to make it "sound proof" and there must be a method to get rid
of the excessive heat generated by the amp under test.
Of course a few speakers are placed in this room.
What do we have:
A room with a surface area of about 3 by 2 meters and 2.5 meters high.
Floor is concrete, walls are of concrete blocs 14 cm thick.
Of course I do not have an arm or a leg to pay for materials so it has
to be fairly cheap.

Where do I start?

You can't realistically build anything at home that will prevent a
full-power amp test from annoying the neighbours. How often do you
need to do this? Can you rent space in an industrial area for a few
hours at night?

[Zilog]

Laurence Payne wrote:
On Wed, 16 Aug 2006 18:00:29 +0200, Zilog wrote:

Hi,
I need a chamber where amps (guitar, PA) are tested at full power and
with a real life signal.
I need to make it "sound proof" and there must be a method to get rid
of the excessive heat generated by the amp under test.
Of course a few speakers are placed in this room.
What do we have:
A room with a surface area of about 3 by 2 meters and 2.5 meters high.
Floor is concrete, walls are of concrete blocs 14 cm thick.
Of course I do not have an arm or a leg to pay for materials so it has
to be fairly cheap.

Where do I start?

You can't realistically build anything at home that will prevent a
full-power amp test from annoying the neighbours. How often do you
need to do this? Can you rent space in an industrial area for a few
hours at night?

It can realistically be build at home. Room is not very big but it can
be used. I've seen and heard similar "boxes", but that was a long time
ago. The amps were Cerwin Vega's, huge power!
You could hear the music outside the box, yes, but that was at a very
modest level. My workshop is at about 50 meters away from the house.

I need to do this lets say five times a week.
At this time I can not fully test the repaired amps or those with
vibrations or the like.
- Electrical test is no problem; I can go up to 2000 Watts at 2, 4 or 8
Ohms (for those who are ready to ask me if I shouldn't use a dummy load)
- It's noise or additional sounds generated by the enclosure of the
amp, speakers or whatever mechanical item that can make noise or vibrate
at these levels.

Renting a space is out of the question.
I repair and then test the gear. I can't go to another place to setup
everything, measure, play guitar (for test purposes) and try to find the
problems.
Apart from being robbed when not there...

If needed and only if it's absolutely necessary I can make the room a
bit bigger but I prefer to stick to these measures as the space is
there, Idle at the moment.

Thanks for replying,

Zilog

[Arny Krueger]

"Zilog" wrote in message


I do not want to take acoustic measurements.
The main purpose is the testing of guitar amplifiers and
check their behavior at full power.
I then can find and eliminate resonance problems to start
with but also "strange" noises when played at high
volumes either from the instrument or by the amp or
cabinet.

An economic alternative might be an electrical network that simulates the
impedance curve of the kind of speakers your amplifiers are generally used
with.

[Scott Dorsey]

Arny Krueger wrote:
"Zilog" wrote in message


I do not want to take acoustic measurements.
The main purpose is the testing of guitar amplifiers and
check their behavior at full power.
I then can find and eliminate resonance problems to start
with but also "strange" noises when played at high
volumes either from the instrument or by the amp or
cabinet.

An economic alternative might be an electrical network that simulates the
impedance curve of the kind of speakers your amplifiers are generally used
with.

No, a big part of what he's looking for are cabinet problems and not
related to the actual electronics. I do think you have to drive the
cabinet at high levels for that. But I also think you probably want
to move to the country if you intend on doing that often. The real
estate is cheaper and the air is cleaner too.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Arny Krueger]

"Scott Dorsey" wrote in message

Arny Krueger wrote:
"Zilog" wrote in message


I do not want to take acoustic measurements.
The main purpose is the testing of guitar amplifiers and
check their behavior at full power.
I then can find and eliminate resonance problems to
start with but also "strange" noises when played at high
volumes either from the instrument or by the amp or
cabinet.

An economic alternative might be an electrical network
that simulates the impedance curve of the kind of
speakers your amplifiers are generally used with.

No, a big part of what he's looking for are cabinet
problems and not related to the actual electronics.

I dunno. He seems to be really confused about what he is looking for. But I
agree that the soundproof chamber would be the way to go if cabinet
resonances are on his agenda.


I do
think you have to drive the cabinet at high levels for
that.

Agreed.

But I also think you probably want to move to the
country if you intend on doing that often. The real
estate is cheaper and the air is cleaner too. --scott

There's an acoustical lab in town that does high-intensity testing of
loudspeaker drivers - same basic application. They use something like the
suspended chamber that you recommended, Scott.

[Zilog]

Arny Krueger wrote:
"Scott Dorsey" wrote in message

Arny Krueger wrote:
"Zilog" wrote in message


I do not want to take acoustic measurements.
The main purpose is the testing of guitar amplifiers and
check their behavior at full power.
I then can find and eliminate resonance problems to
start with but also "strange" noises when played at high
volumes either from the instrument or by the amp or
cabinet.
An economic alternative might be an electrical network
that simulates the impedance curve of the kind of
speakers your amplifiers are generally used with.

No, a big part of what he's looking for are cabinet
problems and not related to the actual electronics.

I dunno. He seems to be really confused about what he is looking for. But I
agree that the soundproof chamber would be the way to go if cabinet
resonances are on his agenda.


I do
think you have to drive the cabinet at high levels for
that.

Agreed.

But I also think you probably want to move to the
country if you intend on doing that often. The real
estate is cheaper and the air is cleaner too. --scott

There's an acoustical lab in town that does high-intensity testing of
loudspeaker drivers - same basic application. They use something like the
suspended chamber that you recommended, Scott.


Well That's exactly what I try to explain-ask-say.
I'm not confused about what I'm looking for.
It seems others are.

Indeed cabinet problems for one.

Second; Guitar amps are subjected to a lot of vibrations caused by the
speakers. These vibrations can cause unwanted noises and are hard to
find if not driven at high levels.

Moving to the country is no option. If that could be done (in my case) I
wouldn't ask about comments, tips and idea's on a Test chamber.
The only option seems to be a suspended chamber with acoustical
insulation. Thanks Scott.

I remain with the following questions:
1. What material can be used for acoustic insulation at a modest price.
2. How to get rid of the heath without destroying the acoustic (or non
acoustic) properties of the chamber.
And with these two questions I in fact started the conversation.

So who has experience in getting rid of excessive heath and in materials
for insulation.
Thanks folks,
Zilog

[GregS]

In article , Zilog wrote:
Arny Krueger wrote:
"Scott Dorsey" wrote in message

Arny Krueger wrote:
"Zilog" wrote in message


I do not want to take acoustic measurements.
The main purpose is the testing of guitar amplifiers and
check their behavior at full power.
I then can find and eliminate resonance problems to
start with but also "strange" noises when played at high
volumes either from the instrument or by the amp or
cabinet.
An economic alternative might be an electrical network
that simulates the impedance curve of the kind of
speakers your amplifiers are generally used with.

No, a big part of what he's looking for are cabinet
problems and not related to the actual electronics.

I dunno. He seems to be really confused about what he is looking for. But I
agree that the soundproof chamber would be the way to go if cabinet
resonances are on his agenda.


I do
think you have to drive the cabinet at high levels for
that.

Agreed.

But I also think you probably want to move to the
country if you intend on doing that often. The real
estate is cheaper and the air is cleaner too. --scott

There's an acoustical lab in town that does high-intensity testing of
loudspeaker drivers - same basic application. They use something like the
suspended chamber that you recommended, Scott.


Well That's exactly what I try to explain-ask-say.
I'm not confused about what I'm looking for.
It seems others are.

Indeed cabinet problems for one.

Second; Guitar amps are subjected to a lot of vibrations caused by the
speakers. These vibrations can cause unwanted noises and are hard to
find if not driven at high levels.

Moving to the country is no option. If that could be done (in my case) I
wouldn't ask about comments, tips and idea's on a Test chamber.
The only option seems to be a suspended chamber with acoustical
insulation. Thanks Scott.

I remain with the following questions:
1. What material can be used for acoustic insulation at a modest price.
2. How to get rid of the heath without destroying the acoustic (or non
acoustic) properties of the chamber.
And with these two questions I in fact started the conversation.

By health I assume mean ear spl levels.
You didn't answer all my questions so I can only say, foam or fiberglass
is good for putting on top of block walls. if you don't have a block wall, then a heavy
material is needed, like MDF or particle board. All holes must be sealed, but you
need ventillation. Without reverbaration, the SPL will be greatly diminished at
any distance from the speaker, especially off to the side. Espicially an open back enclosure
will have little spl.

greg

So who has experience in getting rid of excessive heath and in materials
for insulation.
Thanks folks,
Zilog

[Zilog]

GregS wrote:
In article , Zilog wrote:
Arny Krueger wrote:
"Scott Dorsey" wrote in message

Arny Krueger wrote:
"Zilog" wrote in message


I do not want to take acoustic measurements.

Snip
Snip

I remain with the following questions:
1. What material can be used for acoustic insulation at a modest price.
2. How to get rid of the heath without destroying the acoustic (or non
acoustic) properties of the chamber.
And with these two questions I in fact started the conversation.

By health I assume mean ear spl levels.
You didn't answer all my questions so I can only say, foam or fiberglass
is good for putting on top of block walls. if you don't have a block wall, then a heavy
material is needed, like MDF or particle board. All holes must be sealed, but you
need ventillation. Without reverbaration, the SPL will be greatly diminished at
any distance from the speaker, especially off to the side. Espicially an open back enclosure
will have little spl.

greg

So who has experience in getting rid of excessive heath and in materials
for insulation.
Thanks folks,
Zilog


Up until now we have:
Concrete floor, hollow building blocks on 3 sides, A roof made up of
wood and iron plates and no door.

What do I have to do:
Make a door (two doors, one outside and one inside) so that we have a
room. Isolate the roof with fiberglass.
Build inside that "room" another room.
Well isolated from each other and suspended from the floor and walls by
the use of rubber parts (I do have them)
Add another layer of fiber glass on the inside and cover it with a thin
sheet of fabric to keep the fiber particles in place.
Until here it no problem.

Remaining is the Ventilation:
I do not know how to solve this one.
I think that any hole or the like will let the sound pass through.
Maybe a long tube lined with sound absorbing foam will do the trick.
Letting the air out / in and attenuating the sound that escapes through it.
Any advice?

Thanks,
Zilog

[[email protected]]

Remaining is the Ventilation:
I do not know how to solve this one.
I think that any hole or the like will let the sound pass through.
Maybe a long tube lined with sound absorbing foam will do the trick.
Letting the air out / in and attenuating the sound that escapes
through it. Any advice?
tHe secret is bends in the ventilation ducting, such as is
done with well designed hvac systems for commercial studios.

Consider for a moment the muffler on your car. THe gases
from your tailpipe make lots of bends going through the
muffler before exiting the pipe. tHe muffler attenuates the
sound because there is no good path for lal that sound.
Oversimplification obviously, but consider this for a bit.

THis means you'll need to either have a big bigger fan
drawing air through your chamber, and I"d think possibly
putting the fan on the output instead of the intake might be
your idea.

SOme of the acoustician types in this group will give better
advice I"m sure, but all will suggest that ventilation
doesn't take a straight path through your chamber box.




Richard webb,
Electric Spider Productions
Replace anything before the @ symbol with elspider for real
email address.



Great audio is never heard by the average person, but bad
audio is heard by everyone.

[Ben Bradley]

On Thu, 17 Aug 2006 21:00:56 +0200, Zilog wrote:

Rob Reedijk wrote:

If it's allowed to be ugly, this can be done cheap. I assume it's
temporary. Build a box in a box. Each box will have a plywood floor
and drywall walls. Fill the walls, floor and ceiling with insulation.
Try to have almost no solid contact between the two boxes. You will have
it through the floor since one must rest on the other. Use the pucks that
Scott mentioned for this and to rest the whole thing on your floor.
I would avoid the ventilation issue by making it large enough that you
can operate the amp for short periods without over-heating. You will
need to have two doors---one for each box lined up on the same side, with
a piece of insulation that you move in and out. Also, you will need
a conduit for cables. I would just put one in with enough line, mic
and power lines that you won't have to worry about it later. Make the
walls and floor thick. 8 inches? Use staggered 2x4s. Double up the
drywall for more isolation. Mass is your friend.

total cost? Couple hundred bucks.

Rob R.

The construction has a permanent character and it's solely purpose is
testing amps and speakers at their max volume.

So at least it doesn't have to be pretty. I think all the comments
Rob made still apply.

Can Fiberglass or rock wool be used for insulation?

Do you mean AS the walls, or between the sheetrock walls?
Definitely not as the walls. See "mass is your friend" above. You'd
need at least the same weight as drywall, and any porousness these
might have is a big negative. You want it airtight.

I think if drywall is used I have to isolate it with acoustical foam
sheets to avoid to much reflections. These can make the "rattling" test
unreliable.

There are two problems: One is keeping the sound from getting out,
that's the room-in-a-room/box-in-a-box construction as described
above. The other is treatment within the box for the reflections, comb
filtering and bass nodes.
I think the smaller the working space, the worse all the problems
will be: room nodes will go up into the lower midrange (the acoustic
space itself will have resonances), and heat buildup without
ventilation will be a greater problem.

Ventilation I still see as a problem.
First for the equipment if it's on for some time (30 minutes)
and secondly, if a live test is done with a guitar and amp under test.

Don't let anyone in there for a test without them wearing ear
protection. Put a warning sign on the door.

It will be very hot in there...

Will you really ever have a need to run at full volume for 30
minutes continuously? I'm thinking you can get away with a "sealed
box" with no ventilation if you run it for maybe ten minutes at a time
(or until it gets to the max temperature you think it should get -
remote temp monitoring is a $10 digital indoor/outdoor thermometer
from Target), remove the input signal but of course keep the amp
powered up, open the door and run a window fan into the doorway for a
couple minutes while you take a coffee break. This would of course
make operation inconvenient but would save on having to build
acoustically isolating ventilation.
For isolating ventilation (I'm not an expert, you better pass this
by someone who is), use a couple of the modern insulated 25-foot
heating and AC vent tubes that come compressed into about a 4-foot
box, one driven by a fan at the "outside" end for fresh air, the other
for return. Their lengths will also need to be in an acoustically
insulated volume, or perhaps go through several such volumes, making
the whole thing that much larger without increasing the working volume
inside.

As far as finding resonances and odd vibrations (though it appears
you've done this for a while and know what you're doing), "live
program material" is okay and necessary, but I'd also use a fequency
sweep. There are lots of HP 200 audio oscillators still around. Get
something with at least a 10 to 1 sweep range so you don't have to
switch bands as much, if at all. Or make a sweep CD generated with
Audition or other DAW program.


But maybe that can be solved with a microphone and monitor amp with
speakers outside the chamber.

The doors can swing the opposite way so that's solved to. (I forgot
about the doors...)
To insulate the inner box from the floor I have a box full of rubber
disks about 2 cm thick and 10 cm in diameter.
Is a pointed cone maybe a better solution to isolate the inner cabinet
from the floor; you know these thingies that are placed under turntables
or loudspeaker cabinets. Only bigger in size.

I think only if they're made of rubber or other flexible-and-lossy
substance. Steel is bad - I recall that the loudspeaker mounts are
intended to COUPLE the loudspeaker to the floor, definitely not what
you want here. The pucks/donut mounts Scott mentioned are surely what
you need.

well, it's taking form.

More reactions are welcome and very much appreciated.

Zilog

[Zilog]

Ben Bradley wrote:
On Thu, 17 Aug 2006 21:00:56 +0200, Zilog wrote:

Rob Reedijk wrote:

If it's allowed to be ugly, this can be done cheap.
Build a box in a box.
Fill the walls, floor and ceiling with insulation.
Use the pucks that Scott mentioned.
Make the walls and floor thick.
Double up the drywall for more isolation.
Mass is your friend.
Rob R.
The construction has a permanent character and it's solely purpose is
testing amps and speakers at their max volume.

So at least it doesn't have to be pretty. I think all the comments
Rob made still apply.

Yep, It's a BOX for testing, so no fancy stuff inside.

Can Fiberglass or rock wool be used for insulation?

Do you mean AS the walls, or between the sheetrock walls?
Definitely not as the walls. See "mass is your friend" above. You'd
need at least the same weight as drywall, and any porousness these
might have is a big negative. You want it airtight.

Mass indeed, and it's getting airtight.

I think if drywall is used I have to isolate it with acoustical foam
sheets to avoid to much reflections. These can make the "rattling" test
unreliable.

Will naked drywall not be a source of reflections.
As said earlier, I have to isolate it with Acoustic foam. Agreed?

Ventilation I still see as a problem.
First for the equipment if it's on for some time (30 minutes)
and secondly, if a live test is done with a guitar and amp under test.

Don't let anyone in there for a test without them wearing ear
protection. Put a warning sign on the door.

I'm the only user...
If there is another person I'll be with him all the time.
I have only two ears and I like them the way they are. So protection is
available if needed.


It will be very hot in there...

I know, I know.


Will you really ever have a need to run at full volume for 30
minutes continuously?

Yep, most of my amps run for 30 min at various power levels; some at
full power.

...run it for maybe ten minutes at a time, keep the amp powered up,
open the door and run a window fan into the doorway for a
couple minutes while you take a coffee break. This would of course
make operation inconvenient but would save on having to build
acoustically isolating ventilation.

That's a valid option, Thanks! It avoids the installation of long
isolated ducts.


As far as finding resonances and odd vibrations (though it appears
you've done this for a while and know what you're doing), "live
program material" is okay and necessary, but I'd also use a fequency
sweep. There are lots of HP 200 audio oscillators still around. Get
something with at least a 10 to 1 sweep range so you don't have to
switch bands as much, if at all. Or make a sweep CD generated with
Audition or other DAW program.

That stuf is all available and used when needed.


The pucks/donut mounts Scott mentioned are surely what you need.

Noted and will be used.

To recapitulate:

A box in a box.
Inner box in plywood. Walls are about 20cm thick.
Inside walls in drywall and covered with acoustic foam.
Space filled up with glass fiber.
The whole box is suspended from the ground and walls by rubber isolators.
A double door in the cabinet, very well isolated.
A ventilator to get the hot air out after a test run.
A microphone to monitor the amp or cabinet under test without me being
in the box.

IF there are any other recomandation or tips. I'll leave it here.
This will do the trick I believe.

Many thanks to all who gave their views and advice.
Thanks,

Zilog