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how do in wall speakers deal with inconsistent 'cabinet' volume?

TonyJZX

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there's a fair bIt of inwall kits available pretty cheap where i am

a question i have is that people will install them between wall studs and in ceilings and you can have infinite volume and maybe a very small wall cavity

so how can they expect a consistent sound?

and they will claim 50-20,000 hz but how can you guarantee '50 hz' when you cant guarantee a fixed volume and no bass reflex port???

also this comes back to my point in that surely the manufacturer might specify a 'volume' so the speaker can be placed into a cavity made of cheap chipboard or osb board so that the volume requirement is met.... ie. installer can roughly measure a volume before fixing?

or is that random-ness accounted for so that the sound is sort of randomised as 'close enough'?
 

alex-z

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Some of them have plastic shells which act as an air volume for the woofer. These models tend to perform poorly, causing a mid-bass bump and potential rattles.

Open back models generally perform better, because even a small wall cavity usually has an air volume several times greater than the volume equivalent compliance of the woofer. A wall which is filled with insulation still contributes to the air volume at low frequencies. As the air volume grows, the QTC of the speaker will change, but that is not a bad thing. The rolloff stays predictable and easy to integrate with subwoofers.

As a general rule of thumb, the focus of in-wall speaker installation should be that the baffle cannot resonate. Double layer drywall with green glue is a good example. If a resonance is present, it will show up sharply on measurements, because the large baffle size efficiently transmits them. Building a cavity for the speaker from plywood or OSB could easily worsen the sound, if you introduce resonances through improper bracing or damping.

Manufacturer frequency response claims are worthless, always have been. Unless a manufacturer provides a fixed dB number and test condition, you have no way of estimating actual performance. For example, +/-3dB is worthless. 6dB is a huge amount of variance in both measured and perceived acoustic output.
 

NiagaraPete

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there's a fair bIt of inwall kits available pretty cheap where i am

a question i have is that people will install them between wall studs and in ceilings and you can have infinite volume and maybe a very small wall cavity

so how can they expect a consistent sound?

and they will claim 50-20,000 hz but how can you guarantee '50 hz' when you cant guarantee a fixed volume and no bass reflex port???

also this comes back to my point in that surely the manufacturer might specify a 'volume' so the speaker can be placed into a cavity made of cheap chipboard or osb board so that the volume requirement is met.... ie. installer can roughly measure a volume before fixing?

or is that random-ness accounted for so that the sound is sort of randomised as 'close enough'?
Here's one that is not cheap but has pretty good specs.

 

DVDdoug

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a question i have is that people will install them between wall studs and in ceilings and you can have infinite volume and maybe a very small wall cavity
You're right! Some in-wall and in-ceiling speakers have a cabinet but since it's usually a small cabinet I wouldn't expect 50Hz.

also this comes back to my point in that surely the manufacturer might specify a 'volume'
I don't think they usually publish the Thiele/Small parameters for in-wall speakers. But there was to measure them, once you have the speaker in-hand.
 
OP
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TonyJZX

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I thank people for replying... this whole arena is a bit of a dark art.

If you google around you will find 'ceiling speaker boxes'... in that yes, they realise there's a need for fixed volume there.

I think the wall studs install falls into the 'close enough' category. I think I might buy a pair and inwalls and experiment with boxes before i cut into my walls.

WHere I am there's a heap of cheap inwall electronics like touchpads and digital amps... seems like less people want to indulge in fixed installs when the economy aint so good.
 

alex-z

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I thank people for replying... this whole arena is a bit of a dark art.

If you google around you will find 'ceiling speaker boxes'... in that yes, they realise there's a need for fixed volume there.

I think the wall studs install falls into the 'close enough' category. I think I might buy a pair and inwalls and experiment with boxes before i cut into my walls.

WHere I am there's a heap of cheap inwall electronics like touchpads and digital amps... seems like less people want to indulge in fixed installs when the economy aint so good.

Those backing boxes you see for ceiling speakers are to reduce noise leakage. In a properly built room + insulated attic, you shouldn't need or want to use backing boxes. Especially if you don't know the T/S parameters of the woofer involved, some are simply not suited for use in small sealed applications.

In-wall touch screens and amps I steer people away from when doing consulting jobs. Inevitably, they become outdated and then you are talking about patching drywall to remove them. A small rack mount setup makes more sense in the long term.
 

muskrat

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The space inside a 2x4 wall is 2.7 cubic feet. This is for a standard wall. An exterior wall might be 2x6 so even larger. This is plenty of room for most 12" woofers and most in wall speakers are smaller, even subs. So woofers should be chosen to operate in free air, no back pressure from the air space. There are negatives to in wall speakers but positives too. No baffle edge diffraction for instance. There is no reason a well designed in wall speaker can't sound excellent in the right room. Just build the rest of your house around that perfect room.
 

Mr. Widget

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there's a fair bIt of inwall kits available pretty cheap where i am

a question i have is that people will install them between wall studs and in ceilings and you can have infinite volume and maybe a very small wall cavity

so how can they expect a consistent sound?

and they will claim 50-20,000 hz but how can you guarantee '50 hz' when you cant guarantee a fixed volume and no bass reflex port???

also this comes back to my point in that surely the manufacturer might specify a 'volume' so the speaker can be placed into a cavity made of cheap chipboard or osb board so that the volume requirement is met.... ie. installer can roughly measure a volume before fixing?

or is that random-ness accounted for so that the sound is sort of randomised as 'close enough'?
Most in-wall and in-ceiling systems are designed to be "infinite baffle" designs. They are definitely not acoustic suspension designed where you need a defined restricted volume to provide an "air spring", and they are not ported where you need a defined volume for your tuned helmhotz resonator. For the most part they do not sound as good as fairly average in room enclosure based speakers.

There are exceptions to the rule, but they are not the typical in-wall units that most people install. There are a few in-wall and in-ceiling speakers with ported back boxes, but typically they are quite small and not great performers. There are also some speakers with bandpass woofers incorporated in their enclosures, but these are fairly costly and intended for in-ceiling installations due to depth.
 
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