Building center channel speaker box using in wall speaker

R

Rick Dean

Audiophyte
Hello,
I have an extra Polk Audio Lc 265i in wall speaker. I am contemplating building a box to create a center channel speaker. Does anyone have any thoughts or feedback on going about that or just doing it, generally speaking?
 
M

Movie2099

Audioholic General
Hello,
I have an extra Polk Audio Lc 265i in wall speaker. I am contemplating building a box to create a center channel speaker. Does anyone have any thoughts or feedback on going about that or just doing it, generally speaking?
I believe you could do that. Just make sure to put some insulation inside box and sealed tight. Should sound just fine.
 
ryanosaur

ryanosaur

Audioholic Overlord
You can try it, for certain.
Now for the however: (sorry, but it's real) What you suggest likely will not work.

Speaker drivers have parameters that predicate their usage. Those designed for in-wall usage are optimized, along with the crossover, for an infinite baffle, and will have different compliance requirments than those used in a box. When putting speakers into a box, you have to take much more into consideration. The Fs and Vas of the driver, as well as the drivers Q all play important roles in matching a box to the drivers. Getting the Vb (box volume) right is one problem, designing for a ported enclosure and getting volume and port tuning to come together is another.
After getting a box optimized for the drivers, you then have to redesign the XO for the new baffle size, and also account for the BSC (Baffle Step Compensation).
This is a very light scratching of the surface.

In every previous thread where something like this has come up, I always encourage the inquisitive to learn about what actually goes into Speaker Design. It is not a plug and play hobby.

The more friendly two books for introduction are the Murphy and Weems books:

After those, the more advanced books by Alden and Dickason:

I am working my way through learning the SoundEasy Software right now and have read those books several times each. Even still, there is a lot more to learn about doing it well. I feel it is a worthy pursuit!

I hope you will take some time to learn about it, first. :D

Cheers.
 
TLS Guy

TLS Guy

Seriously, I have no life.
Hello,
I have an extra Polk Audio Lc 265i in wall speaker. I am contemplating building a box to create a center channel speaker. Does anyone have any thoughts or feedback on going about that or just doing it, generally speaking?
The problem is you do not know what size box to build. So first you need to buy the Dayton woofer tester and measure the Thiel/Small parameters of those woofers.

That will tell you if those speakers are optimally loaded by a ported box or a sealed one. Then the volume of the box can be calculated. If it requires a ported box, then the port dimensions can be calculated. You can't build any old box and expect it to work properly.

If you get the woofer tester and measure the T/S parameters then I can calculate the optimal box design for you.

The other issue is that an in wall speaker does not have a monopole/omnipole transition frequency. So an in wall speaker would be designed without baffle step compensation in the crossover. So the crossover would need modification, although you might get away with it if you place the enclosure right up against the wall..
 
R

Rick Dean

Audiophyte
You can try it, for certain.
Now for the however: (sorry, but it's real) What you suggest likely will not work.

Speaker drivers have parameters that predicate their usage. Those designed for in-wall usage are optimized, along with the crossover, for an infinite baffle, and will have different compliance requirments than those used in a box. When putting speakers into a box, you have to take much more into consideration. The Fs and Vas of the driver, as well as the drivers Q all play important roles in matching a box to the drivers. Getting the Vb (box volume) right is one problem, designing for a ported enclosure and getting volume and port tuning to come together is another.
After getting a box optimized for the drivers, you then have to redesign the XO for the new baffle size, and also account for the BSC (Baffle Step Compensation).
This is a very light scratching of the surface.

In every previous thread where something like this has come up, I always encourage the inquisitive to learn about what actually goes into Speaker Design. It is not a plug and play hobby.

The more friendly two books for introduction are the Murphy and Weems books:

After those, the more advanced books by Alden and Dickason:

I am working my way through learning the SoundEasy Software right now and have read those books several times each. Even still, there is a lot more to learn about doing it well. I feel it is a worthy pursuit!

I hope you will take some time to learn about it, first. :D

Cheers.
"So you're saying there's a chance? " :)
I know Polk sold an in wall enclosure to mount this specific speaker in. At least there is something to get a volume measurement from?...
 
R

Rick Dean

Audiophyte
"So you're saying there's a chance? " :)
I know Polk sold an in wall enclosure to mount this specific speaker in. At least there is something to get a volume measurement from?...
To follow up my last comment, I was just able to find info on that enclose and it was not a box...
 
ryanosaur

ryanosaur

Audioholic Overlord
To follow up my last comment, I was just able to find info on that enclose and it was not a box...
There's always a chance you can get lucky. :) Serendipity can also be a very cruel mistress. ;)

@TLS Guy is far more experienced than I, and we are mostly in agreement.
With the investment in the right tools, you might be able to do something with that gear... I suspect it will cost you more to do what you are talking about than to buy a proper Center Channel.
 
TLS Guy

TLS Guy

Seriously, I have no life.
To follow up my last comment, I was just able to find info on that enclose and it was not a box...
I managed to find out on the Polk forum that if you want to enclose that speaker, then the correct enclosure volume is 1 cu.ft. It is a sealed enclosure and not ported. So you need to construct a box of 1 cu.ft internal volume. I would make it of 3/4" MDF and very rigid. I would add 10% to the volume, so 1.1 cu.ft to allow for the air displaced by the drivers. The box should be filled completely with Polyfill. Do not compress the Polyfill, but make sure it fills the box completely. You will need to add speaker terminals on the back of the box.

Apparently those drivers have a very high Qts, and without an enclosure the cone excursion is excessive and they rattle. The enclosure improves them greatly and lowers system Qtc, and greatly reduces cone excursion. Make sure the box is well sealed. Good luck.
 

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