# Building In Ceiling Speaker Enclosures



## Italianwinelover

Hello new friends,
I look to you for guidance...
I am getting ready to install all of my in wall speakers for my 7.1 system. I bought all Polk Audio LCi series speakers for my setup. After bouncing around on the Polk Audio forum, I have decided to place my rears(Lc65i's) as well as my surrounds(LC80FX's) in my ceiling as one of my walls is an exterior wall and don't want to deal with vapor barrier issues. Anyway, for a Dr. Evil sum of money, Polk sells enclosures for those speakers. My ceiling has an attic above it so I am able to access the area, easily for install. I would like to build enclosures for the speakers as Polk does highly recommend enclosures to acheive better sound. Could you please lead me down the right path for starting the proccess...I spoke with a Polk Service person on the phone but he was whipping technical data at me like throwing stars in a ninja nightmare. Unscathed but a little confused I left the conversation knowing I need to build a box of dense material and that it needs to be the proper cubic feet of volume per driver, sealed and properly mounted. 

Help...:rubeyes:


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## Italianwinelover

After more reading today, I did find a, what I assume to be a discontinued enclosure (since Polk doesn't advertise it on their site) that was a different style (more cubical in shape compared to their elongated in wall style they are using currently). It had the dimensions of the exterior listed. Is there a method you would suggest to calculate the volume that I could use in conjunction with the exterior dimensions? When calculating, what do I need for driver information? Just the driver size? Are tweeters included in that calculation? My LC80FX has an 8" driver. The LC65i's have a 6.5" driver. Could I use the same MDF built box with just a different cutout for the two different styles of speakers?


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## fbov

The right path for starting, as a DIYer, is box simulation software. If you really are in the dark as to how to calculate internal volume from external dimensions, I may not be doing you a service by telling you about it. 

http://audio.claub.net/software/kougaard/ubmodel.html
Download Unibox, assuming you have access to Excel, as it's just a spreadsheet for calculating driver response in various types of boxes. Charlie Laub has done a good job of explaining it. but regardless, you need something called Thiele-Small (T/S) parameters for your drivers. Polk should have that data on their spec sheet. 

Any box improves on infinite baffle performance. Unibox allows you to predict the result, depending on what kind of box you build - sealed is the simplest. The only hard and fast requirement is that you control leaks in a sealed box, as they can whistle. In general, as long as you give the larger driver clearance to the back, any dimensional combination works. 

You will have to do the math:
- L x W x D for external volume using external dimensions
- l x w x d for internal volume using internal dimensions
- internal dimensions (l, d, w) = outside dimensions (L, D, W) - 2 x wall thickness. 

Note that depending how you join the panels, you'll need to cut some panels to internal dims, others to external dimensions. 

You need to find the stud spacing so the box fits between then. That's W. You need the target box volume, based on Unibox simulations preferrably, giving you l x d (interrnal cross-sectional area). Make "d" 2x the driver depth (cone to magnet) and you have your box dimensions. 

Then cut a hole for mounting the driver and you're ready to assemble. Best practice requires you to add a couple internal cross braces between the large panels, to control box vibration. 

The one thing I'm not clear on is the interface between finished ceiling and a speaker in a box. You don't want to use ceiling sheetrock as a box wall - too floppy. You don't want to recess the driver into the ceiling, either. Perhaps your driver mounting addresses this issue, as the speakers want to be flush when you're done. 

HAve fun,
Frank


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## bambino

If it were me i would just try to get as best to close as possible with size. for the Baffle or sheetrock side i would glue in some 1/2" or 3/4" wood cut to size for install then add your sides and top. By the way for calculating your box size volume do WxHxD=1728 (1cu.ft.).:T


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## Italianwinelover

Thank you Frank! That helps a lot! I have a friend who is a very accomplished woodworker and I am going to get him on board to help me in the process. Should be fun!


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