# Rescued some KEF in wall drivers - box size?



## DeuceTrinal (May 7, 2012)

I rescued a pair of KEF coaxial driver/crossover setups from the trash pile. They came out of a pair of Ci200QT motorized in-ceiling speakers. 8" woofer with a 1" coaxial tweeter, 6 ohm impedance, 88db sensitivity, xover at 2.5kHz (seems high for an 8" driver?)

I want to throw them in a box and see if they are good enough to use or give to a friend. I'm really not sure what kind of volume I should be putting them in though. They are designed for in-ceiling applications, where they would typically be in air spaces ranging from 1-2 feet^3 to fully IB. They originally had a back box that swung them down from the ceiling, but it had a large (1"x 7") vent directly to the back space, with a very fine mesh screen over it. It didn't seem to be aperiodic though, unless it only provided a very low amount of resistance. I think it ensured they were IB or close to it. 

I'm not expecting super hifi here, just usable sound. Two speakers plus an old beater 2ch receiver makes a nice ipod bookshelf system for friends that want to add sound to rooms, and I like to do that for them.

I'm inclined to think I'll need a big volume, but I really don't know where to start. I assume sealed for simplicity, as I don't know any specs for these speakers for winisd or anything. 

Any suggestions?


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## robbo266317 (Sep 22, 2008)

Can you see any identifying numbers on the drivers themselves?
If not then build the biggest box you are happy with and see how they sound.


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## DeuceTrinal (May 7, 2012)

Stamped in white on the back of the woofer cone is:
2020-0303
0226.02.060
Stamped on the magnet is 270307
Sticker on the magnet has barcode and L1B 3011108853 and L1B 301108796 (each speaker), I assume those are KEF serial numbers. 

I didn't find anything obvious on google.


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## robbo266317 (Sep 22, 2008)

Yep, I guess you will just have to try it and see what results you get.
I know you can measure Thiele-Small parameters but I have never done it.


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## fusseli (May 1, 2007)

I would think a large sealed box would be the best bet.... Adding an aperiodic vent couldn't hurt. The bass and midbass may be lacking, but they will certainly make sound.

If you could measure T/S params, you could design a box that would work best.

Care to share a picture of them?


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## DeuceTrinal (May 7, 2012)

But is "large" 1 cubic foot? 3? More? 
I suppose I'd only really need to measure the t/s of the woofer itself, as the rest of the system is already engineered. I don't currently have that capability, so not immediately. 

Pics as requested - they still have the square baffle on them that attached them to the motorized back box.


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## fusseli (May 1, 2007)

Ya I'd say 1-2cuft is pretty large for a driver of that size.. until you can measure T/S do you have a test box or something? If these are gifts, maybe large boxes aren't going to be the best...


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## GranteedEV (Aug 8, 2010)

DeuceTrinal said:


> I suppose I'd only really need to measure the t/s of the woofer itself, as the rest of the system is already engineered. I don't currently have that capability, so not immediately.


You will also want a contour/EQ filter in the lower midrange as the built in crossover will not account for baffle step losses (where the finite dimensions of the front of the box don't reflect large frequencies the way a ""infinite"" ceiling or wall would.


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## DeuceTrinal (May 7, 2012)

I'm not sure about that. These speakers are designed to drop down from the ceiling and face the listener when in use. They wouldn't have the typical "infinite" baffle a normal in-wall speaker has. Here's a picture of them showing them stored and deployed:


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## fusseli (May 1, 2007)

Even swinging out like that I'm guessing it still is open to the air space behind. It's also so close to the ceiling still that I'm guessing the original Xover doesn't account for any BSC. You can experiment and see how it sounds in different boxes, but to "get it right" putting them into boxes you need to measure T/S (to design your box) and even measure FR (to see what contour/BSC you need). A simple RL shelf is probably enough, you can add it in series before the speaker terminals. Here's a calculator to get you in the ball park. Again, the best way would be to measure FR and simulate, but it will definitely sound better with some compensation than it would with none.


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