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madam View Drop Down
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    Posted: 28 December 2021 at 5:25pm
Hi,

I have a pair of B&C 12CXN88 drivers. 
They are custom made versions made for Martin Audio Xe300 stage monitors, with the special waveguide.

I would like to build a pair of fron speakers from them.

No idea of box design, so any help is highly appreciated.

Regards,
Adam


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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2021 at 6:02pm
If they’ve had modifications made, you’d do well to setup a simple test jig for measuring Thiele-Small parameters before attempting any box design. REW has a guide in the manual, and you only need some bits of wire and a 1K resistor.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote madam Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2021 at 6:58pm
Its just a few gramms on the woofer from a paper waveguide.
Most likely to have a different dispersion.

I could measure the woofer part, but no way to measure the coax tweeter anyway.
I guess the OG driver parameters could result a pretty close result to the optimal box
And would use it as a front "tophat" with a subwoofer, so would be crossed about 100Hz.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2021 at 9:13pm
Originally posted by madam madam wrote:


I guess the OG driver parameters could result a pretty close result to the optimal box


Probably not, given that you’ll need to make a passive or active crossover that maintains consistent coverage through the transition region.

For the sake of half an hour’s effort, you’d have a lot more useful information for the choice of cabinet and port volumes.

If it has the extra ‘cheeks’ then you’d be best off downloading the GLL balloon data for the LE equivalent cabinet, and paying attention to the HF dispersion and response. The LE can be run biamp, I think, but there is a passive network inside so this must also be considered.

You could even trace this data using screenshots and the tools within VituixCAD. Which would also let you consider baffle diffraction and design a network to ensure decent listening window response.

Otherwise, if you just want a ‘lazy’ option rather than designing something, then the external box dimensions for the LE cabinet including port size are easily available via the drawings Martin provide.

Edited by toastyghost - 28 December 2021 at 9:14pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote madam Quote  Post ReplyReply Direct Link To This Post Posted: 29 December 2021 at 9:19pm
Maybe I shoud just sell these new speakers instead.
Anyone?

If its boxed.... its like 3000€, with a MA badge.
The crossover costs like 100 € from MA (SCOS00169 )
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 29 December 2021 at 9:37pm
You’ll need to do the same things for any other coaxial driver or combination of ported woofer and HF source, if you want a good response using a passive filter network.
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