Open baffle with drive units and xo from my SA 4744 speakers?

I’v been toying with the idea of trying open baffle with the drive units from my boxes SA (SA=Stage Accompany) speakers. my SA speakers is a two-way with a 12” woofer in br enclosure and a big ribbon mid/tweeter, xo is supposed to be 1000hz.

I would mount the 12” and ribbon mid/tweeter in an open baffle and use the excisting xo from the speaker. To help the 12” woofer with the bottom end I have a pair of Audax pr380m2 15” woofers. I have 5mH coil and 100uF cap on hand for the 15” Audax woofers xo.
For compansating the low Q of both the 12” and 15” I would use dsp to lift the low end.
How wide baffle would be ideal for the xo point I get with 5mH coil and 100uF cap on the 8 Ohm Audax Woofers? I guess there is a way of calculating how wide the baffle should be for optimaly blendeng the 12” midwoofer with the 15” audax with given xo point? I can do some messurements with dsp and compensate from there but a good starting width for the baffle would be a good start I guess?
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Total Q factor (QTS) of 0.15 for the bass driver makes it a very unlikely candidate for this application. Fs is nice and low, but overall bass perfomance is likely to be very weak.

Try googling Martin King Open Baffle for some useful background. My current prototype OB speakers use Monacor 15 inch PA drivers in a U frame with active amplification, DSP and an XO of 600hz. There's a large FR hump just below 300hz - exactly where I would expect it to be with this design.

If XO is passive, then 150 to 200hz is there or thereabouts.
I thought xmax was the limiting factor when dsp is applied and not qts of the driver? I might very well got the q, dsp and xmax backwords though.
I got inspired by OBL15 that use a low q driver (qts 0,25) and that seems to work.


The ciare woofer in the OBL15 has greater xmax then my audax woofer. But since I want to play it in parallel to my SA 12” woofer it might be OK or not?
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I'm no expert! However, xmax is clearly an issue. I was thinking about your wish to use the existing XO.

It looks like the Audax will be crossing over at around 300hz or thereabouts.

It certainly looks worth having a play as you already have the drivers. However, the probability of getting it all to work well together is probably on the low side. Some measuring equipment and a bit of software called REW might be good.