Hi, Troels!
Happy New Year!
Mu name is Yavor and I'm a big fan of your work, I've built two of your designs, THE sp38/13 and the Vifa PL18/XT. Both sets sounds incredible. I'm extremely happy with the results, thanks to you. I built both designs exactly to your specs. The X-over and the cabinets with the exception of the SP38/13 I made the front, rear and top panels out of double 18 mm Baltic birch.
I have a question about the SP38. The amplifier I'm using is the Phase Linear 700B, big solid power I am sure you are familiar with the 350W a side amp. I would like to get a little more power handling and possibly a little more lower bass. The question to you is this: Can I add a second Revelator to this system, let's say place the driver down low, just above the first shelf of the cabinet and let's say 6.5 mH first order separate crossover like a 3½-way set-up.
Thanks again and best regards, Yavor.

Hi, Yavor.
Thanks for you response and for the nice pics. Looks great with the solid fillets.
Making the SP38 into a kind of Ekta "G/38" is a bit tricky as we usually in a 3½-way set-up will take the major advantage of getting an overall higher system sensitivity from having the lower bass driver helping the upper bass driver in lower midrange, virtually eliminating the need for baffle step loss compensation. Current system sensitivity is around 86 dB and in a 3½-way we might easily tune the whole system around 90-91 dB like the Ekta Grande! However, this takes a complet redesign of the crossover and although easy to simulate, it takes careful fine-tuning by hand to get 3rd-4th order filters in place
Just adding a second bass driver to the exsisting system will maintain current sensitivity and most likely make the whole system too bass heavy, in particular from a 1st order filter. Next: Adding a second driver will require ~twice the cabinet volume, so new cabs required.
Best regards, Troels.