DL86, you would have to understand as you dig farther down into infrasonics, even with very accurate compensation values for your mic in REW, the computer/notebook input electronics would probably be inaccurate. But seriously I don't think anyone needs much accuracy over there that low down, as long as you know you are getting output.... LOL!
You have to be careful with the pro stuff. I have a pair of Beyma 10MW/Nd vented, whenever I exceed 100dB/1m for 1 cab and 105dB/1m for the other (approx) I'd get some funny rattling distortion kinda sound suddenly, its as if the magnets inside are loose and rattling with some midrange kinda noise. I'm not sure what is happening, but I will try to put some superglue on the individual neodymium magnets and see (i can't close the vents between the magnets as they serve as cooling holes). Can't be both drivers are faulty at the same time, I believe its a design flaw. As you can see its not a 100% hit all the time even with EXPENSIVE drivers.
I'm not letting that bother me, since I am enjoying the Lambda 15s so much that the Beymas don't get any play time at all.
But one fine day when I am free I shall fix it, so that at least the $$$ is not wasted (can't sell DIY for nuts over here in SG). Trying to earn as much money as possible while the chance/opportunity is still available!
The Beyma CP380/M is a very good driver, you can try that.
Or use the Neo version the 385Nd, but seriously i believe they are around the same. Do it active with EQ, no issue with the funky impedance peaks and whatever different horn compensation needed for whatever horn flare you choose. You should try the Lambda TD drivers from aespeakers, they are very very good and most importantly don't cost much. Do a search, they are used all over the place in many designs over here and DIYA.