Built the Krutke/Zaph L18/27TBFC

[LNeilB]

And damn does it sound nice. Very transparent midrange, potent bass,sweet, mellow highs.

But I have to ask - is the H1224 driver SEVERELY limited in power handling below 100hz? My pair rattles like hell at moderate volume with substantial sub-100hz signals - music, not test sweeps. I'm wondering if this batch of 1224s are defective, because the Seas H571 paper driver I've been using, with half as much xmax, has never been problematic.

[JonMarsh]

I'd try checking a few things- is it ported, and are you sure your port size and tuning is correct? (nothing like an impedance sweep to know for sure)

Second, make real sure you don't have some of the driver wiring connections or any acoustical stuffing near the midwoofer cones- that one has "bit" a lot of people.

Last, as a check on the cone travel/driver integrity, remove one driver from the cabinet, and sweep with a signal generator free air at just a couple of volts drive- you should be able to see and hear excursion representative of Xmax in the lower range (20-40 Hz) without any VC rubbing or lead slapping - if you do, it's probably not the driveres. Check assembly...