I'm real sensitive to spitting, sibilant speakers. A zobel helps when a driver has a rising FR like the FE127E. Try 8 ohm and 2.2 uF.Right now I'm trying to find a good cabinet for a pair of FE127E's I have laying around. I've looked at all of the MLTL variants, BR's and the Fostex standard DBR. Nothing is going to go below 70 Hz and max power handling will be in the 1/2 watt range -- 85dB max undistorted. The only use I can see for a "full-range" application is computer speakers, and 24x9x9" is a bit big for my computer desk. I'm thinking that the right application for this driver is as a mid-tweeter over a 10" or 12" woofer and crossed at 300 Hz or so.
The best of the lot is indeed the Fostex DBR. However, the dip at 150Hz is just hinted at in the Fostex FR plot. Running the numbers through MJK's spreadsheet shows the dip to be a very sharp 20dB hole. AT 150 Hz, that should cause notes to drop out! Anyone build the standard DBR?
Bob