tweeter selection for D'Appolito M-T-M
I plan on building my second set of speakers. First pair was 25 yrs ago with bass port tuning and crossover done all by ear, no science--funny process for an engineer like me. This year I'm going to build an inexpensive pair of d'Appolito Midwoofer-Tweeter-Midwoofer speakers using the recommended 12 db/octave crossover at 2500 hz and the 2 4-ohm midwoofers in series. Any advice on tweeter selection? I'm leaning toward a pair of 1" silk domes--Northcreek d25-065, $36/pair. I think that the -1.5 db shelf from 1.5 K to 3 K is marketing crap, but the North Creeks do appear on paper to be a good value. Is there a better tweeter option for <$50/pair?
Are their any issues with putting 2 4 ohm midwoofers in series for 8 ohm? I picked up 4 Isophon's P170/30 cheap (<$10 each delivered) on Ebay.
If this project works well, I'll build some higher end speakers. If it's crap I'm only out $100.
I'll mod the crossover if necessary
I plan to mount the crossovers externally. I'll start with the Isophon recommendation and modify with filters and attenuators or even change the order if I don't get the sound I want. I prefer to get flat Freq response from the drivers so that a simple crossover will work and I won't have to apply fixes, but if anyone ever invented the perfect driver it would take the fun out of this.
From what I've read the Isophons have a flat FR and a flat impendence curve up to 6000 hz, so the recommended crossover should be good. Now I need a tweeter with good dispersion, a flat response down to at least 1250 hz (1 octave below crossover), and a flat impedence curve. The impedence curve is the easiest thing to fix, and the dispersion is the hardest, so my priorities for tweeter selection are 1. dispersion. 2. FR. 3. impedence curve.