Replacement driver choices for a double 12" cab,

Kevin, I have just read your first post again and I think that the Bass bins are already built, if so please ignore my last post. I must read more carefully next time.

Tony

It's a nice idea but ultimately probably causes more issues than it solves.  In these boxes the frequencies are covered easily.  Taking mine for example:

The 12" driver is capable of playing to probably 3kHz fairly cleanly (ignore the fact it'll get a bit beamy).  The compression driver and horn combo is useable down to 500Hz (although you wouldn't want to because of power handling issues).

This means that at a crossover point of 1.2kHz both drivers are capable of doing an octave either side of it, making for a very clean transition between the two.

No, the 12NDL76 in terms of parameters is closest to the 12MH32 although the neo has about double the excursion capability of the MH32.

12PE32 is a dedicated midrange driver, has a very light cone and only a 2.5"VC and ideally should only be used on mid horns from about 200Hz up.

Although saying that the 12ND710 I use in my mid-tops is a dedicated midrange driver and I use it down to 120Hz.  It does mean there is a bit of a dip in the system between 120Hz and 200Hz but since it's not unusual to put a cut in the EQ around there on most systems, you don't really notice it missing.

Kevin,

Did you see my thread about the cabs I build recently of this type?

http://www.speakerplans.com/forum/forum_posts.asp?TID=10250&KW=cha2214

The cabs have now been fitted with 18Sound 12ND710's which are incredibly efficient and will work well with high crossover points to the HF.

I'm using the currently unavailable PDC14 that you also wanted to use.  I would recommend using a larger compression driver and getting the crossover point down. 

In terms of alternative compression drivers, the 18Sound drivers are worth considering.  They are quite bright sounding and need a bit of work on the processor but that done you get a very detailed sound.  Not particularly expensive.  Also worth looking at how much some of the new B&C 1.4" drivers are, or maybe the DE610.  Definitely recommend the 18Sound 1.4" flares though.

And just to help your decision process if you want to go down the other route a DE250 on 1086XT with a single 12", crossover 2kHz ish is also very nice indeed.Again 18Sound maybe for a 12" or B&C 12NDL76.

Most of the 12" drivers I've suggested will exhibit the roll off on the low end.  This is just due to their high midband efficiency and the very strong magnets used to acheive it.I find a low shelf starting about 160Hz and lifting the low end by 3-4dB tends to flatten it out.The other option is to use a slight overlap with the subs.

Oh, and one twin 12" mid top will keep up with about 3 18" bass bins!

Tiny word of warning about the reflex ports in your tops. If you cut them like that the port piece (assuming you need to extend it beyond the baffle depth? - if not ignore all this!) ends up being mightily complicated to cut as its got no 90' angles in it. It has to follow the trap angle to keep the same dimensions throughout the port. You also have to make an angled cut into the baffle or else the port will have a slight constriction at the very end.

Ill show you a picture of what i mean when we sort out the net at home, just moved house ya see :)

Alf