Newby needs help screwing with a professional design

[martyh]

I have a pair of Apogee centaur minors that need rebuilding, the ribbons are in good shape but the cabinets are shot. Since I am going to need to build new cabinets I thought I might select better woofers to mate with the ribbon. The trouble is that the original woofers are 6 Ohm nominal and the woofers I would like to try are 8 Ohm nominal. Replacing the woofer on this speaker has been covered here a bit but I still don’t completely understand so please bear with me.

The original design has the HP and LP sections in parallel, I feel pretty confident that I can screw with online calculators and come up with a 12 dB LP section that will match the xo points from old to new but I have no idea what will happen to the relative spl between the hp and lp sections considering the different impedance.

The original crossover has a selectable resistance below the capacitance in what otherwise looks like a straight up 12dB LP section. Can someone please tell me what the resistor does and how to scale it?

Since I will need new coils anyway can I select coils with a dcr that will help me get closer to the original level of the lp section

And lastly for now, can someone point me to a free or cheap program that will let me enter the variables for the crossovers and drivers and simulate the response of the system.

Thanks in advance,
Marty

The new woofer: http://www.parts-express.com/pdf/297-302.pdf
The original woofer http://www.sea.vg/vifa/P17WG-00-06.pdf
The original XO http://www.apogeespeakers.com/projec..._crossover.pdf

[PeteMcK]

what you are proposing is really a new design, you'll need to recalc the box tuning too (assuming box size is appropriate...)

box calculator:
http://www.linearteam.dk/default.aspx?pageid=winisdpro

to match the change in level, you'll need an L pad,
(it's not the nominal resistance that's important, but the relative sensitivites - actually these drivers are close, you may be able to get away without one...)

calculators on this page should help with that and xover values:
http://ccs.exl.info/calc_cr.html#second