OK... I've been hinting around at this for a while. I've recently decided, to ditch my C70 Alpha III project, to instead build a modified 250Ti design...
I've decided to "go for broke", in some ways... to change the few things, I always thought were not quite to my liking in the 250Ti design...
Here's what I've come up with, as far as a driver complement is concerned:
Highs: 035TIa (naturally)
Midrange: slightly "customized" 104H-2 (treated paper cone rather than the poly cone 104H- I always liked the transient response of the treated paper cone better, as I thought it hit a good balance between the "rowdy" LE5-X variants and the "overly polite" 104H)
Midbass: 2118H. Closest thing to a 108H available. I also just plain LIKE the way 2118Hs sound... a BUNCH.
Bass: "Customized" 2235H, with a custom made "PR460"... ie, a passive radiator, made from an 18" basket, loaded with an aftermarket 2245 cone and soft spider, with a weight-adjustment bolt/nut arrangement. This PR would be mounted on the rear of the 250Ti cabinet, instead of a port...
I decided to try the 2235, due to much more ready availability WRT the LE14H-1 (those 15" frames are everywhere)... I'm thinking of using a slightly longer voice coil (possibly a 2245 coil, 1" winding length instead of 3/4"), to increase the X-max, raise the Q a bit, and raise the Mms just a bit. According to my calculations, this should wind up giving me within 1/2 dB of the same sensitivity to a LE14H-1, and a solid 29-30 Hz or so f3 point, before considering room gain. And the nice thing about the PR, is that I will be able to tune the bass rolloff, to the room...
Crossover, would be as close to a stock 250Ti, as I can do, accomodating the new drivers. I would assume I can retain the stock topology, but tune various sections to optimize them for the new drivers, using LEAP/LMS...
So far, I've got a pair of 2118 frames, a pair of LE5-10 frames (which I will custom recone as "104H-2-type" drivers), and a pair of 2225 frames and aftermarket 2235 cones to go into them. I still need 035TIa tweeters and some baskets of some sort, to build the passive radiators into. I'm hoping I can find a couple of Peavey Lowrider or Black Widow 18" frames... they should make quite good PR chassis, as dimensionally, they're very close to JBL 18" frames.
So, any comments? Yes, I know I could go with more "modern" drivers such as the 1500AL or other exotic new stuff, but I thought I would try to build them with "in the day" components... stuff that COULD have been assembled, back in the day the 250Ti was built. An alternate universe version, as it might have been...
Of course, I now need to manufacture some time, in order to get to work on these. Gee, who hasn't heard THAT story before?
Regards,
Gordon.