Going From MT To MTM...

[foxfire3]

Hi All,
I have a 2-way bookshelf design that I'm pleased with the sound of.
I'm using a 2nd order on both the woofer and tweeter.

If I were to use the same drivers for a MTM configuration, can I just cut the woofer inductor's size in half(for (2) 8 ohm woofers in parallel) and double the capacitance going to both woofers or is more complex than this?.
Would the tweeter's crossover values remain almost the same with exception of the L-pad?

Also, I keep reading about "lobing" issues when it comes to mtm designs.
Can someone please elaborate about "lobing" and what can be done to keep it to a minimum?

Thank you...

[kop]

Because of phase, CTC spacing and lobing issues the two are different animals. If you go from TM to MTM you'll need to do a completely new crossover. You will likely have to change the crossover point and slope(s). Lobing refers to the shape of the speaker's radiation pattern. Different driver configurations and crossover combinations produce strikingly unique sonic qualities. If you want to enjoy the benefits of a properly executed D'Apolitto configuration, you shouldn't think of this as simply adding a woofer.

[foxfire3]

Thanks kop...though I've never thought of a mtm design as "just simply adding another woofer".
I came up with the suggested crossover changes from the Usher projects that Dr. D'Appolito designed for PE a while back.
His changes for going to a mtm from a mt were almost spot on with what I asked about above.
It could be that it just happened to work out that way with the Ushers he was using.
I don't know...that's why I'm asking.

Thank you...

[Chris Roemer]

Thanks kop...though I've never thought of a mtm design as "just simply adding another woofer".
I came up with the suggested crossover changes from the Usher projects that Dr. D'Appolito designed for PE a while back.
His changes for going to a mtm from a mt were almost spot on with what I asked about above.
It could be that it just happened to work out that way with the Ushers he was using.
I don't know...that's why I'm asking.

Thank you...

Well . . . , I . . . uh.

I've done that too! If your TM was well designed (not too high of an Fc - crosspoint), and you're not trying to lay it down sideways for a center channel, then you CAN get really close to a workable XO (when parallelling two 8 ohm drivers, from the TM) by doubling cap values, and halving inductors and resistors. The Fc for the tweeter should remain the same, you should only have to "unpad" it by about 6dB.

Chris