DXT and W4-657: TMM vs MTM

[Pablo]

Well, maybe this is a reiterative question, but I´m trying to decide about the design.

I´d like to make something mini with four TB W4-657D (measurements ) and a pair of Seas DXT, but I´m not sure about the arrangement I should pick, I mean TMM with a cascade filter or a standard MTM crossed around 1500-1600 Hz (C-C distance being 22 cm or so).

What would you choose?

Thanks for your inputs.

Pablo.

[Jed]

How much BSC (baffle step compensation) do you plan on using for your design? MMTs usually have full baffle step compensation, so that might not work well for a near wall placement. The advantage of MMT is that you really don't need as low a crossover point, so since you are going with the DXT, it probably can handle an MTM application just fine and you'll have more options for BSC.

[Pablo]

Thanks Jed for your answer. Well, you have explained perfectly some of the issues I was wondering about. This is not a near wall design, so 4-6 db are in order, that´s why I was not sure between MTM or TMM.

One more question ¿what about the dispersion pattern of an MTM crossed low enough? ¿Is it really worth the effort?

Pablo.

[Jed]

Thanks Jed for your answer. Well, you have explained perfectly some of the issues I was wondering about. This is not a near wall design, so 4-6 db are in order, that´s why I was not sure between MTM or TMM.

One more question ¿what about the dispersion pattern of an MTM crossed low enough? ¿Is it really worth the effort?

Pablo.

I guess if you are a perfectionist, then yes it is worth the effort. That said a crossover point around 1800-2000hz should be fine.

Also, the MMT or MTM format is really a personal preference choice if you are planning full bsc. MTM is theoretically a bit cheaper because you don't need the extra large coil on the lower woofer, but other than that they each have their advantages. I'm using LR4 crossovers on my MTMW right now and don't really notice the "limitations" of polar response dips etc, so theory aside, you just have to pick one and design for a nice flat response. They both will sound good in your applicaton. Now if you wanted to use a tweeter that could only cross down to 3k, I'd recommend the MMT but obviously that isn't the case.

Jed