d’Appolito / ribbon tweeter question

[Wseaton]

Something that I've always wondered about MTM/d’Appolito configurations is why you don't see ribbon/planar tweeters coupled with them more often.

Pardon the dumb question, but given the default horizontal/vertical characteristics of a typical MTM design you'd think a ribbon/planar tweeter, with their particular horizontal/verical dispersion characteristics, would be a match made in heaven. Still, I don't recall every seeing a commercial or reputed DIY design using such a configuration.

Is this still a personal preference in regards to ribbon/planar tweeters, or does it have to do with the low crossover limits of ribbon/planar tweeters not conducive to a MTM design?

[Cal Weldon]

RAW Acoustics uses them

http://www.rawacoustics.com/

[Wseaton]

Well slap me 'silly' and call me 'billy'.....

Wasn't planning on building any speakers.....but damn, that HT2 kit looks mighty impressive. If there are any 'ears' out there who could offer comments on that MTM kit, I'd appreciate hearing from them.

[spock]

Check over @ The Audio Circles. Raw has their own forum there, and there are a couple of customer reviews/comments within.

[Wseaton]

Thanks for the tip.

So, I take it that planar/ribbons and MTM designs are a good thing, but we just don't tell anybody our secrets ?

:-)

[pinkmouse]

I would be a little concerned about the size of most ribbons causing lobing issues with the two midrange drivers.

[Landroval]

I think there are a few good explanations why MTM ribbons are not a good way to go.

1) Ribbons are usually quite tall (3"-5"+borders) so the midranges will be quite far away from each other which will result in bad imaging ja combing in the vertical axis. Something like LCY or BG Neo3 will do much better than Fountek NeoCd2.0.

2) Ribbons usually need to be crossed higher than dome tweeters, so the combing and imaging will be much worse. Very steep crossover slopes will help with this, but there's no way to cross a cheap ribbon much under 3kHz and still get low distortion. Also the steep crossovers have some weaknesses compared to basic ~2nd order stuff.

I like the RAW HT1 and HT3, but I wonder if the HT2 can give anything more and not have some major drawbacks of the high crossover MTM design.

[Wseaton]

The HT speakers use WR125S drivers, which from what I'm reading are nearly full range.

This would tell me the WR125S is crossed over higher than normal, and hence couple well with the ribbon given it's specific problems with a vanilla 2500hz crossover and slope.

Speculation at least.

[Landroval]

Yes, the WR125 + ribbon MT is a good combo because the crossover point can be much higher than with a basic metal cone woofer. The point is that MTM needs to have low crossover point to work well, so WR125 MTM is only making things worse.

[chainenoble]

here's a mtm i just finished.i used the llcy 110 crossed at 2500.it works very well.it's a big improvement over the Seas Excel Millennium tweeter.