Tweet/mid flush mounting

Puggie · 17th January 2005, 09:14 AM

I'm planning a D'Appolito style floorstander, I now have my drivers, Morel MDT-20 (ceramic magnet soft dome tweet) and Audax AP100Z0 (4.5" aerogel midbass). I'm going for a long thin ported box which looks fine (I've un the model in Bass Box Pro and MJK's MLQWT mathcad model and get very similar results so I'm happy with that).

My question is with the mid/tweet mounting I need to flush mount the tweet to reduce reflections, that is not a problem, I'm intending to cross them over about 2kHz (4th order LR low pass and 2nd order Butterworth or LR highpass). How far apart do the mids want to be bearing in mind the tweet has a 4" diameter face plate? I was planning on flush mounting the tweet and mounting the mids on the surface with the edge of the mids overlapping the tweet. Now this gives me a nice close pair of mids (5.5-6" apart) but will the edge of the mids which is sat on the tweeter face plate cause difraction/reflection problems for the tweet? My main reason to flush mount the tweet and surface mount the mids is to time-align the cones better and IMHO it looks good.

What are peoples opinions?

HeatMiser · 17th January 2005, 03:37 PM

Zaph has done some measuring of the effects of flush mounting, and there are some graphs that cover the case of overlapping drivers so you can get an idea of the effects. It doesn't look too bad really.

http://home.new.rr.com/zaph/audio/mtg-surface.html

That Audax driver has a flange just over .25 inches thick (7 mm) by the way, according the the Audax spec sheet..

As to how critical the spacing is, I've heard it said that if you keep it under one wavelength you're generally fine. I don't know if that's true or not, but that's what some people say. 2000 Hz gives you 6.75" to work with.

There are almost certainly folks on this board with more information and different opinions though.

Puggie · 17th January 2005, 04:53 PM

Thanks for the link,

IMHO looks like the gains from aligning the voicecoils and getting the drivers close together will outweigh the possible side effects. Either way the drivers in question are hardly the height of high fidelity, I'm sure they will be fine

anyone else care to comment

BillFitzmaurice · 17th January 2005, 06:11 PM

The 1 wavelength assumption is correct but not carved in stone; D'Appolito exceeded it himself in his Thor TL. To be safe just pack them as tight as you can.

17th January 2005, 09:14 AM	#1
Puggie diyAudio Member Join Date: Oct 2004	Tweet/mid flush mounting I'm planning a D'Appolito style floorstander, I now have my drivers, Morel MDT-20 (ceramic magnet soft dome tweet) and Audax AP100Z0 (4.5" aerogel midbass). I'm going for a long thin ported box which looks fine (I've un the model in Bass Box Pro and MJK's MLQWT mathcad model and get very similar results so I'm happy with that). My question is with the mid/tweet mounting I need to flush mount the tweet to reduce reflections, that is not a problem, I'm intending to cross them over about 2kHz (4th order LR low pass and 2nd order Butterworth or LR highpass). How far apart do the mids want to be bearing in mind the tweet has a 4" diameter face plate? I was planning on flush mounting the tweet and mounting the mids on the surface with the edge of the mids overlapping the tweet. Now this gives me a nice close pair of mids (5.5-6" apart) but will the edge of the mids which is sat on the tweeter face plate cause difraction/reflection problems for the tweet? My main reason to flush mount the tweet and surface mount the mids is to time-align the cones better and IMHO it looks good. What are peoples opinions?

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17th January 2005, 03:37 PM	#2
HeatMiser diyAudio Member Join Date: May 2003 Location: Washington State, USA	Zaph has done some measuring of the effects of flush mounting, and there are some graphs that cover the case of overlapping drivers so you can get an idea of the effects. It doesn't look too bad really. http://home.new.rr.com/zaph/audio/mtg-surface.html That Audax driver has a flange just over .25 inches thick (7 mm) by the way, according the the Audax spec sheet.. As to how critical the spacing is, I've heard it said that if you keep it under one wavelength you're generally fine. I don't know if that's true or not, but that's what some people say. 2000 Hz gives you 6.75" to work with. There are almost certainly folks on this board with more information and different opinions though.

17th January 2005, 04:53 PM	#3
Puggie diyAudio Member Join Date: Oct 2004	Thanks for the link, IMHO looks like the gains from aligning the voicecoils and getting the drivers close together will outweigh the possible side effects. Either way the drivers in question are hardly the height of high fidelity, I'm sure they will be fine anyone else care to comment

17th January 2005, 06:11 PM	#4
BillFitzmaurice Banned Join Date: May 2004 Location: New Hampshire	The 1 wavelength assumption is correct but not carved in stone; D'Appolito exceeded it himself in his Thor TL. To be safe just pack them as tight as you can.

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