HT centre: flat or angled front?

BlackCatSound · 3rd August 2006, 10:10 PM

In an attempt to reduce 'spare driver mountain' I'm planning to use a pair of 8" Volt BM220.8s and a Morel USA MDT-33 to make a new centre speaker in the usual horizontal MTM config.

Now the $64k question is should I have a flat front (all 3 drivers in the same plane) or should I angle the mids outwards slightly?

Basically ___ or \_/

I'm glad I have a projector as this centre will probably suck the picture off a CRT at 10 paces

Andy G · 3rd August 2006, 10:48 PM

you would do far better if you can do a w t/m w set-up.

ie use the 8's up to around 300-400, then have a tweeter over say a 4" mid in the centre. easier flat construction too.

BlackCatSound · 4th August 2006, 09:14 AM

I thought about Mt/mM as I have some audax HM100Z0 4" mids but the Volt 8" plays clean to 3k. Beaming will happen but is that an issue with a centre? (plus the fact the MTM changes the dispersion anyway)

pinkmouse · 4th August 2006, 10:05 AM

You need to do some of axis measurements of FR on the volts, and see at what angle they roll start rolling off. For the sake of argument, say you've got up to 10 degrees to play with before your 3K response gets compromised, you then use that 10 degree off axis measurement to calculate your crossover rather than the straight ahead FR. Does that make sense?

BlackCatSound · 4th August 2006, 02:17 PM

I forsee some time spent with the table saw and router making some test boxes

pinkmouse · 4th August 2006, 02:45 PM

Quote:

Originally posted by BlackCatSound
I forsee some time spent with the table saw and router making some test boxes

Bodge it!

You're only really worried about the crossover frequencies, so just get a couple of,say, 1m squares of chipboard, hinge them together in the middle with gaffa, then mount the drivers on them. At the frequencies of interest, back wave isn't a problem, you're only looking at it around the crossover area. If you wanted to get really technical, you could put another strip in the middle with the tweeter on it, then just flex away!

BlackCatSound · 4th August 2006, 03:21 PM

Really should get my measurement mic built, I've only been working on the PCB for 6 months

BlackCatSound · 10th November 2006, 02:21 PM

Well its taken 2 months to get the last driver from Volt but its worth the wait

Please ignore the quality of the cut'n'shut box or the fact the drivers are slightly squif. I'm not shinobiwan

I'm cheating and running active so I can tweak the crossover settings easily.

ShinOBIWAN · 10th November 2006, 05:52 PM

'Life's Good' - that's oh so poignant when there's 2xVolts and Audax's best mid in the same shot.

ShinOBIWAN · 10th November 2006, 05:56 PM

Quote:

Originally posted by BlackCatSound
Please ignore the quality of the cut'n'shut box or the fact the drivers are slightly squif. I'm not shinobiwan

Don't blame your laziness on me!

3rd August 2006, 10:10 PM	#1
BlackCatSound diyAudio Member Join Date: Oct 2004	HT centre: flat or angled front? In an attempt to reduce 'spare driver mountain' I'm planning to use a pair of 8" Volt BM220.8s and a Morel USA MDT-33 to make a new centre speaker in the usual horizontal MTM config. Now the $64k question is should I have a flat front (all 3 drivers in the same plane) or should I angle the mids outwards slightly? Basically ___ or \_/ I'm glad I have a projector as this centre will probably suck the picture off a CRT at 10 paces

4th August 2006, 10:05 AM	#4
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	You need to do some of axis measurements of FR on the volts, and see at what angle they roll start rolling off. For the sake of argument, say you've got up to 10 degrees to play with before your 3K response gets compromised, you then use that 10 degree off axis measurement to calculate your crossover rather than the straight ahead FR. Does that make sense? __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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3rd August 2006, 10:48 PM	#2
Andy G diyAudio Member Join Date: Apr 2002 Location: Newcastle, Australia	you would do far better if you can do a w t/m w set-up. ie use the 8's up to around 300-400, then have a tweeter over say a 4" mid in the centre. easier flat construction too.

4th August 2006, 09:14 AM	#3
BlackCatSound diyAudio Member Join Date: Oct 2004	I thought about Mt/mM as I have some audax HM100Z0 4" mids but the Volt 8" plays clean to 3k. Beaming will happen but is that an issue with a centre? (plus the fact the MTM changes the dispersion anyway)

4th August 2006, 02:17 PM	#5
BlackCatSound diyAudio Member Join Date: Oct 2004	I forsee some time spent with the table saw and router making some test boxes

4th August 2006, 03:21 PM	#7
BlackCatSound diyAudio Member Join Date: Oct 2004	Really should get my measurement mic built, I've only been working on the PCB for 6 months

10th November 2006, 02:21 PM	#8
BlackCatSound diyAudio Member Join Date: Oct 2004	Well its taken 2 months to get the last driver from Volt but its worth the wait Please ignore the quality of the cut'n'shut box or the fact the drivers are slightly squif. I'm not shinobiwan I'm cheating and running active so I can tweak the crossover settings easily.

10th November 2006, 05:52 PM	#9
ShinOBIWAN diyAudio Member Join Date: Feb 2004 Location: UK	'Life's Good' - that's oh so poignant when there's 2xVolts and Audax's best mid in the same shot.

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