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Old 31st July 2010, 01:02 AM   #1
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Default Waveguide loaded MT dipole?

I'm wondering what the OB/Dipole guys think of these loaded with a 6.5" OB mid driver and a 1" CD up top

Click the image to open in full size.

For size reference sake, the panel is 16" wide and is part of a QSC theater speaker system. It normally uses a closed back 6.5" mid but we all know how crappy those are. The 1" CD driver used is from celestion. Here's the measured response of it mounted in these...

http://sites.google.com/site/driverv...ression-driver

I have no idea what an OB mid driver such as the B&C 6MD38 looks like horn loaded but i can't help but wonder???

Please let me know if i'm outta my mind or is it worth a try?

Last edited by mayhem13; 31st July 2010 at 01:11 AM.
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Old 1st August 2010, 12:48 AM   #2
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At a glance this doesn't really make sense as an open baffle. It's kind of the reverse of a U-baffle, so there could be a cardioid response facing the wrong way. That would mean it's unusually directional, with a very small sweet spot. It's also a large baffle for the midrange, which (as John K keeps trying to tell people) could result in nulls that can't be equalized, starting an octave above the baffle peak. That peak would be pretty low in this case.

On the other hand it could be an interesting experiment if you're moved to try it.

Of course if you abandoned the idea of OB and built a box behind this thing, it should be nice and loud with that B&C midrange. The width would suggest adding a bass cabinet below with a 15".

Last edited by thomasjefferson; 1st August 2010 at 12:51 AM.
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Old 1st August 2010, 01:12 AM   #3
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Quote:
Originally Posted by thomasjefferson View Post
... It's kind of the reverse of a U-baffle, so there could be a cardioid response facing the wrong way.

...
I guess not.

Horn (WG) in front is loading the driver and forming a restricted space, so several dB of 'gain' (within a certain bandwidth) can be obtained here. Simply put, it'd be louder in front.

It's just like an Edgar mid horn - no back chamber, just leaving the driver open-backed.

I also use my Oris horn this way. It's indeed obvious louder in front than back. I can't measure and make sure what the polar response actually is. By very rough observations by ears (among messy room reflections), I guess it might be sort of an asymetric dipole (or is there such thing?) - a figure 8 with larger lobe in front and smaller in the back.

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Old 1st August 2010, 03:42 AM   #4
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In other words, put it in a box and revel with the directivity then?
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Old 2nd August 2010, 07:02 AM   #5
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Formidable Fostex Front Horn
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Old 2nd August 2010, 07:43 AM   #6
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Dipole? No - it wont be a proper dipole, as the rear and front radiation will be very very different. Better use as closed box for this I think, and get much better control over the radiation pattern than leaving the back open.
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Old 2nd August 2010, 08:50 AM   #7
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How about using 2 of them back to back?
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Old 2nd August 2010, 10:59 AM   #8
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That wont work for the tweeter - its a compression driver.
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Old 2nd August 2010, 02:05 PM   #9
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A bit off-topic but here is a dipole with "horns" on both sides:

Forsman AS - VSS5

I have heard them once at a demo - liked it but the bass was a bit difuse (probably due to speakers located too near frontwall - only 50-60 cm distance)
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Old 3rd August 2010, 03:08 AM   #10
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Originally Posted by StigErik View Post
Dipole? No - it wont be a proper dipole, as the rear and front radiation will be very very different. Better use as closed box for this I think, and get much better control over the radiation pattern than leaving the back open.
Thanks Stig.....that's what i'm thinking also.....topping a 15" hi eff pro woofer.

I would think i should look for a 6.5" that has a natural rising response as i suspect the horn loading will dramatically boost the the 300-1khz range?.....i mean why waste that efficiency right?
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