Waveguide loaded MT dipole?

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mayhem13

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Joined 2008
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

HPIM1006.jpg


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/driver...sc-hpr153i-mid-tweet-combo/compression-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?
 
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thomasjefferson

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Joined 2009
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".
 
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CLS

Member
Joined 2005
thomasjefferson said:
... It's kind of the reverse of a U-baffle, so there could be a cardioid response facing the wrong way.

...
Click to expand...

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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mayhem13

Member
Joined 2008
StigErik said:
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.
Click to expand...

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?
 
badman

badman

Member
Joined 2003
pothaudio.com
http://www.diyaudio.com/forums/planars-exotics/2651-ess-amt-1-air-motion-transformers-12.html#post2251015

I've been working with horn loading a dipole..... The assembly is mostly done. There's some more filling and sanding around the triangular pieces, and I want to knock the edge round down a little more to try to optimize profile smoothness. But in any case these will have dramatically better loading in the lower part of the passband, and a whole lot less diffraction. Sorry for the rough "real" pics, but when they start looking decent I'll put some better ones up. Pretty hard to beat a heil for a dipole with exactly equal front and rear radiation.
 
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