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Old 30th December 2006, 11:40 AM   #1
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Default Dipole BIB ?

http://www.acuhorn.pl/table.htm
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Old 30th December 2006, 12:51 PM   #2
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Ah yes, the Accuhorn 175. Dunno, to be honest. I haven't seen any good pictures of it, which show a mouth or any detail. The 125 initially looks like an inverted BIB, but in fact, from some shots I found a while ago, appears to be a BVR design.

If it's a dipole, then the drivers must be internally partitioned off from each other, or the rediation from the rear unit, being 180 degrees out of phase with that from the front, would simply cancel out. If they're not partitioned off from each other, then they're actually bipoles, with the drivers running in-phase. In which case, they could have a central expansion upward (or downward) with an additional sloping baffle for the rear unit. My only concern about that is the BIB is a corner horn, and needs the reflection boundary conditions to supress ripple, and you can't do that with bipole or dipole designs. Anyone know of any better shots of these things?
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Old 30th December 2006, 01:28 PM   #3
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Scott,

What would happen if these are dipole bibs, as in two separate enclosures put back to back, if they were placed near a corner? Would the driver facing the corner cause problems in some way?
You may have touched on this and I was to dense to catch it.

Also I wonder what the result would be if you did have two BIB's connected back to back with one firing up and the other down?

One thing I will say about these in the picture, they're well executed, very tastefully done.

Rick
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Old 30th December 2006, 09:46 PM   #4
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>>> Also I wonder what the result would be if you did have two BIB's connected back to back with one firing up and the other down?

That sounds interesting. Any of the usual BIB drivers could be used but a double BIB using 4" drivers like the Fostex 127 or TB Bamboo could be rather room friendly. They are so thin they could litterally be placed side by side (one forward one backward) glued and screwed together.

Hmmmm....
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Old 30th December 2006, 10:04 PM   #5
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I was thinking that from the outset it would be easy to just build them that way. Either back to back or side by side. That way the end result would be much cleaner and use less material.

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Old 30th December 2006, 10:07 PM   #6
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Quote:
a BVR design.
What's that Scott?

Rick
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Old 31st December 2006, 06:49 AM   #7
jamikl is offline jamikl  Australia
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Whilst talking about dipole BIBs and even dual BIBs I have wondered at the possibility of building two BIB towers side by side, maybe one forward and one backward and maybe, as was mentioned, one up and one down with something akin to an Oris horn mounted between them at the right ear height. If this was possible it would allow maybe half of the horn to be buried between the two BIBs and may well look better than trying to mount a horn on the front of the speaker in a single BIB. Any thoughts on this Scottmoose or GM or anybody else who may have an opinion.

A happy new year to you all and may the thinkinking continue. Be nice to be able to afford 'to do' as well!!
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Old 31st December 2006, 07:27 AM   #8
chrisb is offline chrisb  Canada
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Quote:
Originally posted by Rick J. B.


What's that Scott?

Rick

see Scott's designs Harvey/Bruce (and no doubt further progeny) - a long thread, with some interesting developments.



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Old 31st December 2006, 10:28 AM   #9
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I know that feeling.

Rick: BVR = Big Vent Reflex. You know how most domestic 'horns' feature a small chamber, and a long gradually flaring path length?
A BVR turns this on its head. It has a very large chamber, coupled to a short, rapidly flaring horn (or to be more accurate, waveguide). In technical operation their a reflex box with huge, expanding vents.

Pushing a dipole against a wall is a tricky one -you'll get lots of early reflections, and increase the likelihood of the rear radiation cancelling out that from the front. It's not as bad as some would have you believe, but it's difficult to get going right. A couple of feet at least is a good idea between cabinet and rear wall.

A way of doing this would be to design two unfolded ML TQWTs in the same cabinet, with drivers placed at 50% line length. Alternatively, an inverted BIB, deepened so that a second expansion at the rear could take place, both joining at the top and flaring downward, and then use the plinth to adjust the cabinet height and partially short the output CSA. Castle did something similar with their Harlech / Harlech S2 and Howard S3 designs I believe. Just a fair bit smaller. That would have to be run bipole though rather than dipole. Not that that's a problem: bipole is great.
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Old 31st December 2006, 02:20 PM   #10
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Oh I'm definitely looking into this, it sounds very interesting.

Rick
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