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Post by chrisbee on Mar 9, 2006 7:04:24 GMT -7
Is an "outie" identical in performance to an optimised manifold of exactly the same size, number of drivers and opening area?
One lives in the room and exhausts into the backspace. The other sits in the backspace and fires into the listening room/HT via the manifold opening.
But are they a true mirror image of each other with regards to sound quality?
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Post by ThomasW on Mar 9, 2006 9:27:51 GMT -7
The 'outie' might have a slight performance advantage. But without a real world test this is speculation on my part.
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Post by chrisbee on Apr 16, 2006 2:05:25 GMT -7
Thomas
Despite your misgivings I keep thinking about these tall underfloor manifolds. They suffer from phase and time delay effects since the opposed pairs (or quads) of drivers can't be physically in the same plane in such a long "tube". The sound from the lower drivers has to travel the greater length of the manifold before it escapes into the room compared with the upper drivers. There lies the problem.
If such a manifold was placed in the room and the exit area placed in sealed contact with a hole in the ceiling (or floor) there would be no phase problems.
The drivers would be in much the same plane within the room as a tall "outie".
Rather than the sound having to travel the length of the manifold from the lower drivers in a hidden manifold. Only the backwave would suffer from these phase and delay effects in an outie. But as the backwave is completely "lost" under the floor (or up in the attic) it should not be audible.
A further advantage: There would be no need to go into the crawlspace or attic. Just make a hole and prop up your 24 x15" driver, floor-to-ceiling, tube manifold.
In fact you could use the crawlspace and the attic simultaneously for better backwave dynamics from the instantly-doubled exhaust area! The fully opposed drivers would cancel out physical vibrations in the column(s).
You'd have to consider the area of the manifold opening areas, of course, so as not to comprimise the perfomance of the IB too much. But just think how many drivers you could stuff into such a tall column!
Too wacky? Hi-techy? Or just plain tacky? ;D
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brady
Full Member
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Post by brady on Apr 16, 2006 7:49:29 GMT -7
A huge manifold floor to ceiling, I like it  As far as phase issues and sound quality, I think Thomas said there was no difference between his upstairs room and the basement. |
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jonfo
New Member
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Post by jonfo on Apr 24, 2006 5:02:58 GMT -7
While I’ve not built an underfloor manifold, my outie performs above all my expectations.
One reason I think an outie is possibly better is that the radiating surfaces are all in room and form a sphere of radiation or pressure wave at a room junction point (Mine is center front at the floor / front wall junction) that helps really put the pressure wave ‘into’ the room.
Whatever the case, it measures and sounds awesome.
Your idea for a large muti-driver column is intriguing. You basically are right about not having the resonance issue in room, but I wonder if the pipe resonances in the manifold will still impact what the drivers are able to generate in-room. No free lunch there?
What you describe (a floor to ceiling manifold) is pretty much a Line Array system. You could use smaller 10” or even 8” drivers (a whole lot of them to cover the four sides) and basically have a subwoofer / mid-bass line array system. You could play this up to 250Hz or so, and use a shallow crossover to the mains.
Talk about slam. These would destroy the mid-bass of any commercial speaker. Remember that the chest cavity resonance of the avg male is around 160hz. When you feel drums ‘hitting in the gut’ or ‘slamming’ that’s the frequency that matters.
Read up on line array theory and see if this might be an option.
For those that do not know, a line array of high quality 8” drivers of about 7’ length would house 10 drivers per side or 40 drivers total. (sort of cost issue there). That many drivers plus the effects of room boundary mirroring from line arrays would yield very low frequency output at low distortion as well as giving you the option of going pretty high (for a sub) before the x-over.
Food for thought…
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Post by chrisbee on Apr 25, 2006 0:01:26 GMT -7
Interesting.
What would be the requirements for these smaller drivers?
Perhaps one could get a bulk discount?
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jonfo
New Member
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Post by jonfo on Apr 26, 2006 17:34:10 GMT -7
I'd recommend the Adire Extremis 6.8 if you want to crossover high. But it's not cheap at $99/ea. I just bought 6 for a 'short' line array for my Center Channel project. They are very well built. I assemble the whole thing next week. Look for measurements and what not within the next ten days. Here's the thread looking into it, there are some other driver recommendations included in that thread as well: www.diyaudio.com/forums/showthread.php?s=&threadid=76975An 8 or a 10" is probably cheaper and will do better down low. |
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Post by carpenter on May 12, 2006 15:58:12 GMT -7
Hi everyone,
Parts Express has an affordable, stackable TangBang woofer (W8Q-1071) measuring 8" x 12" that would be perfect for a floor to ceiling IB line array. I simmed 16 units in a 2000 cubic foot enclosure. With an Xmax of 12mm, the tower (exits on attic and crawlspace) will accept 100 watts before becoming nonlinear. I EQ'ed the bottom end at 20hz with 11db gain, thus yielding a 3db down at 18hz. The SPL at 100 watts input came to 120db. I would place the drivers on a arc, which basically aims the energy toward the listener. This helps to eliminate the comb filtering effect.
Pretty darned impressive--especially when you consider that a line source only losses 3db as you double the distance from the array vs a point source that loses 6db.
More food for thought. ;D
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Post by ThomasW on May 12, 2006 21:29:48 GMT -7
The primary issue with non-round drivers is that the suspension stresses the cone on a non-linear manner. As a result the cone motion isn't pistonic. So the SQ suffers...
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Post by carpenter on May 12, 2006 22:14:19 GMT -7
If it's not pistonic, then what is it? I see a rectangular piston.
My primary fascination with this driver is the ability to stack them close together, thus keeping their center axis tightly coupled. This enhances the line array's ability to produce higher frequencies/harmonics without cancellation and keep the array sounding more cohesive.
John
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Post by ThomasW on May 12, 2006 23:04:35 GMT -7
A round driver has equal tension along it's edges. That helps keep the cone motion linear. Non-round drivers have unequal tension on the cone particularily at the corners.
Given the passband where an IB is operating a grouping that tight isn't needed. If one is designing something like a MTM main speaker, then yes one wants the drivers close together. And that's why a number of companies make units where the cone is round but the mounting flange is flat on 2 sides.
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Post by carpenter on May 12, 2006 23:34:43 GMT -7
One would presume in a case like this, TangBang would give me the drivers just to prove their superiority... Ha  John ;D |
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