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Old 24th May 2011, 12:52 PM   #1
el`Ol is offline el`Ol  Germany
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Default What enclosure type is this?

Hello all!

Currently I am walking on the borderline between OB and enclosure with some success.
More as a desperate try without much hope to get more bass extension I put a sewer pipe I had left from an other experiment behind a U-Frame and it worked so well that I made a permanent installation out of it.
But what is it? Is is just an OB with enhanced acoustic short circuit? Or is there some loading?
The other expample: a corner speaker consisting of three quarter-circles. Surprising bass from a little fullranger with good tonal balance. Physical impact of a horn, but directed bass response like a dipole. Which of the two is it?
I didn't do measurements, a bit because I fear that it measures worse than it sounds, a bit because of laziness.

Oliver
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Old 24th May 2011, 10:13 PM   #2
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Interesting, you could probably model these several ways, maybe one way to view the first one is as a lossy quarter wave pipe, 'cause you'll have some pipe resonance, but the Q will be lowered by the open sides...??? But of course there will be some OB effects as well. Have you tried some damping directly behind the driver, to eliminate reflections though the cone?

The second one looks a bit like a Karlson, without the BR behind the driver, more like a TL with a flared opening, (I've tried this too, using 6" pipe, it works well)
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Old 25th May 2011, 06:25 AM   #3
el`Ol is offline el`Ol  Germany
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I don't think there are TL effects, at least no useful ones. Speaker one is 1 meter and open at both sides, so a half wave resonatior, second speaker is 50x50x50 cm. Resonances should be in the fundamental region, without influences on the bass.
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Old 25th May 2011, 06:33 AM   #4
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Methinks if you blocked the top (sit some board on top), it'd turn into some rear-loaded horn.

The driver won't be experiencing much loading from the cabinet at low frequencies, of this I'm almost certain.
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Old 25th May 2011, 07:59 AM   #5
el`Ol is offline el`Ol  Germany
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I think I'll have to measure again and post the two curves. The U-frame alone gave 80 Hz and would have needed a sub urgently. Now I can live more or less without it, and I don't think this is because a rise >= 80Hz. Can it be a horn-reflex?
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Old 25th May 2011, 08:28 AM   #6
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Midway between open and closed box ,or at least the back wave sees a sort of micro-hall (ambient),so what you hear is an already reverberated sound that is already 'ambient processed' on its own .
IMO
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Old 25th May 2011, 10:11 AM   #7
el`Ol is offline el`Ol  Germany
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So an elongated acoustic short circuit?
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Old 25th May 2011, 10:40 AM   #8
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sorry : 'elongation' finds no matches in my brain
time : 0.1 s
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Old 25th May 2011, 12:50 PM   #9
el`Ol is offline el`Ol  Germany
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The foldings don't cause loading, but just make the acoustic short circuit longer.
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Old 25th May 2011, 08:05 PM   #10
el`Ol is offline el`Ol  Germany
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Strangely in free-field the bass extension is rather less, but there is no pipe resonance whatsoever and also the 200 Hz peak probably caused by baffle diffraction is gone. The advantage in bass extension is only there close to a corner, but also here it is mainly the improved bass quality that counts. The tube obviously mainly did what I originally intended, and that very well.
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