Bass driver with concentric port. - diyAudio
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Old 7th September 2003, 12:17 PM   #1
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Default Bass driver with concentric port.

I read a while back about some loudspeaker box having an annular port around the periphery of the driver (well, tautologically speaking anyway ) The puprpose was something to do with the phase realtionship of the driver and port waveform time relationship because they now share a common centre.

Anyway, if I could wave a magic wand and make any kind of driver at all, I would try something like I drew in the attached drawing. (Will someone please call the tautology police? )

The port is now incorporated as part of the centre pole piece. Both cone as port share a common centre. Also, centre pole cooling would be great! Over to you...
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File Type: png concentric port.png (22.8 KB, 307 views)
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Old 7th September 2003, 12:34 PM   #2
SY is offline SY  United States
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What's the point? At the wavelengths involved, the port can be quite a distance away without affecting "phase" or "time relationships" in any meaningful way. One more example of creating problems while trying to solve one that doesn't exist...
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Old 7th September 2003, 12:47 PM   #3
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Default trust not just any book.

50hz=6.8metres long,so no 1/4 or 1/2 wave effects can harm anything as i understand it.....

but long box dimensions, could get into it.

it looks cool anyway
port in the cone
who wouldve thought!
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Old 7th September 2003, 12:55 PM   #4
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Hi,

Agree with SY. In fact you create more problems because the mutual coupling between bass port and driver canít be neglected anymore. The work of Thiele and Small ignores mutual coupling.

Note what counts for a bass reflex port is the mass of air herein. For substantial mass you need substantial cross section area of the port. This means a large hole in the pole piece.

Cheers
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Old 8th September 2003, 12:32 PM   #5
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Graham,
By fitting a dustcap, mounting that driver in the middle of a door, and extending that tube out long enough you could make a dipole with TL loading.

Eric / - More crazy ideas inspired by Graham.
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Old 8th September 2003, 06:59 PM   #6
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Leave Graham alone.

Remember, they thought Galileo's ideas were crazy.
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Old 8th September 2003, 07:57 PM   #7
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I think I also once mentioned that Graham was an unlimited source for crazy ideas.

But I don't regard this as a negative attribute !

Regards

Charles
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Old 8th September 2003, 09:21 PM   #8
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They said Edison was crazy. They said Einstein was crazy. They said Joe M. Varilla was crazy.
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Old 8th September 2003, 09:50 PM   #9
Mark Kravchenko --- www.kravchenko-audio.com
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Default Co-Drive

Such a driver allready exists. There was quite a writeup in Voice coil a year ago or so.

Mark
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Old 8th September 2003, 09:54 PM   #10
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Actually, all modern tannoy dual concentrics have a bass driver with a hole through the middle for the HF unit. Ive got a pair salvaged. Doesnt sound that great without something there.
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