Bass driver with concentric port.

Circlotron · 7th September 2003, 12:17 PM

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...

SY · 7th September 2003, 12:34 PM

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...

mikee12345 · 7th September 2003, 12:47 PM

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!

Pjotr · 7th September 2003, 12:55 PM

Hi,

Agree with SY. In fact you create more problems because the mutual coupling between bass port and driver can’t 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

mrfeedback · 8th September 2003, 12:32 PM

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.

roddyama · 8th September 2003, 06:59 PM

Leave Graham alone.

Remember, they thought Galileo's ideas were crazy.

phase_accurate · 8th September 2003, 07:57 PM

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

SY · 8th September 2003, 09:21 PM

They said Edison was crazy. They said Einstein was crazy. They said Joe M. Varilla was crazy.

mwmkravchenko · 8th September 2003, 09:50 PM

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

Mark

Rotellian · 8th September 2003, 09:54 PM

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.

7th September 2003, 12:34 PM	#2
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	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... __________________ If there's a sucker born every minute, where do the rest of them come from?

7th September 2003, 12:47 PM	#3
mikee12345 diyAudio Member Join Date: Nov 2002 Location: NZ	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!

8th September 2003, 12:32 PM	#5
mrfeedback diyAudio Member Join Date: Feb 2002 Location: Perth, Australia.	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. __________________ I believe not to believe in any fixed belief system.

8th September 2003, 06:59 PM	#6
roddyama diyAudio Moderator Emeritus Join Date: Jan 2002 Location: Michigan	Leave Graham alone. Remember, they thought Galileo's ideas were crazy. __________________ Rodd Yamashita

8th September 2003, 09:21 PM	#8
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	They said Edison was crazy. They said Einstein was crazy. They said Joe M. Varilla was crazy. __________________ If there's a sucker born every minute, where do the rest of them come from?


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7th September 2003, 12:55 PM	#4
Pjotr diyAudio Member Join Date: Nov 2002 Location: Netherlands	Hi, Agree with SY. In fact you create more problems because the mutual coupling between bass port and driver can’t 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

8th September 2003, 07:57 PM	#7
phase_accurate diyAudio Member Join Date: May 2002 Location: Switzerland	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

8th September 2003, 09:50 PM	#9
mwmkravchenko Mark Kravchenko --- www.kravchenko-audio.com diyAudio Member Join Date: Jan 2002 Location: Perth Canada	Co-Drive Such a driver allready exists. There was quite a writeup in Voice coil a year ago or so. Mark

8th September 2003, 09:54 PM	#10
Rotellian diyAudio Member Join Date: Sep 2003 Location: UK	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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