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...
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...
Attachments
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...
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!
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!
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
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
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.
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 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
But I don't regard this as a negative attribute !😎
Regards
Charles
Co-Drive
Such a driver allready exists. There was quite a writeup in Voice coil a year ago or so.
Mark
Such a driver allready exists. There was quite a writeup in Voice coil a year ago or so.
Mark
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.
Hey, I never said Graham is crazy.
I have said that I suspect the water where he comes from.
Eric / - Never Drinks Tap Water.
A lot of air moving through the pole peice could be beneficial in cooling a pro driver that's absorbing several hundred watts for hours on end. Otherwise, I don't see much point.
re: cooling
JBL uses the reflex port of their cheap active P.A. speakers for cooling purposes, though they use it for cooling of the amp.
But I remember seeing a drawing (about 20 years ago) by Sony, showing a speaker where they made voice-coil cooling by the use of a bent heat-pipe. The heat was transported to a some radial fins inside the reflex tunnel.
There is no reason why Graham's principle shouldn't work. But you will be very restricted regarding tube diameter and the range of possible tunings.
Regards
Charles
JBL uses the reflex port of their cheap active P.A. speakers for cooling purposes, though they use it for cooling of the amp.
But I remember seeing a drawing (about 20 years ago) by Sony, showing a speaker where they made voice-coil cooling by the use of a bent heat-pipe. The heat was transported to a some radial fins inside the reflex tunnel.
There is no reason why Graham's principle shouldn't work. But you will be very restricted regarding tube diameter and the range of possible tunings.
Regards
Charles
Circlotron said:
if i could i'd wish for a full range (line source, planar or other) and forget about the vented pole piece.
Fender use this sort of design in their amps but with the dust cover
reason being, as the dustcover is moved in and out, it draws/blows air thru the middle thus cooling the whoel arrangement. If it didn't, the 4x12inch drivers in a 100W cabinet could get mighty hot after a gig at full volume
reason being, as the dustcover is moved in and out, it draws/blows air thru the middle thus cooling the whoel arrangement. If it didn't, the 4x12inch drivers in a 100W cabinet could get mighty hot after a gig at full volume
My long term goal of course, is to stealthily break your brains. Buahahaha 
You only get to see a small percentage of the ideas....
You only get to see a small percentage of the ideas....
The thing I wonder about is what effect does the dust cap have in the overall radiation of sound??? (not really knowing anything about the physics of it)
If you have a hole in the center of the speaker up to maybe 5cm or more in dia, isn't that going to effect the ability of the driver to move air?
moreover if the air is rushing into the port as the driver moves out, and vice versa, wont that make things even worse?????
I probably need to read up again on ports and phase!!!
Regards,
Tony.
If you have a hole in the center of the speaker up to maybe 5cm or more in dia, isn't that going to effect the ability of the driver to move air?
moreover if the air is rushing into the port as the driver moves out, and vice versa, wont that make things even worse?????
I probably need to read up again on ports and phase!!!
Regards,
Tony.
Dustcaps become important as you move into the midrange- for a sub or atrue woofer, they don't have a huge effect.
Yes, having a hole instead of diaphragm will decrease the amount of air moved for a given displacement.
Yes, having a hole instead of diaphragm will decrease the amount of air moved for a given displacement.
Dust caps can be taylored for the upper frequency range, therefore some drivers have very stiff dust-caps. Without any dustcap also the radiating area is smaller.
But it can still be made working well, just have a look at all those coaxial drivers, drivers with a phase-plug and of course all those where the dust-cap is just that: a DUST cap !
Regarding the 100 watts guitar speaker: I personally do not regard 100 Watt speakers as real high-power speakers and I think it would work with airtight dustcaps as well. A human being radiates more than 100 Watts of heat into his surroundings on average ! There are closed-box subs in the KW range that don't cook when operating. There are even closed P.A. subs that can take a lot of average power: www.bagend.com
Regards
Charles
But it can still be made working well, just have a look at all those coaxial drivers, drivers with a phase-plug and of course all those where the dust-cap is just that: a DUST cap !
Regarding the 100 watts guitar speaker: I personally do not regard 100 Watt speakers as real high-power speakers and I think it would work with airtight dustcaps as well. A human being radiates more than 100 Watts of heat into his surroundings on average ! There are closed-box subs in the KW range that don't cook when operating. There are even closed P.A. subs that can take a lot of average power: www.bagend.com
Regards
Charles
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