Bass driver with concentric port.

[mrfeedback]

Leave Graham alone.

Hey, I never said Graham is crazy.
I have said that I suspect the water where he comes from.

Eric / - Never Drinks Tap Water.

[Brett]

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.

[phase_accurate]

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

[navin]

Originally posted by Circlotron
Anyway, if I could wave a magic wand and make any kind of driver at allOver to you...

if i could i'd wish for a full range (line source, planar or other) and forget about the vented pole piece.

[ir]

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

[Circlotron]

My long term goal of course, is to stealthily break your brains. Buahahaha You only get to see a small percentage of the ideas....

[wintermute]

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.

[SY]

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.

[phase_accurate]

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