External faseplugs

[Squeak]

By external I mean an object you put in front of the driver to get it to beam HF sound less.
The advantage being that it's much easier to install than a plug where you have to remove part of the cone, and you can make it removable in case you want to have the beaming back.

I've seen various shapes and I believe I once saw a whole site dedicated to them and experiments... Some of the most popular being the pointy lightbulb shape and cone shapes.
So peoples comments, experiences and suggestions are welcome.

[Redge]

Hi,
show us the website, any pictures ?
I would like to see that.

[MisterTwister]

probably this page
Humble Homemade Hifi
small phase plugs have very little effect.
I'd experiment with plugs bigger than a lightbulb, one that can obstruct entire speaker cone.

[sreten]

Hi,

Most of it is pure conjectural nonsense, once you understand what they do.

For less HF beaming it must be very carefully designed, and it is not a lightbulb.

That will have effects completely irrelevant to the original premise, e.g. response.

rgds, sreten.

[Squeak]

Well small wavelengths can "see" smaller objects. AFAIR human speech is already under a cm.
If bulb shapes are less than ideal, then how would one go about calculating the right shape?
Why would a steep cone shape with the point towards the center of the driver not be pretty good? I can't see how it is much different from radial diffusers.

What about slit/slot lenses, anyone know about those?

[jrenkin]

Phase Plugs

[sreten]

Originally Posted by Squeak

AFAIR human speech is already under a cm.

Hi,

No it isn't. Its fundamentally related to the size of your head, the spacing
of your ears and the occlusion of your head related to that spacing of the
directional information, which means human hearing peaks around 3kHz,
and your talking very head size related wavelengths of around 10cm.

Middle C for singing / music / instruments is over 1m.

rgds, sreten.

Its not surprising human hearing peaks at moreorless half head size.

[Bob Brines]

The main problem here is that what we generally call phase plugs aren't. A real phase plug is a devise placed in the throat of a horn to form a proper wave front into the horn, as described in the article quoted above. The chunks of word and metal we use to replace dust caps create or remove cancellations across the cone. The few I have played with act as notch filters up in the sibilance range and are indeed beneficial. Some of the larger ones affect dispersion, which is good or bad depending on the beholder.

Bob

[Squeak]

So if you wanted to make one that affected dispersion, how would you go about it? Remember I want something that's removable, so I can get the directivity back if I want to. So Lowter style magnet mounted mushrooms are out of the question.
Would a flying saucer shape, a little smaller than the cone, put as close to the driver as possible be totally nugatory?

[Bob Brines]

Originally Posted by Squeak

So if you wanted to make one that affected dispersion, how would you go about it?

Personally, I wouldn't try. The logical extreme of your quest is a vertically mounted driver with a cone shaped reflector above it that changes the directivity to horizontal. To go part way is fraught with difficulty because different frequencies come off of different parts of the driver/whizzer. You could also wind up partially horn loading either the cone of the whizzer.

Good luck!
Bob