These days I prefer single forward radiating tweeters with good directivity. Either seas dxt or horn and compression drivers.
Rear radiating high frequencies can be unpleasant when played very loud. I really think rear hf projection should be minimised.
Rear radiating high frequencies can be unpleasant when played very loud. I really think rear hf projection should be minimised.
Heil AMTs and even Beyma TPLs are too wide to operate in dipole dispersion pattern above say 3-4kHz. Easily checked with Edge or similar. A nude BG Neo3 reaches 6kHz (dipole null) Sad that they are out of production now.
I don't know if some other magnetostatic tweeter could be used without backplate. Someone should play with eg. with this Dayton Audio AMT1-4 Air Motion Transformer Tweeter 4 Ohm - AMT Series - Loudspeaker Drivers By Series - Loudspeaker Components
I don't know if some other magnetostatic tweeter could be used without backplate. Someone should play with eg. with this Dayton Audio AMT1-4 Air Motion Transformer Tweeter 4 Ohm - AMT Series - Loudspeaker Drivers By Series - Loudspeaker Components
Waveguide?
Hi
Will two small dome tweeters with a built in narrow waveguide mounted back to back and out of phase give a dipole radiation pattern?
The waveguide should somehow control the dispersion to the sides.
best regards
uwe
Hi
Will two small dome tweeters with a built in narrow waveguide mounted back to back and out of phase give a dipole radiation pattern?
The waveguide should somehow control the dispersion to the sides.
best regards
uwe
Once you accept that true dipole is a means, not a purpose (purpose is controlled directivity) I think that should be somewhat workable, but the devil is in the details.
Generally, you have 3 main ways to control directivity:
1. waveguide
2. dipole
3. source size
If you use waveguides back-to-back, then you would want to use dipole directivity up to where it still works (dipole peak) and then smoothly blend into waveguide directivity. It's probably not trivial to get right because as you change the waveguide size (which is the "baffle" for the dipole) you also change the dipole peak.
You can use the same approach for a planar tweeter (waveguide at the front and back) and thus eliminate the requirement for a very narrow baffle. Actually, the big Heil AMT is a planar with symmetric waveguides at the front and the back to control directivity.
Is there really any point of having "pure" dipole operation all the way up ? Dipole pattern is a means, for directivity not a purpose. You can achieve similar directivity with (shallow) waveguides blending in where the dipole operation stops.
An externally hosted image should be here but it was not working when we last tested it.
TB W2-800SL
57mm diameter
up to ~5k
magnet mount baffleless 1-4pcs depend of needed db
A fullrange dipole radiating speaker is not possible in real life.
In the low end speaker size is easily the limit (or room space available behind the speaker)
In the upper end speaker size is the limit (how small it can be) the highest dipole peak varies from 2-6kHz. Transition from dipoel to "normal monopole" radiation pattern should be smoot and some rearside treble radiation is beneficial too.
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All speaker design and construction is a blend of compromises. With no/minimal baffle it is easy to construct different prototypes before making the final artistic and well polished showroom speaker!
In the low end speaker size is easily the limit (or room space available behind the speaker)
In the upper end speaker size is the limit (how small it can be) the highest dipole peak varies from 2-6kHz. Transition from dipoel to "normal monopole" radiation pattern should be smoot and some rearside treble radiation is beneficial too.
-
All speaker design and construction is a blend of compromises. With no/minimal baffle it is easy to construct different prototypes before making the final artistic and well polished showroom speaker!
There is no point. Uniform "dipole like" forward directivity is more easily accomplished at high frequencies by a waveguide, which combined with dipole mid and upper bass gives the desired uniform pattern.
The back pattern (to match the dipole rear lobe) is less important since that sound is heard only after reflection from (preferably diffusing) walls. Rear phase is unimportant (except to avoid a null at crossover) since diffuse reflection obliterates phase.
One specifically does not want specular reflection producing apparent secondary localization, and in general one does want a falling high frequency response to the rear to give the more natural sounding falling power response in the room. That is much more easily accomplished with a separate rear-firing tweeter or, in some cases, none at all . . .
dewarth, I agree 100%. I still use a planar tweeter though (Neo3) in a shallow double waveguide because I like how it sounds and, as mentioned before, I attenuate the back badiation using absorbtion.
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