Hypothesis - improving off-axis dispersion from a dome tweeter

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T

Think

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Replace it with a smaller dome tweeter as the narrowing off axis response for the higher frequencies is a function of it's size.

I love narrow planar tweeters for their off axis response; narrow vertical (no floor and ceiling bounce) and super wide horizontal.

An example https://doc.soundimports.nl/pdf/brands/Dayton Audio/PTMini-6/pdf_Dayton Audio_PTMini-6_1.pdf The downward slope sounds just fine but could be eq-ed up (very dampened room or outdoors?) as the on and off axis response are identical.

These work best with a number of small (3-4") mids and bass woofers should IMO always be in their own sealed box and in a corner of a room.
 
adason

adason

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TBTL said:
Which plots are you referring to?



I'd like to try what a loudspeaker sounds like with constant directivity and a wide horizontal dispersion between 300 - 15.000 Hz. A wide vertical dispersion is not necessarily what I am after, but as I do not know of a practical way to reduce vertical dispersion to < 180 degrees at low midrange frequencies, I would like to have 180 degrees dispersion at high frequencies as well.
Click to expand...

in the link you provided, click on measurements, you can see significant beaming on vertical plots in comparison to horizontal
RAAL 140-15D
 
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454Casull

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adason said:
Based on measurements, the foam is norrowing the vertical dispersion. Clearly visible on the plots.
Why would you want the sound to bounce from floor and ceiling?
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That really depends on the application. For nearfield usage, e.g. monitoring, you generally want more dispersion so that the response is less impacted, relative to any given amount of head movement. At the same time, because the distances are smaller, the ceiling bounce is largely out of the picture (you'd have to be anywhere from 60-80 degrees off axis for the ceiling bounce) and the "floor" (desk) bounce could be mitigated pretty easily with surface treatments.

As others have mentioned already, a ribbon already has pretty restricted vertical dispersion. Without further measurements it's hard to tell exactly what kind of impact the foam has, but I would guess that it actually does improve it.
 
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drewmc

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Electro-Voice used a foam ring with a small aperture around a large dome on some of their stage monitors back in the '70s. I had a friend who had a pair of these. There is the issue that if the dome is not truly pistonic, the center of the dome decouples and the high frequency output is reduced at the center of the dome.
 
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454Casull

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Joined 2004
drewmc said:
Electro-Voice used a foam ring with a small aperture around a large dome on some of their stage monitors back in the '70s. I had a friend who had a pair of these. There is the issue that if the dome is not truly pistonic, the center of the dome decouples and the high frequency output is reduced at the center of the dome.
Click to expand...
Right, this is pretty much exactly what I was thinking of.

Perhaps if one were to use a contoured piece of felt or absorptive material and isolated a section of the dome close to the voice coil, this could be avoided.
 
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