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Old 1st December 2012, 08:22 PM   #21
system7 is offline system7  United Kingdom
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Quote:
Originally Posted by theaudiophile View Post
If you look at post 11 its gets more confusing. And system7 how does the felt reduce the output from the tweeter?
I have to admit I'm a bit woolly on that! I'm usually more interested in deeper problems in physics....

But a Conformal Mapping -- from Wolfram MathWorld and the Method of Images would be my approach to analysis.

Click the image to open in full size.

https://semiaccurate.com/forums/show...?t=4667&page=4

You see, where you have a boundary, you get an image of the acoustic source. If the boundary is damped by felt at certain frequencies, the image is weaker so reinforces less. This is why putting a speaker against a hard wall boosts bass 6dB.
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File Type: jpg Electromagnetism_Method of Images.JPG (34.0 KB, 140 views)
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Old 1st December 2012, 09:22 PM   #22
Decker is offline Decker  United States
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Anybody tried gluing a sheepskin to the front baffle with cutouts for the drivers? Thought about this as I passed a shop that sells sheepskin seat covers for cars.
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Old 1st December 2012, 10:08 PM   #23
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Originally Posted by Decker View Post
I passed a shop that sells sheepskin seat covers for cars.
Do they have cutouts for the drivers?
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Old 1st December 2012, 10:08 PM   #24
Bon is offline Bon  Australia
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Quote:
Originally Posted by Rudolf View Post
Bon,
if we have a tweeter mounted flush in a baffle. What would be the incident angle of the sound traveling from the tweeter along the baffle surface? The thread opener did not ask about edge diffraction of any sort.

Well, the grazing rays from the drivers are the ones to control, exactly because they "see" the baffle edges and are diffracted. Even if the baffle edges are rounded and chamfered to control diffraction, the grazing rays also "see" the frame of a typical grille. Reducing the strength of the grazing rays is a step towards controlling the deleterious effects of edge and grille diffraction. A typical dome tweeter with plate set flush in a baffle, still has a dome proud of the baffle surface and will generate low angle incidence waves on the baffle.
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Old 1st December 2012, 10:23 PM   #25
Decker is offline Decker  United States
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"Do they have cutouts for the drivers?"

Funny!
I know it was a silly question. Picturing sheepskin covered speakers gave me a chuckle. I thought I would share it.
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Old 1st December 2012, 11:07 PM   #26
Rudolf is offline Rudolf  Germany
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This is a picture of a dome tweeter on a brown baffle. The red half-circles are the fronts of the sound waves which consecutively radiate from the dome:
hyugens2.gif
Quote:
Originally Posted by theaudiophile View Post
Its also intuitively clear that it must be soaking up some of those nasty waves which are sliding along the baffle that should not really be there.
In the picture I have singled out the situation, where the wavefronts are "sliding along the baffle". What is "nasty" about it? Why should they not really be there?
Quote:
What do you guys think?

If there are no reflections whats the point of applying wool? Why does it work?
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Old 2nd December 2012, 01:06 AM   #27
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Quote:
Originally Posted by Rudolf View Post
This is a picture of a dome tweeter on a brown baffle. The red half-circles are the fronts of the sound waves which consecutively radiate from the dome:
Attachment 315178

In the picture I have singled out the situation, where the wavefronts are "sliding along the baffle". What is "nasty" about it? Why should they not really be there?
The reason you are getting confused is because you are oversimplifying. How can you be sure that the grazing angle of the tweeter rays are exactly 0 radians? Only in theory do such extreme cases arise. In practice, you are looking at strictly positive grazing angles, which means reflections do occur. In addition
the texture of the baffle, the geometry of the tweeter faceplate, can all affect the outcome.
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Old 2nd December 2012, 02:51 AM   #28
Dissi is offline Dissi  Switzerland
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Originally Posted by theaudiophile View Post
How can you be sure that the grazing angle of the tweeter rays are exactly 0 radians? Only in theory do such extreme cases arise. In practice, you are looking at strictly positive grazing angles, which means reflections do occur.
You deny grazing angles of 0 radians, but you believe in misterious reflections which do not exist. I'm baffled.
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Old 2nd December 2012, 04:06 AM   #29
Bon is offline Bon  Australia
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Quote:
Originally Posted by Rudolf View Post
In the picture I have singled out the situation, where the wavefronts are "sliding along the baffle". What is "nasty" about it? Why should they not really be there?
They get real "nasty" when they inevitably reach the baffle or grille edge. Then diffraction gives you a delayed, phase shifted version added to the original signal.
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Old 2nd December 2012, 08:38 AM   #30
Rudolf is offline Rudolf  Germany
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Quote:
Originally Posted by Bon View Post
They get real "nasty" when they inevitably reach the baffle or grille edge. Then diffraction gives you a delayed, phase shifted version added to the original signal.
I'm very well aware of what's happening at the baffle edge.
But that's not the question the OP and I asked. Do you have any opinion if there is a problem for the waves just travelling on the plain baffle surface?

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