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Old 28th November 2013, 03:12 PM   #21
Jsixis is offline Jsixis  United States
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slanted baffle also has an effect of the waves interacting with the floor and ceiling.

I have only built 1 speaker cabinet that has a 6 degree slant, it is my single 10" bass rig.
It works for me.
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Old 28th November 2013, 03:51 PM   #22
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Originally Posted by lilun View Post
can you provide further support to your statements?
I could turn that around and ask you for evidence that a sloping front panel in a speaker cabinet, or non parallel walls in a room prevents standing waves, as that is the claim that was originally made, and that original claim needs support.

It might seem intuitive that the non parallel walls would prevent standing waves forming but that doesn't make it true. The frequency distribution will change a bit yes, but they will still form within an enclosed space whose dimensions are greater than a half wavelength in size.

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non parallel walls are used in cabinets and by studio engineers to design studios. If it didn't work why go to all the trouble?
Non parallel walls in cabinets are typically for either slanted baffle for time alignment, for styling/aesthetics, or based on the misguided idea that it will prevent standing waves.

Non parallel walls in studios are more about achieving certain room acoustics at higher frequencies, eg damping versus reflection versus diffusion.

You might be surprised at just how terrible the bass standing wave problems are in professionally designed studios, particularly in the control room, and how little effect non parallel walls have on the situation.
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Last edited by DBMandrake; 28th November 2013 at 03:55 PM.
 
Old 28th November 2013, 04:13 PM   #23
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you could turn it around but that would be evading the question. Its by definition that standing waves form between parallel walls. Thats what I have read. Its not 'greater than half wavelength' its at exactly half or other multiples.

many speakers have been built based on pyramid shape or other curved shapes. If it didn't help nobody would bother.
 
Old 28th November 2013, 04:15 PM   #24
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if the walls aren't parallel, the distance between them is not equal. How can you have standing waves which are based on different dimensions? Intuition tells you that it would help to spread out the standing waves, effectively reducing it.
 
Old 28th November 2013, 05:18 PM   #25
tinitus is offline tinitus  Europe
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think of it as a ressonance instead of 'a standing wave'

in a space its defined by volume
in a material, part of is defined by shape, and mass, etc etc
assymetric shape can cause the ressonances to move, and change
which is supposed to be better than a 'one note standing wave'
and there is a lot of sales rubbish and 'beliefs' in there too
it only works adequately when done properly
and what properly done really is ? ... please don't ask

but that is not the real point of slanted baffle
that have already been very nicely explained a few posts above
you wont get any better than that

apart from that, a slanted baffle can also be a matter of visual and practical design

oh, btw, I have also heard it being claimed that a slanted baffle radiates diffractions differently than a straight up baffle

I would suggest to consider a combination of both slanted and stepped baffle

funny that using double woofers may actually be the cause of real trouble
and that is rarely considered to be a problem in this respect

edit ... I took it for granted that slanted refers to the front baffle
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Old 28th November 2013, 05:21 PM   #26
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Quote:
Originally Posted by tinitus View Post
think of it as a ressonance instead of 'a standing wave'

in a space its defined by volume
in a material, part of is defined by shape, and mass, etc etc
assymetric shape can cause the ressonances to move, and change
which is supposed to be better than a 'one note standing wave'
so are you disagreeing or agreeing with mandrake?
 
Old 28th November 2013, 08:46 PM   #27
tinitus is offline tinitus  Europe
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so are you disagreeing or agreeing with mandrake?
yes, probably he knows more on this matter
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Old 28th November 2013, 10:25 PM   #28
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by lilun View Post
if the walls aren't parallel, the distance between them is not equal. How
can you have standing waves which are based on different dimensions?
Intuition tells you that it would help to spread out the standing waves,
effectively reducing it.

Hi,

Take a room that is any right angled triangle. Just by reflecting the
hypoteneuse your back to a rectilinear shape and standing waves.
Radically different shaped room, not much change in standing waves.

Science is not clueless intuition.

rgds, sreten.
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Last edited by sreten; 28th November 2013 at 10:32 PM.
 
Old 28th November 2013, 10:44 PM   #29
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what do you mean reflecting the hypotenuse? and back to a rectilinear shape?
 
Old 29th November 2013, 06:08 AM   #30
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Quote:
Originally Posted by sreten View Post
Take a room that is any right angled triangle. Just by reflecting the
hypoteneuse your back to a rectilinear shape and standing waves.
Radically different shaped room, not much change in standing waves.
You beat me to it - a right angled triangle was exactly the example I was going to use to demonstrate a standing wave in a room with no parallel walls. It's the obvious and easy to visualise example of non-parallel walls still forming standing waves...

Quote:
Originally Posted by lilun View Post
what do you mean reflecting the hypotenuse? and back to a rectilinear shape?
Imagine a right angled triangle where the right angle is at the bottom left and the hypotenuse is at the top right.

A wave starts on the left hand wall and travels horizontally to the right, reflects off the hypotenuse at 90 degrees, travels down, reflects 180 degrees off the bottom wall back towards the hypotenuse, reflects off the hypotenuse at 90 degrees towards the left hand wall.

If the total distance travelled by the wave is one wavelength (or multiples) a standing wave will form, in fact in the case of a right angled triangle the standing wave will be at the same frequency as a cube room with the same base and height.

Parallel walls are NOT required for standing waves to form, they just represent the simplest case where a standing wave can occur purely between two walls with a single reflection to return to the starting point.

In the right angled triangle example three reflections were required for the wave to travel one wavelength and arrive back where it started, but that's irrelevant. With more complex shapes the number of possible reflection paths increases dramatically, but there are always paths that will form standing waves.

No matter the internal shape standing waves will form, just their frequency distribution will vary.

The only way to deal with standing waves in a speaker cabinet is damping - the energy has to be dissipated somehow.
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Last edited by DBMandrake; 29th November 2013 at 06:16 AM.
 

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