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panel in a speaker cabinet, or non parallel walls in a room prevents standing waves, as that is the claim that was originally made, and that original claim needs support.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.
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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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.
many speakers have been built based on pyramid shape or other curved shapes. If it didn't help nobody would bother.
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
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
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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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...
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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@DBMandrake at what phase is the reflection encountering the source ?
I guess the whole idea of the slant is to create many modes, hopefully some will cancel out others as the reflection hops around. Damping maybe desirable so as to weaken each reflection.
The backwave just needs to be delayed and weakened. Also any resonances from the other cabinet walls need to be addressed.
Also for a small room where the speaker is firing at a wall opposite, although the pressure is lower in the room, it may help to have a slightly slanted front baffle (I could be totally wrong here).
kind regards,
Harrison.
at what phase is the reflection encountering the source ?I guess the whole idea of the slant is to create many modes, hopefully some will cancel out others as the reflection hops around. Damping maybe desirable so as to weaken each reflection.
The backwave just needs to be delayed and weakened. Also any resonances from the other cabinet walls need to be addressed.
Also for a small room where the speaker is firing at a wall opposite, although the pressure is lower in the room, it may help to have a slightly slanted front baffle (I could be totally wrong here
).kind regards,
Harrison.
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I believe this to be a very naive view. It matters because of marketing and what road apples you can get the reviewers to spout. Think speaker cable. I am not at all dismissing the visuals. We do usually look at the speakers, so it can be an important requirement.
There is one and only one way to determine the usefulness. MODEL & PROTOTYPE. Not one, but multiple versions of the same system. Then MEASURE and LISTEN to the crossover alignment and imaging to see if it is an advantage. I can say I have heard sloped systems like Theil that were very good. I have heard offset systems like Vanderstein that are very good. Are they better than if they were a box? I have no idea. I have heard offset and sloped systems what were very bad too. My old modified Celestion Ditton 44's were slightly better balanced tilted back in one room, but better straight up in another. I test all of my prototypes tilted and have never found any sonic advantage.
A non-regular rectangle may assist in distributing the diffraction ripple. If you play with EDGE a bit, you will find you can play with position to the same effect on a rectangular baffle.
I once did a slightly curved side box to stress the MDF and see if I can move panel resonances around with thinner and lighter material like the Kef Q1s I once had, or if the space required is better used for a thicker flat side. I don't pay to ship my speakers, so light weight is no advantage. I went back to flat sides as the answer was no.
So the trap is that although physics tends to be pretty intuitive, you need to be careful and put that intuition into the correct set of parameters. Don't fall for " because he did it". "He" may have not known what he was doing no matter how much he was paid. He may have.
I still don't understand your example. Does everybody else? can somebody else explain
HaHa, this IS wandering. Sloped baffles are FACT!
I don't think anyone slopes baffles to avoid internal reflections. The reason you do it is to align phase on the two drivers at the listening position. You can observe that if you listen to a two way above and below axis the overall sound and feeling of INTEGRATION of the drivers changes.
Sloped baffles are used to point the optimum loud lobe directly horizontally. This can occasionally be done with a flat baffle where the drivers and filter play nicely together, but sloping the baffle to time align the drivers' acoustic centres is an option. It is also an unavoidable fact of regular two ways the you lose power above and below axis. FWIW, MTM D'Appolito designs change the rule book slightly.
This is a DIY stepped baffle, courtesy of Michelino:
This is a commerial sloped baffle, courtesy of Joachim Gerhard:
Good phase alignment and good lobing are quite deep topics, with different solutions depending on filter order and drivers chosen. But done with care, IMO are two things that make for a good speaker.
I don't think anyone slopes baffles to avoid internal reflections. The reason you do it is to align phase on the two drivers at the listening position. You can observe that if you listen to a two way above and below axis the overall sound and feeling of INTEGRATION of the drivers changes.
Sloped baffles are used to point the optimum loud lobe directly horizontally. This can occasionally be done with a flat baffle where the drivers and filter play nicely together, but sloping the baffle to time align the drivers' acoustic centres is an option. It is also an unavoidable fact of regular two ways the you lose power above and below axis. FWIW, MTM D'Appolito designs change the rule book slightly.
This is a DIY stepped baffle, courtesy of Michelino:
An externally hosted image should be here but it was not working when we last tested it.
This is a commerial sloped baffle, courtesy of Joachim Gerhard:
An externally hosted image should be here but it was not working when we last tested it.
Good phase alignment and good lobing are quite deep topics, with different solutions depending on filter order and drivers chosen. But done with care, IMO are two things that make for a good speaker.
thats true for any triangle not only right angled ones like the example he gave.
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