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Old 12th March 2013, 10:05 AM   #2061
Elias is offline Elias  Finland
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Originally Posted by graaf View Post
can You post simulations for 700, 1000 and 1500 Hz?
I already made a bunch of simulations, not only this configuration but others as well. I will propably put them on my home page as soon as I find some free time.
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Old 12th March 2013, 10:20 AM   #2062
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What's the conclusion from looking at the numbers and simulations?
Floor and ceiling reflections are too early in time, too low in level and to close to the direct sound source to be of much value?
Should a speaker design avoid, enhance or ignore them?
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Old 12th March 2013, 10:40 AM   #2063
graaf is offline graaf  Poland
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Originally Posted by Rudolf View Post
But if two waves travel almost parallel, their phase relation doesn't change significantly on their way. So they are sensed as one.
but if two wavefronts arrive at the ear at a different time then there is yet no phase relation but they are not sensed as one or are they? I think not but of coruse I may be wrong
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Old 12th March 2013, 10:45 AM   #2064
graaf is offline graaf  Poland
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Originally Posted by Elias View Post
Sure there are ! Its called wave equation
Acoustic wave equation - Wikipedia, the free encyclopedia
Feynman etc. impressive and very wise

but are there any simplified formulas that allow us to predict more-or-less precisely when there will occur a specular reflection? Having regard to the wavelength and the distance from the sound source to the reflective surface?
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Old 12th March 2013, 10:53 AM   #2065
graaf is offline graaf  Poland
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Originally Posted by Elias View Post
I already made a bunch of simulations, not only this configuration but others as well. I will propably put them on my home page as soon as I find some free time.
would be great! I an looking forward to it!
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Old 12th March 2013, 10:57 AM   #2066
graaf is offline graaf  Poland
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Originally Posted by markus76 View Post
What's the conclusion from looking at the numbers and simulations?
Floor and ceiling reflections are too early in time, too low in level and to close to the direct sound source to be of much value?
Should a speaker design avoid, enhance or ignore them?
It took over 2000 posts for anyone to ask this crucial questions

and the award goes to ...Markus!
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Old 12th March 2013, 11:01 AM   #2067
Elias is offline Elias  Finland
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Quote:
Originally Posted by markus76 View Post
What's the conclusion from looking at the numbers and simulations?
Floor and ceiling reflections are too early in time, too low in level and to close to the direct sound source to be of much value?
Should a speaker design avoid, enhance or ignore them?
Too early for conclusion, but meanwhile I disagree with unimportance of floor reflection.

It can be said that lifting midrange driver 1m above floor is not the way to go. Look at the floor and ceiling reflections in the post #2045. Floor reflection is very strong at the listening position, so is ceiling reflection. Certainly their affect timbre, if nothing else. I think there are other perception factors too.
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Old 12th March 2013, 11:06 AM   #2068
Jmmlc is offline Jmmlc  France
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Hello Elias,

Your wavetank simulations are interesting and are also useful to investigate the best position of the OB in the lateral direction.

Considering your simulation (without elevation), the OB should also be placed touching the lateral wall...

Best regards from Paris, France

Jean-Michel Le Cléac'h



Quote:
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I'm in the design phase of my new loudspeakers, and exploring the floor reflection contribution therein I made some FDTD simulations of the case.


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Old 12th March 2013, 11:14 AM   #2069
lolo is offline lolo  France
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Quote:
Originally Posted by Elias View Post
It can be said that lifting midrange driver 1m above floor is not the way to go. Look at the floor and ceiling reflections in the post #2045. Floor reflection is very strong at the listening position, so is ceiling reflection. Certainly their affect timbre, if nothing else. I think there are other perception factors too.
Well, I actually worked on it over the weekend. Since I moved houses last year I always had a timbre and dynamic issue, the ceiling is low, only 2.3m high. I always suspected the ceiling so finally had a whole day to do take measures. So nice to see the graphs confirming it, massive reflexion at 3ms. I stacked some acoustic foam on top of the tweeter and bingo, the reflexion went 15db down.. How does it sound? I can play louder and don't have that terrible high midrange emphasis that made everything shout at me, and now a nice 10ms window to the first reflexion.
Conclusion? I don't think you'd want such an early strong reflexion, at least not on a forward firing setup. My 2c.
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Old 12th March 2013, 11:17 AM   #2070
graaf is offline graaf  Poland
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Originally Posted by lolo View Post
that terrible high midrange emphasis that made everything shout at me
problem is not with the ceiling reflection as such but with that particular speakers in this particular configuration
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