I see models like Danley BC 218 and Dutch & Dutch 8c claim to have boundary coupled subs. What is the basic physics these designs are based of?
If I correctly interpret the following post: BC218
The Danley BC 218 subs can be stacked such that they exhibit directivity, just by being huge.
Dutch & Dutch 8c: the subs are close to the rear wall of the listening room, resulting in the reflected sound being in-phase with the direct sound. Therefore the reflection from the rear wall does not cause a dip in the frequency response.
The Danley BC 218 subs can be stacked such that they exhibit directivity, just by being huge.
Dutch & Dutch 8c: the subs are close to the rear wall of the listening room, resulting in the reflected sound being in-phase with the direct sound. Therefore the reflection from the rear wall does not cause a dip in the frequency response.
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I suspect Dutch & Dutch 8c is a cardioid with the driver back wave being vented to the sides, to enable bass directivity.
The link says that "guest" is permanently banned etc. But Danley BC 218 is used in live stadia and such, where there are no walls. I read two threads here that attempted to figure out Danley's method at least I couldn't understand.
Danley BC-subs reverse engineered
Tom Danley gives a good explanation in Post #89 in the thread linked above.
I believe there is a lot more to it than that but I have a hard time explaining my thoughts in writing and in english (being Swedish).
Since loudspeaker drivers have become very powerful over the last 20 years or so, we all have to take the nonlinear behaviour of sound and nonlinear dynamics into account when designing bass horns and QW band pass boxes.
Most tapped horns and high order QW designs do operate at highly nonlinear working conditions over much of their operating range. Failing to take that into account and use this to an advantage instead of fighting agains it like a normal BR port will inevitable lead to heavy losses of potential performance.
Based on some of the comments about the sound character of the BC412 and BC415 I have read over the years I conclude that Tom Danley is well versed in nonlinear acoustics and does take these aspects into account when designing his latest and greatest designs. They seem to share a lot of sound characteristics with my ROAR designs, which kind of indicates this.
Steven H Strogatz book Nonlinear Dynamics and Chaos is a great read and intro into this. Nonlinear Dynamics and Chaos: With Applications to Physics, Biology, Chemistry, and Engineering — Steven Strogatz
Tom Danley gives a good explanation in Post #89 in the thread linked above.
I believe there is a lot more to it than that but I have a hard time explaining my thoughts in writing and in english (being Swedish).
Since loudspeaker drivers have become very powerful over the last 20 years or so, we all have to take the nonlinear behaviour of sound and nonlinear dynamics into account when designing bass horns and QW band pass boxes.
Most tapped horns and high order QW designs do operate at highly nonlinear working conditions over much of their operating range. Failing to take that into account and use this to an advantage instead of fighting agains it like a normal BR port will inevitable lead to heavy losses of potential performance.
Based on some of the comments about the sound character of the BC412 and BC415 I have read over the years I conclude that Tom Danley is well versed in nonlinear acoustics and does take these aspects into account when designing his latest and greatest designs. They seem to share a lot of sound characteristics with my ROAR designs, which kind of indicates this.
Steven H Strogatz book Nonlinear Dynamics and Chaos is a great read and intro into this. Nonlinear Dynamics and Chaos: With Applications to Physics, Biology, Chemistry, and Engineering — Steven Strogatz
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BC horns from standard FLHs - Speakerplans.com Forums - Page 1
15NW100 BC Horn - Speakerplans.com Forums
Some more info in the above threads. Part of the design is the physical size of the horn imposing directivity. Another part of the design is that the termination at the mouth is taken into account.
15NW100 BC Horn - Speakerplans.com Forums
Some more info in the above threads. Part of the design is the physical size of the horn imposing directivity. Another part of the design is that the termination at the mouth is taken into account.
Thanks! Im ordering that book now!
Heres a little something for you maybe? Its strange how things are so intertwined yet obvious? harmonics.
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No, not really, just once again took a slightly different view of how a TL/horn's acoustic sound 'bubble' works WRT boundary layers, be it the mouth or the different pi room loading options, winding up with an unfinished [truncated] horn that can be configured into four distinct loading options depending on the needs of the app.
Wouldn't surprise me it it came to him when he pushed in a gas powered tool's fuel primer bulb, 'priming' his inventor's 'light bulb'. 😉
GM
I think I understand as far as the horn has a decreasing cross-section/restriction (that also functions as a low-pass) that also contributes to acoustic mass. But I' still can't figure what "opening on the side of the cabinet" is.
Thanks for the great book recommendation. I will check it out.
Giri,
The "opening on the side of the cabinet" is the mouth of the horn, which has a smaller exit area than the interior cross-sectional area at that same point.
As an example, if the BDEAP (45" x 45" x 22.5" exterior dimensions) was split into two horns along the dotted line, and the exits were in the same plane as the drivers, each of the two mouths would be approximately 22.5"x 27", while "on the side", the exits for both only comprise a single 22.5"x 22.5" exit, less than half the exit area.
Art
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