In an Olsen-Nagaoka design horn fold, is it the abrupt, sharp turns or the sharp edges of the material, or both, that help to decrease unwanted high frequencies from reaching the horn mouth?
Or put another way, is there any advantage or disadvantage to finishing the exposed edge of each interior horn panel with half-round material?
Thank you.
Or put another way, is there any advantage or disadvantage to finishing the exposed edge of each interior horn panel with half-round material?
Thank you.
Thanks for the prompt reply Chris. I would not for an instant challenge your greater knowledge and experience, and I have no scientific training, but the "good practice" part of your response strikes me as being counter-intuitive. It's difficult to understand how a sharp edge can add or subtract anything positive to the sound waves flowing through the horn.
It is because those sharp edges create some sort of turbulence that helps to thwart higher frequencies?
Hi, I think that's the idea behind it, read something similar recently. If that is the effect it does then make sense as the lower frequencies are less susceptible to being impeded in this way. I shall be interested to hear what Chris says
While I've had a few years of experience, be very careful how much knowledge you credit me with.
Yes, the turbulence - or perhaps destructive interference of high frequency standing waves/ reflections occurring between those succesive folds and parallel surfaces ? -would be my guess.
Truth be told, I can't immediately recall ever reading a technical explanation- and if I did, it would have been over my head. I'm comfortable enough trying to build a speaker enclosure from a set of dimensioned drawings, but the math /physics behind the design principles doesn't need to get very complicated before I'm completely lost.
Dr Scott, help a brother out
Yes, the turbulence - or perhaps destructive interference of high frequency standing waves/ reflections occurring between those succesive folds and parallel surfaces ? -would be my guess.
Truth be told, I can't immediately recall ever reading a technical explanation- and if I did, it would have been over my head. I'm comfortable enough trying to build a speaker enclosure from a set of dimensioned drawings, but the math /physics behind the design principles doesn't need to get very complicated before I'm completely lost.
Dr Scott, help a brother out
Thanks Chris. What you have said seems apt in describing the effect created by successive sharp, right angle folds in the horn (standing waves, reflections,etc.) but have you ever read or heard described what, if anything, the sharp edges of the interior horn fold panels are adding or subtracting.
My simple mind is thinking that the goal is to impede the high frequencies from reaching the horn mouth BUT at the same time to encourage and facilitate smooth passage for the desired low frequencies (perhaps by rounding off some sharp edges
My simple mind is thinking that the goal is to impede the high frequencies from reaching the horn mouth BUT at the same time to encourage and facilitate smooth passage for the desired low frequencies (perhaps by rounding off some sharp edges
Dr Scott, help a brother out
Well, kind sir, I shall do my best
Fund my mental lee, I agree.
I too am not one to measure things to death, when it comes to speaker design and implementation there are too many variables to make it an exact science in my view.
I would suggest that turbulence may not be a helpful way to visualise what is going on as, to me, this is like what happens when there is a constant flow similar to water in a stream, or here, a pipe.
Now, reflections, yes, they can cancel, and if we can arrange it so that we get destructive interference of the frequencies we don't want making it to the end of the pipe, all well and good, this could be accomplished with nasty angles!
Lower frequencies are simply not going to play ball
due to their longer wavelength and are only going to be interested in the length of the pipe.Regards my reading something similar recently, it was in this forum in relation to a TL, so, technically it was hearsay which would not stand up in court of law your honour.
Thanks Scott and Chris. If, over the years, many pairs of ears have concluded that the horns sound better with sharp interior edges, I am in no position to dispute that, even if the underlying physics cannot be completely explained.
There are many of things I don't understand but like a lot (my ex-wife for example
)
There are many of things I don't understand but like a lot (my ex-wife for example
)
Researched this a bit recently, and this was one of the more helpful articles I found: http://perso.univ-lemans.fr/~yauregan/publi/Bend_I.pdf
'Sound is round' and of course this sound 'bubble' gets exponentially larger with increasing frequency [F], so one has to look at the size of a frequency in relation to the horn's shape/area at any given point along its path. It becomes pretty obvious that most BLHs only have terminations big enough to pass the highest frequencies desired, so sharp bends even with sharp edges doesn't generate enough friction with [mid] bass size WLs to even 'tickle' them.
The smoother the bend in surface and contour, the smaller the F can 'roll' around it, but tighten it up enough relative to its size and it will reflect back to the throat [or previous bend], rattling itself to inaudibility unless 'fed' more of the same, so at some high frequency point of an Olson concept BLH it devolves into a series of resonant pipes.
In general this 1/2 WL BW should be limited to the horn's acoustic XO BW to get a good blend with the driver's forward radiation.
If the bends, terminations have sharp edges, then diffraction/reflection can occur over some range, again based on relative size, raising the F to a higher F with multiple much higher F that rapidly decay away in small horns, but usually need some damping in larger ones.
FWIW, don't recall pipe[horn] action being described as turbulent except in vortex designs, but then I'm not classically educated.
GM
The smoother the bend in surface and contour, the smaller the F can 'roll' around it, but tighten it up enough relative to its size and it will reflect back to the throat [or previous bend], rattling itself to inaudibility unless 'fed' more of the same, so at some high frequency point of an Olson concept BLH it devolves into a series of resonant pipes.
In general this 1/2 WL BW should be limited to the horn's acoustic XO BW to get a good blend with the driver's forward radiation.
If the bends, terminations have sharp edges, then diffraction/reflection can occur over some range, again based on relative size, raising the F to a higher F with multiple much higher F
FWIW, don't recall pipe[horn] action being described as turbulent except in vortex designs, but then I'm not classically educated.
GM
Hahaha! I did wonder WTF
. Doesn't sound like I was too far off the mark though. So pleeeeeease tell me I haven't embarrassed myself
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@BWRX: Thanks for that link. Extremely interesting, although I don't purport to understand the math and physics involved.
I note, however, that the experiments considered the effects of rounded vs. sharp outer corners in 90 degree bends (square and round x-section) with sharp inner corners held constant. I started this thread by asking about the effect of rounding the inner corners (using half round material, for example).
Nevertheless, what I think I gleaned from the article on a first read is that in a square x-section pipe, the rounded outer corners produced a more even, predictable result.
Of course, any particular iteration of an Olsen-Nagaoka horn could have the physics all wrong but still sound pleasing to a particular individual's ears)
I note, however, that the experiments considered the effects of rounded vs. sharp outer corners in 90 degree bends (square and round x-section) with sharp inner corners held constant. I started this thread by asking about the effect of rounding the inner corners (using half round material, for example).
Nevertheless, what I think I gleaned from the article on a first read is that in a square x-section pipe, the rounded outer corners produced a more even, predictable result.
Of course, any particular iteration of an Olsen-Nagaoka horn could have the physics all wrong but still sound pleasing to a particular individual's ears
)
Fortunately you don't have to know how to do the math, just how to read and interpret the results! I think the main takeaway is that the outer corner has more of an effect on the transmission and reflection coefficients than the inner corner, and rounded outer corners allow the transmission of higher frequencies with less attenuation because the wave is not reflected back as easily.
It's also worth noting that "Most of the experimental results presented were performed at frequencies in the 30-1000Hz range." (quote from page 1033 at the end of section 4).
Have you ever used Hornresp? If you haven't download it and have some fun with the wavefront simulator. You can make your own 2D horn path and watch how the wavefront propagates
It's also worth noting that "Most of the experimental results presented were performed at frequencies in the 30-1000Hz range." (quote from page 1033 at the end of section 4).
Have you ever used Hornresp? If you haven't download it and have some fun with the wavefront simulator. You can make your own 2D horn path and watch how the wavefront propagates
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@BWRX: Thanks for the link to Hornresp. I'm running Linux but it should run on my system using WINE. I'm going to be very interested to see the effect that various horn mouth sizes have on low frequency extension, especially for a rear firing horn when factoring in corner walls as part of the horn.
I'm no expert. In fact, profoundly deaf since birth. But I love good sound and respect the means to faithfully reproduce it.
Like the Front, the Rear has an Axis, where Beaming occurs. As Beaming occurs at narrower, shorter Wavelengths than those in desired lower register, one can effectively deflect Rear Beaming with methods Members have touched upon.
Though light wavelengths are not round, rather than extend a straight arm in hopes bright light will diffuse, one still effectively shields their eyes with a folded hand and/or arm against bright light, but can still see.
Like the Front, the Rear has an Axis, where Beaming occurs. As Beaming occurs at narrower, shorter Wavelengths than those in desired lower register, one can effectively deflect Rear Beaming with methods Members have touched upon.
Though light wavelengths are not round, rather than extend a straight arm in hopes bright light will diffuse, one still effectively shields their eyes with a folded hand and/or arm against bright light, but can still see.
If the principles discussed here hold true: regarding the sharp turns in a Olsen-Nagaoka design impeding the passage of higher frequencies along the horn, shouldn't the right angle deflector in the top/back of this horn be eliminated?
https://www.madisoundspeakerstore.com/full-range-speaker-kits/fostex-bk-20-folded-horn-kit-pair/
https://www.madisoundspeakerstore.com/full-range-speaker-kits/fostex-bk-20-folded-horn-kit-pair/
I see what you are saying. The effect it has on the reflections is going to depend on the angles they are striking at. By the time they get to that point I can envisage them being all over the place anyway and it could even be helping with further scattering if you look at it like that, I doubt it would make much difference either way. It probably functions as more of a structural brace.
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