Exceptional performance - again, despite the tiny Sica's radial phase plug and especially considering its price.
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Now I prepare a free standing waveguide for BMS 4554, ⌀370 x 120 mm. This is 1.4" driver nominally but it has aboout 40 mm of conical exit (~26°), i.e. the actual driving area is quite small, only about ⌀17 mm.
This is a simulation including the conical exit section (as shown before, there's still a reflection apparent in the impedance data due to the wavefront mismatch).
This is a simulation including the conical exit section (as shown before, there's still a reflection apparent in the impedance data due to the wavefront mismatch).
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Just so we dont get to carried away... Bliesma T34A-4 @ BlieSMa T25A-6, T25B-6, T25D-6, T25S-6 | HiFiCompass
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This is the detail of the driver/horn interface (approx. in the middle of the picture). Even this change of curvature causes an impedance mismatch.
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Hi, is a flat wavefront from driver best (or the only) way to get smooth impedance match to a horn? If there is conical extension with the driver the wavefront can't be flat? Just trying to understand if there is already some kind of rule of thumb to narrow down good drivers for ath generated horn that would match simulations well 
No no, not at all. I stated that only for completeness because at the moment flat wavefront is all I have implemented for the CircSym. Flat wavefront is the right shape to drive an OS waveguide (without any reflection). For example it would be spherical wave for a conical waveguide. In the presented case the conical exit is connected to something resembling an OS contour so there's the mismatch.
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I plan to print several throat geometries and measure them with the drivers I have at hand to see if there's any real trend. For this even a very small waveguide should suffice.
- That all said, the reflection shown above really doesn't mean much in the overall picture. It has some minor effect on SPL but that's about it.
- That all said, the reflection shown above really doesn't mean much in the overall picture. It has some minor effect on SPL but that's about it.
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interesting... i used to think that the horn curvature of itself had a relationship to it's output but the problems it seems are all due to mismatch between driver and throat...sure wish there was a way to design a horn with a predictable response regardless of the source/driver wavefront shape.
Well, in fact this is the horn curvature. One has to look at the driver exit section (if there's a one) as an integral part of the horn. In the example above this whole composed contour is driven by an ideal flat wavefront. What's the actual wavefront, I don't know. I only know that the smaller it is the less critical it is.
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well it seems this problem goes back in time a long way because pre the late 70's it was excepted that mismatch between driver exit angle and horn was the domain of all horn sound problems...
and likely what lead to the mythology of some combinations of horn and driver being good sonically despite what the math says it should be.
and likely what lead to the mythology of some combinations of horn and driver being good sonically despite what the math says it should be.
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This is for a tubular extension inserted into the driver down to the phase plug exit.
If one was willing to compensate the strong resonance otherwise it's pretty good
If one was willing to compensate the strong resonance otherwise it's pretty good
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