Aadams Posted March 1, 2019 Report Share Posted March 1, 2019 I just noticed this today. Boston CR65 nominal 5 inch cones have a dust cap that is not like any dust cap on any speaker I have ever had. Notice the photo below: The bullet shaped dust cover remains stationary while a sleeve on the cone moves over it. Is this a common construction these days. The cone driver crossover is 4200hz, about 1khz higher than the point where it would become beamy using the 13560 rule. Does anyone know the purpose of this form of design? Just curious. Link to comment Share on other sites More sharing options...
ligs Posted March 1, 2019 Report Share Posted March 1, 2019 My Dayton RS 225 -4 8" woofer looks like this too. Usually it is called a phase plug. Not sure it is essential for good sound. Link to comment Share on other sites More sharing options...
Aadams Posted March 1, 2019 Author Report Share Posted March 1, 2019 1 hour ago, ligs said: Usually it is called a phase plug. Not sure it is essential for good sound. Thanks. I have been reading about phase plugs. Apparently it permits even higher crossover points before beaming becomes a problem. I couldn't find much on it but the stationary hard surfaced plug seems to scatter frequencies with wavelengths less than the width of the cone that would otherwise beam out from the center if there were a fixed dust cap. I don't really know what I am talking about but that is what I picked up from several hits regarding cone mid woofers with phase plugs. Adams Link to comment Share on other sites More sharing options...
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