I am working on a small home audio project which I think contains an interesting and challenging physics/audio engineering problem which I have zero knowledge of how to solve.

The speaker driver is facing downwards, and I want to design a cone which points upwards towards the driver so that the sound is redirected as efficiently as possible in all radial directions. I also would like to minimise the space between the cone of the driver and the base of the "redirection" cone as much as possible.

I suspect that this may be a complex set of calculations and may not be possible, in which case I'll try various designs. But having even a ballpark estimate of the required dimensions and spacings would be extremely useful.

The driver I am using is a Dayton Audio RS100-4. It is being mounted on a panel of radius 100mm.

I realise this question is likely to be marked as too broad and I am happy to add further details as required. Fact of the matter is that I don't know what information is required to tackle the problem and/or aid comprehension.

Thank you.

  • I suggest you start perceiving the world in wavelengths. Start with lambda = c/f, where c is the speed of sound and f is frequency. Yes, distances do vary in this world. Next recall interference and wave effects. Finally, make very big doubts about your project, once you factor in 3D standing waves in your room, and their effect on perceived sound.
    – MS-SPO
    Jan 2 at 15:47

1 Answer 1


Aside from downward facing subwoofers, where there is not really a need for a diffuser, the only "audiophile-ready" loudspeaker that is similar to what you ask is the Citation X by Harman Kardon.

It didn't use a parabolic diffuser attached to the surround, but has this strange shape attached to the speaker cone - part of the profile is rather close to a parabola:

enter image description here

Full article that picture is taken from is on Roger-Russell.com - which also talks about the specific requirements and some of the tech decisions made.

As reflection from a surround based diffuser will depend on the cone you use, the frequencies etc in use, I don't think you can get a perfect design, so you may be best off assuming a paraboloid coin is a reasonable simple fit and avoid the challenge of trying to create a "best" fit. In my experience, even a normal cone will probably do the job sufficiently well.

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