Something to read on Audio Junkies about spherical enclosures and diffraction

Original linked thread

They're talking about it in terms of car audio, but I was wondering how much research Axiom has done with this in home audio applications? Anyone know if they've dabbled?

I've wondered if Axiom has ever tried anything with composites. While they get great sound from MDF boxes, I wonder what they could do if not limited to a flat front baffle.

While it gets pretty expensive when working in wood to get nice compound curves, it's nothing to lay out fiberglass or carbon fiber on a mold and get any shape you desire.

In my car circle, our group pushed a guy with slight aspirations of making custom body panels to go with it, and get the equipment to do carbon fiber. He actually was surprised how easy it was once he got into it.

It might be a little difficult to build the entire enclosure, and get the rigidity needed for the bass drivers, but as shown in the links above, a hybrid design with the tweeters in the composite enclosure attached to a more traditional box to hold the parts more likely to shake things up. Still could have a waveguide diffractor glued to that too.

That sounds like a nice recipe for a new Axiom speaker.

By the way, it's your birthday? Happy Birthday, Chris! I guess you should have a thread in the Water Cooler.

I know the reason Axiom does not use a box shaped speaker as the article mentions, and does use their current wedge designed cabinet, is to help eliminate the standing wave issue. They put many years of research into this design. Also, they use a meatallic dome in their tweeters to keep a consistant sound stage dispersion.

On any of the DIY sites such as Solen or Parts Express, you can see a number of tweeters and midranges with tapered tubes or cones attached to them to combat standing waves. This is also why you see some rather odd looking cabinet designs such as pyramids, aside from tapered, curved or ellyptical designs. Others use an angular shape within the cabinet, unseen from outside.

The Jamo 707i's I just sold had the elliptical sides on them like this ( ) It was for the same reason as Axiom to eliminate standing waves. I wonder if they helped with diffusion though since the front was flat for about 2 inches on either side of the drivers.

Hi Sloped and all,

Note that the front of Axiom speakers has rounded (chamfered?) edges that run the entire length of the enclosure, to address edge-diffraction effects. It's quite important and most careful designers approach this with different techniques.

By the way, an acquaintance of mine who ran a small Canadian speaker company for a short time back in the late '70s claimed that the best-dispersed highs he ever achieved was by suspending two raw tweeters from the ceiling using nylon fishing line. The wires from the tweeters led to a module below that contained the woofer and midrange drivers.

I never heard the setup or tried it myself, but I was always intrigued by the idea. . .

Regards,

Alan, I remember reading somewhere that there was a minimum radius/chamfer that was required to address the edge diffraction issue....something in the neighbourhood of a 1" rad min? I guess it would have to do with the higher freq's wavelengths?

Definitely has to do with the short wavelengths of high frequencies. For more detail, I'd have to consult with Ian.

Regards,