Diffraction-optimized......

[lasse]

Hello,

For some time, I have had a thought that the next step for me, just gotten rid of the passive XO:s, is to do something about the box-shape of the speakers I build (again and again).

I stumbeled over this speaker from a few decades ago, swedish Mirsch now no longer in business I beleive.

What do you think? Is this worth the big effort? And HOW ON EARTH do you build the spheres in wood? Anyone knows?





Regards//lasse

[WayneN]

Re: Diffraction-optimized......

Hi Lassie,

I know that I saw a design with a sphere in it quite a while ago; I think it was done by either DanN or WayneW and CurtC or maybe Dave Pellerene? I’m sure someone here will remember. I imagine it will be a lot of work and very rewarding if you can manage to pull it off.

WayneN

[carlspeak]

Re: Diffraction-optimized......

I think the Swedish design is nice but a bit overboard with regards to mitigation of diffraction.
You can build a standard type of cabinet, but just round the corners or taper the shape in the area of the tweeter. Another key, is to offset the tweeter from the centerline about an inch or so. Don't go too far or you may be forced to build a mirror image pair.

[[email protected]]

Re: Diffraction-optimized......

your gonna need a big lathe. your could always do some fiberglass work or cut somthing in half and start removing mass from the inside. bowling ball. two wooder bowls glued together.

[maynardg]

Re: Diffraction-optimized......

http://www.geocities.com/cc00541/Exclamations.html

[davepellegrene]

Re: Diffraction-optimized......

Something like this. This one is only $850. Fiberglass resin and cloth over top?

[dlr]

Re: Diffraction-optimized......

Hello,

For some time, I have had a thought that the next step for me, just gotten rid of the passive XO:s, is to do something about the box-shape of the speakers I build (again and again).

I stumbeled over this speaker from a few decades ago, swedish Mirsch now no longer in business I beleive.

What do you think? Is this worth the big effort? And HOW ON EARTH do you build the spheres in wood? Anyone knows?

Regards//lasse

Short of a _good_ coaxial or a waveguide, that one is probably one of the best for diffraction control. It may have drawbacks, however.

The downward angle of the midrange may provide more floor reflections that could affect the room power response once the listening axis is equalized, but room placement and treatment may make it a moot point.

There will be strong reflections from the lower woofer box. That angle cut section of the woofer box looks like it would be more reflective towards the listening position than a normal rectangular box with short time delays affecting the first arrival perception. The floor reflections, outside of power response, will also be stronger due to the angle. Some kind of carpeted floor would be necessary, I would think.

The midrange enclosure (the sphere) is actually one of the worst shapes for internal dimensions, so I would never use that shape other than for a tweeter.

As has been pointed out, a normal box with large roundovers (e.g. Thiel) will be nearly as effective as a sphere. But if you like the looks of the unit pictured, you can find ways around the issues, though I would still recommend against the sphere as a box for a midrange unit.

All of this assumes that you also don't want to use felt for diffraction control that allows for more baffle shape options while still controlling diffraction.

dlr

[Sibelius40]

Re: Diffraction-optimized......

Hmm...while I am sure they would sound good, I might not like looking at two of these after a while - they remind me of wooden versions of that robot in Rocky IV. (Happy Birthday, Paulie...)

[curt_c]

Re: Diffraction-optimized......

The midrange enclosure (the sphere) is actually one of the worst shapes for internal dimensions, so I would never use that shape other than for a tweeter.

As has been pointed out, a normal box with large roundovers (e.g. Thiel) will be nearly as effective as a sphere. But if you like the looks of the unit pictured, you can find ways around the issues, though I would still recommend against the sphere as a box for a midrange unit.

dlr

Au contraire, mon ami...

Having done several designs using spheres, I can say that the sphere is one of the best shapes I have ever heard for diffraction control and box resonance. Thanks to Wayne's hard work in building the sphere's, -This is how Wayne and I started out together BTW- Wayne has this killer OW1/Accuton 3 way that needed a crossover. Of course, back then I told him that spheres would never work. (Until I heard them.) -That design is still our benchmark for SQ.

The benefits of a sphere for diffraction effects are obvious, but what is not it its apparent lack of resonance and standing waves. The 'boxy' sound of a comparable rectangular box simply doesn't exist. Part of this of course is the lack of panel resonance due to the shape, but part of it is the lack of standing waves. Yes, I know this statement flies in the face of conventional wisdom, and I was in the other camp as well until my ears told me different. I have to give Wayne credit for seeing his sphere project through, in spite of the criticism his idea garnered on the boards back in the day...

We've done 5" drivers in 12" spheres, and 6.5" drivers in 17" spheres. Both have worked equally well regardless of the drivers utilized. Vifa PW17, RS180, C-82's, C-92's, to name a few.

I'd love to demonstrate them someday at your DiyNE, -What do you think Homeland Security would do if I tried to bring 2 17" black spheres as carry ons? :eek::eek::eek::eek:

C

[bearberry]

Re: Diffraction-optimized......

Check this thread:

http://www.diyaudio.com/forums/multi-way/159151-ikea-spherical-speakers-first-build-done.html

On using IKEA bowls and other found spheres.

bb

[dlr]

Re: Diffraction-optimized......

I'd love to demonstrate them someday at your DiyNE, -What do you think Homeland Security would do if I tried to bring 2 17" black spheres as carry ons? :eek::eek::eek::eek:

C

If you ever have the opportunity to make it to DIY NE, by all means do so, even if you have to come empty-handed. If you can bring the speakers, just don't have the speaker wire connected from the binding posts to a small, black DIY amp box.

And no carry-on, of course. ;) But then you'd have to rely on the strength of the spheres being able to take the thrashing that occurs in checked baggage.

dlr

[lasse]

Re: Diffraction-optimized......

Au contraire, mon ami...

Having done several designs using spheres, I can say that the sphere is one of the best shapes I have ever heard for diffraction control and box resonance. Thanks to Wayne's hard work in building the sphere's, -This is how Wayne and I started out together BTW- Wayne has this killer OW1/Accuton 3 way that needed a crossover. Of course, back then I told him that spheres would never work. (Until I heard them.) -That design is still our benchmark for SQ.

The benefits of a sphere for diffraction effects are obvious, but what is not it its apparent lack of resonance and standing waves. The 'boxy' sound of a comparable rectangular box simply doesn't exist. Part of this of course is the lack of panel resonance due to the shape, but part of it is the lack of standing waves. Yes, I know this statement flies in the face of conventional wisdom, and I was in the other camp as well until my ears told me different. I have to give Wayne credit for seeing his sphere project through, in spite of the criticism his idea garnered on the boards back in the day...

We've done 5" drivers in 12" spheres, and 6.5" drivers in 17" spheres. Both have worked equally well regardless of the drivers utilized. Vifa PW17, RS180, C-82's, C-92's, to name a few.

I'd love to demonstrate them someday at your DiyNE, -What do you think Homeland Security would do if I tried to bring 2 17" black spheres as carry ons? :eek::eek::eek::eek:

C

Hello and thanks for all the feedback. (and especially Curt)

This encourages me to build something like this in the future. The IKEA-idea is very nice-sounding to a Swede, you know.

Regards//lasse

[3way]

Re: Diffraction-optimized......

Take a look at the B&W sphere + rear tapered tube for the midrange and tweeter. The Nautilus series uses this technology. From my experience it is very important to absorb the rear wave in boxed midrange and tweeter designs, as well as to minimize box resonances. Rear wave reflections back to the cone are powerful and audible. I think the physics behind expanding the rear wave into a sphere and then using a stuffed tapered rear tube to absorb the energy with minimum resonance is good science.

http://www.bowers-wilkins.com/display.aspx?infid=1579

There is also a growing group that are building minimum baffle (nude) dipole speakers for similar goals.

[David Crewe]

Re: Diffraction-optimized......

The Gen-II's are comming along nicely.

[critofur]

Re: Diffraction-optimized......

, though I would still recommend against the sphere as a box for a midrange unit...

I'm kind of surprised you would say that Dave - I believe a sphere can actually be a good mid/full range enclosure.