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-   -   Concept, Beolab 11 style isobaric sub using Ikea Blanda metal bowls. (http://www.diyaudio.com/forums/subwoofers/215003-concept-beolab-11-style-isobaric-sub-using-ikea-blanda-metal-bowls.html)

Studio Au 23rd June 2012 03:40 PM

Concept, Beolab 11 style isobaric sub using Ikea Blanda metal bowls.
 
https://dl.dropbox.com/u/1444609/diyaudio/Ik%20Sub.jpg

2x10" drivers running in isobaric configuration, using MiniDSP for crossovers,

Housed in two attached, sealed 36cm Ikea Blanda bowls. A wooden frame would hold a detached granite slab for the bowls to sit on, spikes in-between the ground/wooden frame & granite/metal bowls.

Thoughts?

eXa 24th June 2012 11:02 PM

How do you get it to be isobaric?

NEO Dan 24th June 2012 11:36 PM

The depiction appears to be of the push push variety with the bowls connected at the bottom. Push push being a force cancellation strategy would not require the granite...

Studio Au 25th June 2012 11:52 AM

Yes they would run push pull. If im right in thinking this allows the cabinet size to be half of the recommended size.

My hi fi racks and orb like speakers all sit on granite (kitchen counter savers sm 4 lrg 9) these help to isolate vibrations and give a sturdy base thats cheaper than the oak, really flat and really stable.

For 20 on metal spun bowls, 9 granite, 4 spikes and 6 oak with a small sheet of mdf, 45 +/- I think I could be a great sounding and looking enclosure.

Looking at the peerless xls 10". Any have any idea how to model this?

Studio Au 25th June 2012 12:16 PM

Ps. This design also only needs two holes cutting in a round piece of mdf. With a good router it could be constructed within a hour or two.

d1030180 25th June 2012 12:24 PM

Quote:

Originally Posted by Studio Au (Post 3071688)
Yes they would run push pull. If im right in thinking this allows the cabinet size to be half of the recommended size.

My hi fi racks and orb like speakers all sit on granite (kitchen counter savers sm 4 lrg 9) these help to isolate vibrations and give a sturdy base thats cheaper than the oak, really flat and really stable.

For 20 on metal spun bowls, 9 granite, 4 spikes and 6 oak with a small sheet of mdf, 45 +/- I think I could be a great sounding and looking enclosure.

Looking at the peerless xls 10". Any have any idea how to model this?

Maybe you could also consider Scan-Speak 26W/4558T00 in addition to Peerless 10" XXLS/835016. The Scan-Speak has a lower free-air resonance frequency and might achieve lower total Q in a similarly sized enclosure.

http://www.scan-speak.dk/datasheet/pdf/26w-4558t00.pdf

djk 25th June 2012 01:28 PM

"If im right in thinking this allows the cabinet size to be half of the recommended size. "

Sorry, that's not isobaric. The drivers will have to work in whatever size the bowels are. I would run them Push-Pull and use a Linkwitz transform.

planet10 26th June 2012 03:13 AM

Quote:

Originally Posted by djk (Post 3071794)
I would run them Push-Pull

To be isobarik the drivers need to be couple together driving the same volume (with a small coupling cavity between the 2 drivers (ie 2 drivers act as a single compound driver). I can dig out pictures to illustrate if necessary.

I would go push-push over push-pull (cancelling 2nd order without doing anything about 3rd order creates a non-monotonic series of harmonics). Besides, push-pull probably wouldn't fit this configuration of half-spheres.

dave

Studio Au 26th June 2012 07:53 AM

Ok thanks Dave, let me try and be clear, as my understanding seems to be way off.

My goals were to try and design a sub, using two drivers to cancel/dampen each others forces, making a non-vibrating cabinet (within reason). And I believed that you could use two large drivers running in push-pull our isobaric to allow for a far smaller cabinet than if run normally (or a far bigger driver)

These bowls could be two separate sealed units, however joining them seemed to make more sense, a larger overall volume of air and the rear pressure form each driver canceled or balanced by the opposite movement of the other, as a passive radiator would work.

http://hem.bredband.net/filmtva/bb5.jpg

I saw these on the Voodoo thread, and thought they looked amazing, just didn't want to have to cut the metal, and thought this would lead to a more interesting design.

Am I right in thinking my sub would be omnidirectional? As its not got a baffle but is coming from a small slot.

Does anyone know how to model this?

planet10 26th June 2012 08:26 AM

2 Attachment(s)
Quote:

Originally Posted by Studio Au (Post 3072820)
Am I right in thinking my sub would be omnidirectional?

All subs are omnidirectional.

Isobarik will halve the volume needed for the same box Q, but one has to account for the overhead of the coupling chamber (or live with a magnet sticking out). A smaller coupling chamber is better.

http://www.diyaudio.com/forums/attac...1&d=1340699085

A single pair of drivers in an isobarik cannot be push-push -- well they can, but the complexity & end volume makes the point moot. To do isobarik and push-push you need 4 drivers (top figure).

http://www.diyaudio.com/forums/attac...1&d=1340699085

dave


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