10 speakers in series/parallel? Dodecahedron design.

[crinklecut]

Re: 10 speakers in series/parallel? Dodecahedron design.

I currently have a 5V BT module on hand, which I'll be adding inside the case. Would it be possible to run it off the 5VGEN pin of the amp, or should I run it off the battery with a voltage regulator?

I imagine running off a regulator would create lots of heat.

[crinklecut]

Re: 10 speakers in series/parallel? Dodecahedron design.

I don't live in the states, but I'm sure pillow stuffing won't be an issue Thanks!

[Chris Roemer]

Re: 10 speakers in series/parallel? Dodecahedron design.

Acoustic stuffing is just the "polyfill" found in your typical pillow (can be bought at Wal*Mart). Fiberglass insulation works just as well (but it's a little pickier).

[crinklecut]

Re: 10 speakers in series/parallel? Dodecahedron design.

I drew up a rudimentary model in sketchup so my idea becomes a little clearer:



I'm not sure what the final colour or button cluster at the top will be like, but this is a pretty good idea of what I'm going for (:

The empty faces are meant to have speakers on them. I got lazy to draw them all, but I hope you guys get the idea!

[crinklecut]

Re: 10 speakers in series/parallel? Dodecahedron design.

Yeah, I did take note of acoustic stuffing. The instructables build used it, and I probably will too, if I can get my hands on it.

The phenomena you describe are interesting. Definitely see how it goes when it comes together.

I'm not too keen of having it being suspended on a pole, as I want it to have some degree of portability/boombox kinda feel. If I have 9 drivers, the pole won't be necessary unless I want to get a more advantageous listening position.

I won't be able to put this together that quickly though. I'm in the middle of mandatory national service, which means my hands are pretty much tied on weekdays :( I'm still very much planning and getting a feel for the project direction.

Rest assured I'll be updating this thread when I start doing some real work.

[1100xxben]

Re: 10 speakers in series/parallel? Dodecahedron design.

If still want to use 10 drivers and can find a suitable 16 ohm driver, you can run them in series pairs, and all 5 pairs in parallel to bring you to 6.4 ohms nominal.

If you're looking for flat response, you're most likely going to need some EQ at the low/mid freq. You'll actually need some "reverse BSC". Each driver by itself will be fairly omni below 1 khz, especially below 500 Hz. With that many drivers in an "omni" configuration, they will all contribute to output as all drivers will be summing together in all directions. So, when standing at a specific point and listening to the speaker, you will have all 9 or 10 drivers contributing to the low end, and somewhere around 1-3 contributing to the high end where the individual speakers are very directional. This will give you a pretty big boost at the low end.

Another phenomenon you will probably notice is a dip somewhere in the 600-1000 Hz range which is dependent on the diameter of the enclosure. The drivers will still be radiating omni, but the drivers on the back-side will be out of phase with the drivers on the front in relation to the listening position, so there will be some amount of cancellation there resulting in a dip in the FR.

Also make sure you use some acoustic stuffing in the enclosure to minimize back-waves from opposing drivers. If you don't, you may see some dips in the upper frequency response due to back-waves being out of phase.

I agree with jhollander that this could be a cool project. I think a 9 or 10 driver "ball", pole mounted on top of an appropriate sized sub could be a sweet speaker to put out in the middle of your back-yard.

[crinklecut]

Re: 10 speakers in series/parallel? Dodecahedron design.

The PE t- amp in the podzuma would work

http://www.parts-express.com/dayton-audio-dta-2-class-t-digital-audio-amplifier-module--300-385

There’s also a video at PE for using the t-amp
Podzuma link for battery info

http://www.parts-express.com/project-gallery-speaker-project-the-podzuma

3 parallel groups of 3 series- 4 ohms woofers results in 4 ohm.

The will be some BSC as the woofer is not a perfect point source and this not a perfect sphere. I think that’s worthy of measuring as many people are looking for a full range no x-o option.

With an open facet this could get a port… I’m starting to like this project.

Those are some really useful links, thanks!

I'm not sure what the impedance of my speakers will be - I haven't found suitably efficient 3" full ranges that fit my budget.
I'm not going to splash nearly a hundred on speakers I don't have confidence will work out.

On that note, how would you suggest splitting the two 15W channels across 3 parallel sets of 3 series?
Any recommendations on cheap and cheerful drivers, even if they're not from PE?

All the help is incredibly encouraging (: I'm glad I joined this community. Thanks loads!

[jhollander]

Re: 10 speakers in series/parallel? Dodecahedron design.

The PE t- amp in the podzuma would work

http://www.parts-express.com/dayton-audio-dta-2-class-t-digital-audio-amplifier-module--300-385

There’s also a video at PE for using the t-amp
Podzuma link for battery info

http://www.parts-express.com/project-gallery-speaker-project-the-podzuma

3 parallel groups of 3 series- 4 ohms woofers results in 4 ohm.

The will be some BSC as the woofer is not a perfect point source and this not a perfect sphere. I think that’s worthy of measuring as many people are looking for a full range no x-o option.

With an open facet this could get a port… I’m starting to like this project.

[ngjockey]

Re: 10 speakers in series/parallel? Dodecahedron design.

Do omni's need BSC?

[crinklecut]

Re: 10 speakers in series/parallel? Dodecahedron design.

I'll have to find a suitable amp/speaker pairing! Till then, I think I'd prefer an array of 9 speakers, with 3 empty faces for controls, inputs, stand/base, and a handle. I kinda want the finished product to have a carry-around boombox feel, great for outdoor bbqs and the like.

Are there powerful enough little amp boards for a 9x 3W load? I guess I could place battery packs at the bottom of the unit, resting on the silicon/rubber base for stability.

[jhollander]

Re: 10 speakers in series/parallel? Dodecahedron design.

You could reach 10 ohms using 10 four ohm drivers.

+1, also the original 12 plus a threaded rod and 1 inch PVC stand. If your driving with a a battery powered amp may want to consider something less than 10 ohms.

[joeybutts]

Re: 10 speakers in series/parallel? Dodecahedron design.

Ping! cptomes

I bet he'll be able to help you....
Wolf

Def.

[blur]

Re: 10 speakers in series/parallel? Dodecahedron design.

You could reach 10 ohms using 10 four ohm drivers. A series of 5 drivers makes 20 ohms, paralleling that with another group of 5 makes 10 ohms nominal. Don't know if this helps...

[crinklecut]

Re: 10 speakers in series/parallel? Dodecahedron design.

That's an interesting idea. I'll think about that I'm just afraid I won't be able to build a sturdy enough pole/stand for the job. It's meant to be quite rugged for outdoor use.

The idea I had was to have an empty top and bottom face, for button clusters and a stable rubber/silicon base. This would leave 10 facets for speakers.

Taking into account a 9 driver design, I could leave another down facing face empty for input/charging/etc.

My only concern with my idea is if there's any impact on sound quality with one of the drivers not having an opposing driver on an opposite face. Thanks for the suggestion, though!

[MGrant1957]

Re: 10 speakers in series/parallel? Dodecahedron design.

The instructables design has his mount at the apex of 3 baffles. If you keep the dodecahedron, you could mount yours on a pole at the bottom apex between 3 drivers and use your the 3 top baffles or 3 bottom baffles for mounting your input jack, on-off switch, and tone control/whatever. This way you won't be wasting power driving speakers that are pointed up at the ceiling or down at the floor. It would also allow you to use 9 drivers 3 parallel sets of 3 series drivers... I.E. 8 ohms.