DIY Omni Dodecahedron Speaker

[Naughtius]

Really cool! The in-room response looks surprisingly decent, but it doesn't look like it's happy playing below 200hz which is fine for voice, not great for music. I guess it's fit for purpose, though?

I'm also impressed at how fast you got this project done. Usually these DIY threads drag on for months or years...

In my head this was mids on up... based on your posted measurements I may have confused myself about how it would play out.

Thanks! Indeed decent, but not loud, and they are as you said not happy at all below 200Hz, even with the 12 of them together. The in-room response is also a moving mic method average, moving the mic across the sphere at about a 1 meter radius, so it's easy to miss a lot of the interference this way. Do you see more of what you expected in the second, raw, unfiltered response image? It is fit for its purpose.

It's about 80% done, which went surprisingly smooth for me as well - now that last 20%....

 

[Salt]

The response in room (moving microphone) is as to be expected, and sufficient for pleasant listening, and nobody would have expected any upper-to-low-bass from this construction.
If it's just for voice (0.1-4 kHZ) reproduction, it is sufficient at all.
Otherwise a/some sub/s would tweak it up to fullrange.
Great project!

 

[Phenoez8]

Took me a bit to find the tweeters, those are small! If you send me a STEP file I could run a quick simulation of what the radiation pattern would look like across the frequency range. Their baffles might also influence it a bit at the higher frequencies. Nice design with the passives in there.

Hello! Thank you so much for your offer to help! I just finished building this thing so it will be really interesting to see if your simulation can match measurements. I will send you the files in your DM.

 

[SivKiv]

@Naughtius This is probably way way too late, but have you considered those BMR drivers by the likes of Tectonic and Cotswold? Seems like a pretty decent driver that can go pretty wideband, but, I don't know if they'd be much better in the low frequency response, if at all. Although, as mentioned, maybe a configuration where this paired with a sub of sorts could possibly work, what do you think?

 

[Naughtius]

@Naughtius This is probably way way too late, but have you considered those BMR drivers by the likes of Tectonic and Cotswold? Seems like a pretty decent driver that can go pretty wideband, but, I don't know if they'd be much better in the low frequency response, if at all. Although, as mentioned, maybe a configuration where this paired with a sub of sorts could possibly work, what do you think?

It's never too late for another revision! I have checked them in the process, and I think the one I checked did have some more low end excursion range, but felt the wide high end radiation could make the comb filtering issue even worse than with conventional drivers.

I've done some more simulations since, and think making a teeny tiny 3/4"-tweeter ball, and putting a 6" high excursion woofer beneath that (LXMini style) would be another viable option, giving both a better high end as well as more low end.

Still gotta finish the amp and (internal) cabling for this one though, so it might be a while before another build.

 

[SivKiv]

It's never too late for another revision! I have checked them in the process, and I think the one I checked did have some more low end excursion range, but felt the wide high end radiation could make the comb filtering issue even worse than with conventional drivers.

I've done some more simulations since, and think making a teeny tiny 3/4"-tweeter ball, and putting a 6" high excursion woofer beneath that (LXMini style) would be another viable option, giving both a better high end as well as more low end.

Still gotta finish the amp and (internal) cabling for this one though, so it might be a while before another build.

I'd love to see results of the tweeter ball+woofer combo, could be a somewhat simple but neat Omni speaker. I do wonder though, how loud does you current design get at a meter before the speaker has THD at roughly 3% throughout most of the frequency response?

 

[SivKiv]

How's the build going so far?

 

[SivKiv]

A bit of a dead thread now, but I've recently been exploring creating a similar solution again, and I'm now wondering if I should have an array of 1 inch full rangers on a sphere, with a separate woofer component in a box below. The smaller size of the drivers should reduce CTC and in turn hopefully reduce HFs comb filtering, while the separate woofer component hopefully improves LFs extension by quite a bit and reduces IMD. Two things are that the woofer and sphere must be close enough for summation to occur at crossover, while also having the box be as acoustically unobtrusive as possible to minimise any diffraction that might occur from the HFs radiating from the sphere towards woofer's cabinet. Going for larger full rangers may allow a lower cross and further placement of the woofer cabinet, but would sacrifice the HFs Directivity pattern instead. It's tough balancing the compromises honestly I guess.

 

[kemmler3D]

It's tough balancing the compromises honestly I guess.

Speaker design in a nutshell I think.

 

[SivKiv]

Speaker design in a nutshell I think.

True hahaha

 

[kemmler3D]

True hahaha

I wonder if you could do a box-within-a-box to do something almost like the Genelec 3-way coaxial, with a <200hz driver inside the sphere with all the smaller drivers attached to the outside, with little slots between the small drivers for the bass to come out? I guess the slots would cause unpredictable port-like effects, but with enough DSP you could brute-force the response. So instead of putting the box below, you put it inside...?

 

[SivKiv]

I wonder if you could do a box-within-a-box to do something almost like the Genelec 3-way coaxial, with a <200hz driver inside the sphere with all the smaller drivers attached to the outside, with little slots between the small drivers for the bass to come out? I guess the slots would cause unpredictable port-like effects, but with enough DSP you could brute-force the response. So instead of putting the box below, you put it inside...?

That's an interesting solution that I really didn't think of. Question is, I'd probably need the box inside to be fairly large to meet the Vas of most woofers, and in turn the sphere itself also has to be larger. Not sure how I'd frame it inside either, and if it would interfere with whatever bracing that may be needed for the main speaker either. Will definitely have a look at it's feasibility though.