https://www.erinsaudiocorner.com/driveunits/tectonic-elements-tebm35c10-4-miniature-bmr-driver/
Round enclosure, 6 opposing drivers would be interesting.
When they are close together and driven with identical signal there’s noticeable comb filtering when using pink noise, but not with music.
Round enclosure, 6 opposing drivers would be interesting.
When they are close together and driven with identical signal there’s noticeable comb filtering when using pink noise, but not with music.
It's still there with music but perhaps you can't detected it!? Or anyone else for that matter....
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It is indeed possible to place the drivers in a smaller enclosure. That will then have a different shape, f.i. a truncated tetrahedron. Volume then can be reduced by a factor of 4. But Qtc becomes then undesirable high. So you have to find extra voulume elswere or take smaller dirvers like the 2" DMA58-8.
Interesting suggestion, maybe I'll give it a try. However, I really have no idea what to expect.
What do you mean by measuring with both poles ?
Might well work. Is this your own hardware ?
But I don't think this is an omni directional speaker and is therefore outside the scope of my project.
Also the omni's I made it give excellent sound repoduction despite the combing. The problem I want to solve is the not optimal stereo separation.
It’s a work mate’s he bought the speakers and I did the rest. We made it as a joke.
We use omnidirectional speakers from norsonic in our work for room acoustics and this little one is quite similar to one of theirs.
We use omnidirectional speakers from norsonic in our work for room acoustics and this little one is quite similar to one of theirs.
It’s not really round, it is a dodecahedron. A dozen pentagons with a driver sitting in each one.
dave
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Once 3 indirekt speaker in the phase(exsisting) and another time out of phase. In the phase You should have combs and out of phase combs should disappear(almost). You should try 6 dB crossover 200Hz? for direct and 1-2kHz for indirekt speaker, as You need attenuation for indirekt speakers You can wire this in parallel with series resistor and with parallel direct speaker that should be 4 Ohm. Measure that with all room modes(no time gate) and above 1kHz with indirekt speakers Spl should be maximal 2dB higher with the same linearity as without ambiental. Measure on listening position - You need room reflections for correct result.
Hmmm i like the idea of letting the motor stick out for increased heat dissipation. I haven’t smoked a coil yet but it definitely have happened.
I never seen this brand/model before.
The test signal is usually loud pink noise and can in some cases be on for an extended period of times if we are measuring the sound transmission thru walls or floor/ceiling.
From the REW measurements, I noticed that at certain orientations of the omni, the SPL function is quite flat up to 4.5 kHz and plunges steeply downward above that.
photo taken from mic position
If we add tweeters we could get an acceptable SPL in at least one direction, that is towards the listener at the sweet spot.
We can try mounting tweeters on the four empty hexagons. In doing so, the speaker still meets the criteria for an omnidirectional speaker.
Artist impression of the simulated configuration.
for the DA175-8 the factory on-axis fdr was used.
for the DMA70-8 the SPL measured with REW is used (see above) + 6 dB
for the ND13FA-4, the factory 30-degree off-axis fdr was used
I simulated the following circuit with all drivers in the origin:
The resulting SPL from the simulation already looks very promising. The energy frequentie response is also pretty beefed up.
However, even if this approach works in practice, I expect there is still much to be done to achieve optimal results. This means a lot of measuring to find the best orientation for the omni and optimizing the filter. But it could be a winning approach.
Note: as an alternative, consider a tweeter on each of the six squares.
photo taken from mic position
If we add tweeters we could get an acceptable SPL in at least one direction, that is towards the listener at the sweet spot.
We can try mounting tweeters on the four empty hexagons. In doing so, the speaker still meets the criteria for an omnidirectional speaker.
Artist impression of the simulated configuration.
for the DA175-8 the factory on-axis fdr was used.
for the DMA70-8 the SPL measured with REW is used (see above) + 6 dB
for the ND13FA-4, the factory 30-degree off-axis fdr was used
I simulated the following circuit with all drivers in the origin:
The resulting SPL from the simulation already looks very promising. The energy frequentie response is also pretty beefed up.
However, even if this approach works in practice, I expect there is still much to be done to achieve optimal results. This means a lot of measuring to find the best orientation for the omni and optimizing the filter. But it could be a winning approach.
Note: as an alternative, consider a tweeter on each of the six squares.
Hello Dave,
My crossover is still passive.
Do you know how to build a Linkwitz Transform function into a passive crossover crrcuit ?
I am looking into building a truncated dodecahedron ESL. I'm still working out some of the details and working on fixtures for assembling the drivers and the speakers. The plan is to make the drivers 200 mm diameter using 3D printed ABS frames for each. There will be a plastic or metal tube up the center to run wires from the transformers and bias supply in a box below the speaker. I will attempt to seal the enclosure as it gets assembled. Currently planning on making two 6 driver subassemblies and joining them as a last step.
I have printed some 80 mm versions of the driver frames and a gluing jig to assemble them into a model that will tell me if the 3D printer is accurate enough before I go full size. The jig clamps three of the driver frames together at a time. Initial tests look good. I used Fusion360 with a polyhedron plug-in to get the basic shape and all the angles. The real trick will be getting the angles accurate enough that the assembly process won't flex the drivers and cause the diaphragms to wrinkle.
I'll be using wire window screen for the stators with 1.5-2 mm spacing, unless I can locate some cheap source of perforated aluminum or steel discs. Using screen may limit the bias voltage and sensitivity of the speaker. I'll use 6um polyester film for the diaphragms with Licron coating.
At 200 mm dia., with 12 drivers, the total radiating area will be about 337k sq mm, equivalent to a 613 x 613 mm driver, so it should be capable of reasonable SPL, and relatively wide frequency response. A subwoofer will deliver the lowest frequencies. The driver size will tend to beam the high frequencies a bit, but the truncated dodecahedron will allow pointing one driver directly at the listener.
Once I'm working on the actual speaker I'll start a separate thread to update progress.
I have printed some 80 mm versions of the driver frames and a gluing jig to assemble them into a model that will tell me if the 3D printer is accurate enough before I go full size. The jig clamps three of the driver frames together at a time. Initial tests look good. I used Fusion360 with a polyhedron plug-in to get the basic shape and all the angles. The real trick will be getting the angles accurate enough that the assembly process won't flex the drivers and cause the diaphragms to wrinkle.
I'll be using wire window screen for the stators with 1.5-2 mm spacing, unless I can locate some cheap source of perforated aluminum or steel discs. Using screen may limit the bias voltage and sensitivity of the speaker. I'll use 6um polyester film for the diaphragms with Licron coating.
At 200 mm dia., with 12 drivers, the total radiating area will be about 337k sq mm, equivalent to a 613 x 613 mm driver, so it should be capable of reasonable SPL, and relatively wide frequency response. A subwoofer will deliver the lowest frequencies. The driver size will tend to beam the high frequencies a bit, but the truncated dodecahedron will allow pointing one driver directly at the listener.
Once I'm working on the actual speaker I'll start a separate thread to update progress.
Mine will be a complete sphere with 12 drivers:
AFICT, the fusion360 plugin generates polyhedra of a specific size of its own choosing, and you have to scale it to the final size you want.
In the image below the blue piece is the gluing jig that holds three of the driver outer stators (red) together for gluing. The orange piece is one of the inner stators. These prints act as both structural elements and spacers for the stators. All the triangular pieces have matching pieces parallel to them on the opposite sides of the shape. One will have a hole for the wiring tube and the opposite one will have some receptacle for the end of the tube.
If I use screen for the stators I'll probably add some webbing to support the screen and keep it flat over the entire surface of the stator.
In the image below, the purple piece is a gluing jig for an individual driver. It is used to align the red outer stator and the orange inner stator. The diaphragm will be glued between them. I still have to work out the electrical contacts between the stators and diaphragms on both the inside and outside drivers.
I will also print triangular pieces to fit between the drivers. One of those will have a rigid tube (metal or PVC) running through it for the wiring to the transformers and bias supply.
Here's a picture of the test prints - both types of gluing jigs and the outer stators are shown:
I'm planning on gluing up two hemispheres then seeing how well the two match up when I try to put them together. These prints are made of PETG so I'll probably solvent weld them together using ethyl acetate. The final prints will be ABS and I'll look for an adhesive that can also seal the joints.
AFICT, the fusion360 plugin generates polyhedra of a specific size of its own choosing, and you have to scale it to the final size you want.
In the image below the blue piece is the gluing jig that holds three of the driver outer stators (red) together for gluing. The orange piece is one of the inner stators. These prints act as both structural elements and spacers for the stators. All the triangular pieces have matching pieces parallel to them on the opposite sides of the shape. One will have a hole for the wiring tube and the opposite one will have some receptacle for the end of the tube.
If I use screen for the stators I'll probably add some webbing to support the screen and keep it flat over the entire surface of the stator.
In the image below, the purple piece is a gluing jig for an individual driver. It is used to align the red outer stator and the orange inner stator. The diaphragm will be glued between them. I still have to work out the electrical contacts between the stators and diaphragms on both the inside and outside drivers.
I will also print triangular pieces to fit between the drivers. One of those will have a rigid tube (metal or PVC) running through it for the wiring to the transformers and bias supply.
Here's a picture of the test prints - both types of gluing jigs and the outer stators are shown:
I'm planning on gluing up two hemispheres then seeing how well the two match up when I try to put them together. These prints are made of PETG so I'll probably solvent weld them together using ethyl acetate. The final prints will be ABS and I'll look for an adhesive that can also seal the joints.
Thanks - very impressive - please make sure to start a dedicated thread for this very interesting project and unique project...pretty please - so that we may follow its progression and finalization.
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Surely this is further mimicking what happens with a live instrument, and therefore beneficial to the impression of realism...
The frequency response of any room at the listener's ears can never be flat, and is different at each ear. In my experience, the common obsession with ruler-flat response of everything, everywhere misses one of the most important aspects - that the room is part of the system. I guess that room treatments (especially diffusers) just aren't cool. Perhaps it's also a WAF thing...