For a guy like me who doesn’t need a driver to do much above 90db, and that’s actually with like 10db headroom, the bmr 2” is not the worst choice I could make in choosing a widebander. But there’s also the possibility of adding a small neo tweeter to play above 5khz right before the resonant modes start appearing. I wonder how the transient response of a 5/8ths soft dome would compare to a ribbon, planar, or amt. That’s saying that more than only a few people could tell the difference blindfolded from a tiny dome and a ribbon type transducer. That could also be an avenue for me to explore in getting everything into those premade black Dayton cabinets I like so much.
I’m quite good with fiberglass from my car audio interest and could easily fit the bmr 2” and tiny neo dome onto a 4.5” circle that fits the tweeter cutout and even point on axis if the response wasn’t already phenomenal from a tiny dome. But, the center to center spacing would still be far from a 1/4 wave at even a 2” c to c. This is fun.
I’m quite good with fiberglass from my car audio interest and could easily fit the bmr 2” and tiny neo dome onto a 4.5” circle that fits the tweeter cutout and even point on axis if the response wasn’t already phenomenal from a tiny dome. But, the center to center spacing would still be far from a 1/4 wave at even a 2” c to c. This is fun.
The Techtronics driver Erin measured does have decent low distortion, though. Around -50dB at 90dB 1m. I don't see a big jump where the resonant operation seems to start.
The jist of what @andy19191 and @planet10 are saying seems to be 'this is as good as they can get', right?
Perhaps line array is a very good build option for such drivers, sorting power handling and lowering distortion. Average of lobing might even be helped if each driver where rotated a little.
The jist of what @andy19191 and @planet10 are saying seems to be 'this is as good as they can get', right?
Perhaps line array is a very good build option for such drivers, sorting power handling and lowering distortion. Average of lobing might even be helped if each driver where rotated a little.
I’ve thought before about running 2x3 of the bmr 2” on the little Parts Express .04cf knockdowns I love so much. The high q of the 2” gets a little rowdy with 6 in .04cf but even with only three ~$25 they begin to become more realistic for more people spl wise, at least for a micro bookshelf like I’m going for here. 1/4 wavelength c to c is right at 7khz. I wonder how the polar world look, I don’t have any experience simulating arrays or clusters. A 3x6 cluster seems like it would reach darn close the limit of hearing with cabinet ear level and on axis.
There is a 1-3/4” bmr with a more pedestrian qts but I can’t find any measurements on it and those drivers seem like they can be all over the place performance wise. I enjoyed the 3.5” as a novelty when playing around with it in my .5cf cabinet with a 7” pr tuned in the very low 30’s. Volume limited to near field for sure at that tuning, but it was fun to listen to until I needed the cabinets for more official duties.
I haven’t played with the 3.5’s in at least two years but after seeing the measurements, I don’t have much urgency to make time to. I know very little about how the engineering goes to make those drivers work like they do but if the employment of the resonances lessened intermodulation, the 3.5” with it’s 5mm throw could be a decent competitor in the 3”-4” class. Unfortunately, it’s measurements are a dumpster fire…
https://hificompass.com/en/speakers/measurements/tectonic/tectonic-tebm65c20f-8
There is a 1-3/4” bmr with a more pedestrian qts but I can’t find any measurements on it and those drivers seem like they can be all over the place performance wise. I enjoyed the 3.5” as a novelty when playing around with it in my .5cf cabinet with a 7” pr tuned in the very low 30’s. Volume limited to near field for sure at that tuning, but it was fun to listen to until I needed the cabinets for more official duties.
I haven’t played with the 3.5’s in at least two years but after seeing the measurements, I don’t have much urgency to make time to. I know very little about how the engineering goes to make those drivers work like they do but if the employment of the resonances lessened intermodulation, the 3.5” with it’s 5mm throw could be a decent competitor in the 3”-4” class. Unfortunately, it’s measurements are a dumpster fire…
https://hificompass.com/en/speakers/measurements/tectonic/tectonic-tebm65c20f-8
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A 2" £1-10 driver is likely the commercial optimum. One can go large and more expensive to get some improvement but the use of resonances will always limit the achievable technical performance. About 20 years ago when there was more interest in bending wave speakers I attended an informal presentation of a large DIY/prototype in a medium sized lecture room. It sounded fine with percussion and one or two instruments (e.g. the inevitable Stimela) but the designer with a smile refused to play orchestral music.