So, I saw these in the other post where they were used in OB. Looked them up, and the FR curve looked way too nice on their website, and the polars were amazing... I just had to get some, especially since they were shipping for free over here.
DIYAudio initial thread:
http://www.diyaudio.com/forums/full-range/314130-temb35c10-4-ob.html
BMR specs:
http://docs-asia.electrocomponents.com/webdocs/15b6/0900766b815b6e2c.pdf
Initial testing done online:
Tectonic Elements TEBM35C10-4 Miniature BMR(R) Driver | Medley's Musings
Got them in about 4 days, and geez, these things are small. Barely over the size of a tweeter. The 2" is actually the size of the driver, bezel included. The flat cone barely measures 1.25".
Here's a sample of me measuring them with DATS:
So, just like the initial DIYA thread, I mounted them on mini OBs and had a quick listen... not bad! Couldn't find screws small enough to fit these in my shed.. had to use tape to hold them! FR looked good, Impulse very good.
DIYAudio initial thread:
http://www.diyaudio.com/forums/full-range/314130-temb35c10-4-ob.html
BMR specs:
http://docs-asia.electrocomponents.com/webdocs/15b6/0900766b815b6e2c.pdf
Initial testing done online:
Tectonic Elements TEBM35C10-4 Miniature BMR(R) Driver | Medley's Musings
Got them in about 4 days, and geez, these things are small. Barely over the size of a tweeter. The 2" is actually the size of the driver, bezel included. The flat cone barely measures 1.25".
Here's a sample of me measuring them with DATS:
So, just like the initial DIYA thread, I mounted them on mini OBs and had a quick listen... not bad! Couldn't find screws small enough to fit these in my shed.. had to use tape to hold them! FR looked good, Impulse very good.
Because these things have quite the low sensitivity, at 78-80dB, it would make sense using multiples to improve their rating.
I had ordered 4 of those little BMRs, so, they went on a mini OB. Now, they are about the same as a TC9... still not great, but useable.
Trouble is, the combing effect, starting at about 7kHz, with these when placed on that little OB was severe. Wasn't sure if it was the extreme dispersion these have, of if it was the backwave interfering with the higher frequencies. Probably a combination of both, since that little OB was so thin. a much wider baffle might help here.
Measurements so far have been at 1m, in front of the OB.
Last graph shows about 3.3m away, at the listening position on the couch. Still affected by combing there.
I had ordered 4 of those little BMRs, so, they went on a mini OB. Now, they are about the same as a TC9... still not great, but useable.
Trouble is, the combing effect, starting at about 7kHz, with these when placed on that little OB was severe. Wasn't sure if it was the extreme dispersion these have, of if it was the backwave interfering with the higher frequencies. Probably a combination of both, since that little OB was so thin. a much wider baffle might help here.
Measurements so far have been at 1m, in front of the OB.
Last graph shows about 3.3m away, at the listening position on the couch. Still affected by combing there.
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Alright, a small OB won't do it.
It was either a much larger baffle, of going sealed. Looked up WinISD and it said these need about 0.85 litres per driver. Made a quick 4-litre box, filled with polyfill, from scraps I had around.
Ha! Now we're getting somewhere. That took care of the combing.
The highs are limited in vertical dispersion, as it should be when drivers are mounted in line. But, the horizontal dispersion is phenomenal. My couch is 3m wide, and sitting in the middle or either ends of it, I could barely hear a shift in tone. Quite impressive.
Using the sealed box, I could reach down to 200Hz before it started falling. Measurements taken at 1m straight forward and at 45 degrees show the wide horizontal dispersion, which holds true at the listening position on the couch 3m away. And, no combing. Cool!
It was either a much larger baffle, of going sealed. Looked up WinISD and it said these need about 0.85 litres per driver. Made a quick 4-litre box, filled with polyfill, from scraps I had around.
Ha! Now we're getting somewhere. That took care of the combing.
The highs are limited in vertical dispersion, as it should be when drivers are mounted in line. But, the horizontal dispersion is phenomenal. My couch is 3m wide, and sitting in the middle or either ends of it, I could barely hear a shift in tone. Quite impressive.
Using the sealed box, I could reach down to 200Hz before it started falling. Measurements taken at 1m straight forward and at 45 degrees show the wide horizontal dispersion, which holds true at the listening position on the couch 3m away. And, no combing. Cool!
In the initial online testing of this driver, it was mentioned that distorsion becomes too much under 300Hz.
This begged for woofer support. I had a W8-1363SBF lying around, so made another quick sealed box with scraps and came up with a quick XO at 450Hz. Initially, I went with the Harsch XO, because it works so well with my present setup. However, here, things were a bit thin sounding. It was missing some energy.
I switched to 2nd order XO on both the mini array and the woofer. This brought back life to the music.
Used a little EQ to dial down 4 peaks , at 110Hz, 900Hz, 3000Hz and 5500Hz. Peaks were about 5dB each, so dialed down 5dB at those frequencies.
This got me a nice little FR that was pleasing to listen to.
This begged for woofer support. I had a W8-1363SBF lying around, so made another quick sealed box with scraps and came up with a quick XO at 450Hz. Initially, I went with the Harsch XO, because it works so well with my present setup. However, here, things were a bit thin sounding. It was missing some energy.
I switched to 2nd order XO on both the mini array and the woofer. This brought back life to the music.
Used a little EQ to dial down 4 peaks , at 110Hz, 900Hz, 3000Hz and 5500Hz. Peaks were about 5dB each, so dialed down 5dB at those frequencies.
This got me a nice little FR that was pleasing to listen to.
Attachments
Finally, I decided to A/B these 4 little BMRs array against a single TC9 in sealed box as well.
First impression, the BMRs are flatter than the TC9 when no EQ was used. Quite nice, considering many people are impressed at the TC9 flat response.
Then, I tried to EQ them the same, to within 1 or 2dB of each response. Quite time consuming to try to perfect two curves looking exactly the same!
When that was done, I thought the TC9 produced a livelier feel to the music than the BMRs, but not by much. Could have been the ceiling bounce of the TC9, compared to the narrower dispersion of the mini array, thus lessening the ceiling and floor bounce.
Graphs coming soon! Measurements were done on another computer than the one I'm writing with at the moment!
So far, I like these little BMRs. I'm thinking a small array of 9 drivers, sandwiched between two 8" woofers could be very nice. Even 6.6" woofers could do... the 8" seem so big compared to the little BMRs!
First impression, the BMRs are flatter than the TC9 when no EQ was used. Quite nice, considering many people are impressed at the TC9 flat response.
Then, I tried to EQ them the same, to within 1 or 2dB of each response. Quite time consuming to try to perfect two curves looking exactly the same!
When that was done, I thought the TC9 produced a livelier feel to the music than the BMRs, but not by much. Could have been the ceiling bounce of the TC9, compared to the narrower dispersion of the mini array, thus lessening the ceiling and floor bounce.
Graphs coming soon! Measurements were done on another computer than the one I'm writing with at the moment!
So far, I like these little BMRs. I'm thinking a small array of 9 drivers, sandwiched between two 8" woofers could be very nice. Even 6.6" woofers could do... the 8" seem so big compared to the little BMRs!
Attachments
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It's an odd driver. I have a thread in multi way where I horn loaded and measured them.
I think the comb filtering is exacerbated by the way the cone behaves. In a traditional loudspeaker, only the center of the cone is vibrating at very high frequencies. For instance, if you play 16khz on a 3.5" Fostex driver, only the center is moving. So the Fostex behaves as if it's about 1" in diameter at 20khz.
This behavior is achieved via a careful combination of cone, surround, and dustcap. It's the reason the Fostex costs $35 and cheap paper woofers cost $8.
But the BEM drivers are ultra rigid, so the entire disc is vibrating at 20khz. You can see this in the polar response.
I think the comb filtering is exacerbated by the way the cone behaves. In a traditional loudspeaker, only the center of the cone is vibrating at very high frequencies. For instance, if you play 16khz on a 3.5" Fostex driver, only the center is moving. So the Fostex behaves as if it's about 1" in diameter at 20khz.
This behavior is achieved via a careful combination of cone, surround, and dustcap. It's the reason the Fostex costs $35 and cheap paper woofers cost $8.
But the BEM drivers are ultra rigid, so the entire disc is vibrating at 20khz. You can see this in the polar response.
If you guys could make an estimation, how much, if any, can the frames be milled away to close the center-to-center of the array? Minding the comb filtering, part of me wonders how effectively these could be used as computer speakers in a short array (monitor height, let's say, so maybe 5-6 tall) where minimizing the desk bounce may be worthwhile.
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