I’ve never seen such a big ribbon driver before, nor one with such an extended frequency response. On paper it looks like and option of something close to a FAST system. Of course, there are no THD measurements and I can’t find anyone using them (the pdf is marked preliminary). Are there obvious trade offs with ribbons tweeters trying to go this low?
LM8K - Wide Band Planar Ribbon Transducer - Radian Audio
Brian
LM8K - Wide Band Planar Ribbon Transducer - Radian Audio
Brian
From the data sheet, it looks like a plainer magnetic.
to me it looks a lot like a Bohlender Graebener Neo10 Planar Transducer
I love my NEO 3. its just not a ribbon.
to me it looks a lot like a Bohlender Graebener Neo10 Planar Transducer
I love my NEO 3. its just not a ribbon.
More like Neo 8. Same size, different FR, flat plates..
https://www.parts-express.com/pedocs/specs/264-712-bohlender-graebener-neo8-specifications-44294.pdf
On Angel’s Wings, Part 1 - A Speaker Design for the Bohlender Graebener RD-75 Planar Magnetic Driver | audioXpress
https://www.parts-express.com/pedocs/specs/264-712-bohlender-graebener-neo8-specifications-44294.pdf
On Angel’s Wings, Part 1 - A Speaker Design for the Bohlender Graebener RD-75 Planar Magnetic Driver | audioXpress
OK, so there is precedent for frequency response that low. The NEO8 seems to be unobtanium now but I can read old reviews and review projects to see how others fared using a planar with such a wide frequency response.
The full line of BG drivers are available at Parts Express. The ones I've got have been fine, but there are reports that the unit to unit consistency is poor.
As far as the Radian drivers, I've been in contact with them and will be buying a few soon to test out. Once I get them, I'll post comparison measurements with the Neo8S that I've got on hand.
Greg
I think that radian would do well in a front horn. I think it could be a flat frequency response from 200Hz - 18kHz. It would give it a much wider coverage. Sensitivity would increase 6-8 dB. The maximum SPL would increase the same amount. If you over powered it I think it would just get warm and start to compress the sound.
At what frequency? It's not a simple, one number answer. The taller the driver, the less vertical dispersion. And the higher the frequency, the less dispersion.
Two of these drivers are not going make appropriate Karaoke speakers, run full-range.
Greg
The vertical height is comparable to the Neo 10 (..and 8, 8S, 8 PDR).
Here is Zaph's single driver vertical measurement for the 10:
http://www.zaphaudio.com/temp/B&G-Neo10-FR-offaxis-vert-0-15-30-45-60.gif
-the longer the vertical line, the more directive/narrow the freq. response off-axis.
Note: an engineered (for the desired dispersion) horn can trade some of the further-out off-axis pressure reduction for more pressure as you get closer to 0 degrees. (..basically shooting for a moderately similar +/- 30 degree window, with very little pressure as you move to 60 degrees plus.) It could also make a 1st order design a bit easier to accommodate with acoustic gain.
Here is Zaph's single driver vertical measurement for the 10:
http://www.zaphaudio.com/temp/B&G-Neo10-FR-offaxis-vert-0-15-30-45-60.gif
-the longer the vertical line, the more directive/narrow the freq. response off-axis.
Note: an engineered (for the desired dispersion) horn can trade some of the further-out off-axis pressure reduction for more pressure as you get closer to 0 degrees. (..basically shooting for a moderately similar +/- 30 degree window, with very little pressure as you move to 60 degrees plus.) It could also make a 1st order design a bit easier to accommodate with acoustic gain.
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The plot from JohnK is the directivity in the vertical plane of the Neo 8, which was just being used as a proxy for the LM8K (since no data is available in the vertical plane).
OTOH, the response in the horizontal plane is much better. Here is a plot of the horizontal directivity of the LM8K as a dipole, from the Radian web site:
An externally hosted image should be here but it was not working when we last tested it.
Looks pretty good...
To improve the vertical directivity it might be possible to add foam or felt to the outside of the perforated metal fame of the driver, in the upper most and lower most 1" of the radiating surface. The only way to tell would be to buy one and try it.
This is a pretty interesting product. I could sure make use of it between 750Hz and 3kHz in a dipole loudspeaker. Heck, two per side in a MTM format could work very nicely... but they are $200 each.
FYI, here is a link to the full datasheet. It includes a plot of the LM8K vertical directivity in a closed box:
RADIAN LM8K DATASHEET
... or as a pdf file:
https://radianaudio.com/wp/wp-content/uploads/2017/12/LM8K-data-sheet-011117.pdf
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Would anyone who owns one of these be open to measuring and posting the frequency response of the unit used as a dipole (no baffle at all) in the vertical (long) direction, on axis and off axis at every 10 degrees or so? Radian only provides the vertical response data for the driver with closed back.
If someone one ship me one I will be happy to make a complete set of outdoor measurements of the driver as a dipole (nude, without baffle) including frequency response and harmonic distortion. I live in Michigan. I would send the driver back after making the measurements.
If someone one ship me one I will be happy to make a complete set of outdoor measurements of the driver as a dipole (nude, without baffle) including frequency response and harmonic distortion. I live in Michigan. I would send the driver back after making the measurements.