low frequencies = cones. not too controversial. yes there are belt driven subwoofers, modulated fan subwoofers, there is Powersoft M-Morce moving magnet subwoofer etc. but for our purposes here we're just going to cover everything below 1 khz using good old dynamic paper cone drivers and we won't discuss them because they're boring.
but mid to high frequencies there are options, for example:
cones
domes
compression drivers
planar
AMT
true ribbon
electrostatic
probably forgetting some like Plasma tweeters ...
the question is what would be the perfect compliment of technologies to cover the range above 1 khz ?
my thinking on this question has evolved over time but as of two days ago it is as follows:
1 - 3 khz = BMS 4596ND ( annular diaphragm compression driver )
https://www.bmsspeakers.com/index.php-71.html?id=4596nd
3 - 9 khz = Beyma TPL200 ( pleated diaphragm air motion transformer )
https://audioxpress.com/article/tes...a-tpl200-h-pro-sound-air-velocity-transformer
9+ khz = Aurum Cantus G3 ( pure aluminum true ribbon )
https://www.parts-express.com/Aurum...6kDwku8s0r1xlyZU5_2n0FYdFRLdz9xUaAmGJEALw_wcB
those technologies are the most efficient, flattest measuring, highest output and lowest distortion in their respective frequency ranges.
for example the BMS midrange begins to fall apart above 3 khz due to "mass break point" ( apparently function of horn geometry ) and flex of the relatively soft polyester diaphragm ...
the TPL begins to fall apart above 9 khz due to the depth of the pleat putting an upper limit on HF response much like in a compression dome the spacing between phase plug slots puts a limit on HF response
while the True Ribbon can go well past 20 khz but is limited on the low end by the fact that it doesn't seal the air chamber ...
as well the TPL can't go very low either because the forces are side to side - no force front to back which means air pressure at low frequencies can push the entire diaphragm in or out which means that the air chamber is only FLEXIBLY sealed and it can only go marginally lower than true ribbon - nowhere near as low as compression driver
a planar can go as low as a compression driver because motor force is front to back and the chamber is sealed. the problem is that at frequencies below those which AMT can comfortably handle the planar is soundly beaten by the compression driver, by about 10 decibels of efficiency, while also having the benefit of user replaceable diaphragms. i think one reason you don't see many planars in prosound is you can't replace a blown diaphragm in a planar like you can in a compression driver.
you CAN replace a diaphragm in the Beyma TPL as well you can replace a ribbon in most good True Ribbon tweeters like Aurum Cantus, which offers both replacement ribbons and replacement instructions. RAAL also sells replacement ribbons for most of their drivers. With some ribbon tweeters you can roll your own ribbons as well.
and at frequencies above mass break point of compression driver the planars exhibit rather erratic behavior that isn't close to flat. in fact the planars aren't flat anywhere in the frequency range. combine that with planars having the lowest efficiency ( between CDs, AMTs and True Ribbons ) and being the only one of these four technologies with non-replaceable diaphragms and you can see why i have eliminated them from the "optimum" setup.
and thus the winning trinity ( as mentioned above ) is Compression, AMT and True Ribbon with 1 khz, 3 khz and 9 khz crossover points where the compression is a dedicated midrange from BMS ( or if you prefer B&C, but i think BMS is better ) and the AMT is Beyma TPL200 ( which i think makes a better dedicated upper midrange, while the TPL150 tries and fails to cover a wider frequency range ).
sadly there is no True Ribbon on same level of engineering as BMS and Beyma because major prosound companies like that do not make True Ribbons and instead for TR you have to rely on less sophisticated operations, most of them from Asia ( except RAAL ) and there doesn't seem to be one real winner between the Ribbons.
RAAL seems to be the highest regarded and does seem to have the best ribbon element but i don't like how they put the transformer inside the acoustical chamber. it strikes me as a cost cutting measure so they don't have to build a housing for the transformer like every other ribbon maker does and the downside is the chamber now can't be fully acoustically optimized. it is now both too large ( for a supertweeter ) and asymmetrical.
but mid to high frequencies there are options, for example:
cones
domes
compression drivers
planar
AMT
true ribbon
electrostatic
probably forgetting some like Plasma tweeters ...
the question is what would be the perfect compliment of technologies to cover the range above 1 khz ?
my thinking on this question has evolved over time but as of two days ago it is as follows:
1 - 3 khz = BMS 4596ND ( annular diaphragm compression driver )
https://www.bmsspeakers.com/index.php-71.html?id=4596nd
3 - 9 khz = Beyma TPL200 ( pleated diaphragm air motion transformer )
https://audioxpress.com/article/tes...a-tpl200-h-pro-sound-air-velocity-transformer
9+ khz = Aurum Cantus G3 ( pure aluminum true ribbon )
https://www.parts-express.com/Aurum...6kDwku8s0r1xlyZU5_2n0FYdFRLdz9xUaAmGJEALw_wcB
those technologies are the most efficient, flattest measuring, highest output and lowest distortion in their respective frequency ranges.
for example the BMS midrange begins to fall apart above 3 khz due to "mass break point" ( apparently function of horn geometry ) and flex of the relatively soft polyester diaphragm ...
the TPL begins to fall apart above 9 khz due to the depth of the pleat putting an upper limit on HF response much like in a compression dome the spacing between phase plug slots puts a limit on HF response
while the True Ribbon can go well past 20 khz but is limited on the low end by the fact that it doesn't seal the air chamber ...
as well the TPL can't go very low either because the forces are side to side - no force front to back which means air pressure at low frequencies can push the entire diaphragm in or out which means that the air chamber is only FLEXIBLY sealed and it can only go marginally lower than true ribbon - nowhere near as low as compression driver
a planar can go as low as a compression driver because motor force is front to back and the chamber is sealed. the problem is that at frequencies below those which AMT can comfortably handle the planar is soundly beaten by the compression driver, by about 10 decibels of efficiency, while also having the benefit of user replaceable diaphragms. i think one reason you don't see many planars in prosound is you can't replace a blown diaphragm in a planar like you can in a compression driver.
you CAN replace a diaphragm in the Beyma TPL as well you can replace a ribbon in most good True Ribbon tweeters like Aurum Cantus, which offers both replacement ribbons and replacement instructions. RAAL also sells replacement ribbons for most of their drivers. With some ribbon tweeters you can roll your own ribbons as well.
and at frequencies above mass break point of compression driver the planars exhibit rather erratic behavior that isn't close to flat. in fact the planars aren't flat anywhere in the frequency range. combine that with planars having the lowest efficiency ( between CDs, AMTs and True Ribbons ) and being the only one of these four technologies with non-replaceable diaphragms and you can see why i have eliminated them from the "optimum" setup.
and thus the winning trinity ( as mentioned above ) is Compression, AMT and True Ribbon with 1 khz, 3 khz and 9 khz crossover points where the compression is a dedicated midrange from BMS ( or if you prefer B&C, but i think BMS is better ) and the AMT is Beyma TPL200 ( which i think makes a better dedicated upper midrange, while the TPL150 tries and fails to cover a wider frequency range ).
sadly there is no True Ribbon on same level of engineering as BMS and Beyma because major prosound companies like that do not make True Ribbons and instead for TR you have to rely on less sophisticated operations, most of them from Asia ( except RAAL ) and there doesn't seem to be one real winner between the Ribbons.
RAAL seems to be the highest regarded and does seem to have the best ribbon element but i don't like how they put the transformer inside the acoustical chamber. it strikes me as a cost cutting measure so they don't have to build a housing for the transformer like every other ribbon maker does and the downside is the chamber now can't be fully acoustically optimized. it is now both too large ( for a supertweeter ) and asymmetrical.
The problem is the integration of different dispersion characteristics. Maybe put the BMS on a plane wave waveguide and line them up vertically...
So you are looking to cross the 15cm tall ribbon G3 at 9 khz. To a 20+ cm tall beyma tpl.
Which again crossed to a horn/waveguide at 3k, which also incurs a large ctc between that and the 20cm+ tall TPL.
That id also narrow 1-2 octave bands you are looking to use them in.
There will also be mismatch in dorectivity and power response. Outside of cancellations, lobing and resulting vertical directivity of the setup.
The right 1" compression driver with a fitting horn/wg will give you that entire range with spl capability, controlled directivity and good hf performance.
There are also compression drivers like fx TAD ET-703A, JbL 045, JBL D2415k etc. That is designed for 'tweeter' useage.
There also is the Phillips/Stage accompany "ribbons" which is a different tech, rarely mentioned.
A lot less rare then the plasma tweeters etc.
Which again crossed to a horn/waveguide at 3k, which also incurs a large ctc between that and the 20cm+ tall TPL.
That id also narrow 1-2 octave bands you are looking to use them in.
There will also be mismatch in dorectivity and power response. Outside of cancellations, lobing and resulting vertical directivity of the setup.
The right 1" compression driver with a fitting horn/wg will give you that entire range with spl capability, controlled directivity and good hf performance.
There are also compression drivers like fx TAD ET-703A, JbL 045, JBL D2415k etc. That is designed for 'tweeter' useage.
There also is the Phillips/Stage accompany "ribbons" which is a different tech, rarely mentioned.
A lot less rare then the plasma tweeters etc.
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Not really have to do with horns only, a cone has the same physical 'limitations.
Fhm = 2*Fs/Qts' (upper mass corner accordig to T&S theory).
Unless breakup/secondary resonances extends the response.
Also inductance plays a crucial role in that regard.
Direct radiating applications. Ribbon Planar or Dome for mids.
Gonna be hard to beat a aluminum cone mid, if the upper breakup has been reduced/ well designed.
Otherwise off axis a small dome will be hard to beat for sensitivity and directionality
Gonna be hard to beat a aluminum cone mid, if the upper breakup has been reduced/ well designed.
Otherwise off axis a small dome will be hard to beat for sensitivity and directionality