let's say HYPOTHETICALLY you took the large format B&C ME464 horn:
https://www.bcspeakers.com/en/products/horn/1.4/0/ME464
1.4" BMS midrange
https://www.bmsspeakers.com/index.php-62.html?id=bms_4594nd-mid
and Radian LM8K mid-tweeter configured as dipole
https://radianaudio.com/collections/ribbon/products/lm8k-wide-band-planar-ribbon-transducer
put the planar coaxially inside the horn and crossed them over at 1.5 khz ...
the black line in the chart below is for DIPOLE operation of LM8K WITHOUT BAFFLE
so as you see you don't lose any output by going dipole - if anything you get BETTER frequency response from the dipole ( above 1.5 khz )
there is a fairly obvious SLOT shape in the middle of the ME464 horn where the LM8K would fit almost perfectly ... of course i am not talking about blocking the output of the compression driver - there would perhaps be about 3 inches of space left on all sides of the LM8K for the sound from BMS mid can go around it ... but also some of the sound would go THROUGH it as well ...
then to control the back wave from the LM8K you would put some acoustical damping material ( like wool ) right behind it as well as line the sides of the horn with a thin layer of foam or felt ...
the logic being that below 1.5 khz a horn loaded BMS mid is about 110db / watt
versus a measly 90 db for the LM8K ... on other hand the BMS will roll off above about 3 khz but the LM8K actually has rising response all the way up to 10 khz ...
so you can create a sort of a co-axial driver, not unlike this radian:
https://radianaudio.com/collections/ribbon/products/6crn38lt6-line-array-driver
only instead of a cone there would be a midrange horn and the planar would be a dipole instead of having a very shallow chamber ( like what i assume Radian is using ).
i think dipole could be beneficial here because by allowing some of the BMS output to go THROUGH the dipole it would reduce the diffraction around it ...
also even though a dipole has a rear wave it has no side radiation so as long as the rear wave could be tamed maybe reflections inside the horn wouldn't be so bad.
for example you could even stuff the horn with wool so that the low frequencies can come out of the horn but the HF back wave from the planar is absorbed instead of being reflected ...
again, for the time being i am not suggesting this would make a practical speaker but rather this is a thought exercise - the question is can it be done and would it work ?
and yes i am aware BMS is famous for their COAXIALS so you could just get one of their 1.4" coaxials on the same horn but IMHO those are also not without compromise. it is not theoretically possible to perfectly combine the output of the two BMS diaphragms. the way they combine is merely GOOD ENOUGH not perfect.
the question then is can my proposed planar / horn coax combine the two outputs WELL ENOUGH too ?
the problem with BMS and B&C coax design is that it is immutable - whereas my concept can be CUSTOMIZED for different applications ...
you may not see the value in crossing over a midrange compression horn to planar and that's understandable in which case just imagine that instead of a horn it's a woofer. and you are placing a dipole planar in front of the woofer. has anybody tried that ?
obviously Radian has done it, but not with a dipole. but i think one benefit of dipole for example is that the diaphragm conductors would be cooled from both sides rather than sealed off with a chamber from behind thus increasing output capacity ...
another benefit is that bass from the woofer won't push the dipole diaphragm into the chamber but put similar pressure on it from both sides the force thus mostly canceling out so that the diaphragm isn't as heavily modulated by the bass ( hopefully )
i already mentioned that diffraction would be reduced ...
what do you think ?
https://www.bcspeakers.com/en/products/horn/1.4/0/ME464
1.4" BMS midrange
https://www.bmsspeakers.com/index.php-62.html?id=bms_4594nd-mid
and Radian LM8K mid-tweeter configured as dipole
https://radianaudio.com/collections/ribbon/products/lm8k-wide-band-planar-ribbon-transducer
put the planar coaxially inside the horn and crossed them over at 1.5 khz ...
the black line in the chart below is for DIPOLE operation of LM8K WITHOUT BAFFLE
so as you see you don't lose any output by going dipole - if anything you get BETTER frequency response from the dipole ( above 1.5 khz )
there is a fairly obvious SLOT shape in the middle of the ME464 horn where the LM8K would fit almost perfectly ... of course i am not talking about blocking the output of the compression driver - there would perhaps be about 3 inches of space left on all sides of the LM8K for the sound from BMS mid can go around it ... but also some of the sound would go THROUGH it as well ...
then to control the back wave from the LM8K you would put some acoustical damping material ( like wool ) right behind it as well as line the sides of the horn with a thin layer of foam or felt ...
the logic being that below 1.5 khz a horn loaded BMS mid is about 110db / watt
versus a measly 90 db for the LM8K ... on other hand the BMS will roll off above about 3 khz but the LM8K actually has rising response all the way up to 10 khz ...
so you can create a sort of a co-axial driver, not unlike this radian:
https://radianaudio.com/collections/ribbon/products/6crn38lt6-line-array-driver
only instead of a cone there would be a midrange horn and the planar would be a dipole instead of having a very shallow chamber ( like what i assume Radian is using ).
i think dipole could be beneficial here because by allowing some of the BMS output to go THROUGH the dipole it would reduce the diffraction around it ...
also even though a dipole has a rear wave it has no side radiation so as long as the rear wave could be tamed maybe reflections inside the horn wouldn't be so bad.
for example you could even stuff the horn with wool so that the low frequencies can come out of the horn but the HF back wave from the planar is absorbed instead of being reflected ...
again, for the time being i am not suggesting this would make a practical speaker but rather this is a thought exercise - the question is can it be done and would it work ?
and yes i am aware BMS is famous for their COAXIALS so you could just get one of their 1.4" coaxials on the same horn but IMHO those are also not without compromise. it is not theoretically possible to perfectly combine the output of the two BMS diaphragms. the way they combine is merely GOOD ENOUGH not perfect.
the question then is can my proposed planar / horn coax combine the two outputs WELL ENOUGH too ?
the problem with BMS and B&C coax design is that it is immutable - whereas my concept can be CUSTOMIZED for different applications ...
you may not see the value in crossing over a midrange compression horn to planar and that's understandable in which case just imagine that instead of a horn it's a woofer. and you are placing a dipole planar in front of the woofer. has anybody tried that ?
obviously Radian has done it, but not with a dipole. but i think one benefit of dipole for example is that the diaphragm conductors would be cooled from both sides rather than sealed off with a chamber from behind thus increasing output capacity ...
another benefit is that bass from the woofer won't push the dipole diaphragm into the chamber but put similar pressure on it from both sides the force thus mostly canceling out so that the diaphragm isn't as heavily modulated by the bass ( hopefully )
i already mentioned that diffraction would be reduced ...
what do you think ?
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