Can a larger driver not perform as well



Quote:
Originally Posted by cptomes /forum/post/15446620


Given the low $/Watt amps available, high efficiency isn't as important as it was 40 years ago.

Click to expand...

well thats one way to look at it.


another way is to say since you now have an amp ( Powersoft K20 ) that produces 9000W x 2 channels you now should have a demand for a 9000 watt woofer. ( alternatively you can bridge a Crown I-Tech for roughly same power ).


does it make a lot of sense to make a 9000 watt 12" woofer ?


Audiopulse LMS Ultra recommends 5000 watts of amplifier power. it comes in 15" and 18".


now if you were to scale the LMS motor to 9000 watts your voice coil dimensions would have to increase by a factor of (9/5)^(1/2) or 1.3; so if you keep the proportions of the driver roughly the same the 15" version becomes 20" version and 18" version becomes 23" version.


so like i said i think there is a good case for a 21" woofer today.


now some people say that large woofers have low voice coil surface area ( thermal power handling ) relative to their weight. i could argue that this is not necessarily the case but i'm not going to do that because ...


i invented a solution to this problem years ago but it involves integration of the amplifier with the woofer as well as some sensors and/or control electronics so you probably won't see it implemented for some time. but it could certainly enable a 10,000 watt motor with perhaps three inches of excursion and a BL factor of something like 50 at maybe 10 pounds of weight. efficiency would also be roughly twice that of any current woofer. there is no real limit to the performance of this technology.


now if somebody were to step up to the plate and bring this technology to life pretty soon a 21" woofer would be considered small.


anyway i gotta run ...



Quote:
Originally Posted by SlowcarIX /forum/post/15458753


how do you define a heavy woofer...how many inch, or mass of cone...? also what frequency range do you consider mid-bass? thx!

Click to expand...

inches aren't important. actually, the larger, the more efficient, so can be better.


moving mass, mms, which includes the cone. 50g is light, but needs a huge enclosure to get any depth even when designed well and doesn't do well on sub-bass spl because of limited coil winding depth at this weight. 150g still allows some mid bass and can find some good extension in a medium large enclosure. 450g is probably too heavy for mid bass, but provides for nice deep extension and efficiency in the sub-bass and max sub-bass spl. this must be weighed against the power of the motor and the coil winding, BL. BL^2 / mms^2 provides a rough understanding of the efficiency relationship that matters.


a driver that has 100g mms and 20 Bl produces a level of midbass. doubling the mms requires a doubling of the Bl to achieve the roughly the same midbass. this is why hsu chose a lightweight driver for his mbm and didn't just put a giganormous magnet on his subwoofer driver...it would have to be impracticly big in order to have the mid bass of the lighter cone.


roughly 60-180hz or so (drums and the lower end of the electric guitar).

what really matters for high frequency extension is not MMS its the mass of the voice coil itself.


the basic idea is conservation of energy. energy doesn't get from electrical to acoustical in one step. it has to go into kinetic energy of the voice coil first. then it has to go from kinetic energy of the voice coil to kinetic energy of the diaphragm. the problem is that at different frequencies the diaphragm couples to the voice coil in different ways.


at high frequencies the part of the cone that couples to the voice coil is small and therefore light. if the voice coil is heavy the energy transfer will not be efficient to the cone.


if voice coil mass was zero the response would just keep going and going. you would basically have a ribbon tweeter. because a ribbon tweeter doesn't have any voice coil that has to couple its energy to the diaphragm - the diaphragm is energized directly.


so its not a matter of whether you have a 12", 18" or 21" woofer. its about voice coil mass. i could build a 21" woofer with response to 20 khz if i wanted. i could also build a 12" woofer without much response above 50 hz.


historically it just so happens that there aren't too many 21" tweeters which is why people succumbed to the delusion that size of the driver is what determines its frequency response.


the good news is you will never really figure out whats going on. its good because if you could figure these things out there would be no place for trolls like me