29Hz from a 34.6 cubic foot box (almost 1000 liters) is not very amazing.
The dimensions of 32" x 36" x 52" are not very DIY friendly, but the design is easy to build:
The drivers used in the EAW KF940 have low MMS (and Xmax) so contribute to the high sensitivity, but using modern drivers with over double the Xmax considerably more low frequency output is possible.
A tapped horn design like Josh Ricci's Othorn could be adapted for dual 12", using modern drivers could achieve similar low frequency output of the KF940 in about half the volume:
That said, limiting the driver size to 12" in huge cabinets does not make much sense now that high excursion 18" and 21" drivers that will hold up to horn loading are readily available.
The dimensions of 32" x 36" x 52" are not very DIY friendly, but the design is easy to build:
The drivers used in the EAW KF940 have low MMS (and Xmax) so contribute to the high sensitivity, but using modern drivers with over double the Xmax considerably more low frequency output is possible.
A tapped horn design like Josh Ricci's Othorn could be adapted for dual 12", using modern drivers could achieve similar low frequency output of the KF940 in about half the volume:
That said, limiting the driver size to 12" in huge cabinets does not make much sense now that high excursion 18" and 21" drivers that will hold up to horn loading are readily available.
Hey Art,
so basically what you saying is that at the time the KF940 was designed, they choose to use dual 12"s instead of a 18 or 21 cause at the time it was
the 18's will not outperform those dial 12"s correct , and they have used that big volume so to hit 29Hz.
Now, budget wise, what makes more sense , An othorn with dual 12's or just as it is designed.
so basically what you saying is that at the time the KF940 was designed, they choose to use dual 12"s instead of a 18 or 21 cause at the time it was
the 18's will not outperform those dial 12"s correct , and they have used that big volume so to hit 29Hz.
Now, budget wise, what makes more sense , An othorn with dual 12's or just as it is designed.
Yes, back in 1998 there weren't many 18" or 21" that would handle the power of the two 12" and also stand up to cone pressures of a horn.
The Othorn was designed to use the 21" B&C 21SW152-4,(Sd 1680 Cm2) which has an Xmax about double of the 12" used in the KF940.
To equal that displacement using the EAW804058 12" (roughly 7-8mm Xmax, Sd 520 Cm2) would require six, which probably cost about as much as the similar looking Eminence Kappa Pro-12A (only 4.8mm Xmax).
At Parts Express current price for the B&C 21SW152-4 is $907 (12.5Kg), Kappa Pro-12A is $175x6=$1050.00 (45.18Kg).
Displacement per $$ is a moving target, more options are available now than 25 years ago.
The Othorn was designed to use the 21" B&C 21SW152-4,(Sd 1680 Cm2) which has an Xmax about double of the 12" used in the KF940.
To equal that displacement using the EAW804058 12" (roughly 7-8mm Xmax, Sd 520 Cm2) would require six, which probably cost about as much as the similar looking Eminence Kappa Pro-12A (only 4.8mm Xmax).
At Parts Express current price for the B&C 21SW152-4 is $907 (12.5Kg), Kappa Pro-12A is $175x6=$1050.00 (45.18Kg).
Displacement per $$ is a moving target, more options are available now than 25 years ago.
Attachments
Ahhh, so a 21sw152 on a similar tuned horn will do the trick.
Can the keystone or TH18 be modified to do 30hz flat using the 21 B&C
And I'm asking cause times change and before 40 or even 35 we're the norm as the title of the TH18 flat to 35...
But nowadays EDM and d&b hit 30 or 28...
So the requirement shift
Besides , reflex can hit 30hz flat or less with their distortion limitation so, a horn that can do the same range will be awesome even that you need to multiply the cab count by 1.5
As long you hit the SPL and slam the stage we are golden!!
Can the keystone or TH18 be modified to do 30hz flat using the 21 B&C
And I'm asking cause times change and before 40 or even 35 we're the norm as the title of the TH18 flat to 35...
But nowadays EDM and d&b hit 30 or 28...
So the requirement shift
Besides , reflex can hit 30hz flat or less with their distortion limitation so, a horn that can do the same range will be awesome even that you need to multiply the cab count by 1.5
As long you hit the SPL and slam the stage we are golden!!
THs are limited in usable bandwidth to less than 3*Fb.
A 30 Hz TH would get you up to about 80 Hz and will likely needed to be LP'd pretty steeply at that point.
In comparison, a 30 Hz OTDL should be able get up to around 120 Hz,.
A 30 Hz TH would get you up to about 80 Hz and will likely needed to be LP'd pretty steeply at that point.
In comparison, a 30 Hz OTDL should be able get up to around 120 Hz,.
The driver/cabinet alignment is key to the "flatness", but the lower Fb of the cabinet does not change with the driver.
The scaled down, shorter path length version of the EAW KF940, the LA400, is a 45Hz horn.
If you "modified" the 35Hz Fb Keystone or TH18 to the have same path length, cabinet volume and fold pattern as the Othorn, they would also have 30Hz response 😉.
Art
Thanks for the explanation and graphs, it makes much sense now , and again, I know PA subs normally don't go below 40 or 35 so you don't sacrifice much SPL, but with the new breed of drivers and more affordable amplification , it is more doable to have more cabs and power to hit lower with great SPL.
Along those lines between a horn flat to 30 (27hz -3dB) and a reflex tuned to 30Hz
Who will need less power to attain the same SPL if you test them next to each other.
And what was the horn type who in multiples of 4 cabinets will reach lower? I can't recall.
Along those lines between a horn flat to 30 (27hz -3dB) and a reflex tuned to 30Hz
Who will need less power to attain the same SPL if you test them next to each other.
And what was the horn type who in multiples of 4 cabinets will reach lower? I can't recall.
I can't recall (valid) measurement data showing horns in multiples with more LF gain or extension than direct radiators.
A FLH with response actually "flat to 30 Hz" would require a mouth circumference near a wavelength, around 12 foot diameter for 30Hz.
That horn would be much larger than the 34.6 cubic foot EAW KF940.
A bass reflex alignment with response "flat to 30 Hz" can be built in a box under one cubic foot, the larger horn would use less power to attain the same SPL at 30Hz .
FLH low frequency horns require lots of volume to achieve their efficiency, once volume is restricted, there comes a point where an "oversized" BR will be more efficient than an "undersized" FLH.
The most efficient design may not be capable of as much SPL less efficient design.
A FLH with response actually "flat to 30 Hz" would require a mouth circumference near a wavelength, around 12 foot diameter for 30Hz.
That horn would be much larger than the 34.6 cubic foot EAW KF940.
A bass reflex alignment with response "flat to 30 Hz" can be built in a box under one cubic foot, the larger horn would use less power to attain the same SPL at 30Hz .
FLH low frequency horns require lots of volume to achieve their efficiency, once volume is restricted, there comes a point where an "oversized" BR will be more efficient than an "undersized" FLH.
The most efficient design may not be capable of as much SPL less efficient design.
Last edited: