Ohh My ! i thought the Levan will hit 30 flat, as all the people who installed them or have been in clubs and "felt" them rave about them
so then is not how low it goes but the "flavour" of the bass of a front loaded horn VS a tapped horn ?
or what is it that the berthas have that spectacular reviews
nothing compare to them back in the day ?
now with a bunch of Danley's TH118XL or a pile of L-Acoustics KS28's nobody seem to miss the berthas.
is it ?
so then is not how low it goes but the "flavour" of the bass of a front loaded horn VS a tapped horn ?
or what is it that the berthas have that spectacular reviews
nothing compare to them back in the day ?
now with a bunch of Danley's TH118XL or a pile of L-Acoustics KS28's nobody seem to miss the berthas.
is it ?
Overall, that adds up to an exponential expansion, but as each individual horn section has two parallel walls, "Par" (parabolic) rather than "Exp" would make the sim closer to the build.
That said, it won't make much difference in the results.
Fc looks higher than the EAW spec, indicating your estimated path length might be a little short.
The "advanced centerline" estimation seems to work best for horn folds :
I don't think I could be off by more than maybe 5-10cm which seems insignificant for a rough estimate. That's less than a fraction of the 1/4 wavelengths we are looking at to go lower.
For reference, I attached the PDF.
For reference, I attached the PDF.
Right , minor path length difference and the "Exp" substituted for the "Par" won't amount to much.
The "VTC" (Volume of Throat Chamber) made up by the cone profile and the speaker standoff (which you omitted in your "Bertha PDF") will also make a small difference which may not amount to much.
Omitting the speaker standoff, or making it's depth too short will make for a lot of slapping when driven hard just above or below Fb 😳
Drivers sealed in small rear chambers get hot. I reversed the driver in an offset FLH to put the LAB12 magnet vent in the throat for better cooling, making VTC considerably larger.
The Hornresp sim indicated a fairly large change in VTC would make little response difference, but it did, requiring a retrofit of a circle around the driver to reduce the ATC volume.
Anyway, the cone profile on an 18" with a standoff and throat restriction can amount to a fair amount of VTC...
The "VTC" (Volume of Throat Chamber) made up by the cone profile and the speaker standoff (which you omitted in your "Bertha PDF") will also make a small difference which may not amount to much.
Omitting the speaker standoff, or making it's depth too short will make for a lot of slapping when driven hard just above or below Fb 😳
Drivers sealed in small rear chambers get hot. I reversed the driver in an offset FLH to put the LAB12 magnet vent in the throat for better cooling, making VTC considerably larger.
The Hornresp sim indicated a fairly large change in VTC would make little response difference, but it did, requiring a retrofit of a circle around the driver to reduce the ATC volume.
Anyway, the cone profile on an 18" with a standoff and throat restriction can amount to a fair amount of VTC...
Attachments
I think I see what you're saying. The driver needs a little height off the baffle which is the "stand off" so the cone doesn't slap the letterbox and you can seal up VRC with less air by making that staved wood part. the VTC needs to exist while being as far from the baffle as the cone needs to travel. I might use some 1" material for the standoff.. what a nightmare of a mistake it would be if that were too short.. That said we both think the acoustic changes in our efforts to dial the sim in tighter would be minimal.. Am I following you?
For a sealed chamber the size don't change too much the response, large chamber may just help to increase the time the driver take to heat up and modern driver like small chambers to flatter response.
The dimensions can be changed to increase horn length, so it will tune the frequency down.
The VTC includes the volume of the standoff (you might use 1" or 25mm, rather than the 15mm the EAW BH882 used for construction) the speaker gasket depth, plus the volume of the cone shape which together may total more than 4 liters per driver. Cone shapes come from near flat to 100mm deep.
The volume of the rear chambers (VTC) also includes the triangular sections on either side, above and below and in between the initial horn expansion. Those volumes could be sealed off if you choose to use a smaller VTC .