Insane and almost identical to another equivalents box of the same tuning, and port CSA. I know that PR causes a sharper roll off, but otherwise, this is just a mass loaded enclosure, like Mass loaded TL, instead of the mass load being that of an air volume, the mass is added via a PR and the "vent" is constricted further down the line, hopefully reaching a desired tuning and not something random.
The Mass added via PR essentially negates the need to lengthen the line to reach desired tuning.
If We copy the internal volume of this enclosure and then add the line that creates identical cutoff.... the completely vented version of this enclosure will out perform the PR loaded version. The advantage of PR is conservation of Space in order to reach a certain tuning. The act of not doing so, conserving space that is, will cause more efficiency.
So what is it then? PR is king of space conservation while being able to use the backwave and reach a low tuning? At some point an enclosure can become so small that reaching a certain tuning with an acceptable vent CSA becomes impossible, then enter the PR to save the day? Why not I guess.
My only critique of the box above @PassiveRadiatorDude, is that if the Vent CSA is lower than the SD of the PR than this design could be improved, possibly, by removing the vent and just placing the PR's on the baffle, and then add the mass to the PR to get the desired tuning. The increased, effective radiation area will increase efficiency and thus output.
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Yes, passive radiators are the king of space conservation while being able to use an effective radiating area and low tuning.
A bass reflex port with the equivalent radiating area tuned as low as the four 12" passive radiators would be insanely huge.
The cross section area of the "vent" of the slot loaded force cancelling dual radiator Earthquake Pump-12 passive radiators has almost nothing to do with their Fb.
Placing the four passive radiators on the baffle would not increase their effective radiation area, and would loose the force cancelling effect- that's over a kilogram of weight moving up to 100mm peak to peak at Fb.
A bass reflex port with the equivalent radiating area tuned as low as the four 12" passive radiators would be insanely huge.
The cross section area of the "vent" of the slot loaded force cancelling dual radiator Earthquake Pump-12 passive radiators has almost nothing to do with their Fb.
Placing the four passive radiators on the baffle would not increase their effective radiation area, and would loose the force cancelling effect- that's over a kilogram of weight moving up to 100mm peak to peak at Fb.
Not entirely.
A PR has a compliance, which a port doesn't have.
So sometimes this does change quite a lot of things.
In this case again, my first question would be why someone wants a bandpass system?
Because if there is any active EQ possible, the advantages go down VERY quickly.
Especially because PR's aren't cheap, and when two are needed, you might as well just go for a closed system with two woofers and have very similar maxSPL and low end.
I have never seen WinISD crashing btw, maybe you mean that it will give an error instead?
Make sure you don't put in all parameters, but just a few and let WinISD calculate the rest.
I usually put in Qms, Qes, Fs, Vas, Re, Sd, Xmax and Pe.
The part about the radiators being on the baffle versus in a slot..... You can see the effect of Vent CSA in Hornresp. I don't understand why you don't agree. If I make the slot CSA 1cm x 1cm you would argue that it has No effect on the final radiation mass/impedance? How is this possible?
Certainly a bass reflex vent with a tiny cross section area is near useless at high drive levels.
I never suggested or argued about making a slot for 2x12" with a CSA 1cm x 1cm.
The Pump 12 slot's air mass is so little compared to the half a kilogram of moving mass that it's CSA and volume is immaterial.
On light 18" drivers like the ones you use, the slot's air mass will lower the Fs a bit, but the CSA relative to the Pump 12's plenum exit and yours is similar. Obviously, you didn't find slot loading your drivers reduced effective radiation area or efficiency.
I never suggested or argued about making a slot for 2x12" with a CSA 1cm x 1cm.
The Pump 12 slot's air mass is so little compared to the half a kilogram of moving mass that it's CSA and volume is immaterial.
On light 18" drivers like the ones you use, the slot's air mass will lower the Fs a bit, but the CSA relative to the Pump 12's plenum exit and yours is similar. Obviously, you didn't find slot loading your drivers reduced effective radiation area or efficiency.
I just revisited my sims and discovered a flaw in my logic. If I changed the CSA from what it is (1/2.77 of the accumulated Sd) to the actual accumulated Sd (2560cm2) the change is not significant in the LF
Thats interesting... I do not have similar results with a vent, at tuning. Above or Below in a BR, going from 900cm2 to 450cm2 while matching tuning
More things for me to learn I guess. GD lowers on the BR as I shrink CSA but keep same tuning while the slot loaded LF GD increases as I decreases CSA, while GD near tuning lowers... The main concept is that CSA affects things differently depending on if near tuning/cutoff or not.
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For those that like lots of experimentation 'playtime' >
I have found that there are quite a few very cheap Auto Subwoofers that not only have high Xmax
but also very low Fs due to high mass cones. Being so cheap, they are low efficiency, but can be useful
as passive radiators that can be also 'slightly driven' using high value but 'lossy' cheap inductors. (6ohms DCR)
Along with 'cone mass tweaking', these slightly driven subs can create quite amazing low bass box tuning.
I have found that there are quite a few very cheap Auto Subwoofers that not only have high Xmax
but also very low Fs due to high mass cones. Being so cheap, they are low efficiency, but can be useful
as passive radiators that can be also 'slightly driven' using high value but 'lossy' cheap inductors. (6ohms DCR)
Along with 'cone mass tweaking', these slightly driven subs can create quite amazing low bass box tuning.
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Same reason small Churches, etc., want powerful, narrow BW LF from small containers to supplement their organs.