Hi
A few thoughts, for a horn which has one side of the driver exposed, like the BassMaxx’s or an old “scoop” for that matter, the driver suspension takes the place of the stiffness one normally uses (in the form of a sealed box) in a conventional horn (like a lab).
The issue here is not that there is “spare energy” that can be picked up by using the rear of the driver, a horn can load the driver just fine on one (either) side.
Rather, the reason for the Tapped horn is that when one makes the horn “too small” then one gets large peaks and dips in the response. Those are caused by the acoustic load on the driver changing too much (on account of the horn mouth being too small).
The idea in the tapped horn is that by including both faces of the radiator within the horn passage, separated by distance (phase), the load on the driver is then comprised of the load on one side at some frequencies and both sides at another (as well as “in between”).
In effect, by making the driver’s radiating area change with frequency, one can accommodate a much smaller horn (the changing impedance it presents to the driver).
The physical arrangement is as Mark pointed out, is conceptually similar to the BP system he linked with the air Volumes being very small and the horn (instead of ports) being more normally sized. The roll off on a Tapped horn varies between 24 dB per octave (like a vented box) to about 18dB per octave or a little less (a sealed box is 12 dB per octave) depending on size / frequency.
As I am unaware of anything similar and being a “new” kind of horn with some apparent advantages, I have applied for a patent on this . It would be “premature” to make a LAB project out of it but who knows maybe someday.
FWIW, 1200Watts is 30.79dB over 1Watt, 1600Watts is 32.04dB over 1Watt, thus an increase from 1200 to 1600Watts is (with no power compression) is a change of 1.25dB, not 2.5dB.
When someone provides a measurement in a repeatable condition, then one can compare devices. I wish more folks published real response measured curves.
I have posted a higher resolution (than on the website) measurement of a TH-115 at 10 meters and 100Watts input (~3.5Hz bw, 1 /10 octave vector smoothing) equal to 1W1M.
While the measurement is only of the subwoofer range (it is a subwoofer), one could overlay the two relevant portions of the curves and compare the two at the same distance, same power level. Maybe someone with more skill than me can scale and overlay them in photoshop.
When comparing, levels VS frequencies, remember the TH115 is also smaller, it is 40 by 22 1/2 by 28 (with wheels) @ 120Lbs –VS- 42 by 42 by 22 ½ @<200lbs (w/o wheels).
What would really be fun is to compare the Z-5, labsub and 115 to some of the “big name, expensive” subwoofers out there, some of which obviously “play with” the numbers and also (because of?) have no response curves.
Here is where the marketing BS is going to cost the “Goliath’s” in the long run (I hope).
I think many would be down right pissed off if they knew what some speakers actually did compared to what was claimed, hence, I encourage people to measure for themselves.
Fwiw, I have met the Bass Max guys at a couple trade shows, the designer and I have some things in common and I do wish them good luck ( they have a powerful boxes too).
Best Regards
Tom Danley