Hi
The TH115 is a very modestly sized bass enclosure, which uses a 15” driver in a new type of low frequency horn I developed called a Tapped Horn.
Your observation about the mouth area being small is correct, the advantage of the Tapped horn is that it allows a significantly smaller horn to be used than normal.
How you ask?
AS you make the horn mouth smaller, one finds ripples in the frequency response, which inversely coincide with peaks and dips in the impedance curve.
These reflect a greatly changing acoustic load on the driver.
With the Tapped Horn, the driver source impedance to the horn is made to change with frequency also, in a way that can largely adapt to the changing horn load, at least over the bass range. This is done by having both sides of the driver, driving the horn but from different points on its length.
You will notice that even with one TH115, the normal ripple one would expect in a horn that small is not present.
A more extreme case is the PB-12 which has a Teeny Tiny mouth but still lacks the traditional ripple pattern.
So far as the LabSub, it was pretty much as much as I could get out of that size box and cutoff, going as far as seemed safe with driver parameters.
Even now some years later, the Lab 12 driver is one beefy driver.
The only Tapped Horn comparable in size to the Lab sub is the Vortex, also a Tapped horn which is a little smaller (42 by 42 by 22 ½ in). I couldn’t find the measurements someone sent me of their single Lab @ 1meter but one for one the Vortex would have less ripple and greater sensitivity.
Once you had say 6 Labs (where the mouth is big) then they would be about 50% efficient and would be hard to beat electroacoustically.
Multiple Vortex’s in a 2X2 , 2X3, 3X3 array would have forward directivity due to the frontal area BUT requires a crossover below 90-100 Hz due to the spacing between outlets.
A 2X2 array would have about 10 dB of apparent gain on axis added to the sensitivity mid band in addition to a higher over all efficiency.
We do not have measurements for that case yet however.
In another thread there here is a discussion about spec’s.
The curves on our web site are TEF measurements, taken in a conservative way by driving the box in half space at 100W and at a microphone distance of 10 meters.
This removes the errors present if one measures a large speaker up close at 1 meter and the 10 meter distance is –20DB from 1 Meter but the 100W level is + 20dB from 1 Watt so the result is a conservative 1 Watt equivalent.
These are what anyone else will measure if they do the same test, no magic or BS.
Numbers are for designing so they should be accurate but listening is what really matters, I think you would be impressed with the sensitivity, sound quality, output and weight of the TH115….but how else could I feel ha ha..
Your best bet is to call Mike and see about getting some demo’s, nothing beats first hand comparisons.
Hope that helps
Tom Danley