Kennythekey, in what part of the country are you located?
Since you have the motivation to visit Jeff Catalano, I fully encourage you to do so. You'll have an absolute blast! Jeff's a great guy, representing some of the more interesting yet least encountered equipment. His place, literally in the shadow of the Brooklyn Bridge, is something of a historical landmark, filled with more records than you'll believe.
Though difficult for me to explain in objective terms, something certainly exists with both backloaded horns and transmission line bass alignments in that they behave in a more complex pattern in terms of the load they present to a partnering amplifier than do sealed, ported, and front loaded horn loudspeakers; all those operating in a far more simple way. Then again, it should appear logical that what happens after the electrical impulse excites a driver's voice coil will be different as the driver's backwave has to travel such an incredibly far distance in comparison. The simple, electrical, numbers living on a stat sheet fail to capture this phenomenon. At any rate, let us understand that how the amplifier interfaces with the loudspeaker will determine how effectively, or not, that air mass propels down the labyrinth.
As Bud Fried stressed, a backloaded horn and a true transmission line are the exact opposite of one another. In simple terms, as the name implies, the area of the horn increases exponentially in size as we traverse it, whereas the transmission line decreases exponentially.
My experience shows that some amplifier topologies work better with some loudspeaker alignments than others. Representing a company producing a wide range of amplifiers allowed me to play in a way where differences in parts and the designer's approach canceled out. By that I mean, the amplifiers used parts from the same manufacturer and type, and the amplifier circuitry would be shared across differing products. Obviously, when comparing a push-pull pentode design to an SET, you would find the expected disparities. However, when comparing a 211 and 845 SET or 2A3 and 300B PSE or push-pull, we were dealing with almost identical product.
What initially surprised me was that the company's very powerful 78 wpc push-pull triode/pentode switchable amplifiers paled in comparison to the ability to put power into a backloaded horn next to their modestly powered 15 wpc 211 and 28 wpc SET. The 300B 8 wpc SET and 16 wpc PSE wound up closer to the 211. Now, who would ever believe that an SET could outmuscle a push-pull amp in a drag race? Yet, across the speakers of three different companies, the trend held up. Strange to see, but it actually came across as if the PP amps felt like a runner or bicyclist struggling for air when climbing a steep hill. These amps just could not get over the hump. This demonstrated there really is something to the SET phenomenon that those who denigrate their low power on paper have not yet realized. In somewhat of an analogy between tube and solid state, I believe the SET kind of power is actually different in a way we have thus far failed to be able to measure.
The transmission lines displayed conventional (and expected) performance.
Again, the OTL amplifiers we used (not only Atma Sphere - note: the A/S were 2004 and 2008 vintage) behaved the way I described in an earlier post. One big surprise that I didn't mention, even with the nominal 4 (dipping to 2.3) ohm load of one of the true TLs, the OTL amplifiers, even the 30 wpc Atma Sphere S30, outshined more powerful transformer coupled tube amps in virtually every case. Of course, just like people I know who power their B&W and older Wilson (newer are much better) speakers with OTL amplification, just because it's done, doesn't mean it's good.
In the end, as the saying goes, it's horses for courses...
