What can anyone say about Quarter Wavelength transmission line enclosure design ?

Acoustic Zen loudspeakers utilize the transmission line design. They sound phenomenal!!! 

I built the electrostatic panels too, rodman. Just the way Sanders described. They sure looked like they would work! But being a starving college student it took me a while figuring out how to find and buy everything for the power supply to make them work. In the meantime I for some unfathomable reason decided to remove the woofers from the TLs.

Now if you ever do this be sure to use a cap or something to cover the speaker mounting bolts. Because the whole thing is stuffed with dacron. If you don't cap the bolts then when you go to remove the bolt the dacron gets wrapped around it so tight you're never getting that bolt out without destroying the cabinet, or the driver, or both.

And that will be the end of your glorious Speaker Builder Electrostatic TL project. Sigh.

I built a pair (in 1981), per Roger’s design, to go with a customer’s Acoustat Model IIIs. He wanted something that could match the speed and definition, of his electrostatics. They worked so well, powered by a Halfer DH-500 and crossed over via a Dahlquist DQ-LP1, I duplicated the system for myself(and my Acoustats) and another customer. Back then, I used a 10" woofer that Milo Nestorovic employed in his woofer systems. In answer to the OP’s original query; TLs(at that time), were the only woofers systems around, that many of us had experienced, able to blend well with electrostatics. I used bi-amped TLs, in concert with various planars, for 36 years. Now, with an Emerald Physics system. The trusty DQ-LP1 was replaced by a modded TacT RCS 2.2X(and Hafler Trans-Nova 9505), about 12 years ago. The TacT’s DSP(time-alignment/room correction/EQ) was the finishing touch, to an already stellar bottom end. Guess I’m a TL believer!

I am very fortunate to have a pair of T+A Criterion 210 speakers that are transmission line designs that are done right!  They have exceptional response from top to bottom and absolutely no overhang in the bass. They are very heavy speakers due to the transmission line enclosure, but that is a small price to pay for wonderful sound.