Lowthers. Mention them to the utterly uninitiated audiophile bystander. Chances are, you'll hear "Lowther shout" in response. This demonstrates that the Achilles heel of these full-range drivers is far more infamous than their many virtues. And that's true regardless over whether such opinionates have ever even heard a Lowther-based speaker in the flesh. Being mostly known for one's shortcomings by repute and from the distance makes not only for one massively foregone conclusion. It also erects a perception barrier that anyone working with these devices in production loudspeakers must tackle. Put more succinctly, you're liably written off before you ever got a chance to make your point. That would be too bad.


Jacob George of Rethm is the first to agree that yes, unmodified and simply stuck into any old cabinet, Lowthers
do suffer from an upper midrange peakiness that veritably honks at the listener. He would further admit that to get decent bass performance from these drivers poses real engineering challenges in the driver loading department. Which raises the obvious question: If both bystanders and intimates agree that these drivers have problems, why even bother? The answer boils down to the promise of zero-crossover, zero phase-shift, zero time-delay, zero-lobing coherence. The whole single-driver ideal is to loudspeaker designers what a zero NFB single-ended triode is to amplifier builders - minimum mechanical and electrical complexity to pass the fragile and complex music signal fully intact. More importantly, to pass it in one piece that doesn't require reassembly in the listener's ear/brain apparatus: Speaking with one single voice rather than many (forked tongue, anybody?). Immediacy. Directness. Clarity. Transparency. These are the bewitching qualities that compel designers like Jacob to brave the many obstacles of fabricating commercially successful single-driver Lowther models.

But nobody said that was easy. A single glance at Jacob's The Second -- incidentally his first-ever design -- immediately telegraphs unconventionality, something borne from years of architectural training and practice (including four years at the Brooklyn School of Architecture/Pratt Institute); his gift for thinking outside of the box; and a concise aural image of his ideal which is firmly imprinted in his mind. While you're still close to the photo above, focus on the far speaker. Imagine yourself as the driver rear wave. Travel back from the DX-4 Lowther through a gradually expanding, formed plywood (not PVC!) tube of semi-spherical profile. Stay horizontal, then follow the downward slope of the cabinet above the two holes. Go vertical toward the floor past the big hole, hang a right angle to now move underneath it and return to the cabinet's front. Then hang another 90-degree turn to go straight up until you reach the bottom of the driver. Now turn back again for your first 360-degree loop of continuously expanding and widening tunnel fun. Commence downward again (just below your first passage this time) until you come to a fork in the road: A smaller portion of you-as-the-rearwave will exit through an opening inside the upper hole, the far larger portion of you will travel a bit farther to exit through a similar opening in the larger hole.


But that's not all. In order to prevent this rear wave from reflecting off the first change-of-direction barrier back through the diaphragm -- a major flaw of most Lowther-based designs according to Jacob -- our clever engineer affixes a rather sizable expanded polystyrene attachment to the driver magnet to create a compression chamber that effectively prevents both back flow and accelerates the rear wave to commence its hasty progress through the circular rear-horn/TL-hybrid labyrinth.