A little while ago, TDL Electronics Limited used to be the British speaker manufacturer that championed the consumer advantages of transmission line principles in bass reflex ported speaker cabinet design. Making mostly floor-standers, their speakers gained some attention of export markets and there were some multiple drive unit monsters headed for the USA in the late nineties.
With a complex folded cavity inside the speaker to delay the reverse phase acoustic wave generated at the rear of the bass driver (but allowing it to supplement the wave generated in front without cancellation), transmission line speakers are efficient to drive and are capable of very low and distinct bass.
I bought this pair of new Studio 1M’s just after the original company closed down and was sold. Indeed I was quite lucky to get £500 shaved off the original £999 selling price, after dragging my existing equipment down to a listening room in my local Hi-Fi shop and listening to a few alternatives which came nowhere close for the bass!
They are 1 metre in height hence the 1M in the model name, and came wandering into the house in two rather large cardboard boxes – which initially caused a few domestic concerns around here.
TDL’s speakers then characteristically had a mostly flat neutral ‘transparent’ response over the normal audio bandwidth due to their usage of innovative materials and custom manufactured drivers. My Studio 1M speakers feature stiff aluminium diaphragm drivers for both the tweeter and the bass driver, a design choice taken to reduce the crossover response mismatch found with usage of different materials.
The benefits are particularly telling with brass instruments, percussion and female vocals which really project themselves into my listening room. I have a small collection of demo CD recordings distributed by equipment manufacturers themselves (Naim, B&W, Dali) that impresses me in a way that music commercially designed ‘loud’ for the radio sadly doesn’t. Oh well.
So, moving on to the bass and holding on to the roof tiles…
My Mission Cyrus ‘Straight Line’ amplifier does not feature a bass control (or allow any other tonal modifications) but with these speakers it does manage to generate quite a weighty soundstage for recordings that have a naturally deep content like church organs, stringed bass and the occasional thumpin’ dance track.
The heritage of TDL grew from an earlier 70’s company called IMF whose history is told here. Looking forward there are professional transmission line products by PMC that are used in recording and broadcast studios including those of the BBC.
The TDL company website of today includes some history and descriptions of the internals of these speakers, but the current range produced are quite different products made abroad using traditional components and designs. They are now owned by The Audio Partnership – Julian Richer’s ghostly collection of former great British Hi-Fi companies. eBay is probably the best place to find an original TDL Transmission Line model.
Interestingly, Bose seem to have taken some of the transmission line delay principles and built them into their over-hyped clock radio, which does sound impressive for bass (I’ve played with one!) but loses it tonally in comparison to a proper Hi-Fi system (and a few midi-systems as well …)