PS AUDIO: The significance of the folding transmission line in a loudspeaker?

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Neil / editor in chief

One thought on “PS AUDIO: The significance of the folding transmission line in a loudspeaker?

  1. I can point to two people who disagree.

    1. John Watkinson:

    “In the transmission line loudspeaker, the back wave from the woofer is delayed by guiding it through a folded pipe that causes a delay. At some frequency, the delay will be equal to half a cycle and the delayed back wave emerging from the pipe will be in phase with the radiation from the front. It is only in the case of a sine wave that a delay is indistinguishable from an inversion and we know a sine wave carries no information. In the case of a transient, the transmission line speaker destroys the waveform. The baby is thrown out and the bathwater is retained.”
    http://www.theregister.co.uk/2014/07/02/feature_the_future_loudspeaker_design/?page=4

    and 2. Alan Shaw of Harbeth
    http://www.harbeth.co.uk/usergroup/showthread.php?2370-All-sound-to-all-speaker-to-all-men-Is-there-a-universal-speaker

    Quoting Paul McGowan:

    “At the long wavelengths found in low bass the sound being out of time by one cycle, relative to out of phase by half a cycle, is fairly meaningless to the ear and thus you really can’t hear what’s happening and you ignore this difference.”

    I am always fascinated by this sort of thing in hi fi. I think that in a complete standard-issue audiophile system there are quite a lot of these arbitrary dismissals of quite major anomalies.

    “It’s a very clever design but for cost reasons it isn’t done very often.”

    Another aspect that bemuses me. If we really think that this is the way to make the best speaker, then knocking together a few pieces of chipboard to make a folded transmission line doesn’t cost a lot of money. The impression that statements like this make, is that despite hi fi equipment costing multiple thousands of pounds, the manufacturers are *still* penny-pinching. Really? Are we sure, in fact, that a lot of high end manufacturers aren’t taking a pre-penny-pinched concept (such as a small two way bass reflex speaker) and then gilding the lily to produce a fundamentally penny-pinched speaker that costs £10,000? By starting with a clean piece of paper they might have come up with something that works so much better for the same money.

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