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"Fast TL's"

Posted by mrbiggleswurth on April 22, 2000 at 09:53:38

In Reply to: Kind of a moot point ... posted by Sean on April 21, 2000 at 19:19:21:

Impulse response will show that only a critically damped system has the least stored energy at resonance. It is the one that rings the least.

Impulse and group delay measurements will show that TLs do not qualify as the most accurate.

Transmission lines have dual, rounded impedance peaks that show they are resonant systems very similar to a vented systems. The peaks are smoothed over because of all the stuffing (the "vent" is damped). If you were to calculate the total internal volume of a given TL and then just build a big box with the same internal volume and then tune the enclosure with a large OD vent (the same area as the mouth of the TL) to the same resonant point of the TL, and then stuff the enclosure vent with Dacron or something similar, you will get almost exactly the same result. In-room this may be impossible, because the relative location of the mouth and woofer of a TL may generate substantially different power response than that of just a huge vented system. But the fundamental behavior of the system will be the same.

No bass system is "fast." A woofer's ability to oscillate at low frequencies means that by definition it is fast enough. There are many things that account for a subjectively "fast" sound, and most of them have to do with Q and distortion. Lower Q drivers are better damped, either electrically or mechanically, and they have a way of just sounding "tighter" and "quicker" that woofs of higher Q. And the final Q of the total system also dictates this subjective quality.

There are many reasons why it is tough to marry a cone woofer subwoofer to a typical electrostat, but it has nothing to do with the "speed" of the woofer. Most simply have to do with the fact that cone woofers just sound completely different in the midrange to electrostats, and this big disparity tends to be easily heard in a transition from one to another. Also radiation pattern: you are going from a dipole to a monopole, probably at some poorly chosen crossover point, so the power response is radically different between the two in the bass range.

The only system that I have ever heard that I thought successfully married a cone woofer sub to an electrostat was/is Gradient, with their sub for the ESL 63. And that design is an open baffle dipole.

Biggleswurth

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