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Re: "Fast TL's"

"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."

That's why i said that i prefer sealed and stuffed boxes. When your ears and measurements jive, something has got to be right !!!

"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)."

While ALL vented systems will show dual resonances and impedance peaks, TL's ( if properly designed ) do this the least. Their frequency response is typically very linear in the bass region with little to no noticeable "humps" in the lower regions. This results in both tighter bass and a more consistent load for the amp.

"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."

What you are describing is essentially a large "vario-vent" design. While it does offer similar electrical measurements and characteristics of a TL, the sound of the system "in-room" is measurably different ( as you noted ).

"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."

While the systems' Q is quite important and will tell quite a bit about what you should expect from the sound, I have to agree with Clayton on this. A sealed box with a very low Q ( 0.5 ) typically sounds very "dry" whereas one with a reasonable Q ( 0.7 ) will tend to sound very full without the nasty ringing of a higher Q design. The very low Q system will typically sound like the driver is not reproducing ALL of the notes while systems with too high of a Q will ring and sound ill-defined. You have to have a meeting point between the two to sound well balanced.

"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."

We are dealing with two different things here under one subject. YES, speed does matter a great deal when mating dynamic woofers with planar's or E-stat's. If the woofers don't respond fast enough with the proper damping, they will always sound slightly bloated ( compared to the razor sharp & fast mid / treble ) and slightly behind the pace of the rest of the music. This tends to give a very disjointed sound and can really slaughter the performance of an otherwise excellent system.

The other half of the equation is radiation pattern ( as you mentioned ). Bass that is emanating from a point source will always sound measurably different than a multi driver / multi direction array. This is especially true when the rest of the system sounds much more open and does contain a higher amount of reflected energy.

"Thin mint" speakers will typically produce a specific polar pattern. Speaker placement and room acoustics can drastically effect this, and it may be tough to deal with in some specific installations. If the woofers are crossed over too high or don't exhibit a similar radiation pattern, they will be far too easy to localize. This will blue the soundstage and imaging to a very measurable effect. Tonal balance might be quite good, but the system just won't sound "cohesive" or "hold together". Sean
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