Edgar

All very true, for metallurgical applications requiring great toughness. I am skeptical about any claims for vacuum tube innards, however. In fact, I am concerned about what might happen to some of those delicate internal parts when brought to such a low temperature -- will they crack due to different coefficients of thermal expansion (contraction, in this case) than the parts to which they are attached? Will they shatter with the slightest jostling? Will the seal around the pins be compromised? Any number of ill effects come to mind, and frankly I just don't know whether they are genuine concerns or much ado about nothing.

I tried it with a tub of Cherry Garcia and got a killer brain freeze.

Markertek Full Compass

More detail, with an example: If you need, say, a 100Hz 3rd order Bessel crossover, then create a 144 Hz 2nd order Butterworth crossover. In the woofer signal path, insert a 132 Hz 1st order lowpass filter after the crossover. In the tweeter path, insert a 132 Hz 1st order highpass filter after the crossover. The combination of the 2nd order Butterworth crossover and the 1st order filters will create a very close approximation to a 3rd order Bessel crossover. For cutoff frequencies other than 100 Hz, just scale accordingly. In general, this technique does not work for higher order Bessel crossovers. It just happens that a 3rd order Bessel filter contains a 2nd order section that is very close to a Butterworth characteristic. Greg

If they offer a 1st order filter after the crossover, then you can cascade a 2nd order Butterworth crossover with a 1st order LPF in the woofer path and with a 1st order HPF in the tweeter path. Greg

The denominator polynomial for a 3rd order Bessel filter is: s3 + 6s2 + 15s + 15 This can be decomposed into the cascade of a 2nd order section and a 1st order section: (s2 + 3.67781464537391s + 6.45943269348336)(s + 2.32218535462609) The 2nd order section has a Q of 0.69105, which is really close to the Q of a Butterworth filter (0.70711). So you could construct a very close approximation to a 3rd order Bessel filter as the cascade of a 2nd order Butterworth and a 1st order filter. You just need to figure out the cutoff frequencies for the constituent filters. Greg

It's the same thing that makes people love Chevy over Ford, the Packers over the Bears, or Harley Davidson over other motorcycles: fanaticism.

Pretty much any CAD program will create a DXF. I use TurboCAD and, frankly, don't even bother with DXF unless I need to transfer the drawing to another person. As for the design of the horn itself, a little mathematical knowledge plus Hornresp will get you started. Greg

Try Audio and Stereo Review.

I've been through similar, only with FedEx. They admitted fault. I filled out all of the paperwork and jumped through all of the hoops. They still owe me $$ for their truck knocking over the basketball goal by my driveway, since 2008. It's just not worth my time to pursue it, and they know it.

Having grown up in the St Louis area, and now just having moved back, this seems very typical to me for this time of the year. We've gotten much better at predicting and detecting storms than we were when I was young, but the storms themselves seem pretty much the same as they have always been.

They said last night on The Weather Channel that the tornado sirens went off twenty minutes before the tornado hit. So many storms hit this area so often that it's easy to become complacent, to lose that sense of urgency. I do it myself. My sympathy goes out to the people who lost so much.

Is he mistaking the woofer cone for a horn?

My portable computer, which I only use for email and browsing, got that a week or so ago. I have no idea how it got in, for the computer was (supposedly) protected. The first time I ran antivirus software to eradicate it, it launched so many Windows utilities that the CPU usage went to 100% and the antivirus software ran at a snail's pace. Ultimately I ran several antivirus and antimalware programs (which took several days); each said that it had removed it but every time it returned when I rebooted. The only way I was able to remove it completely was to wipe the HD and do a clean install. This is a nasty one.

From the "crude but effective, and very sturdy" department: stands. []

Alas, I am currently "bikeless".

If you mean tube shields, then about all they do is cause the tube to run hotter; see Fig. 6 in the first paper here.

Here.

Watch video.

Tried hunting for a job lately? Same kind of situation.

A while ago I saw a news bit that said that Bose was doing research on MR-based shock absorbers. Yes, THAT Bose. Believe it or not.

That's why I listen to vacuum tubes. They'll never achieve self-awareness. They'll just sit in the corner of the room and glow warmly.

See page 25 of Keele's paper.

I've seen them both ways, and I don't know when the change was made. The pair that I have does not have the center brace. Somewhere I have response graphs from the 9040 series, but I cannot locate them at the moment. I recall EV stating that they loaded down to around 300 Hz, with a recommended crossover at 500 Hz. But I also seem to recall some anomalies in the response between 500 and 700 Hz, leading me to conclude that 700 Hz might be a better choice. Mine are not in use at the moment, so I cannot comment beyond that. The 9040A is approximately the same width and depth as the K402; about 6" less in height. But that curved front makes it difficult to integrate into a cabinet of any reasonable shape. Greg

Several years ago I shipped (commercially) a set of large speakers from Canada to the US. They had to go through Customs, but because the speakers had been made in the USA, the process was streamlined considerably by NAFTA. Seriously, it went from a 1" thick stack of paperwork to a single signature. In my travels, I have found it to be MUCH more difficult to cross back into the US than to cross into Canada, despite the fact that I am a US citizen. I can't imagine how difficult it might get if they suspect you of carrying contraband. I strongly urge you to follow the rules on this. Don't try to take any short cuts. The stakes are too high and the consequences too dire. Greg