The Loudspeaker - Some things never change

For bass speakers (well below 100 Hz) the critical parameter is how much air volume you can move around at a specific frequency.

  • You can use a single medium size speaker with a long throw
  • You can use a speaker with a large code (250 - 500 mm). The problem is how to make a solid cone acting as a rigid piston.
  • Use multiple smaller units, but the problem is "fingered" angular response at higher frequencies.

There is also the general rule of speaker box volume, lowest frequency and efficiency, you can optimize one with the cost of the others.

When the available power these days costs practically nothing, you only have to optimize between speaker volume and lowest frequency response.

IMHO for typical home applications, a subwofer in the middle of the room is the best solution, in which all three alternatives above can be used with two or even five speakers for directivity.

Now the question is, where should the cut-off frequency between the subwofer and the rest of the speakers should be located, perhaps between 50 and 150 Hz depending of the room size. Moving it up to 150 Hz would allow optimizing the mid and high frequency response in small cabinets.

Reply to
upsidedown
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Reply to
jurb6006

** That's the "plate supply" voltage for the particular configuration.

NOT the max permissable plate voltage which IS 2kV.

** Then you have not seen the "MusicMan" models that use 2x6L6 to get 100w.

Or the much older German "Dynacord" models that use the same configuation.

.... Phil

Reply to
Phil Allison

** Any of the Dynacord 100W models from the 1960s and 70s qualify.

IME, anything an EL34 can do - a decent 6L6 can do as well.

... Phil

Reply to
Phil Allison

Reply to
upsidedown

The plate or the glass ?

Really. When the horizontal (line) output tube in TVs lost drive they would redplate. There was some extra good version of the 6MJ6 IIRC that was pret ty damn tough. One time I saw not the plate melted, but the glass. It made an indent like an inny belly button.

I guess that's why some of those transmitting tubes are made of metal.

Reply to
jurb6006

When I built my own speaker system some years ago (an MTM array in a tower, with integral side-mounted subwoofer located near the floor) I experimented with several crossover frequencies, and found that for this system 200 Hz sounded best.

There exists an effect caused by "floor reflection" - the direct wave from each driver reaches the ear and combines with a delayed wavefront which reflects from the floor. This can result in a "suckout" (audible dip in frequency response) at the frequency at which the two wavefronts are out of phase. The frequency at which this occurs depends a lot on the height of the driver above the floor (since this affects the difference in length between the direct and reflected path).

In the case of my speaker system, it was advantageous to set the crossover frequency relatively high. The crossover frequency was

*above* the "floor reflection suckout" frequency for the midbass/midrange drivers in the MTM array, but was *above* the suckout frequency for the subwoofer mounted down low close to the floor. Net result: midbass with no suckout.

I tried both lower crossover frequencies (100 and 140 Hz) and a higher frequency (275 Hz) and neither sounded as good with these drivers and the cabinet setup I had built. I'm not sure a 200 Hz crossover frequency would have worked well in a system using a single subwoofer... at 200 Hz we're starting to hear some directionality to the sound.

So... don't be afraid to experiment.

Reply to
Dave Platt

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