No, they do not have a weight. The black thing you're seeing is most likely the pole piece. The only possible added mechanical resistance is the second "damper" spider which is mounted on top of the main spider; but I believe that is more to keep the voice coil straight in its assembly than anything else. The Weber motors do not have the same mechanical resistance as a regular speaker, and due to being either weakly magnetized or not magnetized at all, the motors do not exhibit anywhere near the same motion as a regular speaker.bancika wrote:Weber motors seem to have some sort of a weight (that black thing on the top) that simulates cone resistance using gravity. Provided I'm right that also means you can mount them only one way - weight facing up.
They just sit there and get hot - very hot. I am sure if you tried to put a continuous 100 watts through the 100 watt motor it would likely burn up. Despite that, I've never seen a Weber attenuator returned with a burned up motor. The failures of the MASS units are almost always either due to failures of the junky rheostats (they tend to fall apart) and sometimes failure of the impedance matching resistors (from gross overheating, probably due to overpowering). With the resistors, more often it's the contact glue they use to hold them in place which often fails and emits a noxious odor and sometimes even begins smoking. On numerous occasions I suggested using proper thermal epoxy to make this bond, but I was always ignored - obviously epoxy is too expensive for them, though it only requires a small amount to get a good bond, as opposed to the gallons of contact cement and super glue they go through and still get a crappy bond. The only failures I've ever seen in the motors are on a couple units in which the tinsel lead wires (located underneath the spider on the interior of the assembly) were improperly insulated and were shorting against the metal chassis. Those lead wires should be entirely coated with black insulated glue, but a couple of the former contract builders didn't do so, and if the uninsulated wires have too much slack they may short as described. I've only seen that happen a couple times.
To address the other points; yes, rotary L-Pads differ from standard rheostats because they have two resistance tracks of different value which are intended to provide the correct impedance match with the given load throughout its sweep. A rheostat doesn't keep a constant resistance with the load in parallel with it the way that an L-Pad does, that's why I prefer the L-Pads. And yes, I believe those are intended for lower-current things like tweeters, though 100 watts into 8 ohms is still 100 watts into 8 ohms... but at what nominal frequency is that measured - I assume the current through the load would be the same at a given power level and frequency? Even though that resistance would change depending on its AC impedance, I'm going to assume that the given resistance of an L-Pad is specific to the nominal AC impedance of the load for which it is intended. But yeah, anyway, that 100 watt one I tried started smoking, though it didn't actually burn up or fail - maybe it was just some stuff on it that started smoking from the heat even though the device itself was still fine. I'll need to experiment with it some more and observe closely what happens when it is adjusted to a heavy amount of attenuation with a large amount of power through it. I think I should do this experiment with a cheap solid state amp.
They have those stereo ones; you could use both halves wired in parallel for more power handling at a different impedance.
And if you used some series/parallel resistors with the L-Pad to match to different resistances, this would also divide the power dissipation duties to take some of the heat off the rotary L-Pad (literally!).