Do the woofers move with the volume turned turned all the way down ? Sean
very simple, your amps don't like the speakers and are unstable into the load they present for whatever reason. Either impedence/effeciency of the speakers or design of the amp/input impedence-output sensitivity. This is a guess though as I am not stating this from my own knowledge but from what I have recently read in Listner. Go ahead and correct me anyone if this sounds wrong.
The amp is either oscillating at a very low frequency or passing DC. Both are signs of an amp in need of a thorough inspection and repair / re-alignment. I would advise against running the amps until you can fully diagnose the situation. Continuing to do so could result in major damage to the speaker, amp or possibly both. Sean
Just a note: For those that think that DC will cause a driver to throw forward and stay in that position, that is not necessarily correct. The DC level could be fluctuating up and down. As such, the driver would move forward, but could appear to "flutter" or move in and out as the amount of DC voltage varied. It would never take a "full stroke" ( positive push forward and then the accompanying negative stroke backwards ) as that would represent an AC signal. DC would only move in one direction but could be moving or fluctuating none the less.
One could actually play music over the top of this, but you would have to present a higher level of AC voltage ( music signal ) to the speaker than the DC level that was leaking into it. The higher AC voltage would actually "muscle" the speaker into moving, but it wouldn't be near as sharp, clean or clear as if there were no DC present. Needless to say, there would be a tremendous amount of heat build-up in the speakers' voice coil and "melt-down" could occur. In severe cases, the driver will literally "flame out". I've seen this happen at rock concerts. The unknowing crowd simply thought that it was "special effects".
Further damage to the amp could also occur, as there is a drastic amount of reflected voltage fed back to the amp in a situation like that. The speaker is resisting movement due to being partially locked in place by the DC so some of the AC music signal is not absorbed and sent back to the amp.
Keep in mind that it is also possible for a driver to "suck in" or move backwards rather than go forwards when DC is present. This would have to do with the polarity of the DC voltage and how it is connected to the speaker. Sean
Are you sure its not the components upstream from the amp? You can check this effect by simply removing the input connections from the amp, and unplugging all of the gear that is upstream.
I have seen ground loops / ground problems cause this...
If it is the amp -- it seems like a power supply issue -- this may happen due to a bad diode, regulator tube, or capacitor. There are certainly other things it could be - these are the most common ones I have run across...
Good luck -- and follow Sean's advice if you can't quickly figure it out...
Unless it's a rare output transformerless (OTL) design, your amp has an output transformer between the power tubes and the speaker. This transformer will not pass DC unless it is seriously defective, in which case you'd likely have more severe symptoms such as smoke and overheated output tubes.
If it's not coming from an upstream component, then as mentioned above, low frequency oscillation is the likely culprit.
I agree that it's time for a trip to the shop.
I have no idea what it might be. Keep in mind that some speakers are capable of going MUCH lower in frequency response than others are. I have one set of speakers that will throw madly at 5 Hz while others do not flicker in the least. As such, your ESS's with their passive radiator loading may be revealing a problem that the other speakers simply can't reveal. Either way, i would not chance damaging ANY of your equipment without first having them checked out.
Glen, i've seen flame-out's at several different shows. The most significant one that i remember was at one of my buddie's shows. His bass amp ( Gallien Krueger ) started leaking DC and the speakers began smoking and then literally spit out flames. People thought it was like Ace Frehley's old "smoking Les Paul" routine. The reason that i remember this one so vividly though is that they were MY bass cabinets that he ignited !!! Needless to say, he replaced the drivers with brand new ones. I didn't come out of that one too bad, as i ended up with 4 brand new 18" drivers that cost about $180 apiece : ) Sean
Kona, if you have switched the speakers and it is still on the same channel and have changed amps and it is still on the same channel, then the problem is coming from before the amp. From your description, it is a subsonic frequency. When you used a different pair of speakers, they may not respond to a frequency that low and made you think that they weren't having the problem. Disconnect the preamp from the amp's inputs and see if that stops it. I think it's in the preamp from what you've described. Since it happened when the volume was all the way down, that pretty well eliminated any source problems. When you changed amps, that eliminated the amp. When you switched speakers and the problem remained on the same channel, that eliminated the speaker. The preamp is the only thing left. Try a different preamp.