Are my speakers supposed to do this?

Hi all. Thanks for reading this thread. I just put a new preamp (Eastern Electric Minimax) into my system and am noticing some weirdness in my speakers. When everything is on but no music is playing I noticed that both the left and right drivers of my monitors (Tyler Acoustic taylos) are moving forward and backwards very slowly but at a very steady rhythm. Takes about a second for them to move forward and then another second to move back. They repeat this cycle until I turn the amp off. This doesn't seem normal to me. I never noticed this with my previous pre. When I play music through the system it seems okay, no obvious distortion although I do notice my drivers moving (from my listening position 7 feet away) in a similar way - slow in and out although it doesn't seem as cyclical.

When I first put the Minimax preamp into my system there was a very loud hum and some static pops coming through the speakers. I lifted the ground on the pre with a cheater plug and the hum & static went away.

Did I damage my speakers? I want to try and trouble shoot but am afraid that damage already may have been done and I don't want to make it worse.

I've no idea what's high-freequency DC(probably something brand-new in EE) but BAT has tendency to drain some DC at the output.
Probably the same story with your pre which isn't neccessary because of bad tube...
DC ??? absolutely not. High frequency DC...what is that ??? Please tell us how high frequency it is, DC with frequency and still called DC ???

What you are experiencing is subfrequency motorboating, or, in other words, an unstable power amp that is probably only marginally stable with the speakers you are using. You might have been using a pre with a higher output impedance and just got away with it. However, with the low
Z of the EE MM, that puppy becomes likely unstable.

Anyway, w/o knowing what you are using, it's just my logical conclusion, not gospel...

The output impedance of the EE MM is 1.5Kohm which is high for a tube pre if I'm understanding this right. My previous pre had a LOWER Z and I had no problems matching with my Belles SS amp (100 Kohms). There is definitely something wrong with the pre. (Speak to Bill about this. The Belles is solid state.)

Sorry if I used the term High frequency DC out of context. I don't consider myself an electronics authority and I was attempting to interpet the explanation of a similair problem that I had.

Just to clarify, I had a problem with a phono stage that caused very unusual problems with my system that had baffled the manufacturer and was the most frustrating audio situation that I ever encountered.

The phono stage, a BAT P5, connected to a BAY VK 30se, caused the power tubes (KT-88) in my amp to light up. I didn't even play a recording and this would occur. I then used a solid state amp and instead of the amp reacting, the problem manifested itself in my speakers where the mid range drivers extended way out then retracted as Tooter has experienced. Note that the woofers didn't move.

I was told that it must be the amp, the tubes, the interconnects, the power conditioner etc.. I checked everything but the problem kepted happenning. At the time, BAT didn't believe that the problem was coming from the P5, so I sent the P5 to a 3rd party & they said the there was an excessive DC leak out of the P5 and they called BAT to convince them. Additionally, I was told that since only the mid range drivers reacted and that no sound was heard lent itself to a frequency that was inaudible.

Anyhow, a DC filter was put on the P5 and the problem was solved. BAT had never seen anything like this at the time, which was 2 years ago.

Fortunatly, Tooter is getting a replacement and hopefully this will be a happy ending.

I still cannot think of a clue there is anything wrong the EE MM but the power amp. It is because any amp that would have a problem being driven by any source having a Z=1.5k isn't worth its design...