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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.

Thanks.
tooter
ykm
5 posts
 
Tooter, I was trying to find out any possible clue so to ask the speakers too. If the pre was "causing" your power amp motor boating, the amp is marginally stable. There are many thousand pres out there, the pres you used did not cause any problem with your power amp does not mean it was the EE MM if the power amp was marginally stable. This is not wrong because a hifi equipment designer would sometimes want his gear to deliver better sound with some trade off of slight stability or output power or heat generation or.... An engineer finds a power amp motor boating will first of all fix the power amp. Apologise if I have made some agressive assumption before knowing all the designs of your gears.

Regards,
Ykm
tooter OP
85 posts
 
Ykm,

No offense taken! No need to apologize. I am just not clear on what you mean by power amp "motor boating" and "marginally stable". Can you elaborate? What part of the amp's design is deficient which would lead to it being "unstable." I'm not an engineer but Belles amps have gotten great reviews and I've used them with many speakers and pres without incident.

thanks.
ykm
5 posts
 
Tooter, first of all gears got great reviews do not necessary mean their spec. are perfect. I understand EE MM also got many great reviews too. Motor boating is some low frequency oscillation and that you saw the woofer was pushed in and out. If the oscillation is "faster" and "louder" in your case, you would hear it like the sound of an old motor boat and that's how it came the term. A few things can cause such oscillation, incorrect amount of nfb, decoupling caps do not have enough value, bad design of the PS...I am not a real expert, but have diyed quite many amps. Audio gears are very different from other electric appliances, spec. is one thing, but sound performance is the most concerned. There many many many audio gears in the market. Every engineer does them in a different way. You cannot expect when EE made his gears and when Belle made his gears to be able to match the rest of the world. If you search around, there are many many many sayings such and such pres don't work with such and such amps etc. But when you check them, they are all fine. As soon as you connect them together, they are "loaded" and affected by each other, say DC leakage, impedance...etc. So at the end of the day, your sepckers, Belles and EE MM are all well checked okay. That's all the fun of playing with audio I look at it.

Regards,
Ykm
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