A really interesting amplifier/loudspeaker/EMI (or RFI) problem Someplace Else

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mhardy6647
mhardy6647 Posts: 33,049
in Electronics
With some trepidation ;)
I got sucked into a really interesting troubleshooting discussion at (don't judge me!) ASR last night.
There is a fellow who posted over there about some induced noise (a buzzy hum -- like a ground loop hum) that his center channel loudspeaker (a B&W speaker) is picking up from his big (and, I think, new or fairly new) McIntosh MC255 5-channel A/V power amp.
Cutting to the chase: The amp induces this sound in the (passive) center channel speaker even if the speaker is not connected to anything. The speaker is receiving, detecting, and transducing the induced hum. That seems... odd. Nigh-on Twilight Zone odd. ;)
Now -- his amp and speaker are in very cramped quarters, but the question is: what exactly the heck is going on here? More to the point, is the EMI from the amp normal or is there something funny going on with the amp?
If (?!) any of you is suitably curious -- here's a link to the thread.
https://www.audiosciencereview.com/forum/index.php?threads/mcintosh-transformer-causing-noise-in-speakers-while-disconnected.53114/

I was shootin' from the hip and not much help, in full disclosure.
It's a fascinating observation, though.

Y'all got any thoughts?

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Comments

  • F1nut
    F1nut Posts: 49,806
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    Dump the B&W stuff.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • mhardy6647
    mhardy6647 Posts: 33,049
    edited March 20
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    F1nut wrote: »
    Dump the B&W stuff.
    Point taken. :)
    I wanted to say that myself, I must admit -- I am not a fan.
    I was atypically diplomatic on that point, though.
    I mean -- I'd just move the amp, but that doesn't seem to be on the OP's agenda.
    B&W and Mac seems like a relatively uncommon combination to me -- but I don't pay that much attention to either brand, so I could be wrong. I wonder if the speaker design (XO?) has something really awry that turns it into an LF radio. :|
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  • F1nut
    F1nut Posts: 49,806
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    mhardy6647 wrote: »
    F1nut wrote: »
    Dump the B&W stuff.
    Point taken. :)
    I wanted to say that myself, I must admit -- I am not a fan.
    I was atypically diplomatic on that point, though.
    I mean -- I'd just move the amp, but that doesn't seem to be on the OP's agenda.
    B&W and Mac seems like a relatively uncommon combination to me -- but I don't pay that much attention to either brand, so I could be wrong. I wonder if the speaker design (XO?) has something really awry that turns it into an LF radio. :|

    I doubt the issue is the speakers, I just don't like their house sound.

    I suspect the amp has an issue causing it transmit a strong EMI field. If the amp is brand new the owner should contact their dealer or McIntosh directly. If bought used either return it or have it serviced.

    Did the person try putting a different brand of speaker near the amp?
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • mhardy6647
    mhardy6647 Posts: 33,049
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    F1nut wrote: »
    ...
    Did the person try putting a different brand of speaker near the amp?
    That is a really good question! Thank you!!
    My impression is that the amp was purchased new and is brand new or, at least, pretty darned new.
    He did just get the phone number & names of the folks to call at Mac.
    Call McIntosh's Tech Support line (607)723-3512 ask for Chuck Hinton(Tech Support) or John Messemer(Service Manager). There maybe other techs there that could help too.


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  • pitdogg2
    pitdogg2 Posts: 24,585
    edited March 20
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    I guess that guy has never heard of nor seen a decent amp stand..
    Personally I'd move the amp to an amp stand, it looks to be AWFUL heavy for that MDF it is resting on. I'd move the receiver to the bottom center and get those wifi antennas as far from the speaker as I could. Do I think it could be the wifi part ? Personally I do not know as I've never had anything with those. Unless he's tried it he may never know. A couple of well placed strategic holes with a hole saw on a drill and it will look great and be much more accomodating for the receiver.

    That to me that looks like it is one well placed bump from a complete collapse to the diagonal position.
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  • Clipdat
    Clipdat Posts: 12,608
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    Inductive coupling? I got nothin
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  • mhardy6647
    mhardy6647 Posts: 33,049
    edited March 20
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    Definitely inductive coupling -- but with no active components in the loudspeaker (!) it's kind of spooky.
    Most likely, something 'nonlinear' in the speaker (perhaps a 'defect' - minor imperfection - in a voicecoil or crossover coil, e.g.) is detecting (in the sense of a radio's detector, usually a diode) the radiated signal (technically EMI, practically speaking, low frequency RFI) and that detected signal is stong enough to vibrate the speaker cone(s) after being transduced by the drivers' electromagnetic (voicecoil/magnet) "motors".

    Pretty weird. :p

    Speakers that "play" with no deliberately added signal (or power) aren't unknown (I gave an example of one from my childhood in the maelstrom of that thread) -- but it's not quite an everyday occurrence, especially with not a particularly sensitive loudspeaker. :)

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  • Clipdat
    Clipdat Posts: 12,608
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    Take away is obviously never use any products from B&W or McIntosh, and certainly not together in close proximity in the same system. Duh. I thought everyone knew this.
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  • nooshinjohn
    nooshinjohn Posts: 25,102
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    Clipdat wrote: »
    Take away is obviously never use any products from B&W or McIntosh, and certainly not together in close proximity in the same system. Duh. I thought everyone knew this.

    Mcintosh and B&W together does nor sound very good IMHO... Mac's with Polks, is an entirely different ball game.
    The Gear... Carver "Statement" Mono-blocks, Mcintosh C2300 Arcam AVR20, Oppo UDP-203 4K Blu-ray player, Sony XBR70x850B 4k, Polk Audio Legend L800 with height modules, L400 Center Channel Polk audio AB800 "in-wall" surrounds. Marantz MM7025 stereo amp. Simaudio Moon 680d DSD

    “When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson
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  • treitz3
    treitz3 Posts: 18,342
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    I doubt it is the wi-fi. I have a satellite unit for my mesh network and it sits right next to the power supply to the preamplifier.

    Tom
    ~ In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence. ~
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  • treitz3
    treitz3 Posts: 18,342
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    My guess would be the large toroidal xns-frmr in the amp that it's placement within said component is only a couple of inches away from the magnets of the center speaker...and in this case, it's audible. Tom
    ~ In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence. ~
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  • mhardy6647
    mhardy6647 Posts: 33,049
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    treitz3 wrote: »
    My guess would be the large toroidal xns-frmr in the amp that it's placement within said component is only a couple of inches away from the magnets of the center speaker...and in this case, it's audible. Tom

    That does in fact seem to be what it is. :#
    Great diagnosis!
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  • F1nut
    F1nut Posts: 49,806
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    treitz3 wrote: »
    My guess would be the large toroidal xns-frmr in the amp that it's placement within said component is only a couple of inches away from the magnets of the center speaker...and in this case, it's audible. Tom

    I read some of the comments at ASR. The guy is getting the noise in the L & R speakers as well, which are far away from the amp, so it is not a matter of being within a few inches of the center.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • treitz3
    treitz3 Posts: 18,342
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    I don't do ASR. Never have, never will. I would rather watch a slug do the 100 yard dash, as that would be time better spent. I was just going off of the information provided here.
    mhardy6647 wrote: »
    There is a fellow who posted over there about some induced noise (a buzzy hum -- like a ground loop hum) that his center channel loudspeaker (a B&W speaker) is picking up from his big (and, I think, new or fairly new) McIntosh MC255 5-channel A/V power amp.

    Tom

    ~ In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence. ~
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  • invalid
    invalid Posts: 1,279
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    It could even be a bad circuit breaker in the service panel causing the issue.
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  • mhardy6647
    mhardy6647 Posts: 33,049
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    Could certainly be some DC riding on the AC.
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