hissing sound from rt floor standing speaker, powered subwoofer, WITH NO WIRES ATTACHED

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ruddyduddy
ruddyduddy Posts: 1
in Speakers
My left speaker just started making a fairly loud hissing sound. I unplugged the power. Unplugged the wires and the speaker is freestanding in the middle of the room hissing away, I believe from the powered subwoofer. ?????????? LSi25
Nothing is attached to this speaker!!
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  • shs
    shs Posts: 105
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    Perhaps is there a cat trapped inside? Or maybe a snake?
    SONY VPL-VW385ES, Da-Lite 92" 0.9 HD progressive 16x9 screen, Apple TV 4K, Oppo UDP 203, Anthem AVM 60, D-Sonic 4000 (800x3, 400x4) for bed layer, 2 Crown XLS 1002 (225x4) for Atmos; Speakers: Polk LSiM 705s, 703 front, 4 702F/X surround, 4 Polk TL3 (Atmos), Velodyne DD15 Subwoofer.
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  • mhardy6647
    mhardy6647 Posts: 33,066
    edited February 2021
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    If it has an amplifier in it, yes, you are hearing amplifier hiss. Based on what I've read on the internet, detectable levels of such hiss is more or less endemic in powered loudspeakers.

    Now, I know ;) that many folks aren't crazy about ASR (and I get that, believe me!), but -- in the context of hiss in powered loudspeakers, this might be of interest to the OP. :)

    https://www.audiosciencereview.com/forum/index.php?threads/studio-monitor-speakers-without-hiss.11627/

    It is probably inaudible at normal listening conditionings at a normal distance from the loudspeakers. I don't know -- but it may well be normal.
    That said, I'll defer to experts on this particular loudspeaker.


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  • shs
    shs Posts: 105
    edited February 2021
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    Perhaps the capacitors in power supply for the amplifier has to drain before it will stop hissing. Or, sure you are not missing a cat?
    SONY VPL-VW385ES, Da-Lite 92" 0.9 HD progressive 16x9 screen, Apple TV 4K, Oppo UDP 203, Anthem AVM 60, D-Sonic 4000 (800x3, 400x4) for bed layer, 2 Crown XLS 1002 (225x4) for Atmos; Speakers: Polk LSiM 705s, 703 front, 4 702F/X surround, 4 Polk TL3 (Atmos), Velodyne DD15 Subwoofer.
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  • WLDock
    WLDock Posts: 3,073
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    Its most likely leaking caps.

    84482.jpg
    2.2 Office Setup | LG 29UB55 21:9 UltraWide | HP Probook 630 G8 | Dell Latitude | Cabasse Stream Amp 100 | Boston Acoustics VS 240 | AUDIORAX Desk Stands | Mirage Omni S8 sub1 | Mirage Omni S8 Sub2
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  • mhardy6647
    mhardy6647 Posts: 33,066
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    Rick88 wrote: »
    ⬆⬆ Yes, but:

    "I unplugged the power. Unplugged the wires and the speaker"

    "Nothing is attached to this speaker!!"

    oh, oops. :)
    sorry :/

    Yeah, I'll cast a 'capacitor' vote, too!
    It can happen.

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  • mhardy6647
    mhardy6647 Posts: 33,066
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    The capacitors store charge. On power off, depending on the design, they may slowly discharge, running the amp until they drain completely. If so, the hiss will fade more or less slowly (depends on the caps and any bleeder resistors in the power supply).

    My vacuum tube amplifier will play for 30 seconds or so after turn-off from the residual DC in the P/S caps.
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