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Turntable feedback from nearby speaker

Discussion in 'Electronic Repair' started by [email protected], Dec 19, 2013.

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  1. Guest

    I've just gotten finished, (or so I thought) upgrading and servicing all the equipment in my entertainment center. I just replaced my mediocre speakers with a pair of nice 12 inch JBL's that were abandoned in the building we just bought. My turntable is an old Thorens belt drive, supported with a spring arrangement that I thought would absorb any vibration. The turntableis in a cabinet about a foot off the floor and right next to the left channel speaker. If I crank up the volume when listening to a record there is distortion, the severity directly proportional to the increase in volume. Atfirst I wasn't certain about this but you can actually "feel" the vibrations on the turntable base. There are these springs supporting the platter and arm and these springs are "stuffed" with a foam material but this vibration is coming through anyway. I know that one solution is to relocate the speaker however the room is not large enough to do this. I was thinking of putting foam under the speaker which would be easy and perhaps even a soft foam block under the turntable as well but I'm afraid that trying to support and level a turntable supported like this could be a nightmare. Does anyonehave any ideas? Thanks, Lenny
  2. Phil Allison

    Phil Allison Guest

    ** Remove the foam.
    ** Waste of effort.

    ..... Phil
  3. Guest

    I'll try removing the spring foam and see what happens. Thanks, Lenny
  4. Guest

    HEY ! Try reversing the phase of the speakers. I shit you not. that howl is the same as what you would get out of a microphone.

    One phase of the speakers (ALL OF THEM) will result in less acoustic feedback than the othsr.

    Also, get the thing off the op of it. Thsat cover. It is a reflector and amp;lifier of feedback. (sound)
  5. gregz

    gregz Guest

    Is the cabinet vibrating ? Putting the turntable further away ?

  6. Phil Allison

    Phil Allison Guest


    = Raving Nut Case
    ** ROTFLOMAO !!!!!!!!!

    ** You shit folk - big time.

    ** Not it isn't.

    ** Sure - put the stereo pair out of phase.

    Brilliant solution.

    Wot an IDIOT !!!!

    ..... Phil
  7. Guest

    "** Sure - put the stereo pair out of phase. "

    That is NOT what I said !

    Reverse the phase of ALL the speakers, then they wind in phase with each other but in the oposite phase regarding the phono cartridge.

    I've done this a whole bunch of times and sometimes it does have a quite significant effect. The problem is that it's a 50/50 chance that it could get worse. In that case reverse them all back.

    Concievably you could accomplish the same thing buy reversing both channels of the cartridge itself, but it is not designed for that. Some of them automatically ground the shell to one of the - terinals. Even if not it still kinda beelongs one way.

    Ergo, you reverse the phase of the speakers. All of them. Unnastan now kid ?
  8. wrote in message
    I'm reminded of the old joke where a patient tells his doctor that his arm
    hurts when he holds it vertically. "Then don't do that!"

    I remember when H H Scott made console phonographs. They went through quite
    some trouble preventing feedback when the turntable was in the same cabinet as
    the speakers. And I doubt their speakers went as low as the JBLs.

    Some of the suggestions are good (such putting a huge chunk o' granite under
    the 'table), but you really need to move the turntable away from the
    speakers -- and the walls.
  9. Phil Allison

    Phil Allison Guest


    ** ROTFL

    High time for you to FLY - fuckwit.

    ..... Phil
  10. Phil Allison

    Phil Allison Guest

    ** You should have - cos that at least has a chance of working.
    ** Makes no difference at all.

    I've done this a whole bunch of times and sometimes it does have a quite
    significant effect.

    ** Makes no difference at all.

    The problem is that it's a 50/50 chance that it could get worse.

    ** Makes no difference at all.

    ** Makes no difference at all.


    ..... Phil

    Unnastan now kid ?
  11. Boris Mohar

    Boris Mohar Guest

    For a real torture test play Dark Site of the Moon.
  12. Guest

    "* Makes no difference at all."

    How could you claim to be any kind of engineer and say that ?

    OK supposedly smart ****, design an oscillator with negative feedback instead of postitive and see how far you get.

    Anyway, whoever mentioned the turntable havinmg isolation, I had this Dual 1229 for a while that you could pretty much just sit right on top of the speaker. And I did. And my speakers always have bass. If it ain't got bass out the fucking door it goes.
  13. Leif Neland

    Leif Neland Guest

    Efter mange tanker skrev :
    You have to take into account the speed of sound and the distance
    between speaker and pickup.

    It does not matter if the speaker is in phase or not, it matters what
    the phase of the soundwave when it hits the record a little later.

  14. Phil Allison

    Phil Allison Guest

    "Leif Neland"
    ** If low frequency sound waves were vibrating the LP direct - there would
    be no fix other than removing the TT from the room. So this is not the usual

    Turntable feedback IS a result of the room's *structure* vibrating in
    sympathy with standing waves at particular
    wavelengths - mainly the floor if the TT is supported by that OR the walls
    if a shelf is being used. The frequencies of such standing waves depend on
    the room's dimensions and the speed of sound.

    Any TT must be isolated from these vibrations and the oldest and by far most
    effective way is by use of coil spring.

    IME, the ideal set up is 3 conical springs and enough weight above them to
    result in vertical oscillation at about 2 Hz. When displaced, the TT system
    should move freely and oscillate up and down for a couple of seconds - so
    any connecting cables must be looped and able to follow the movement easily.
    No damping material should be used.

    If done correctly, room surface vibrations no longer affect the TT - even
    jumping on the floor - so the chance of actual feedback is eliminated.

    .... Phil
  15. Guest

    It does not matter if the speaker is in phase or not, it matters what
    the phase of the soundwave when it hits the record a little later. "

    Of course it does. That is why there is a difference.

    In a given installation the way the timing is and the most prevalent feedback frequencies could result in it resonating at say, 3Khz, which is not so hard to deal with. In the opposite phase it may resonate at 65 Hz, which isALOT harder to deal with.

    Been there done that. thisis why I took the opportunity to stick it up Allison's ass, just because. Because he loves to do it to other people.

    I am still waiting for the oscillarot with negative instead of positive feedback. I got all the reponse of an Israeli government official when asked about the kill ratio on the Palestinians.

    Motherfuckers spout shit out, and then can't even come bvack and say they were wrong with dignity. They hide. Fukum.

    **** all this. It's too nice a day.

    I have PERSONAL EXPERIENCE THAT IT DOES MAKE A DIFFERENCE, and that Turet'sSymdrome motherfucker can either come out and say he was wrong or make moreof an ass out of himself trying to insult me, which is impossible because unless I have respect for the insulter, I have no respect for the insult.
  16. Guest

    I have a question for Phil. As I had mentioned earlier there are soft foam rubber inserts inside the three coil suspension springs on my turntable. You had mentioned to remove these. I am going to try that but haven't had a chance to try this yet, but why did they put that foam in there in the firstplace? Lenny
  17. Guest

    Why Phil ?

    /the spongie things are to keep the coils of the spring from resonating, remember resonance ?
  18. Guest

    BTW, removing the foam is not a good idea.
  19. wrote in message
    Correct. It provides damping.
  20. Phil Allison

    Phil Allison Guest

    "William Sommerwanker = Fuckwit Idiot "

    ** Which is not wanted in this case.

    FOAD you stinking moron.
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