Unwanted subsonic information...

Discussion in 'Audio Hardware' started by VinBob, Dec 13, 2017.

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  1. VinBob

    VinBob Forum Resident Thread Starter

    Location:
    New Jersey, USA
    Hello All,

    Was wondering if someone can point me in the right direction here...

    I recently pulled off my grills to show off my speakers and to my surprise, I noticed the bottom two speaker drivers fluctuating quite a lot when playing back vinyl especially the left channel more so - this does not happen at all when playing back digital or the radio. I seem to be able to produce this no matter what LP I play and I am making sure that the LP's are flat and am even using a periphery ring on my VPI Prime to ensure they are flat and stable.

    Now, I do have a subsonic filter I can use via the 310LP phono stage, but I read in certain places that it's best to not use filtering if you can avoid and best to eliminate the root cause of the problem. I have checked the tonearm and cartridge compliance and although on the lower side of 8Hz-8.5Hz, I have been told that this should not be causing this issue and that I am compliant - would being in the 10Hz range be better and if so, can this be achieved by adding more mass on top of the cartridge via say the Soundsmith screws?

    I am somewhat at a loss here and would appreciate any suggestions/pointers for next steps as I would ideally hope this can be resolved by some change to my setup (move speakers further out or further back?) but hopefully, I don't have to look at an alternative cartridge which BTW, has maybe less than 10 hours on it. Again, what is odd, is that it is happening more on the left channel and if I swap the speakers around, it then shows more on the right...

    Am also including a link to a picture of my setup which I hope helps in providing a good visual of what I am dealing with: Audio Setup

    Cheers,
    Vin.
     
  2. Check your cable routing to ensure they aren't picking up some RF.
     
  3. Agitater

    Agitater Forum Resident

    Location:
    Toronto
    Try the subsonic filter on your phono stage. If the unwanted woofer excursions disappear, you’ve solved your problem. Anyway, I think that it was to remedy exactly this sort of problem that subsonic filters were originally developed. Stop muddy sounding lower octaves! Using the subsonic filter doesn’t affect any other part of the audible frequency range.

    You’re used to the way things sound from your system right now. Using the subsonic filter will improve the sound because it will likely dump all the unwanted woofer movement. Just remember that it will take a couple of hours of listening to get used to the improvement. Give it a chance.
     
  4. VinBob

    VinBob Forum Resident Thread Starter

    Location:
    New Jersey, USA
    Any particular cables? All the cables are well shielded and I don't see any obvious issues around this particular area, but will double check. Just FYI, I am using XLR cables from the phono stage to the preamp, so I would assume that would remove any unwanted interference right there as far as cabling issues go. Thanks for the feedback.
     
  5. VinBob

    VinBob Forum Resident Thread Starter

    Location:
    New Jersey, USA
    Thanks Agitater. I will try this as a last step over the weekend while I research any other options. What is puzzling to me, is that the left speaker shows more driver/cone movement versus the right speaker?? :confused:
     
  6. missan

    missan Forum Resident

    Location:
    Stockholm
    It's best to correct the root cause, which a high pass filter doesn't. But still it can be a good enough measure. Fixing the root cause is usually more tricky.
     
  7. VinBob

    VinBob Forum Resident Thread Starter

    Location:
    New Jersey, USA
    Indeed and ever since I got back into Vinyl, I have had nothing but tricky problems to solve and less listening to music - I sometimes wish I had stuck to digital!!! :rolleyes:
     
  8. Agitater

    Agitater Forum Resident

    Location:
    Toronto
    Well you’re eyeballing the woofer excursions, so that’s not exactly a precise measurement. Then too, maybe you’re right. Or maybe one woofer is slightly more sensitive than the other. But that might be an indication that your cartridge/stylus azimuth is slightly off. Or it could just be the way some of the LPs are recorded (with more deep junk information on the left side of the mix). Or maybe your amp is throwing a bit of very low level infrasonic or subsonic junk all by itself.
     
  9. missan

    missan Forum Resident

    Location:
    Stockholm
    Usually this problem comes from the resonance, the amplitudes are a bit too large.
     
    stuwee likes this.
  10. VinBob

    VinBob Forum Resident Thread Starter

    Location:
    New Jersey, USA
    Thanks - I don't think one woofer is more sensitive than the other as when I swapped the speakers around, I seemed to get more movement on the right channel from what I could tell...
     
  11. VinBob

    VinBob Forum Resident Thread Starter

    Location:
    New Jersey, USA
    Would that be down to an arm/cartridge compliance matching issue? If so, would there be a way to solve this without replacing either the tonearm or cartridge and not use the subsonic filter just yet?! :)
     
  12. missan

    missan Forum Resident

    Location:
    Stockholm
    IF it's a resonance problem, I would test the filter. The correct fix would be to make the arm lighter and with more damping.
     
  13. VinBob

    VinBob Forum Resident Thread Starter

    Location:
    New Jersey, USA
    Thanks. Not sure how I could make the arm lighter - its a VPI 3D 10" arm which has a mass of 9 grams. The cartridge is 7.3g, fasteners about 1g and the compliance is about 20.4 (12 x 1.7 to get the 10Hz value) which gives me a resonance of 8.46Hz. I am in the 7Hz-12Hz range so I should be OK there correct?
     
  14. ralf11

    ralf11 Forum Resident

    Location:
    Earth
    it's rumble, not RF

    see if it happens with the motor on but arm not down

    next, play a 0 dB track on a test record & see
     
    Old Rusty likes this.
  15. Jerry James

    Jerry James Rorum Fesident

    [​IMG] Hope you won't mind me piggybacking here. I just discovered today that I have this exact same issue. This is a new development that began when I swapped out my Peachtree Nova and Moon phono pre for a VPI 229D last week. The moment the needle hits the wax (does not happen when the motor is running by itself) the woofers go nuts (depending on volume adjustment). This did not happen with my former setup. I tried routing the table into that Moon pre and then into the 229D and the problem disappears. So, what should I do? I'm in over my head at this point with the tube gear (I know nothing about it - this is my first piece...). Nothing else in my system has changed; seems to be the phono amp in the 229D. Anything I could tinker with before subsonic filters (which, I also know nothing about...)? I'm using a VPI Classic 1 with an Ortofon 2M black, which sits on top of a 5 tier Solidsteel rack and the amp is on a butcher block on the solid concrete basement floor.
     
    Last edited: Dec 13, 2017
    Strat-Mangler likes this.
  16. missan

    missan Forum Resident

    Location:
    Stockholm
    Like I said, test the high pass and see how it goes.
     
  17. JohnO

    JohnO Senior Member

    Location:
    Washington, DC
    Switch to MONO. Does the visible subsonic speaker movement go away?
     
    Fishoutofwater likes this.
  18. Good plan; worth a try
     
  19. VinBob

    VinBob Forum Resident Thread Starter

    Location:
    New Jersey, USA
    Thanks - Will try both and I should have a 0dB track on one of my Test LPs - Will try this later tonight and report back.
     
  20. VinBob

    VinBob Forum Resident Thread Starter

    Location:
    New Jersey, USA
    This is an interesting thought - I actually tried this the other evening myself as my preamp has a mono switch, and I believe I did notice quite a reduction in the movement of the speaker drivers. So what does this technically mean with respect to the issue exactly? Thanks in advance...
     
  21. missan

    missan Forum Resident

    Location:
    Stockholm
    Technically it means that some of the amplitudes are out of phase. Which in turn most likely means that some of the movements are the arm moving vertically up and down.
     
  22. VinBob

    VinBob Forum Resident Thread Starter

    Location:
    New Jersey, USA
    Thanks mate and which presumably, would make sense if one has some level of warping in the LP correct? In my case, I have a dead flat LP and which is clamped down with my VPI Periphery ring, and yet I still get the speaker driver movement symptom... :confused:
     
  23. missan

    missan Forum Resident

    Location:
    Stockholm
    It´s a mistake to think one can get an Lp flat, it´s not so. This isn´t something that is easily visible, but the warps are nearly always there with some amplitudes.

    Not saying this is definitely the root cause, but we can´t see this movements of the cantilever and arm, they are mostly too small. But still the output from the cartridge at the resonance can be larger then the music. To some extent depending on the RIAA curve.
     
    Last edited: Dec 14, 2017
  24. VinBob

    VinBob Forum Resident Thread Starter

    Location:
    New Jersey, USA
    Thanks missan - I guess the stylus is picking up things that are clearly not visible to the naked eye...
     
    missan likes this.
  25. missan

    missan Forum Resident

    Location:
    Stockholm
    A good way would be if You could upload a wav-file from a suspect record
     
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