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Rig Problem? High Harmonic Content in Upper Mids

Discussion in 'Amps and Cabs [BG]' started by BuffaloBob4343, Feb 22, 2006.

  1. BuffaloBob4343

    BuffaloBob4343 Supporting Member

    Jul 3, 2005
    Buffalo, NY
    I seem to be experiencing a problem when playing my rig at higher volumes. I am playing through either an Aggie or TrueVoice peamp into a QSC 850 (in bridged mono mode) and into a Schro 1210. I have checked the rig many times to be sure things are set up properly.

    The problem occurs when I sustain certain notes, like D on the G string or A on the D string. The fundamental seems to die out very quickly and what's left is a very annoying harmonic.

    I'm not sure if this is a rig problem or a guitar/string problem, or even an input gain level problem. It seems to occur indepedent of which preamp I use (Aggie DB659 or TrueVoice). It seems to occur the least on my Modulus Fretless Jazz (TI Rounds) and seems to be the worst on my Warwick (Infeld Super Alloys).

    Anyone else experience this? Could this be that the Pups on certain of my axes are hot and thus should either be lowered or the strings raised?

    I don't want to start f'ing with my guitar set-ups until I am am sure it is not something else.

    But it is ANNOYING THE HELL OUT OF ME!!:eyebrow:
  2. KJung

    KJung Supporting Member

    Unfortunately, that sounds like a classic dead spot(s) on your bass neck. Not much you can do about it if that's what it is. Some have luck with one of those weights that you attach to the headstock to change the 'frequency' of the neck.

    Edit: I couldn't quite tell if this was happening on all your basses... you say it happens 'the least' on the Modulus... which should have no deadspots at all.
  3. BuffaloBob4343

    BuffaloBob4343 Supporting Member

    Jul 3, 2005
    Buffalo, NY
    The only thing is that it doesn't seem to happen ay lower volumes. Also, I thought a dead spot lead to a preciptous drop infundamental with no remaining sound.

    In what I have experienced, it seems to be volume dependent and doesn't drop off immediately. Also, rolling of the mids seems to help as well.

    Maybe I just don't know what a deadspot really is! If this is a deadspot, how common is this in top o' the line basses?
  4. BuffaloBob4343

    BuffaloBob4343 Supporting Member

    Jul 3, 2005
    Buffalo, NY
    And you're right, it doesn't really happen on the Modulus at all, although it is a Genesis and does have tone woods surrounding the carbon fiber spine.

    And I am not experiencing a really fast decay of the fundamental, but I have noticed this at higher volumes on my Warwick. And it sounds fine as long as I don't try to sustain the note a really long time.
  5. KJung

    KJung Supporting Member

    What you describe is what I hear in a deadspot.... a quick reduction in fundamental volume with an upper harmonic remaining. Also, unfortunately, I've never seen a correlation between the price of an instrument and deadspots.... it's just the nature of wooden basses.

    Also, deadspots can seem better or worse depending on EQ and the room, since a deadspot is 'frequency dependent'. Different room acoustics can help or make it worse.

    However... other TBer's will chime in.... maybe it's something in your gear or something else entirely, but it sure does seem to be a deadspot.

    Edit: One way to check is that if you play long sustaining notes when the bass isn't plugged in, you should still be able to hear that fundamental drop out if it's a true deadspot. Unplug your bass and find a very quiet spot.... play the notes above and below and on the problem note and listen for a difference. You should be able to hear that fundamental die out if that's the problem.
  6. pickles

    pickles Gold Supporting Member

    Mar 23, 2000
    Ventura, CA
    Sounds like a dead spot all right. Try playing the same note at the 10th fret on the D string, and I bet it'll sustain real nice for ya. That all but eliminates the possibility of anything being wrong with the rig, since its the same fundamental note (granted, with different tone).
  7. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    You'll probably find it depends on the note/fret, if it's one where you can hit a ringing harmonic, like the fifth and seventh frets, then then phenomena is caused by the string, not the bass. The density of the body makes a big difference in the length of sustain too. Lightweight woods like Basswood and Poplar absorb vibrations like a sponge and don't ring on, denser woods like Ash don't absorb vibration as much and ring longer. You can hit as note on my carved Rosewood bass, put it in the case, come back a week later and take it out and it's still sustaining.
  8. KJung

    KJung Supporting Member

    Dead spots are a different animal than general sustain issues. I've never noticed any correlation between the density of wood and dead spots. You are correct that more dense woods tend to sustain longer. However, even though it's counterintuitive, more dense woods can actually increase the impact of a dead spot, since the notes around it can actually ring a very long time, making the drop in fundamental volume that much more noticable.

    It's a very frustrating thing and there's very little that can be done about it.
  9. BuffaloBob4343

    BuffaloBob4343 Supporting Member

    Jul 3, 2005
    Buffalo, NY
    Hey Everyone,

    Thanks to all for the responses. I guess I have finally acquired a nice enough rig that I am starting to notice more of these tertiary issues than I did before.

    After KJung's first post, I did some searching on deadspots on this forum and learned quite a bit. I guess I never knew how common they are in wood necks, and especially at the locations where I have noticed mine.

    Actually, none of them are all THAT bad. They do drop off faster than others, but unless I do a long sustain, the note sounds absolutely fine. I guess if you need to sustain those nodes, you do it elsewhere on the board. And unless it is totall interfering with ones typical playing styles. they are just part of the character of the bass.:bassist:

    I guess the other thing one can do is to EQ the partiuclar bass to minimize the effect.

    Thanks again!!
  10. KJung

    KJung Supporting Member

    It's amazing how you can learn to play around a dead spot. After a while it gets to be second nature... you should be fine.

    Good luck and rock on!
  11. BuffaloBob4343

    BuffaloBob4343 Supporting Member

    Jul 3, 2005
    Buffalo, NY
    In case anyone is intersted, here is an article that discusses the cause of dead spots, using a Fender Strat as a test case.


    Apparently, it is resonsant vibration in the neck that dampens the vibration of the string.
  12. Thor

    Thor Moderator Staff Member Gold Supporting Member

    That was going to be my next suggestion. Try a slight cut
    at the higher frequencies.

    Also, does the Schroeder have a horn or tweeter?
    ( I haven;t gotten arond to reading the megathread, as my wallet
    can't stand it right now.)

    If so, does it have a switch or Lpad of some kind. Can you reduce the
    impact of it slightly?

    I think you are looking for some nuance tweaks at this point.
  13. BuffaloBob4343

    BuffaloBob4343 Supporting Member

    Jul 3, 2005
    Buffalo, NY
    Yeah, your right, Some minor EQing and some tweaks here and there and everything is all good again. One thing I discovered is that the Schro 1210 sounds better with the QSC filter rolled off at 50Hz rather than 30Hz. It can reproduce the lower frequencies, but it really cleans the cab up a lot at higher volumes.

    I had my rig set up for my 21012, but I needed to tweak the rig here and there when going to the 1210. I also like my 1210 better without my Aphex Big Bottom/Aural Exciter also.
  14. Thor

    Thor Moderator Staff Member Gold Supporting Member

    I had found that to be the case with my Eden rig,
    the EQ settings make a big difference. I just wrote them
    down, start flat, this knob to here, that one to there,
    and check for the room boom from there.
  15. svtb15


    Mar 22, 2004
    Austin,TX - McKinney,TX - NY,NY, - Nashville,TN
    I play it all. Whatever works for the gig
    I would think that a dead spot would also happen if the bass is not plugged in. Acousticly is should happen with your ear next to the bass.. although using excessive amounts of EQ in the lower BASS area may actually make that dead spot more prominant and noticeable if that is what it is.. First,,,I would listen to the bass with your ear next to it, WITHOUT being plugged into your amp. If that note does not sound dead without the amp I would highly suspect that it is not the Bass.
    Look at your EQ settings, are you boosting Tons of BASS into the signal? or using Alot of MID CUT? Flatten out your EQ to see if that helps then go from there.
    I personally have almost never had a dead spot on multiple strings as you decribed.. Only a 1 note area on a Fender style bass in the normal spot.
    Also, one thing to check if you have multiple dead spots on multiple strings is to see if your Truss rod is rattling.. That happened to me with a MM stingray and it caused what you decribe when the truss rod rattled sympathetically with the resonant note.. Make sure it is not just floppy around in there.
  16. If you sustain the dead notes do the remaining harmonics turn into feedback? I notice on certain notes and EQ settings, at high volume the sound coming from the amp will vibrate the bass and cause a feedback type of sound. I figured it had something to do with running the gain high, and running the amp at 2ohms; which I've read reduces damping factor, which can be a factor in feedback. I'm no expert but it seems like a possibility.
  17. Thor

    Thor Moderator Staff Member Gold Supporting Member


    He said he eq'ed it out 3 posts ago.


    We're done I think.
  18. BuffaloBob4343

    BuffaloBob4343 Supporting Member

    Jul 3, 2005
    Buffalo, NY
    Actually, I did experience this last night with my OPEN "D" string and at "D" on my G on my P-Bass. I have a DarkStar Lakie and I tried adjusting the pole piece under each of the top two strings but this did not help.

    I think this is some sort of feedback phenomenon because if I walked away from the amp and faced away, I could find spots in the room where this did seem to go away.

    DS PUPS tend to be extra hot, so I am going to try and calm things down with some different strings. I never noticed this with my 21012 (which is in Buffalo and so not available for an A/B comparison right now). Of course, it may be I didn't try to sustain those notes very long and just didn't cause it while playing previously thorugh the 21012.
  19. Metal Mitch

    Metal Mitch

    Jul 14, 2003
    There you go. Not a dead spot, only happens on long sustained notes at higher volumes, is affected by EQ and/or location of the bass in relation to the speakers... definitely feedback. It's fun. Play with it, but be careful not to fry your speakers. ;)
  20. Fred Hammon

    Fred Hammon Dark Star pickups

    May 13, 2005
    What you've described sounds like the string still being too close to the pickup.
    Dark Stars have a very strong magnetic flux and they will stop the string from vibrating if they get too close to a pole piece and leave a rather "sickish" sounding harmonic ringing. Guitar players call this "Stratitis".
    Make sure the poles are adjusted well out of the way. When you fret a string it could get pulled down very close to the pickup. Go ahead and back them below the bobbin face a little if necessary.
    I usually recommend 3/16" mimumum clearance - unfretted. How much do you have when you're fretting those notes?

    The problem could be elsewhere but this needs to be addressed first.