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Auralex Gramma between Rack and cabs?

Discussion in 'Amps and Cabs [BG]' started by OldCityBass, Oct 30, 2005.

  1. I have a 6 space rack that I like to use with a couple of different cabs configurations. When I use this rack on top of 2 Aguilar GS112's, the rack produces a very audible vibration noise. I don't seem to really notice this with other cabs but that's probably because I'm generally playing at an overall lower volume with the GS112's - and that makes the vibration noise more noticeable.

    I know that taking the rack off the cabs will solve this problem, but I like the rack to be up high enough to make adjustments without getting down on the floor.

    Anyway, I'm thinking that trying a Auralex Gramma on top of the cabs / under the rack may solve this problem. Has anyone tried something like this?
  2. I used some vibration absorbing spheres under the rack when I got an expensive NOS tube in my preamp. Figured vibrations can't be helping the tube innards out any.

    I think it should work fine. If you've got something in the rack vibrating, isolate the rack from the source of vibrations. Makes sense to me.

    The only problem I can see is that the auralex is made to support a lot of weight. Therefore it is fairly stiff. If the rack isn't heavy enough to compress it a little, it may lose its vibration absorbing qualities. You may need something softer.

    Think how much smoother your car rides when its loaded with bass bear. Think how rough your car would ride with Hummer springs on it. Same principle.

  3. NJL


    Apr 12, 2002
    San Antonio
    I used a GRAMMA between my rack and cabs, it worked just fine.....also helps get the rack just a tad higher so you don't have to mess up your back tweaking...
  4. Folmeister

    Folmeister Knowledge is Good - Emile Faber Supporting Member

    May 7, 2003
    Tomball, Texas
    I always use a Gramma between my cab and head. They work very well in terms of isolation from vibration and adding a little height to the rig. The ONLY concern is that the top of the Gramma doesn't have much grip for the plastic/rubber feet on most racks.
  5. Cool, thanks guys. I'm going to give it try.
  6. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    Fremont, Ohio
    Editor-in-Chief, Bass Gear Magazine
    I also think that this is a good use of a Gramma pad, especially with tube heads.

  7. Big String

    Big String Supporting Member

    Apr 22, 2000
    Northwest Indiana
    Been using them for that purpose for some time.
    If your rack case is slippery stick some velcor in a couple spots on the bottom of your case. Use the bristle side not the soft.
  8. cheezewiz

    cheezewiz Supporting Member

    Mar 27, 2002
    I use a Gramma between my tube head and my cab. I got the idea from Mr Bowlus up there! ^
  9. Why not just save some cash and get a piece of conventional foam rubber, whatever color you like? The Gramma, for all its good points, costs what it does because of its design to acoustically decouple items (usually cabs from floor). That feature isn't really necessary to isolate your head from the cab. What are we talking here, $2 to $5 for a piece of foam from a UPS store (or wherever)?
  10. I'll ship you some of those foam packing peanuts for $10.00.

  11. +1 on Tube Head isolation with a Gramma.
    My V4BH is too wide for my Bag End cabs, the feet are wider than the cabs, and it only made sense that tubes would be happier if they were not directly coupled to the cabs.
    One under the stacked cabs and one on top under the head, makes a lot of people take a closer look when they see it and wonder what kind of weird cabinet system I have (o;}
  12. I've got two pieces of that super cheap fiberboard stuff, not the hard stuff, but the crap that you don't ever want to build anything out of. One goes under my 1x12 at the bottom of the stack, and one under my calzone rack with my mesa. Cost me 10 bucks I think, just had to saw it into the right shape. The stuff is really soft, and seems to decouple the rig from the floor as some of you describe those auralex pads as being able to do.
  13. I use two of the three inch Auralex bookcase pads. I place them at both cover/case hindge locations. They have a slight angle towards the front but the weight of the rack flattens out the pad so you cant tell there's and forward slope at all. The pack came with four pads and four thin wedges. I paid around $20.00 for the set. The pads fit perfectly in the six space lids when not in use. I have the PLX internal rattle problem and the pads stop the noise.
  14. 57pbass

    57pbass Supporting Member

    Slightly OT....I have been using my Auralex Gramma with my Scout Combo with great results....
  15. I've tried putting my Gramma on top of my cabs, and my amp on top of my Gramma before. Had to do it that way, Grampa had bladder control problems.

  16. A pair of Mopads from auralex....does this kind of job better - it's less stiff, and more intune with isolating something like a rack case (vice isolating a cab from the floor, for instance).

    Cost about 1/2 for a set of Mopads as well.
  17. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    Fremont, Ohio
    Editor-in-Chief, Bass Gear Magazine
    I use Mopads with my smaller heads when the cab I am using has a top handle. I hadn't though of using them for a heavier tube head, though I may give it a try. I am concerned, though, that with a heavy head, the foam on the Mopads would compress to the point of not being as useful. Still, it is pretty resilient stuff, though.

  18. Good suggestion on the MoPads from Auralex.
    I'm sitting with a pair on either side of my computer desk supporting my Event 20/20 monitors. Now that was a Doh! Moment.
    I shall give those a try one day, although, a V4BH does tip the scales at an even 40 lbs. it appears the MoPads might compress too much as Tom suggested. I wonder if that tiny Skjold preamp would benefit any?
  19. RevGroove

    RevGroove Commercial User

    Jul 21, 2002
    Burlington ON Canada
    Manager, Account Services: Long & McQuade Ltd. (Burlington); MTD Kingston Basses International Emerging Artist; Bartolini Electronics Emerging Artist
    I used one between head and cab...until I switched to a shockmount rack case...still use two GRAMMAS underneath my "big rig" though...