How important is floor coupling?

Discussion in 'Amps and Cabs [BG]' started by BigEarl, Sep 1, 2017.


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  1. BigEarl

    BigEarl

    Sep 29, 2003
    Elgin, TX
    And by that I mean cab to floor (you and your dirty minds!)

    Is it important?
    Should it always done regardless of stage or venue?
    Is it needless?
    So many questions, hoping for so many opinions!
     
    HaphAsSard and Sanchan like this.
  2. lz4005

    lz4005

    Oct 22, 2013
    It is important to avoid it because it usually makes you sound like mush.
     
    TomB, Jeff Scott, Charlzm and 9 others like this.
  3. charlie monroe

    charlie monroe Gold Supporting Member

    Feb 14, 2011
    Buffalo, NY
    Good sound is dependent on consistency. Every stage is different.

    Why would you want to build a variable into your sound?
     
  4. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Regarding coupling, there is acoustic coupling (which is called a boundary condition) and can not be avoided no matter what you might wish, and mechanical coupling which is cabinet vibration coupled through the feet and/or surface of the cabinet. This is usually what you want to avoid.
     
    kevk, TomB, MDBass and 6 others like this.
  5. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    It's important enough that a Auralex Gramma pad makes a difference, at least for me!
     
    cazclocker, TomB, ExaltBass and 8 others like this.
  6. lz4005

    lz4005

    Oct 22, 2013
    Acoustic coupling isn't impacted by lifting a speaker cabinet off the stage on a stand?
     
  7. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Not much, there will be some small amount of nulling added, with the characteristics depending on the distance to the boundary and distance away from the source.
     
    ExaltBass, petrus61, s0707 and 2 others like this.
  8. bucephylus

    bucephylus Supporting Member

    Aug 18, 2002
    Probably is affected to the extent that the different position creates a different field boundary with the floor; but, the physical basis for the interaction still exists; you just change it a little bit. And, with bass frequencies, it would be a very little bit.

    Mechanical coupling with a stand would depend on the vibration characteristics of the stand.

    I tend to view the acoustic coupling as something I work with at a given venue. The mechanical coupling has solutions, and I can directly control it.
     
  9. BigEarl

    BigEarl

    Sep 29, 2003
    Elgin, TX
    The reason why I asked is that for years I've been told that floor coupling is essential to a bass cab for assisting in the lower regions (under 100k) though I have never totally bought into it.

    Hey, at 6'4", any distance I can get that sucker closer to my head is a win!
     
    ExaltBass and slamsinger like this.
  10. +1. Don't leave home without mine.
     
    ExaltBass likes this.
  11. Rick James

    Rick James Inactive

    Feb 24, 2007
    New Jersey
    You get full boundary reinforcement from the floor, and the wall in back of the cab too, when the distance to it is less than 1/4 wavelength. 1/4 wavelength at 100 Hz is 33 inches, at 50 Hz it's 66 inches, so you don't need to have the cab on the floor. If you have a boomy stage you can get rid of a lot of boom by lifting the cab 36 inches or more, because boom tends to come from the 80-150 Hz range. You loose the boom with no effect on the lows.
     
  12. Kael

    Kael

    Dec 26, 2004
    Oklahoma City
    Owned a gramma pad, sold a gramma pad. Room acoustics (which are fairly uncontrollable) usually play a FAR greater role in boomy mushy bass tone than most stages. Unless perhaps the stage is constructed of old cereal boxes or some such hollow mess. If you are that concerned with coupling, by all means grab a gramma pad. I just find it to be an unnecessary thing to haul.

    Now for studio monitors coupling is a much larger concern. Isolate those puppies.
     
    superheavyfunk and tzohn like this.
  13. Plutonium244

    Plutonium244 Supporting Member

    Mar 29, 2015
    Wisconsin
    I find the gramma pad useful in many situations; there are enough wooden stages around. I wish it were common practice to put them under monitors at venues in addition to your IMO on-the-mark comment re: studios.

    The coupling effect can occasionally be useful... say, you want to use a 10" cab instead of something bigger in a relatively quiet situation, where you still want an impression of rich bass. Always a possibility of adverse interaction with other sources on stage though, with that vibration going through the floor.
     
  14. seamonkey

    seamonkey

    Aug 6, 2004
    Gramma pads and things like it usually elevate or tilt the speaker also to point better at your ears.
    There is not a whole lot of evidence, or measurements that they help anything with a well built cabinet.
    I have not seen anything, even a youtube showing one of these making a difference.

    It seems to be that overall all cabinets are built better these days and don't have a lot of mechanical coupling.
    YMMV, and plenty of even boutique cabinets may be suspect but overall it seems to be better these days.

    Also, acoustic coupling is at "sound" frequencies. Sound goes around obstacles shorter than it's wavelength. Think of thunder in the distance, you only hear low frequencies, when it's close you hear higher frequencies also. Any foam or pad is not going to block the sound close to the source of the low freq sound. The sound is just going to travel around it.
    The bass sound from the cab is just going to get to the floor outside of the pad.

    difr.gif

    difr2.gif

    A lot is confused with boundary effects and room modes
    Speaker Placement 101: Is Speaker-Boundary Interference Killing Your Bass?
    Boundary Cancellation and Room Modes
    These are good places to start over finding some magic foam to place under the cab.

    I can't believe cab manufacturers wouldn't be singing the praise or licensing these pads if they actually did anything special for their cabinets.
     
  15. Rip Van Dan

    Rip Van Dan DNA Endorsing Artist Supporting Member

    Feb 2, 2009
    Duvall, WA
    Normally I try to avoid it unless the venue is sucking up the low end. Putting your cab on the floor will give a 3db boost to the low end if you need it. Putting it up against a wall will give it another 3db boost and putting it in a corner will add another 3db to it. So that's as much as 9db of boost to the low end. That usually sounds like a whole lot of rumbling mud (not a good sound).

    If your stage bounces (as opposed to a "solid" feel on stage), avoid putting your cab on the floor at all costs. It will turn your sound into mud.
     
    physics likes this.
  16. It can vary from not important at all to very important.
    Sometimes you may want all the bottom you can get.
    Other times you may find yourself on a hollow,
    boomy stage where you just want to avoid everything
    being buried under an overwelming. muddy low rumble.
     
    bassomane likes this.
  17. Rick James

    Rick James Inactive

    Feb 24, 2007
    New Jersey
    It's +6dB per boundary, but only compared to outdoors, where there are no boundaries.
    Speaker spatial loading - sound radiation - Audio Judgement
    Indoors all of the boundaries factor in to the result, as well as the distance to them, so there's no simple calculation.
    I've only found two examples of isolation devices actually being measured for effect, and both debunk their worth.
    Testing Loudspeaker Isolation Products
    Do I need to isolate my subs? Do I need speaker spikes? - BillFitzmaurice.info
     
    seamonkey and tzohn like this.
  18. seamonkey

    seamonkey

    Aug 6, 2004
    +1 Bookmarked!
     
  19. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    In practice. putting your cabinet on the floor or a foot above the floor isn't going to change the "boundary gain" (which in practice will be between 3 and 6dB depending on losses within the boundary.) All it will do is add a small, shallow dip at the frequency (range) that corresponds to ~1/4 wavelength (the "round trip" path of the distance corresponds to 2 x 1/4-wavelength... or, are you ready for it... 180 degrees, which is where the cancellation comes from.

    Every time you add a (real) boundary and decrease the section angle of radiation by 1/2, you will gain 6dB of theoretical sensitivity (because of the inverse square law's "squared factor).

    If the stage is mechanically resonant, and vibrations into the stage through mechanical contact are bothersome, decoupling with a thin piece of foam, blanket, etc. can in fact help, but it really does depend on the primary transmission cause. It's not going to hurt anything, it might help and no kittens or carrots will die from experimentation.
     
    Rip Van Dan, MR PC, DavC and 3 others like this.
  20. Is there something different that Gamma pad does that the regular old interlocking foam pad you can buy at Lowe's or Home Depot can't do?
     
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