Lifting the cab off the floor?

[f.c.geil]

Floor coupling and the effects therefrom are greatly exaggerated. The vast majority of the sonic difference is that the high frequencies are now closer to your ear, so you hear them better. The additional highs make it SEEM like there is less bottom end (just like turning down the tone knob seems to add bass). There isn't, but the loss of highs has the same psychological effect. Psychological, NOT physical.

 

[Sid Fang]

This has been covered in several previous threads, but this is the first time I've seen actual "coupling deniers" claiming that the effects of losing acoustic coupling with the floor are "exaggerated" or "psychological". As I've recounted many times, I often prop my 112 practice combo on a 10" stool with no problems and some benefit in dispersion, but when I happened to set the same amp on a 31" cabinet, in a practice space I knew quite well, the loss of bass response through the whole room was immediate and terrifying. I really thought that the combo had failed.

There are some good explanations of the phenomenon out there, with math, diagrams, etc. The physics is real and will bite you if you ignore it.

 

[will33]

In general, at close range an elevated cab sounds brighter because you're getting more highs, not less lows.

This ^^

The lows stay intact out in the audience, just appear less up close due to being able to hear highs better.

Lift it a couple feet or more and then you get long enough boundary distances to cause cancellation that will indeed lose fullnes in the sound.

Of course, this is all subject to other walls/boundary distances, solid or flimsy stage, other sound sources on stage, etc.

 

[will33]

A rule of thumb for subwoofers is to place them less than 2 ft. or more than 8 ft. from boundaries to help avoid nulls down in the 40-120hz passband they play. Can use distances in between there to intentionally cause a cancellation if you're having bad boom/mud problems with a bass rig.

 

[mambo4]

I hate having my cabs on the floor. I like them as high as I can get them Right at my head if possible. I don't care what my cabs sound like to the audience. That's what the PA is for. I want to hear myself as clear and directly as possible

This is what it's all about. Get your amp by your ears and hear yourself. My experience shows that this resolves more problems than it creates.
Acoustic coupling concerns seem generally overblown in most cases, and "more bass" is not automatically a good thing.
Know that there is a big, big difference between "bass frequencies" and "frequencies that are important to a good bass tone".

 

[will33]

This has been covered in several previous threads, but this is the first time I've seen actual "coupling deniers" claiming that the effects of losing acoustic coupling with the floor are "exaggerated" or "psychological". As I've recounted many times, I often prop my 112 practice combo on a 10" stool with no problems and some benefit in dispersion, but when I happened to set the same amp on a 31" cabinet, in a practice space I knew quite well, the loss of bass response through the whole room was immediate and terrifying. I really thought that the combo had failed.

There are some good explanations of the phenomenon out there, with math, diagrams, etc. The physics is real and will bite you if you ignore it.

If the bottom cab isn't plugged in, in addition to the distance cancellation, its cone will move some in sympathy with the output of the working cab, adding to the problem, as well as the non-working cab itself acting as a bit of a bass trap.

Sort of a trifecta of losing lowend there.

Sticking a shorted plug in the bottom cab can help some with the sympathetic cone movement, but it's still acting as a sort of "spongy" baffle and the box is still somewhat of a bass trap.

 

[T-Bird]

Hi.

This has been covered in several previous threads, but this is the first time I've seen actual "coupling deniers" claiming that the effects of losing acoustic coupling with the floor are "exaggerated" or "psychological".

I must be on Your ignore list then .

I would probably use the word "misunderstood" rather than "exaggerated" or "psychological" though, but IMO the latter two do apply as well in some cases.

As I've recounted many times, I often prop my 112 practice combo on a 10" stool with no problems and some benefit in dispersion, but when I happened to set the same amp on a 31" cabinet, in a practice space I knew quite well, the loss of bass response through the whole room was immediate and terrifying.

Was that cab plugged in?
Any unused cab becomes a quite effective bass trap, especially if it's a Helmholz resonator.
EDIT: Will33 beat me to it .

There are some good explanations of the phenomenon out there, with math, diagrams, etc. The physics is real and will bite you if you ignore it.

None of that information supports the benefits of floor coupling on MI bass frequencies.
None that I've seen at least.

With speed of sound = 345 m/s and EDIT:A4 not C4 = 440 Hz, the 1/4 wavelenght of E1 (41.20 Hz) is 209.33cm/~6'10.
Most bass cabs do not go that low with any authority anyway, so the effect is even less pronounced.

Regards
Sam

 

[Bassamatic]

Pretty sure you will start to hear a loss in low end once you are more than a few inches off the floor. Tilting is OK, raising causes you to lose the coupling with the floor so the bass has yet another direction to go around the cab. Using a pad stops your cab from physically vibrating the stage without losing coupling. Just experiment.

Just FYI - If you want to see what MAXIMUM coupling can do, back your cab into a corner, on the floor. You should gain more than 6 dB (4x) in acoustic level just by doing that - using the room walls as a giant horn.

 

[Gaolee]

Sometimes floor coupling can cause problems, particularly on hollow stage IME. I use a Gramma pad and it is perfect in isolating my cab from the floor

Yep. I have had this happen. I have used everthing from a scrap of carpet to a couple boards to gym flooring tiles to solve the problem.

 

[jeffbrown]

I used to use a pad for just my combo, but still couldn't hear it well enough, so I got a tilt-back stand which puts it at about a 45 degree angle, still only a couple inches off the floor. That helped measurably. I tried putting the pad under the stand, and found that the sound seemed cleaner (??). (The stand has 4 small plastic pads contacting the floor.)

When I use the 6x10 plus head, I have no problems hearing myself ;-). Haven't tried the pad under it, so that'll be the next experiment.

I have an extension cab for the combo, and I've tried the following: 1) no pad, straight stack. I hear me well, booming hasn't been a problem. 2) Pad under ext. cab. No difference. 3) Pad under combo on top of ext. cab. Seems like some lows go away, which indicates loss of coupling, I assume. 4) Tilt-back under combo on ext. cab. I hear me *quite* well, but I suspect some sound is lost out front. Haven't tried pads under both. That seems like overkill/too much damping, but I could be wrong.... I don't usually need to set up near walls or in corners.

SO, in my estimation, pads and stands work, but ya gotta tailor it to each situation.

YMMV/HTH

 

[jeffbrown]

And yeah, this has been the topic of many threads before. There's science, and your ears. Do the right thing.

 

[Fuzzbass]

Gotta show the love for the "vertical 2x10 stack". This is a way of elevating your rig -- that is, bringing speakers closer to ear level -- without actually lifting it from the floor. This configuration absolutely blows away an equivalent 4x10.

 

[Nephilymbass]

I elevate my 410. I used an 810 for years and got used to having speakers closer to my head.

Stacking 2 cabs works nice but that means more heavy gear to lug around.

The whole loss of low end thing can be more than compensated for by running an xlr signal that has plenty of low end to a pa that has decent subs. A lot of people hate using xlrs because they say they sound thin but the reality is no cab and no mic has the lower frequency range of an xlr signal. The reason an xlr can sound thin is because those folks can hear floor coupling and or are using low tuned cabs and they compensate with eq (dial out lows) to get a tighter sound onstage, but it actually results in a thinner xlr signal than using a sealed cab elevated off the floor.

 

[Michael J]

With ... C4 = 440 Hz,

Also known as A.

 

[Nephilymbass]

As far as how i elevate my cab. No, i don't use speaker stand or milk crates. I stack my 410 on an empty 8 space road case style rack which happens to be about the same height as a 15 cab. I also remove the rear wheels off the 410 to give it some tilt and keep it from rolling. My actually rack gear (pre amp, power amp, rack tuner) i carry in a 4 space gator rack bag now. I use to use much bigger racks including the 8 which i use as a cab stand and a 14 which is now our pa rack at the rehearsal space. But a lot of the stuff that was in my big racks has been replaced with stuff on my pedalboard. Even my wireless is a pedal style.

 

[T-Bird]

Hi.

Also known as A.

Talk about making a stupid mistake .

Thanks for pointing that out.

Regards
Sam

 

[Sid Fang]

If the bottom cab isn't plugged in, in addition to the distance cancellation, its cone will move some in sympathy with the output of the working cab, adding to the problem, as well as the non-working cab itself acting as a bit of a bass trap.

Sort of a trifecta of losing lowend there.

Sticking a shorted plug in the bottom cab can help some with the sympathetic cone movement, but it's still acting as a sort of "spongy" baffle and the box is still somewhat of a bass trap.

I'm aware of this effect, but in the accidental experiment in question, the total bass suck went away when I put the combo on the floor *beside* the unplugged cab. The bass trap action should still have been in play.

Pretty sure you will start to hear a loss in low end once you are more than a few inches off the floor. Tilting is OK, raising causes you to lose the coupling with the floor so the bass has yet another direction to go around the cab. Using a pad stops your cab from physically vibrating the stage without losing coupling. Just experiment.

There was a great page on one of the speaker manufacturers sites that showed graphically how the effect works, and why it doesn't start cutting in until one gets into the range of 2 feet off the floor. The classic plastic milk crates used in bars and clubs since the 1970s just happen to be shorter than that.

Tilting a cab that's close to the floor is indeed a much better idea than raising it to ear level, if you want to hear it directly, though of course tilting presents its own problems with stability.

Note, by the way, that the pad thing is about *mechanical* coupling with the floor/stage, which is almost never a good thing, as opposed to acoustic coupling, which can be a blessing or a curse, depending on what you're expecting.

Just FYI - If you want to see what MAXIMUM coupling can do, back your cab into a corner, on the floor. You should gain more than 6 dB (4x) in acoustic level just by doing that - using the room walls as a giant horn.

Very true, and it's saved my ass once or twice when all I could bring to a club gig was my 150W combo. I insisted on having the corner for it, for precisely this reason, and kept up with 2 guitarists, vocal PA, and unmiced drums, without it even getting warm.

 

[will33]

When you put the combo beside the other cab you got your coupling back and the baffle with the working speaker in it reached all the way down to the floor again.