Speaker cabinet positoning: height, blocks, foam, etc...

[Russell L]

When using a single cab I've come to like mine tilted back. I do it with different things since I haven't ever bought a wedge specifically for the task, the latest thing being a dogfood bowl that happened to be in back of the truck one night (yes, it was clean, lol). I've also used a piece of 4x4 and even my gig bag with extra cords inside. Guess I need to get me something just for it, huh?

[Got2SadowskyNYC]

Actually, casters do prevent coupleing. How do I know? It's not difficult to feel coupleing. It is GREATLY reduced from setting the cab directly on the floor. I go from 416.25 square inches of surface contact to less than 3 inchs, spred out over 4 wheels, of contact surface.

I NEVER claimed it was 100% couple free, but you don't need it to be. You just want it to prevent the amp from being boomy and this is more than enough.

[Philonius]

I recently built this and posted a thread on it.



Phil Jones Briefcase Stand Someone asked me if the cab still had any bass response. My response, other than shocked indignation, was that I didn't think this arrangement would have any negative effect. I certainly noticed none. Any of you acoustic wizards have an informed opinion to share?

[JimmyM]

Originally Posted by Got2SadowskyNYC

Actually, casters do prevent coupleing. How do I know? It's not difficult to feel coupleing. It is GREATLY reduced from setting the cab directly on the floor. I go from 416.25 square inches of surface contact to less than 3 inchs, spred out over 4 wheels, of contact surface.

I NEVER claimed it was 100% couple free, but you don't need it to be. You just want it to prevent the amp from being boomy and this is more than enough.

Right, but it's not losing low end on casters...it's gaining mids and highs. It might only be 3-5 inches higher with casters, but it's still going to put mids and highs a little bit closer to your ears, and it's often enough to make a difference in how the cab sounds to you.

[JimmyM]

Originally Posted by Philonius

I recently built this and posted a thread on it.



Phil Jones Briefcase Stand Someone asked me if the cab still had any bass response. My response, other than shocked indignation, was that I didn't think this arrangement would have any negative effect. I certainly noticed none. Any of you acoustic wizards have an informed opinion to share?

Should not have any negative effect on bass response whatsoever, only a positive effect on mids and highs.

[Russell L]

By the way, just wanted to report that my Little Mark III head has been sitting atop my rat fur covered cabs when tilted back without sliding around at all (but I do let the legs come against the handle plate, too, which helps). Sometimes, when there's enough room in front without standing too close, I will let the front legs of the head overhang the top edge of the cab, just for a little added security. That way I can tilt the cab back even a little more. Just gotta make sure I don't pull it off there with my cord, but that's always a concern anyway, and the reason I run my cord through the cab handle.

[Downunderwonder]

Originally Posted by Got2SadowskyNYC

Actually, casters do prevent coupleing. How do I know? It's not difficult to feel coupleing. It is GREATLY reduced from setting the cab directly on the floor. I go from 416.25 square inches of surface contact to less than 3 inchs, spred out over 4 wheels, of contact surface.

I NEVER claimed it was 100% couple free, but you don't need it to be. You just want it to prevent the amp from being boomy and this is more than enough.

When we're talking about coupling it's acoustic coupling. We are talking of sound sources combining additively. The bass from the speaker and ports and reflected bass from the floor and wall behind. If the cab is raised about 2-1/2 ft the coupling from the floor is lost.

Same reason you back your cab against a wall rather than put it out from the wall, aside from saving space!

[Got2SadowskyNYC]

I'm 6'5" (with my boots on add an inch) so it's not much closer to my ears. We're talking 4inches MAX. I'm not hearing highs and mids better.

The question was who leaves it on wheels, sets it on the floor etc. So the question is acoustic coupling.

You don't loose bass response from the cab, BUT you do loose bass response from the stage. Especially if the stage is hollow or scaffolding. Another case is if it's on a riser of some kind, but it a lesser degree. The stage or riser becomes a sympathetic subwoofer, i.e. boomy.

If the platform is concrete then it's a nonissue.

In the rare instances where I have a wall to deal with, I set it off several inches if possible. I also set it off axis from the back wall.

[Got2SadowskyNYC]

The briefcase amp stand is great.

[sanderic]

Back in high school, 1970s, we put our amps on top of empty beer kegs. May not have sounded great, but it sure looked cool.

[will33]

As explained by BFM, and makes sense to me when you think about it.


The "coupling" is acoustic, not mechanical. If your cab vibrated so much it physically shook the whole floor, that would be one $#!++/ cab. Ehat happens is, the acoustic output from your speaker excites the reaonantce of the flimsy floor causing it to vibrate. Your rig then in turn vibrates because it's sitting on a floor that's vibrating...not the other way around..

Yes, it seems as if you lose some lows lifting thimgs off the floor. This is not true. You can measure and record the same amount of lows becaise they are still there. You can hear them still there if you move further away from the rig out into the room. What you are hearing is more mids and highs, not less lows, though it may still "seem like" less lows by comparison.

That all applies until you reach a distance approaching a couple feet off the floor. That's enough to cause a real boundry cancellation down in the "meaty" frequencies of the bass to lose real lows.

[Russell L]

When stacking cabs vertically does your top cab lose some lows, being as it is a couple of feet off the floor?

[dspellman]

Two kinds of coupling -- acoustic and mechanical.

Mechanical happens when the vibrations from the cabinet actually vibrate the stage floor and create a whole new "speaker." Hollow stages can really boom.

Acoustic coupling happens when the sound bounces off floor/nearby walls and adds 3-6 dB in the bass range. Raising the cabinet lowers the wavelength at which coupling is taking place. Rather than you getting the gain below about 250Hz you might only get it below 100Hz. (thank you barefacedbass.com)

[Wally Malone]

I use two crates when using just one of my Accugroove Tri-112s and do cover them as well. I've found that will always hear what I want and not have other band members, especially singers complaining that I'm too loud. And I use the Gramma pad between my cab and amp to suppress vibration to the amp.

Wally

[JimmyM]

Wow Wally, and you're an AFM representative. You of all people should know better than to use milk crates!!!

[5 Wire]

When acoustic I use a stand for the combo. Electric is either 212 on rubber feet or, for big gigs full stack on a riser. I sometimes wonder about porting the riser and spiking the bottom of the stack.

[Wally Malone]

Originally Posted by JimmyM

Wow Wally, and you're an AFM representative. You of all people should know better than to use milk crates!!!

Jimmy, I do use a nice looking black cover over them and they're good for carrying a lot of cables, etc. as well. I actually like the gigs I do where I need both cabs and then raising the cab is not an issue.

and Jimmy, I know you were pulling my leg.

Wally

[JimmyM]

OK, if it's a nice looking cover and not a tablecloth, I won't call the union on you

[Russell L]

Originally Posted by Russell L

When stacking cabs vertically does your top cab lose some lows, being as it is a couple of feet off the floor?

Thought I'd ask again what goes on with the top cab in a stack inasfar as losing lows goes, due to the height off the floor?

[JimmyM]

The bottom cab is still working, isn't it?