Stacked Cabs Coupling (?) Troubles?

[SurferJoe46]

Running my combo/cab with 2-12 and horn on top of my 115, I find that I needed a thick towel to take a bad noise out of them.

Are they coupling to each other and the towel just muted that or is there another dynamic here of which I am not aware?

The top cab has it's original and very supple thick rubber cookie-feet, and I take the casters off when I stack it on top of the 115.

The 115 is on casters and it's not apparently the problem - I think.

That towel trick worked - is there a better way to isolate them from each other in a stack formation: a special pad or insulator? The towel looks kind frumpy.

Maybe I can get the cat-lady across the road to make me some really thick doilies.

[MR PC]

Google "Auralex".

["Q"]

I'll just throw this out here for a goof but, the Hi-Fi stereo crowd would say that the bottom cab is not coupled to the ground ENOUGH. Though I'm assuming those brass spikes they use would probably detract from the cabs "roadability" factor (ouch).

But if it too has rubber feet you might try switching to something more dense.

[SurferJoe46]

Originally Posted by MR PC

Google "Auralex".

Originally Posted by "Q"

But if it too has rubber feet you might try switching to something more dense.

Going there - thanks.

[fretno]

I personally would remove the casters . I am also a big fan of Auralex Gramma boards , though I don't think it would work between the cabs . I recommend a dense mat like used in some places of work where people stand for long periods of time . I use it under my amp .

[SurferJoe46]

Originally Posted by fretno

I personally would remove the casters . I am also a big fan of Auralex Gramma boards , though I don't think it would work between the cabs . I recommend a dense mat like used in some places of work where people stand for long periods of time . I use it under my amp .

I just got off the phone with the Aurelex Company and they don't recommend their pad for my application, but said it would work good for floor-to-cab coupling troubles. He also recommended to use some rebond carpet padding or lacking that to use a work mat.

The "Gramma" has the top covering, a hard flat board-like device and some 'pontoons' that keep the main thing slightly above the floor.

[agreatheight]

I have been using a towel or a moving blanket between stacked cabs for 15 years. I'll agree that the aesthetics may not be perfect, but it works very well... and I am not one to spend money if there is no pressing reason.

[SurferJoe46]

Originally Posted by agreatheight

I have been using a towel or a moving blanket between stacked cabs for 15 years. I'll agree that the aesthetics may not be perfect, but it works very well... and I am not one to spend money if there is no pressing reason.

< sigh > You're right.

It's kinda funny that the towel between them took out all the nasty sounds. I thought the amp was loose or that a baffle or brace had broken loose - it was THAT loud.

The next part that's funny is that only my AEB brought this sound out! I use a hole plug and it wasn't harmonics - just the tone and resonance from it I think.

I knew it wasn't a loose speaker, in case you saw my post a while back about the electrical lugs being flaky and the loose screws on the speakers - I'd already been there/done that.

[agreatheight]

Maybe if you got a black towel it would be less noticeable?

["Q"]

Originally Posted by agreatheight

Maybe if you got a black towel it would be less noticeable?

Simple genius is always the best kind.

[SurferJoe46]

Originally Posted by agreatheight

Maybe if you got a black towel it would be less noticeable?

Originally Posted by "Q"

Simple genius is always the best kind.

Undeniably!

I guess the pink one was a little too, er - ya know?

[muddycreek]

Horse mats. Black, 1/2-3/4" thick fairly heavy rubber. Acoustician-on-the-cheap's dream for floating wood frame floors.

Sometimes larger stables/tack stores cut them for themselves or for other people, might have a little 2' squareish remnant lying around for free or very cheap. Cut 'em to your exact size with a circular saw. Worth some phone calls if you've got horses within half an hour or so.

[SurferJoe46]

Great ideas, all.

I wonder what the dynamics of this problem are all about?

I have noticed problems with footprints on floors, but between the stacks? Isn't that a little odd?

Beginning to believe that this science of sound wave propagation isn't really a science at all.

[Bob C]

Most people seem to enjoy a positive coupling effect from stacking cabinets. Can you describe the bad sound you are experiencing? Is it a rattle from vibrations? Is the bottom cabinet way more efficient than the top one?

[craig.p]

Horse mats are really called "stall mats." You can get them at most any feed/grain store like Blue Seal or Agway. Tack shops usually have them, too. Another way to cut a stall mat is to bend it over a 4x4 or a 2x4 so there's a good tight bend in it. Now take a utility knife and cut along the line you've already drawn on the mat, right over the top of the 4x4 or 2x4 along its length (over the center of the mat's curl). Do NOT try to cut all the way through to the other side of the mat -- just most of the way through. Then go back and make a second pass all the way through. Use a fresh blade.

[uglyrumor]

I, too, have cushioned my speakers and head for years. It just made sense that the vibration was not good for sensitive electrical components. The vibration coupled with heat is a recipe for failure. That being said, I have been known to be pretty anal about my equipment, and my 1973 bassman amplifier looked brand new when I sold it a year or so ago. Same with cabinets. Seperate them with a good soft rubber pad.

That being said, there are thousands of amps and cabinets without those precautions taken that have lasted years. But your problem is vibration.

[SurferJoe46]

Originally Posted by Bob C

Most people seem to enjoy a positive coupling effect from stacking cabinets. Can you describe the bad sound you are experiencing? Is it a rattle from vibrations? Is the bottom cabinet way more efficient than the top one?

Interesting questions - let me think.

It was like a heavy flutter, kinda like a hand being slapped on the cab somewhere.

When I stuck my fist between the two cabs as far as I could and it quit. I could not feel any actual motion, not like a cab wall was flapping or broken/cracked. It was just that they seemed to be talking to each other and generating a feedback.

I pulled both grills off and it wasn't the drivers at all. The tubes on the back of the 210 combo are pumping air like crazy I felt.

Next I took them apart and back onto the dual wheel casters I got - figuring I was getting those non-musical instrument wheels chattering. Nope.

So I took the casters back out of the combo 210 cab and then stuck a towel on top of the 115, put it all together again with the original rubber biscuit feet still on the (top) combo and the same casters on the lower 115.

Noise gone.

["Q"]

Maybe filling the gap is whats important. Could the space between the cabs be a resonant cavity?

[billfitzmaurice]

Originally Posted by SurferJoe46

Are they coupling to each other and the towel just muted that or is there another dynamic here of which I am not aware? .

Mutual coupling is accomplished by having them close to each other, there is nothing mechanical about it at all. If placing one above the other causes rattling noises you just have to identify what's rattling and fix it by whatever means works.

[SurferJoe46]

Goody. The towel it is then and maybe getting a black one will help until I find some of the rubber fatigue mat. .