Amp isolation?
- Thread starter Amped
- Start date
Set the bass cab on several layers of carpet, not a total cure but it helps. Get the guitar amps up off the floor, spare dinning room chairs work well for this and it helps a lot. Also you might want to place the amps at a slight angle to the wall behind them. If you can look under the floor, see which way the floor joists (beams) run, make sure the bass travels across them, sound waves from bass will boom more if the sound travels parrallel to floor beams. I have wood floors too, covered with carpet. Wood floors add some nice natural reverb to a room but they are niosy so carpet or at least a few throw rugs are handy to have around.
Well, to spare a dining room chair, you could build your own amp riser. A few companies produce these, but you can make your own for a fraction of the cost. All you need is a few feet of 2x4, and some plywood. Study a few designs of the ones made by companies. Build it sturdy, especially if we're talking about a bass cab. Then, have fun with your fiberglass, carpet, rugs, and any other things you may have around the house.
EDIT: OOh, it is a cabinet. Yeah, make sure its strong so it won't snap or buckle too much under the weight.
EDIT: OOh, it is a cabinet. Yeah, make sure its strong so it won't snap or buckle too much under the weight.
Richard Monroe
Well-known member
Use an amp stand. And it's not just isolating the cab from the floor. The cab is like the body of an acoustic guitar. It needs to resonate. Putting it on a pile of carpet is like putting your acoustic up against a wet dog.-Richie
Amped
New member
So what about putting the cab on a piece of 703 cut to the footprint of the cabinet? What about hockey pucks? The floor is three layers of 3/4" OSB plywood covered with carpet. I just dont want the sound to resonate through the floor. I know Auralex mke a riser but im not sure what its made of, called the "GRAMMA", looks pretty simple. Thanks for the responses.
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Amped
New member
mixsit said:I've always figured the biggest factor of getting the cab up off the floor was just coupling from that one barrier reinforcement (is that the name for it?) and changing the reflection-frequencies. But I guess it's taming the floor vibrations to boot. Good point.
Wayne
Hey Wayne, whats up bud!? Im not quite sure Im understanding your post, care to elaborate?
RICK FITZPATRICK
New member
Hello Amped. That should work to an extent, maybe two layers of it. However, here is the REAL problem. Even though you may decouple the direct structural transmission from amp to floor, the fact remains you have a wood floor, which is a diaphram/ membrane. ALL objects have a resonant frequency, but suspended membranes are the worst. No amount of decoupling will help with this. There will be certain frequencies that will excite the floor regardless. If transmission to a neighbor below is occuring, de-coupling will not help at resonant frequencies. In fact, there is very little you can do to stop these. Especially lower frequencies. Even concrete floors between upper and lower spaces have a resonant frequency, although because of its mass, the frequency will be much lower. Structural transmission of low frequency via resonance will transmitt throughout a building via connections too. You could dampen this resonace via heavy carpeting, but you can't stop it. Here is the plus side though. If the floor cavities are sealed, you have a certain amount of built in bass absorption within YOUR room!! Even your walls provide built in absorption. Although usually, this is NOT enough. Especially in small rooms. Of course, if the walls are concrete, there is very little absorption as they are not a sealed membrane. Drywall/stud walls create membrane traps, which work at specific frequencies. Well, enough ramble. Later.
fitZ
Well first I should have said de-coupled from... Oops.Amped said:
Yeah, I was mainly referring to the reflections from nearby surfaces and the phase/combing effects, etc. And being that at the floor there is that 'one-point' bass boost. Like in a corner you get double the effect.. But I can't seem to think of the correct term for it.
Any body?
Never gave much thought as to how the floor was vibrating. Seems like that would be pretty far down in the mix of things.
Wayne
RICK FITZPATRICK
New member
Why else would you de-couple the amp from the floor?
It would have nothing to do with acoustics, unless a mic stand was on the same surface. But most engineers use isolated mic clips anyway. Anotherway is to build an amp "box within a box" isolator, although the other players couldn't hear it(if built correctly). You would have to monitor in headphones, but it would isolate it from the room, thereby not creating any resonant sound in the room itself.
fitZ
Amped
New member
Fitz, its gonna take a lot of power to get three layers of 3/4" OSB to react like a diaphram, especialy when the floor joists are 2x10's 16" OC. Fortunately, this is a free standing (pier & beam) building with nothing below except dirt. You might remember my thread titled "Quiet Zone" from a year or so ago. It pretty much defines my settup. I just picked up some 4" foam so Im gonna give that a try along with the 703. I know Im gonna have resonance at certain frequencies, I just want to try to minimize them as much as possible for rehearsal more so than recording. I just picked up a Hartke bass rig with no casters and theres a lot of surface to surface contact. Thanks for the response!
Roger that. I'm just focusing from the other direction (as well as messing with the original point of the thread- shame on me.RICK FITZPATRICK said:Why else would you de-couple the amp from the floor?
fitZ
)But I see the acoustics of it coming ahead. For example, an amp on the floor, a mic four or five inches from the grill -also being six or eight inches from the floor. It'd probably be fine but it's right up there with multi-pathing off a music stand into a vocal mic with things to keep an eye on.
Wayne
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"..But I see the acoustics of it coming ahead." You know what, scratch that. Hell, it's not like I have some handle on which is bigger.
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RICK FITZPATRICK
New member
Not really. But since there is only dirt undernieth, and there is no one to bother, what the hell
Nothin you could do about it anyway. Just for your own reference though, what I am refering to is TRANSMISSION via the resonant frequency. Even a small portable radio could do it. Thats why real studio designers lower the resonant frequency of the floor to at LEAST an octave below the lowest frequency the monitors will reproduce. Then match the wall transmission loss to the floor. If on a de-coupled slab, then the walls/ceiling set the low frequency resonance TL/ target. Everything else, such as doors, HVAC, windows are spec'd to match.At least this is what I understand. But I'm no expert.
Cool. Nice rig. Good luck with the de-coupling. Roger that mixit! I do too. One step at a time.
fitZ
