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Discussion in 'Amps and Cabs [BG]' started by AllodoX, Nov 28, 2001.
Am i the only one here who puts a rubber mat under the speakercabinets ?
i've never heard of anyone else doing it... what kind of mat do you use and why do you do it?
sounds like another one of those past-down-from-generation-to-generation type of tips. Or maybe it could work.... Please do elaborate, AllodoX....
I do it, here's why. We play on a hollow stage. Hollow stages become like speakers with any sound produced on them, if they're not insulated somehow on top. Also, really low frequencies tend to resonate thru the stage and are picked up in the mics, which is bad and really muddies up the sound.
I'd recommend doing this for most anyone.....
aha! very interesting. sounds factual enough for me to believe...good idea...i will try it next time I gig around....
I wouldn't imagine that a rubber mat would prevent low frequencies from resonating in a hollow stage. A mat even a couple inches thick won't block frequencies with wavelengths of 10 feet or more from being transmitted to the stage. It might block a little of the vibration but the sound waves will travel right through it. Hell, low frequencies can travel through insulated concrete walls. In order to effectively stop the transmission of sound waves the material they are travelling through must be at least as thick as the wavelengths. That's why when you stand outside a club or arena you can hear the bass but you can't hear any high frequencies. The walls are thick enough to block mid and high frequencies but not thick enough to block low frequencies
I didn't claim they took care of ALL low frequencies, but enough to minimize the "rumble" of the stage itself because of my amp. See, the mic stands, not so much the mic itself, carry the low-frequency up to the mic, a different kind of "bleed", if you will. My experience is truly that our sound is better when I place a mat under my amp. I don't need to get into the physics of sound to know what works. Reminds me of a current thread about lowest freq. and cabinet tuning; the real judge needs to be your ears and real-world experience.
While a mat won't completely block transmission of bass, it can be very effective at absorbing energy and damping out vibration modes of the stage floor itself. It might not eliminate all the acoustic anomalies you'd get playing on a hollow stage, but I'm sure it can help. The heavier and squishier, the better. For example, there is some gooey matt that people use for damping vibrations going to sensitive things like turntables. I suspect it is pretty dense and has extraordinary damping properties.
BTW, it is not true that a wall has to be as thick as the waveform in dimension in order to completely block vibration *transmission*. One can block bass transmission by alternating massive, stiff barriers (e.g., stone, brick, concrete) with "lossy" substances such as insulation. Cutting down on bass reflection is trickier, as Spacegoat implies - and often requires very deep (thick) absorption surfaces. (Note here the important distinction between reflection and transmission.)
I'm aware of that Mike, but I didn't particularly want to haul out the Sound Engineer's Handbook and get into a detailed analysis . I can see how a mat would damp some physical vibration, but it won't prevent resonance due to sound waves or boundary loading. I can easily make the portable stage at the local arena vibrate quite a lot with subwoofers placed 6 feet from the downstage corners, on that very dense pressboard they use to cover the ice surface. I'm skepitcal as to how effective this is, but I'm gonna have to try it just to see.
Some folks are making a kind of isolator made out of dense foam a couple inches thick. I looked at one, and it even has some serrated baffling on the under side. Intuitively, I think this sort of thing would do a pretty good job of isolating the cab from the stage. It's not solid foam ... it's got a couple runners that lift it off the floor. I think I saw it in MF, too.
I've got a mat under my amp for the resonance.
If you put your amp against the wall, it will usually sound like sh.t, specially if your amp has rear-ports.
because the wall will absorb the bass, and/or muffle it.
If you put your amp on a little distance from the wall, it will sound a lot better.
That goes double for the floor.
If you're a bedroom-bassist(tm), then you've probably experienced whining parents / sisters / neighbours, complaining that the cups are shaking on the cupboard...
if you put a rubber mat under your amp, you isolate the sound. the floor will not absorb and/or muffle the fundamental low tones. It will make sure that only the cab itself will resonate, giving you better tone. And it will keep your parents / whatever from b.tching you about shaking houses..
In my band, both the guitarist and me have rubber mats under the amps..
they're not even expensive.. you can buy a simple rubber doormat for about $ 3 at most hardwarestores. they're about 80x30x3cm, should be enough for most cabs. if your cab has legs or wheels, put a wooden plate in between.
I do something vaguely similar.
I put a foam "spacer" between my valve head and cab.
Most valves are "microphonic" to one degree or another - I find this really helps.
Is this something to do with incontinence?
Again, most floors (especially in houses) do not have the mass or right type of material to absorb LF energy. I'm not entirely convinced that it will give you better tone, because it only affects physical vibrations and does nothing to alter the propagation of sound waves. It may help prevent resonances created by physical vibration of a floor or stage, I'm going to have to try it myself to see if it makes any tonal difference.
It sounds like a damn high school science class in here! As was already stated, let your ears decide what does and doesn't work and don't worry so much about the why.
Hey AllodoX, you think a mat would work for me? I usually play on the floor (no stages for this band ).
This has been mentioned many times.
Your port placement doesn't affect your sound.
If you don't believe me, go look on acme's site, they have an article, regarding port placement, and how it makes no difference where the port is.
And here people have been posting to get a better sound via sound coupling to the floor, to put your 4x10 on the bottom and the 15's on the top. I tried it several times, and the difference was not noticable to me.
I can't imagine going through any effort at all to use a pad given the negligible, if any, difference. Of course, if you think you hear the difference and are willing to put the effort to cart around a pad and lift your gear on and off it, more power to you.
Maybe they're talking about port placement in the box (front, upper right as opposed to front, lower left)? It makes sense to me that if you have a ported cab and you place that port directly against a wall, it won't be able to "breathe" properly. It would be the same as placing a piece of plywood over the port.
Correct, but that's not port placement, that's overall cabinet placement. That's like saying "Well, would ernie ball slinkies be inferior to my 20 year old set of grease-ridden guitar strings, on bass, if I sanded the slinkies down to literally single wires?" It just doesn't really fit the context of my post, sorry.
I'm assuming you're correct as far as the breathing goes, but as far as I've known, as far away from the wall doesn't matter, if it's rear ported, just as long as you're not physicially blocking the port.
This is correct.
All bets are off if you physically block the ports, though