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Physics Question - Amplifier Sound - Elevated or On-Floor?

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Physics Question - Amplifier Sound - Elevated or On-Floor?

Postby BassFacer67 » Fri Apr 03, 2020 11:42 pm

I'm curious to know, excluding all other variables related to acoustic treatment or apartment build, if an amplifier will be 'louder' to apartment neighbors below my unit if placed on the floor or elevated on a table for example? I assume vibrations from the amp would be touching the so they may have more direct contact and be louder, however one may argue that the amp itself isn't vibrating much but rather the space in front of the speakers where the sound waves are going. What do you guys think?
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Re: Physics Question - Amplifier Sound - Elevated or On-Floor?

Postby Martin Walker » Sat Apr 04, 2020 12:07 am

An all-in-one guitar amp could well transmit audio vibrations through the floor due to its loudspeakers, but a power amp alone won't transmit any noise to the surface on which it's resting - it's the loudspeakers that you'll have to decouple.


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Re: Physics Question - Amplifier Sound - Elevated or On-Floor?

Postby BassFacer67 » Sat Apr 04, 2020 12:38 am

I have a roland blues cube hot. Is that considered an all in one?

Thanks,
Z
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Re: Physics Question - Amplifier Sound - Elevated or On-Floor?

Postby Sam Spoons » Sat Apr 04, 2020 9:20 am

BassFacer67 wrote:I have a roland blues cube hot. Is that considered an all in one?

Thanks,
Z

Yes, the speaker is in the same box as the amp IIRC. As Martin said, it doesn't really matter where the amp section is as it's the speaker that makes the noise so would transmit that thought the floor structure.

BassFacer67 wrote:.... however one may argue that the amp itself isn't vibrating much but rather the space in front of the speakers where the sound waves are going. What do you guys think?

The speaker cabinet will vibrate, try putting your fingers on it when playing something fairly loud through it, direct coupling the speaker to the floor will transmit sound into the floor structure in addition to the airborne sound (and, probably more efficiently so louder to the neighbours below).

I loaned a mate a simple device to decouple his bass practice amp from the floor in his bedroom, it was a single 450mm square by 75mm thick 'egg box' type acoustic tile glued to a square of MDF, placed foam side down with the amp on tom worked very well, though obviously only for a small light amp.
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Re: Physics Question - Amplifier Sound - Elevated or On-Floor?

Postby Music Wolf » Sat Apr 04, 2020 9:24 am

The Roland Blues Cube Hot is all-in-one amplifier and speaker combination, referred to as a Combo.

Image

It is simply an amplifier and speaker housed in the smae box. The alternative is a seperate amplifier (Head) and speaker cabinate (Cab). Normally the head is sat on top of the cab referred to as a stack.
Image

As Martin said, it's the speaker that makes the noise and which needs isolating from the floor. A solid structure, such as a table leg, transmits audio vibrations. You would need to sit the speaker enclosure on a 'shock absorber'. Something which can turn those vibrations into minute amounts of heat.
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Re: Physics Question - Amplifier Sound - Elevated or On-Floor?

Postby Wonks » Sat Apr 04, 2020 9:49 am

Effing disappearing long posts. Curse you crap SOS forum software!

The OP just meant the combo rather than the amp section itself.

Inverse square law for sound means that the direct speaker sound at the ground will be about 10dB less at 30" away (say on a chair) than at 10" away (amp on the floor).

Worst case physical cab to floor transmission will be when it's on the ground. On a support/chair/stand, the support will first absorb some of the transmissions before they reach the ground. Stick a pillow under it for a further reduction in direct transmission noise.

You'll get room reflection contributions too, but they will be much less than the direct sound. Very slightly lower reflection contributions when the amp's on the floor, but not a huge amount.

So up on a chair/bed etc. is best for your neighbours.
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Re: Physics Question - Amplifier Sound - Elevated or On-Floor?

Postby ef37a » Sat Apr 04, 2020 10:36 am

You almost always want to get guitar speakers off the ground.
Not only do they fire into your knees and make tone setting a nonsense (what you hear up there is nothing like what they hear 'out there') but you get a bass lift that can make the sound 'muddy'.

And yes, vibration will couple into the floor and travel more efficiently. I NEVER got the hi fi fad of 'spikes' ? To make such a strong coupling to a floor is bound to colour the sound and upset them below.

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Re: Physics Question - Amplifier Sound - Elevated or On-Floor?

Postby shufflebeat » Sat Apr 04, 2020 11:16 am

The sound that will "carry" is the overlap of:

- the sound the amplifier is generating
- the frequency at which the medium (wood floor, concrete, ceiling, air) resonates. Some of the sound generated will not carry because it is absorbed or reflected.

This being the case it's difficult to say for certain but I can say with some confidence that if you can do this in consultation with your neighbour it will be better because:

- you'll be able to hear exactly the aspects of the sound you do/don't have to worry about
- noise which is being imposed on you is *always* more annoying than that which you have been consulted on.

My recently deceased neighbour complained about the kids bouncing a basketball. When I said I'd find a way to deal with it he said, it's only a problem between 1-3pm when I go for a kip in the back room. The rest of the time I can turn my hearing aid off.

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Re: Physics Question - Amplifier Sound - Elevated or On-Floor?

Postby The Red Bladder » Sat Apr 04, 2020 12:29 pm

Loud noises are a severe annoyance to neighbours, especially in blocks of flats. Placing a guitar stack against a wall can cause a great deal of annoyance.

Another good way to annoy the neighbours is to set fire to their bins.
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Re: Physics Question - Amplifier Sound - Elevated or On-Floor?

Postby ManFromGlass » Sat Apr 04, 2020 1:48 pm

I’m impressed that most of the folks here are helpful optimists!

It wasn’t stated in the original post but most here are assuming the idea was to not bother the neighbours. I was thinking of a thread a few months ago of a poster who had noisy bottom end turned up to 11 neighbours from hell and wanted some sonic payback advice.

:eh:
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