How much sound comes out the back of a speaker?

[Desmo]

Just had a brainwave for when we re-arrange our front room next year and need a quick question answered.

Our house is mid-terraced so we've got neighbours both sides. If we were to hang a TV on the wall, how much noise would go through to their room? The walls are only single skin brick.

Also, if I were to use my current speakers (Mission 773's) instead of the TV's speakers, would they be any better at keeping the sound out of next door? Thinking that as they could sit away from the wall by an inch or two that they might be better.

[Mark]

I believe that for best results, speakers are supposed to be at least six inches from the wall, but I'm not sure how many people actually do that (I don't).

Attaching speakers directly to a wall can certainly cause issues with vibration. Not sure how much of that will travel through the TV if it's the TV, rather than the speakers, that are attached.

[Kell_ee001]

The Missions would be better at reducing noise - we did that at our last place :)

I think you'd get better quality too which would mean you could keep them turned down more too.

[leowyatt]

I think about six inches should be fine, I have a pair of eltax speakers with rear firing ports and aslong as they are not too close the sound is fine and my neighbours never complained :D

[mejinks]

I think about six inches should be fine, I have a pair of eltax speakers with rear firing ports and aslong as they are not too close the sound is fine and my neighbours never complained :D

But they were deaf? ;D

Seriously though, use the missions for better quality, then leave your tv on and invite yourself next door to judge for yourself the annoyance factor.

[leowyatt]

haha no they weren't but being students probably did help :D it all depends on the kinda of house you are in.

In ours you'd struggle to hear much through the walls however in the gf's mum's house the walls are like paper :( you hear pretty much everything.

[Matblack]

Less than comes out of the back of you to be perfectly honest

MB

[Matblack]

On a more serious note

I wouldn't be worried about sound traveling backwards I'd be more worried about it traveling forwards. Right now your speakers are hitting an internal wall and some noise is being disapated then its being reflected back into the room. If you rearange the room most of the noise will be directed at a party wall behind your sofa position. Now with careful placeing of the sofa that should absorb a lot of sound but you will be aiming sound at a party wall.

Backwards transmission is pretty minimal, bass will be more of an issue as low tones can easily penetrate brick but they will be on the rebound as well. Our back wall is tanked, then brick and then earth and we never have complaints from the neighbours on the screen side of the room, although you can hear the home theatre in the dining room directly above the set up.

MB

[Will]

There's a certain space from the wall which does cause a harmonic at certain bass frequencies (I can't remember exactly the frequency) which is why when you put speakers in the corners of the room by the wall the bass is amplified somewhat. If you leave the speakers at least a few inches away from the back wall, especially with solid speakers like the missions, the amount of sound that will come out of the back should be minimal. If the speaker is well made then there should be very little loss through the back. Ported speakers (which I hate with a passion) will usually cause more resonance owing to the design. If you're concerned you could put carpet onto the back of your speaker or up against the wall (not very pretty though ;) :p)

[Dr. Z]

There's a certain space from the wall which does cause a harmonic at certain bass frequencies (I can't remember exactly the frequency) which is why when you put speakers in the corners of the room by the wall the bass is amplified somewhat. If you leave the speakers at least a few inches away from the back wall, especially with solid speakers like the missions, the amount of sound that will come out of the back should be minimal. If the speaker is well made then there should be very little loss through the back. Ported speakers (which I hate with a passion) will usually cause more resonance owing to the design. If you're concerned you could put carpet onto the back of your speaker or up against the wall (not very pretty though ;) :p)

Mission 773s ARE ported ;) Besides, all a port does is act like another driver (the air in the back of the cabinet causes the air in the port to act like a mass on a spring, albeit with a higher Q factor).

The reason that you get "more bass" when you put a speaker in any intersection between acoustically hard surfaces is because speakers, to all intents and purposes, radiate spherical waves. Thus on one hard surface you get "twice" the energy vs the loudspeaker in free space (as its now radiating the same energy in a hemisphere) - as you remove portions of the sphere you get the same energy over a smaller surface area. It has little to do with resonances and isnt frequency dependant, although the results of putting more energy out can be, depending on the performance space.

Carpet, unless wavelength/2, isnt going to do squat to help any bass penetrating a party wall. Even w/2 isnt going to be marvellous. Besides, you would make the room smaller by a ridiculous amount.

Desmo, you have a couple of choices if you want to avoid irritating your neighbours:

1. Keep the level on the down-low and use the missions (wherever they sound good, which almost certainly wont be up against the wall ;)) because they will tear strips from any speakers built into a TV, even though they are getting on a bit.

2. Install your system in such a way that it isnt firing at a party wall.

[Will]

You don't have to tell me ;) ;) Old hand at this crap now :( Unfortunately theory hardly every concurs with practice of audio/video setups - well certainly not on yachts. :)

I didn't know those missions were ported - still don't like ported speakers though ;)

Just use egg boxes you'll be fine :p

Ultimately there's little you can do bar not play the music too loud or point the speakers at the neighbour's wall. And try and keep the speakers away from the wall as the amplification you get from hard surfaces often sounds crap.

[Dr. Z]

Just use egg boxes you'll be fine :p

Thats actually a bloody good idea (though not the egg boxes, they are useless for everything bar flutter echo).

Diffusion!

Not going to be cheap though :p

[Will]

Turn your room into an anechoic chamber :cool: Have you ever been in one, it makes you feel a little uneasy really...

Though to be honest I think audio sounds better with a bit of reverb as most speaker systems are designed with that in mind.

[Dr. Z]

Turn your room into an anechoic chamber :cool: Have you ever been in one, it makes you feel a little uneasy really...

Though to be honest I think audio sounds better with a bit of reverb as most speaker systems are designed with that in mind.

Me? Doing an acoustics degree it'd be a bit silly if I hadnt ever been in one :)

Considering that in terms of the physics an anechoic chamber is not really that different to being outside, its a bit strange why they are so opressive!

Which speaker designers told you they were designing speakers with reverb in mind? Most design them for anechoic conditions and the ISO standards for measuring frequency response are all tested in anechoic conditions. Our listening room is fairly anechoic but done with diffusion rather than absorbtion. It was designed by Dr Cox, too!

[Treefrog]

I went from a cheapo pair of wall mounted speakers to floor standing Celestion Ditton f15s. At the same apparent volume in the room the cheapo ones annoyed my neighbour, the Celestions didn't. I'm guessing that the sound travelled through the solid walls better than through air, then wall. So I'd suggest using the Missions and keep the (better) sound where you want it.