Loudspeakers and Plasterboard

[Kroma]

Hi,

I bought some speakers, each weighing 7.5kg and some AVF speaker mounts

for 'hanging' them on my plasterboard wall. I've been putting off fixing them up for ages as I guessed it might be difficult but I've read up on the subject and bought bits and pieces to make it as smooth as possible in the meantime. However - near-disaster has struck!

On Monday evening I set about finding the studs in the plasterboard wall (on an outer wall of my 15-year old house) so that I could fix the brackets in line with the enclosed instructions (which state that you should only affix to a stud if you have plasterboard walls)

I used a stud detector and my hand (to thump/knock) and whenever I was sure I'd found a stud, I marked its edges with masking tape. I found 2 or 3 each side of my fireplace. From these I selected where the speakers would end up (unfortunately I couldn't get them to be symmetrical without risking electrocution).

I started with the speaker on the left of my fireplace and measured where the lowest wood screw needed to go, held the backplate of the speaker mount in place and screwed the 3 screws in. There wasn't too much resistance but it didn't feel hollow and the mount felt pretty sturdy when in place (even though the screws never seemed to totally 'tighten' when fully home).

I assembled the remaining parts of the speaker mount onto the backplate and put the speaker on (and added some screws to hold it there). All seemed well and good so onto the other side of the fireplace.

The stud detector had been a bit more temperamental on this side but I was confident that I chosen the right place.

I held the backplate in place and screwed the first screw in - it slipped in too easily and I realised that maybe I'd mis-judged!

I took it out again, had a few more thumps of the plasterboard and moved the backplate to the left a couple of centimetres or so.

This time, the screws did exactly what they'd done for the other speak mount - not totally tightening but it seemed secure. I assembled the rest of the mount and added the speaker (which is above my tv etc so had it fallen off I'd have had a £2000 replacement bill). Job done (or so I thought).

24 hours later, I checked on my work. The left hand speaker was still flush with the wall. However, the right-hand speaker had daylight showing through the top half of the bracket. As my tv was underneath I quickly wielded a screwdriver, took the speaker off and inspected the bracket. It was VERY loose!

I could pull the top two screws out about 8mm with my fingers but they then needed unscrewing the rest of the way. Maybe the stud was about 8mm behind the back of the plasterboard and had some 'play' in it? Maybe there was no stud there?

So, what should I do now? 36 hours after installation my left hand speaker bracket (with speaker) is still flush to the wall but of course, the screws didn't come to a halt when tightening them.

The right-hand speaker sits on the floor and I have 3 holes in my wall (which has slightly textured wallpaper).

Should I try to use plasterboard fixings or a) will a 7.5kg speaker + bracket be too heavy for plasterboard, b) will plasterboard without a stud act as a resonance board and c) if there IS a stud there, will a plasterboard fixing be successful?

To be honest, I'm not sure what to do - especially as my tv sits under where the right-hand speak is going. Also, how can I tell if my left-hand speaker is (and will remain) secure???

Any help and information will be gratefully accepted.

Regards,

Daryl

[Thomas Prufer]

Remove both speakers. Put them exactly where you want using these:

or

Don't overtighten. Two will hold far, far more than 7.5 kg -- more like 75 kg...

Thomas Prufer

[Christian McArdle]

You know when you've hit the stud, because the screws will be really quite difficult to turn. I suspect either that you may have used screws that were too short, or didn't find the stud.

To find a stud, use a bit of stiff wire (I normally use liberated CPC from T&E cable) and bend it. Poke it through the hole and if it goes no deeper than about 1.5cm, then it is right there. Otherwise, insert it further, rotate it and generally prod around until you have located the stud.

The screws you use should be something like 4mm x 50mm if the bracket positions the screw head near the wall. Add length if the screw has a considerable portion inside the bracket itself before approaching the wall surface. (i.e. if the bracket is 2cm thick, use 4mm x 70mm. Note that the screws supplied with brackets are invariably too small to hold even their own weight up, let alone something heavy like speakers.

Christian.

[Dave Plowman (News)]

The best type of plasterboard fixings are the steel type that spread out behind and use a bolt rather than a woodscrew - the sheds sell them. They're fine for a radiator, so a speaker should be no problem - if the fixing bracket is reasonably large. However, if a hole is close to a stud they may not spread out properly.

[Gordon Hudson]

Before decising there is definitely a stud there drill in using a 2mm drill bit and see if you get sawdust.....

it works for me.

[Ian_m]

Any help and information will be gratefully accepted.

Try these, seen these used to carry 20Kg plasma screens, by going through the board in block wall.

[Doki]

I'd be tempted to use stands...

[Mike Dodd]

Any chance that you've got metal stud framing?

[meow2222]

then you havent screwed into the wooden stud. Or perhaps you used screws much too short. Use something that goes 2" into the wall.

uhoh

You need to find the stud, and use 2 or 3" screws into it. Plasterboard fixings will hold at first, but IME tend to give way over time. Also you dont want speakers coupled to resonant board

If its dot and dabbed, ie there are no studs, just use long screws into the block wall behind. 4" screws should be pretty safe. Drill hole, Put your rawlplugs on the end of a coathanger and push them in, one after the other. You'll need at least 2 in each hole with that depth. And use decent thickness ones. Also I'd dot some plaster/filler in there first, as the brackets will be levered against the wall by this fixing, and PB isnt that strong. So drill, create a good lump of filler in there, then when dry redrill and plug.

clearly it isnt

NT

[karl]

[Kroma]

Thanks for the replies so far everybody.

An update...

48 hours after the job, the left hand speaker was still firmly attached to the wall but as a precaution I have now taken down BOTH speaker brackets and investigated with a paper clip.

It would appear that NEITHER brackets were attached to studs and I am starting to suspect that I don't have wooden studs as some of you have suggested. I'm not sure what the stud detector was picking up!

On both sides there appears to be another layer of plaster behind the front plasterboard. On the right speaker the back layer was about 5mm past the end of my woodscrews. On the left speaker, my woodscrews had penetrated the back layer of plaster by about 3mm (which I presume was what kept the speaker up).

My latest plan is to use plasplugs plasterboard fixings and longer screws. The longer screws should attach to the back layer of plaster and the plasterboard fixings should prevent the screws from slipping (I'll have to snip the end of the plugs on the left hand speaker though or the back layer of plasterboard will prevent them from opening and doing their job).

What do you think? Will this suffice. The left hand speaker did seem ok as it was but I imagine this will give me even more rigidity.

One last thing... is a plasterboard wall capable of holding a 7.5kg speaker safely?

Thanks again,

Daz

PS The last occupant of the house had used those big nasty self drilling wall screws (which somebody suggested) in several places throughout the house but they seem to destroy walls... our coat rack was attached with them - it fell down and bought chunks of plaster out with it.

[Thomas Prufer]

Eh? I've seen them used to hold up commercial shelving in new plasterboard, each one holding 20 kilos or so. Haven't seen or heard of one failing yet.

Thomas Prufer

[Thomas Prufer]

Wait a minute -- the big screw things are for plasterboard: cardboard, white chalky crumbly plaster, more cardboard. No good at all for plaster, the white stuff stuck to a wall with a trowel, no cardboard.

Thomas Prufer

[Christian McArdle]

plasterboard, each

The commercial shelving will be designed to produce only a strict downwards compressive force on the plasterboard, where it is strongest. In some cases, it will rest on the floor for extra strength. A small bracket can't do this, as the limited vertical connection with the plasterboard will require a considerable outward force on the board.

Christian.

[Thomas Prufer]

Well, it's wooden shelving, made by my mates the chippies, a handful to a few dozen installed in a hundred shops or so. They use the metal thingies to attach a strip of wood to the wall (which is usually plasterboard), and then screw their woodwork to that. They use the wood strip because it's a standard design across all the stores, and sometimes it's a brick wall. And then it may take a few plugs to get one to hold in the wall. No such problems with the thingies.

I asked if the huge metal screw thingies were any good, and they said yes, a single one would probably hold my weight -- I'm more'n 7.5 kg on a bracket!

Thomas Prufer

[Kroma]

These did - or rather it was the plasterboard which failed (pulled apart by the huge plugs). Mind you, there were several heavy winter coats on the rack at the time! I re-fixed it by drilling 3 extra holes and then I used plastic plasterboard plugs. It's still up!

Back to the original topic...

My speakers are still floor-bound. Is the idea of using longer screws into the back-layer of plaster combined with plastic plasterboard plugs likely to work with my 7.5kg speakers (3 screws per bracket)?

TIA,

Daryl

[The Natural Philosopher]

What you CAN do is inject copious quantities of car body filler into the cavity..or even expanding foam first, then car body filler, to 'spread the load' over a wider area of plasterboard. Plasterboard is strong enough, it just cant take the localised stresses..

[Fitz]

What he said.

Although I have a tendancy for over-engineering everything I do, I really think fixing anything heavy to plastboard (even with special fixings) is just saving up problems for later. I've had to do it a couple of places where there was literally no other choice, but I still don't like it. I'd simply go through the pasterboard into the solid wall underneath. Far simpler and more reliable.

[meow2222]

this has already been answered. do it if you want but if it were me I would not be relying on the plasterboard or the plaster to hold them up. It probably will, but you want a bit more than probably when falling off will cost you 2 grand.

NT