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How best to seal woofers - silicone or ...?

irb

irb

pfm Member
I have some Pentachord speakers which I've been fixing up, and I'm going to need to come up with a way to seal a gap round the woofers - further info about the speakers on this thread.

Pics here hopefully:
P4051200 by grilled snapper, on Flickr
P4051204 by grilled snapper, on Flickr

When the woofers slide into place, there is a gap between the woofer frame and the cabinet, that needs to be sealed. I reckon the only way to do it is with a sealant gun and a long nozzle. But what sort of sealant is best? Silicone? I'm worried I'd never get the woofers out again.
 
That's what I'd use if I could. But I can't see how I'd get it into the gap.

There's also a danger it would fall out, in time. The photos show the bottom of the speaker.
 
Use silicone if you never want to get them out again.
Some foam or draft excluder etc would work.

Pete
 
The thing is, the woofers (a pair, mounted face to face, with an MDF spacer in between) have to slide in first, but there will be a gap of 2mm or so between the outside of the woofer frame and the cabinet. That gap needs to be sealed, in order to create a sealed volume in the cabinet. The gap will be hard to access because the magnet and frame will be in the way.
If a draught excluder or foam 'string' is self-adhesive I don't think I'd be able to get it in. If it isn't, it might fall out in time, and I'd have unsealed boxes, leading to incorrect operation of the woofers and probably over-excursion.
The best idea I can come up with right now is to apply a ring of tape (masking tape? Sellotape?) to the inner surface of the cabinet, where the seal needs to be. Then seal the gap with silicone, using a long nozzle. The silicone will stick to the woofer frame probably, so it won't fall out. But it won't bond to the cabinet because of the tape. It should still give an air seal, though.
Does that make any sense? Or is there a type of sealant that's not as sticky as silicone that would do the job, so I don't have to mess around with tape?
 
Silicone then cover with clingfilm, then mount and secure the driver while silicone is still liquid.
Let the whole thing set, you can then disassemble and remove or trim the clingfilm if you wish.
 
The only other thing I can think of is to squeeze a foam 'string' into the gap, then apply a little silicone, aiming to create dots that stop the foam creeping out the gap. But not so much that it glues the woofer in place.
 
Vinny said:
Silicone then cover with clingfilm, then mount and secure the driver while silicone is still liquid.
Let the whole thing set, you can then disassemble and remove or trim the clingfilm if you wish.
Click to expand...

I'll think about that. My initial worry is that it would be hard not to push the silicone around while sliding the woofers into the box. Could be messy.
 
Thank you for all the suggestions, everyone. It's a real head scratcher, this one.
Originally there was a cloth band stretched round the woofers and MDF, as a gasket. But it didn't actually seal the gap. It was a dodgy design, because if it had sealed the gap, the woofers would not have slid all the way in.
 
Something not as messy as silicone? Self-amalgamating tape? Not sure how long term it holds its shape, but it ought to be good for quite some considerable time.
 
Vinny said:
Something not as messy as silicone? Self-amalgamating tape? Not sure how long term it holds its shape, but it ought to be good for quite some considerable time.
Click to expand...

Cheers Vinny. That's an idea. I'll give it some thought.
 
Butyl tape?

It's a bit like Blu Tack, but much more sticky.
 
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Could you mark the position of the 'inner' woofer with a pencil, or measure down to the frame from the screwed face in the photo and then glue some little fillets around the inside walls just beyond this to create a lip. Then put sealing foam on the fillets or the woofer frame which will get squeezed and thus form a seal when you install the pair of drivers?
 
a.palfreyman said:
Could you mark the position of the 'inner' woofer with a pencil, or measure down to the frame from the screwed face in the photo and then glue some little fillets around the inside walls just beyond this to create a lip. Then put sealing foam on the fillets or the woofer frame which will get squeezed and thus form a seal when you install the pair of drivers?
Click to expand...

This was my own first thought. However, it would be really tricky to make it work, because of the design of the woofers. There are fillets glued to the inside of the box already, but they don't go all the way round - and that's because of the design of the woofers, which don't present a flat surface on the rear of the frame. (The rubber roll surround is glued to the rear of the frame, and it goes right to the edge in the middle of each of the five sides.) Hence there's no simple way to create a seal there.

I've pretty much decided I'm going to put masking tape round the inside of the box, adjacent to where the frame will be, then slide the woofers in, then silicone the gap. This stays close to the original design, but adds a proper seal.

I've ordered some extra-long nozzles for the silicone, which should help. I reckon this will be less difficult than trying to position something like tape or plasticene. If I want to take the woofers out in the future I'll probably have to slide a knife in and cut the silicone, but at least it should come off the box cleanly because of the masking tape.
 
Yeah, after I posted I had a closer look at the pictures and it isn't a simple task. Best of luck with the challenge 'cos it will be hard to see what you are doing with a bloody silicone gun in the way! Fat fingers, small gap syndrome!
AP
 
Thanks AP and everyone for suggestions and ideas. I'm waiting for a few bits and pieces to arrive, so I can go ahead. I'll post in due course.
 
I have used decorators caulk or gutter sealant . The latter never fully goes off .

I used silicone before. Had to use a car bottle jack to get the driver out :eek:
 
I have some black 'tar-like putty' that is in strips of plastic similar to blue-tak. This is ideal for sealing in drive units without the permanency of silicone. I'm not sure if it is still available though, I haven't bought any for years.

Regards
Peter
 
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