Rogers LS6 bass driver - glued to cabinet? Unscrewed, not shifting

[blotblot]

The polypropylene bass driver of one of my mid 80's Rogers LS6's (label attached) has sun damage (very silly!) resulting in an elongating crack about 0.5 to 1cm inside the outer edge, now 50% of the way round (see attachment). Beginning to sound buzzy - playing only very gently until repaired!

Hoping not to have to replace the bass driver as I cannot find a source of genuine Rogers replacements for the LS6 bass driver, although one bass driver was replaced by Rogers/Swisstone in Mitcham about 20 years ago.

So I am looking to see if I can add a fairly thin layer of M3 DP8005 repair on both sides of the cone. I have the glue, have rubbed down with fine sand paper, and want to do the other side too.

Having unscrewed the four screws, it seems WELL STUCK.

< Is this glue, or a degraded gasket/rubber? >

< Do I just pull really hard somehow, or apply heat first, or.... ? >

< Any ideas on how to remove, as I don't want to damage the cone, the woodwork or the metal chassis?? >

Getting a grip on the metal chassis is also proving to be tricky as it is recessed into the wooden front panel.

Very keen to try the glue option having received it, and if it works I may apply to both speakers so they are balanced!

< Also sources for a genuine replacement driver, if it doesn't work, as LS6 driver repairs/spares appear to have less mentions online than the LS3/5a that I also use. >

[Edward Huggins]

Why not attempt the repair from the front face only and leaving the driver in-situ?
Levering it out might deform the chassis BUT if you are determined to remove it, then drill a 2cm hole through the back wooden panel immediately behind the manget's centre and force it out with firm pressure from behind. You could use a thick wooden dowel or a screwdriver, tapped as gently as possible. The hole you have drilled can be filled later.

[Radio Wrangler]

Probably sealant/gasket gone sticky.

If you can rig up something to give a steady pull via all four screw holes, something with a bit of springiness to maintain tension, it may come free if left for a while. Oh and a limit stop to prevent catapult action

David

[blotblot]

Originally Posted by Edward Huggins

Why not attempt the repair from the front face only and leaving the driver in-situ?
Levering it out might deform the chassis BUT if you are determined to remove it, then drill a 2cm hole through the back wooden panel immediately behind the manget's centre and force it out with firm pressure from behind. You could use a thick wooden dowel or a screwdriver, tapped as gently as possible. The hole you have drilled can be filled later.

That's a grand idea! Thank-you!!

I was thinking of filing off opposite sides of some screw heads that don't quite fit, inserting through the screw holes once enough is filed off and giving a quarter turn and rigging up a system to pull on these.

Your method sounds so much better, as long as I don't drill through the crossover, as I have no idea where that is - I could peek through the tweeter hole if I can get the tweeter out!

[mhennessy]

Unscrew the 4 bass driver screws about 5mm.

Turn the whole thing on its front.

Wait.

It might take a while - you can help it along by slapping the back of the cabinet with the palm of your hand. I don't think the LS6 driver is very heavy, so it might take a few days.

The screws will catch it from falling out completely.

From the factory, there is no glue, just a thin gasket.

If you drill a hole in the back panel, you'll have to drill through a later of bitumen damping material and then a 1" layer of foam. That could get messy. I really don't recommend that.

The crossover is likely mounted on the rear panel, directly bolted to the PCB. At least, that's how it's done when they used a plastic tray to hold the terminals. Shame they moved away from that, because that comes out easily, giving you the access you need. The crossover is behind the acoustic foam, so looking through the tweeter opening might not be as useful as you think. However, it might allow you to poke a couple of fingers in to push on the rear of the bass chassis. But the tweeter probably has the same gasket material as the woofer...

If you like the LS6, you should try the LS7

[blotblot]

Every physicist's best friend - gravity! Another grand (and easy sounding) idea. Guess try that first, then move to the next level of difficulty.

Glad there is no glue involved.

BTW, I tried getting the tweeter out for a peek, and no problem. Big hands, but might see if I can get my hand in there to give the driver a nudge. I did spot the foam, and as you suggest, no sign of the crossover!

Really appreciate all these ideas...

[blotblot]

Originally Posted by Edward Huggins

Why not attempt the repair from the front face only and leaving the driver in-situ?
Levering it out might deform the chassis BUT if you are determined to remove it, then drill a 2cm hole through the back wooden panel immediately behind the manget's centre and force it out with firm pressure from behind. You could use a thick wooden dowel or a screwdriver, tapped as gently as possible. The hole you have drilled can be filled later.

Thanks.

I had thought of front repair only, but as the voice coil both pulls and pushes, and given these speakers are my 'give it some welly' speakers (unlike the LS3/5a's for a subtler listen), my preference is definitely to try to get some additional strength on both sides.

I like another poster's idea of gravity... might come back to this idea if I get stuck though.

[60 oldjohn]

Originally Posted by blotblot

I was thinking of filing off opposite sides of some screw heads that don't quite fit, inserting through the screw holes once enough is filed off and giving a quarter turn and rigging up a system to pull on these.

If you do any filling, take care not to get filings near the speaker, and clear all filings away when finished. Big magnets small steel particles not good.

John.

[Refugee]

Has anyone thought of using the driver itself to loosen the gasket?
If you can find some longer screws if the existing ones are not long enough to allow an obvious gap leaving them in a few turns so that the screws will catch the driver if it comes free.
Put it face down and connected to the amplifier and feed in a bass signal close to the maximum power of the speaker and the driver should push itself off the sticky gasket and will make a vastly different sound once it is resting on the screws.
If there is a port in the cabinet cover it with a block of wood wrapped in heavy cloth to increase the air pressure behind the driver.

[blotblot]

Originally Posted by mhennessy

Unscrew the 4 bass driver screws about 5mm.

Turn the whole thing on its front.

Wait.

It might take a while - you can help it along by slapping the back of the cabinet with the palm of your hand. I don't think the LS6 driver is very heavy, so it might take a few days.

The screws will catch it from falling out completely.

From the factory, there is no glue, just a thin gasket.
<snip> :

* * This worked! After 2 hours it was hanging loose! Thanks again. * *

I will provide updates on how the gluing inside and out works.

[blotblot]

Originally Posted by Refugee

Has anyone thought of using the driver itself to loosen the gasket?
If you can find some longer screws if the existing ones are not long enough to allow an obvious gap leaving them in a few turns so that the screws will catch the driver if it comes free.
Put it face down and connected to the amplifier and feed in a bass signal close to the maximum power of the speaker and the driver should push itself off the sticky gasket and will make a vastly different sound once it is resting on the screws.
If there is a port in the cabinet cover it with a block of wood wrapped in heavy cloth to increase the air pressure behind the driver.

Another great idea - but I did try mhennessy's idea and it worked within a couple of hours. Good stuff, gravity! Particularly with a substantial driver...

Would definitely have tried this next, but perhaps not at full power given the current delicacy of the polypropylene!

Thanks

[Refugee]

Those flexible surrounds can be bought as a repair kit on the web.
Just measure up the ID and OD and do a search.

[blotblot]

Originally Posted by Refugee

Those flexible surrounds can be bought as a repair kit on the web.
Just measure up the ID and OD and do a search.

Thanks for responding - Are you referring to the gasket between the back of the driver and the cabinet, or the rubber flexible mount/suspension for the driver cone itself, between the cone and the chassis?

[blotblot]

Originally Posted by 60 oldjohn

If you do any filling, take care not to get filings near the speaker, and clear all filings away when finished. Big magnets small steel particles not good.

John.

Good point!

[mhennessy]

Originally Posted by Refugee

Those flexible surrounds can be bought as a repair kit on the web.
Just measure up the ID and OD and do a search.

Guess you've not looked at the pictures in the original post? The surrounds are not the problem.

[mhennessy]

Originally Posted by blotblot

* * This worked! After 2 hours it was hanging loose! Thanks again. * *

I will provide updates on how the gluing inside and out works.

That's great news - glad it worked for you

Good luck with the next phase of the repair. If possible, a couple of close-up pictures of the fault would be interesting - I'd like to see the failure in a bit more detail as I haven't come across this myself. Polypropylene is normally pretty robust, so I wonder what caused this?

Cheers,

Mark

[ajgriff]

In the first post the OP mentions exposure to strong sunlight as a possible cause but I wonder if clipping has something to do with it as the speakers are sometimes driven hard as well.

Alan

[mhennessy]

Yes, but I'm not quite convinced by that.

I must have seen hundreds of polypropylene bass drivers, but have never seen anything like that before. When over-driven, the glues tend to fail first - though actually I've had glues fail in normal use (polypropylene is notoriously hard to glue). I can recall an instance where the voicecoil (on an aluminium former) got so hot that the inner part of the cone - under the dust cover - was deformed.

I can't recall an instance of sun damage, either.

It's a mystery

[blotblot]

Successfully dropped the driver out, and started to carefully dust where I had gently sanded the polycarbonate cone …. and THE BRUSH WENT STRAIGHT THROUGH!. AARRGGGHH! (Photo attached)

More fragile than I had imagined!

Took pictures (attached) of the 'gasket' or what was left of it, and a side view of the driver with one connection unsoldered.

This 'gluing' is going to involve filling some holes where the polycarbonate has broken into smaller bits than I will be able to fix back in.... May have to try a bridge of Sellotape or wax underneath.

Still, a challenge perhaps for the next few days....

I will try to get some better and close-up pictures of the damage as you suggest. I have a feeling that this was the driver that was not replaced by Rogers in Mitcham, but the original, and it has been in a conservatory right next to the window, with direct sun perpendicular to the cone from about 1pm, which then swings round until 6pm (no grills on, stupidly, in attic I think) and a regular temperature of 40 degrees, occasionally 45 degrees on sunny days. Have been meaning to cover it up, at least when not in use....

Looks to me like the cone has crystalised. Not quite as see-through as the other speaker - will try to show a comparison.

Ooops. Hmmm.

And rarely played loud, in the last year. Musical Fidelity B200 at 50% only very occasionally. Mostly 5-10%.

Having got the glue, will continue with repair as nothing to lose, but I doubt it will be successful or sufficiently robust.

[ajgriff]

Quote from a specialst website:

"Because of the chemical structure of polypropylene, it has a high degradation rate when exposed to UV light like the Sun. The light causes the bonds holding the polymer together to break which weakens the plastic. This makes polypropylene unsuitable for uses that require long term exposure to sunlight."

Can't vouch for the accuracy of this information but it does look likely that UV is indeed the culprit.

Alan