Interesting SBL tweak.

Posted by: garyi on 13 December 2003

Something has been nagging me about my SBLS.

When I got a new gasket kit, I choose to attach the pads with small pins as apposed to the staples (I couldn't work out how to get the staples in without a staple gun)

Anyway this was a messy solution, but a solution non the less.

However the sbls have been moved albeit carefully since then but I hadn't got round to a re-seal, after spouting off about how important this was I thought I better take some of my own medicine.

As suspected the spikes had pierced the pads entirely and gone into the wood (I knew this already because the gap betwen bottom and middle box was very small.)

I took them apart today, the plan was to remove the pads and swap them around to utalise areas of the pads which had not been used, (I don't have a new kit to hand)

Well it was all a bit messy and the pads were frankly trashed.

So I started by filling the wood with a strong epoxy glue.

Then I used a lid from a chocolate tin, cut it into pads. The metal is different, slightly stronger but almost exactly the same thickness.

After attaching them with the correct staples (whice required hammering small holes into the pads first) I re-asembled the sbls. As hoped the gap between boxes was slightly larger as the spikes had not pierced the pads.

The out come.

Well its all a lot better, I have been suffering a degree of boom with the speakers both in corners, but this has gone a long way to fixing the problem.

It got me to thinking about the whole spike arrangment between the two boxes. For instance if there was a way would it not be better that they were not that at all.
I was thinking perhaps four small ball bearings which could be used to give you the gap whilst the silcon seals, then can be knockoed out with a ruler or something?

Or if the spikes are required, but the best form of decoupling also a must what about some thin peices of steel in place of the pads, which could be attached in a robust fashion such as four screws, one per corner?

Anyhoo, I am very pleased with the results.
Posted on: 13 December 2003 by Jo Sharp
I asked JV about this and he replied that there are tolerances which can be taken up by the spikes penetrating the pads.

But they managed it with the PIPs on Credos.....

Jo
Posted on: 13 December 2003 by Allan Probin
Four ballbearings wouldn't work as there would inevitably be a small amount of rocking due to limits on the mechanical tolerences that can be achieved. Pressing the mid box gently down on the spikes allows the tolerences to be taken up. Three ballbearings would work though (Jo, the Credo uses three PIPs per speaker). However, if the ballbearings were knocked out after the silicon had set the joint would compress and you would loose the decoupling effect between the boxes.

Historically the Aluminium pads were an afterthought. When the SBLs were first designed the mid-box rested directly on the spikes. The Aluminium pads were only introduced to allow the speakers to be repeatedly dismantled and re-assemled with consistent alignment and without chewing up the wood.

Allan
Posted on: 13 December 2003 by Jo Sharp
Ah yes, of course.

Pip,Pip, Pip!

As Bertie Wooster might have said....

Jo
Posted on: 14 December 2003 by J.N.
Thanks Garyi; very interesting.

I also have the 'Superb Bloody Loudspeakers' and keep wondering about (and putting off!) a re-seal.

I've just bought some Intros for the number two system, so am thinking PIPS as well. Could it be the answer?

The PIP idea was conceived long after the SBL's of course, and is a much simpler soution to defining a fixed gap.

Dare we try it?

Care to comment Mr Dane?
Posted on: 15 December 2003 by Dev B
...but as a slightly counter point to Richard's excellent post SL2s have a very very small gap that in effect makes the middle box behave in a way similar to the SBL..
Posted on: 18 December 2003 by Martin Payne
quote:
Originally posted by Richard S.:

PS - re the old JV posts, is there any update on getting the old forum posts back from the archives?



Hmm, sorry, they still need a lot of organising. If PS is reading this - consider me reminded.

cheers, Martin

E-mail:- MartinPayne (at) Dial.Pipex.com. Put "Naim" in the title.