Gale 401s -- failed project resurrected...
- Thread starter Mr Tibbs
- Start date
I like your style (buying in a pair of Peerless mid's, just in case).
Thanks for your advice - I'm happier now to go ahead with the surrounds I've got. They may not have the same profile as the originals but at least they exactly fit the cone and chassis.
Mr Tibbs
OK, some good progress to report - the four bass drivers are refoamed and looking good, with no rubbing of the voice coils when the cones are pushed in or out. The process wasn't difficult, just needing a steady approach and the application of the supplied instructions.
Here's a pic showing the prep just before the surround is glued to the cone. The PVA glue is applied to both surfaces and allowed to become tacky. The cardboard template was my idea - it helped me make sure the glue went exactly where it needed to go and also made sure of perfect cone/surround alignment;
The next pic shows the dust cap removed and the VC shimmed. This is necessary to ensure the proper alignment of the VC while the outer edge of the surround is glued to the chassis. No attempt is made to pull the outer surround into alignment with the chassis - it simply finds its own spot and stays there while the glue dries;
The four completed bass drivers;
Mr Tibbs
Here's a pic showing the prep just before the surround is glued to the cone. The PVA glue is applied to both surfaces and allowed to become tacky. The cardboard template was my idea - it helped me make sure the glue went exactly where it needed to go and also made sure of perfect cone/surround alignment;
The next pic shows the dust cap removed and the VC shimmed. This is necessary to ensure the proper alignment of the VC while the outer edge of the surround is glued to the chassis. No attempt is made to pull the outer surround into alignment with the chassis - it simply finds its own spot and stays there while the glue dries;
The four completed bass drivers;
Mr Tibbs
Tony L
Administrator
Impressive stuff. So you had to take the dust-caps off? How did you do that? Also how did you clean up the driver / basket in preparation, i.e. get the old manky surround off so cleanly? Can't see myself ever having to do this as my speakers are all either paper surrounds or compression horns, but information like this is very useful to retain just in case!
Tony.
Tony.
pure sound
Trade: manufacturer/distributor
Nice work. Is the compliance of these surrounds (and resulting Fs) as per the originals or is that not as critical on an IB speaker?
I guess someone with plenty of experience may get away without shimming the VC but I didn't want to risk ending up with rubbing voice coils, so the dust caps had to come off. A modeling knife with a fresh blade and just use the tip of the blade to cut round the circumference of the cap, close to the cone. Care is needed as the VC leads exit right under where the cutting is done!
Cleaning the old foam surround away from the cone is just a matter of picking it off with a fingernail (that was my tool of choice anyway). I then very lightly sanded the area to get rid of any small lumps. To get the foam off the frame I used a sharp wood chisel and just pared it off. A quick rub round with emery finished the job.
I would doubt very much if these surrounds are an exact compliance match with the originals. They shouldn't be too far wrong though, and in any case they'll change with age until they eventually expire (much like the originals).
Looking around the web for info on the 401s, I was surprised to see that many of them tend to get their drivers replaced rather than repaired. Worse still, the replacements seem to be chosen on a basis of what fits the front baffle rebates rather than attempt to match the parameters of the original drivers. I've seen bass drivers and the Peerless mid fitted with plastic cones as replacements in 401 refurbs, so I'm happy at least to be keeping the original paper cones intact!
Rob, I'll mail him a link to this thread.
Thanks all ;-)
Mr Tibbs
Robert
Tapehead
Certainly was on a set of AR woofers that I refoamed.
Bass extension was quite different (better) using the correct foam kit. However, the two kits I had were quite different.
I guess 'close enough' should be 'good enough' after all these years.
Those Gale drivers look very like AR woofers.
pure sound
Trade: manufacturer/distributor
As is often the way, an IB speaker relies less on damping by the magnet than a ported speaker might and as a result the magnets are generally less massive. I can imagine some people fitting drivers with large magnets intended for vented use & then wondering where the bass had gone!
Setting Son
Karma, ne?
Excellent thread and impressive indeed, Mr T.
RustyB
Registered Ginga
Yes I do, full metal jacket ones, but extensively modified.
RustyB
Registered Ginga
Good question.
My 301's came with the woofers already re-foamed, but I didn't like the look of the replacements.
I replaced them with the same high compliance surrounds I use on AR's, and the Fs dropped from 42 to 35 Hz.
That was pleasing, but Fb remained at 80 Hz, which was disappointing, clearly the small working volume of 14L was dominating here.
However, subjectively, the bass was far better with the new surrounds, and I can only conclude that the driver now has a higher Qm.
Unfortunately I didn't have the WT3 woofer tester before I changed the surrounds, so can't measure this, but it seems reasonable.
AFAIK some of the 401's, possible later variants, used Peerless woofers, presumably the same one as in the 301,
model 83121, also used in some B&O's, eg the S55.
RustyB
Registered Ginga
Hmmm, I admire your enthusiasm, but, as I've said, my current room is 301 size only.
I do, however, know of another room, quite large, where a pair of 401's would probably work much better than the incumbents, which have only half the woofer radiating area.
Here's a clue: you can see aircraft from the window.