Allison Bass driver repair

[trio leo]

I was scared of doing this repair for about 2 years, why I don't know they were knackered any way, what did I have to lose, so I bought the repair kit and this is how I did it.
this is what they looked like when I started

http://i1094.photobucket.com/albums/i444/trioleo/SDC11930.jpg
I made a cone support from a piece of hose pipe

http://i1094.photobucket.com/albums/i444/trioleo/SDC11941.jpg
then I used thinners to clean the metal basket and very carefully the edge of the cone, I used a craft knife and cotton bud

http://i1094.photobucket.com/albums/i444/trioleo/SDC11932.jpg

http://i1094.photobucket.com/albums/i444/trioleo/SDC11931.jpg
next I used a small blade craft knife to cut the central dustcap(scary bit) note the angle of the knife is parallel to the cone to avoid cutting the fine wire beneath.

http://i1094.photobucket.com/albums/i444/trioleo/SDC11939.jpg

http://i1094.photobucket.com/albums/i444/trioleo/SDC11940.jpg
I then used thin strips of plastic coated paper as shims to centralise the cone before glueing the new foam to the cone

http://i1094.photobucket.com/albums/i444/trioleo/SDC11942.jpg

http://i1094.photobucket.com/albums/i444/trioleo/SDC11933.jpg
after the glue had dried I then glued the foam to the metal basket with a soft brush

http://i1094.photobucket.com/albums/i444/trioleo/SDC11934.jpg
clothes pegs as clamps, taking that the shims centralised the cone I glued the foam to the basket where it lay, I didn't try to centralise that as well.

http://i1094.photobucket.com/albums/i444/trioleo/SDC11943.jpg
I used a piece of blutak to lower the dome exactly where it came from, as the cut was a bit wobbbly it was easy to line up where it came from.

http://i1094.photobucket.com/albums/i444/trioleo/SDC11936.jpg
I used a small file to weigh it down gently whilst the glue dried

http://i1094.photobucket.com/albums/i444/trioleo/SDC11937.jpg
and Voila! the finished Item, once the glue dried they look quite good I thought

http://i1094.photobucket.com/albums/i444/trioleo/SDC11945.jpg
back in the Allison 3 cabinet yahoooooo

http://i1094.photobucket.com/albums/i444/trioleo/SDC11946.jpg

I hope it has been helpful to anyone wanting to have a go, I missed out on 2 years of my favourite speakers now they are back sounding beautiful.
good luck

regards Al

[Theo]

Well done Al - pleased you've got them up and running again! Have the mid/tweeter units been repaired at any stage?

[keiths]

Nice work Alan.

[realysm42]

Does using glue change the sound of it? As it was never there in the centre to begin with, I'm guessing yes?

[Reid Malenfant]

Does using glue change the sound of it? As it was never there in the centre to begin with, I'm guessing yes?
I doubt it very much indeed. PVA is pretty elastic so it'll just aid in damping the thing, the only difference may well be in a very slight alteration of the driver parameters due to a very slight increase in mass.

It'd take some serious measuring gear to find that difference though :eyebrows:

So I reckon they'll sound as good as new :cool:

[Tim]

Fantastic little tutorial, thanks very much for sharing Alan - they look great :)

[trio leo]

Does using glue change the sound of it? As it was never there in the centre to begin with, I'm guessing yes?
I agree with Mr Malenfant, the centre cap is just a dust cover, I laid the glue over the cut line in order not to leave any air holes, as the glue is reasonably pliant when dry and there is only a small amount of it, I don't think it has made any difference, whilst it's hard to remember exactly what they were like when I bought them in the 80s they certainly sound fantastic now and I'm glad I took the plunge.
regards Al

[trio leo]

Well done Al - pleased you've got them up and running again! Have the mid/tweeter units been repaired at any stage?
Hello Theo,
The only thing that seems to go wrong with Allisons are the bass foam surrounds.the tweeters and mid range seem fine, I love the large sound stage Allisons give, and although the 3s are 4ft tall they get lost standing in corners.
recently I was lucky enough to try the new Albarry M1108 Mono-bloc power amps through my 3s, what a beautiful control and delivery, I can't wait to afford a pair.

I hope you are enjoying your LO7D, what a deck eh!

regards Al

[YNWaN]

Strangely enough, I have a pair of Alison Six speakers that need re-foaming; have just ordered the roll-surrounds now :).

[Alex_UK]

Top Job Alan (and good luck Mark!)

[trio leo]

Strangely enough, I have a pair of Alison Six speakers that need re-foaming; have just ordered the roll-surrounds now :).
The 6s were always fantastic VFM, positioned right on the right stands they're great little speakers.
Don't be tempted to re-foam without shimming the cones central.

regards Al

[YNWaN]

Don't be tempted to re-foam without shimming the cones central.

Really? I was hoping to get away without doing that.

[wiicrackpot]

I did a pair of AR6 using the same method and it came out looking original and sounded fantastic, i didn't re-center the flat dust cover and no issues with rubbing voice coil, i took extreme care when gluing and pegging as not to twist the assembly, i think it was made easier as the AR's had heavy paper pulp cones and the flat dust cap was the same. :cool:

Food for thought Mark.

wii.

[trio leo]

I was scared of cutting that central dome, but I watched several videos on youtube and on the foam ring manufacturers site, some videos were guys just taking pot luck and hoping the end result would be ok. I read up on the subject and the serious guys all insisted on shimming the cones central
.
I can only agree with them, in the first photo you see the cone is detached from the metal basket and you could hear the voice coils scraping the sides, so I shimmed and I'm glad I did,but make sure you blow out or suck out any dusty debris before you glue that dust cap back or scraping may occur.
In the last picture the finished drivers are sat flat, gently pushing them in and out revealed no contact noise at all.
Because I like to do things to the best of my ability the pair of driver repairs took me 3 days with glue drying time and pedantically removing the old foam and glue.
I'm glad I did, they now sound fantastic, good luck if you are doing it.

regards Al

[YNWaN]

I have access to a frequency generator so I might just glue the roll surround to the cone and then peg it it to the basket and run some swept tones to make sure the coil isn't rubbing.

[The Grand Wazoo]

A few days ago, I ordered a set of foam rings for a pair of 6.5" mid-range drivers. I'll be attempting the fitting of them without removing the dust cap. So I'll let folks know how I get on in a few days when they arrive & I've had a crack at the job.

The speakers are a big pair of Acoustic Research stand mounters - AR 44BX's.

[YNWaN]

Well, I've just completed the re-foaming of the Allison VI drivers I have. It all went pretty easily really - the only tricky bit is the rather arduous job of cleaning up the edge of the cone and the driver basket. Then apply the glue to the edge of the cone and glue on the edge of the new roll-surround. Use a load of pegs to hold the roll-surround to the driver frame and test with tones from a frequency generator (to confirm everything is OK) - then gradually glue the roll surround to the basket. The end result looks as good as new.

[trio leo]

Well done YNWaN,
I love the Allison 6s, they were always great value for money, I hope your repair puts them back on form.

regards Al