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Linn Isobariks - replacing the mid and bass drivers with Falcon units

nostromo

nostromo

pfm Member
I've been running active Linn Isobariks for about 20 years now. I really loved my Linn Kan MK2's before that, for about the same period. I've had several other speakers when I was much younger including Sara's, Kef 104Mk2 and Mk1s (these were my first). I use a Linn Aktiv +Dirak crossover (which I've rebuilt to replace the glichy xlr connectors, damaging the PCB in the process, I managed to recover from that crisis with some great support from PFM members here) 6 x LK280 power amplifiers (recapped by myself with Mundorfs and Elnas, one runs hot and David Elwood of this parish suggested it was a 'tant' but I don't know what that is...it's working and I have several spares (long story won't go there now) and a Holo Audio Spring 2 KTE Dac with an internal preamp and a nice remote. I sold my LP12 with the Kans, Karik, Genki and Kairn about 20 years ago along with about 500 LPs. That was a big mistake in hindsight, it was a rash decision (seriously/embarrassingly cheaply), the kids were being a handful and money was tight and I thought the future was digital (bought MDAC believe it or not and the JW saga began).

A good friend is also an active Isobarik enthusiast and has a lot more money than me ( Klimax LP12, Akurate amps nuff said). His room is bigger than mine and his setup is very different. He's got Morel tweeters and Scanspeak mids and Falcon B139s. It's the Falcon B139s that really interested me as to my ears in his setup the new Falcon B139s sounded a little tighter and more dynamic than my 40+ year old Linn B139s.

So for a couple of years I've toyed with the idea of replacing my B139s with the all new Falcon B139s designed by Malcom Jones who did the original Kefs too...I've had a couple of chats with Jerry too at Hifi shows. Post Christmas I get a message with a 10% off offer from Jerry, I bit the bullet and for £1300 I got 4 x B110 and 4 x B139 delivered which I thought was very reasonable. I've been sat on them for a couple of months now (other issues in the house etc.) but now I've set about doing the job....so far it's been much harder than I expected and I'm about half way through I guess. The wire and bolts issue has created a pause, so I thought I'd start this thread now rather than after the job was completed. I have no experience in this field whatsoever which will become clearer as this thread progresses, the nearest I've come is laying some composite decking in the garden last year (came out well...better than I and most who know me expected).

I started with decorating the room before Christmas, new paint on walls, ceiling and a new carpet layed (by myself).

These were the new puppies out of their boxes, they look and feel like really high quality products to me, I hope they sound as good as they look:
https://flic.kr/p/2pDrauw
https://flic.kr/p/2pDpXwt
https://flic.kr/p/2pDjqex
https://flic.kr/p/2pDqwdw
https://flic.kr/p/2pDoSBi

This was the setup before I started:

https://flic.kr/p/2pCZWgk
https://flic.kr/p/2pCUmhH
 
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Nice! I really like what Malcom/Falcon have done to keep things going on the driver side of things. Hope all goes well as you get things sorted!
 
meanwhile....I've cleaned off all the silicone from the cabinets, the no nonsense silicone remover was very useful. I wiped clean and gave a light sanding to the wood and a single coat of matt black paint to restore to the original state ready for the drivers.
https://flic.kr/p/2pE4xUK
https://flic.kr/p/2pE3SYH

The correct bolts are finally on their way and I'm debating wheher to go the neoprene gasket route as suggested by @david ellwood or go the silicone route. I did notice that even the Linn factory managed to get some silicone and that black gunk onto the business ends of the B139s see here:

https://flic.kr/p/2pE4xVr
https://flic.kr/p/2pE3izx

The B139s weigh about 5kg each and I wonder if the silicone not only seals them in but supports their weight too. Going the neoprene route would mean the 4 bolts (M5 x 25mm hex 8mm spanner) would be on their own supporting these monsters. The silicone would be messy and I'm sure I'd get it places it shouldn't go and would be pretty much a permananet fix, whereas the neoprene would be easier to fit and subsequently remove if ever required....I envisage using some contact adhesive to stick it to the wood and just rest the B139 on it without glue and just tighten up the bolts and hope it's air tight.
 
Christopher Connolly-Marsh on the Facebook Linn owners group had some keltik gaskets made up, not sure if these fit isobariks, but they fit falcon B139's in keltiks.
 
I've just realised I missed a few steps in getting to what is shown in post #4 above, so to fill in the gaps see below:
Removing the mid and bass drivers it's best to use M8 and M7 bolts respectively see post #4 here.
I screwed the M8 bolt into a hole of the B110 without going more than 1-2 mm into the hole to avoid pushing on the wooden baffle below and then using a claw hammer and a bit of ply covered in an orange cloth bag (to spread he force and to protect from scratches) like this:
https://flic.kr/p/2pD1tdS
It's best to go very slowly and once it begins to lift, stop there and do the same process from the opposite end of the driver by relocating the M8 bolt there.
https://flic.kr/p/2pCZW6k
Similarily the outer B139 can be removed using the M7 bolt.
https://flic.kr/p/2pD1sYJ
Again once it begins to lift switch to an opposite hole on the B139.
https://flic.kr/p/2pCYN2p
De-solder and remove the top B139 and take out the sack of wool below by pushing it away from the silicone holding it in place.
https://flic.kr/p/2pEfXFR
The rear B139 is the real challenge now. With the tools I have there was no good way to lever the claw-hammer while down in the box. So the best way is to carefully sit (not with your full weight of course) on the box with your legs astride the cabinet and simply pull the engaged claw hammer up with both hands and using your leg muscles to keep the cabinet down as you lift with your arms. It requires serious controlled pulling force and great knees! Again once it begins to lift switch to a different hole on the B139 to complete....I couldn't take a picture of this procedure as I was working alone. It can be done but you need to be feeling fit and strong.
https://flic.kr/p/2pCZVvs
The wires for the this lower B139 are very short and it is difficult to de-solder these, but just about possible. I decided I wouldn't be able to solder the new B139 and needed to lenthen both sets of wires and went about finding some wire. I also decided the removed bolts looked rather rusted and covered with silicone which was proving hard to remove, should be re-newed....the saga is documented here: Wire and bolts. I used two layers of shrink wrap over the soldered wires.
I then spent a couple of days removing the old silicone, with some assistance from no-nonsense sealant remover. You will need a small scrapper and even a craft knife used carefully to remove the silicone from under the captive nuts and a spike for inside the nuts. I then wiped it clean with a damp cloth, let it dry, then lightly sanded and gave a single coat of black matt paint in order to getting it looking as close as one can to what it may have looked like in the Linn factory...see post #4 above.
 
j_s said:
Christopher Connolly-Marsh on the Facebook Linn owners group had some keltik gaskets made up, not sure if these fit isobariks, but they fit falcon B139's in keltiks.
Click to expand...
Thanks for this👍, I'm now inestigating. I have a feeling neoprene gaskets is the best way to go.
 
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Just a word of warning that falcon B110a's if to original spec should be a subtly different shape to original B110b
 
david ellwood said:
Just a word of warning that falcon B110a's if to original spec should be a subtly different shape to original B110b
Click to expand...
Well, you had me dashing to check and I can report they are identical and the new falcon B110 is an exact fit, the same as the original Linn. For me you are still the Isobarik oracle....:). I just noticed the new ones come with a gasket, but it looks ludicrously flimsy and I don't think I'll be using it.

The Falcon dropped in (not fitted yet):
https://flic.kr/p/2pEeBiu

The two units together:
https://flic.kr/p/2pEeBiV
https://flic.kr/p/2pEa7Ai

Could be a useful template for some better material which I'm considering.
 
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Keen eyed fishes may have noticed I added some cotton wool (bulk standard lying about in the shed) to the enclosures. I was thinking they could beneift with a liitle more and I may have inadvertently sucked out some into my vacuum cleaner while clearing up dust etc. While hunting around on the net for B139 ready made gaskets, I came accross this:
https://willys-hifi.com/collections...cts/mundorf-twaron-angel-hair-cabinet-wadding
I'm thinking while I'm here why not replace the wadding too....But I have no idea how much I need? Is 100g of the new stuff enough for all 4 enclosures (I've seen some behind the lower B139 wool sack too).
 
@nostromo - the mannie on eBay selling the Keltik gasket kits does sell the B139 ones separately as I bought a load off him a while back.

I have yet to start the different bass driver test - one day

Regards

Richard
 
@Richard Lines, I was wondering what happened to your epic bass driver test, glad to hear you haven't forgotten about it.

My plan here was a liitle bit similar to yours, but it got thrown off course almost immediately. I was going to just replace the B139s and see if I could hear the SQ change, good or bad once I'd put the speakers back in the exact same locations etc. Then I was planning to change the mids and listen again. The idea being that I would be able to report here the differences the Falcon B139s made on their own and then separately what differences the Falcon B110s made.

But once I lifted the speakers onto their backs I realised that I couldn't survive moving them twice, the buggers are just too heavy. So decided that once they were laid out on the operating theatre, to just replace the lot and save my back and any surrounding furniture and even the plaster on the walls. I must mention that once the drivers were out of the cabinets, I could move them with ease, even one handed.
 
I'm stuck at the gasket stage now, I have contacted Christopher Connolly-Marsh via facebook thanks to @j_s and am now in email contact. I hope I can get some gaskets from him. Otherwise I'm investigating making my own by cutting sheets of this:
https://www.amazon.co.uk/gp/product/B0CCF6PQV9/?tag=pinkfishmedia-21
I've ordered a small piece to see if it's suitable.
And while I was getting even more bored I ordered two bags of this:
https://willys-hifi.com/products/mundorf-twaron-angel-hair-cabinet-wadding?keyword=wadding
and a roll of this:
https://willys-hifi.com/products/rubber-gasket-reel-20mm-x-10m-black?keyword=ga
 
This site contains affiliate links for which pink fish media may be compensated.
Richard Lines said:
@nostromo - the lower or inner B139 might be a 'tight' fit as the new Falcon devices have the deeper chassis.

Regards

Richard
Click to expand...
Yes I can confirm the Falcon B139 is 20mm deeper than the orignal Kef unit in the Isobariks. I read somewhere this increased depth allows for a greater cone excursion and improved power handling. The polystyrene cone looks almost identical. I dropped the new units in the cabinets and they are a really nice snug fit....just waiting for gaskets from Chris and wadding from Willys to move on.
https://flic.kr/p/2pEr1PV
https://flic.kr/p/2pEqmZR
 
Thanks to @j_s of PFM I got into contact with Chris Marsh over at the 'Linn Owners' group on Facebook, who very kindly sold me a full set of gaskets for £60 delivered and I'm rather please with them as they are going to save me a lot of trouble and potential pitfalls messing around with mastic everywhere. Also in the future removing these drivers will be a doddle. The gaskets are I believe from several sets that Chris had made for Keltics, so the B139 and tweeters fit perfectly but the mids are round and double the thickness of ther others and will have to be modified a bit to accomadate the Falcon B110 which is not circular. From my inital look at the gaskets for the mids the modification looks doable, it's strange that they are double the thickness of the others, maybe something specific about the Keltic mid driver, I don't know.

https://flic.kr/p/2pGzkG6
 
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