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Kef KM1 in need of repair.

No Friday update this week (I normally get bits done in the evening on a Friday when everyone's gone home at work).

My 2006 Ford Fungus decided that this was the week for one of the front brake calipers to stick on, and I can't, in good conscience, take it on my 100 mile daily commute on the motorway knowing I have defective brakes. I've picked up a couple of calipers and tomorrow afternoon will be 'fix the car' rather than 'fix the KM1s'.
 
Piksky said:
Going back to the ferrofluid purchase quantity shenanigans, just seen lots of these listed on eBay for various different manufacturers drivers: https://www.ebay.co.uk/itm/14550120...pid=5338728743&customid=&toolid=10001&mkevt=1

Assume the stuff you had to get was more specialised?
Click to expand...

I went for the current version of the now-discontinued stuff that KEF used.

As I don't know the first thing about the different types of ferrofluid, it didn't seem worth the risk of substituting a different type.
 
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OK, so a week has passed, and I've done some more.

It's fairly mundane and boring stuff, but necessary.

The amplifier packs and the speaker enclosures are on plug and socket connections.

After some digging, I discovered they're ITT Cannon Trident series connectors, which are still manufactured.
That's handy, because with the passage of time and - I think - some rough handling, there's broken latches on a number of the connectors.

I've purchased a quantity of plugs and sockets sufficient to replace all of the original ones.

They're constructed, like most industrial connectors, such that it's possible to disassemble them, removing the pins / receptacles and wires non-destructively. This would allow replacing a damaged pin in the existing housing, or in my case replacing the housings without having to buy new pins and solder them onto the wires.

There's a special tool to efficiently unclip the pins. I've purchased one.

I've done this sort of thing plenty of times before in my work, with all manners of different connectors. It's not particularly difficult or exciting, but from time to time you have to do it.

The sockets on the back of the amps were looking a bit sad:

https://imgur.com/YHx0aQR

and had a tendency to fall in when I tried to insert the plugs.

After removing a lot of screws, I was able to lay the rear panel flat on the bench to access the inner side. Helpfully, there was quite a lot of slack in the wiring loom, which made the whole thing a lot easier than it could have been.

https://imgur.com/NXGyKgY

I unclipped the sockets one at a time and disassembled them.

Then it was just a case of poking the receptacles into the new housings, ensuring that each one went back in the correct location.

Two of the three sockets on each amp have a blanked-off part, to prevent plugging the mid / tweeter enclosure into a bass amplifier channel. They will unclip (with some effort) and they got transferred across to the new sockets.

https://imgur.com/yGdU9Ef

Finally, the reassembled sockets snap into place in the rear panels of the amps, and it all goes back together.

https://imgur.com/lsWZxVG


The cable plugs come apart similarly to the sockets, with the same tool:

https://imgur.com/RKTnUKB

and I replaced the housings on the plugs for the mid / tweeter housings. There were a number where the locking tab / latch had broken on one side. In principle, it probably didn't matter much because the plugs and sockets are a reassuringly tight fit and probably wouldn't have wiggled loose, but the new housings were about £1.50 each and they're all getting replaced.

https://imgur.com/d18vKtG


Partially dismantled plug - the pins have been unclipped and the housing will now just lift off:

https://imgur.com/Eg0eTcc

And then reassembled, with new heatshrink:

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So, I still need to do the connectors for the bass enclosures. This will be another day, as they're over at the Big Yellow Storage place round the corner. I'm rapidly approaching the point where I need to haul all of them around to work, where I'll do the remaining four plugs, flip the drivers through 180 degrees to compensate for gravity sagging them over the years, and glue on two dust-caps. And then make some noise...

This will happen in the not-too-distant future, but will require a second pair of hands and someone with a larger car than mine. I've spoken to a mate who lives fairly close to where this is all taking place, and he's offered to help in a few weeks time.
 
It's busy at work at the moment, so I've only achieved a small step forward this week - re-assembling the midrange enclosures.

Further down the line, they're coming apart again and going over to the paintwork company we use at work for a cosmetic job.

I've got a house move coming soon (hopefully), and there seems little point in doing all the woodwork up only for it to get a ding or scrape with the move.

It turns out that reassembling the mid enclosures is a little harder than expected.

The recess in the back of the baffle where the B110's sit is slightly oversized, so care needs to be taken to get the driver absolutely central in the cutout. If you just drop 'em in, there's a good chance of having the edge of the surround touching the baffle. No bueno.

I spent quite a lot of time trying to get them central, and I'm not entirely happy with what I've achieved. It's difficult. The only obvious way I can see to do it is to overhang the enclosure off the edge of the bench, lie on the floor underneath it and make a judgement of placement of the driver. Then, you get up, wiggle it a bit one way or the other and go back underneath again and have another look.

With a second person (or a carefully placed mirror), I think it'd be a trivial task.

I'm going to ask one of my colleagues to give me a hand next week so I get the mids perfectly located.

They're held in by a single screw into the back of the big aluminium bar, which passes through a slightly oversized hole in the heatsink on the back of the enclosure. There's enough wiggle-room in this affair that during assembly, you can be out two or three millimetres in position.

I've done one assembly, and stopped there. They'll both get done properly in the coming days.

https://imgur.com/fK9sv7H

For now, I've left the plastic tweeter-guards that I rustled up in place, as I'm very nervous about one of the domes getting bumped whilst in storage or transit.

https://imgur.com/pxSkkIT
 
OK. Minor progress this week (none last week - super busy at work, no time).

The midrange / tweeter assemblies are... assembled.

This is a great relief, and marks a significant step in the whole 'getting them working' process.

https://imgur.com/a/gXPIMJa

The mids are centralised in their baffles to an acceptable level of accuracy. I did it solo, and I think it could be perhaps 1/2mm better. My plan was to stick one of our many broadcast cameras at work under it and do it with a monitor, but I couldn't find a wide enough angled lens to get a good framing of the image on a monitor.

I'll revisit this. At some point, it's all coming apart again to get the paintwork re-done, and that's when I'll get it super-accurate.

I've left the plastic covers I cut out for the tweeters in place for now.

I've ordered all new replacement screws for the tweeters (M5x8 cap head and M5x25 countersunk pozidriv) as the old ones are tarnished and a bit chewed up. I imagine Ebay will deliver those in the coming week.

The other thing I've done this evening is to clean the bodywork of the amplifier packs. The rear panels had tape residue on one and chinagraph pencil markings. It has troubled me every time I've walked past them for the last few months, and this evening I attacked them with my spray bottle of brake cleaner to get the chinagraph off, and then just a bit of soapy water on a cloth to get everything else off.

https://imgur.com/a/3HyzXk5

So now I'm at the stage where there's nothing more to do, for now, to the bits of the KM1s I've got here at work.

I've received permission from work to temporarily move all of the other bits (LF enclosures and the metal chassis that's the central structure) in one weekend (but I had to promise they'd be gone by the Monday).

I need to do some bits to the LF enclosures. I need to flip / swap the upper and lower B300s over (to deal with the slight voice-coil rub on one of the LF drivers where it's sagged over the years). I hope that flipping it through 180 degrees will instantly solve that problem. I'm fairly optimistic.

I need to affix two dust caps to the two drivers that are devoid of them. I have procured the parts and have the correct adhesive.

Then, hopefully, I get to make a lot of noise testing them.

This is dependent upon getting my mate with a bigger car to come in and give me a hand. I will be speaking with him about this again over the coming weekend.

The end is in sight, assuming no other problems reveal themselves.

In the meantime, I think I'm edging closer to selling my little rabbit-hutch sized house in Chislehurst and buying a place with an appropriately sized living room to deploy the KM1s.
 
OK. If all goes to plan, with no unexpected automotive or domestic crisis in the meantime, hopefully this coming weekend will be 'put everything together and make a lot of noise'.

My mate is coming to help on Saturday, and we need to move everything over to my place of work (I'm a keyholder, which is handy for covert weekend missions). There are a few minor bits to do to the remaining hardware.

It might all be done by the end of Saturday. If not, he's agreed to help further on Sunday.

I'm a bit nervous now. If there's unnoticed problems with tweeters or bass drivers, this is when I'll discover them.

The amps appear to all be working, but who knows how they'll cope with their first high-power test run in perhaps a number of years.

Details as it happens...
 
I've had the bolts / screws / washers delivered that I need. Good old Amazon and Ebay.

The outstanding thing, which wouldn't necessarily have stopped Saturday's planned work is that I don't have gaskets for the tweeters. I don't know if there ever were gaskets, as the tweeters are in their own sub-enclosure, but I'd have expected it.

The original plan was to get some foam sheet (got some at home), and get all Blue-Peter on it with a stanley knife and make some.

However, rather conveniently, at work today we had a laser cutter delivered. Hmm... I have some experience with such things from a previous job. "Hey boss, d'you want me to assemble and test it?" "Yeah, sure..." "OK then..."

https://imgur.com/ojAjwd3

So, I seem to have worked out the software.

I found some scrap cardboard to victimise to establish whether my idea would work.

https://imgur.com/A7NyU3S

That looks like it'd work as gaskets for the tweeters. I'll bring the foam in tomorrow and laser it after work. I'm not worried about the screw holes at this point. If I get time to measure their locations tomorrow I'll laser them out as well, if not I'll just punch the screws through and they'll make their own holes.
 
OK. So, tomorrow's the day. I am nervous.

Today, I've properly measured and CAD'd the tweeter gaskets and lasered them out of the 2mm EVA foam sheets I had at home.

https://imgur.com/XXeIGuo

https://imgur.com/GVWRNQz

They fit. Everything appears to be the right shape, size and place.

The other thing I've done this evening is to replace all eight screws for the tweeters.

There are four M5x25mm countersunk pozidriv screws that hold the tweeter to the cabinet, and four M5x8mm cap-head screws that hold the faceplate to the magnet assembly.

The old screws were a bit sad looking (rusty, and the pozidriv screws were a bit chewed up).

Things look a lot better now.

https://imgur.com/mn9jQx8

So, for safety overnight, I've put the plastic covers back over the tweeters for peace of mind.

https://imgur.com/NlqOPwz

Barring unforseen circumstances, tomorrow is the day where I either have them assembled and working, or discover there's yet more work to do.

Fingers crossed.
 
We're not there yet, it seems.

So, with the assistance of a mate, all of the LF enclosures got collected and moved from Big Yellow Storage to my place of work. The hope was to get everything finished and assembled and tested today, but it was not to be.

https://imgur.com/87n5nHC

Between the two of us, we replaced the last of the plastic connector housings with new.

https://imgur.com/vnqFFtU

The two missing dust-caps on one pair of LF drivers have been replaced.

All of the drivers have been swapped / flipped through 180 degrees.

I'm sure, back in August when I took delivery of them, one had a bit of coil rub when manipulated by hand, but the other seven were OK.

My hope was that flipping the driver through 180 degrees would immediately solve it.

Today, it appears that three have varying degree of coil rub. Curious, but I guess if one had sagged it's not unreasonable that they were all getting to the 'nearly rubbing' stage due to gravity and age.

Of the three, one's more-or-less OK now after an hour in its new position, but the other two still have contact between the coil former and the magnet.

I'm a little frustrated, because I'd really hoped to power everything up and run them today, but such things happen.

I have no doubt that, over a yet-to-be-determined period of time, gravity will pull things back into alignment. I don't want to pull the B300's apart unless there's a very compelling reason. I think that, as it stands, it's better to be patient (not a virtue of mine normally) and leave things for a week or two to see what happens first.

So, at the end of the day we took the LF enclosures back to the storage place.

They're much more sensibly placed now in the small lock-up that I'm renting than they were originally, so there's easy access to the drivers in each.

Once a week, in my lunch break, I'll pay them a visit and manipulate the cones in the hope that sooner rather than later the sag problem will fix itself.

And then they will get dragged back into work and I'll make a lot of noise with them.

Now we wait.
 
So, I've been over to the lock-up where the bass cabs are living, and given my woofers a wiggle (ahem).

Some progress has happened.

Of the three, one no longer rubs if manipulated.

The two that still do don't seem as bad as they were.

This is broadly as expected - slow autonomous progress with the assistance of gravity.

I'll see what they're like next Friday.

https://imgur.com/N1QvDd6
 
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