SpeakerTalk

[Paul Marchant]

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.

[Paul Marchant]

So, the current plan is that at the weekend (late Saturday morning), all the bits of the KM1s will be assembled, connected and powered for the first time in my ownership.

I have replacement screws and bolts on order to replace the fasteners on the HF drivers (rusted and a bit chewed up).

I have the 8mm cap-head screws to attach the LF enclosures to the centre chassis coming from Amazon tomorrow.

On Friday, I'll dig out a USB SPDIF interface and a decent DAC and make up a couple of phono -> XLR cables.

I am not aware of any outstanding driver issues (apart from the slightly sagged LF driver in one cab - I'm hoping the flipping it 180' will immediately solve that).

As far as a quick poke with an oscilloscope goes, the amps all appear to be working.

We'll see what comes...

[Paul Marchant]

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://i.imgur.com/ojAjwd3.jpg

So, I seem to have worked out the software.

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

https://i.imgur.com/A7NyU3S.jpg

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.

[Paul Marchant]

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://i.imgur.com/XXeIGuo.jpg

https://i.imgur.com/GVWRNQz.jpg

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://i.imgur.com/mn9jQx8.jpg

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

https://i.imgur.com/NlqOPwz.jpg

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.

[audiolabtower]

Good luck!

[Paul Marchant]

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://i.imgur.com/87n5nHC.jpeg

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

https://i.imgur.com/vnqFFtU.jpeg

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.

[audiolabtower]

Bad luck. My B300s are still perfect after all these years (as are the other drivers - no ferrofluid or foam surrounds to worry about!), but they are the original cast ones rather than the pressed triangle revamps. However with the same internals it should not make any difference. Presumably they have had a heavy workload in their lifetime with much high power.
I rotate the BC1 drivers every 5 years or so and that keeps them fine, they are well known for sagging, a feature of the compliance needed for the bass in that box coupled with the cone treatment for the magical midrange.

[Paul Marchant]

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://i.imgur.com/N1QvDd6.jpeg

[speakerguru]

Admiring your patience.

[Paul Marchant]

I'm regretting not doing the driver 180' thing months earlier in the process. I was tempted, but space at the lockup is in short supply. My concern with limited working space and being more or less in the dark was causing damage to a cone.

On another note, when I fitted the two dust-caps, I was a bit liberal with the adhesive on one of them. Do you categorically know if MEK will / will not damage the bextrene cone if I use it to neaten up the glue? I can't find a definitive answer to this on the internet...

[speakerguru]

Don’t risk any solvents on Bextrene. What adhesive did you use for dustcap to cone? If it’s now reasonably solid then carefully cut of the excess ( if you really must) Skillful scalpel use required

[Paul Marchant]

This stuff:

https://www.bluearan.co.uk/index.php?id=TUFBLACKEN99

It's just cosmetic - there's a little blob at one point around the dust-cap.

Might be worth a gentle scrape with a blade, might be better to leave it. I'll have a look again on Friday when I next go to visit the LF enclosures and try to talk myself into leaving it alone.

[speakerguru]

Don’t know that one.

KEF used Bostik 4141, a white water based adhesive which dried clear, for dustcaps, bitd.

[Paul Marchant]

And this week's update...


I've been over to the lockup where the bass cabs are languishing, and gently caressed my cones (ahem).

Two only slightly rub now, a considerable improvement from last week. The third appears to have completely fixed itself.

I've given myself a stern talking-to about not trying to clean the excess glue off the cone, and it seems to have worked so far.

Another couple of weeks, and I reckon it'll be time to get everything together once more and run them up.

[Paul Marchant]

I've once again visited the lockup where the LF enclosures are living and tickled my transducers (ahem).

Some improvement has been noted over last week. There's less rub on the two that haven't yet fixed themselves, but not a big change. The third one appears fine.

Soon....