TG "The Loudspeaker" Build (Sort of)

[MistyBlue]

I am hugely impressed by the deviousness of the "Getting the Green Light" post. Have you considered PR for a political party? Despite its tongue-in-cheekness, I may have to steal some ideas from there. Whether they will work is another matter.

As to the Lowthers, Steve's Lowthers were pure sculpture. Whilst I can admire the acoustical engineering of the Domestic Disasters, they were, by any standards, pig-ugly. Even a splash of Hammerite paint would have transformed them. Mental note: Don't try poorly finished prototypes for domestic experiments because management simply doesn't appreciate the engineering, only the finish. I'm beginning to think that the lab needs bass bins using the 18" PD184 Precision Devices drivers (still unpacked), which could perhaps then be tried downstairs after management has "inadvertently" heard them working.

Shildon machine tools?

Thanks Morgan, I thought it would provide some amusement. Actually PR/politics is more the forte of the other member of the household, however, I am learning much! Feel free to use any of the ideas, but remember the disclaimer! The Lowther Domestic Disasters were frequently refered to as Daleks and not in a good way.

Good luck with "inadvertent listenings" - I have had mixed results with that in the past.

It was actually Brian Burn at Blue Diamond Machine Tools we went to in Shildon to get the lathe and mill reground. Very good, very friendly - a day out in itself due to the sheer size of the place and everything in it - a machinists Aladdin's cave. Worth looking up, but the website doesn't convey the true scale of the operation there. The bed/slideways grinder is immense!

[steve s]

Those speakers look great by the way
Hope they sound good.. would they make our next owston meet ?

Thanks Steve.

I did notice you guys have a regular get together up there. It sounds very interesting and would be a great opportunity to meet some of you guys and see what you’ve been up to. I wouldn’t want to impose though and turn up without an invite, especially as it would be quite an undertaking for us given our location. Although we have done “Northern Expeditions” to Shildon for the machine tools in the last couple of years.

Shildon is a couple of hours north of our meet up location
No invite required, its not our way.
but the next one will hopefully be 2025.

[Morgan Jones]

I looked up Blue Diamond Machine Tools. Looks like a very dangerous place for me to visit. I bought a 1960s Luthy sensitive drill press last week. Predictably, the electrical department is a nightmare, but the important bits look fine, although there has clearly been no maintenance for decades.

[Ant]

"I'm not having that in my living room."

That sounds familiar...

I have the use of a smallish bedroom at least, but it doubles as my office/storage room. And it's perhaps a bit small for larger speakers. But the biggest challenge is getting the weight of big heavy speakers up the stairs.

Im lucky that emma allows the fanes in the living room, and they arent as big as those are, even though they do look like a pair of washing machines, or a fridge freezer when stacked..
The off white cloth finish makes them less orrible though

[MistyBlue]

There has been a flurry of activity here, involving frantically trying to juggle various plywood structures into a more compact pile that resembles a pair of loudspeaker cabinets before they can take over the entire home with a scene from a WW2 movie incorporating wooden tank traps.

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We are pretty relaxed about the size now, despite the TV needing a riser block - More room for cuddly toys!

I think that they use up the entirety of the "Designated Footprint" though.

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[Morgan Jones]

That's beautiful woodbashing. I'm sure they'll sound good. But you're right, they do take up the Designated Footprint (and then some). I must dig out comparable pictures of my transmission line loudspeakers (positively compact compared to your washing machines). I wanted to finish said transmission lines in red Formica. First wife stated, "I'm not having a pair of pillar boxes in my living room." So they were done in satin black. Which now appears to be unobtainium.

[MistyBlue]

…….washing machines…….

I don’t think I’m going to be able to look at them without thinking that now!

I wanted to finish said transmission lines in red Formica. First wife stated, "I'm not having a pair of pillar boxes in my living room."

Daring proposition. I can see her point.

I always had a soft spot for transmission lines. I think it’s the simplicity of the ¼ wavelength tapered damped pipe that I like. Ivan Leslie (IPL) did a DIY flatpack range of them for many years. I have built a few, here’s one from 2009 with a little additional “pod” tweeter as requested for a friend.

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[Ali Tait]

Use a pair of S5TL's myself, thread on them here-
https://www.audio-talk.co.uk/phpBB3/vie ... tl#p194638

[MistyBlue]

Nice!

Excellent re veneering job by Colin as well. The original builder obviously didn’t get the memo about shrinkage of the iron on veneer and where to start first. Or perhaps they were just unlucky, and/or it crept over time. Shame. But they definitely look better now. Love the corner radiusing as well. I have some crazy ideas about that, and I will get to it shortly.

Interesting reading about the internal vs external crossover. The extra connectors issue is certainly a drawback. The issue around microphonics seems credible, guitar pickups/valves etc can do that – that’s why they wax pot pickups (or epoxy on EMGs etc) – I’ve done epoxy myself on pickups I’ve wound with excellent results. I seem to remember Ivan explaining how the red PP “supersound” caps he sold were wound then flattened into a squashed cylindrical shape to tension the internal foils, apparently to reduce microphonics. Even so, that doesn’t help the inductor coils though.

I like the idea as it makes the crossover easier to play with, although once it’s sorted, it’s done with.

As always, “your experience may differ”.

[Ali Tait]

Not sure if externalising the crossovers made much if any difference, but rebuilding with Mundorf and Audyn caps and Path Audio resistors certainly did.

Yes Colin did a great job on them, and radiusing the edges really does soften the look, particularly for a large box.

[MistyBlue]

Ever since the Lowther Domestic Disasters, (I actually called them Syncline horns at the time after likening the structure to a geological process, but Domestic Disasters seems much more appropriate now!), I noticed how birch plywood can develop an acetic acid type smell after a while which actually gets worse when exposed to high humidity. I also noticed that microbes seem to propagate on it quite well over time. This happened to the DDs when they were in storage, although it is also detectable in freshly cut dry birch ply as well. Ever since, I have gone to the trouble of coating the inside of cabinets as well as the outside to seal the wood. Probably unnecessary but it’s at least piece of mind.

Last time I used some low cost varnish from B&Q we bought for another (unrelated) project to coat the inside, but this time I decided to buy plenty of the same lacquer I use to do the outside. I chose this stuff to do the outside with good results last time https://www.wood-finishes-direct.com/pr ... 0403896308 in satin. I was particularly impressed with just how tough it is – I think they use it for the surfaces of restaurant tables and bars. At the time we were expecting to adopt some Furry Destroyers, hence the lacquer choice, but for various reasons we didn’t in the end. Recently I used the same stuff to do our new lounge table but in high gloss and we were impressed with it. It doesn’t provide the gloss level of the cut back and polished 2K, but it is MUCH easier to apply. A bit of a cop out if you are aiming for Living Voice Vox Olympian levels of finish but certainly easier, less toxic and more importantly removes the need for a spray booth etc or the expense of taking it to an automotive resprayer who will entertain doing the job. A happy bonus is that it has a pleasant smell similar to the Mega Electronics photoresist stripper (in fact the actual chemicals in question are both glycol ethers).

There is an area inside the cabs I will have difficulty in getting to when the top panel is glued into place, so I decided to coat the inside surfaces now rather than later, taking care not to coat any surfaces that are still to take glue. I can then use sprayable contact adhesive to bond the 60mm profiled foam onto the walls of the inaccessible area behind the midrange enclosure before glueing on the top panel. The aqueous chemistry of the lacquer helps adhesion by making the wood fibres on the surface of the ply stand up and then set in the dried lacquer, providing a roughened surface (no sanding) to key into the contact adhesive, instead of absorption into the wood surface layer if it was uncoated.

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[Morgan Jones]

On the topic of varnishing, I found I can obtain a perfect finish with polyurethane varnish using a varnish roller. It's a fine foam roller about 4" wide. It takes three coats for perfection, lightly rubbed down between coats. On the final coat, lightly dust it with very fine wire wool, then polish with silicone furniture polish. The surface will feel absolutely smooth to your fingertips. I do this for my bookshelves and also did an engineered oak worktop. Unfortunately, I did such a good job on the oak worktop that (being perfectly smooth) it looks like imitation wood.

[simon]

Yes I know what you mean. I've used four coats of water based varnish, lightly rubbed down with brown paper between coats, on small bits of oak, then a wax polish. And it does somehow look a bit unnatural. I wonder if it needs a light stain first to enhance the richness of oak?

[MistyBlue]

Thanks for the tips guys!

I will try them out on some test panels when I get closer to that stage and let you know how I get on.

[Morgan Jones]

I've just taken a close look at the oak and it looks fine today. But when it was first done about three years ago, it seemed too smooth. It now has a little grain/texture to its surface. I can only assume that the water content of the wood has changed. The pine shelves done last year (and just checked) have stayed silky smooth. Not that the oak is rough, just has a little natural texture to it. And looks real again, Looking at it closely, I see SWMBO has not always instantly mopped up spills; as she would say, "Tsk".