TG "The Loudspeaker" Build (Sort of)

[Morgan Jones]

I remember that! Glad to hear you took it to heart.

[MistyBlue]

Managed to get some plywood marked out last night. Here are the main internal braces marked ready for cutting with the router.

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Saw a break in the weather, and managing to dodge the intermittent showers, got some of the cabinet braces routed out. I forgot how much mess this makes, even with a 6.35mm diameter cutter. It takes around 3 lots of ~10mm step down cuts to get through to the bottom of the ply to avoid pushing the cutter too hard. It occurred to me I could have got the supplier to cnc cut the holes in the braces and save me the work, but I like to get hands on if I can. The circle cutter jig attached to the router was another toolmaking project I got doing before the previous build a few years ago.

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[MistyBlue]

It occurred to me I could have got the supplier to cnc cut the holes in the braces and save me the work, but I like to get hands on if I can.”

Actually, now that the novelty has worn off, I think my friends and family should stage an intervention and have me sectioned!

This will definitely hurt tomorrow.

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[MistyBlue]

Yep, as expected that last brutally punishing afternoon was painful for my back and knees, but also additionally in a way I didn’t expect. I make a point of taking safety and PPE seriously, but it seems that some of the fines/glue/whatever of the ply got through the FFP3 mask I was wearing and got on my chest, despite being outside, using extraction/filtration and general good housekeeping. Not seriously, but noticeable – and slightly scary. So, I’ve opted to take things up a notch and use a forced air respirator that I got for my run in with 2K automotive lacquer doing one of my guitars some years ago. It is very effective, but it is more uncomfortable and does make movement more restricted.

Today, I went outside for another run at it and before long, our long serving router that we bought for £20 in Proper Job 15 years ago has finally bit the dust . Got a new one from B&Q and now got some more toolmaking to do to adapt the circular cutting jig.

More side projects.......

[Morgan Jones]

Nice work. I was going to warn you that although a router does a beautiful job, you get a lot of leverage on the trammel and it's easy to overload the router's bearings. Looks like you discovered it for yourself; I wrecked my Elu router that way. I then bought a much bigger router. Which I don't much like (clumsy, so now built into a router table), so I also bought a DeWalt the same as the wrecked Elu.

Routing is always messier than you think. I once did a job and it was so messy that I decided I was wasting my time having the cumbersome vacuum cleaner hose fitted to the router. So I took it off. You will be unsurprised to learn that it became even messier.

[MistyBlue]

Nice work. I was going to warn you that although a router does a beautiful job, you get a lot of leverage on the trammel and it's easy to overload the router's bearings. Looks like you discovered it for yourself; I wrecked my Elu router that way. I then bought a much bigger router. Which I don't much like (clumsy, so now built into a router table), so I also bought a DeWalt the same as the wrecked Elu.

Routing is always messier than you think. I once did a job and it was so messy that I decided I was wasting my time having the cumbersome vacuum cleaner hose fitted to the router. So I took it off. You will be unsurprised to learn that it became even messier.

Thanks! We bought this, (although minus the custom base!):

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It is bigger and bulkier but much quieter – which I’m sure my neighbours appreciate. It had a half decent depth lock and the fine feed for getting the depth for flush mounting of drivers right – I seem to remember last time having a few problems with getting the right depth with the proper job router, but that was cheap and cheerful, so to be expected really. The most concerning thing is that a 6.35mm shank tool tends to slip if you overcook the step down – this one still does it from the testing I did earlier today. The collets are pretty basic and are more like sleeves that adapt for different shank diameters into a thin collet in the tightening nut – not exactly an ER or autolock on machine tools. Might be better off with a larger shank cutter for the extra grip, or weld a sleeve onto the cutter shank. I might have a think about a better collet system for it – but I’m in danger of going down another machine tool shaped rabbit hole again!

Those extraction hoses are indeed a bit of a pain and get in the way. We do actually have an industrial extractor that we got primarily to adapt for the surface grinder which I will probably bring to bear when I do the ring/plugs for the ports on the mill. The vacuum cleaner just isn’t effective for the fines and it leaves a fine film all over the place. I could be regretting not putting one on the router though, those fines or whatever are still on my chest which is concerning, but I do like the forced air respirator, even if it is a pain to use. I can also use a hole saw for the smaller holes without getting any fines or smoke when the wood gets a bit too hot.

[MistyBlue]

Managed to restart routing of the bracing panels today, after spending some time over the last week having to design and machine a base for the new router. The original one that was sold with it was a thin cast aluminium job so thin that there was no chance of fitting the circle jig, and I would prefer to keep using the circle jig I made rather than get a new one or remake it.

I’ve also done a slight modification to the CAD drawing I posted, seeing that I still have some 150mm diameter duct left from my previous speaker build. So, I’ve changed the dual ports to a single – this should also cut down the amount of work I have to do routing the rear panel and making the interchangeable ring/plugs for the ports. The rings and plugs will be done on the mill with a rotary table. It also means I can do the rear panel with the router rather than having to set the mill up for it or use hole saws for the smaller sized dual ports. The tuning remains the same – the single port is now quite short. I’ve also taken the opportunity to put more holes into the braces, to ensure they are not taking up too much volume inside the cab.

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[simon]

Looking good, can't wait to see what a 300L cabinet actually looks like.

I feel the router pain! I have a big 1/2" Triton in a router table but for free hand stuff I'm still using the half price special from Aldi or Lidl that cost £12.50 in the end. It's not great and I keep thinking I should get a deWalt, but at £300 I can't bring myself to do it. Until the other one breaks anyway.

And whilst I think my extraction isn't great I always get a large reminder of what it does do when I forget to turn it on...

[MistyBlue]

It may be a while before I have pics of the assembled cabs, I've got all the prep to go yet, and some other issues to sort out that you may find interesting. But I will post plenty of pics and I havent forgotten about the arduino/stepper/attenuator thing that I began a write up of!

I love those Aldi/Lidl deals. Once in a while, you get one of those cheap tools that just keeps going like a trooper! That proper job router was one of those.

It was my own fault really with the fines. I had already been aware that the vacuum cleaner doesn't have enough suction for it, from doing various stuff with the birch before. I thought the FFP3 would be sufficient - I was wrong.

A cautionary tale.

[simon]

I'm sure it'll take a while - there's a lot to do and it's supposed to be fun not a chore. One day at a time.

An FP3 mask is good enough for asbestos so should be good enough for wood dust. Perhaps the fit isn't quite a seal? I use one of these and can test the seal - never had any problems with inhaling dust (that I know).

https://www.screwfix.com/p/jsp-force-8- ... s-p3/1863f

[MistyBlue]

Thanks for the link. I will definitely have to get something like that, which is less restrictive so I can move about easier.

[simon]

Masks aren't the nicest thing to wear for long periods. There's also a Trend P3 that came out maybe 5 years ago that seemed less clunky? I don't how it performs though, and I quite like that the other straps to my head as it feels secure.

https://www.trend-uk.com/stealth-sm-tre ... ed-filters

And many others no doubt.

[Ant]

Thats the type i use, gets a good seal and isnt too annoying to use. Only thing with mine is the clasp on the strap is abit crap and tends to come a bit loose after wearing it for a while. Can just yank on the ends and retighten it though

[MistyBlue]

I should have done this ages ago when I first got the drive units and did impedance measurements after doing a short break in period on each driver, but I got tangled up in the new waveguide designs for the ribbons and CDs, and then doing FRs on them. I did do a brief listening session with each driver, but this evening I took the chance to do some nearfield FR measurements and more listening – especially to the midrange drivers without enclosures before the next stage.

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I’m impressed with the midrange – it reproduced various voices (eg Norah Jones, Mark Knopfler, Chris Rea, Floor Jansen etc) very nicely without any of the harshness with the CD in the current 2 ways. I could have happily listened for hours, which is a good sign. Whether the 1.3KHz xover point is high enough to avoid that CD harshness we don’t like is not completely clear at the moment. I also played around with Audacity’s eq settings and low and high pass filters, to mimic the crossover to see how the mid driver fared with various tracks. The AIC (active impedance control) does make a noticeable improvement to the sound as promised by 18 Sound, so I will definitely use this feature even if it does reduce impedance slightly lower down. I will measure all drivers when the time comes in a single session with enclosures and waveguides attached to reduce level errors. I have a sound meter, but I found that results can be a bit too variable to have real confidence in them, other than perhaps doing multiple measurements and taking the average.

I’m still taken aback just how big the bass drivers are, but also how light they are for the size. Rare earth magnets and cast aluminium baskets I suppose.

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I still have some more woodwork to do, but I’m waiting for some more cutters to turn up. The birch ply is particularly hard on them (and/or maybe I am too!). I’ve gone through about four 6.35mm cutters so far, two broke within minutes!

[simon]

Wow that's bad luck with the router bits. What brand were they?

I've not use birch ply for 15 years or more, but I can confirm that floor grade chipboard is excessively hard on tools, especially when they hit metal inclusions in the chipboard...