TG "The Loudspeaker" Build (Sort of)

[vinylnvalves]

Regarding router cutters, I went through a bunch of trend cutters that kept breaking. I was using then with the CNC, taking off 0.5mm cuts and they still failed. Got fully refunded for them as they were defective. Silverline ones from tool station are good for a while. I use either CMT cutters or ones from Wealden Tools - they last and hold an edge. Birch ply is easy to cut- compared to something’s.

[Max N]

I can also recommend Wealden Tools cutters, they were the best ones I found back in the day.

[MistyBlue]

I had an Erbauer 6.35mm cutter from years ago that was an absolute trooper and lasted ages. I had done several jobs with that over the years with all sorts of material including quite a bit of 30mm birch ply. I got that one from Screwfix. I think it must have been the second or third that I had got and they had performed pretty well up to now. Naturally, I bought another from B&Q recently as a spare – it lasted a few minutes. This one: https://www.diy.com/departments/erbauer ... oreId=1320. Upon inspection, I was shocked at how little material there is between the carbide tipped part of the tool and the rest of the shank. Unsurprisingly, the cutters always seem to break at this point. I thought I’d try something different, so I bought 3 of these from Rennie tools seeing that their milling cutters are quite good and these were cheap: https://www.rennietool.co.uk/collection ... 9136837705. They didn’t last long and the last one I used at a much lower feed rate and depth of cut which really gave me a problem with my back.

Thanks for the recommendations, as a result I’ve ordered 2 of these: TX206.4M https://www.wealdentool.com/acatalog/On ... TX206_2e4M
I also ordered some more from Rennie a few days ago as emergency cutters if one breaks etc. I’m pretty disappointed with them though, but it’s better to have a load spare as setting everything up especially with the respirator etc is a bit of a pain.

[simon]

They're a fair bit more expensive than the Rennies so should last much better... Be interested if you find the same as Steve and Max as I need some more - the moisture resistant flooring chipboard ruined mine including an uncut spiral bit I was trying out and overheated before I did much with it.
https://www.amazon.co.uk/SpeTool-Cuttin ... 17&sr=8-21

[MistyBlue]

Nice find with the carbide, not too expensive either. I had a look at some of those but was trying to be a cheapskate! With harder cutters, they get more brittle. I keep a selection of carbide slot milling cutters HRC50-60 to get me out of trouble when I snap taps in steel. They go through HSS tooling almost like a hot knife through butter, and I’ve saved many (metal) workpieces like that. The other saver is a diamond burr on a Dremel when all else fails.

When I do some more woodwork, I’ll report back on the cutters - I’m hoping I’ll be able to finish the job with them. Just some extra bracing panels (additional to the CAD drawing I posted) and the front baffles which I’m doing last to give some more experience with the tooling so that it can gain my trust for the flush mounting of the drivers. I’ve had trouble before with the cutter slipping in the collet and going too far in – so I’m pretty cautious when it comes to that. I tried it on the rear baffles, the first one was perfect, the second one decided to be a pain. It’s not the end of the world, I’ll just fill it with polyester filler, but it is annoying.

RearBaffles001.jpg (75.4 KiB) Viewed 1111 times

Talking of respirators, we got this years ago for the 2K laquer: https://www.aliexpress.com/item/1005002 ... ry_from%3A

The pump is great; has a Li ion battery and charger which is pretty fast, and a charge lasts several hours of use. The filters are good and all parts feature a NATO standard RD40 screw thread for interconnections (I’m a bit of a stickler for standardisation!), I just modified a brand new extra long vacuum cleaner hose by epoxying RD40 connections into it as an extended inlet so it could draw in clean air through the filter away from the working area. What isn’t so good is the masks themselves – feels like it’s going to break my nose after about an hour. So I ordered some alternative masks with some RD40 filter cartridges which arrived today:

Respirator001.jpg (115.79 KiB) Viewed 1111 times

The Scott Aviva 40 half mask is much more comfortable – night and day. The full mask https://www.thesafetysupplycompany.co.u ... d_source=1 I got for the lacquer, although I havent decided whether I will use 2K with this project - they are a bit big for it! All RD40 connections.

[MistyBlue]

There is something I’ve been dreading for a long time with this build. But todays the day.

For whatever reason, 18 Sound decided to give the 10NMBA520 a dual flange mount option on their driver. Maybe this was to facilitate it as a drop-in replacement for a JBL driver, (such as one in the design Troels used as inspiration for his design), and/or another manufacturers driver – I don’t know. It’s a little academic from my point of view right now.

18Sound10NMBA520Front.jpg (92.75 KiB) Viewed 1101 times

18Sound10NMBA520Side.jpg (71.05 KiB) Viewed 1101 times

18Sound10NMBA520Rear.jpg (78.49 KiB) Viewed 1101 times

What this does do, is complicate the routing for getting the driver flush with the front baffle – something I want to achieve for the sake of cosmetics as well as acoustically. After a quick dive into various manufacturers 10” driver technical drawings, it seems that the nominal round basket has an outer flange of 261mm (Faital/Beyma/Eminence) or 260mm (18Sound) with various depths ranging from about 10 to 14mm. Whilst it may seem unlikely now that I could decide I want to change the mid driver; I would like to have that option open rather than close that door now. Also, the 10NMBA520 has a step in the flange which makes the driver not so flush mount friendly.

On another forum (forget where it was), another builder used an angle grinder (!) to cut away the outer flange so that they could rout a circular pocket to flush mount the driver. This to me seems a good idea – except without the angle grinder! Dealing with the heat must have been a real pain and one false move and that’s an expensive mistake. A look at some of the residual glue used to bond the surround to the basket just adds to that apprehension – it looks and feels like the hot melt variety, or more likely a semi flexible PVA.

The mill is in the process of being converted to cnc, but is fully operational currently as a manual machine after a recent slideway regrind and rebuild (another long story!), but I haven’t got around to mounting the servo motors and configuring it yet, so I can’t use that to rout the front baffle even if I wanted to go that route. Luckily, I have a 200mm rotary table for the mill with a mounting plate that extends to 310mm diameter. With some compressed air cooling, I should be able to keep the heat from building up.

I have designed a cover that will protect the driver from swarf and chips and am mounting it on a melamine faced chipboard carrier that will also protect the cone. I was going to fill the cavities in the mounting “ears” and flange before I attempt to mill it, but I decided against that as I want to keep the heat from building up as much as possible.

[MistyBlue]

So here goes......

RotaryTablePlusAdapterPlate001.jpg (135.88 KiB) Viewed 1095 times

18Sound10NMBA520 3DprintedCover.jpg (76.04 KiB) Viewed 1095 times

18Sound10NMBA520 DTI dial in.jpg (121.86 KiB) Viewed 1095 times

[MistyBlue]

And several hours later..............Success!!!!!

18Sound10NMBA520 Milling.jpg (112.1 KiB) Viewed 1090 times

18Sound10NMBA520 Mod001.jpg (99.17 KiB) Viewed 1090 times

18Sound10NMBA520 Mod003.jpg (80.3 KiB) Viewed 1090 times

Now they are exactly 260mm diameter, ready for flush mounting.

[simon]

That must have been quite a relief! Extraordinary attention to detail though...

[MistyBlue]

That must have been quite a relief! Extraordinary attention to detail though...

Yes!......I had to put my big girl pants on for this one

I was more than a little relieved when I rigged them up for testing and Norah's voice confirmed all was well!

[simon]

I bet! You're braver than me.

[MistyBlue]

The new router cutters arrived yesterday. This was the situation up until then:

RouterCutters001.jpg (80 KiB) Viewed 898 times

First and second on the right are the Erbauer cutters. The second one was modified to use with a sleeve I machined with a single HT grubscrew in an attempt to make sure it didn’t slip in the larger 12.7mm collet, which worked great and for a decent amount of time, until it snapped. Interesting note: when I machined a notch into the shank to take the tip of the grubscrew, I was shocked that a plain HSS drill so easily bored into it. In other words – the shanks of the Erbauers are definitely not hardened. The third from left is a Rennie tool low-cost cutter; I will probably keep the ones I have that are intact as emergency stock. I’m not impressed by them. The intact one on the left was one of the new Wealdon cutters.

Today, I had another run at the woodwork, concentrating on the additional bracing panels. They are probably over the top, but it’s better to do it now than to regret it later.

18101SpeakersExtraBracingSml.png (211.34 KiB) Viewed 898 times

I changed the Rennie cutter for a new Wealdon one and got to work, making sure to not go mad with the stepdown. I was immediately impressed by how it performed and the next couple of hours went really well. Remembering the rule to stop cutter chatter – increase the speed and reduce the feed. Just when I felt as though I had cracked it and the setup was gaining my trust, it snapped. I was doing around 6mm step down cuts with a moderate feed rate (estimated 30 to 40mm s-1 or 1800mm to 2400mm min-1 at around 24000 rpm under load), so not exactly too hard. As a comparison, one of the longer lasting Erbauer cutters that went the distance was coping with around 10mm step down at about this feed rate. Upon inspection, I noticed that a small shard of the carbide edge had broken away from the cutter, probably just before it snapped. The second Wealdon lasted 3 minutes. Grrrr……

Maybe it’s me and I’m just expecting too much. I seem to remember going through a few cutters with the last speaker build, but this rate of attrition is a bit silly. Having said that, the amount of routing work is quite a bit more than last time. I did a check with feeds and speeds with different materials from various cutter suppliers and I’m not overdoing it. I don’t know……

“A bad workman always blames the tools”
Or…..
“You can’t drill a clean hole with a blunt bit” (Thanks Morgan!)

I did remember a company that a friend recommended to me for milling cutters which I took up and was indeed impressed by them. Shop-APT. I might give them a go. Also I might go for an 8mm diameter cutter. I will have to machine some metric collets (listening, Erbauer? ) for them. For now, I will just try to plough on cautiously with the Rennie ones I’ve got left until they all reach their demise and hope I can get the rest of the job done. Come to think of it, I don’t get this problem with milling cutters in birch ply. Hmm……..<lightbulb moment!>

AdditionalBracing001.jpg (157.75 KiB) Viewed 898 times

[simon]

This seems like very bad luck to be going through so many bits. A maximum depth of the diameter of the cutter is recommended, but I tend to do a bit less as the cheap router I use seems to struggle a bit. I don't see why your bits keep breaking though. Very odd. Do you use just the one router or does this happen in multiple routers?

[MistyBlue]

I'm using just the one router - the Erbauer. It doesn't seem to have any runout in the spindle, but you raise a good point - it does seem more likely that I'm just going too hard on them.

The new router is about twice as powerful as the old one, so it's easier to snap tools I suppose.

I only have the front baffles and the crossover/tweeter mount 'apparatus' left to do. So fingers crossed if I don't go mental with the feed or stepdown, I should get it done.

[Max N]

I think I always used 1/2” bits