SB Acoustics monitors build

[DeZZar]

The other day I was talking to my neighbor and he remarked that he had just gotten some speakers off some lady on Gumtree (sort of the Aussie version of Craig's List) and after getting them they weren't working.

So I took delivery of said not working speakers on the promise I'd take a look. Well, the fact the poor guy paid money at all for these things is an injustice!

No idea what time period they are from but one look at them tells me they originally came partnered with one of those all-in-one in multi stack stereo systems. Appear to be a three way.



Wait....is that daylight I can see through the 'midrange'....??



..and I didn't even really need to look to know this was the problem!


I've seen bigger fridge magnets.....and that's the sum total of the crossover you get!


So needless to say my advice to my neighbor was that these should just head straight to the bin.

Given I have a spare sheet of 1/2 inch MDF, some left over veneer, some SB tweeters in stock and some other parts on hand.....do you want me to just build you a decent set of monitors?

[DeZZar]

The answer was yes of course.

Wanting to keep a similar sized cabinet I ended up pairing the SB29RDC tweeter with the SB17NRX2C35-4 6 inch woofer in a net 15L enclosure tuned to 40hz for an f3 of 45Hz. The woofer will take about 26 watts and will be good for 100db. I think that's more than enough for a couple of monitors.

Cabinet design is nothing fancy - just well braced and made from 1/2 inch (12mm) MDF sheet with cleats added to all the internal edges to strengthen it up. Front baffle will be 19mm solid wood.


I had some precision port flares on hand but I did end up getting creative with the port design and the 3D printer is now hard at work printing up this dual elbow solution.


Sheet stock cut and the braces completed.



Getting the glue-up under way!

[DeZZar]

Both boxes done.

Because these will be veneered I have laminated 3mm MDF on top and back where there is exposed MDF end grain to avoid any issues with the joints showing through the veneer in the future.


Opted for a solid timber baffle so gluing up some Oak boards here which I'll then stain to match the veneer on the rest of the box when it all comes together.


Onto the baffle tomorrow...

[Steve Lee]

Just needed an excuse, didn't you?

:D

Show-off . . .

[DeZZar]

Yeah - any excuse will do! :P

[Unbiasedsound]

Damn how much do you charge for your work Dezzar?

[DeZZar]

That's a very good question. In this case my neighbor is also my barber so we're sort of doing a deal/exchange and on top of that he'll have these playing where he does barbering so there is also a sort of a 'tell everyone who asks where you got them' thing.

Normally I would just charge parts plus labor. This would be maybe a two day build. I would absolutely love to quit my job and do this full time but I'm not sure how practical that might ever be. Maybe one day!

[DeZZar]

The compound port elbow about 75% of the way through printing...

[Geoff Millar]

You did all that in two days?! Amazing work, well done.

Geoff

[djg]

Nice work. I thought at first you were going to reuse the Akai cabs.

[DeZZar]

Nice work. I thought at first you were going to reuse the Akai cabs.

I was originally thinking that but considering they needed a new baffle, braces added, rear panel re-done, were made from 9mm chipboard and one of the corners needed repair etc....it was seriously just easier to spend 15min on the table saw slicing up some new panel.

[DeZZar]

hahahaha....I love Fawlty Towers!

[Ugg10]

More like “only fools and horses” sketch called Trigger’s Broom…….Had this broom for 20 years and still going strong, only had four new handles and three new heads!

[Wolf]

Just don't mention the WAR!

[DeZZar]

Got onto the veneering today. Slicing up some left over Tasmanian Blackwood veneer. I really love this veneer and I'm glad to see the left over pieces go to a good home.


Back and sides done - just need to finish the tops tomorrow morning and then finally onto the baffles.



Custom port elbow all done to. Test fitting here with the precision port flare.

[Steve Lee]

I suspect these beauties are going up against a wall due to the front firing ports?

(Splendid looking work as usual, BTW).

[DeZZar]

Yeah destined for a desk/shelf otherwise I might have ported out the back instead!

[danmarx]

That reminds me back in college when my roommate came home one day all excited he'd picked up a pair of 'sweet speakers' from a guy selling them out of, you guessed it, a white van. It was a shame he paid actual money for those speakers and they were as bad as you could imagine. The woofer and mid had those car-style metal grill covers over them, the tweeter was one of those piezo horns and it was covered in your standard gray car sub carpet. The port was like 3" in diameter but only 2" deep too, so figure a 12" woofer in a pretty big box (made of 1/2" particle board) was probably tuned to around 100 Hz. Needless to say, I wasn't as nice as you and didn't build him a real pair of speakers. I love that you 3D printed a port extension to fit around the window bracing. My son just got an Ender 3 printer and I've been wanting to 3D print something in the realm of speaker building. A custom port seems like the perfect thing. Anyway, build looks good, keep us posted!

[DeZZar]

I have to say the 3D printer is just about the most valuable tool in the shop! I started a thread a little while ago to share all the things I've been able to use my for - its an Ender 3 as well - great value printer!

Here's that thread - I also added a little cost breakdown for anyone that's wondering:

https://techtalk.parts-express.com/forum/tech-talk-forum/1471207-3d-printers-for-workshops

[uncola]

Wow great build process pics, DeZZar. are you going to design your own crossover too? I saw there's an open source waveguide for scanspeak tweeters on diyaudio people are 3d printing too. these ones https://www.diyaudio.com/forums/grou...ml#post5862360 https://www.diyaudio.com/forums/mult...-printing.html

[DeZZar]

Wow great build process pics, DeZZar. are you going to design your own crossover too?

Thank you!

Yeah I'll be designing the crossover for these from scratch - I'll post progress on that as well as soon as I get some measurements for the drivers in the boxes!

[DeZZar]

I didn't quite get to spend the time on these today as I would have liked but regardless some progress on the baffles.

I'm finding the solid oak a little challenging to work with - routing it is fear inducing as it splinters very easily and has a really interesting mix of hard/soft(er) wood through the growth rings - I think a two flute straight cut bit isn't the best and causes a lot of chatter. I'll have to hunt down some spiral or compression straight cut bits I think. Anyway after taking it real slow making multiple passes with shallower cuts the cutouts for the drivers are taking shape.

Happy with that fit :D


I don't know why I keep punishing myself with these extra little challenges but in a moment of creative flow I decided to overlap the drivers just a little which requires the face plate of the tweeter to be trimmed.


I'm curious if anyone else has done this before and how you did it?

Personally after thinking about it for a while I've opted for printing a custom sanding wheel. That is, a plastic wheel the same diameter as the woofer that I can stick a strip of sand paper to. I'll Dremel rough cut first and then attach the sanding wheel to either a hand drill or the drill press to sand the final dimensions.

Here's the target look anyway. Just need to finish the cutout for the port flare tomorrow.