BFM DR280 Build

[mrtcat]

The band is starting to get busy and we decided that it's time to invest in some decent PA cabs to replace the god awful Peavey 2x15's we've been using. Problem is we're all way to tight to splash out on big brands so I'm building my own. I love the idea of having something a bit more special too.

I've got plenty of woodworking experience as a cabinet maker. Speaker experience comes from having built a sub woofer boxes for my friends when I was a bit younger then progressing to bass cabs, and full range /monitors in recent years.


This is my first ever BFM build and I thought I'd jump straight in at the deep end and go for a pair of Bill's DR280's. As these are a bit of an experimental test of my abilities and a chance to make a few mistakes I'm going to use some 12mm ply sheets given to me by a customer. If I surprise myself I will defo be hunting down some really nice baltic birch and building another pair for more long term use. If these are solid and I'm happy with them I may sell them off unloaded on here to fund the top notch materials.

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Ok so tools wise I'll use a reasonable range of kit including circular saws, jigsaw, table saw, router, 1,000,000 clamps etc

Bills plans are great and very descriptive. I am rapidly learning that these are not to be used as a basis to "ad lib" a bit. Everything is done the way it is for a reason. If you're going to build your own BFM stuff follow Bill's advice to the letter and take your time. There's great support from the forum but as long as you read carefully and stick to the plans you'll be fine. They cost $15 a set and that's a bloody bargain if you ask me - Thanks Bill!!!

Probably the most important thing to do is get the right adhesive. Wood glue will not work on Bill's designs. Bill recommends PL polyurethane construction adhesive which is very strong and has brilliant gap filling properties which is vital as you need everything airtight and this allows for small imperfections in your cutting. I struggled to find this in the UK tho so I did some testing of other PU stuff and found this to be the best:

[url="http://www.thegluepeople.co.uk/index.php?main_page=product_info&cPath=6_10&products_id=33&zenid=00e669a4213085ba954ec380ad93803c"]http://www.thegluepeople.co.uk/index.php?m...54ec380ad93803c[/url]

It's magic stuff as it expands loads and then sets rock solid and at only £4.26 a tube it's very well priced. Thus far I'm half way through the first tube. Be warned tho, if it gets on your fingers it takes weeks to come off.

Right on with the build!

First up is the horn baffles

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I'm doing two cabs at once to make life just a bit harder. Parts are not desperately easy to clamp but again the plans tell you how. You'll see I screwed them too but now see this is overkill. Next time I won't. I'll leave the screws in tho as they won't be seen at the end.

Edited July 5, 2011 by mrtcat

[mrtcat]

Next stage:

More cutting out, used the router for the baffle and throat horn support slots. Driver spacers attached too. As per instructions I have now pre fitted speakers so I know they'll fit right when I come to put them in at the end of the build. I'm using tee nuts and M5 bolts to secure the speakers which is more than really necessary but I just feel more confident that way.

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Time to cut out my butt cheeks! I used my router with a self made jig, it worked really well and cost nothing.

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The plans show exactly how to mark up curves etc using a 26inch arc (length of thin batton with screw in 1 end and a pencil exactly 26inches away from the screw) and it worked well. This allows you to mark where the access panels need cutting out and where the inner horn curve will be.

Now it starts to get interesting. You start to assemble the bits together and start measuring. What I love about the plans is that Bill accepts there will be some variation in cutting accuracy and explains how to trim / sand parts until you have the exact right width / angle between top and base.

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You may notice I jumped the gun a bit here and fitted the urethane semi circle bits that fill the cavity inside the speaker cone a bit. This became a slight issue later and re-itterated to me that following the plans to the letter was important.

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That's about as far as I am with the woodwork to date but spent some time over the weekend with the tweeters. See next installment!

Edited July 5, 2011 by mrtcat

[mrtcat]

I'm going to go for a melded tweeter array. This basically means I'll be putting 22 piezo tweeters into each cab. My decision was largely influenced by the fact that a friend runs an electrical and plumbing trade store and they had 100 pulse tweeters buried in their store following an order cock up a few years back. He was glad to see the back of them as they were just gathering dust and let me have them for £20. I'm not convinced they'll be as good as CPC's own but for £20 i'll take the risk and if they turn out poo I'll fork out for the CPC ones at a later date. I'm also gonna build my own high pass and low pass filters.

Started by building the tweeter jig from Bill's jig plans. ##Bill's jig plans are a must and at only $1.95 a bargain##

Then cut as described and started glueing.

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It's important to get a good seal so i spot glued them with model aircraft cement then went totally bonkers with hot melt.

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I used the off cuts from trimming them to make supports that have really stiffened the array up.

The final array is OK but bot amazing. Next time I will make sure my gluing jig is more perfect and have now seen many builders on the forum doing some gluing before making the 45degree cuts. This should improve things next time. Not to worry tho they are airtight and rigid and although not perfect it'll be hard to see unless you're right up close. I now realise that my big mistake was not leaving the edges on the end tweeters in each array. I'll rectify this later.

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Then it's time to wire them. The plans make this simple. Each array consists of two banks. Each bank is wired in parallel and the two banks are wired in series.

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All 44 tweeters on the jig - don't panic they're not all wired as one this is the two lots just sat next to each other!

That's it so far. I'm hoping to be done in the next few weeks so will keep posting up my progress. Hope someone finds it useful but if not I'll not be surprised!

Edited July 5, 2011 by mrtcat

[gilmour]

DR280 - very brave for a first build, but looking great so far.

[Big Mick]

Looks like a good start to the build. There's lots of suggestions for foaming PL adhesive in my Jack 12 build thread.

[url="http://basschat.co.uk/index.php?showtopic=111770"]http://basschat.co.uk/index.php?showtopic=111770[/url]

Have fun.

Cheers, Mick.

[mrtcat]

Thanks chaps,

Really enjoyed your thread Big Mick and would love to see a finished picture. Am really staring to appreciate the expansion of the adhesive as it really makes things airtight and also holds incredibly strong. A good sharp stanley knife removes the excess once dry to leave a nice clean join. Going to give the build some quality time this weekend although gigging tonight fri and sat. Will post progress over the weekend.

[Big Mick]

Ahh pictures! Well it's not quite finished yet, just needs paint and grille.

Cheers, Mick.

[mrtcat]

Bit of progress this weekend but not as much as I'd have liked. Got to bend some ply tho which is nice. Hoping it creeps and settles tho as initially it put strain on the front supports where the tweeters will go and they were bowing out a bit. I'll keep it strapped tight for a while tho and hopefully this will help. Also the supports will be in next and they should help nicely.

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Sorry for not doing more pics, I get really carried away and forget to take photos whilst I'm building.

Unless you've built these before you can't even start to comprehend how many clamps I needed to get this far

[Marvin]

It's looking a very neat and pro build

[mrtcat]

[quote name='Marvin' post='1093033' date='Jan 17 2011, 08:10 PM']It's looking a very neat and pro build[/quote]

Low resolution pics are definitely the way forward

[mrtcat]

Ok so a little more progress. Been slow the last couple of weeks as work is busy and have been helping friends out with a kitchen fitting on weekends. Should have more free time this next few weeks and really want to get these finished.

Firstly i countersank most of the screws on the side wall of the horn. I then filled them with car body filler and sanded them back. This was messy but I think it'll be well worth it when they're done. They're going to be fairly unusual looking so may get people looking more closely at gigs so want to at least try to make them look presentable.

Then I added the throat supports. These take a little trimming to get really tidy and level but should be well worth the effort when I get to adding the main box sides.

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Have now added the half round black 4inch tubing at the back. Found a 2m length in a skip so lobbed it into the volvo and it fitted perfectly. Makes a real mess when you cut it on the table saw though. Little black flecks of plastic EVERYWHERE! It's a super static to so sticks to everything. Not to worry looks good now tho.

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Hoping to get my butt cheeks bent this weekend.......................and do some ply bending too!

[mrtcat]

Butt cheeks well and truly bent on one of the cabs. Gigging meant less time to build than I'd hoped for but still some progress. Will hopefully get second cab up to speed tonight.

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Bending the ply was relatively straightforward but an extra pair of hands was definitely needed. End result is very pleasing though and you can feel just how strong it's gonna be. Staring to get excited now as there's a distant light at the end of this tunnel!

[gilmour]

Looking good, and you're making really good progress on these.