Custom Dual/Twin 12" Subwoofer

[ReTrO]

Thanks to plenty of inspiration from Synthesis's projects I have decided to build a new sub to 'replace' my current RTP-15 sub.



The RTP-15 uses a single Adire Audio Tempest 15" dual voice coil driver in a sealed enclosure of a 19" cube. Driven by an RCM Akustik Detonation DT100 II 150W plate amp in an external enclosure, via a nice chunky Van Damme cble terminated in Neutrik Speakon connectors. It's a bit big and heavy to be portable, and since I am moving house soon will need to find a new home.



The new project will use 2 Audio Drive AD12-300SB 12" drivers, as used in the BK Electronics Monolith subwoofer. Most likely both into a sealed enclosure, not sure on the size yet, the more compact the better. Amplification may be a BK plate amp, 300w unit, or a pair of the 200w modules would work quite well.

[Uncle Eric]

Sounds great Richard. Keep us updated and if poss bring it to one of our subtests for Charlie to get his teeth into :thumbup:

[SYNTHesis]

Cool. 8)~8-)~:cool: Looking forward to the details, pictures and eventually opinions.

[ReTrO]

I currently have WinISD Pro (alpha) for plotting box sizez etc.



Suggestions for better plotting and the LWT design would be great. It's been a while since I did this last.



I'm thinking at this very moment of running both units in individual cube enclosures each with a 200w amp module.

[ReTrO]

Right current thinking is as follows:



Each driver will have it's own sealed enclosure as compact as possible, but made in such a way that I can stack the units for use in a very small room (such as I curtrently have). Something simple like rounded vertical edges and square horizontals (i'll try to get a drawing). 25mm MDF should do the job, I've got an underused router and bits for most of it, though I think I will need a larger radius bit, to try and do 25mm ish.



Driven using an external power amp such as the Behringer A500. I'll put Speakon connectors into the enclosures to keep them air tight.



I can do some eq currently with my BFD (which is running very well on the RTP-15), and then think about a transform board for each unit later. I'll be honest, in saying that I'd like to make some very good finished enclosures first.



The drivers are due to arrive tomorrow. :D~:-D~:grin:

[ReTrO]

Finish wise I'll be keeping it a nice and simple black of some sort. I'd love a super high gloss, but will probably end up with something with a slight shine.

[ReTrO]

A couple of ideas for basic enclosures, showing the rounded corners, allowing stacking or not, but still looking good.



The finish I think will look very very good in a Fiat/Ferrari yellow or red. It should also be available in a spray form that I can use easily. Will need advice re laquering etc to get the final glossy finish, though should be ok for sealing and priming with help from Mr Taz. :)~:-)~:smile:



This has also got me thinking about refinishing my recently aquired Jamo D6 THX Ultra speakers in a glossy primary blue. Mmmm, that could be fun. :lol:



http://www.premierdivisionrugby.co.uk/avt/subs_stacked_90.jpg



Stacked pair.





http://www.premierdivisionrugby.co.uk/avt/subs_twin.jpg



Pair independant.

[ReTrO]

The drive units have just arrived, nice and heavy... :o~:-o~:eek: (for the size they are!).



I'm looking forward to making these up, very much now.



Next thing is to get the cabinets drawn up and find a larger rounding router bit for the corners. I'll use 25mm MDF throughout, with some crossbracing. Not sure on what filling, if any to use at the moment, but I can get some from my old work, as they use plenty in their ICE department.

[ReTrO]

I'm running a parallel thread on the DIYAudio forums as well for ideas etc. :)~:-)~:smile:



http://www.diyaudio.com/forums/showthread.php?s=&threadi (http://www.diyaudio.com/forums/showthread.php?s=&threadid=103418) d=103418

[ReTrO]

A quick Sketchup drawing of the old RTP-15 and a new enclosure (for scale).



http://www.premierdivisionrugby.co.uk/avt/old_and_new.jpg

[ReTrO]

A few more images after a change of thinking for the internal bracing. I was going to put loads in but decided against it for ease of build, time and volume being lost.



http://www.premierdivisionrugby.co.uk/avt/sub_1.jpg



http://www.premierdivisionrugby.co.uk/avt/sub_2.jpg



http://www.premierdivisionrugby.co.uk/avt/sub_3.jpg

[SYNTHesis]

Fantastic work. :thumbup:



Just a tip for you since your spraying:



http://www.premierdivisionrugby.co.uk/avt/sub_2.jpg



In that picture you can quite clearly see joints on the externals of the box. These will show through after spraying and tend to make the box look less than it could be.



For the front baffle and rear wall I notice your doing a rather chucky roundover. Consider running rebating the edge of each panel by around 2mm so the each panel appears to standoff from the rest of the enclosure. This then makes it clear that a gap was intentional rather than have an unsightly joint creep back through the paint job.



I do the same thing with all most projects. You can see better what I'm trying to describe here:



http://img.villagephotos.com/p/2005-7/1050288/tism100.jpg



Note where the baffle and enclosure joint and the gap between the two. Doesn't look out of place, unlike a joint that pokes through the paint and you also have the option of doing the panel in a different colour eg. veneer the enclosure and do the baffle in black etc.



The final area to tackle are the sides and the joints formed by the top and bottom panels. If possible you should 45 degree mitre just those 4 joints - no need to do the others. If that isn't possible the consider veneering to cover the joints up. I did this with my baffles because without, the joints would show through once sprayed up:



http://img.villagephotos.com/p/2005-7/1050288/veneer03.jpg



http://img.villagephotos.com/p/2005-7/1050288/tism54.jpg



I did write a useful guide on veneering here:



http://www.diyaudio.com/forums/showthread.php?s=&threadi (http://www.diyaudio.com/forums/showthread.php?s=&threadid=100835&highlight=) d=100835&highlight=



Of course you could just veneer all the enclosure section and do the baffle in a nice matt black instead of veneering and then spraying over that.



If your interested I can provide more details.



Please keep us updated on how the project progresses. :)~:-)~:smile:

[ReTrO]

All the advice is much appreciated. I'll pop both the suggestions into the design. I think I need to add some



A couple of things I need help with, after a walk around B&Q after work.



Source of:



25mm MDF - not in the large B&Q Warehouse, I susepct I'll need to visit a proper timber merhcants for this.



Router 25mm rounding bit - I can't find anything bigger than a 1/2" (12.5mm) rounder bit at the moment. I did look at quarter circle wood strip stuff, but that would just add another join, and was only in size upto 18mm.





I did however manage to get a few good things.



I picked up some M6 T-nuts for the driver fixing. These should be ok if I stick them in with something too. I've see insert nuts, but none of M6 size yet. Also need to find some good M6 botls with good looking hex/allan heads. I think CPC have them available. I've got some neoprene strip for using as a seal (about 8mm wide, and thickness compressing to about 2mm).



Also purchased some spray car paint in Fiat Broom Yellow and high gloss laquer, to test that I like the finish. I do like the Fiat/Ferrari bright yellow, so this should be good. So long as I can get a polished finish. Also bought some white International MDF Primer/sealer from B&Q.



Many thanks



PS: How are your current speakers going? I noticed them over at DIY.

[SYNTHesis]

25mm MDF - not in the large B&Q Warehouse, I susepct I'll need to visit a proper timber merhcants for this.




These folks do upto 50mm thick MDF, I had some of that from them to do a couple of plinths and its serious stuff. Its kinda expensive if you have it shipped to you because of the weight but all the stuff is CNC cut so is accurate.



http://www.cncrouting.co.uk/index.htm

http://www.shapes2size.co.uk/



But like you've said, your best bet is the local timber merchants. Here up north we have a chain of Lavers stores and these stock all MDF sizes upto 25mm. I'm sure you'll find something but if not 18mm is OK(I use this on all my projects) and just beef the bracing up somemore.



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Router 25mm rounding bit - I can't find anything bigger than a 1/2&quot; (12.5mm) rounder bit at the moment. I did look at quarter circle wood strip stuff, but that would just add another join, and was only in size upto 18mm.




Trend are the only people I really know of that do these large cutters. My local Jackson Building Center carries the full range of trend bits and they have a monster 40mm roundover but I would have serious doubts using that safely in anything other than a router table. The bits are also rather expensive but you get what you pay for and Trend are one of the respected bit manufacturers. My 18mm radius roundover cost me about £35 just for that one bit. I'd expect the 1&quot; to be slightly more expensive.



Best thing to do is call Trend up and get a part number off them and then order.



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Also purchased some spray car paint in Fiat Broom Yellow and high gloss laquer, to test that I like the finish. I do like the Fiat/Ferrari bright yellow, so this should be good. So long as I can get a polished finish. Also bought some white International MDF Primer/sealer from B&amp;Q.




Sorry to be the bearer of bad news but that International MDF primer is absolute junk. Sounds harsh but I used it and was disgusted with the finish.

The main problem is its waterbased and when you wet sand your cabinets after priming to get them smooth, the stuff just starts to come off and the water causes marks in the finish. Absolute junk. I'd imagine its even worse if your apply the stuff with a roller, sponge or brush.

Much, much better is simple automotive primer. This stuff sands beautifully, is high build and is sprayed on.



BTW If your going for a high gloss finish I also wrote a guide on doing that too:



http://www.diyaudio.com/forums/showthread.php?s=&amp;threadi (http://www.diyaudio.com/forums/showthread.php?s=&amp;threadid=83141&amp;highlight=high+gl oss) d=83141&amp;highlight=high+gloss



Using the techniques that outlined in that guide, you should have a reflection quality similar to or maybe even better if your prepared to spend more time and care:



http://img.villagephotos.com/p/2005-7/1050288/tism104.jpg



Be prepared for a fair amount of work but the end results are very rewarding.



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PS: How are your current speakers going? I noticed them over at DIY.




Pretty much at a stand still. Its the tempremental weather that we're having at the moment which is causing me problems. Really I need a few nice days back to back for the spraying.

[ReTrO]

More excellent help, thanking you very much.



I'm extremely tempted to get a quote for having the panels cut by the CNC chaps. Previously I was able to have them cut at a friends work (a furniture factory in High Wycombe) where has was the CNC programmer for a number of years. This was perfect for the parts for the RTP subs we made.

[SYNTHesis]

More excellent help, thanking you very much.




Nothing is too much trouble for a fellow DIY'er, so think nothing of it.



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I'm extremely tempted to get a quote for having the panels cut by the CNC chaps. Previously I was able to have them cut at a friends work (a furniture factory in High Wycombe) where has was the CNC programmer for a number of years. This was perfect for the parts for the RTP subs we made.




I know exactly what you mean. MDF is a pain to work with because of the dust and mess it causes. Half the time is spent cutting then the other half is spent hoovering the stuff up and having a shower!



I've recently started having my stuff cut to size or roughly to size by my local timber yard. That way I only have to cut the panels that they couldn't do, in this case that's anything that isn't sqaure or a rectangle. It saves much time and effort with the cleanup.



I'd certainly consider having my stuff all CNC cut but the problem for me is shipping MDF because of the weight and bulk of the stuff. Its also pretty fragile on the edges so special care must be taken to ensure it passes through the postal system unharmed. All this makes postage rather expensive - sometimes more expensive than the MDF itself!



If I could find a CNC cutter locally I'd jump all over it. Nothing like that exists after searching.

[ReTrO]

Regarding paints and laquers what are your recommendations?



The paint is restrictive due to the colour I'm after, which I have so far only seen in 300ml aerosol cans in Halfords, but this is a practice run purchase. The lacquer I purchased is a Halfords general one in I think a 500ml can, will this be up to the job?



For the recommended primer, would again the Halfords 'standard' canned stuff work ok?



Next question: driver fixing bolts, what have you used and where can you get them? Looking at M6 size for the subs.





I guess I need a cabinet to do the final finish on, so much work on that first really, but never better than being prepared.

I always try to remember the saying PPPPPP (Proper Planning Prevents ****-Poor Performance). :D~:-D~:grin:

[ReTrO]

Some more pics after design changes.



http://www.premierdivisionrugby.co.uk/avt/sub2_1.jpg



http://www.premierdivisionrugby.co.uk/avt/sub2_2.jpg



http://www.premierdivisionrugby.co.uk/avt/sub2_3.jpg

[SYNTHesis]

Regarding paints and laquers what are your recommendations?



The paint is restrictive due to the colour I'm after, which I have so far only seen in 300ml aerosol cans in Halfords, but this is a practice run purchase. The lacquer I purchased is a Halfords general one in I think a 500ml can, will this be up to the job?



For the recommended primer, would again the Halfords 'standard' canned stuff work ok?




The Halfords spray cans are probably the best around. Before I got the compressor and gun setup I tried Tetrosyl, Plasicote, Holts, Halfords and Upol branded spraycans over a period of a couple of years.

The Halfords stuff was best. I particularly like their grey primer. Which spraycans you go for, make sure your getting your primer, base and clearcoat all from the same one. Avoid mixing different types from different manufacturers as I've learned the hardway that this can lead to problems.



I'd estimate you'll need about 3-4 500ml cans to adequately cover cover a single enclosure and provide a coat thick enough to wet sand prior to applying the basecoat and clearcoat. When apply the primer hold the can fairly close to the work, say 10-15cm, so that you can get a fairly high build in each pass. Don't worry if you get a run because primer sands beautifully.



BTW After sanding the primer you should move immediately onto the basecoats and then straight that the clearcoats. These steps should be done on the same day if possible. I always get a *much* nicer finish doing it this way than if I leave for days between step.



With the basecoat you really only need to spray enough to get coverage on primer. This is usually 2-3 light coats with the can held about 15cm from the work. Avoid sanding your basecoat if possible and never sand the final coat of metallics.



You need a lot of clearcoat if your going to be doing highgloss. I'd suggest 5x 500ml cans for each enclosure. Build up plenty of coats over a long period. I start by spray each coat every 10 minutes and then slightly increase the time between each as more clear goes on. If your not that confident with spraying then lay down less more often and be sure to give a good amount of time between coats, these steps will definitely greatly reduce the chances of runs which are fatal on a high gloss finish, avoid those at all costs. Once you've done around 8 good coats you MUST leave the work for at least 2 weeks to allow the paint to harden and shrink, ideally a month really for the stuff out of spray cans. After that you can start doing the steps from that highgloss finishing guide I post above.



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Next question: driver fixing bolts, what have you used and where can you get them? Looking at M6 size for the subs.




I never bother with these, wood screws are all I use. I do think the hex head machine screws look more professional but the t-nuts can be a PITA to work with, especially on MDF.



However I recently found(scroll down a bit in the link) some self tapping hex head wood screws that look proffesional but don't carry the hassles of t-nuts. All you have to do with these is mark, tap and then screw in:



http://www.audiophonics.fr/monacor-divers-visserie-c-37_79_9 (http://www.audiophonics.fr/monacor-divers-visserie-c-37_79_96.html) 6.html



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I guess I need a cabinet to do the final finish on, so much work on that first really, but never better than being prepared.

I always try to remember the saying PPPPPP (Proper Planning Prevents ****-Poor Performance). :D~:-D~:grin:




I'd seriously consider spraying on or two 20x20cm MDF test pieces to get a feel for each finishing step and allow you to compensate or identify potential problem areas.

[SYNTHesis]

Some more pics after design changes.



http://www.premierdivisionrugby.co.uk/avt/sub2_1.jpg






Thats perfect now Richard. No nasty joints to spoil the highgloss finish :thumbup:

[ReTrO]

The screws that you have linked to I think can be purchased from CPC. I'm sure I've used them before on the RTP projects. This is guessing you definately don't mean the Trox headed ones, that I always like the look of. They remind me of the Imperial Starsign from Star Wars. :lol:



CPC Link:

http://cpc.farnell.com/jsp/search/browse.jsp?N=411+401+10030 (http://cpc.farnell.com/jsp/search/browse.jsp?N=411+401+1003052&amp;Ntk=gensearch_003&amp;Ntt =hex+head+screws&amp;Ntx=) 52&amp;Ntk=gensearch_003&amp;Ntt=hex+head+screws&amp;Ntx=



I'll do a trip to Halfords tomorrow for some primer and pop some pics up of what I then have to check you think it will work correctly together.



I managed to convert my Sketchup 3d drawing into DXF and sent it over to the CNC chaps, and am now awaiting a cost for material and cutting.



On a very happy note I'm getting one of those nice Makita 1/4 hand sanders for my birthday tomorrow, so that will make things easier. Just need to pickup some decent paper then. We have a shop called Issac Lord in High Wycombe that does all the tools and papers (albeit not the cheapest place) as I think part of the legacy of having had dozens of furniture (mainly chairs) makers/factories in the town.

[ReTrO]

Still need to confirm my choice of connector for the cables on the enclosure at some later date. Probably 2 pole Neutrik Speakon, but might just use binding posts if they can be air-tight enough.

[ReTrO]

Have just seen this Alesis RA500 power amp, and it appears to be preferable to the Behringer. Costs £145.00 all in from Digital Village DV247.com



250w into 4ohms per channel.



http://www.alesis.com/product.php?id=32

[SYNTHesis]

The screws that you have linked to I think can be purchased from CPC. I'm sure I've used them before on the RTP projects. This is guessing you definately don't mean the Trox headed ones, that I always like the look of. They remind me of the Imperial Starsign from Star Wars. :lol:




Thanks for that. I reckoned to have looked around the UK for some of those but couldn't find any! Saves having to ship from France :)~:-)~:smile:



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I managed to convert my Sketchup 3d drawing into DXF and sent it over to the CNC chaps, and am now awaiting a cost for material and cutting.




You'll have to let us know how much thats going to cost. I imagine it won't be cheap but the accuracy will be like nothing else judging by the equipment they list on their website.



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On a very happy note I'm getting one of those nice Makita 1/4 hand sanders for my birthday tomorrow, so that will make things easier. Just need to pickup some decent paper then. We have a shop called Issac Lord in High Wycombe that does all the tools and papers (albeit not the cheapest place) as I think part of the legacy of having had dozens of furniture (mainly chairs) makers/factories in the town.




That Makita sander is a good one, if its the same as the one I showed in that gloss finishing thread I posted earlier. Be sure to use quality paper such as the 3M ones. You can buy bulk packs or single sheets from Paints4u.com:



http://www.paints4u.com/ProductDetails.aspx?productID=6030



Remember to thoroughly read that gloss finishing thread I did because it really does work very well.

[ReTrO]

I have a Makita BO4335.



http://www.makitauk.com/index.php?page=36&amp;catid=21&amp;o (http://www.makitauk.com/index.php?page=36&amp;catid=21&amp;open=21#) pen=21#



I had a look at the papers in B&amp;Q, but they had nothing finer than 600 grit, and that they only had in a pack with 300 and something else.

[ReTrO]

Some pics of the paint I am using. Is sarted with 2 primer coats on the sample MDF this evening, but it got a bit cold, dark and damp to do anymore.



http://www.premierdivisionrugby.co.uk/avt/paint_cans.jpg

[SYNTHesis]

Some pics of the paint I am using. Is sarted with 2 primer coats on the sample MDF this evening, but it got a bit cold, dark and damp to do anymore.






Avoid spraying in anything but good weather and ensure the humidity level is lowish.



Its a bit rich me saying this because just two weeks ago I had to strip something down after the finish went bad due to spraying in less than ideal weather. I know the days I should and shouldn't be spraying on but I just impatient. Try to avoid that :D~:-D~:grin:

[ReTrO]

I'm the same. :lol:



I've left the primer to dry in the garage overnight and day, and will pop on another coat tonight, while it is still warm and dry.



I ordered up some papers (800 &amp; 2000) and the necessary polish etc. last night, so should arrive tomorrow.



I then need to finalise the enclosure design. Plenty of opinion on the DIYAudio forum, and I think the CNC route from the chaps you suggested may be out, which leaves me with a problem doing the large rounded edges. I may have to rethink that bit.



It'll still be high gloss Fiat Broom Yellow though. :D~:-D~:grin:

[ReTrO]

I've posted some new images of a redesigned enclosure on the DIYAudio forum.



My polishing bits and wet &amp; dry arrived today. :)~:-)~:smile:

[ReTrO]

No further updates yet due to the CEDIA Expo last week, and a new job starting in a weeks time. :D~:-D~:grin: