Vanagon – The “Swellegant” subwoofer

If your are sipping your coffee or any other beverage as you read this, please swallow what you have in your mouth and put the cup down. I’m not taking responsibility for any spit takes that might happen when you see what I made.

It started a couple of months ago when I was fooling around with some scrap aluminum and the TIG torch. I was adjusting the welding machine settings and rod size seeing what effect various changes had on welding outside corners. As I welded bits together I realized I could make a box of sorts and that would provide good practice on the seams. Well, i made the box, enclosed on 5 sides and I looked at it… what if I make it into a subwoofer enclosure?

3/16″ thick aluminum is not what springs to mind to use to make a speaker box, but what the heck eh? I had a pair of 12″ speakers in the garage, no idea what make, and I decided to use one as a sub. I added the 5th side to the box, actually pieced together from 4 bits, and cut a hole for the speaker. And why not four bits of tubing for legs? This was going to be a down firing sub. Oh and it was going to be a sub that paid very little attention to volumes, Q factors, etc, etc.

I drilled and tapped holes to screw the speaker to the box, than I made a grill from some 1/4″ square section material. The grill pleased me, stiffer than I expected. And just because I worried about how to secure the beast in the van, I welded on a couple of half moon bits to have something to attach a strap or something.

Ok, so it looked kinda bare. But I was recently given some leather so I thinks to myself “a leather pad thing on top would gussy it up some”. I cut a square of leather, a round of sleeping pad type foam, and some canvas as backing. I sewed it all together (and I found that difficult, only sewn a little bit of leather before and never saddle stitched) and attached it to the box with a leather thong.

And now it looks like some sort of industrial ottoman or commode. Go on, look at the pictures and laugh, I’m used to it now.

(Looking inside you might be able to see some dampening pads stuck on the walls)




Yes, the sides are curved. Same scrap material that I made the underbody protection plate  with.


Paper cone and still in one piece.


So how to power this thing? My head unit has 2 channel sub out jacks and I knew I had a spare amplifier in the workshop. An amp that was bridgeable so I could lead 2 channels in and have one channel (mono) out. I couldn’t find the damned amp, I searched high and low. Found all kinds of things (previous posts) but no amp. Good friend Stephen took pity on me and gave me an amp he had lying around. Nice old amp, a Blaupunkt 4 channel unit.


It was not bridgeable, but it excited me. The existing stereo set up in the van consisted of a Pioneer DEH-P5000 head unit feeding an Alphasonik PMA-2030 amp (not bad vintage amp) under the driver’s seat. That amp powered the front door speakers, Boston Acoustics Rally (model number forgotten) 6″ mid in lower part of door and tweeter up behind stock speaker grill. Oh and those are fed via some separate BA crossovers. Back in the rear overhead cabinet are a pair of 4″ pioneer speakers, powered directly from head unit.

I decided to pull the Alphasonik amp (not bridgeable) and use the Blaupunkt to power the front and the rear speakers. Was a little bit of a pain to do that, but I did manage to reduce the tangle of wires behind the dash (I can’t really fault the previous owners of the van, stereo installs seem to bring out the slipshod in all of us) and I squeezed the amp up on the crossmember behind the glove compartment.

That all worked well. When I say well I mean the stereo system still worked. But I don’t have my sub installed! Where the heck is that lost amp?

I found it the other day, not far from where it was supposed to be. It had fallen, or was placed (yeah, by me) in a box of fibreglass cloth and was covered by same. Callooh callay! I cried (no, I didn’t) when I found it. Some futzing and farting around and it was installed under the driver’s seat and finally my sub made noise. And what kind of noise? Well, a kind of thumping booming noise. It does pump out the bass, it does make things rattle, and once I fiddled with the sub woofer settings on the head unit (low pass and high pass filter adjustment) it sounded rather ok. I don’t think it is as tight or as controlled as a subwoofer should be, but considering everything about it, it is acceptable.

I have it connected to the amp via an RCA jack so it is easily disconnected and removed from the van. Right now it sits behind the passenger seat, but I can extend the cord and I might try other placements.

Oops, forgot, I made a quick sketch of the stereo system layout. Note the connections between head unit and both amps are via RCA jacked lines.

sound sysytem

  1. #1 by famillysyncroJerome on December 11, 2013 - 7:50 am

    You should add an adjustable tube vent for air to move in and out…. a little more on that when I’ll be back home.

    Nice job, I like it, nice welding.


    • #2 by famillysyncro on December 11, 2013 - 3:22 pm


      Here is the link for the vent/tube I was talking about:
      I think there is a need for your sub to “breathe” for better result.

      I really like it, the construction is really nice.

      Do you think you could make a set of “legs” that will match your exterior home made camping table and use the sub as a stool?

      Since you are loosing a lot of room with that empty space in the box, could you make 2 or 4 beer bottle holders at the top with enough room to add ice cube?
      You still can keep the leather pad on it when you are not using it as a beer cooler….

      Or, may be add a air/hydro cylinder to jack the van when you have a flat…… it will be strong enough I am sure….. 😉


      • #3 by albell on December 11, 2013 - 3:32 pm


        Ill look at the port/tube info but my limited knowledge about such things led me to think that with such a small enclosure volume a sealed box was best. But heck, obviously I know little about these things 🙂

        I can use it as a stool as is, it is not too low. I have a console between the front seat already so I havent tried fitting the sub in there. It would be a good spot especially with cup holders etc.

        BTW, it must weigh close to 20 lbs.

        In the end it was just a bit of fun. If i were serious Id see if I could get the other 12 speaker in the van. A removable box behind rear seat back holding 2 12 speakers?



      • #4 by famillysyncro on December 11, 2013 - 6:18 pm


        I knew about it because I made some speakers a long time ago for myself. Even only a vent will improve the air movement.

        Even for fun, I think it is a nice piece, you should keep it and use it.
        I’ll match you bumpers later….

        Are you seriously thinking about 2 12″ subs?


      • #5 by albell on December 11, 2013 - 6:22 pm


        I will consider the port. Today I moved the sub behind the rear seat and it sounded ok there, better for bass heavy music.

        I was only kidding about two subs. Too much space and work and would be in the way when camping.

        Btw, I still haven’t talked to you about engine vibes, I will get around to it soon.

        I hope to get the bumper finished, well at least mounted May not be painted, over Xmas. Spare tire carrier too.



      • #6 by famillysyncro on December 11, 2013 - 7:05 pm

        I’ll be happy to see those bumpers as well as the tire carrier, I am sure they will be nice.
        No hurry about engine vibs, I don’t think I’ll do too much with the cold and bad weather we have right know.
        And because of you, I am really busy with another project: I already got the TV support and the mini pc Android is ordered, usb power supply…… but from China so it might take a while.


      • #7 by albell on December 11, 2013 - 7:10 pm

        Im keen to see the outcome of the mini pc project. This could be a really good vanagon mod. Not just for entertainment, also for OBDII engine data display.


        PS Ill get cracking on the bumper

      • #8 by famillysyncro on December 12, 2013 - 3:58 pm

        Talking about bumper, did you see this mod, bottom of the post:
        I am following it, it is something I’d like to do. Not sure if I want to go as deep and “shim” the front subframe but I like the “front added frame” to connect the bumper…..

        The mini PC will be entertainement only as the G60 is a 91, no OBD but there was a little something integrated to the cluster (that I still have but not really planning to put it inside the van…) acting like a OBD.

        I still have so much to do inside the van (still waiting to add my battery monitoring system….) and may be work on the trans (idle gear leak) but I still need to work on the coolant system, got more leak when the temp went -30 as well as a fuel leak (I replaced the gas pressure regulator some time ago) and had to add 1 more turn on the clamp screw…. that was close.

        Anyway, the weather is too cold for now so all of that will wait.

        Have a good day Alistair.


  2. #9 by Pz on December 11, 2013 - 11:15 am

    Very nice aluminum sub box Alistair.
    Looks almost crush-proof.
    Very retro teutonic looking.
    Your welds sure look good… you dah man!


    • #10 by albell on December 11, 2013 - 11:41 am


      retro teutonic – I like it, mind if I use that in the product promotion literature ?


      It really is crush proof, very strong. I mentioned how surprised I was at the strength of the simple grill (1/4 stock, welded to a ring in the middle), I have to say it again – it is strong!



  3. #11 by pz on December 14, 2013 - 5:09 pm

    Sure, use my made-up lingo at will. Will drive Flder. Industries crazy trying to figure out your marketing guy….:-)
    I bet that subbox would hold up your Syncro without breaking a sweat…

    I’m no speaker guy but have read a book or two….
    With a small enclosure, a sealed box is one norm of design. AFAIK.
    Tuned ports can sound very good but usually demand significant cubic feet of enclosure.
    Your speaker is providing a frontal wave against the sealed air in the box.
    Some call this a half-wave enclosure. As the speaker is not allowed to fully respond to the
    full wave for the musical note mechanically.

    Reproducing clean bass is a mechanical nightmare.. Look at the air driven pipe organ..:-)

    • #12 by albell on December 14, 2013 - 5:36 pm


      That’s what I thought with the small volume enclosure. I don’t think I need any more bass that a port would give, but I do suspect my amp is working hard to move the cone.



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