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April 27, 2016 Comments (0) Club Plus, Club Plus Projects

DIY Evo Custom Subwoofer Enclosure

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I’m Stephen, a Club Plus member and I enjoy doing DIY projects on my Mitsubishi Evolution 6. I created my own removable subwoofer box utilising MDF sourced from an old table top!

Sub Box

I have no formal training in DIY projects such as these. I just do a lot of research, use a lot of imagination and hopefully don’t go through too much trial and error. Previous items that I have customised on this car include cold air induction using an old circular light fitting, a spark plug cover using the bottom of an old flyscreen door and a rear diffuser using an old fish tank as a mold.

Recently I have started experimenting with DIY carbon fibre parts including 1 piece wheel caps with holographic faces and a complete custom front lip. In the future I plan to make custom LED tail lights and make a carbon fibre intercooler pipe. Here’s a photo of my car…

Evo

My Mitsubishi Evolution 6


Specifications:

  • Project time – approximately 100 hours
  • Box internal volume – 1.5 cubic feet
  • Box weight 16kg
  • 12″ Alpine Type X subwoofer – custom metallic gold painted by myself.
  • Alpine 1000 WRMS subwoofer amplifier and Audiosystem 380 WRMS front stage amplifier
  • Enclosure lined with macro suede

Tools used:


Basic Step by step guide:

My previous subwoofer install was a box that was permanently fixed in the boot. This limited the usefulness of the boot. For this reason this box is built over the spare wheel and keeps the vehicle’s original emergency equipment intact. It is easily removable although the box and subwoofer weigh almost 30kg!

Amplifiers are flanked at both sides of the boot to maximise usable boot space. Installed is also custom LED lighting with remote control flash sequence and other LED lighting that flash to the beat of the music and strobes that give the appearance subwoofer is rotating left and right.

Sub before and after
1. I determined how much internal box volume was needed according to the specifications of my subwoofer. In my case I went for larger than recommended specs – 1.5 cubic feet = 42 litres of volume.

2. I placed pine slats around the spare wheel in a trapezoidal shape to form sides of the box.

3. I covered spare wheel well with a large impermeable plastic bag to form a base, overlapping with the slats.

4. I filled the area with the 42 litres of water and floated a piece of cardboard on top. This allowed me to mark the level at which the baffle would sit. I adjusted the slats accordingly to bring the level with the top of the trapezoid. I drained the water out.

5. I allowed the plastic bag to dry, and then I placed the trapezoid over it before lining the plastic bag with aluminium foil to allow easier release of the fibreglass when it was added.

6. I mixed polyester resin according to its instructions and placed fibreglass mat over the aluminium foil and along the internal surface of the trapezoid. I proceeded to add resin to the mat.

7. When the resin had cured I carefully removed the “bowl” structure from the car to allow easier work on the construction of the bowl.

Adding ribs or otherwise changing direction that the fibreglass runs is a great way to strengthen the fibreglass base without adding lots of layers.

8. I proceeded to add 3 or 4 more layers of fibreglass to the bowl. The base was deemed as sufficiently strong when I could stand on it while it was inverted.

If there is a long delay between layering fibreglass it is best to sand the surface to give the new layer some more grip.

9. I then added a series of dowels positioned vertically from the base of the bowl to the top of the height of the trapezoid. These dowels would connect with the baffle to be added later. These dowels reduce flex of the box when the subwoofer is in action. This leads to better bass response.

Sub Box

10. I test fitted the bowl in the car then used traced around the outline of the trapezoid to form the baffle.

11. I cut the baffle and temporarily screwed it to the trapezoid and ensured I could put it in and take it out of the boot easily.

12. I removed the baffle and added glue to the top of the dowels and top edge of the trapezoid before securing the baffle on with screws 100mm apart.

13. I test positioned the subwoofer on the baffle before cutting the hole. The screw holes are very close the edge of the subwoofer cone so the cut for the hole must be very accurate.

Sub Box

14. I reached in through the newly cut subwoofer hole to seal the corner between the trapezoid and baffle with silicone. This was to ensure the box was air tight.

15. I screwed the subwoofer down to the baffle.

16. I constructed amp racks on both sides of the boot. These racks also served the purpose of keeping the subwoofer box in place by resisting lateral movement against the trapezoid.

Sub Box

17. I wired the subwoofer to the amplifier. At the same time I added various LED lighting. I ran a separate power wire for the LED lighting directly via a fused cable from the battery positive terminal. I placed a switch in the boot to turn the lights on and off when required.

Sub Box

18. I used cardboard to make a template for the baffle dressing plate before making the plate from 3mm MDF.

Sub Box

19. I covered the dressing plate with macro suede using contact cement.

Sub Box

20. All that was left was the best part – testing the system out and listening to sweet music.

Sub Box

Sub Box

TIPS:

  • When working with fibreglass always use PPE which should include gloves, goggles and respirator mask.
  • If there is a long delay between layering fibreglass it is best to sand the surface to give the new layer some more grip.
  • Adding ribs or otherwise changing direction that the fibreglass runs is a great way to strengthen the fibreglass base without adding lots of layers.

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