Project – Subwoofer

Come on, Feel the Noise

Be it listening to Brahms, Biggie, Bootsy, or The B52’s, that feeling when those bass notes are hit can often be indescribable. ‘WHOA!’ usually sums up this glorious effect as sub 20’s frequencies boom through your eardrums, resonate into your bones, finally rattling you off your barstool. What a feeling!

And yes, feeling is oh so important.

Sound & Vision

And watching movies isn’t just about simply watching them. As an actor it didn’t take long to realize the importance of relationships and what it is to really listen. Being present. Being authentic. Connection is so important. Someone could be in front of you or on the screen – its no different. You still feel.

We get sucked in. Immersed. We relate to their struggles, their anguish. The broken dreams and abandoned hopes. We join their mighty quests and guilty pleasures, heroic battles and brave adventures. We are there. Walking with them, as they sprint away or leap fearlessly into war. Laughing, crying and shouting at the screen.

A system designed to shake the ground beneath, I believe essential to garnering what can only be the closest thing to an out of body experience. Bass lines and bass drums sound like monsters, plodding mercilessly to their prey. They get noticed. They get felt. The make you feel something more.

Words make us listen. Behavior makes us notice. Sound shapes the moment.

The Brief

Create a subwoofer producing balance and harmony, lining the wayward cacophony with deep tones of authority. Aesthetics were also important. Colors and textures to compliment the décor of my living room. All this incorporated a need to design and build using reasonable dimensions plus finding the optimum position for best results.

In terms of the build I opted for a closed, non-ported box design, based on the correct cubic feet for the sub box. As a result, I chose a 10” subwoofer mounted in a down firing position. This was done for aesthetic reasons and as a result the difference in performance would be negligible.

Materials

  • 15mm 1220 x 2440 standard MDF
  • 9mm 1220 x 2440 standard MDF
  • Wood glue
  • Rubber Feet
  • Paint
  • LED lights
  • Glitter paper

Components

  • 10” subwoofer driver
  • cable to connect driver to amplifier terminals
  • spade connectors for terminal points
  • plate amplifier
  • Fiber stuffing

 The Tools

  • Makita Cordless circular saw
  • Makita Cordless jigsaw
  • DeWalt plunge router
  • Makita trimmer
  • DeWalt Cordless screwdriver
  • FESTool orbital sander
  • Makita dust blower
  • Coping saw

Build  Process

Part 1 – Inner shell cuts

My design comprised of a double skinned box made from 15mm MDF (inner shell and 9mm MDF outer shell).

Strength was essential. Because of this, the inner shell would need to be strong enough to 1) hold the components and 2) sustain a consistent low frequency thrashing.

Similarly, the resulting design of the outer shell would also require a certain level of strength but easy enough to manipulate hence the reduced thickness.

  1. First up – the circular saw with guide rail to cut the inner and outer MDF sheets to their correct sizes. Dimensions for the inner shell had to conform correctly in relation the sub spec. This info can should be provided by the manufacturer. Essential was the cubic feet number for designing the enclosure. Some excellent resources provide this information along with calculators to help your design.

  2. All pieces except the back and base squares from the inner shell were cast aside for the time being.

  3. Next up – the trimmer! We used this attached to an MDF jig to mark the circumference then cut the speaker hole. I measured the radius of the hole and set this to the up with the furthest point of the trimmer blade then proceeded to make the speaker hole in this square. It took around 20 minutes to setup and complete the cutout. I was conscious of not to trying to remove too much material per pass. For 15mm MDF it can take around 5-10 passes to get a clean cut.

  4. I removed the trimmer from the jig then replaced with a different cutting tool. A chamfered edge bit would allow the speaker to recess nicely into the hole and have enough play for the screws to fix into. I chamfered about 3mm (the thickness of the speaker flange).

  5. I cut a hole into the back of the plate amp square then jig-sawed out the excess material.

  6. I then brought back the outer shell square and placed on top of the inner plate amp square and used this as a stencil to drew around. I then cut a hole using the same process as above. Again, I used the trimmer to chamfer the material on the outer shell allowing the plate amp to recess nicely into the groove. I used another jig to achieve this. I then placed this to one side.

  7. I brought back the all the inner shell squares and fixed them together using wood glue. These were clamped and left to set over night.

This comprised of:

  • Solid top/front/left/right faces
  • Hollowed out base face, for the driver
  • Hollowed out back face, for the plate amp

Part 2 – Outer Shell Design & Install

  1. Based on my chosen design, the London Skyline I took the left and front squares from the outer shell pieces and put the rest aside
  2. I created two stencils for the skyline buildings I wanted included and ran this across the two square of the outer shell. Placing them adjacently I fixed the stencil, drew around them then cut out the shape. I completed a rough cut with the jigsaw then more precisely with the coping saw.

I then used fine sand paper to remove the burrs and rough edges as best I could.

This portion took around 3 hours to complete.

  1. I brought all the outer shell pieces together, arranged them into a box before gluing and clamping them. They were left to set overnight.
  1. The next day I started working with the inner shell. I sanded all edges and faces removing excess glue and other debris. This ensured the outer shell would fit over it without getting stuck or not sitting flush.
  1. I cut the glitter paper to size and glued this to the two faces of the inner shell. The two faces of the outer shell would eventually be places on top of these.

These was put aside and left to dry.

  1. I repeated the sanding of the faces and edges with the outer shell, removing glue and debris. I decided to give the top face a detail so used the trimmer to give me a chamfered detail along all the edges.
  1. I used the blower to remove additional debris form the inside of the boxes as it was time to put the first coat of primer onto the outer shell.
  1. Once the outer shell was painted – 2 coats of primer and 3 coats of eggshell gloss we carefully positioned this over the inner shell. We were extremely careful not to take the glitter paper off whilst lowering it into place. Tricky but successful we managed to sit it snugly without too much swearing.

Part 3 – Fitting the Components

Now the shell portion was complete all we filled the box with the appropriate amount of fiber filling ten fixed the driver into the box We used a manual screw driver to accurately apply the pressure. I’ve slipped and driven straight into the speaker cone and certainly didn’t want a repeat of that.

Once that was safely fitted I wire up the connectors to the plate amp then fixed to the back face of the completed box.

One final touch was adding an LED light to the base of the box.

The moment of truth came.

The Test

After connecting this to my A/V system I needed a good selection of sounds to whet my appetite.
I didnt just want to hear thumping bass or thudding kick drums but a feel the overall tones as best I could across the range.
The sub was built to support the existing speakers and provide harmony to the listener, not just destroy the eardrums and cause panic in the house next door.

From my music collection I selected a eclectic mix of records that did test the range.

Music

Primus - Pork Soda
Korn - Life is Peachy
Holst - The Planets
Andy C - Nightlife
Kate Bush - Never Forever

Film

What Did I get?

A very loud, very warm and extremely capable subwoofer that not only produces a great sub sound in the 20-200Hz range but also looks great.
Its hooked up to a Sony AV receiver thats 120W per channel so plenty loud for a smallish living room.
The plate amp allows me to adjust and shape the tone and frequency, which compliments the other speakers beautifully.

My next task is to build some new shelf speakers but will enjoy the vibes from this beast for a while…!