I thought I would share a few pictures of my museum-quality "Time Machine". I bought this game just for the tunes. To enhance the quality I replaced the backbox speakers with Pyle coaxial speakers. I replaced the mid-range with a Pyle 8" sub-woofer. I had an on-board amplifier but to reduce weight I moved it externally. All speaker wire was replaced with shielded 16-gauge cable. The speakers have low pass and high pass filters where appropriate. A sub-woofer needs an enclosure to operate correctly. There are formulas to determine the ideal size. Dickinson's cookbook on speaker design was helpful, hence the added enclosure. Now she rocks!

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There's really not a whole lot to say. I picked the brain of The Korn in Illinois about speaker theory. I don't believe the on-board audio amplifier has enough oomph to drive an 8" or 10" sub-woofer adequately so I chose to use an auxiliary amplifier. I started with an AudioSource model because it is 120VAC. If you look at the second picture you will see I have two control boxes. I plugged the amp. into the second box. I am now going with an external power supply/12VDC car audio amplifier because they have more power. Looking at the second picture again you will notice the Neutrik (made in Switzerland) connectors. They are rated for supply power and feature twist-lok design. Theory suggests that if you hold up a tweeter in mid-air you will hear sound. If you do it for a mid-range speaker, likewise; however, if you hold up a bare sub-woofer you won't hear anything. You need an enclosure. The bottom pinball cabinet is your enclosure. Ideally it is too big but it will work. My enclosure is ideal for my operating parameters. No speaker can reproduce the dynamic range of the human ear. That is why we have the four styles to work in concert to cover the range. We can take this one step further and design a system where certain frequency ranges are prevented from being introduced to a given speaker. Example, we don't want high frequencies going to the sub-woofer. So we introduce a device called a low-pass crossover before the sub that allows only frequencies below 250 Hz (you can pick any number you want) to enter the speaker. Then we do the same thing for the backbox speakers - all frequencies above 250 Hz are permitted to pass. This makes the speaker more efficient, not to mention clearer, because it is not force to reproduce those sounds. The other unresolved question is whether you want these filters before or after the amplifier. The shielded cable was employed to help with noise abatement. I bought everything at Parts_Express.com. They are just up the road about 40 minutes. That's all I got.

Dickinson's formulas for determining the enclosure are based on volumes. I used an 8" sub-woofer. The only constraint is the height - you have to clear the underside of the playfield. The four sides are mounted directly to the floor of the bottom cabinet. I used 3/4" thick poplar for the sides and lid. The dimensions are external. The assembled height is 7-13/16". The width or going from side to side while facing the machine is exactly 12". The dimension from say coinbox towards the backbox is 11-1/8".

Standard factory issue is a chrome on plastic speaker grille. There was no optional black model. I have seen a lot of disfigured chrome examples over the years. I would guess someone had one of those and painted it.