Well after having connected one of my bass cabs up in place of the stock sub in STTNG with great success I decided to do the standard replacement thing with aftermarket speaker. The bass cab, and Eden 215XL sounded like it was made for this task. Alas, the cab was needed for bass playing duties (never mind the fact it was a little impractical due to it's size.
Disclaimer- I don't care what brand or quality sub you fit to a pinball cabinet- without a tuned enclosure for the sub it will either sound crap or never reach it's full potential.
Off to Jaycar I go to get a $40 Repsonse brand 8" 8 ohm paper cone sub and also a set of Response $29 5" speakers for the headbox.
First order of the day was to remove the old sub and it's mounting bracket.
Next cut a larger aperture for the sub and do the same to the bottom of the cab.
Screw in the sub and Bob's your uncle.
Now, when I tested I found the volume of the sub was not cutting the mix. Bugger, tried the 250K pot across R22 with not much difference. Hmm, up here for thinking, down stairs for dancing methinks. The head speakers it turns out are 2* 4 ohm crappers wired in parallel presenting an effective load of 2 ohms to the amp. That's a bit dodge I reckon - not many amps can push a 2 ohm load all day without whinging. I wire these in series for an 8 ohm load but still not quite good enough. Next the beer kicks in and I decide to connect the old sub in parallel so I present a 4 ohm load to this channel.
The level is almost there but without a tuned enclosure it just sounds muddy. A pinball cabinet is not a tuned enclosure and I don't give a stuff if you use the "speaker upgrade kits" from the dealers and do it like me with well priced parts. The sound is going to suck.
Win ISD I hear you say? Well that's a great idea! I'm off to design and build an enclosure and this will markedly improve the sound. I'll post the dimensions of what I cam up with and the frequency response curves and sensitivity data when done.