How to give your WPC pinball machine more bass

In home use the music and sounds of a pinball machine are much more important than when it's on location. There it's usually turned down or there's too much background noise to really appreciate the sound quality.
At home this changes, usually it's quiet - especially when you have a dedicated gameroom and only play one machine - and then sounds matter a lot.

Unfortunately pinball manufacturers don't care a lot about sound quality and they use the cheapest speakers available.
You can buy speaker upgrades, some shops sell new speakers with all wires and connectors already made up, so it's just a plug and play job.

It's not so difficult however to upgrade your own speakers and do a better/cheaper job. If you want a detailed guide then check Joseph Dziedzic website, it describes in detail the best way to improve the sound.

For an easy and quick improvement, just go to a shop that specialises in car speakers and get new ones. Just the same size, but quality speakers, will make a huge difference.

A lot of speakers, some are much bigger.

If you want to install a larger bass speaker in the cabinet, it is best to cut out the hole to adjust for the larger size.
Leaving the default hole will reduce a lot of the sound.

Some people really want a lot of bass and sound volume. When decibels are all that matters for you, then install an extra amplifier in the cabinet. Car amplifiers will do. It's safest not to use power from the pin, but add a new powersupply and hook it up to i.e. the service plug.

I have not installed an extra amplifier. There is however one small trick that you can do on pinball machines that will improve the sound quality. Just one small resistor can be enough, change the value of R17 on the audio-video board on WPC-95, or on R39 on the older soundboard A-16917 (WPC).
This resistor influences the balance between the backbox speakers and cabinet speaker. What we want to achieve is reduce the backbox speakers. When you increase the level of the sound, the bass from the cabinet will come out more.

The potentiometer installed over R17 on a WPC-95 a/v board.

I use a potentiometer instead of a resistor, that way you can adjust the sound like you want. As you can see I use alligator clips to clip it over R17. By default it is a 22k ohm resistor. When you go lower (so buy a potmeter that goes up to 20k ohm) you'll give the sound more bass. It's safest to use a dmm when adjusting it - do not turn it all the way to 0 ohm because that can give some problems ! On my Attack from Mars I've installed it on 9k ohm, this gave the best results. It's a small upgrade, but in combination with new speakers this will make a big improvement in how to pinball machine sounds and even feels (as you feel the vibrations in the cabinet).