Until recently, pinball machines came with lousy speakers.  It is pretty easy to replace them with the same size.   But an upgrade to a larger size brings big sound benefits. 

How to upgrade Williams / Bally WPC backbox speakers.

Supplies Needed

#18 or #16 Speaker Wire – Get the pure copper, not the copper clad wire.  #18 is great and easier to work with than #16.
8″ speaker 4 ohm – There are lots to choose from.  We installed this one in a Williams Indiana Jones.  
Note: make certain that there is enough clearance for the depth (height) of the speaker and the playfield. 
A Jig Saw – Or any hand saw will do, but we use a jig saw.  A table jig saw is even better.
Crimping supplies – You will need to make a new plug.  0.156″ Trifurcon is typically used. If using with a PinSound card, a 7 position plug, or a two position and a four position plug.
Wood Glue
Various Screws – We used 2 & 1/2″ #8 screws to hold the spacer back in place.
Drill and drillbits.

Optional – 8″ MDF / wood spacer – see ‘An Alternative’ box below.

Getting Started

Power off and unplug.  

Take out the pinballs and lift the playfield, setting it back against the backbox.

Unplug, or unsolder the speaker wire (or just cut it) and remove the speaker.

 

Take off the grill and set it aside for use later.

Remove the Spacer

An alternative:   Spacer rings are available which can substitute for this wooden spacer.  They have the advantage of being cut perfectly for size. We don’t use the plastic ones.  The plastic tends to acoustically isolate this woofer from the cabinet.  For best effect, the speaker needs to use the cabinet as a transmitter of sound, not be isolated from it. If you can find a wooden spacer (MDF), that would work.  But then you will need longer screws to go from the bottom of the cabinet through the spacer and hold on the speaker.   If you do this, you could leave the original spacer in place.  But you would need to securely attach the speaker through the MDF spacer and to the cabinet.   This speaker is heavy.  You don’t want it flying off the bottom of the cabinet while the pinball machine is being moved.

Using a screwdriver, or similar, find the spot where the spacer is attached to the bottom of the cabinet.  We do this on the interior (hole) but the outside might work too.  

Go around the hole and just tap in the screwdriver.  Don’t try to lift it all at once.

 

Carefully work to remove the spacer.  It will eventually lift up from the cabinet.  

Tap out any remaining nails and remove them from the insert.  Throw these away.

Tap out the screws that held the speaker in place.  Save these.

Modify the Spacer

That existing spacer needs to be cut to the size of the new 8″ speaker.  

Once the nails and screws have been removed, trace the 8″ speaker circle on the wood spacer, centered on the existing hole.   Some speakers come with an insert for cutting a circle.  Ours did not.  But the cardboard packaging material made a perfect right-sized circle for tracing. 

 

 

After tracing the line on the existing spacer, cut along the lines.  We used a jigsaw – a table jigsaw.

 

 

 

After it is cut, set the speaker on the spacer, make sure it is centered in the hole, then mark four marks in the speaker ring for the screws.
Hold the speaker in place with the wire connections where you want them. Pick holes aimed at the four corners.   Note the position of the wire terminals and Mark That Side of the Spacer!

Drill the holes.  Pick a drill size so that these screws can pass through but remain held in place.  We used a 9/64″ drill bit (~3.5mm).

Insert the screws and test the fit for the speaker with the wire terminals in the same direction.  Carefully align the speaker over the speaker holding screws before lowering into place so that a screw does not go through the speaker cone.

Originally, the spacer was glued and nailed into place.  With the heavier speaker, we want to securely glue and machine screw the speaker into place.

Place the insert in the cabinet (without the speaker) with the side marked for the wire terminals pointing the correct way (typically to the left or back). Center it in the existing hole.

 

We used #8 x 1.5” machine screws for  this step. Drill the appropriate size hole through the spacer and cabinet in one corner.  Insert a screw  and washer from below and through the spacer (have someone hold the spacer).  Lightly tighten down screw and washer. 

Check that the spacer remains centered. Repeat this for the opposite corner.  

With the spacer securely in place, repeat for the two remaining corners.  Check fit, location and that the screws remain in place.  Note marked side of spacer.

Remove the nuts, washers and spacer, leaving the screws in place.

Center the screen in place.

Note:  In a perfect world, the cabinet hole would be routed out to the same size.  This is not necessary here.

Apply wood glue to the bottom of the spacer.  With an assistant helping below, place the spacer (marked side correctly aimed) over the screen and securely tighten it down with the washers and nuts. 

Carefully align the speaker over the speaker holding screws before lowering into place so that a screw does not go through the speaker cone.

Aim the speaker wire connections where you want them, and carefully lower the speaker over the screws – align all four screws before lowering. 

Tighten the new speaker into place.   Wire up and enjoy!

The original speaker is included in this photo to show the difference in quality and size.