(Topic ID: 148069)

TOM: Left speaker not working

By bhwolf

3 years ago

Topic Stats

  • 8 posts
  • 4 Pinsiders participating
  • Latest reply 3 years ago by markmon
  • No one calls this topic a favorite


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#1 3 years ago

Just noticed today that my left speaker doesn't seem to be working on Theatre of Magic -- all sound that I can hear is coming from the right speaker. Looking at the wiring, it's in parallel with the right speaker and connected at the terminals of the left speaker -- so, the signal must be good. It does look like the left speaker is more of a mid-range driver compared to the right speaker.

Are there any tests/maintenance I can do, or is it simply easier to replace the whole speaker?


#2 3 years ago

I ended up replacing mine. That left speaker driver was pretty cheap to begin with, it's not surprising it would break down eventually.

Some good info here:


#3 3 years ago

I know the modern Stern machines are mono, so as long as you have sound from the right speaker, its not electronics.
I would do as jsa said, just replace the speaker.
Truth be told, you could probably go to Radio Shack and get a replacement.

ebay.com link » 8 4 Ohm Woofer Speaker Used On Stern And Other Pinballs

#4 3 years ago

Be careful on how you do this. The board can handle a 4 ohm load. If it's wired in parallel then it is probably and 8 ohm speaker as the two 8 ohm speakers in parallel present a 4 ohm load. A typical car speaker is 4 ohms and would not be an ok swap without rewiring the set in series.

#5 3 years ago

Thanks all --

Markmon -- I pulled the speakers and both are labelled 4 ohm. They look original. I checked the right speaker and indeed it is 4 ohms, while the left speaker is open. Will check into replacements -- would be nice to get something decent but not really needing anything too high end.

#6 3 years ago

If they are both 4 ohm make sure they are wired in series not parallel. The last thing you want to do is out a bunch of extra strain on a very old board amp. Even if Williams wired this wrong at the factory now is the time to correct it. i have even Williams wired both ways.

#7 3 years ago

Thanks Markmon -- I purchased some Kicker 5 1/4" and 3 1/2" speakers to use as replacements (the factory 3 1/2" is working, but figured I'd match the speakers while I'm at it). Didn't want to expand the hole for 2x 5 1/4".

I get what you're saying about the 4 ohm speakers in parallel = 2 ohm equivalent, but the manual (pg 3-30) has it that way. I think it's safer, though, to wire them in series as you suggest. The 3 1/2" does have a capacitor on the + terminal, which might be why it's done that way to preserve the higher impedance. (?)

In any event, I think removing the cap with these speakers, rewiring in series seems the way to go. Seems like they were going after using the left for midrange and right for highs as if it were a single speaker.

#8 3 years ago

The cap does not change impedance. It is a high pass filter to prevent the right speaker from getting any bass.

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