Vision machine - only bonus game makes sound from stereo speakers - normal?

[Lee123]

We just bought 2 slot machines for our home.  One is a standard S2000 Triple Diamond.  All the sounds from that come out all 3 speakers, the 2 small ones on the upper sides and the 1 larger one in the coin tray.  The other machine is a Vision "Bonus Spins Diamond Fives".  At first I thought the upper speakers were disconnected on it, because all the normal game sounds only come out the speaker in the coin tray. That results in sound quality that's not near as good as our other machine.  In fact, I called the dealer and have an appointment for someone to come out and look at it Tuesday.  Then I got the bonus game and all the sound from that came out the upper speakers in very obvious stereo.  Makes it pretty clear the upper speakers are working.  Before I call the shop and cancel my appointment, I want to find out if this is normal behavior for a Vision machine.  Should the normal sounds for playing credits, spinning reels, etc. come out of all 3 speakers, or are the upper ones reserved for the bonus game?  Thanks for your time.