Lupin ~ Royal Road [by Olympia] Pachislo volume

[jpee30]

Dear Pachi members,

Hopefully some of you can give me some advice for the Lupin - Royal Road Pachislo.
I searched quite a bit already on the forum on volume controls and I already build some in my Pachinko machines.
But I couldn't find that much dedicated info on "newer" Pachislos. (also it's my first Pachislo, so I'm exploring a bit)

Pachislo in question is in the title and made by Olympia:

Lupin_Royal_Road_001.jpg

I think it has 2 speakers in the bottom and 2 in the top and apart from that a big one (subwoofer?) next to the rolls.
Lupin_Royal_Road_005.jpg
It already came with volume controls (see picture 002 for bottom controls and 004 for top controls) in the bottom and top front door panels.
Lupin_Royal_Road_002.jpgLupin_Royal_Road_004.jpg


While testing/playing everything is fine until I hit a certain chance/reach: then all hell breaks loose and I get blasted by speaker volume that is high enough to make the whole machine vibrate.
I have a feeling that the big speaker in the top does not have volume controls yet and is only active at specific times.

1. Does any of you have a similar type of Pachislo and is can confirm there are 5 speakers?
2. If so: could someone point me or give some tips to find out which cables. (I think it should be possible to pull out that rear speaker)

Any help/suggestion is appreciated.

Apart from that an additional question (see fig. 006 and 007)
Lupin_Royal_Road_006.jpgLupin_Royal_Road_007.jpg
To the right of the hopper is some sort of plastic tray that I can pull out (beneath it is a hole in the Pachislo case).
On top of the tray is some sort of lid which has some cables connected to it. --> is this something purely used at a parlor?

Thank you in advance.