NIce job on the cab looks great!
I have one general question. How do you hook up car speakers and PC speaker to the Sound card? I was just gonna buy some computer speakers and gut them. I saw your pic said speaker hack but no detail on what it is, or how its done.
Thanks
Thanks ...
Regarding your question here's wha I did:

On the "Speaker hack" picture you can see the controls, the amplifier and three connections. These connections are:
The red and black wires that are connected to the speaker - I remove them from the plate and solder in place one of the wires from the auto speakers (left);
The above double grey wire is the connection for the other speaker - I did the same for the other car speaker (right);
The last grey wire is power - Just put a longer cable;
This works only for self powered speakers (like this ones). If not, the signal is so weak that you'll won't be able to ear almost nothing.
The center speaker on the cab is fake ... it is only used for supporting the plate ...

So actually I did not use car and PC speakers at the same time ... I replaced the PC speakers with the car ones ... but if your amplifier has enought power, you can connect two rights and two lefts with no problem what so ever ...
Hope I was clear ... it's kinda dificult to explain this sort of things without using the hands ...

but if there's anything else you require let me know ...
**** Edited
Opps ... forgot the main issue ...

... there's also a connection from the plate to the sound board using a 3,5" jack ... it's not yet soldered to the plate, on this picture ...
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Regards,