I have the new sound chip and speaker system installed. And it's fantastic. It really brings the pack to life. I'll try to detail a bit of what I did.
You can check out the result here:
First, I removed the existing fan I had in the center circular vent to make room for the speaker, because the fan noise will now be through the chip.
The audio files were given to me by Jason Ehl. A tremendously helpful guy. He built a similar system in his pack and had already sourced the appropriate start up, thrust and fan wind-down sound files.
I then passed the audio files on to Rob at replicaprops.com. Again, an incredibly helpful guy. He programmed the sound chip for me. I could not believe how affordable and convenient this product is. The sounds I set him are now a standard option for others to buy on his site.
The wiring of the chip, speaker and lights was not trivial. It required two battery packs (the chip runs on 3V, the lights on 12V). I also had to track down the appropriate DPDT momentary pushbutton switch. Here's the switch you want:
MB2061SB1W01-DA-RO NKK Switches | Mouser
You can install this with or without an additional amp. This is the amp to buy:
7 WATT MONO AMP
Mine's on order, but honestly, it's quite audible without it. But hey, louder is better, right?
I've attached two wiring diagram options, with and without the amp. The additional switch for the amp version is so that you can kill power to the amp when not using it or it will draw power out of your batteries.
I'm tremendously happy with the result! Finally. I think my Cirrus X-3 is complete
Again, I want to thank Jason Ehl and Rob from replicaprops.com. I could not have done this step without the help of these guys.