While thinking about how to get better sound from my vehicles, it occurred to me that if I could transmit the sound out of a tank wirelessly to a subwoofer, while still using the onboard tank speaker, then those non-directional low frequencies would 'fill the room' while the more directional mids & highs will seem to come from the tank speaker, giving correct location cues to my ears while the tank moves around. Here's how - make a 'series' speaker loop with 1 male & 2 female '2-pin' connections: one for the regular speaker & one for the feed to the transmitter. This will allow both to be connected to the single speaker terminal on your board (using the 1 male plug)... since you wire it in series, there's no danger of blowing your board's amp, as long as you are careful to not short positive to negative. Now, feed the speaker signal from the board to a "speaker-to-line level" converter (which is passive so doesn't need any power) to drop it down to line level, and then feed into the line input on your transmitter. Next, connect the line out of your receiver to a small battery-powered headphone amp, and the output of that to your subwoofer. If the sub is passive, then the level will be controlled from the headphone amp, and if the sub is active, then you will also be able to adjust volume at the sub & will probably have more volume. Very important to use these two level converters with the wireless gear, since it will sound like hot garbage if the impedances are mismatched. Notice that I used the 'line in' instead of the 'mic in' and the 'line out' instead of the 'headphone out' for the cleanest distortion-free sound. Very important to use analog wireless gear for this, since any digital gear will have a built-in delay due to the necessary encoding / decoding of the audio, and that could / would drive you nuts! Pictured here is all the sound gear required: the 2 units on the left are on the receiving end, while the 2 units on the right should fit into a 1/16 tank... but maybe you'll have to remove the smoker
See video link at end of this post for audible example.
This twin-speaker Tiger (on the blocks for repairs) will be getting the 'sonic implant' soon:
Here's a short video with the subwoofer being turned up on 'tank-in-a-box' bench tester while its internal speaker still plays:
https://www.dropbox.com/scl/fi/g00e0pzv ... tqhj5&dl=0
(I never used one, even in big lecture halls. My big mouth sufficed. 
) I have a commonly-available speaker that connects to my iPhone via Bluetooth. Would there be a gizmo (the technical term) that could transmit sound from the tank via bluetooth, or is that too expensive and complicated?