Drive in movie speaker via bluetooth and mini amp
The amp company through a very broken English email is telling me that the speakers are not large enough and it backed up the amp and overheated it.

That's baloney. As long as the speaker resistance is greater than or equal to the minimum load the amplifier can handle the amplifier will not be damaged. Typically those amplifiers can drive down to 4 Ω. If you confirmed that by measurement then that should be OK. The &quot;40V&quot; stamped on the rear is strange so I don't know what that means.

That may be true but the amp was only on for less than 15 minutes and it was not hot when I went to see what was up with it.




simulate this circuit &ndash; Schematic created using CircuitLab
Figure 1. Connecting equal resistances in parallel halves the resistance. Connecting them in series doubles the resistance.
That seems as though the load resistance is too low. If you connected the speakers in parallel on one channel then you have provided a load of only 2 Ω and this could be the problem. Instead you should have connected them in series.
The problem is further compounded by the speakers' own volume controls. We need a photo to debug that further.

Your new photo shows that the speaker volume control is a series-connected variable resistor. The problem now is that if we series connect both speakers the volume controls will interact. (One customer increasing the resistance on their speaker will increase the resistance on the series circuit, reduce the current and reduce the volume.)



simulate this circuit
Figure 2. A recommended wiring scheme.
The wiring of Figure 2 solves a couple of problems.

The circuits are independent.
Adding the series 10 Ω resistor ensures that you never overload the amplifier and also reduces the risk of damaging the speakers if the amplifier volume is cranked up. Any value &gt; 4 Ω will work here. You should choose a wire-wound resistor type with a power rating (watts) of several watts - 10 W would be safe enough and readily available.

One more thing: if your audio source is stereo and you only use one channel you will miss anything that is on the other side of the audio panorama. The solution to this is to bridge out the left and right channels of your 3.5 mm stereo lead. Ideally you would mix them with a few more 1/4 W resistors as shown in Figure 3.



simulate this circuit
Figure 3. A simple resistor mixer to convert stereo to monaural (mono).