Radio Quaderno: Modifications on a LS-166/U military loudspeaker

I bought a LS-166/U military loudspeaker in good general conditions recently. According to labels on it, my LS-166/U was made in Italy by LA.RI.MA.R.T., in Rome.
I bought the LS-166/U with the aim of adapting it as the external loudspeaker for my russian R-326 military receiver.

As you may well know, the R-326 (or P-326 according to the russian alphabet) is a nice small receiver, which can operate both from batteries and from AC mains (by means of its power supply). It started to be produced in early '60s. It employs 19 miniature tubes and requires only about 1.5A at 2.5V to operate, which is surprisingly a low power requirement for a tube receiver of its complexity.

More on this receiver at following links:
Russian Receiver R-326
Soviet Era Radio: Dennis reviews the Shoroh R-326 receiver
The R326 Receiver

The R-326 receiver (from http://air-radiorama.blogspot.com)

The R-326 does not feature an internal speaker. It has a 600 ohms audio output, in the form of a bipolar socket in the lower part of the front panel, that can be used for connecting both heaphones and a 600 ohms external speaker.
Let me say that the original, heavy duty, military headphones that came with my R-326 are not the best you could desire in terms of comfort. So I started to think about how to connect more modern, light and comfortable low-impedance headphones to the radio. First, I looked around for a 600 ohms to 8 ohms transformer to build a simple impendance and connector adapter, then I thought that it could be nice sometimes to have a chance to listen to the radio by an external loudspeaker, possibily a military one. The LS-166/U appeared to be well suitable for my purposes: 600 ohms input impedance, an internal impedance transformer with 8 ohms output, a rotary switch that could well be used to redirect the output to a stereo jack (to be added) for headphones. Finally, there were enough room to add a volume control.
In fact, the R-326 does not offer a real AF gain control on its front panel. Rather, the output audio level can be controlled by acting on the RF gain control. In practice, it is expected that the audio level be controlled externally, on the loudspeaker.

The LS-166/U detailed information can be found here:
LS-166/U

This is the original schematics of the unit:

This is how I have modified it (I hope it is readable):

I removed the original cable (terminated by the U-77/U connector) and replaced it with a robust bipolar cable terminated by two very simple banana plugs, suitable for the R-326 audio output socket.
Then I re-wired the internal connection to adapt for the addition of a 100 ohms wire potentiometer and a stereo 6.3 mm jack.

NOTE: after first period of usage, I preferred to re-wire the volume control as a voltage divider, in parallel with the secondary of the impedance transformer. The original series connection did not allow to completely silent the audio output.

This is a short video showing the unit while working connected to the R-326 receiver.