Sending two XLR out signals to two old loudspeakers

Draft by Gwendolin Korinek, Festspiele Reichenau. CC-BY-SA

This design is a draft which I did not put in practice, but may be useful for theatre purposes.

If you have a pre-installed network cable connection to attach a stagebox (which only provides XLR outs) e. g. on stage left or right, but your FOH is miles away because the theatre hall is quite big, you can save a lot of cable metres with this approach.

The reason you may want to use oldschool loudspeakers is that they could be a functioning prop, part of a play that takes place in, say, the 1970s.

This draft turns two balanced signals into two unbalanced signals.

You need:

- a stagebox 

- two XLR cables

- a special adapter (which you need to solder yourself)

- a 3.5 mm jack cable

- an old household stereo player (which is the „amp“ for the two unbal signals) with a 3.5 mm jack aux input and two oldschool loudspeaker outs

- four loudspeaker cables (2x signals, 2x minus/sleeve)

- two oldschool loudspeakers

- one socket for the stereo player, ideally completely separate from lighting apparatus sockets to avoid hum or issues related to dimming

- stage camouflage to hide the stereo player

Here‘s how it works, in words:

You are sending two signals (double mono, or stereo) to two stagebox XLR outs. Every parameter, including SPL and EQ, can be adjusted for each channel individually, which is very useful if e. g. you want to pre-program a panoramic fade in QLab, or one speaker is in a very different acoustic position from the other.

Next comes the cool adapter you need to solder together as shown in the draft. It uses the classic headphones TRS configuration. One signal to T, the other signal to R, everything else to S.

The two signals now travel to the 3.5 mm jack output which is fed to an old stereo player with a 3.5 mm jack input. Adjust stereo player settings as needed.

The stereo player is the amp for our signals. Next, the signals are fed to two oldschool loudspeaker cables, which feed the two loudspeakers.

For easier use, the stereo player can be hidden in a prop that can be moved around, and only fed with electricity when the play where it is needed actually takes place. Proper cable management (e. g. figure of eight wiring) and formatting cables to the length required (no excess metres of speaker cable) make life easier.

Enjoy!

If you use this design, please credit me (Gwen Korinek) and Festspiele Reichenau.