I read this 4 times trying to figure out exactly what you're trying to do. I've made hundreds of cables that go from XLR to RCA and to ¼" and ¼" to RCA and it depends on the output configuration and the input wiring configuration since some components will wire the hot lead opposite depending mostly on USA or European design but that's not what confuses me. You have active speakers with a volume control on the speaker which has its own built in amplifier?
And you're making a set of active speakers and you want to have a volume control on the speakers you're making?
The volume control would be th
e input control of the amp you're using which is internally set in a circuit that adjusts the voltage the amp sees.
Adding any type of pot within the wiring may and up being noisy when the pot is adjusted that way unless a circuit that's made to control the voltage (like within the amp) is used. What I'm saying is if your amp(s) don't have an input adjustment on it or them then they will be running at full volume at all times and will require a preamp source to control the volume.
All but 1 of the many amps I have stacked up have an input control built into the amp, almost every pro amp will have a "volume" control to set the level for each channel and can be used as volume controls. The only amp I have without any type of level matching control is Bob Carver amp but I use an active crossover which has volume control that adjusts the volume output from each band. A 3 way crossover has an input gain of that controls the gain of all outputs and each output has its own adjustment for each low mid or high output going to each amp that drives each driver. The amps also have their own internal gain adjustment for each amp channel.
What is the source? They aren't getting a signal from nothing, so without knowing the source it's hard to say where your volume control should be? Even if it's coming directly from a guitar it will have a volume control, or if it's coming from a Bluetooth sound card it will have at least 2 or more ways to control the volume.
Using a cheap headphone amp or any cheap interface will have volume controls built in and the interface will typically convert the XLR input to s choice of outputs eliminating the need to use a change cable. Cheap interface or head phone amps can be found for about $25 new.
My question is again what is the XLR source? It is the XLR the input to the active amp?
Your drawing shows the XLR - ¼" - RCA as the audio input, input to the speaker amp? Then you have the wire as an arrow running to a crossover RCA output? (In reality the crossover feeds the amp not the other way around) If it's an active crossover it should have a master volume or gain control built in. If it's an analog crossover it's not going to have an RCA output unless you've changed it to be an analog pre before the amp and Ive never seen that set up used before. I'm not say it won't work but I question the validity of using it like that when you can use 1 amp and connect the analog crossover to the amps output and control all drivers with that one channel and use resistors to control each drivers volume to match the drivers combined sound and the source is the main overall volume control like the headphone amp or interface or any pre amp would.
Are you making a multi amped active speaker? If so use an active crossover that controls each amps individual driver and still use a pre for overall volume or the input gain adjustment on the active crossovers input. You'll still need a source so that's why I'm confused about this?
