I am doing general handyperson stuff for a local church. They rent their hall out for community events, and since their main speakers tend to blow fuses sometimes, they bought a pair of nice, smaller speakers to use as backups. They are the kind of speakers where you slide the bare wire into two slots in back, left and right.
The problem is, instead of being attached to a home stereo which has the same kind of hookup, these speakers will be getting their signal from a mixing board. The output from the mixing board is standard RCA jacks. This is not my field of expertise – can I solder RCA plugs onto the other end of the speaker wires? How would I combine the L and R wires? (I can set the mixing board for monoaural output to each speaker.)
I know you guys will know. Thanks a lot!
Those RCA cables won’t produce enough voltage to drive the speakers – you need to run them through an amplifier first. Are the other pair of speakers attached to an amplifier, or do they have an amp built in?
Which fuses are being blown?
Are they blowing an electrical circuit, indicating that there’s too much equipment plugged into the circuit? The fix for this is to simply find different outlets on other circuits, or unplug the coffee pot or whatever else is also plugged into that circuit. From past experience, churches are notorious for having 18th-century wiring and they often seem to have only two or three 15-amp receptacle circuits for the whole building.
Are fuses internal to the amplifier(s) blowing, indicating too much volume? eg: you need more efficient speakers, or a higher-powered amp. Or an intermittent short in the speaker wires that only acts up when the power levels are high, or the cable moves into just the wrong position.
The main speakers themselves have fuses which blow, & I have to climb up a hair-raising distance to change them. Now, I really know very little about electronics, basically just the principles involved; and I know how to solder things.
Anyway, the fuses in the speakers are 3 amp; while the PA manual says it (the PA) has a 4 amp fuse. My theory is that people who use the sound system push the sliders way up, and since the PA at max puts out more than the speakers can take, that’s what does it.
Clearly the ultimate goal is some higher-rated speakers or, since they have neighbor/noise issues, finding some way to prevent people from turning up too far.
The PA does actually amplify the signal before it goes out to the speakers. The other speakers are just connected to the PA via the RCA jacks; but the new speakers need to have their own cables because of the aforementioned scary climb.
That being said, do I just solder RCA jacks onto the end of the speaker wire? And what do I do about the left/right thing?
Thanks.
How old is the PA system? Some older ones had weird speaker impedance ratings that could render your newer speakers incompatible.
The mixer board probably (hopefully) has a couple of signal out connectors. You’ll want to get an appropriate amplifier, use interconnect cables to hook into the audio out from the mixer (this would probably be RCAs) and then regular stranded wire from the amplifier to the speakers. The amplifier doesn’t need to be anything special. I’d look at used stereo receivers. Make sure it won’t overpower the new speakers and that they have audio in connections. Since the church has neighbor issues, try to find a receiver that has limited power to the speakers. For a standalone solution, consider something like this: Sonic Impact from Amazon.
Swap the fuses - put 4 amps in the speakers and 3 amps in the PA amp. Your speakers will still be protected, but you won’t need to climb ladders to change the fuses.
A PA amp that uses RCA jacks for the speaker outputs? I’m going to venture a guess that you’re running it right at the bleeding edge of what it can do, and the amp is overloading. Usually, PA amps have 1/4" jacks or Speakon jacks. RCA plugs and jacks are fragile little things that normally aren’t used in PA systems.
You might want to look at upgrading the amp first - you can probably use the existing amp as a pre-amp / mixer to feed the power amp.
Well, maybe I haven’t stated my problem clearly. Perhaps I am not asking the right questions.
The existing speakers work with the PA just fine, except when they (the speakers) blow their own fuses. It’s happened twice; both times, both speakers’ fuses had to be replaced.
So the church people bought some smaller, fairly good-quality monitor-type speakers to use as backups in case the main speakers crap out in mid-event. A lot of their events are meetings and small gatherings that don’t need super-loud amplification or marshall stacks, YKWIM.
The PA has a built-in amplifier which is (more than) adequate.
The existing speakers have the same bare-wire slidey things in the back, into which you insert L and R speaker wire. These wires terminate in RCA plugs, which plug into the signal-output RCA jacks on the mixer.
I need to make new cables for the new speakers so that we can just switch plugs going into the PA output, to switch speakers.
What I need to know is how the attaching of the RCA plugs is done to the source end of the speaker wire. The plugs unscrew, and there is a metal doohickey which is meant to hold the wire that is soldered in, but I don’t know how this is properly accomplished. It’s not self-evident. Do I just have to make sure the copper from both wires is touching the shallow depression on the inside end of the plug?
Thanks.
Oh, crap. I took too long typing, and missed your post, gotpasswords. That’s an excellent idea, about switching fuses. Thanks!
About the plugs, I think I am mistaken. I think they are indeed 1/4 inch. The great big kind like on the end of a guitar cable. Quack.
So how do I solder them on?
1/4" plugs? OK, now we’re cooking.
Once you unscrew the body shell, there should be a smallish tab with a hole near the center. That’s connected to the very tip of the plug. The long strip along the side may or may not have a small hole for soldering a wire to.
Thread the wire through the plug’s shell that you’ve unscrewed so you can re-assemble it later. Strip a little insulation off each end of the wires, and solder the side of the wire with the ribs/printing to the tab for the plug’s tip, and solder the other side to the long strip.
Wrap a few turns of electrical tape around the wire where it will be held by the long strip and gently squeeze the strip closed around the wire. You just want to hold the wire snugly, rather than squash it. Screw the plug body on and repeat at the other end.
Look about halfway down the page for a picture of this. Look for "freshly wired guitar plug)
Yow, thanks, gotpasswords. Beautifully succinct response. I understand how to do it now. You rock!
One small note on soldering the jacks…
Be sure and keep the polarity of the wires the same on both jacks, and on the connections to the speakers.
If you don’t, the signals to the two speakers will be “out of phase”. meaning that the sound will be muddled in certain areas of the church.
The speaker wires should be polarized by either colour (Silver/gold is very common) or by ribbing on pne side of the joined speaker wires.
Regards
FML
So now you know the difference between 1/4" phone jacks and RCA phono jacks, right?
Makes a difference. 
And as FML said, respect your polarity. If you don’t have color-coded wires, use an ohmmeter to be sure. It doesn’t matter which line goes to the center conductor, but it must be the same for both (all, if you have more than a pair) of the speaker pairs. Speakers that are out of phase lose bass and may sound funny in some parts of the room.