Circuitry Question for This Forum's Electricians

[SSTJ]

No practical concerns here, I'm just curious ...

I have a Uniden 520XL CB radio with this 8-ohm, 15-watt speaker. Works fine. Let's say I use this splitter to add a second, identical speaker. What will happen?

As I see it, this would create a second, parallel circuit. That would reduce the overall resistance of the 'overall' circuit, and my Uniden would therefore have more amps drawing from it whenever the speakers were engaged. But my questions are:

1. Would adding the second speaker actually have any impact on the volume of the first speaker?
2. Would the combined volume of both speakers actually be louder than when I had just one?

I realize this same question must come up in countless contexts, but this just happens to be the context in which I'm coming across it.

 

[glowell222]

No practical concerns here, I'm just curious ...

I have a Uniden 520XL CB radio with this 8-ohm, 15-watt speaker. Works fine. Let's say I use this splitter to add a second, identical speaker. What will happen?

As I see it, this would create a second, parallel circuit. That would reduce the overall resistance of the 'overall' circuit, and my Uniden would therefore have more amps drawing from it whenever the speakers were engaged. But my questions are:

1. Would adding the second speaker actually have any impact on the volume of the first speaker?
2. Would the combined volume of both speakers actually be louder than when I had just one?

I realize this same question must come up in countless contexts, but this just happens to be the context in which I'm coming across it.

Adding the second identical 8 ohm speaker will not reduce the resistance of the circuit. For question number 1: does the CB have enough power to adequately sound both speakers at the full 15W? If it does, then yes-you will have 2x15W of CB radio loudness. If it doesn't, then you may have reduced volume in one or both speakers. For question 2, it's the same answer as for question 1.

 

[Jerry Bransford]

Yes wiring two speakers in parallel will halve the impedance/resistance. Absolutely. That's basic Ohm's law.

The problem I see is PA speakers like that have relatively low "Sensitivity" ratings which simply means they require a lot of wattage power to drive them. That "15 watt" rating they push means nothing about how loud it'll be, that just means it can handle 15 watts from whatever audio source it is connected to without damage. And its specifications are pure bullshit, no speaker provides power and its "RMS" rating is bullshit too, that's strictly a rating for an amplifier's measured output, not a speaker.

The bigger problem is your CB's speaker jack only puts out, on average, 1-2 watts. 3 when it's really loud, 7 watts PEAK power when the earth and stars are in alignment.

Your CB's little audio amplifier (I also use the Pro-520XL) couldn't power two big speakers like that in parallel, it can barely power that one.

Look for a different PA speaker that has a complete specifications instead of that BS "15 watts at 115 dB". It can only put out 115 dB if it's driven at 15 "real" watts which your/our CB simply cannot even come close to. What you're looking for is a Sensitivity rating of at least 90 dB or higher.

If you can't find a PA speaker with an adequate Sensitivity rating, you can always connect a line-level amplifier between the CB's speaker jack and the speaker. Then you'll have enough power for an external PA speaker.

If you plug that Amazon speaker into its speaker jack, you're going to be very disappointed in its low power output.

I still cannot believe the absolutely misleading "specifications" it is quoting... pure BS except that it probably could produce a 115 dB sound pressure level if it was driven with 15 real watts.

 

[CharlesHS]

Why not use a cable with double male ear phone jacks; plug one end into the speaker output of the CB, select Audio IN on the Jeeps stereo and then plug the other end into ear phone jack input of the Jeeps stereo. Then you can use your Jeep stereo amplifier with the vehicles speakers to broadcast your CB audio output.
Just don't turn the volume up too high or you could get a squeal (feedback) from the speakers into the microphone.

 

[SSTJ]

Yes wiring two speakers in parallel will halve the impedance/resistance. Absolutely. That's basic Ohm's law.

...

@Jerry Bransford , thanks for this. Very helpful.

For the more 'theoretical' side of my question, let's imagine that I had found a loudspeaker that met your specifications, in terms of sensitivity, etc. Then, what would your thoughts be on my Questions #1 and #2?

 

[SSTJ]

Why not use a cable with double male ear phone jacks; plug one end into the speaker output of the CB, select Audio IN on the Jeeps stereo and then plug the other end into ear phone jack input of the Jeeps stereo. Then you can use your Jeep stereo amplifier with the vehicles speakers to broadcast your CB audio output.
Just don't turn the volume up too high or you could get a squeal (feedback) from the speakers into the microphone.

Thanks. That's an interesting 'hack' solution.

As mentioned in the original post, this is more of a theoretical question. I'm curious about how adding multiple speakers, in parallel, impacts the performance of the original speaker, and of the overall volume, etc.

 

[Jerry Bransford]

Placing speakers in parallel divides the power between them. You'd have to turn the volume up, if it had enough oomph left. You could add a line input amplifier to give them both more power.

 

[SSTJ]

I also found this very helpful. In short:

• Yes, adding a second speaker without adding any power would make the first speaker quieter, because the first speaker gets less power than it did when it was the only speaker.
• Still, the addition of the second speaker makes for overall more volume, because it more than compensates for the decrease in the first speaker.

But again, this more hypothetical. To actually apply this, @Jerry Bransford makes great points about the real specifications of CB radios, and of loudspeakers, etc.