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Old 02-17-2009, 01:10 AM   #1
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Stereo / Speaker questions.

Today I thought I'd take a look at getting a stereo put in my bus. It has speakers up in the ceiling and at one time had a stereo which was yanked before I bought the bus. Of the wires that were snipped where the stereo went here is what I found:

1 - Ground
2 - Always Hot
3 - Hot when key is turned to "on" or "accessory"
4 - Speaker wire going to the speaker outside of the bus
5 - Second speaker wire going to the outside of the bus
6-9 Two of these three wires go to some of the speakers in the ceiling. The other one I have no idea what it does.

I have four speakers in the ceiling. I get sound out of two of them. The two on the right side get sound, the two on the left side get nothing. If I disconnect one of the speakers that works the other one stops working too. I thought this kind of odd. Of the three speakers I pulled all had an orange wire going to it, but the other wire was of different colors. None of them match wires going to the stereo, so it is safe to assume that there are connections somewhere between.

At this point I should confess I know nothing about stereos, so might make assumptions that are incorrect. The best I can conclude is that I get two channels coming out of the stereo, two speakers on the right channel and two speakers for the left channel, and that the remaining "mystery" wire is used in conjunction with one of the others, used as a common, to get the left channel working. I further assume that the wiring on that channel is flaky somewhere which is why it's not working.

Are my assumptions correct?

If I need to rewire the speakers that don't work, how do I do it? I don't even know where the wires go up to the ceiling at. Is it even possible to get to them without pulling a ceiling panel?

Thanks for any and all input.

-Ray
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Old 02-17-2009, 01:37 PM   #2
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Re: Stereo / Speaker questions.

Hm.. It sounds like the speakers are wired in series where the positive from the head unit goes to one speaker, then the negative of that speaker goes to the other speaker, and the negative of that speaker goes back to the head unit. Wiring speakers in this way will half their resistance, which could be a problem if it drops to below what the head unit can handle. Car speakers and stereos are usually not designed to be wired this way, so I would be dubious about keeping it like this. It won't hurt the speakers, but it might overload the stereo.

I'm not sure how the panels or wiring in your bus work, but if you can figure out an easy way to rewire your speakers, I think that would be a good idea just to replace all the old wires with clean new ones. It sounds like it was "half assed" the last time. Chances are that your stereo has 4 speaker outputs(each with a + and a -). The ideal way to wire the system would be to run an independent set of wires to each speaker from the stereo.

If rewiring the speakers isn't an option, try to use the existing wires to get the left channel wired how the right channel is. I'm assuming it's like this: [stereo +] --- [+ speaker 1 -] --- [+ speaker 2 -] --- [- stereo]
The only other way that it could be set up if a single channel is powering the two speakers is by bridging all of the +, then bridging all of the - back to the stereo -, like:
Code:
|-[+ stereo    -]-|
|-[+ speaker 1 -]-|
|-[+ speaker 2 -]-|
If it was set up this way, though, each speaker should be able to operate even if the other one is not plugged in, so I'm guessing this is not the case.
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Old 02-17-2009, 07:39 PM   #3
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Re: Stereo / Speaker questions.

I have to agree with the others though wired in series DOUBLES the resistance, not halves it, and wiring in parallel halves it, not doubling it. Less resistance (impedance really) is what puts a greater load on the amplifier in that there is nothing to "hold it back."

I suspect they are wired in series. I know my bus uses a really goofy wiring configuration. I also wouldn't be surprised if they were wired in parallel, but used a common ground based on your description of the wiring. That just doesn't seem to fit if unplugging one kills another one.

Here's a simple test. Use your multimeter to ohm out an individual speaker. IIRC a 4 ohm speaker should test out to about 3.7 ohms on the meter. Now plug that speaker back in and go to the harness at the back of the headunit and ohm it out. If the resistance seen is more then they are in series. If it is less then they are in parallel. This is important if you're looking at getting replacement speakers.

Ultimately I think the best bet would be to get a more standard automotive head unit and automotive speakers along with new wiring. Yes, installation is a bit of work, but it will be a higher quality unit and will follow more typical wiring conventions. Heck, if you really wanted to make it scream then you could add an external amplifier for the speakers. Most headunits put out 20-25 watts RMS per channel at 4 ohms. Many can put put into a 2 ohm load on the front channels and some can even do it on all 4, but beware. The field effect transistors in the internal amplifier will most likely not like this AT ALL. I rebuilt an old Pioneer head unit I had with bigger transistors to help and it worked great...right up until I burned it up again with a 2 ohm load on just hte front channels. I'm a big fan of external amplification.

*edit* I think Down South beat me to the punch!
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Old 02-17-2009, 07:43 PM   #4
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Re: Stereo / Speaker questions.

The speakers say on them 4 ohms. It doesn't matter which of the two speakers I unhook... they both stop working regardless. I did not measure them with my ohm meter, or at the stereo. I can do that tomorrow.

It appeared all the wires were headed towards the driver side of the bus. There is a panel above the windows that is screwed on, so I thought I'd yank it off and poke around. My goodness, what fun. I got one small section off, but it isn't easy. The upper part has a lip that slides up into the ceiling panel. The lower part fits down into the window frame. So it can't go up or down as it is... Unless I remove the windows I don't know how I'm gonna get the rest of that panel off, and I'm not sure how to take the windows out! There are 4 large screws on each window, but removing them doesn't work any magic. Those windows wont move. If there is a magic method of doing this someone please let me know!

Anyway, looking at the panel I did get off it appears all the wires go down to a wire harness in there that goes to the front of the bus. I'm gonna have fun rewiring that puppy if it comes to that!

-Ray
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Old 02-17-2009, 08:31 PM   #5
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Re: Stereo / Speaker questions.

Hi Ray, I just put a new stereo and speakers in my bus and had the same issue with the wiring. The wires going to the speakers were not the same color that went to the head unit. It also seemed they used a common ground. I ended up running new speaker wire from the speakers all the way up to the head unit since I had bought the equipment from Circuit City and there were no returns.
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Old 02-17-2009, 08:33 PM   #6
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Re: Stereo / Speaker questions.

does your unidentified wire have power when you turn your lights on?
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Old 02-17-2009, 08:50 PM   #7
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Re: Stereo / Speaker questions.

Quote:
Originally Posted by Downsouth
Experience, if I remember correctly, wiring in series does in fact half the resistance - it doubles the impedance's numerical value. While (2) 4 ohm loads wired in series will double the load's numerical value to 8 ohm, they actually half the resistance presented to the source, causing the radio to only produce 50% of its rated power.


If you want to talk about a powerhouse of a headunit, try one of the Pioneer's with the MOSFET power supply! 50 watts per channel, realistically around 33 watts RMS and I have ran subs off the back channels at 2 ohms all day long!

DS

Hmmm...you may be right on the wording there. All that garbage gets into phaser angles and the such because you're talking AC type voltages...nasty stuff. At any rate, wiring in series will cut the load on the amplifier in half by reducing the current demand by half and that means longer lasting parts.

My old Pioneer head unit certainly put out power after I updated. I just don't think it could cool those FET's sufficiently because it was right below a heater duct and already hotrodded up a little. I will probably buy Pioneer again given the quality and features available at the price point.
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Old 02-18-2009, 05:02 AM   #8
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Re: Stereo / Speaker questions.

Ray,
First, rule out a bad speaker in the non-working pair. Take each one out and ohm across it, preferably with the wires disconnected so you are sure it's the speaker you are measuring. If either or both measures unlimited ohms, it won't pass electricity and is bad. If your speakers are in series (as we suspect), then the a bad one will break the connection to the other one, if it is still good.

Just guessing, the orange wires might be a color code for the jumpers between speakers. Here's a clue: on the speakers that are working, is the orange connected to (+) on the first one and (-) on the other? Are they like this:

Left 1> - - Color 1- - (+SPKR-) - - Orange - - (+SPKR-) - - Color 2 - - > Left 2
Right 1> - - Color 3- - (+SPKR-) - - Orange - - (+SPKR-) - - Color 4 - - >Right 2

To match the colors at the radio to the speakers, take the speakers down, mark which wires are (+) and (-) on a paper, and then use an ohmmeter to check which are connected to what. You will probably need a long piece of wire or a clip lead to make your meter wires long enough. Make yourself a list, such as:

Left SPKR1 + green goes to grey & white
Left SPKR2 - blue goes to yellow & white
Right SPKR1 + red goes to grey & yellow
Left SPKR2 - pink also goes to yellow & white

Newer radios have amps that have no output transformers, and the speaker wires cannot be grounded. The outputs are sometimes labeled left 1 and left 2, right 1 and right 2. If you say there are only 3 wires on the last 4 pins, then one of them might be the common for both right and left. Or it's possible there used to be a fourth wire to the non-working speakers. Make sure you have unlimited ohms (no connection) to ground on any speaker wire before you re-use them with a newer unit. If there is one common wire, make sure the new stereo will allow the left (-) and right (-) to be tied together.

Series wiring is the safest for the amps. Parallel wiring will lower the resistance seen by the amp so it approaches a short circuit. Just like putting a screwdriver across an AC outlet, it may draw too much current and burn out the amp. Two 4-ohm speakers in series appears to the amp as 8 ohms. In parallel, they appear as two ohms, and draw 4 times the current at a given voltage. It will be louder, but the life of the amp may be measured in seconds. When you get a new stereo, check the specs to make sure it is rated for loads down to 2 ohms before you switch, or else keep the series wiring.
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Old 02-18-2009, 11:24 AM   #9
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Re: Stereo / Speaker questions.

Quote:
Originally Posted by Downsouth
This is not a bad thing though, as wiring speakers in series actually halves the resistance, cutting the actual workload on the radio in half.
whoops. You guys are totally right. Brain fail.

The bottom line remains that you should probably rewire the system. If there's play in the existing wires (ie. you can pull them through without significant snagging) you might be able to tape the new wires to the old ones and pull them into place without taking everything apart. Try to tape them end to end so you don't have overlapping in order to keep the wire from bulging and snagging on something.
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Old 02-20-2009, 08:22 PM   #10
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Re: Stereo / Speaker questions.

Howdy, all. Much confusion in this post.

Resistance in series adds up. Resistance in parallel divides, by a complex, tedious, and irrelevant formula. Impedance behaves like resistance, with complexities thrown in.

The extra resistance from speakers in series will reduce the current draw from the amplifier. This is a good thing, but the sound output will be weak.

Setting other considerations aside, think about this: The speaker cone vibrates. It is relatively big and heavy. Bass makes it vibrate more than treble. if you set a big heavy mass vibrating, momentum keeps it moving when the applied signal stops. This is known as overhang, the result is muddy bass.

The amplifier damps out this overhang, if it is allowed to. You can help it by supplying big wires from speaker to amp. Try it on your home speakers. Use 18 gauge to one channel and 12 to the other. Crisp clean bass from one side, moof moof from the other. For maximum quality, replace the ridiculously small woofer wire inside the speaker with 12 gauge.

If you want quality audio, run big wire to the speakers, especially the woofers. Not the bogus $50 a foot connoisseur wire from the golden ear audiophile shop, Ace hardware lamp wire works fine.
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