Anyone familiar with install of car amplifier in bus?

[belfert]

Okay, so I bought a 4 channel Pioneer GM-6400F amplifier for my bus.  I intend to use it to power 4 speakers off the rear output on the Pioneer head unit I also purchased.  The speakers are 4 ohm if that matters.

Should I just use two RCA splitters to split the audio between the two set of stereo RCA jacks?  This would allow me to run two speakers on input A and another set of speakers on input B.  The amp says it does bridging, but I don't know if that will help.

I don't think the manufacturer expected folks to use the amplifier this way.  Folks using four speakers would generally use the front and rear RCA outputs from the head unit.  The manual is fairly worthless.

[buddydawg]

You can split the RCAs or if the amp is 2 ohm stable you can run 2 speakers off each channel by wiring them parallel.  This will leave the other channels available for more speakers if you wanted to add some at another time.

[WEC4104]

Brian:

Using a pair of "Y" stye RCA splitters would allow you to use the 4 channel / 4 speaker set up, but I'm not sure how much signal degradation you get from using the splitters.

I do have another approach that crossed my mind....


The Pioneer GM-6400F has pre-amp inputs and pre-amp outputs.   Suppose you connect the left and right outputs from the stereo head unit to the Channel 1 and Channel 2 inputs on the amplifier.   Next, grab a pair of short RCA style patch cables.  Connect them from the amplifier's Channel 1 and Channel 2 pre-amp outputs.   Run the other end of the cables into the Channel 3 and Channel 4 inputs on the amplifier.  I'm thinking this is an alternate solution.

[belfert]

Would a good quality splitter like Monster or something similar that has more copper be better?  I probably wouldn't really use Monster because too expensive.

Monoprice sells their RCA splitter for 46 cents, but it looks pretty cheesy.  Lots of folks praise Monoprice, but mostly for digital cables where the cable doesn't matter so much with 1s and 0s.

[Jeremy]

Just to check first that I understand what you are trying to do:-

You have six speakers, two in the front and four in the back.

The front two speakers are driven directly from the head unit
The four rear speakers are driven from a four-channel amp via the head unit's 'rear' line-output
The rear speaker outputs from the head unit, and the 'front' line-output are not connected to anything

Correct?

If so, it occurs to me that the easiest thing to do is to split the four rear speakers into two pairs, driven via the head unit's front and rear line outputs. If the six speakers are actually positioned a similar distance from each other in a 'front/middle/rear' configuration, this would work fine - the fader would simply operate the 'front & middle' set together, rather than the 'middle & rear' set together.

If however the four rear speakers are close to each other and are all some distance from the front pair, and you want to use the fader effectively, you need to do something else.

I've looked at the manual for you amp, and I see it can run in two-channel mode off a single input (ie. no need to split RCA cables) by use of the '2CH' switch (see page 10 of the manual). This makes the two sides of the amp into single channels - see page 9 of the manual for how to use all four speaker outputs to wire just a pair of speakers when in this mode. To wire two speakers in parallel is straightforward as long as the amplifier can handle the resulting impedance - however there is a problem here as on page 8 of the manual it says "Speaker impedance is 2 ohm-8 ohm in 4-channel mode, or 4 ohm-8 ohm when in Bridged or 2-Channel mode". That means you cannot use 2 4-ohm speakers in parallel (sum impedance 2-ohm) when in 2-channel mode.

Which means that if you are determined to run in this configuration you either need different speakers, or a different approach - possibly a split input lead after all. I assume the amp can operate on half the signal it was expecting, but I'm not sure if there are downsides to this - I've never done it myself. There may be more information in the manual for your amplifier, but I only had a brief look.

Jeremy

[belfert]

I will use the rear RCA audio out jacks on the head unit to supply the amp.

It isn't clear if 2 channel mode supplies power to all four speakers.  The labeling seems to indicate that each set of two channels suppplies one set of two speakers.  I am going to call Pioneer to clarify.

[Jeremy]

One channel means one speaker - stereo sound therefore has two speakers - a left and a right channel. Therefore in two channel mode the amplifier will 'think' it is driving two speakers even if you wire two sets of two in parallel (ie., four speakers in total) - but understand the impedance issues mentioned above before doing this.

Incidentally, I noticed in the manual that your amplifier will also (unusually) allow itself to be driven by the head unit's speaker output if suitably configured. I didn't read up on this bit, but another solution for you might be to drive one side of the amp (ie., one pair of channels) from the line-out, and the other side from the speaker output.

Jeremy

[WEC4104]

If the amp, running in 2 channel bridged mode, supports 4 - 8 ohm loads, what about wiring pairs of speakers in series?  Two speakers @ 4 ohms each, wired in series, would yield a permitted 8 ohm load.  No?

[Nick Badame Refrig/ACC]

Hay Brian,

Here is the short on amp bridging.

Amplifier bridging is simply using 2 channels of an amplifier to drive a common load. For 2 channel amplifiers, one left signal and one right signal is used to drive a mono speaker load. Keep in mind

that mono and bridging are not necessarily the same. Mono means that there's only one output signal. There could be more than one speaker but each speaker will have the same output.

Bridging means that you are using more than one source of power to drive a load (speaker). The sources of power are one each output from either channel of the amplifier. A long time ago,

amplifiers had signal on the positive output speaker terminals only. To bridge one of those amplifiers, you'd have to use some means to invert the signal on one channel (remember the

old 'bridging modules' for Orion amplifiers?). Today's bridgeable amplifiers have an inverted channel as part of their design. For many amplifiers, the left positive and right negative are are the

signal outputs. A few use the left negative and the right positive. Others still (mostly mono amplifiers that are to be used in bridged pairs) require that you choose 0° or 180° via a switch to

invert the signal.

Hope this helps
Nick-

[Jeremy]

If the amp, running in 2 channel bridged mode, supports 4 - 8 ohm loads, what about wiring pairs of speakers in series?  Two speakers @ 4 ohms each, wired in series, would yield a permitted 8 ohm load.  No?

Yes, I believe that would work - again, something I've never done in practice myself.

Jeremy

[belfert]

I talked to Pioneer today and they say there is no way to use two channels and get the sound out of all four speaker outputs.  I'll just have to use all four channels with RCA splitters as I originally planned.

[Jeremy]

I'll just have to use all four channels with RCA splitters as I originally planned.

Out of interest, is that the approach Pioneer recommended? I'm interested to know whether simply splitting the input signal in half is considered acceptable. There must be a way of splitting the input signal as mega-stereo installations use banks of amplifiers in parallel - but I'm not sure whether there is some device available similar to the amplified splitters used when running multiple TVs off one antenna.

Anyone else know?

Jeremy

[Homegrowndiesel]

Hey Brian Belfert,
Wow they have some really good tech advise. I bet if you phrased it different you would get a different answer.  "I talked to Pioneer today and they say there is no way to use two channels and get the sound out of all four speaker outputs."  Of course there were several answers that would work, but the best one is.  " I'll just have to use all four channels with RCA splitters as I originally planned."  I want a surround sound processor.

Good luck.