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Can I hook up front and rear speakers to the same channel w/o screwing up the crossovers?

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Can I hook up front and rear speakers to the same channel w/o screwing up the crossovers?

This question is answered

 Here's my setup:

Kenwood excelon head, Infinity reference component speakers in front (4 ohm), infinity 2-way speakers in back (4 ohm), 4-channel JBL amp, JBL sub. The fronts and sub are hooked up to the amp. The rear speakers are hooked up to the head unit.

The head unit has an option to bypass the internal amp. I found that doing so increases the sound quality so much that I elected to bypass it, leaving my rear speakers unpowered.

I would kindof like to have rear speakers again. I like having the head unit's amp bypassed, so I am looking at hooking them up in series or parallel with the fronts on the amp (not sure if it matters between the two, as the amp can probably handle 2 ohm).

So here is the first question. Hooking up the front and rear speakers together will change the impedance. Will that screw up the speakers' crossovers?

Second question: I want to be able to adjust the level of the rear speakers to balance with the fronts. Would I need an l-pad for that, or would a simple potentiometer work? (Again, without screwing up the crossovers. I noticed a capacitor attached to the 2-ways, so they have at least a high pass on the tweeter.)

Verified Answer
  • If your ultimate goal is getting flawless sound quality, your better off the way you have it now.  What may ultimately be the best solution is to add an amp for the sub. 

    There's no reason to not give it a try, tho.  As long as you don't try to run the coaxials off the crossover's output, the crossover will work fine.  it will have the same amount of power running through it or less, depending on your amp.  The damping of the amp will be reduced, and if your ears are sensitive enough to detect a difference when disabling the HU amp, you may very well be able to recognize the difference in damping as well.  L-pads were not intended for the purpose you have in mind, because along with attenuation, they would slightly shift the phase of the rear speakers from your fronts.  That may give you unwanted side effects.  If the rears were sufficiently attenuated, it would be hard to detect.  You can calculate the resistor values here

    IMO it does seem like more trouble than it's worth, but experimentation is the best way to learn.  Even if it doesn't do what you want, you may be able to find a more conventional purpose for L-Pads in the future.

  • I hadn't heard of the L-Pads before (amazing what's on BCAE1) and typically I would have said you can't adjust the relative front to rear volume with both speakers on one channel.

    Another thing to consider is you will now be sending half the 2-ohm wattage to your rear speakers, so you need to be sure they can handle that.

    Hope This Helps!!!

    2002 Ford Focus JVC KD-A815 Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

All Replies
  • I would say your increase in SQ probably came more from your rear speakers being deactivated than you deactivating the internal amp.  Seriously just leave the rear speakers unpowered.  Rear speakers are only for rear passengers and if there are none there, my advice is keep them off.  They just crap up your soundstage.

  • Actually, I tested it with the rear speakers off and just tested the effect of turning off the head unit's amp with only the fronts and sub. It sounds good the way it is, but I think it might be nice to have just a touch of rear speakers. If it's going to be too much hassle, I'll just leave the rears off.

  • If your ultimate goal is getting flawless sound quality, your better off the way you have it now.  What may ultimately be the best solution is to add an amp for the sub. 

    There's no reason to not give it a try, tho.  As long as you don't try to run the coaxials off the crossover's output, the crossover will work fine.  it will have the same amount of power running through it or less, depending on your amp.  The damping of the amp will be reduced, and if your ears are sensitive enough to detect a difference when disabling the HU amp, you may very well be able to recognize the difference in damping as well.  L-pads were not intended for the purpose you have in mind, because along with attenuation, they would slightly shift the phase of the rear speakers from your fronts.  That may give you unwanted side effects.  If the rears were sufficiently attenuated, it would be hard to detect.  You can calculate the resistor values here

    IMO it does seem like more trouble than it's worth, but experimentation is the best way to learn.  Even if it doesn't do what you want, you may be able to find a more conventional purpose for L-Pads in the future.

  • I hadn't heard of the L-Pads before (amazing what's on BCAE1) and typically I would have said you can't adjust the relative front to rear volume with both speakers on one channel.

    Another thing to consider is you will now be sending half the 2-ohm wattage to your rear speakers, so you need to be sure they can handle that.

    Hope This Helps!!!

    2002 Ford Focus JVC KD-A815 Sony CDX-GT410u Sony XT-100HD HD Tuner Stock speakers, no amp, no subs

  • Thanks for the reply. If changing the impedence before it hits the crossover means it doesn't mess it up, then there's no need to use an L-pad. I guess a couple of regular potentiometers in series with the rear speakers would work. I'm not sure how many watts the pots will need to be rated for.

    I don't really understand how it would shift the phase of the rear speakers, but I know that out of phase is a bad thing. I am kindof leaning toward just doing nothing right now.