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Wiring 4 speakers to 2 channel amp

Discussion in 'In-Car Entertainment' started by sharma, Apr 30, 2007.

  1. sharma
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    sharma Member

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    [Apr 30, 2007]
    Hi,

    I have a good 2 channel amp however i have 4 speakers wired to it. Currently the left channel on the amp runs both the rear and front left speakers and the right channel runs both the rear and front right speakers. However as i have a sub, i want the midrange and treble to be comming front the front speakers more.

    Can i wire it so that the left channel on the amp runs the front speakers and the right channel runs the rear speakers? Then i can fade it so that there is more comming out of the front speakers. I don't see how this would cause a problem although it may affect the way the stereo sound comes out.

    Thanks.
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  3. dualmono21
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    dualmono21 Well-Known Member

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    [Apr 30, 2007]
    what amplfier is this please ???
    is the amplifier two ohm stereo stable ???
    if the amplfier is 2 ohm stereo stable then yes you could in theory wire it like that
    if you do wire it like that you will in fact be listening in mono
    so i would not advise it

    my suggestion would be to run the front speakers only from the amplifier
    and forget the rear speakers and dissconnect them
    the adjust the gain between the subwoofer and the main front speakers to get the sound you desire
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  4. sharma
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    sharma Member

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    [Apr 30, 2007]
    I do not think the amplifier is 2 ohm stereo stable. How do you find this out? It does not say this anywhere on the amp and you cannot change the sound mode(i.e stereo, mono, e.t.c). I have used the amp like this for years in my old car however and have had no problems with it as yet.

    What will be the sound difference if i wire it like that? Will it really make any real difference? I have put the rear speakers in specially so i do want to make some use of them and i want some midrange and treble comming from the back even if it is a lot less than the front.

    My other option (which i am not looking to do anytime soon) is to connect a 4 channel amp instead of this 2 channel one. However the blaukpunkt adaptor i am using only has 2 pairs pre amp outputs. I would need 6 to do this as i have another amp running my sub. I know you can buy connectors to make one of the pairs into 2 pairs, however would this solve the problem of me changing the balance as it is still the one rca pair split into 2.
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  5. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Apr 30, 2007]
    You need another amp, or replace the 2ch with a 4ch.
    Yes you only have front & rear RCA's, but you split the rear RCA's to feed both the rear amp & sub, or split them to feed the front and rear amps, but set the gain on the rear amp to a level lower than the front to give you the balance you want. Then use the balance on the HU to adjust the level of the sub i.e. more front = less sub, more rear= more sub.
    this is probably a better compromise if you don't have a sub out on the HU, as once you set the front & rear speakers to your liking, you very rarely have the need to adjust them again, whereas the sub will benefit from adjustment depending on how bassy different kinds of music are.
    Most decent amps have a straight through pre-out on them (to feed additional amps) so you shouldn't need to use Y splitters.
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  6. sharma
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    sharma Member

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    [May 1, 2007]
    I am looking at buying a 4 channel amplifier and feeding the front speakers and the sub though that and using the exsisting amplfier to run the back speakers so i can set a lower gain level for the rears. However will i not loose audio quality and will the power not split for the rears if the rear pre outs are split into 2 sets of pre outs?

    Also whats the best high pass frequency setting for speakers if i have a sub (i.e. dont want bass going through speakers, however i do want the full midrange and treble going though the speakers for clear sound).

    Another option i have is to get a set of passive crossovers and feed the rears through them. Or is there not some sort of volume controller i could connect to the rears?

    Thanks.
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  7. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [May 1, 2007]
    No you can split the rear pre-outs without any loss of power, or as I suggested by a decent 4 channel amp which will have it's own pre-out output to feed another amp without splitting.
    Normally you would set the sub at around 80Hz low pass, and the high pass at 80-90Hz.
    Personally I'd just buy a cheap £30 Alpine amp on ebay and use that for the rears. You can get a small 2 x 30wrms Alpine dirt cheap these days.
    Forget using crosovers, and buying a pre-out fader will be more costly than just adding a small amp, and you'd then have to mount it somewhere and install additional RCA leads - very messy.
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  8. dualmono21
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    dualmono21 Well-Known Member

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    [May 2, 2007]
    if you want to run both the front and rear comps and a sub
    then a one box solution like a 5 or 6 channel amp would be the neatest
    adding multiple amps can get messy as andy quite rightly says

    there is a rare amplifier called an xtant 3300c which is actually a three channel amp but can be used like a five channel and has the facility to turn down the gain of the rear speakers
    if your lucky you may find one on ebay
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  9. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [May 2, 2007]
    Or an Alpine MRV-F450, which is a true 5 channel amp with dedicated sub channel. they go for around £120-140 on ebay.
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  10. sharma
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    sharma Member

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    [May 2, 2007]
    Th xtant 3300c is only a 600 watt amp so although it sounds good i don't think it has enough power to run my speakers and sub.

    I think i am just going to go for a powerful 4 channel amp and run the fronts and the sub off that and run the 6 x 9's off my other amp. You sure 80-90hz is fine for the high pass? Should it not be more along the lines of 250hz to cut out the bass?

    Also i know you guys said a 400 watt amp is not enough to run a 600 watt sub, why do so many shop sell packages like this? And that would mean a 800 watt amp is not enough to run my components and my 600 watt sub? Also what is the maximum gain an amp should ever be set to? Should it not go beyond 3/4?
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  11. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [May 2, 2007]
    600w, 800w, 1000w amp, doesn't mean a thing. You need to look at the RMS figures per channel at 14.4v into 4 ohm

    "You sure 80-90hz is fine for the high pass? Should it not be more along the lines of 250hz to cut out the bass?"
    You ask for advice/recommendations then query each one - very annoying.
    Most decent amps won't even provide a crossover point at 250Hz. Why? because you'd effectively be losing all the midrange between where the sub low passes and the mid range high passes i.e. nothing between 100-250Hz.
    Shops sell those packages because they're cheap shyte, and people who don't have any budget will buy them.
    The gain on an amp is purely to match the input level between the HU and the amp. There is no definitive setting as it all depends on the pre-out level of the HU, the losses in the RCA's, the sensitivity of the amp and the load (speakers) connected to it. The max gain is the max gain, but if this is the optimum setting for your system then you probably need a better amp or a pre-out booster. Most amps being driven to the limit will not sound good an will start to clip which will damage the speakers.
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  12. dualmono21
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    dualmono21 Well-Known Member

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    [May 2, 2007]
    the rms rating on the subwoofer means absoloubtedly nothing at all
    but the one on the amplifier means everything
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