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Thread: Stereo Upgrade

  1. #1
    Registered User HSV Senator's Avatar
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    Question Stereo Upgrade

    I'm looking at a very mild upgrade of the stereo in my 2004 Monaro. I don't want to run aftermarket amps or subs.

    It will consist of an Alpine Head Unit with steering wheel adaptor, 4x45 wrms Alpine KTP-445A "Power Pack" amp, front 6.5" and rear speaker upgrade and Focal Bam Sound Deadening. The rest of the system will be factory standard including rear 6.5" subs in the shelf run off a small factory amp in the boot.

    The factory configuration is causing me grief though. Apparently the front, rear and subs are all 2 ohm speakers wired to present a 4 ohm load to the head unit. I think its the following:

    Front: 2 ohm 6.5" speakers + tweeters = 4 ohm
    Rear: 2 ohm 6.5" speakers + 6.5" subs = 4 ohm

    I assume I need aftermarket 2 ohm speakers front and rear. I can get 2 ohm Focal splits for the front but 2ohm rear speakers to wire with the 2 ohm factory subs are impossible to find it seems. The closest I can find are the following:

    Infinity Kappa 62ix @ 2.7 ohm
    JBL GX602 @ 2.3 ohm

    The JBLs may be USA only too.

    How would the 2.7 ohm speakers work in this configuration? Have I understood the factory fronts properly? Any issues with the Alpine power pack amp and factory amp with this speaker setup? Can anyone foresee any other issues with this configuration ?
    Holden Monaro CV8-R
    Lexus IS250

  2. #2
    Jak Sie Masz! trent from punchy's Avatar
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    Why not run new wiring?
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  3. #3
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    The amp is 4ohm, whats the problem ?

    Toss in the new 4ohm speakers and run some wires to em.
    Last edited by Fondles; 24-11-18 at 06:53 PM.

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  4. #4
    Registered User HSV Senator's Avatar
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    I'm not sure I actually understand what you guys are recommending, there's no where to run wires to? Are you picturing a regular amp? Keep in mind It's an Alpine KTP-445A. It's technically 6 speakers to a 4 channel despite the factory amp, the fronts may be able to run @ 4 ohm but the rears can't. It's a weird way Holden have wired this but not unheard of for factory systems.
    Last edited by HSV Senator; 24-11-18 at 08:10 PM.
    Holden Monaro CV8-R
    Lexus IS250

  5. #5
    Registered User HSV Senator's Avatar
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    This is the amp:

    http://www.strathfieldcarradios.com....iABEgJ_h_D_BwE

    Everything has been plug and play, exactly what I wanted for ease of install and removal but the way the rear speakers have been wired with the rear subs from factory is a bit painful for going aftermarket. Most just go aftermarket amps but It's not what I want to do.
    Last edited by HSV Senator; 24-11-18 at 08:16 PM.
    Holden Monaro CV8-R
    Lexus IS250

  6. #6
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    ahh plug and play, I missed that bit.

    Some of those that work forces are the same that burn crosses.


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    I don't see the problem with the fronts? The factory splits present a 4 ohm load to the amplifier, almost all aftermarket splits will do the same.
    It doesn't matter what impedance the individual drivers are, only the combined total (if they are wired together obviously).
    The rears must have a passive crossover between the amp and speakers if they are wired to the same amplifier channel. Replicating that is going to a be a pain I would think.
    I would run the rear 6.5's from the HU and power the subs from an amp. Not that amp though as it has no low pass filter that I can see.
    If you are trying to avoid amps in the boot you could use one of the micro class d amps behind the dash. Like this: http://www.strathfieldcarradios.com....ug-wiring-kit/
    Run fronts from 2 channels, rears off the HU, bridge the other 2 channels for the subs. It's 2 ohm stable also which gives you some flexibility.
    Do you have a wiring diagram for the factory system? I'm interested in how they crossover the rears.

  8. #8
    Registered User HSV Senator's Avatar
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    Thanks for the response R31t, the 2 ohm comments for the fronts were due to how the factory wired them, as I said to Fondles I think 4 ohm is probably ok there. Itís the rears that are the issue due to the factory amp/subs.

    There is already the Alpine KTP-445A (Class D mini amp) installed in my car:

    http://www.strathfieldcarradios.com....iABEgJ_h_D_BwE

    It runs directly off the Alpine HU (Single Din job right now but Iím thinking of upgrading to a touch screen Head Unit after I sort all the speakers). All plug and play.

    I donít know exactly how the factory system is wired and thus unfortunately donít have a wiring diagram, what I listed is just my suspicion Iíve actually got a thread open on the Holden forums asking to confirm my thoughts. I just know that the actual factory speakers are stamped 2 ohm. There seems to be heaps of conflicting information out there on this.

    My thoughts were as long as I put 2 ohm speakers in to match what came out then thereís no problem. Getting the 2 ohm speakers then became the problem!
    Holden Monaro CV8-R
    Lexus IS250

  9. #9
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    CDT do a 2ohm 6.5" coaxial.

    https://www.cdtaudio.com/coaxials/cl6cx.php

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  10. #10
    Registered User HSV Senator's Avatar
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    Quote Originally Posted by Fondles View Post
    I've not heard of that brand before, will do some research! Thanks!
    Holden Monaro CV8-R
    Lexus IS250

  11. #11
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    OK, Got you now.
    I think it's unlikely that the rear speakers and subs are driven off a single channel per side. The factory amp you mention will only be powering the subs.
    Keep in mind going from 2 to 4 ohm impedance isn't going to cause any problems anyway, the amplifier will just be delivering less power. P=V^2/R.
    Going the other way, you need to check the amplifier is 2 ohm stable.
    The only issue I can see is if the rear speakers really are 2 ohm, and your alpine amp isn't 2 ohm stable. But the way I read it this is how you have it hooked up now anyway?
    Summary: Put new 4 ohm speakers in, will be fine.

  12. #12
    Registered User HSV Senator's Avatar
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    Quote Originally Posted by R31t View Post
    OK, Got you now.
    I think it's unlikely that the rear speakers and subs are driven off a single channel per side. The factory amp you mention will only be powering the subs.
    Keep in mind going from 2 to 4 ohm impedance isn't going to cause any problems anyway, the amplifier will just be delivering less power. P=V^2/R.
    Going the other way, you need to check the amplifier is 2 ohm stable.
    The only issue I can see is if the rear speakers really are 2 ohm, and your alpine amp isn't 2 ohm stable. But the way I read it this is how you have it hooked up now anyway?
    Summary: Put new 4 ohm speakers in, will be fine.
    From what I've read, the amp only runs the subs, the front and rear speakers are run from the HU but the subs/amp are wired into the rear speakers for both 2 ohm sets of speakers/subs to present a 4 ohm load to the factory head unit. I only have a very basic knowledge of car audio so I'm not sure how that works TBH. Although I think its the same for the Alpine HU I have now, I just used an ISO loom for the Alpine first up, then added the Alpine mini amp also using ISO wiring. So it should run the same way as the factory system.
    Holden Monaro CV8-R
    Lexus IS250

  13. #13
    Registered User Grizzler's Avatar
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    The speakers I pulled out of mine have 3 ohms printed on them.

  14. #14
    Registered User HSV Senator's Avatar
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    Quote Originally Posted by Grizzler View Post
    The speakers I pulled out of mine have 3 ohms printed on them.
    Interesting. Is your car a Monaro? This is what's in my car:

    Holden Monaro CV8-R
    Lexus IS250

  15. #15
    Registered User RB30-POWER's Avatar
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    The 6 stacker Premium Stereo fitted to the Calais and GTO/Monaro use 2 ohm speakers front and rear, they aren't wired funny to get 2 ohms, they are native 2 ohm speakers, it's how the system is rated at higher power output then the pov pack model Commodores, the head unit is obviously designed for this however.

    When I upgraded my head unit I had to replace the rear speakers with some cheap 4 ohm speakers because of this, I just wanted to play it safe and not risk overloading the replacement head unit that is suited to 4 ohm speakers only, which most are.

    The rear sub amp is just spliced into the rear speaker wires, so as long as the rear speakers are wired the subs will continue to work.

    I would highly suggest what I have done however, I'm using a 4x100wrms amp to power the front aftermarket splits and the factory subs, the rear speakers I have just powered from the head unit for rear fill.

    The factory subs sound & perform really well for what they are with a proper amp and crossover on them.

  16. #16
    Registered User HSV Senator's Avatar
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    Thanks for your reply RB30 Power. So you are saying that the 2 x 2 ohm rear speakers and 2 x 2 ohm subs are not wired in parallel to present a 4 ohm load to the factory headunit? That's what I've been told a few times now but if that's wrong that changes things. TBH it seemed easy to just replace 2 ohm speakers with 2 ohm speakers (CDT HD6-EX.2 coax). I really don't want to change the existing configuration from the plug and play amp to an external amp, ill probably just rip it all out and go back to stock instead if that's the only option
    Holden Monaro CV8-R
    Lexus IS250

  17. #17
    Registered User RB30-POWER's Avatar
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    Standard Base Model Radio is rated as 80watts (max)
    Level 3 Calais/GTO Radio is rated as 120watts (max) with a 2x70w (max) sub amp, which is how they market the Calais/GTO/HSV models as being a 260watt system.


    If that head unit/amp you are talking about doesn't support 2 ohm speakers,(the website doesn't say if it does when i looked) you will have to upgrade to standard 4 ohm spec speakers - front and rear.

    Subs will not matter as they are driven by the factory amp, the factory amp gets the sound signal from the rear speakers only, this doesn't affect the impedance of the rear speakers in anyway, they will still present as a 2 ohm speaker load to any head unit or amp you wire them too, so if the headunit/amp doesn't support 2 ohm they need to be changed.

  18. #18
    Registered User HSV Senator's Avatar
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    Extremely helpful information RB30, that makes sense. You've saved me making a mistake, thank you.

    So really I just need 4 ohm front and rear speakers to achieve what I want. Subs stay as they are. Alpine HU and Power Pack amp stay as they are.

    Cheers!
    Holden Monaro CV8-R
    Lexus IS250

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