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reduced sound out put after replacing o/e bose ?


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Think I may have found a cheaper answer instead of adding pac-rom units.


I recently fitted two stereos, one JVC double din unit to celtic vals car and another pioneer unit to keyser's wifes car.


When fitting the unit to vals car unfortunately the head unit didnt have the necessary rca outputs. With Vals car and the necessity for her to get back to her home and with us having the dash all stripped down i decided to take the gamble and cut the red and white and yellow and black rca ends off of the iso lead set.




After cutting the ends off close to the white sockets at the end of the leads i found the necesary colour coded speaker wires. After soldering these to the high imput speaker wires on the head units plug i refitted the stereo.


I was quite shocked how loud the unit was in comparisson to my sony unit fitted using the correct iso leads ie rca's and the pac-rom units.


I didnt know if it was just the case of the jvc unit being more powerful but with val happy with what i had done we sent her on her way.


Recently i fitted a pioneer unit to Keyser's wife's zed in the same way as val's with the same results in sound quality (loudness).


So tonight i decided to strip my dash down remove my pac-rom units and carry out the same modifications to the loom as above. I am pleased to be able to report that the sound output is tenfold more than it was with the rom units. Hopefully this may be of help.

Edited by buster
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The reason the volume is low is due to low voltage preouts when using the phono leads. Never had this problem with Alpines but when i fitted it to the bose in my Afla GT the adaptor had built in resistors to limit the output to the bose amp to protect it. I removed these as it was to quiet.


This has made me think that the reason they dont use the high level outputs is to protect the bose amp as it wasnt designed to take a high level input.

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First thing I will say is Buster's method works like an absolute charm, great work Buster!


How the day started....


So headed off down the Zed Shed today so Bob could fit my new head unit. It's amazing how far some chocolate cookies, Chocolate ring doughnuts and some allsorted biscuits will get you with Keyser and Buster :lol:


Buster making a start




Keyser playing with his toys in the Zed Shed





Dash/Bose out






Buster tried the Sony unit all connected out of position to make sure that the unit worked etc and to show me the difference of volume. The Sony unit on maximum was terrible and could barely hear it! So without hesitation I wanted Bob to work his magic with his workaround.


Busters quick donut break :snack:




Back to it and Bob snipping a few cables here and there to do his mods :#1:








Getting cable ready for soldering....








Buster using the heat gun on the cables




Head unit back in all connected




Finished job and all the steering wheel controls worked a treat. The Sound difference afterwards was immense, putting the volume up to around 13 out of 50 and that was loud enough! :#1: Compared to how it was before Busters modification has made it crazy loud :yahoo:





All I can say is a HUGE thanks to Bob for changing over the stereo for me and doing the modification and for Keyser letting me come down and annoy him by asking stupid questions :blink: You guys are seriously awesome.


and the final picture :yahoo:



Thanks guys.



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well thankyou for your kind words. :D the idea behind the zed shed was to carry work and make it easier for the non tech people out there who wanted to undertake like work. :D

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  • 2 weeks later...

Bob, you'll need to do a proper guide/tutorial on this.

After reading this several times, I still don't know what cables you snipped and where you actually connected them to.

All I can get is that you are by-passing the Bose amp altogether and going to the speakers directly.

Unless I missed something

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ok .i ll try and explain.


this is not by passing the bose amp in-fact its retaining it and just improving the signal as required.


pretty straight forward to do.you ll need to cut the rca leads off about an inch above the plug exposing the wires ie.white and black and purple and black green and black greey and black.then strip back and match these to the h/unit loom speaker wires.you need to remove the plug from the h/u speaker wire loom....join them together ie purple to purple ,black / purple and black and so on with the others.white to white and black to white/black,green to green and black to green and black,grey to grey and black to grey and black.



hope this help.and you will not need the booster packs but you ll need ear plugs

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Interesting read :) I had the same problems after fitting my Alpine Headunit into the Zed. I've overcome it a different way though - fitted a spare Genesis Profile Four amp I had lying around, its now very loud, better SQ and I have complete control :D


This does make sense though, as when I was looking into all the wiring of the stock Bose amp, Headunit etc. I found that it uses high level outputs from the Headunit to the Amp as standard anyway. So converting it to RCA/Phono is bound to lower the output. I expect the reason the kits are made like this is that its a simple plug & play installation.

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I have done this wiring 'mod' today, and just like Bob (Buster), I'm shocked with the results. My stereo is now seriously LOUD!! :yahoo::yahoo:


I had a HU recently fitted by Halfrauds and although it 'worked', it just wasn't right. All 4 speakers worked and the volume was OK, but something just wasn't right....


So after reading the online guides, I thought I'd pull the HU out to see if I could help improve things.

I won't bore you with the full story, I'll just 'cut to the chase' as it were and cut a long story short.


In a nutshell, you need to cut the below off the loom(s) harness and then match the 8 wires you're left with together.




Once you cut the red, white, black and yellow RCA plugs off, strip the black covering back to reveal two wires underneath it. (In lay-mans terms as I'm no expert at all, the coloured RCA plugs look like they're fed by a thick black wire, but it's just covering 2 thinner wires).


On my harness, once I'd stripped the black covering back, one wire is 'bare' - this is the earth wire, the other insulated wire is coloured and is therefore easy to match with the other wire you've cut. (Match colour to colour and the wire with a black trace is your earth).


The other connector block that is fed by 8 coloured wires is for your speakers. All that is to be done is match the 8 wires together and connect them. I used 'crimps', but they could easily be soldered.


When all was finished, I just had one connector block feeding into the back of the HU (aswell as the mic, steering wheel control and aerial). The RCA plugs are no longer used.


My stereo is an Alpine unit (CDE-W235BT). This mod has made a tremendous change to the sound output and performance as a whole. On the HU, volume 4 is loud, 5 is very loud and 6 was really gonna p*** the neighbours off if I left it that loud whilst refitting everything. I cannot use the 'Loud on/off' function on the HU as just going from 3 - 4 on the volume control makes a massive difference.


Hope this helps.


Cheers, Ian :thumbs:

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  • 2 months later...

I have this same issue with the speakers failing on my OE head unit, but i was thinking of upgrading to an aftermarket unit anyway so not too much of a concern; however i cant say im too keen on the idea of cutting up the wires on a new unit due to the low volume levels.


My question is, do you find these low volume issues on ALL aftermarket head units or just certain brands? can anyone advise any units which wont require rewiring work?



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Not all head units have the low volume problem just some of them. You can buy an inline booster for about £20. Just to confirm that I cut the plugs off due to the fact it was quiet and I only could fit 2 plugs (school boy error) :bangin: Only took 15 min after taking it out and very straight forward. The volume is so much louder. Before i could have it on 50 (max) and talk over it. Now I can't take it above 25 before my ears hurt :lol: . Defo worth doing.

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  • 4 weeks later...
  • 4 months later...

i have just done this to mine as i had poor volume and was very disapointed with the results but now its so much louder a big thanks to all who have posted different things that i have followed, and i have read so many from what was needed to how to do it and now how to improve it again thanks for taking the time to post so that a techo spastic like me that likes to do things himself is very greatful

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I have pointed a few people to this thread in the last week, looks like a lot of people got new HU's for Christmas or just taking advantage of some cracking deals :thumbs:


If you have issues with volume this is the fix, all depends if the HU has adjustable output though, seems a lot of Pioneers have issues, mine did...

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