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8" sub into AU

3K views 18 replies 5 participants last post by  JC-XR8 
#1 ·
There is a hole in the parcel shelf in my AU that will take an 8" sub. I do NOT want to upgrade any other speakers and I want to keep the standard Ford Head Unit. Any suggestions on how I add the sub to this system? I've thought about running it in parallel off the left or right rear speaker, but I'm not sure that this would end up putting out much more bass.

Do I need an amp? If so, 2 or 4 channel and how would I connect it? I know I could use an RCA converter running from the rear speaker wires, but how do I then run the rear speakers AND the sub?

Any and all help gratefully appreciated. Thanks in Advance.
 
#2 ·
The simplest way to do this is to run an amp with high (speaker) level inputs, then just use wire taps to wire the inputs parralell to one of the existing rear speakers.

As far as amps go, you only need 1 channel, however you can buy an amp with as many channels as you like and run it in bridged mode.

The AU head units do not have RCA outputs.

The only cable you will need to run is 12V to the boot for the amp.
 
#3 ·
AUForte - Thanks for that. I was kind of thinking that's the way to go. I'm going to buy a 4 channel amp on the weekend and hook it up to the front speakers (I got new 5X7 pioneers for $140) and the sub. I'll leave the rears running from the head unit as you can hardly hear them anyway, without putting a lot of rear fade control to them.

I'll post the results here - and any further questions as they arise!
 
#4 ·
Good into JCV8

Post back how you go because I'm thinking of doing the same thing. Blakpunt (spelt something like that) decks can be hooked up to the steering controld for the AU if you are interested. I'm thinking of keeping the original deck (CD Futura deck) and running a 8" sub and different rears. Are the rears in the AU 5X7 not 6X9?
 
#5 ·
Apparently they are 5x7 all round - but check first. I haven't looked at the rears (not theor size anyway). I'm just about to go and do the amp now, so i should have results tomorrow (8/12/02). Good to know about the blaupunkt (?) - I'll keep it in mind if I ever get the money to replace the Ford Cd Head Unit.
 
#7 ·
I had already installed the front speakers (new pioneers) and they were really good. I have n9ow installed the amp to run the fronts plus the 8" sub. I now get a small 'click' when I turn the car on. When I actually start it, I get a whining through the speakers. If I turn the car off (ie back to accessories), the radio sounds pretty good. I can clearly hear the sub, which is what I wanted.

Anyone know how to eleiminate the whining through the speakers when the car is on? The instructions for the amp said to install an alternator filter - what the hell is that? And do they work? Has anyone else had to install one of these?
 
#8 ·
JCV8 said:
I had already installed the front speakers (new pioneers) and they were really good. I have n9ow installed the amp to run the fronts plus the 8" sub. I now get a small 'click' when I turn the car on.

If you turn your head unit off, wait a few mins and then turn it on, do you get a pop/click through the speakers ? If that's the problem keep reading (otherwise disregard the following). Some amps have a built in delay to fix this problem, in that when they detect voltage on the remote wire, they won't give power to the speakers straight away which elimiates the turn-on "pop" sound. afaik Jaycar used to sell something that you put on the remote wire which would add the delay to the amp. Maybe ask them ?

JCV8 said:
When I actually start it, I get a whining through the speakers. If I turn the car off (ie back to accessories), the radio sounds pretty good. I can clearly hear the sub, which is what I wanted.
Bugger, there's plenty of reasons why this can happen.

- Start by checking your various ground connections, and then recheck them. Are they all making good solid contact ? In the case of the amp, is it grounded on bare metal on the chasis (ie. grounding the wire on a painted surface is generally not good enough imho).
- At the battery make sure the terminals are making good contact as well.
- Check you gain settings (ie. try lowering them and seeing if this makes a difference)
- Trace the path of the speaker & rca wires and make sure there's no shorts occuring along the path
- How are you running the speaker wires, rca wires and power wires. e.g. rca's and speaker wire are run up left hand side and power wire running up right hand side? Or are they all running up one side etc ??

Aside from that, CAA will give you more comprehensive troubleshooting info: www.caraudioaustralia.com and click the "technical" button, they have a few guides relevant for this kind of problem. Or consider joining the forums there and posting a question.

The instructions for the amp said to install an alternator filter - what the hell is that? And do they work? Has anyone else had to install one of these?
Here's a link explaning the concept http://www.avweb.com/articles/altwhine.html (I'm sure if you search google you'll find more useful info). Can't really comment on them cause I've never used one. What I'd suggest though is that they'd seem a more last resort option, because there are plenty of good systems that don't need/make use of them ??
 
#10 ·
Thanks guys. I've checked every connection! I've got the speaker connections running up the middle of the car, and the power running up the drivers side. The ground wire is screwed in to the bare metal behind the back seat. I haven't connected directly to the battery - I did have it to the battery yesterday when I did my original post about the whining, so I changed it to run off the factory Amp connection in the wiring loom, thinking this may fix it - it's still the same!

I think I'll go and see Jaycar and see what they can do - some sort of suppressor sounds like the way to go (the amp is only a cheap one, maybe that has something to do with it).

Again, thanks for the help - I'll post back the results, any fixes and any lessons learned.
 
#11 ·
I rang Jaycar and described the symptoms and they recommended a noise filter - so i went there and bought one. Fitted it, and it's reduced the noise to about half the level. now I also have a constant buzz in the speakers that does not increase with engine revs (I probably couldn't hear it before because the whining noise was so loud.)

I took the car to an audio place and they had a look at the sub - they reckon that the sub is crap (which it is) and that if i actually bought a decent one, it would solve the problem. So that's what I will do - save some more funds and get a decent sub and give this one back to my brother - he didn't have any problems with it in his nissan, so he can have it back, even though he sold the nissan! you get nothing for nothing I suppose.

I have now wired the sub to run off the right front speaker - it's OK, but an Amp would obviously help.
 
#12 ·
Mate, buying a different sub will do nothing to your whining problem, sounds like electrical noise, most probably from the alternator or a poor ground somewhere, suppressors only mask the problem, it's nice to get to the bottom of it, your hum may be a ground loop
 
#16 ·
JCV8 said:
Jaycar suggested I run the ground wire back to negative side of the battery - I did this and it was worse!
It should be sufficient to ground the amp wire on the bare metal chasis in the boot. If you do this try to keep the length of the grounding wire to a minimum. Maybe try experimenting with different ground points in the boot ?

The following is from a thread on CAA:
1. Remove the RCA input from the offending amp and place some shorting plugs across the inputs. If the noise goes away then your amp is fine and the noise is being created further down the line (goto 2). If the noise is still there then its a problem with that amp. Check all power / ground connections again. And speaker wires/terminals shorting to ground. If the noise is still there then you have a dodgy unit or it is poorly designed.

2. Connect the RCA to the amp again but disconnect them from their input ie crossover or HU. Put some shorting plugs on the inputs (or just short the inputs). If the noise appears then your RCAs are the problem. Replace them with some cheap shitty KMart ones and see if you still have the prob. If the noise is not there then its coming from even further down the line.

3. Connect the next device. If its a crossover or processor then remove its RCA inputs and replace them with shorting plugs. If the noise appears again then the processor/xover is the prob. Check its power/ground wires. Some Xovers are known for their noise capabilities. If the noise doesn't appear then reconnect its inputs one by one until the noise reappears.

4. Keep repeating this shorting input process until you find which device/RCA leads are causing the noise.

If you find that your HU is the cause then check all its power/ground connections. If this doesn;'t get rid of the noise you can try a power filter or maybe the unit is faulty.

Remember ground is not ground. The chassis of new cars are often made of alloys. As such they are not necessarily good conductors. You might have to try several different ground points for your amps/HU before you get a good one. If you suspect your HU is the noise source then just disconnectthe RCAs from the HU first and short the ends that goto your amps/processor. This will tell you if its the noise source without working your way back through the amps etc.

To make shorting plugs all you need to do is to buy some cheap RCA plugs from Jaycar/Dicksmith/Tandy and short the two terminals (ie solder a bit of wire from the center pin to the outside pin).
For step (1) you could also try: remove the rca inputs at the amp, and hook up a portable discman (keep the volume low, & amp gains low). then hit play on the discman and listen for the noise,
-If the noise is gone: then suspect the h/u setup or maybe your rcas are picking up the noise ?
- If the noise is still there, suspect the amp setup or speakers. Wire up a different pair of speakers to the amp (or instead of another set of speakers, wire up the sub) and play the discman again. If you still have noise, maybe try moving the amp somewhere else in the boot ? (if possible ?).

The only other thing I can think of atm (which you've prolly already checked): is the gauge of the cables you're using for power & ground sufficient ?

Suggestion: if you're still not getting anywhere consider joining the CAA forums and search for similar problems/symptoms to yours (which there are) or post a question ?
 
#17 ·
Thanks for all the advice. I have tried most of this and I still get the noise even with no input plugged in to the amp at all. The only way to get rid of the noise is to take the fuse out of the fuse holder in the power lead. It could be the power wire I guess, but I'm using 6mm stranded wire for both power and ground wires. The power wire runs the length of the car, while the ground is about a foot long and definitely goes into steel - magnets stick to it!

This all got me to wondering if it could be the output, but when I disconnected the speaker wires from the amp and reconnected them to the HU, the noise disappeared. I'm really thinking that it's the amp ("If the noise is still there then you have a dodgy unit or it is poorly designed"). I disconnected all inputs and all speakers except the sub, and the noise was still there! Even with a filter. I think I'll give up on this amp and get a brand name one installed (I'll do it myself first, and if the noise is still there, i'll get a pro to do it)
 
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