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CLU61
07-09-2010, 08:45 PM
Hi All,

this is my first post having just sold my R34 GTR (dirty words around here?) and buying a silver VE R8.

I'm loving the torque and the general level of comfort, however the stock ICE isn't quite cutting the mustard. I've perused the thread about adjusting the OEM amp gain and will give that a go (once I work out how to get boot liner out without breaking something!), however that will just be a band-aid approach and I'm sure I'll want more very soon.

I have some amps that I took out of my last car which I'd like to put into the R8. I have a few questions, please forgive what may be 'noob' queries.

1. I am told that with no RCA pre-outs, the OEM head unit requires some sort of converter which amplifies the signal from the speaker outs at the rear of the unit and allows amps to be hooked up properly. The converter at Autobarn was about $300 and I was told with that running the amps would perform as well as if they were running ofrom an aftermarket head unit. Sound about right?
2. It would seem replacing the OEM head unit will be far too hard given that the MFD runs the cimate control etc - I was made aware of some options such as an add-on, smaller MFD to run the climate control, however requires a lot of stuffing around and doesn't look very good. Has anyone out there replaced the OEM unit with an aftermarket and if so what did you do about running climate control etc?
3. As mentioned above, I want to try increasing the gain on the OEM amp, having looked at the pics of where the amp and knob are, I assume everyone that's done it had to take the liner off to access it? I've tried sticking my hand down with liner on and it would definitely appear to be impossible to adjust unless you're double jointed or Inspector Gadget...

Thanks
Jon

Simonk
07-09-2010, 09:46 PM
This is something I'm hoping to do shortly if I can only find the time. Check that your amps you're going to put in don't have high level input before you go buying an RCA converter. If it has them it means you can plug in the speaker wires from the stereo straight into the amp for the input signal

forget about changing your head unit. I think it can technically be done bit really no worth it.

On the left of the boot, grab the carpet at the top and just pull it down. It's held there by a plug which will just pop out. You can then pull the carpet back far enough to get your hand in there. The gain knob is on the bottom edge of the amp. You will be able to reach over the top of the amp to get to it. I found that although you get more bass out of the subs, they distorted way too early and vibrated a lot so I turned them back down.

CLU61
07-09-2010, 10:17 PM
Thanks Simon

My amps aren't anything amazing, a JVC KS-AX3002 (65W x 2 at 4 ohms, 90W x 2 at 2 ohms, 130W x 1 at 4 ohms bridged) and a Pioneer monoblock GM-D7400M (rated 200W x 1 (4 O)/ 400W x 1 (2 O) continuous power 400W x 1 (4 O)/ 800W x 1 (2 O) max. power), but I'll get nothing for them in a private sale so was hoping to use the JVC to run some splits in the front, and wasn't sure whether the Pioneer amp (which previously was running 1 x 12inch Pioneer sub) would run the 2 x 8s or can a monoblock only run one sub? If not may have to buy a new amp to run the subs (prob buy some reasonable aftermarket 8's).

The JVC has a white 6 pin plug connection on the side marked 'high level input' and the Pioneer has a switch marked 'input' which toggles between 'RCA' and 'speaker'.

SO assuming my amps, or whatever amp I buy, has this high level input capability, does that mean they can be set up to run and perform as well as they would from an aftermarket head unit without the converter? Not sure if it was a sales pitch but the way it was explained to me, I need the converter to boost the signal to have the amps and speakers they're running perform to their optimum?

Thanks for your assistance guys.

gunsrunner
11-09-2010, 02:47 PM
CLU61 it is exactly the opposite.
The speaker out from the head unit is to much and needs to be converted to line level, which is around 200 millivolts to 5volts depending on amps.

The problem with this is that the signal has already been amplified by the head unit, then through a converter (Amp or external) to de-amplify then through another amp to re-amplify.

All of this leads to a bad signal to noise ratio, so you can never expect it to be as good as a high quality after market unit that sends 4-5 volts straight to the amp inputs.

There are a range of line level converters ranging from $20 - $1000 but they still have the inherant problem of signal to noise.

On the subject of running two subs on one output.
Your monoblock would output 200wrms per sub, if you use 4ohm subs in parrallel.

Most car amplifiers can be loaded down to 2ohms, but may get hot.
If you run two 4ohm subs in parrallel (ie:+ to + | - to -) you get a 2ohm load.
In series (ie:+ to - | - to +) you get 8ohms.

You can also bridge two channels together on some amps, but the amp will only see half the impedance(ohms)
So if you join two 4ohm subs in parrallel for a 2ohm load, then bridge two channels of an amp to make one channel to drive these subs the amp would see a 1ohm load and probably burn out, get hot and cut out, not good.

CLU61
12-09-2010, 03:30 PM
CLU61 it is exactly the opposite.
The speaker out from the head unit is to much and needs to be converted to line level, which is around 200 millivolts to 5volts depending on amps.

The problem with this is that the signal has already been amplified by the head unit, then through a converter (Amp or external) to de-amplify then through another amp to re-amplify.

All of this leads to a bad signal to noise ratio, so you can never expect it to be as good as a high quality after market unit that sends 4-5 volts straight to the amp inputs.

There are a range of line level converters ranging from $20 - $1000 but they still have the inherant problem of signal to noise.

On the subject of running two subs on one output.
Your monoblock would output 200wrms per sub, if you use 4ohm subs in parrallel.

Most car amplifiers can be loaded down to 2ohms, but may get hot.
If you run two 4ohm subs in parrallel (ie:+ to + | - to -) you get a 2ohm load.
In series (ie:+ to - | - to +) you get 8ohms.

You can also bridge two channels together on some amps, but the amp will only see half the impedance(ohms)
So if you join two 4ohm subs in parrallel for a 2ohm load, then bridge two channels of an amp to make one channel to drive these subs the amp would see a 1ohm load and probably burn out, get hot and cut out, not good.

Thanks Gunsrunner. Yeah that's pretty much what Northfield Car Sound Capalaba told me - it can be done with a converter but quality isn't as good. I'm sure if you buy premium equipment it can be made to sound a whole lot better than the factory system but with my budget I don't think I'll bother for a while.

Might have to look at an exhaust upgrade instead :D

reedy1989
17-09-2010, 10:07 AM
What Size are the Front Speakers in the VE R8/GTS?

Simonk
17-09-2010, 10:22 AM
I haven't seen the fronts yet but the rear doors are 6" so I assume they're the same. I just put some Alpine Type S in the rear which are 6.5" but had to use the adapter that came with the speakers. I've just got them runnning off the head unit and I'm surprised how good they sound. I thought they'd be way under powered but they seem to perform fine. Much better than the stock ones. I'm hoping to put in my Type X in the front in the next couple weeks. I'll definately be amping these though and will be connecting the headunit speaker wires into the high level input of the amp rather than use an RCA converter. I'll keep you all posted on the result on the sound quality. I've never used high level input so we'll see how much signal noise I get.

reedy1989
17-09-2010, 10:50 AM
ahh ok, the fronts look the same as the rear door speaker sizes...i was thinking alpine type-r as have run them in all my cars and cannot fault them...

gunsrunner
19-09-2010, 10:01 PM
yep as stated 6 inch mounts, but 6.5 and 6.75 can fit. Type R and S are the same size, except for the magnet, but there is heaps of room in the VE.
Use some sound dead behind the speakers to get the best responce and seal the speaker properly.
Only had the GTS for a couple of weeks and still need to get the steza out of the Munro, before i can get started.
Dyn Audio GT240s front and rear. Type R 2 x 12 for subs.
Alpine MRPF600 and MRPM1000 for amps.
Runs off an Alpine W502 head unit at the moment, hope it sounds ok off the factory unit. Can get Stinger ipod controller(320kbps music only)
4 guage power and monster cable, with a full box of Dynamat Extreme.
Had false floors in all my cars, but might go boxes for the GTS that way i can keep the full sized spare.
Will let you all no what it's like when finished.

Simonk
26-09-2010, 08:40 PM
Well I spent my Saturday morning pulling the car apart and puting in the Type X speakers. I'm running them off a Kenwood amp and using the high level input directly from the factory speaker wires. I found an acc wire behind the headunit to use as a remote lead to switch the amp on and off. The only problem with this is that when you take the key out the front speakers turn off while the rears and centre stay on. Overall though I'm very happy with the result. I don't have any unwanted noise issues which is good. Overall I'm very happy with the result.