ScoobyDoo555

Well, I'm about to finally install the amps - chrimbo came early :-)))))

Question is, I can't decide how to wire it all in.
The head unit has two line outs (1 front 1 rear)
I was thinking of just running the 4ch amp (doors & rears) on the front, and the 2 ch (sub) off the rear output......

This way I can also maintain control over the bass when I'm at McDonalds (with my Puffer jacket on and Artful Dodger CD <wink>)

Anybody disagree - if so, how would you do it?

Dan

john banks

I bet that premature release of the amps took some amazing bargaining on your behalf!

I was surprised to see that my 4 channel amp would NOT allow alteration of the level of the fronts vs rear (rear channels originally bridged for sub) if it was run off a single pair of line level inputs - although it does allow different filter settings. This was not documented in its manual, and thankfully I still had all the car "in pieces" when I realised this so I could install a 2nd RCA cable. As it was, input sensitivity ended up being max on both channels anyway, and now it is bridged to 2 channels only so it doesn't matter. I now use the other RCA cable to drive my sub amp, which allows the McDonalds style bass adjust (reduction in my case, only NOVABOYS turn it up and their neon lights on). I was relieved to see that my headunit's preouts were fading (although again it was "discovered" rather than documented in the "manual"). I suppose you'll have to set the front/rear balance on the amp then and hope it does allow independent adjustment of level off a single input unlike mine. I suppose if it was a daft set up like my 4 channel you could use a 3rd RCA cable pass through, but presumably not to itself or you would have positive feedback, and if you took the pass through from the sub amp, the level of the amp supplied from the pass through would adjust with the rear preouts from the headunit. DOH! So a "Y" cable may be beneficial in this case. Hopefully your amp design is a bit more thoughtful!

On my system, the rear speakers are off the head unit, and the sub amp is off the rear preouts, so they move together. But I don't notice the change in volume of the rear speakers 'cos the fronts and sub are so much louder

Another potential problem when bridging the sub amp - with ScoobyDoc's present amp it takes only the left channel input and ignores the right, so if there was something bassy on the right you might miss it. Since you are a Sound Engineer, you tell me whether this is significant in normal music... depends on how it is recorded/mixed? My amp uses each channel to make up each half of the bridge though. I suppose a "Y" cable could be used again if necessary. I can't access it from work, but the rec.car.audio faq I think suggested ?1K resistors in the positive lines of two RCA cables before they were joined, with the grounds just connected together, but I can't be sure. Sounds like something to avoid if possible. You folk with 3 preouts (GOLD FOUR VOLTS etc) must look down with pity on us 2 preout Luddites!

I have waffled too much and probably thought of all sorts of problems you are not going to face, but some of them were problems to me. I hope my amateurish drivel at least sparks your thinking a little

[This message has been edited by john banks (edited 09 December 2000).]

ScoobyDoo555

Cheers John ;-)

The release is purely for quality control - the luck I've had this week (somebody went into the front of the Scoob in the carpark!! - not a week since I've had the rear bumper replaced!), the amp would be knackered - some Xmas present eh?
So, in the meantime, I'm putting everything in to try, and then leave the wiring in for the main install on Xmas Day (No way I'm spending time with the family!!)

Sounds like you had a MAJOR headache when you did your install..... however, practice makes perfect!!LOL!!

Yeh, my head unit has the fade function,so the rears (that are redundant anyway...) will be on the same output as the sub....
This just means a bit of setting up..

Of course, as you say, I've also got the option of 'Y-connecting' the outputs to obtain an output from both outputs, I'll see though - depends on whether I can really be bothered to do it !!!!!

<Another potential problem when bridging the sub amp - with ScoobyDoc's present amp it takes only the left channel input and ignores the right, so if there was something bassy on the right you might miss it. Since you are a Sound Engineer, you tell me whether this is significant in normal music... depends on how it is recorded/mixed? >

From my experience (open to being blown out of the water!!!), the input for the sub, although resulting from just the left channel, doesn't matter, coz generally, it is a mono mix anyway (if you look on most 'musical' instruments, the Left channel is mono )

Just my 2p anyway.....

Dan

john banks

I thought you were going to wire the 4 channel to the front preout, but then you mentioned wiring both sub and rears from rear preout. Anyway, if you agree the rears are redundant, how about trying them off the headunit and bridging your 4 channel to power the fronts. It made a huge difference to my system. But then you may have really posh amps anyway that sound awesome as they are and may have plenty of power to drive your components. My components are rated at 90WRMS, and sound a lot better with 150WRMS from the amp rather than 50! Would be a fairly easy experiment to try to see which you prefer? I was AMAZED at the difference - even the wife thought so, and she usually turns her nose up at these things!

chiark

What you really need is something that takes one RCA and splits into front, rear and sub output with variable front/rear fader and sub level and crossover frequency control. And has a 5 band EQ.

Something like the quarter din Kenwood 4042A, which fits in the ashtray slot (hey chaps, don't go there, right? )

I have one for sale if interested. Car Audio Direct don't have em listed on their website, but I paid around 130 quid a couple of years back.

It's boxed and mint. Let me know if you're interested...

ScoobyDoo555

Sorry John,
Put my brain in gear - that WAS what I was going to do - 4ch amp of front Line Out. 2ch amp of rear Line Out. This way I can fade out the Sub.....

Thanks Chiark, but no thanks!!! My next addition will be a DSP box, but not 'till next year :-)

Cheers guys

Dan

Scooby Doc

Dan

Just read your post

Congratulations. QC is important. You wouldn't want to have your wife trying to find a replacement on Christmas Day

Victory to the boys!!

Martin

ScoobyDoo555

Cheers ScoobyDoc!!!!

I've even gone to the point of clear-heat-shrinking all of the cables (sad I know!!) with I.D tags....
Put the power cable thru the grommet where the A/C should go, and coiled it up behind the carpet. Took the Scoob out for a quick spin (as you do), and Bloooody Hell!!! The noise!!! Amazing what a bit of carpet can do!

Might be time to Dynamat the front and rear!!!

Now all I need to do is get the MDF floor...however, does anybody remember Kenny Everett's 'Handyman Reg'?........ :-0

Dan