This is a quote taken from Future Shop in regards to what Pre-outs are. Is there any validity to the line I put in bold? A head-unit with a pair of pre-outs, one used for the fronts, and one for the subwoofer... Will the head-unit automatically use the power that would be for the fronts and reroute it to put more power to the rears?

 

That line is missleading. It seems to be saying that if you used the preouts to a amp for your fronts you could then hook up your rear speakers to all of the speaker leads(front and rear) from the deck and get more power. That would in effect be bridging the front and rear channels together in parallel. I wouldn't try that if i was you. If you use the front speakers on an amp and run the rear speakers of the deck, the deck will not make more power, it just wont have to work as hard to make power for only the rear. If you could give the actual link it self it would be helpful cause the web site is often wrong about the real technical stuff and we have to have it corrected.

 

That's why I questioned it. I've never heard that before. Physically, it could be possible, no? I mean if there was a switch on the body of the head-unit, that you could select what the pre-amps were being used for. If you could set it for Front and Sub, then internally it could supply more power to the rear. Of course, it would have to be designed that way...
Anyway, here's the link
javascriptpenWindow('http://www.futureshop.ca/catalog/glossarydisplay.asp?sku_Id=0665000FS10098908&logon =&langid=EN##%20Of%20Pre-Out%20In%20Pairs%20%20%20')

 

that link isnt working for me. I'll try to find it on my own though

 

http://www.futureshop.ca/catalog/glossarydisplay.asp?sku_Id=0665000FS10098908&logon =&langid=EN##%20Of%20Pre-Out%20In%20Pairs

That's what you're looking for. I meant to edit my original response but got held up playing NHL09...

 

If I had a head-unit that I was connecting the rear pre-out to the subwoofer line input on an amplifier with properly set low-pass filters, on my left.
And on my right, I had an identical amplifier that was getting its sub line input from a dedicated subwoofer pre-out at the head-unit - would there be any difference in the reproduction of the bass?
Is having a dedicated sub pre-out going to result in better bass compared to a setup that was using the rear pre-out for the subwoofer?
I guess you'd just have to be more careful when using the rear pre-out since there's no filtering done at the head-unit, and if you don't use the LPF correctly at the amp to remove the higher frequencies, than you could damage to subwoofer.

 

Maybe they are trying to talk about the feature found on even low end Pioneer decks where you can set the rears to be non fading and use them for sub output?

 

Unless the deck has some additional processing or more/less voltage on the sub out, then no there would be no difference.

 

Depends on the head unit and filter settings. If the head unit had a built in subout filter which was the same type, order and frequency as your amp's filter, then there would be no diference. Otherwise you could have phase issues.

You've basically answered your own question. A sub output gives you options and flexibility, it's not a necessity.

 

Thanks for the link. That statement is just plan wrong. I'm not sure what their trying to say. It's seems that they don't get installers to write that stuff or make the car audio packages cause they always put stuff in the flyer that won't go together.