Bridging Head Unit?

[Chingon]

I think I know the answer already, but not why...

Anyway, why would it be a bad idea to bridge 2 channels... (say the rear) or 4 channels (all to the front) in a head unit's amp?

Is 35-40 watts ample power for components up front? I'm thinking of some polk dx6510 (6.5 and 1" tweet). I don't want it to win competitions, I'm more focused on sound quality... Is it better to power these w/the head unit's amp 35 watt (nakamichi cd40) or 40 watt denon amp?

I also have a rockford fosgate amp I don't really want to use, but if the pre-amp outputs have a clean signal (as I hope they will), will an amp **** it uP if I defeat the crossover? I've heard fosgates tend to go bassy even after defeating the xover...

Modified by Chingon at 4:14 AM 4/12/2005
Modified by Chingon at 4:55 AM 4/12/2005

[PoorManQ45]

Psshh, psssh, hey you there. You wanna buy some green. YOu look like you've been smnoking a bit already.

Just messin with ya.

I say upgrade to a Nakamichi CD-400 from http://www.cbrstereo.com . It's pretty cheap, pricewise.

Amyways, the power you're talking will NOT be enough for components. I hate them. THey are so god darn inefficient and there's no excuse for it. They require at least 75w RMS each!

[Simmsled]

NEVER BRIDGE HEADUNIT AMPS!!!!!! FIRE WILL OCCUR!!! Not a good thing. If you have a Denon 40w 2ch... that is sweet. Those things are SO clean, use it.

[PoorManQ45]

I've read the article about why you shouldn't bridge HU outputs, but it didn't really make sense. It said that some how the positive and negative signals would get crossed. I don't see how that's possible when the HU is run in MONO with the front/rear amps playing the EXACT same thing.

What about strapping the amps? Is that pheasable?

THanks for the input Simmsled, you da man

[GaNITE]

Most head units have outputs that are designed for driving 2 to 4 speakers. These outputs provide the audio output power to drive the speakers. The power from a high power head unit is actually limited by battery voltage to about 20 watts per 4 ohm speaker. All of the manufacturers that say their head units can produce 30 or more watts of real power are full of ****. On "high power" units, the internal audio amplifier will most likely be damaged if a speaker output wire is allowed to contact anything except a speaker terminal, even if the volume is not turned up. make sure that there is no power to the h/u when making any connections.Most of the head units which are damaged, are damaged due to incorrect connection of the speaker output wires. This is especially true with "high power" h/u's.It IS POSSIBLE to bridge your h/u speaker level outputs, I've seen it done.That said, I'd recommend you don't. If you TRULY desire proper SQ, go with an external amp, quality components(not polk) such as mb quart, boston acoustics, jl, focal(which all come with external x-overs, by the way)....etc, and some QUALITY cables/speaker wires.<--most important step!! that's where your sound is coming through, after all. I also agree in upgrading to the cd400. i have one in my q and the quality for dollar really can't be beat.(plus it's got a 24 bit DAC for under $300!) as for the fosgate.....do you know anyone who would buy it?? just a thought.

good luck in whatever you decide to do......i hope i helped somewhat.

[Simmsled]

What is strapping the amps?

On another note... the rockford amps do work well with highs and mids.

[GaNITE]

strapping is using 2 amps to power 1 speaker. hopefully you haven't tried this already. most manufacturers will, and i agree, advise against this. all it takes is one surge and you're screwed. DO NOT listen to those who will tell you it's ok as long as you have 2 identical amps set up the same way!!! NOT TRUE! hell, even using a 2 channel amp on a dvc is risky...

[PoorManQ45]

and some QUALITY cables/speaker wires.<--most important step!! that's where your sound is coming through, after all.

You were doing good up until this statement.

The only thing that really matters about the wires is the shielding, which applies mainly to the RCA cables. Even unsheilded cables will do if there arn't any high electrical interference devices nearby, ie Neon transformers. Speaker wire is speaker wire. Copper is copper. As long as the insulation is sealed and oxygen is not allowed in it will be fine. Oh yeah, and it has to be of sufficient gauge.

Most head units have outputs that are designed for driving 2 to 4 speakers. These outputs provide the audio output power to drive the speakers. The power from a high power head unit is actually limited by battery voltage to about 20 watts per 4 ohm speaker. All of the manufacturers that say their head units can produce 30 or more watts of real power are full of ****.

Yep, Head Units do NOT have transformers in them to increase the voltage above that supplied by the electrical system.

[audtatious]

"Back in the day", Sony used to supply external amps for their headunits instead of internal amps. These were small metal boxes with 4 RCA inputs and 4-pair outputs. Rated at 11x4 and had a bridging switch for 22x2. Buddy of mine ran it at 1 ohm bridged for 6 months (2ea RF SP54 in parallel with 1ea RF 4" + RF tweeter in parallel with the mids in parallel = 1ohm). Damn thing never blew up. I actually still have that amp and use it today to bench test speakers.

[PoorManQ45]

Ah, a tribute to SOny's good ol' days. Unfortunately if you try that with their new amps what will happen is described in my Sig.