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Discussion Starter #1 (Edited)
Ok, next question:

Assuming a Mopar head unit in the dash (RBQ or RB4) and that the stock Infinity amp/speakers will be bypassed/replaced.

Which of these configs would give me cleaner sound from the new aftermarket amps and speakers:

a) putting a HiLo converter right behind the head unit and feed low signal to the new amps.

b) running the speaker-high outputs from the Mopar head to the high-level inputs on the new amps.

I'm leaning toward a) based on other discussion.

Length of cable runs: the amp for the front speakers will be under the dash. The amp for the rear speakers will be in the rear trim panels.

The rear amp will feed the back speakers directly. The front amp will hit crossovers to split highs and mid-lows and then feed the sail and door positions.

The first install will be in the SOs Liberty. If that works out (sorry honey!) I'll do the same to the trep.
 

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If the amplifier has its own speaker level inputs, then typically you will get better performance from using those than by using an external LOC. As for the amps you may want to reconsider their mounting locations. Up under the dash isn't a very ventilated location, nor is under the rear deck (assuming it will be mounted inverted)...
 

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Discussion Starter #3 (Edited)
The amps I'm looking at have optional clip-on cooling fans and will be pumping about 150w per channel. No big subs, no 0 gauge wire, no 1fd cap, pretty vanilla install other than running at almost 10x the per-channel spec of the factory head. I think that the RBQ and RB4 run at 16 watts/ch RMS into 4 ohms, the Infinity amp runs that up to something like 30 w/ch RMS into 2 ohms.

The rationale for the amp locations is to keep the overall cable runs as short as possible and to use well-shielded low-level cable to run signal.

But if you're telling me that I won't gain anything by using a HiLo converter the strategy changes somewhat.

I should be able to run the signal from the factory head back to the current Infinity amp location using the factory harness and then branch out to the new amps. From there run heavier speaker wire from that location to the 6 speakers.

This keeps from splicing into the under-dash wiring (or making a custom plug-in harness) for the front speakers/amps but requires that I run speaker wire forward through the sills to the front speakers. Having a pair of 300 watt amps in the rear might be justification for a dedicated, fused relay-controlled power and ground run in the 8 gauge range.

Why settle on using amps rated at 2x 150 watts? That seems to be the "price break" (for both amps and speakers) between what is a nice power and quality upgrade and the beginnings of outrageous $$ and power.

Of course there is no way that I'll be doing any of this until I get a string of 40-50 degree days, installing car audio outdoors in a Minnesota Winter is just plain stoopid. So there is plenty of time to think the kinks out of the design.
 

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Running speaker level signals through the car is much better than running RCA line level signals through the car. The higher voltage lines have a lower risk of noise induction than the low voltage RCA lines. The reason all systems don't do this is because pre-outs provide better quality signals than post amplified ones (the headunit amplifier adds a lot unwanted THD+N, etc.). However, since your system has no pre-outs directly from the headunit, you might as well use it to your advantage and keep the level conversion all inside the amplifier itself. Short cables runs are always better than long runs, but honestly, I don't think the benefit is worth the extra work.

As for the amps, assuming they are 150W x 2 RMS, I'd want 4 gauge running to the trunk. You don't need this to be relay switched, just make sure it's fused at the battery. The amplifiers have their own internal switching to keep them powered down when the headunit is off...
 
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