# Questions on head unit output wattage



## Andro (Nov 13, 2002)

I'm using a small amp to drive my front speakers. The rear speakers are connected directly to the head unit. (My setup actually sounds better that way.) I'm just worried because I blew my rear separates before when all four of my speakers were living off the head unit's power (without the small amp). It seems my system was underpowered and that's why I bought a small amp to take at least half of the load from the head unit. My Pioneer head unit says it has 40 x 4 watts of power. That means I get 40 watts going to each of my 4 speakers, right? If I connect only two speakers to the head unit, how much power will go to each of the two speakers? Will it be 80 x 2?


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## samo (Apr 30, 2002)

First of all, never, ever believe the power output listed on any piece of audio equipment. They always list peak power, not RMS, and peak is a basically meaningless number. It will be a cold day in hell before your deck puts out anywhere near its peak power. A more accurate figure is RMS power. RMS is generally about half of what peak power is listed at. Your deck probably puts out about 18-22W RMS per channel. This is the kind of power your speakers are seeing. You will get about 20W to each speaker. If you only use two channels, you will still only get ~20W per channel.


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## scrappy (Jun 30, 2002)

that true only about halfo of the peak power I have a 50X4 and I only get 23 rms


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## SentraStyleEMW (Aug 15, 2002)

scrappy said:


> *that true only about halfo of the peak power I have a 50X4 and I only get 23 rms *


And lets not forget the THD (Total Harmonic Distortion) level of that 23 watts rms...most heads are usually around 1% or so...regaurdless of what the specs say. That's a night and day difference between most amps' .08% THD.


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## Andro (Nov 13, 2002)

So why does the illumination on my head unit become dim whenever I play my stereo loud? It, like, blinks whenever the bass hits.


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## McLaren F1 2003 (Jan 2, 2003)

if i am not mistaken, thats because your system is pullin more power than the alternator can supply at that moment...so the system starts pulling power from the battery


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## Project200sx (Aug 22, 2002)

If you upgrade your battery you should no longer have this problem, go for a drycell, redtop or yellowtop. expensive but it will fix your problem. also your speakers may have blown before because of this, it created a lack of power which can blow a speaker.


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## ImportCarTuner (Jun 9, 2002)

Project200sx said:


> *If you upgrade your battery you should no longer have this problem, go for a drycell, redtop or yellowtop.*


 Along with a new battery, you probably should get a capacitor...


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## Binger (Aug 29, 2002)

*headunit and stuff*

Also keep in mind that the signal from your headunits amp will start to clip way before your amp thats runing the front speakers, so you very well could wind up damaging those speakers again if you turn it up to loud. Also the amp in the headunit is a 4 channel so just hooking up the rear speakers does not increase the power to them. If you try to mono a headunit you will lower the impedence way to much and probably destroy everything.


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