Understanding RMS, The Head Unit & Speakers

  • I've been searching the internet for an example and understanding of how RMS from your head unit works with the RMS level on your speakers.  I have yet to find a clear example as most talk about amps and woofers.  

    Currently I have a Pioneer DEH-X6600BT (www.crutchfield.com/.../Pioneer-DEH-X6600BT.html) [14 w RMS x 4 channels 4 ohm] which I recently replaced in my 2003 Honda Civic.  It was recommended by a rep on this website to purchase these 2 speaker sets as I blew out the old factory speakers last week.  Polk Audio DXi651s for the front (power range: 6-55 watts RMS (165 watts peak power)) & Sound Ordnance™ P-69 for the back (power range: 2-55 watts RMS (110 watts peak power)).  

    Is my sound level capped because my Head Unit only puts out 14 RMS while each speaker can handle up to 55?  Is this bad? Does it even matter? Any help in understanding this I would greatly appreciate :)

    Thanks for your help!

  • Yes and no.

    Yes, you will be limited on just how loud the speakers can play off the HU's 14RMS and due to this lack of power, not to mention the design f the HU's internal amp, the speakers will distort before you even reach full volume with the stereo.

    Now, is that to say that the 14RMS isn't enough to get you adequate output from the speakers? No. You should in fact be able to get acceptable volume levels while retaining clear output with mere HU power. If the factory stereo system was loud enough for you back when it was working properly, then this new setup should suffice as well. There may well be a reduction in lower output though, but that's common with unamped aftermarket speakers compared to factory.

    So, is it bad? No, the setup will still work, just not at it's full potential.

    Does it matter? Depends on what you are seeking from the setup. If you are wanting just as much low end or more than what the factory setup produced, you may want to get an amplifier for the speakers or even add a dedicated subwoofer.

    Best advice I can give you, install the setup and give it a go, then upgrade as you see fit.

    Well, I guess that if you have enough concerns, you could buy a 4-channel amplifier to install now as well, which you can use to power all the speakers and later use to power just the front and a subwoofer in the back if you find a need to deeper/richer or flat out more bass.

    A good amplifier could be the Alpine MRP-F300 or even the SO M-4050. Either should be able to feed the speakers around 50RMS and then if you see fit, you could run the rears off the HU and use the rear channels bridged to power a 150RMS sub setup.

    Oh, and a good website to learn a little is BCAE1, there's a lot of useful and informative information there.