Hello All,
Long time reader, first time poster. I purchase a 2010 F150 XLT CC about a month ago and I am loving the truck, all aspects except the speakers that is. It all started out by me just wanting to replace the door speakers. Then it advanced to 'well if I add door speakers maybe I should amp them' then my sickness advanced further to 'if I add an amp it wont take that much more to add a sub'. As I have been researching this stuff I realized I also want a sound processor because I want to keep my factory head unit with MS Sync. Ok long intro but here is my question. The amp I am seriously considering is the Crunch P5000 5-channel amp. My door speakers will be replaced by Infinty Kappa 62.9i and I was offered a good price on a Rockford Fosgate P1S810 at the stereo shop tonight. But in looking at everything I see the amp is rated as follows: 4 x 125 + 1 x 300 @ 4-Ohms 4 x 200 + 1 x 500 @ 2-Ohms Maxx and then when I look at the specs for the sub I was offered a good price on I see its specs say the impedance is 8 ohms. Does it matter that the amp is rated at 4 ohms and the sub at 8 ohms? Thanks in advance for any help.

 

General rule of thumb: increasing the amount of resistance (ohms) on your subs won't hurt your amplifier. You find out at what the smaller amount of resistance your amp is stable at (let's say 2 ohms, in your case), and then you can use any sub combination that gives you >= 2 ohms.

So, essentially, you won't hurt the sub or amp by going that route based on the expected output of the amp at 8 ohms and the power handling of the sub (both at 150 watts).

HOWEVER, doing this would essentially be wasting your amplifier, and probably would not produce the amount of bass you are seeking. You should find a subwoofer that is more inline with the specs advertised with the amp. Either a 300 watt 4 ohm subwoofer, or a 500 watt 2 ohm subwoofer. I personally would try to get a 2 ohm subwoofer to really make use of the amp.

Keep in mind, though, that there are things called dual voice coil (DVC) subwoofers that offer for flexible wiring options. For instance, a DVC subwoofer with each voice coil offering 4 ohms of resistance could either give you 2 or 8 ohms of total resistance depending on whether you wire the voice coils in parallel or series, respectively. Likewise, you could, in theory, make use of that RF subwoofer at 2 ohms if you bought 4 of them and wired them in parallel. But you probably don't have the room for that.

 

Hey I'm not here to preach but I've heard the amp play and Bench tested it and they dont put out more than 800Watts.

That Subwoofer channel at 2 ohms would give you about 200-300 watts at most. So it might still work perfectly for your situation. in order to get to a 2ohm load with you subwoofer is by either buying 2 (Single Voice-coil 100-150rms watt) 4ohm subwoofers or 1 (Dual Voice-coil 150-300rms watt) 4ohm subwoofer {both setups are able to be wired parallel to 2 ohms}... in able to get the best performance from your that amp... dont waste your time with Dual 2ohm or single 8ohm. Because if you think you're getting too much bass. Just turn the Bass down. Alot of people dont understand that. And there's sometimes you might wanna show off or just want more bass and so turn it up a little.

The Door Speaker Channels. Also are not actually 100watts @ 4ohms or 200watts @2ohms. alot of door speakers are 4ohms so Stay in that 40-100watts rms range and you should be pretty satisfied as long as you're not trying to compete with anybody.

 

Crunch amps are gargabe in my opinion...dont waste your time