Expert: Cleggsan - 8/30/2009

Question
QUESTION: i have 2 Rockford Punch 12 inch subs, one is a HE2 and the other is an HX2, the amp i was given was an Alpine MRV-F407. I was not able to figure out if it is big enough for the 2 subs or if i have to go out and buy another amp, if so what one would your recommend for the 2 subs.

ANSWER: The Alpine is a 4 channel amp or it can be bridged for 160w x2 at 4 ohms.

The Rockford speakers are DVC 4 ohms.  Which means they must be wired either in series or parallel.  In parallel it becomes a 3 ohm load; in series it becomes an 8 ohm load.

So, you must determine how to wire them for proper impedance loading on the amp.  If the load is too low in impedance it will damage the amp.  If you wire the voice coils in parallel and put it on one of the bridged amps you will be in danger because the speaker is now 2 ohms and the amp bridge likes to see 4 ohm minimum.

A single amp, non-bridged, can take a 4 ohm load, but it will only provide an 80W output.

The Rockfords are only 86db sensitivity - which is quite low.  Depending on how much SPL you want to get out of them, the 80 watt input will not give you gut shaking power.  

so, based on that you should try the Alpine alone and if not sufficient, you may need a stronger amp.

The amp you have, also, is not configured correctly.  You need a good two channel amp that will drive a 2 ohm load.  Then connect one speaker to one channel.  You need a good 200w to 400w amp to drive these Rockfords to a respective level (unless you are only listening to background music).

Also, if you put really big amps in your car you have to think about adding a high output generator to keep the battery charged.

Good Luck,

C


---------- FOLLOW-UP ----------

QUESTION: Thanks, i was looking in to different amps and wasn't sure what to look at but now i think i have a good idea on what to look for.

the Rockford Punch 2-channel Amp-P650.2 seems like a good fit by me, i just wanted to make sure i was making some what of a right decision on that choice

Answer
Well, it is a fine amplifier.  Little pricey.  It is an AB design which means it will run a little warmer and use a little more power from the battery than a class D.

For a subwoofer drive where low distortion is not the most important thing in the world it may be good to just check out a couple of class D designs to see the comparison.

You should get one that has the crossover built in for convenience.  They are, generally, a little cheaper than the pricey stuff - and for sub drives they work good .

Best wishes,

C