Enough Amp for JL M10IB5?

[steined]

I have a Polk PA D5000.5 Amp - http://www.polkaudio.com/products/pad5000_5 in my boat. I have 3 pair of Polk 6.5" db651s (http://www.polkaudio.com/products/db651) and one set of Polk DB1000 tweeters hooked up to it (http://www.polkaudio.com/products/db1000).

I'd like to add an infinite baffle sub behind the captains chair in my 242 LS.

It looks like I have about 200W RMS @4 ohms for the sub. The sub I am looking at (JL M10IB5-SG-WH) is rated at 250W RMS. (http://www.jlaudio.com/m10ib5-sg-wh-marine-audio-m-series-subwoofer-drivers-91733)

Am in in the ballpark here? I'm guessing I am running my coax and tweeters at 2 ohms right now since I wired them up as they came from the factory. Does that present any issues or complications?

Thanks in advance!

 

[David Analog]

Power ratings are taken with a 14.4 volt supply at 1kHz. 14.4V is unrealistic in a boat.
A brand new, fully charged, lead acid battery will rest at about 12.7 volts after any surface charge from the alternator/stator/shore charger has dissipated and before a load.
Your charging system will generate nearly 14 volts but with any amount of load that voltage will come down quickly.
An unregulated amplifier will lose about 25% of its 14.4V rating with a more plausible 12.5 volt supply, and lose another large % over a wider bandwidth, and lose another large % with all channels driven simultaneously.
Because of this I have used the JL Audio 10" IB M series sub safely with a 340 watt amplifier even though the maximum thermal power rating is 250 watts. I can tell you that it keeps sounding better as it gets more power (to a limit).
Based on ratings, the JL Audio 10" IB MX series is probably a better fit for the 200 watt amplifier rating at a 4-ohm load. But I also give the amplifier credit for some good headroom since you are running a conservative load with an amplifier that is ultimately capable of producing 500 watts as rated into a 1-ohm load.
The M series will be fine. You just won't be getting 100% of its potential.
You can get the most from the sub by properly tuning it (gain, crossover, etc.) and an IB sub needs to be tuned a little differently than a sealed sub. Get with Odin @ Earmark Marine as he will walk his customers through the best tuning process. He has an extensive audio background.
As for the rest of the load, with three pair of coaxials and one pair of supplemental tweeters, you will be as low as you can go on the four highpass channels. The tweeters will need to be on the two channels that are driving one coaxial each so the load is equally distributed. So four channels will be driven at the lowest safe load and one mono channel will be driven conservatively. That's good. I wouldn't want to drive a single-chassis multi-channel amplifier to the lowest load across every channel in the hot July and August afternoons.