Looking for some advice. Currently have the typical OEM system in the boat. Sony head with CD, two 6.5" JBL 3 ways in the cuddy forward bulkhead pointing back, same speakers under the bench seat facing forward. I would like to add a sub. I don't want the thudding sound heard in my kids cars. Just want to enhance the bass. Can I add one 10" sub under the bench in the center. Should it be enclosed or free air. How much power? Will I then need to add an amp for the head unit to keep up. Is there one amp that does both? Once I do this will I need to add an additional battery? I know there are many on this board who have gone thru this. What did you guys do?
Thanks, Dave

You will have to add an amp to power the sub. Your head unit will only have enough power for your 4 other speakers. Subs use a lot more power. The amount of bass all depends on how much power you have going to the sub. The more power the more boom! As far as enclosed or free air depends on the style of sub you buy. I have 4 x 10" JL Audio subs that can been seen across the front of my rear bench. What kind of boat do you have? Once motor or two? Do you currently have one battery or two?

Free-airs will be easier and require less power. As for how much power, give the speakers what they're rated for, no less! Very important!

This is the kind of info I'm looking for! Boat is a 21' Four Wynns Liberator. One battery, group 30. I was thinking free air sub but want to make sure they have decent sound quality. I knew the sub would need it's own amp, but not sure if the other speakers would need one too so the sub does not over power them. Again is there one amp that will do both?
Thanks, Dave

Just do something like this

Yes you can get a 5 ch amp to power the 4 speakers and the sub.
And give the speakers clean power.

Get a 4 channel amp that you can bridge 2 channel on. run the cabin speakers off the head unit power, the cockpit speakers off 2 channel on the amp and the sub off the other 2 channels bridged.

I would also install an additional battery and battery switch.

the 5/4 channel amp is a very good way of adding power to your system. chances are your stock 6.5's will like the added power. I upgraded my system in my old boat to something like you are asking about. However, i used 3 subs and 2 amps...1 sub amp...1 mid/highs amp. You really have a lot of options here. My install was pretty straightforward because i didn't have to cut up any of the original boat. Post a pic, there's a lot of members on here with really good ideas. BTW my subs were (3) 8". One last thing to remember, even less adequate speakers will sound a lot better with good clean power from a quality amp. Good luck.

I have 2 JL Audio free air subs. While they sound good, they don't have the bass a box sub does. A buddy has a Bazzooka tube under his rear bench seat. I think it sounds alot better than my JL's.

ive got the new clarion water proof head unit, 2 sets of clarion 6.5" speakers, and 1 set of clarion 10" speakers i will sell for 500$ plus shipping

go to clarions web page and you can see what they are worth, the head unit alone is 300+, i bough tthem for my boat that was a race boat, and decided not to put them in for resale purpose