I have an older cedar creek that HAD the concertone stereo and speakers. The subwoofer always sounded like garbage.
looking into subwoofers i realized that the concertone is a dual subwoofer so it has 4 wires as it has effectively dual cones to drive.
If the retards wired it correctly then it should work ok...but the speaker is (at least in mine) a cheap POS.
I don't like non powered subwoofers..they sound dead. Now my original concertone had a small amp connected to it but still was muffled. Even though the stereo, if it has a subwoofer out, is a powered output...just never seems to sound anywhere near as good as a subwoofer with an external amp. They just have to cram too much in to the rv stereos small space to get a good sub amp out I think.
But back to yours...if they wired it correctly is the question...one set of wires should be like a solid color with the other being the same color with a stripe. Like say yellow and then yellow black and that should go to one cone and the other set to the other cone. Problem on mine was the speaker wires going to the subwoofer were just two red and two blacks while the stereo side was marked. So I had to fiddle around and play swap wires until I got ONE cone working good...basically one of the subwoofer speakers sounding ok. You may want to do this. But maybe you are lucky and the speaker wires are all 4 color coded and not just two red and two black on the speaker side.
Long term best bet is go buy a powered subwoofer and hide it in the cabinet if you can. Mine is behind the fireplace. I bought a small powered subwoofer with built in amp at wally world. Works great...not like we are trying to blow away the campground just trying to get some good bass since the regular speakers have none.
But check the wiring first...and you dont have to use both sets of wires. Try just using one subwoofer output and see if you can get it to sound decent first. They may have the two outputs crossed going to the speaker.
These people who wire these up are the single most retarded group of people I have ever met...seriously they suck and have for years...cause the new ones still have many problems with poorly wired stereo and tv.
I only hooked up one cone on my concertone cause both hooked up was too muddy. I run the concertone on one subwoofer output and the powered one on the second output.
Lastly it is possible there is a wiring issue between the stereo and speaker...maybe a screw driven through a wire...possible. If all else fails drop the speaker, if it is a ceiling one, wire it direct to the stereo or us a short run of speaker wire and check again.
Thats just my experience...