Boats + Bass

Installed a moderate sized stereo in a family members 34' Larson on the weekend.

Looking for suggestions from the bank of TW audio gurus:

2 x 12" subs in a properly sized sealed box, mated to a properly matched up amplifier. Subs are rated at 250W RMS each, amp puts out 500W RMS. These are car audio subs/box.

The box is just sitting under one of the bench seats, with the subs facing out into the boat. The subs are moving as they should be, the vibrations can be felt in the hull, but the subs just don't sound as loud as they should. Guaranteed if they were in the trunk of a car or in the access cab of my truck, they would be ridiculous.

What's the problem? Why is the sound not carrying?

- should the box be turned around so the subs are pointing at the wall behind the seat, as to sort of mimic them being in a trunk?

- when a sub box is put out in an open area, say as if you were to put a sub box in the bed of your truck for tailgating, should it be a ported box for louder SPL?

Already tried looking this up on marine audio forums but no luck.

Anyone have luck with a sub box in the open bed of a truck? Guess that would be most similar scenario.

 

I would try flipping the box around so the sound can bounce off an object, right now it is just going out into the open.

Just my idea, not a big guru.

 

if you can post some pics of the location, i have done alot of boats, i can tell you some ideas of what to do. Also make sure you didnt inadvertantly reverse the phase of 1 sub.

 

What you're experiencing is the effects of using a car audio sub (housed in a car audio box) in a place that isn't a car. You wouldn't think this makes much of a difference but it makes ALL the difference. Check out the picture I've posted below.




What you're looking at is the low end frequency response gain induced by the cabin of the vehicle; called Cabin Gain. Basically, you have a speaker moving a large amount of air in a small air space. The waves get trapped in the car and can't get out. The structure of the vehicle confines all the sound to that space. Because of this, starting around 45hz and down, you get a significant boost in output. When you're not in the vehicle you get little to no gain. When your HT sub is in the corner of your room in your house you'll get gain too (aptly named corner gain) but it's not as significant as in your car.


I'll bottom line it for you though. I'd imagine you're going to want something with extreme bottom end that is stupid efficient to fill a space like that with sound. I agree with Jigzor, try changing the subs to fire more into the boat instead of out onto the water. You'll get more reflections off the boat that way.

A proper solution would require you to get creative with the enclosures and probably to get more power as well. Could be a good candidate for a horn loaded enclosure or a Karlson.

 

i think ported boxes are louder in a open area

 

I think we will try this first.

The polarity was triple checked. Subs are confirmed to be in proper phase with each other.

Here's a quick visual of where the subs are placed in the boat. Any other suggestions we could try before making any significant changes?

It does make sense.... but not the answer my cousin is going to want to hear . I didn't have any input on the components of the system, I was just the installer. The rest of the speakers/amps sound awesome, just the SPL of the bass is lacking for what it is.


If moving the location around isn't going to make much difference, would a new properly sized ported or band-pass box be the way to go?

 

What subs are you using and what is the enclosure volume?

 

Ported boxes are louder period. They might not be the optimal in all circumstances though.

 

Yep, depends on the type of music you are listening to. Generally you get tighter response from a sealed box vs a ported.

 

ported increses output, digital designs website has all types of charts and box plans with detailed instuctions, definatly the best way i know of to get more bass, i have a single 12 in the full size box and its impressive

 

and ive had subs as long as ive had my licence

 

you could try make a baffling plate to attach over it, that location, in that style boat is the thing that is hurting you.

 

That's a complete myth. And it has been,







Wait for it....













Wait....










Waiiiiiiiiiiiiiiiiiiiiiiit.

 

Also, if these aren't marine subs they might be at risk for cone damage seeing as how there is a gratuitous amount of water being thrown around back there. Do the subs have a paper cone or some sort of poly composite? Paper will take a dump eventually if they get wet. What subs are they?

 

The subs are a big-box-store bough deal. 2 x MTX 12" in MTX's sealed box. The cones are made from poly something or another.

I don't think it's a big concern for moisture in their location. There's about a 1.5' deck of the back, with an additional 4' swimming platform. Theres a canopy/cover on the boat as well, so if it's raining, it will be nice and dry.

If the box gets damaged, he's not too concerned. That's why he just got it at a big-box type store. It was his first kick at the bucket in marine audio.


What's the baffle ideal? You mean a cover over top of the front face of the box, say 2" out from the face of the subs, covered on 3 sides? Open at the bottom? I'm picturing something like an upside down map-pocked?

 

That is pretty much the only location for the box on his boat... so with that location as our constraint, we'd be willing to make a new box to get better SPL out of it.

I've got a fair amount of 1" MDF left over from a previous stereo project, so if making a new box is the only solution, so be it.... but what design would be best? Vented, ported, bandpass?

If we make the baffling plate, would it be best to have the subs pointing down and the baffling plate pointing in (towards the center of the boat)?

So far here's what I think we'll try:

#1 - turn the box 180 and have the subs facing the wall, if that fails;
#2 - make a baffling plate on the existing box, if that fails;
#3 - make a new box - but what style would be best?
#4 -

 

It's just an assumption but I'd guess the MTX subs aren't particularly efficient and have a somewhat high FS (resonant frequency). A more efficient sub with a lower FS would have been ideal I think.

 

Agreed that the subs are not the best. Would there be a better box design we could explore for the open-area scenario that we have?

 

You could try porting the box or building a new one. It's likely that a horn or a TL would be much too large for the boat though so you should probably stick to ported.

 

Might also want to check the recommended box volume vs. what you actually have. If your box is too small it'll most likely mute your output a bit.