Subwoofer install in OEM location on 400DA - What gives?

Stee6043

Well-Known Member
Jun 1, 2015
6,706
West Michigan
Boat Info
1997 Sundancer 400
Engines
7.4L Gassers
I was pretty excited to not have to drill a 10" hole in my 400 to match the stereo setup I had on my 340 previously. This weekend I completed the install of my amps and I am baffled by the sub's performance.

With a free-air JL 10" in the stock location (starboard side @ helm) connected to a dedicated amp I am not getting much output in the cockpit. I have the gain all the way up on the amp and I can see the sub moving substantially but the output just isn't there.

In my 340 I cut a hole in the storage position under the helm seat. The same exact sub, same exact amp, was VERY loud. Lots of low end. More than I needed. I had the gain maybe at 3.

I'm assuming the confined wall space at the helm position is not working for a free-air sub? Anyone else have this experience? I'm wondering if I need to relocate to my previously winning location and cut some fiberglass. Kind of a bummer though....I hate cutting glass.

Thanks in advance for any thoughts!
 
Make sure +/- are connected correctly. That will cause the symptoms you describe.
 
Make sure +/- are connected correctly. That will cause the symptoms you describe.

Before closing up the couch I actually swapped them to be sure that wasn't the problem. I was hoping that would be a quick fix. Sadly, not so.
 
I'm assuming the confined wall space at the helm position is not working for a free-air sub?
How confined? A small cavity will impact an IB woofer's performance and sound quality. Other aspects about the mounting location can as well. You did actually go with the M or MX with "IB" in the model number, correct?

I have the gain all the way up on the amp
This really means little, without the context of the amps potential wattage. Say its able to only put out 100W. Well, the amp likely reach full potential well before 100%, so its likely in a state of clipping now, but 100W is not much to a woofer. However, its a 600W potential amp, then all the way up could easily blow a 10" IB woofer.

What amp and how is the woofer wired to it?

Lastly, there are a number of head unit and amp settings that can and will impact the woofers performance, well before we even get to setting the gain. I would highly suggest you enlist the assistance of the JL woofer and/or amp retailer you worked with for the purchase. They should be willing to assist you with the setup and tuning.
 
How confined? A small cavity will impact an IB woofer's performance and sound quality. Other aspects about the mounting location can as well. You did actually go with the M or MX with "IB" in the model number, correct?


This really means little, without the context of the amps potential wattage. Say its able to only put out 100W. Well, the amp likely reach full potential well before 100%, so its likely in a state of clipping now, but 100W is not much to a woofer. However, its a 600W potential amp, then all the way up could easily blow a 10" IB woofer.

What amp and how is the woofer wired to it?

Lastly, there are a number of head unit and amp settings that can and will impact the woofers performance, well before we even get to setting the gain. I would highly suggest you enlist the assistance of the JL woofer and/or amp retailer you worked with for the purchase. They should be willing to assist you with the setup and tuning.

Thanks for the reply, Wylie.

It is indeed a JL MX10IB. I'm running it at 150watts.

I do appreciate your feedback though I'm not looking for a deep dive into the components used only because I've installed this exact same system previously and was exceedingly pleased with the low end performance. Far more than I could have ever needed. I was way, way below full-gain on the amp in the prior installation. I only wonder why the exact components sounds so very different with the sub located in the gunwale vs under the helm seat.

The gunwale is not particularly small. It appears to be open, wide open, for 20' +/-. It's gotta be 2' tall most of the way. Lots of air volume.

I have played with the sub levels on my Fusion head unit. I've also manipulated the tone controls on the head unit. The fact that the speaker is extending so much (visually) is leading me to believe it's the mounting location impacting the sound quality, not the settings. It's getting plenty of power to move the cone....a lot. I was just curious if anyone else has experienced this.

I suppose I could pickup an M10W5 and try it...just for kicks. Looks like that is the sealed box version? Hmmm...
 
The gunwale is not particularly small. It appears to be open, wide open, for 20' +/-. It's gotta be 2' tall most of the way. Lots of air volume.
Then an IB woofer is the correct woofer for this location. However, how its physically installed, can impact the amount of bass energy that radiates from the woofer or is transferred to hull.

I'm not looking for a deep dive into the components used
As stated, there is way more to it, then just the gain setting. Those bass, mid and high tone controls in the head are really impacting the full range speakers, not the woofer. The only thing we want the head to do for the woofer, is provide a full-range output to the amp and control its volume. However, there are head unit setting that do impact the woofer's performance.

My advice is still, to get your amp/woofer retailer to help you. They can give you tips on how to properly mount the woofer. Which head unit output is best, what head unit settings to adjust. What to set the other amp settings to. They can also help you tune the existing in-boats, so they work in unison with the new woofer, not against it.

Swapping woofers will result in the same poor performance. Its not the woofer, but rather upstream. Good luck.
 
Do you have the Sub "Bridged" to the AMP? I'm assuming its a 2 channel amp...

edit: Bridging the sub to an amp requires 2 channels (L&R) you connect the + on one channel to the sub & the - on the other channel to the sub. This doubles the wattage going to the sub as well as works with both L&R channels. Most Amps will also have a 'bridged' switch.

You probably have already done this, but just in case you didn't I thought I'd ask.
 
Last edited:
Do you have the Sub "Bridged" to the AMP? I'm assuming its a 2 channel amp...

edit: Bridging the sub to an amp requires 2 channels (L&R) you connect the + on one channel to the sub & the - on the other channel to the sub. This doubles the wattage going to the sub as well as works with both L&R channels. Most Amps will also have a 'bridged' switch.

You probably have already done this, but just in case you didn't I thought I'd ask.

Sure enough, it's bridged. Like a champ. I have the sub-out from the Fusion head unit connected to a "Y" RCA adapter, L+R inputs into the amp and bridged on the way out. The amp has a built in low pass crossover which is active. Passover frequency has been toyed with but I left it at something just under 100hz. Sub level on the head unit is at 24 or 27 which is the max on the Fusion unit. I reversed polarity just for kicks, no noticeable change in performance.

I'm going to assume the confines of the gunwale are the problem unless I can find some other smoking gun. The solution is cheap...fortunately.

For kicks, here is what the amp install looks like before I completed cleaning up the cables. Nothing fancy, nothing terribly tricky. I simply replaced the OEM setup with something I've used before with very good results.

 
I have the sub-out from the Fusion head unit connected to a "Y" RCA adapter, L+R inputs into the amp
What model head? Does it not have a left and right output pair or is it a single summed mono output?

Just for kicks, connect a stereo RCA to amp and one of the head units full-range outputs.

I'm going to assume the confines of the gunwale are the problem unless It appears to be open, wide open, for 20' +/-. It's gotta be 2' tall most of the way.


I would not assume it or even think it. A typical IB woofer needs about 2.5 3ft of air space. I dont need to do the math, your cavity is WELL above that. The woofer type is not the issue. Defective or blown? Possible, wrong type for the location? Nope. Head unit or amp issue? Sure. Too much gunwale flex? possible.
 
Only 150 watts from that amp bridged? Looks bigger. All the Fusion stuff I have ever messed with had Right/Left outputs for sub. No need for Y cables.
 
Stee6043: I'll admit to not knowing much about about this stuff, but I can tell you I have 2 huge JL subs mounted in my cockpit and 1 of them is in the starboard gunwale and it is louder than I will ever need even at half volume. If you ever want to see/hear it I'm down in slip 113.

-Tom
 
Only 150 watts from that amp bridged? Looks bigger. All the Fusion stuff I have ever messed with had Right/Left outputs for sub. No need for Y cables.
Looks like the Prime series R150x2. So 150W rms x 1 @ 4 ohm bridged

Thats my feeling about the fusion woofer outputs. They typically supply a stereo output, not summed mono.

So if the OP is running a single left or right chnl then splitting it into the amp's left and right, that reduces the signal level, thus effecting the amps output.
 
I second that. 150 watts is right in that subs wheel house. I have seen a bunch of IB subs mounted in that location on friends boats with no effect on performance. Has to be settings or equipment failure.
Nothing else makes sense.
 
Hmmm...you guys have me wondering this morning. I found an online version of the manual that references a mono sub output. I'm running a Fusion MS-RA70N.

I'd have a pretty good laugh at myself if I missed the other sub out but I'm 89.7% sure it was a single RCA on zone 1 with another on zone 2 (not in use).

Good to know you guys have seen subs in this location work well. I may pull my couch back apart this weekend and start working back and forth between the functioning amp/functioning outputs and see what I see. You guys have been most helpful.

And here I thought this would be the easy project!
 
references a mono sub output.

By nature, any single RCA output chnl of a head unit is mono. Each "left" is a mono and each "right" is a mono. But with a full range output, we dont label them "mono", but rather left and right with the intention of having a stereo image when we use both. Woofers dont run stereo, so we simply call them mono, as there is no need for a dedicated left and right.

In your case, you are using a 2 chnl stereo amp. It requires both RCA inputs to be occupied in order for the amp to make its rated output at a reasonable gain level with a typical line level input voltage. You are dividing that single output, resulting in a higher gain level. Still may not even be making its rated power. So, go back and run a traditional 2 chnl stereo RCA from BOTH sub outputs, into BOTH amp inputs.

Next, keep in mind that the woofer zone on the ra70 is tied to zone-1. So if zone-1 volume is down, woofer level will be down. You can turn the woofer level down, but you can only turn it up to the level of zone-1. Unless you are fading front/read on your 4 chnl, id use the ra70's zone-2 output for the woofer. If memory serves me right, you will need a speaker to RCA converter.

If you do choose to stick with the ra70's woofer outputs, you need to go into the head unit and make sure the woofer outputs are set to full-pass or off. We want a full range output to the amp, then let the amp do the filtering work for us. Im betting the woofer outputs are filtered, further hampering its performance.
 
I will take photos this weekend and full fess-up if I missed an RCA output!

Wylie, thanks again for all the help. You've given me quite a comprehensive list of things to check this weekend.
 
Stee6043, I have the same head unit and there is a dedicated rca sub line out with its own level controls. The other thing I would check in the settings menu on the head unit is the crossover setting. If you are using the line 1 rca outs, the crossover setting will limit your low end. Ditch the Y cable and connect directly to the sub line out and check that crossover setting on your head unit. I have a Rockford 10" pm210s4 on a small amp and it is mega loud. That factory location will boom.
 
A couple of things from my experience on my old 2000 400DA. I replaced all of the speakers with JL's. The sub mounting area was thin fiberglass which flexed a lot. Also that big hollow area behind the speaker with the flexing of the fiberglass mounting surface created a lot of resonance and unwanted noise. First I lined the outer hull surface with a sound attenuating mat and then glued a 3/4" thick plywood backing ring behind the fiberglass and screwed the speaker into that ring through the fiberglass. It fixed all that unwanted noise.
 
So I'm just now back from a week on the boat. Had a blast. I got a lot of projects done during the week but I would say the audio project is still 15% "open".

I did confirm that I had the sub crossover setting on the Fusion head unit set at 50hz. Changing this to the highest setting (250 I believe) made a noticeable difference. I was able to bring the sub level down substantially as a result, mid-teens now.

I think I'm probably functioning normally at this point with maybe only the flex/space issue changing the way this sub performs when I compare it to my other. I'd say it's plenty loud now but I still don't love how high I have the gain on the amp.

I did not have a chance to remove my couch but just to clarify - I am connected to the Zone 1 sub out on the head unit. There was some question over whether or not it is a stereo out vs mono out. I haven't confirmed this yet. But I'm 76% sure it was a mono-out, hence the Y RCA adapter being used. I still plan to confirm this....eventually.

In terms of the overall system setup I will someday want to add something aft facing and maybe even something in the anchor locker. I hope to keep this boat a while so why not make it just the way I want it....:)
 

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