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-   -   Poor bass response from under helm? (http://www.wakeworld.com/forum/showthread.php?t=802384)

Wakesounds 06-14-2014 8:24 PM

Poor bass response from under helm?
2 Attachment(s)
So last year I had two 12" subs in my I/O under the helm (one side firing and one fired towards the bow) and it pounded! Fast forward to this year...I bought a new inboard and built a new enclosure for the same subs and using the same amp. which gives about 1000w @ 12.5v This time both subs face outward towards the driver and it sounds really weak. When you sit in the back row the bass is barely audible when turned all the way up and completely overpowered by the rest of the mids/highs. The subs are moving like crazy but it doesn't seem to have the output audibly.

The only difference that I can think of is that the box is slightly smaller and both subs face outward instead of firing off a wall. Also the new box is built with 3/4 birch and resin coated, the old was 3/4 mdf resin coated. Both are well braced internally. The first pic is the old enclosure the second is the new. Am I missing something? Have other people had success with outward firing sub setups?

T_A 06-14-2014 8:37 PM

Really nice looking enclosure and it sucks you might need to change it, just one of those subs turned sideways toward the hull should pound! Not sure if them facing different directions like you had them before would be better or not. Can you try the old box in there?

T_A 06-14-2014 8:40 PM

I have a single 10 turned torward hull running off 300 rms and it's louder than I'd ever need. Direction makes a huge difference!

BradM07SS 06-15-2014 4:22 AM

Make sure the subs aren't out of phase. The subs would move like Hell but actually cancel each other out.

DavidAnalog 06-15-2014 6:32 AM

In theory, when you load a woofer's output off a single boundary (like a wall, floor, etc.) you pick-up +3 dB of gain. And that is equivalent to doubling your amplifier power. When you previously loaded both subs into a five-sided cavity you benefited from 5 times +3 dB and two woofers compound loading. Now in reality you wouldn't pick-up 15 dB of gain since these are not extended boundaries but the difference is still very real and very audible. You presently are loading off at least one plane, the sole.
Certainly you lose a bit of upper bass attack and some transients when you load the subs into the cavity but I like the minor trade-off for all the acoustic leverage in return.
So while I would expect to hear a difference, I would also look for another cause.

Wakesounds 06-15-2014 9:06 PM

I checked the wiring today and everything was wired up correctly for the amp. I will do a little more looking into the issue tomorrow.

Wakesounds 06-18-2014 7:34 PM

So I did a little more work and testing today. To verify the power I measured the ac voltage output with a 0db 50hz test tone and everything came out correct. I tried firing them at different angles and the best bass output was when firing toward the floor and it was only decent output at best. Part of the problem with that is...I dont have the space to build a box that sits off the floor and fires downward.

The best was I can describe what im hearing is if you crank up you tunes and fire you subs up into the air. It sounds decent if your right in front but as you move a few feet back the bass fades away. I know lots of others have built simalar looking sealed boxes and they claim "pounding bass"...so what am I doing different thats wrong???

T_A 06-18-2014 7:39 PM

Not sure but you already ruled out the stupid stuff like bass level on head unit and EQ right?

Wakesounds 06-18-2014 8:41 PM

Yup of course. I have it running through the ws420 so it bypases the HU. All eq's are off or flat and the mids and towers have more than ample output.

ian_ashton 06-19-2014 4:17 AM

It absolutely sounds like one of the subs is wired backwards to me.

How do you have them wired, Series-Parallel? Is the wiring to both identical?

philwsailz 06-19-2014 6:44 AM

I too agree it sounds like you have the woofers out of phase.


DavidAnalog 06-19-2014 7:07 AM

These are concerns assuming that everything is functioning correctly on the woofers and amplifier, all voice coils are good, load configuration is right for the amplifier, etc.

It takes four times the excursion and therefore four times the amplifier power to produce bass that is one octave lower at the same amplitude level. So in an open air environment lower bass flash evaporates in a 180 degree sphere. Very low bass can be a fleeting pursuit, unlike in a car. Even though bass is more non-directional it does have a polar pattern with more quick impact out in front. The meat of the bass (that which is perceived as loudest) is from 50 to 80 Hz. Not only the fundamentals in that region, but the first harmonic of the lowest fundamentals can be dominant. The bass output begins to gradually attenuate 'above' the selected crossover point. So in your crossover selection have you done anything to impede the output?

Have you done the math to verify what the system 'Q' (Qtc - woofer in box) is? If the 'Q' is too low you will get really deep bass extension below a point where you can generate a lot of perceived output. But you can get less output in the sweet spot and the bass will sound a little dead. If the 'Q' is too high you will get less deep bass extension and a hump in the response but the sub will take on more of a singular character. The key is to find the right balance where the bass is 'live' but also extended and fairly linear (even in its response and roll-off). In a sense, a subwoofer and enclosure is a tuned resonator and you want that resonant range broad, even and perhaps with a small crown in the bass sweet spot. Shoot for a 'Qtc' of around 0.8.

A combination of poor management of both the above can be a real bass killer.
Looking at those two 12"s side-by-side and resting on the sole, I can't imagine why you don't have great bass.

Down-firing can give an impressive tactile sensation because you are exciting the entire cockpit sole. But I would rather move the air than move the boat. And using a reinforcing boundary is certainly effective. But if the bass radiation path is reduced in surface area at any point then you have effectively choked the output. For that reason I prefer side-firing because you typically have much more space between the woofer and the adjacent boundary. Two opposing woofers, with one woofer aimed at the starboard hull and one woofer aimed at the walkthrough wall with a minimum of 6" of clearance on both sides delivers a symmetrical phase output and takes full advantage of every potential reinforcing plane.

hatepain 06-19-2014 9:13 AM

Do you still have the factory sub connected that's is aft of the helm and firing directly at the underhelm sub's? If so you might be getting some serious cancelation.

Houstonshark 06-19-2014 10:51 AM

I can't remember the configuration (and don't want to read through everything again), but have you tried disconnecting one of the subs?

It really sounds like a phasing issue.

Wakesounds 06-19-2014 11:24 AM

1 Attachment(s)
I hope that its wired wrong for the sake of being an easy fix. I do have the factory sub but I disconnected it. The crossover is good...tried multiple settings. The box is on the smaller side of recommendations but still within range at about .8 cuft per sub. I will admit the qts and q information is above my knowledge level for building but I keep within guidlines for enclosure size. As far as the radiation path, there is a wall behind the driver seat that allows pass for the wrap around seating so the passenger can face the rear.

Ive attached a picture of my schematic and amp info. The subs are currently wired to a 3ohm mono load because I dont have room for a third currently. I did hook up the 3rd in the walkway, rear facing to see if it would make a significant difference and it really didnt much. I calculate that each should be getting at least 375w with the boat off at 12.5 and about 600 while running. Like I mentioned, I did hookup a 3rd to pull a 2 ohm load but it only helped a little.

DavidAnalog 06-19-2014 12:38 PM

I doubt you are putting yourself through all this just because the performance is off a little from before or because the bass isn't up to par with an enclosed vehicle cabin. I trust it's not just a small perception thing and it's a BIG difference.
Your schematic looks fine.
I would disconnect one of the subs as mentioned above. And I would try each individually. It's too easy not to eliminate a problematic woofer or voice coil.

0.8 cu.ft. seems really, really small for a 12-inch sub....regardless of what the manufacturer states. And that's a fairly massive sub so if 0.8 is gross then the net might be closer to 0.7. There's just no way unless those subs possess some really unusual parameters. Let me give a 'what if'. Let's say that the sub in that box has a half power point (- 3 dB) at 55 Hz. That means it begins a soft decline much higher. And I might be giving it some credit at that. Then let's say that you have it actively low-passed at 90 Hz. That means the slope actually begins lower than 90 Hz. And in an inordinately small enclosure there is a fairly pronounced peak in the midbass. Now splice it all together. The sub peaks at one frequency just around the crossover point and is in a second order or greater decline on each side of that peak. Second order means 12 dB per octave. Octave means half or double the frequency. -12 dB means much less than 1/10th power. What if the amplifier nomenclature doesn't actually match the frequency. I've seen amplifiers with a crossover a full octave off.
The above might be a second reason to test each sub individually with the entire enclosure displacement and the other opening temporarily sealed off.
In my experience I don't think those subs are efficient so I don't think you have much room for error.

ryanbush11 06-19-2014 12:42 PM

That setup will be running at a 3ohm load to the amplifier...

Wakesounds 06-19-2014 1:59 PM


Originally Posted by ryanbush11 (Post 1881652)
That setup will be running at a 3ohm load to the amplifier...

Yes I know that. Check out my post above.

David, yes its a big difference from my last boat and all the same equipment. Just a little different enclosure and boat layout. I'll check the voice coils and pull one from the box and see how it sounds with 1 sub in double the volume.

ryanbush11 06-19-2014 2:54 PM


Originally Posted by Wakesounds (Post 1881664)
Yes I know that. Check out my post above.

David, yes its a big difference from my last boat and all the same equipment. Just a little different enclosure and boat layout. I'll check the voice coils and pull one from the box and see how it sounds with 1 sub in double the volume.

I thought you were asking, since you listed two different options above...

Wakesounds 06-19-2014 3:24 PM

Sorry if its confusing, I understand that with 2 subs I'm drawing a 3ohm load thats why I listed out the amp output at 3ohms as well as the others. Even at 3 ohms they still are getting good power.

hatepain 06-19-2014 5:36 PM

I was trying to do some research on these sub's but didn't come up with much. I too felt the enclosure was a bit small which led me to wonder. Is that .8 calculation internal volume space less the sub volume displacement? You probably didn't do this but its not uncommon for people to take the outside measurements not accounting for the material thickness and sub displacement when determining the box size.

Here's to hoping its an easily solvable wiring issue!

Wakesounds 06-19-2014 6:02 PM

They are eclipse 8122dvc's. They came in dual three ohm for a while then switched to dual 4 I believe. I bought them and the amp years back and never installed them till I got a boat and had them laying around. They sounded awesome in my last boat with the same amp but different box configuration. You could really "feel" the bass and it was crazy loud when sitting in the driver seat. Now I cant turn my inboats up past half on the ws420 without completely overpowering the bass with all high end. I havent heard any boat with this type of cockpit facing box so im just taking peoples word that it should be decently loud.

Wakesounds 06-19-2014 6:13 PM

Sorry, forgot to mention that internal volume after displacement.

Wakesounds 06-19-2014 6:22 PM

I found these parameters, maybe david or someone can tell me what I should have built either ported or sealed?

Fs 27 Hz*
Qts 0.30*
Vas 3.2 Cu Ft*
SPL 89.4 db*
VCoil Z 3.1 Re Ohm per coil*
Power 500/1000 Watts*
Qms 5*
Qes 0.32*
XMax 1.30" 1 way*
Sd 511.0 Sq CM*

0.10 Cu Ft Woofer Displacement*

ryanbush11 06-19-2014 8:09 PM

If you want it to be louder, ported is always the answer... some people will argue sealed sounds better, but there is no question to go bandpass for SPL

Wakesounds 06-19-2014 9:57 PM


Originally Posted by ryanbush11 (Post 1881705)
If you want it to be louder, ported is always the answer... some people will argue sealed sounds better, but there is no question to go bandpass for SPL

I was referring to what the speaker parameters i listed would suggest as far as enclosure choices...but your right that in the correct setup ported typically yeilds more spl (if you have the space).

BradM07SS 06-20-2014 3:29 AM

Maybe one of the subs wiring came loose . Happened on my setup the woofer will still move with the other one. Check your ohm on the speaker wire at the amp to verify a 3 ohm load

DavidAnalog 06-20-2014 5:25 AM


Originally Posted by Wakesounds (Post 1881696)
I found these parameters, maybe david or someone can tell me what I should have built either ported or sealed?

Fs 27 Hz*
Qts 0.30*
Vas 3.2 Cu Ft*
SPL 89.4 db*
VCoil Z 3.1 Re Ohm per coil*
Power 500/1000 Watts*
Qms 5*
Qes 0.32*
XMax 1.30" 1 way*
Sd 511.0 Sq CM*

0.10 Cu Ft Woofer Displacement*

That is a very low Qts which generally indicates the woofer likes bass-reflex better than sealed.
You would only have space for a single 12-inch sub because the ported enclosure is going to approach 3 cu.ft. external displacement.
I hope you can trust those parameters.

Wakesounds 06-20-2014 10:09 AM

Yes those are accurate parameters. If space does not allow for a ported enclosure, what would be a good sealed enclosure (net per sub) size to start with?

hatepain 06-20-2014 10:44 AM

Did you determine that its not a wiring issue?

Houstonshark 06-20-2014 11:21 AM

Definitely check the wiring first and then disconnect one of the subs before continuing the discussion about the enclosure.

That being said, what are your internal enclosure dimensions?

Wakesounds 06-20-2014 11:47 AM

I checked the wiring and it looked good, that being said...I'm gonna take it all apart and rewire from scratch to make sure. The current size is about .8 cuft net per sub.

hatepain 06-24-2014 10:36 AM

Any update on this?

Wakesounds 06-24-2014 11:08 AM

Still a work in progress. The wiring is correct but I havent checked each vc individually yet. I built a small .9 cuft box for a single 12 and put it in my suv with 500w from a 500/1 to see how it would sound. Keep in mind that the accoustics are different in an suv but it sounded really good with that volume of air space per sub. I also built a single ported 2.2 cuft tuned to 33hz and sounded good in the truck for a test...but havent had time to try it in the boat. So far I'm still disappointed with the output as it only keeps up when the mids are turned down on the ws420.

hatepain 06-24-2014 5:51 PM


Wakesounds 07-14-2014 2:49 PM

So Im still struggling to fix the issue. I pulled out the box with 2 12's from the boat and put it in my truck with a 500/1 so wether it has a 3, 2, or 1.5 ohm resistance...it will still get 500w from that amp. I hooked it up and the output was less than impressive. Then I unhooked 1 of the subs and the output improved with that single sub wired at 1.5 ohms instead of 3 ohms when two are wired. My belief is that when going from 1 to 2 subs and keeping the same power...output should increase slightly (1.5db I think) so what is my problem? I believe I ruled out the encosure volume as the problem by trying a single 12 with a similar enclosure size with good results and I triple checked the wiring and even swapped polarity to see if output increased by some chance. I verified each vc is working...so...im stumped?

DavidAnalog 07-14-2014 5:31 PM

I assume that you have measured the DCR of all four voice coils independently and found all of them to be within a tight tolerance. I might also measure the DCR while slowly, gently and in a centered manner, pushing in and out on the woofer cone, looking for something intermittent.
Just for grins and on the slim chance that one voice coil on one of the woofers is iffy, I would do your single woofer test with the opposite woofer.
I would also take a small 1.5 volt battery or small 9 volt battery and do a polarity check independently on each of the four voice coils.

Wakesounds 07-16-2014 3:15 PM

David, I'm not familiar with the DCR reference? Maybe its just slipped my mind. Also the battery polarity test has been a while...maybe you could remind me the simple process?

Wakesounds 07-16-2014 5:09 PM

So I pulled them out and tested them individually in a solo box and they all sound great individually (in my truck). So maybe the enclosure is a bit small or they should fire into the walkway or hull? Either way, I'm gonna start from scratch and see where it gets me. I've built lots of enclosures over the years but this has been the first that has underperformed and also the first that hasnt fired into a wall or something. Any recommendations from the pros?

BradM07SS 07-17-2014 2:33 AM

I would wire one of them reverse phase and just see how it sounds. Still sounds like they are out of phase

skuhleman 07-17-2014 10:18 AM

Did you try them individually under the helm in different directions? Thats where I would start. Try that before you go building a bunch of different boxes.

Wakesounds 07-17-2014 5:02 PM

I checked the polarity with a 9v for each coil and everything is accurate to its color designation. Next I guess I'll try the 1 sub in different directions to see its response. It just baffles me that others get good bass response from that location and I dont! Maybe my standards are way high...but I dont think so.

DavidAnalog 07-17-2014 7:26 PM

Try this.
Two isolated back to back 1.25 cu.ft. gross enclosures. Not sharing an enclosure. All 0.75" stock. Two .75" X 2" baffle to back stiffeners in each enclosure and computed into the displacement. The .75" edge aimed at the woofer/opposite stiffener. One woofer firing starboard into the hull. One woofer firing port into the center pass-through structure of the driver's helm. Try your best to equalize the average (the hull being angled) distance between the woofers and adjacent surfaces. Hopefully you will have at least 5-inches of clearance between the peak of each surround and the adjacent surface. It's okay if the left side woofer is just a little farther forward in the enclosure than the right side woofer. Have the woofers just far enough apart and offset that the magnet forces don't fight one another. Use terminal cups. Encase the terminal cups. Make absolutely certain that each enclosure is airtight. Sealed inside and outside. So airtight that the woofers face considerable resistance when pushed inward. The joined enclosures raised 3/4-inch up off the sole with polymer blocks. Initially don't worry about the leg room. Just try it so see how it performs. If that doesn't pound then start changing products.

Wakesounds 07-17-2014 9:41 PM

1 Attachment(s)
Thank you David, i'll build them tomorrow but let me clarify...the space is shaped like a hexagon and the port side is mostly cutout like the picture I attached earlier. With this design the port/starboard firing speakers will not be loaded equally against their walls is that ok?

Also the 1.25ft^3 is internall net volume after all displacements correct?

phillywakeboarder 07-18-2014 6:25 AM

What's behind the kick plate under the dash? Have you thought about removing it to make room for a bigger box plus get back some legroom?

Wakesounds 07-18-2014 6:41 AM

I trimmed part of it to allow more space but I dont want to destroy it entirely in case I sell it or decide to remove the enclosure. That peice wraps around to form various trim pieces so complete removal is out of the question unless I wanted to fab trim pieces too (which I dont).

DavidAnalog 07-18-2014 6:49 AM


Originally Posted by Wakesounds (Post 1885204)
Thank you David, i'll build them tomorrow but let me clarify...the space is shaped like a hexagon and the port side is mostly cutout like the picture I attached earlier. With this design the port/starboard firing speakers will not be loaded equally against their walls is that ok?

Also the 1.25ft^3 is internall net volume after all displacements correct?

Gross before woofer mass, not net.

You are right and now that I see into the cavity behind the enclosure I'm no longer feeling the side-firing scheme. Hard not seeing it in person but I thinking you are reading it correctly.
The molded structure around the cavity appears soft and compliant. Not good at all for an adjacent boundary when side-firing.
From the photo the opening over the cavity appears to lead into another cavity. If so that would be more of a bass trap versus a reinforcing boundary. Can you close that opening off?
If there is a solid bulkhead between the under helm cavity and under bow cavity, that's good. If those two spaces are open and adjoined then that's bad.
In the big picture, dual 12-inch subs with lots of power should hammer. Everything else we are discussing is minor tweaking.

DavidAnalog 07-18-2014 7:14 AM

You've tried the Eclipse in your vehicle so as a test try another set of subs in the boat.
Eclipse never engineered or made subs, they just contracted it out. I remember the old Phoenix Gold carbon fiber subs. They looked like a million bucks. As good as their original amplifiers were there was nothing you could do to make their subs sound competitive. Their internal efficiency was so terrible they ate power like a black hole. Possibly the Eclipse subs require too much power for an open field boat. An enclosed vehicle cabin on the other hand will forgive just about anything.

Also, I can't stress enough the integrity of the enclosure.

Good luck.

Wakesounds 07-18-2014 9:35 AM

David, I had the same sub/amp combo in my last boat and it pounded. Thats why I'm not giving up on the equipment just yet.

That molded area is just a thin fiberglass mold and the area above isnt really possible to seal off well. I could take that panel out and try to reinforce it, but that might have to wait a while fir that kind of project if you think thats the way to go. The space behind that opening also shares space with the bow. I was also considering a vented enclosure tuned at maybe 34hz in the walkway to fire off of the divider if I cant manage a decent sealed enclosure under the helm. Not ideal of course but I'm not seeing many options left. Thoughts?

jjolin01 07-19-2014 4:41 PM

I had the same problem last year in my old boat. I found the WS 420 had low output. I sent it in to wetsounds and they verified that and sent me a new EQ. Check that out.

Wakesounds 07-21-2014 10:55 PM

JJ, I even tried it with bypassing the 420 with no improvement. I tried putting it in the walkway off the divider just to see...not really a good idea tho. The divider just rattled a bit since its not very structural. Worth a shot tho. I think it might be worth buying some new equipment at this point if other people aren't having similar issues.

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