Dual Voice Coil Subwoofers

[cab13367]

Okay, time for another newbie question. I am going to use the 5th channel on my Kicker ZX700.5 to run the subwoofer. This channel puts out 210w rms at 4 ohms and 420w rms at 2 ohms. So to get the most out of the amp, I am thinking of replacing my current Polk/MOMO single voice coil 4 ohm sub with something that can be configured for 2 ohm operation. I see that they sell dual voice coil (DVC) 4 ohm subs and DVC 2 ohm subs. I know that I can wire the voice voils in parallel on a 4 ohm DVC sub so the amp sees a 2 ohm load. But my question is, should I go that route or should I buy a 2 ohm DVC sub and just use one voice coil. Will the sub perform better if both voice coils are being used (i.e., buy the 4 ohm DVC and wire the voice coils in parallel). I really don't know how these subs work, as you can tell.

The best bang for the buck 4 ohm DVC that can handle about 400w rms seems to be the Kicker CVR104 (about $75 shipped) - anyone have experience with this sub?

I was really liking the Boston Acoustics G310-44 ($110) until I read that it has a foam surround. Doesn't seem like that would hold up very well over time.

Your thoughts/suggestions are appreciated.

Thanks,

Al

[mmandley]

I have the 4ohn Duel VC on my Sub you herd yesterday Al. The Duel voice coil subs will have a very different sound if you only run 1 coil. Its designed to have both oils running. Its like 2 speakers in 1. You could run a 2 channel amp to the duel voice coil subs and it would sound good. The ability to wire the coils together to lower the ohms allows the amp to work and twice the capacity. 200W Vs 400 watts.

I dont know all the details of the way it works but this is how i understand it. Maybe Razz, Newty, Brian can explain it better.

My money is get the 4ohm duel voice coil and make the 700.5 push is at 2ohm load.

[brain_rinse]

If you decide to buy a new sub, a DVC 4 ohm sub wired in parallel would be a good way to go. Just to be clear, the dual voice coil just gives wiring flexibility and doesn't make it a better performing sub. So for example, there would be no real difference between a single 2 ohm coil sub and a dual 4 ohm coil sub wired in parallel.

I have never used a Kicker CVR sub, but I do know it is their entry level line. If you are going to upgrade, my advice would be to spend a little more and get something that you know will be noticeably louder in the end. Just getting more power from the amp won't necessarily result in a better sounding setup unless your sub is currently way underpowered.

[sandm]

good advice ^
the only real reason to buy a dvc 4ohm sub would be if you plan on adding more down the road, it can give you a little more flexibility, such as running it to 8ohms, then adding another wired in for a total 4ohm load. you will find that some speaker lines only offer one or the other, so you have to take what they have for sale..
have heard a lot of good things about the kicker cvr. lots of guys are using the solobaric subs as well. you need to ensure that whatever sub you buy has a box that is optimized for it. simply replacing a sub with one that offers more power out of the amp may be defeating the purposes if the box is not designed for the sub.
sometimes you are better off with an optimized sub/box combo and a little less power than a ton more power and a box/sub that don't work well together.

[EarmarkMarine]

cab,

You could potentially damage a dual voice coil woofer by wiring only one of the coils. You would be inordinately working one coil with half the overall thermal capacity.

The Polk MOMO sub is very anemic in a sealed enclosure but will sound absolutely great in a bass-reflex enclosure. I've never experienced another woofer where the performance was so polarized. In a bass-reflex enclosure you would get roughly the same output with 200 watts as you would have in a sealed box with 400 watts. So if you're sealed now, then give this some consideration.

You're correct that a dual 4-ohm in parallel is the way to go in order to draw the full output from your amplifier. Also, I totally agree with all of Brian R's comments. Very good points.

David
Earmark Marine

[cab13367]

Thanks everyone, great info as usual.

David,

The sub is in a footbox that is essentially open on one end so it's basically operating in almost a free air state. I was going to try and seal it up but I think I will try to make a ported enclosure out of it per your comments. If after that it seems like it's not hitting hard enough, then I may try something that presents a 2 ohm sub to the amp.

Thanks,

Al

[sandm]

al,
think you might be in for a lot of work here. to turn it into a ported enclosure, you need to completely seal it, then add the port, tuned to the dimensions that the sub needs. I would say your best bets are to find a good free-air sub that will better suit your needs or do what I'm doing, trashing that footwell box and building a box in it's place..

[viking]

sealed enclosure is the only way to go! (see newty and/or mmandley for ideas). I'm kinda partial to JL audio and there better than entry level subs and amps are not all that expensive.

I'll have pics and posts of my upgrades before the season starts.

Just my .02!

[Razzman]

al,
think you might be in for a lot of work here. to turn it into a ported enclosure, you need to completely seal it, then add the port, tuned to the dimensions that the sub needs. I would say your best bets are to find a good free-air sub that will better suit your needs or do what I'm doing, trashing that footwell box and building a box in it's place..

Or do what Newty did and seal off a section and build a box to go in it. I have used the Kicker Comp 10's (not the VR) in a few installs and with 300-400 watts to them they sound good, but they need a sealed box of around .75-1.0cf to do it. A ported box with good power to it needs to be 100% sealed and strong enough to withstand the power. I don't think you can get that out of that space Al without some serious major surgery, more than what Newty did to his imo.

[Brianinpdx]

Cab Cab -

Best advice is here is to NOT hook up one coil. This is one of the topics we would be covering in that Tek session that we should should do for you guys. Hooking up just one coil is a good way to "slinky" the woofers VC (think back to childhood of that slinky heading down the stairs).

The comment about pushing full power out of your amplifier can sometimes be a mixed bag on 5 channel amplifiers (depending on the model). In simple terms, if all the speakers beg for max power the power supply sees / works under max stress. I'd ask the community that has that model amplifier for some input on what has worked best out there in the real world. Other times the power-supply handles the loads just fine but if you hide the amplifier in the boat installation it gets hot and tries to protect itself. I'm not trying to put you off running the amplifier hard, just have a look at the specs and check to see what people have done in the real world.

Now with that said, my choice would be to buy a DVC, run it full power and if you choke or protect the amplifier you can always turn the gain down somewhat. Most amplifiers these days have independent gain controls. Make sure the model you own does.

As for he box situation, let me use plain language.... BAG that free air stuff. Buck up and build a box. And when you do that, use a 12" woofer instead of a 10". Using a 12" (if possible) will offer you big time advantages in your boat because you'll have more cone area in play. Even given the same power a 12" will be noticeably fuller and forceful sounding. From what I hear, Newty just built a box for one of the guys on here. Get him a six pack and go help him. It's a great learning experience.

And if you need help with advice on what will work or wont work, stop by the Exile factory on the way to see Newty...your right in our back yard. We can have a look at your specific situation install wise. *no crawling through our dumpster for factory seconds though :)

Cheers,

-Brian
Exile Audio

[sandm]

thanks for the post.. dead on..

free air subs suck, just didn't want to be the one to offend someone here. now if you do want a freeair, I'll sell ya the kenwood excelon 10 that I just took out of mine ;)

totally agree with jl as well. was going to go 12w3, but ended up getting a steal on a new 12w6. sucker is a beast..

[Razzman]

*no crawling through our dumpster for factory seconds though :)

Well there just went my day! :p

[cab13367]

Guys,

Thanks for the advice and for schooling me on dual voice coil subs. Much appreciated.

As for going all out and building a sub box, using a 12" sub, etc., etc., I don't want to go thru all that trouble. I don't need competition level sound and don't want to take up additional room in the footbox area. So I am going to try and see first if I can make the stock location work with a 10" sub (the max that will fit in there).

It was sounding pretty good with the old amp I was running, hits plenty hard for me, but it was just a little boomy. So I am going to try a few things to tighten it up and if it works, and I get plenty of volume out of the new amp at 4 ohms, then I'm good to go.

Thanks,

Al

[viking]

thanks for the post.. dead on..

totally agree with jl as well. was going to go 12w3, but ended up getting a steal on a new 12w6. sucker is a beast..

I've got a 12w3 (not installed yet). Should be enough for my boat! That baby is an upgrade from the 12w1 that rocks anyway. I've had them in vehicles before. Let me know how she sounds!!

[sandm]

I had a pair of the 10w1's and they were great subs. rocked..

I can't wait to hear this one installed. wanted a pair, but no room.

[jmvotto]

Al, try the existing sub with the new amp Momo with the 5th channel on the kicker. should sound just fine especially with the bass knob for types of tunes. You foot well is taller than my obv and you may need some polyfill to dampen the boominess.

you could try this as well with dynamat a 10" baffle, cheap to try

http://www.crutchfield.com/p_237XT10/XTC-10-Speaker-Baffles-6-1-4-depth.html?o=p&showAll=Y&search=baffle&ssi=0

[Brianinpdx]

Al - sounds like everyone has you on the right track and I don't see anything wrong with your plan with the ten.

And just so everyone knows, I don't ever want to come across as slamming anyones ideas here on free air or otherwise.

But if anyone would like a "on the boat demo" of free air sub bass give me a call and I'll grab a rubber matt and a big ole wooden spoon. We can turn up the stereo and wack away at that matt !!! Hehe. Oh wait, we got no sunny days here anymore. Dangit!

-Brian

ps: on a sincere note, let us know how it turns out.

[sandm]

brian, your thoughts on the epicenter to "restore" some lackluster bass in a freeair enclosure?
haven't used one in years, but I remember it did a better job of "enhancing" bass without just cranking up a gain pot and distorting the sound worse....

[EarmarkMarine]

An epicenter is an awesome processor for restoring compressed fundamentals to older analog recordings. It works very well in an enclosed vehicle that benefits from a 'cabin effect' which constitutes a second order per octave rising characteristic as the bass declines in frequency. At these lower frequencies the woofer is extremely well damped (controlled so to speak) due to the increasing air mass rigidity in the small and confined cabin of a car, truck or SUV. But here comes the "however."

In the open field environment of a boat without such leverage it requires many times the power and places an inordinate mechanical and electrical stress on the woofer trying to achieve the same output level in the bottom octave. For just a little bit of emphasis in the lowest registers it will suck the life out of the dynamics and tonal construction, especially at higher volumes. Using a free-air would only compound the challenge. I might feel differently if you were running a very serious 15-inch with lots and lots of reserve power.

A more efficient way to increase the overall bass output in an open air boat is to slightly expand the woofer's bandwidth by crossing it over a little higher than in a vehicle for instance. After that, having the right woofer to enclosure to amplifier to in-boat loading combination will make a world of difference.

On another subject, several of the woofers mentioned in this thread are definitely not suitable for 'free-air' applications (like the Excelon or Polk MOMO). What exactly are we describing by "free-air"?

David
Earmark Marine

[Razzman]

David, the "free-air" reference in this case is the drivers footrest in the Moomba, which when cut open is a hollow open cavity into the ski locker to port and towards the stern of the boat for wires and cables to run through. SC uses this location for the optional factory sub and many have installed one there. That's why Al (Cab13367) is asking these questions about free-air.

Also, at what point do you recommend crossing over on the sub freq to increase the overall bass as you mentioned?

[cab13367]

David, the "free-air" reference in this case is the drivers footrest in the Moomba, which when cut open is a hollow open cavity into the ski locker to port and towards the stern of the boat for wires and cables to run through. SC uses this location for the optional factory sub and many have installed one there. That's why Al (Cab13367) is asking these questions about free-air.

Also, at what point do you recommend crossing over on the sub freq to increase the overall bass as you mentioned?

Actually, what I said in a nutshell is that the footbox where I have the sub installed is so far from being sealed that my sub is more or less in a freeair state. As Razz says, there is a big hole on the end of it next to the ski locker plus there is a hole on top where all the cables run through plus there is a hole that leads to a chaise under the flooor of the boat. I know my Polk MOMO sub is not a free air sub and again, I plan to seal the enclosure or try to make a ported enclosure out of it and see how that sounds.

So I wasn't asking any questions about a free-air sub, I just mentioned that my sub is basically operating in a free air state.

While we're on the subject, what characteristics makes a sub a good "freeair" sub? That is, how is it different than a non-freeair sub?

[EarmarkMarine]

Razzman,

The crossover frequency selection will be unique to each system. Usually you go a little higher with a small woofer, free-air woofer or woofer that is in a less than optimum application. You'll get an increase in overall output by widening the bandwidth which causes you to gain down the sub. And that results in improved tonal construction, particularly at higher volumes.

Here's one way to proceed. Set your high and lowpass crossovers at 120 Hz. With your tower speakers off, turn up your coaming coaxials to just under clipping (no harshness or significant distortion). With your sub down, incrementally increase the sub's gain until it is a linear extension of the fullrange coaxials. If it sounds boomy, remote or detached then back it down some until the sub sounds like its seemlessly spliced with the mids rather than sounding like an independent source. At this point you'll have good tonal construction with balanced output. If you want more bass emphasis then use your bass tone control. At least it presents a subtle octave-to-octave rise versus the ubrupt edge of a steep crossover slope. Listen to it for awhile this way and get used to it. It may not be for everbody but it is a good reference point.

From this point if you want to increase the sub's gain, the elevated output will raise the frequency of the lowpass -3dB intersection relative to the highpass. So as you increase the sub's gain you'll also simultaneously lower the lowpass frequency to eliminate the broad overlap of the high and lowpass crossover filters. Hopefully your amplifier has independent high and lowpass controls that you're able to stagger the filters. This will allow you to maintain a more uniform phase and amplitude response through the crossover region.

In an open-field environment , even with larger and more powerful subs, we rarely use a lowpass point below 90 Hz. Its very different from a vehicle.

For tuning purposes, use only good recordings without heavy bass emphasis. You don't necessarily want to use your favorite material. Use a variety for contrast. Stay away from downloads, burnt CDs or anything that may have built-in EQ. Have all tone controls flat with the bass EQ on the amplifier defeated.

I know its a protracted answer but there's no perfect frequency. This is a proven technique that has converted many nasty systems to pretty good sounding systems. Plus its a very subjective perception ranging from purists to bassheads.

I hope this helps. Its only a snapshot in the system tuning process.

David
Earmark Marine

[EarmarkMarine]

Cab,

A free-air sub is self-sufficiently damped so it has different electrical and mechanical parameters. It will also have a higher resonance. A 10-inch free-air would optimumly operate in an infinite baffle of 3 cubic feet or larger. Just like any other sub a free-air requires complete front-to-rear acoustic isolation and a very rigid mounting surface.

In contrast, acoustic suspension subs are very dependent on a precise enclosure (sealed or bass-reflex) for damping and control.

Actually free-air subs can sound pretty good if they're properly executed. Unfortunately you rarely see the correct woofer put to task in the right manner. JL Audio makes the best free-air subs by a considerable margin.

Now that I better understand your sub mounting, here's what I would suggest:

Get a true free-air sub. If a sub manufacturer claims their product is a jack of all trades then you can assume it does all applications poorly. Seal up the floor hump the best you can. You're only concerned with openings that are in close proximity to the sub. The distant openings represent too long of a pathlength to be a problem. You want the sub to realize as much of the bilge cavity as possible.

Reinforce the thin fiberglass hump mounting surface with a carpeted thick KingStarboard overlay.

Properly tuned it will be a day and night difference from what you have now.

Another option is to close off the floor hump opening and install a sealed box over the top of the hump that extends toward the bow mold. There's plenty of room up there to fit a side-firing sealed box with .675 gross (before driver) internal displacement. Its a bit tighter up there in the last several year models of Moomba LSVs but it still easily works with 5/8" material thickness. This would be an ideal displacement for a variety of subs whether JL, Alpine, Polk, Kicker, etc.

And Sandm is right, a bass-reflex enclosure doesn't fit well with your scenario.

David
Earmark Marine

[Razzman]

David thanks for the explain. I run the Kicker ZX amps and they have plenty of adjustments easy to get to. I usually end up with my subs right around 80 hz and that seems the best.

Also, i have my sub on top of the footwell hump and it works real well up there, nice surround effect without being boomy.

[cab13367]

Razzman,

The crossover frequency selection will be unique to each system. Usually you go a little higher with a small woofer, free-air woofer or woofer that is in a less than optimum application. You'll get an increase in overall output by widening the bandwidth which causes you to gain down the sub. And that results in improved tonal construction, particularly at higher volumes.

Here's one way to proceed. Set your high and lowpass crossovers at 120 Hz. With your tower speakers off, turn up your coaming coaxials to just under clipping (no harshness or significant distortion). With your sub down, incrementally increase the sub's gain until it is a linear extension of the fullrange coaxials. If it sounds boomy, remote or detached then back it down some until the sub sounds like its seemlessly spliced with the mids rather than sounding like an independent source. At this point you'll have good tonal construction with balanced output. If you want more bass emphasis then use your bass tone control. At least it presents a subtle octave-to-octave rise versus the ubrupt edge of a steep crossover slope. Listen to it for awhile this way and get used to it. It may not be for everbody but it is a good reference point.

From this point if you want to increase the sub's gain, the elevated output will raise the frequency of the lowpass -3dB intersection relative to the highpass. So as you increase the sub's gain you'll also simultaneously lower the lowpass frequency to eliminate the broad overlap of the high and lowpass crossover filters. Hopefully your amplifier has independent high and lowpass controls that you're able to stagger the filters. This will allow you to maintain a more uniform phase and amplitude response through the crossover region.

In an open-field environment , even with larger and more powerful subs, we rarely use a lowpass point below 90 Hz. Its very different from a vehicle.

For tuning purposes, use only good recordings without heavy bass emphasis. You don't necessarily want to use your favorite material. Use a variety for contrast. Stay away from downloads, burnt CDs or anything that may have built-in EQ. Have all tone controls flat with the bass EQ on the amplifier defeated.

I know its a protracted answer but there's no perfect frequency. This is a proven technique that has converted many nasty systems to pretty good sounding systems. Plus its a very subjective perception ranging from purists to bassheads.

I hope this helps. Its only a snapshot in the system tuning process.

David
Earmark Marine

Hi David,

Thanks for the info above. This will come in handy since I am about done with my amp upgrade.

One question: I have the ability to set the crossover frequencies either from my Kenwood head unit or from my amps. Is there an advantage to using one or the other? The head unit is a Kenwood eXcelon KDC-X692 and the amps are a JL Audio M6600 and a Kicker 08ZX700.5.

Thanks,

Al