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Dual Voice Coil sub wiring/questions

L

Little Bear

Full Member
Joined
Oct 11, 2003
Messages
39
Location
NorthEast PA
I want to replace my existing 8" sub that I mounted in a custom wedge style box. Just the sub, not the box. I like the box.

http://www.picturetrail.com/littlebear3

I found one that should fit perfectly because of the very shallow mounting depth of my sub box. It's exactly the same depth as my existing sub.

http://www.sounddomain.com/sku/ABNAW831T

I've never dealt with dual voice coil speakers before. Is there any advantage to dual voice coils other than more wiring options? Do they sound better?

I believe I can wire it up 2 ways. The sub is a DVC 4ohm. I have a 400W 2 channel amp. It will do 100W RMS/channel @ 4 ohms or 300W RMS bridged @ 4ohms. I guess I can either run each voice coil to each channel on the amp or wire the voice coils in series (8 ohms) and bridge the amp (giving me 150W RMS, right?). Which would be better? I'm guessing I'd get more power running each voice coil separately to the amp.

Any thoughts?

-LB
 
You are indeed correct! With your two channel amp, you'll be better off running one coil per channel.
 
I will agree with DS on this one.... i know i know......hurts to admit it! Im only doing so because its what you allready have. In actuallity its the wrong ohm sub for your application. You really should have looked to see if you could have gotten it in a dual 2 or 8 ohm then you could have ran it at 4. And im only saying to run it at 4 because i have no idea what brand amp you are running and if it could handle any lower.
 
arrivalanche said:
I will agree with DS on this one.... i know i know......hurts to admit it! Im only doing so because its what you allready have. In actuallity its the wrong ohm sub for your application. You really should have looked to see if you could have gotten it in a dual 2 or 8 ohm then you could have ran it at 4. And im only saying to run it at 4 because i have no idea what brand amp you are running and if it could handle any lower.
Click to expand...

My amp is a Profile Baja BA400 and can handle a 2ohm/channel load in stereo mode or 4ohm bridged. It's 100W RMS/200W Max per channel @ 4ohm or 300W rms bridged @ 4ohm.

I haven't bought the sub yet. I did look around for other options but my biggest problem is mounting depth. I need one in the 3 1/2" range. Not many options in that depth. After thinking about it, this one should be perfect for my application. The dual voice coil sub is 200W RMS/400W Max (assume 100W RMS/200W Max per each voice coil), the same as my amp. Running each voice coil separately to each channel of the amp will give me a 4 ohm load per channel.

-LB
 
I went to Audiobahn's web site and started poking around the FAQ section. I found out that it's bad to hook up each voice coil to each channel of a stereo amp. It will work if each channel is mono but mine's stereo. They say each voice coil will play different music and eventually tear itself apart from the 2 voice coils fighting each other. :eek: That makes a lot of sense now that I think about it. So on to plan B, wire the voice coils in series (8 ohms) and bridge the amp. Besides, that makes my wiring easier since I don't have to cut and mount another pair of terminals in my sub box. ;D

Just thought I'd pass this info on in case someone else gets in the same situation.

-LB
 
LOL! Please ignore their site. I'd gladly go to my garage and hook up my most costly sub to my largest amp and let it rock all day running stereo to the coils.

Think about it this way: The sub has a pair of coils and you have a pair of amp channels. The positive half of the output waveform will (if the sub is wired correctly) push the cone outwards, causing forwards excursion. The negative half of the waveform will pull the cone backwards, causing backward excurion. If you ran signal to the amp that was opposite and inverse for the channel pair, and then ran this output to the sub, where do you think the cone will rest, considering that the coils are receiving equal yet opposite input?

This is just like the old myth about dual coil subs and polarity. Installers for years have said that if you wire the coils backwards by accident, the cone will rip itself to shreds in a matter of milliseconds. The truth is, that if you wire the coils in opposite polarity, the sub will just sit in the neutral position, since one coils energy is negating the others. The coils WILL NOT rip the sub to shreds.



 
Do not hook both both voice coils up to independent channels on a stereo amp. Like it says on the web site, alot of times, a different signal is coming from the left and right channels. Though it does work, it will deffinately shorten the life of your sub. Run it at 8 ohms bridged, it will be getting the same power as if you run it 4 ohm stereo anyway.
 
Here's an analogy. If you take a piece of rope and pull at both ends, tug-of-war style, with 250lbs of force, where does the rope go? I will stay perfectly still, since the force applied is equal and opposite. If you begin to increase or decrease either sides force, then the results will be different.

There is nothing in a sub to get "destroyed" by wiring coils incorrectly be accident or stereo to a pair of coils. The electrical input from the amp to the coils is simply creating a magnetic force in the motor assembly with this input. The force will vary depending upon how much input is received. The motor assembly is totally isolated from the cone assembly in a conventional sub. The cone is connected to the coils, which rest in a gap within the motor (magnet area) of the sub.

13w7_voicecoil.jpg


Notice the voice coil in this pic, it is red. It "floats" in a very narrow gap. You can see that the only physical contact that the cone has with the speaker is the upper "roll" along the cone's edge, the spider, right next to the voice coil (keeps the coil centered in the gap) and the tinsel leads, which are the little wires attached from the speaker input terminals to the coils themselves to provide input power from the amp.
 
DS, that was a most-excellent explantion!! I was going to ask, but now I don't have to! Excellent diagram!

(y)s for you!!
 
Thanks Yak, and welcome back! ;D

That's a W7 in the diagram for those who are curious.
 
You are wrong. If you wire the voice coils out of phase, or in stereo they are fighting each other. Lets use your tug of war example. If both sides are pulling equal amounts, the rope, in your example, isn't moving. So now your applying power with out movement. That energy turns to heat. Heat will burn up the voice coil, and kill the speaker.
 
Coil heat transfer is a totally different subject than physical destruction of subs due to wiring them incorrectly. You are correct though that wiring them in opposite phase will generate heat. For that matter, ANY input to the sub will generate heat, as subs are horribly inefficient when converting electrical input into mechanical output.

But back to the point. If they are wired in opposite phase, with equal input to each of the two coils, the sub is practically just sitting there, as if at rest, as the magnetic fields are cancelling one another. Let's assume that each channel is providing the sub with 100W continuous input per coil. How will 100W per coil, coils 180 degrees out of phase differ from 100W per coil, coils in phase? 100W per coil is 100W per coil, regardless of the phase difference present. The only factor that may play a part in some subs being smoked by an installer stupid enough to leave them this way would be the fact that the sub at rest would not have the benefit of any mechanical cooling provided by the cone's motion, as in via the voice coil gap and perimeter cooling, if the sub in question has these technologies to its advantage.

As far as wiring a sub stereo and shortening its lifespan, I call BS. Input is input, and cooling is either working or not. If the cone is moving, the sub is cooling. As far as phase being a major concern to ouput level, it only becomes an issue if you're an SPL competitor with the money, know-how and testing equipment to actually win and you have multiple subs, usually mounted in different areas and on different planes, creating phasal anomalies that will decrease SPL due to destructive interference of wavefronts. Case in point: the Gates Bronco. It used PPI PSC's as its winning strategy, before it became obselete using Kicker's product.
 
Oh man DS (or is is BS?) ;) , I gotta side with Allied on this one. You are correct that input is input, and the point here is that a two channel stereo amplifier (assuming it has stereo input) would be sending different levels of output to each voice coil if it's hooked up in stereo. Since the levels vary to get stereo separation (that's the whole point), and the amplifier magnifies the input signal from the head unit and sends different levels to each voice coil this will cause them to work against each other and generate heat and could indeed physically destroy the speaker (electrical burning smell from the voice coil, I've witnessed it). Everyone's heard thousands of songs with high stereo separation with sound moving from left to right and right to left, but it's usually in the upper frequency ranges (OZZY - beginning of Crazy Train is one of my favorite examples). The stereo separation is created by differing levels of output from the head unit between Left & Right channels. 5.1 Dolby and DTS go beyond stereo in more complex separation but I don't mess with that except with my home theater system. Will the speaker blow up, no; will it work for a while and prob sound okay, yes; but it will fail more quickly especially if pushed hard. Another option would be to use a single channel (L or R) from the head unit to the amp and use a RCA single female to two male Y-connector to split the single channel into the Left and Right input on the amp. Then run the amp in stereo to each voice coil and you should be fine because the input is coming from the same channel (might have to increase gain on the amp because input was split). The big downside to this approach is that if there is stereo output in frequencies that the sub is tuned for (this is rare) then you will be missing one channel of the bass. If you really want the lower ohm load I would do this option and see how it works, it will set you back a couple of bucks to get the RCA splitter from Radio Shack. Just my humble opinion...
 
Heat buildup without coil movement = no cooling = the 'potential' for reduced life.

DS is the man and he's right when he says he'd hook up a sub like this and not have an issue. You'd have to run a lab test to see if there was sufficient heat to reduce coil life, and then its a question of how much power you want to put into the coils. 50-100W wouldn't do squat to it no matter what. You wouldn't get more heat than the interior ambient temp on a summer day with the windows up.

It's Friday so time to open a beer and relax and stop worrying about how to wire your subs.
 
No doubt DS has likely forgotten more about car audio and electronics than most will ever know. BUT - this place is great because it's a discussion forum, not an everything DS says is right forum. For what it's worth, here's a quote from the JL Audio 12W6V2 (dual voice coil sub) manual. Pay particular attention to the warning in the last line. While JL may not be the best out there, they're pretty good at what they do and have numerous patents to backup the expertise and knowledge gained through spending money on research and development. If hooking up a dual voice sub up in stereo were fine why would JL go to the extra expense to build in jumpers to wire the voice coils in series or parallel but only have ONE set of speaker inputs. Oh yes, it's probably just a marketing thing. :p As for relaxing and having a beer, that's exactly what I plan to do tonight while upgrading my factory ground and alternator wires and finding a place to mount my new power inverter! (y)

Please note that the W6v2 is a dual voice coil driver.
BOTH voice coils must be connected to the
amplifier (in series or parallel) for the speaker to
operate properly. To accomplish this, each W6v2
features a pair of main input connection pushterminals
and four voice coil configuration tab
terminals. These are located behind the main input
connectors and are used to interconnect the dual
voice coils in one of two ways: Diagram A shows a
series connection (8Ω nominal impedance per
speaker). Diagram B shows a parallel connection
(2Ω nominal impedance per speaker) and is the way
the speaker is configured at the factory. After
verifying that the tabs are properly configured using
the supplied jumper(s), connect the amplifier?s
output wires to the W6v2?s main input pushterminals
and install the speaker into the enclosure.
Warning! Failure to properly connect the
configuration tabs will result in no output and may
damage the speaker.
This is on page three of the owner's manual, available online at http://www.jlaudio.com/subwoofers/pdfs/W6v2_MAN.pdf.

P.S.
Thanks to whoever (Sgt) gave me my first OOPS! >:D The pressure is off now. Why do so many people have theirs disabled anyway? It's just a forum!
 
Thanks for the help everyone. I've decided to go a different route only based on availibility of the subs.

I bought two 8" audiobahn aw831q subs on ebay for $40 + S/H. They are SOOO much beefier than the POS sub that I have now. I tried mounting it in my existing wedge style box and it won't fit. I then tried notching out a groove in the bottom of the box to give the speaker magnet clearance and the next thing I know I'm seeing carpet. :E: Cut too deep and the sub still won't fit. A quick patch job and I throw the old sub back in.

Time to build a new under seat box (maybe 2). >:D My question, down firing or up firing, which is better. I thought down firing was better but almost every box I see is up firing. I'm confused.

I plan on wiring each DVC sub @ 2 ohm and running each off of each stereo channel of my amp. My amp will do 150W RMS @ 2 ohm from each channel.

I can't live without a sub. I found that out the other day. I was riding along and my amp shut off. The music without sub? ICK, BLAH, SPIT... :D: After I got home I got out the volt meter. No power to the amp. I traced by wiring to find my ground wire flopping around. The head of the screw holding it broke off. That was the self tapping screw that came with my wiring kit. Got a beefier screw and reattached. Oh sweet bass... Even a crappy sub is better than no sub. >:D

LB
 
Beats me on a hard and fast rule for up vs. down firing. What do you think DS? I think as long as the sub has enough room for excursion and air movement but maintains something to work against (i.e. floor, bottom of seat, hatchback :D:, etc.) then it should be okay either way. Subs seem to do better when in a corner, against a wall; just as long as they're not firing out into the wide open spaces of the vehicle. At least this is from my own experiences. I'm sure there's some techno-physics explanation but I'll have to leave that to the experts. The only reason mine is downfiring is because it is not under the rear seat so I can take it out easily for midgate use...
 
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