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WakeWorld Discussion Board » >> Boats, Accessories & Tow Vehicles Archive » Archive through April 21, 2006 » Ohm load question for dual coil sub « Previous Next »
By Richard (nauty) on Wednesday, March 29, 2006 - 9:11 am:    Edit Post Delete Post
I have a 4 ohm dual voice coil sub and a 4 channel amp. If I bridge the 4 channels of the amp into 2 channels, each channel then becomes 2 ohm. By running each of the 2 ohm bridged channels to the dual voice coil sub will I get a total of 4 ohms to the sub?

I just want to make sure I'me on the right track here.

 
By adam Curtis (acurtis_ttu) on Wednesday, March 29, 2006 - 9:56 am:    Edit Post Delete Post
the "channels" don't become two ohms the voice coils are what cause the resistance (ohm). By doing what your talkign about, your amp will see ch 1 & 2 @ a 4ohm load (one voice coil) and ch 3 & 4 @ a 4ohm load (the other voice coil). I've never tried that before, I know it gets a little tricky running dual VC subs off multiple channels. Sorry I wasn't more help.
 
By Elle Duke (elleduke) on Wednesday, March 29, 2006 - 10:17 am:    Edit Post Delete Post
Check this out it might help you out.

http://www.crutchfieldadvisor.com/learningcenter/car/subwoofers_wiring.html


 
By Richard (nauty) on Wednesday, March 29, 2006 - 10:26 am:    Edit Post Delete Post
Thanks for the reply. Yep, I'm a little confused myself. It's an older Kenwood amp (KAC-943). I downloaded a manual off the web for it. The manual has few wiring examples illustrated. One of the examples shows the amp in bridged mode, which states that each bridged channel will be 2 ohms. In this example only two speakers are being run off of the amp at a 2 ohm load. I thought that if each bridged channel (1&2 - 3&4) were running to the same dual coil 4 ohm sub, would it be a total of 4 ohms from the amp to the sub?

I thought I read a thread a couple of days ago where it said this was the case. I've searched all over and I can't seem to find the thread. If it turns out I am mistaken here, I would greatly appreciate it if someone could tell me how best to hook up this sub using a 440W 4 channel amp. The sub is rated at 4 ohms 500w RMS and 1000w max.

Thanks very much for your help!

 
By Craig Strait (yosquire) on Wednesday, March 29, 2006 - 10:26 am:    Edit Post Delete Post
The top picture assumes your Subs consist of two 2 Ohm voice coils.

The lower picture assumes two things, your Subs consist of two 4 Ohm voice coils, and your amp is 2 ohm stable in bridged mode. If it is not, you could burn up your amp by doing this.
Upload

 
By adam Curtis (acurtis_ttu) on Wednesday, March 29, 2006 - 10:46 am:    Edit Post Delete Post
Am I missing something? Richard you have one sub and your trying to hook it up to a 4 cahnnel amp? I'm seeing a link on how to hook up multiple subs to a 2 ch amp and pictures of multiple subs to a 2 ch amp????

Usually the way those manuals read can be a little confusing, the resitance number given is what the amp will push at that particular load.

Based on what I wrote and you wrote your amp will see a 4ohm load on both channels not 2ohm. I woudl think it woudl be ok , but you won't gain any additional power. If you bridged channel 1&2 but only show the amp a 4ohm load I woudl think in theory it woudl be just like playing out of either channel 1 or 2 (@ a 2ohm load, both VC run in parallel) . Remember the bridged power according to your amp is rated @ 2ohms. Also something to remember most 4 ch amps were not primarily built to push subs, therfore are not ideal.

(Message edited by acurtis_ttu on March 29, 2006)

 
By Richard (nauty) on Wednesday, March 29, 2006 - 10:54 am:    Edit Post Delete Post
Craig,

I'm a little confused by your diagram. It could be because I just don't understand stereo diagrams or because I am sick and have been taking Sudafed this morning

To answer your question, each voice coil on my sub is 2 ohms. What confuses me about the top diagram is that you show two coils with two sets of terminals on each. Perhaps I'm just looking at it wrong?

Anyway, I just called tech support for the sub. The tech told me that I could run the amp in bridged mode (2 ohm) with channels 1&2 going to one terminal and channel 3&4 going to the other terminal as long as each bridged channel is in mono mode. (The amp I have is stable at 2 ohm in bridged mode and does have a mono switch for each amp. This amp is basically two 2 channel amps in the same casing. When bridging channels 1&2 and 3&4 there is a switch for each that allows you to select mono for each).

Is this the best way or would you suggest wiring it as stated in your top diagram?

 
By Bruce Mac (brucemac) on Wednesday, March 29, 2006 - 10:55 am:    Edit Post Delete Post
yeah, i think adams is right, you're not going to gain anything running all four channels to the amp, in fact it could be the opposite. from what i'm reading above, your best bet would be to do waht adams is saying and running two-channels bridged to the sub and have the sub wired in parallel (4-ohm dvc sub in parallel would give you a 2-ohm load).
 
By Bruce Mac (brucemac) on Wednesday, March 29, 2006 - 10:57 am:    Edit Post Delete Post
oh then it's a 2-ohm sub, forget what i said
 
By adam Curtis (acurtis_ttu) on Wednesday, March 29, 2006 - 11:03 am:    Edit Post Delete Post
nauty, your right. I also assumed we were talkign abtou a dual 4 ohm. Run one vocie coil to 1/2 channel and the other voice coil to the 3/4 channel. The diagrams above are not what your after. take the positive of one vocie coil to the positive of the 1/2 channel. Take the negative and do the same. Very simple hookup. repeat on the other vocie coil. your amp will see a 2ohm load on ch. 1/2 and 3/4.
 
By Richard (nauty) on Wednesday, March 29, 2006 - 11:08 am:    Edit Post Delete Post
Thanks very much for everyone's help.

For future reference, I wouldn't reccommend trying to figure out wiring diagrams after taking Sudafed. My head is spinning.

 
By Richard (nauty) on Wednesday, March 29, 2006 - 11:17 am:    Edit Post Delete Post
Okay...I'm a moron.

Being doped up on Sudafed I wasn't positive that I remembered correctly what the tech told me each coil was, so I called him back. I was wrong. Each coil is 4 ohms. Now then, what' the best way to hook up this sub using a 4 channel amp?

 
By Bruce Mac (brucemac) on Wednesday, March 29, 2006 - 11:21 am:    Edit Post Delete Post
then I think you should listen to Adam

if you run the sub in parallel off of 2 channels bridged, it would be a 2-ohm load.

i would get a second opinion on that.

 
By Tom (wakeprodigy) on Wednesday, March 29, 2006 - 11:31 am:    Edit Post Delete Post
Just how Adam said. Follow this check list.

Bridge your 4 channel amp into two channels
Connect one voice coil to channel 1/2
Connect the other voice coil to channel 3/4

This will have each bridged channel (1/2 or 3/4) driving a 4 ohm load. Your amp should be able to handle this.

Make sure that your sub can handle the power your amp delivers.

(Message edited by wakeprodigy on March 29, 2006)

 
By Michael Hayes (mhayes) on Wednesday, March 29, 2006 - 11:33 am:    Edit Post Delete Post
Not sure about the details of the Kenwood amp, but be careful because most amps if stable at 2 ohms in stereo, are not stable at 2 ohms when bridged. Take JL amps for instance, a 300/2 in stereo is stable from 1.5 to 4 ohms, however when bridged, it's stable from 3 to 8 ohms.

(Message edited by mhayes on March 29, 2006)

 
By bowen (holderbee) on Wednesday, March 29, 2006 - 11:49 am:    Edit Post Delete Post
Nauty...you are retarded! I didn't realize that you bought a dual 2 ohm VC sub. I thought it was a dual 4 ohm VC. Someone correct me if I am wrong, but in order to maximize the amp...you should probably get a different sub. You should get a dual 2 ohm VC sub or a single 4 ohm sub. Otherwise you will be running your amp at 2 ohms and it will probably end up overheating and clipping out on you (because it is an older amp).

I can help you if you still can't figure it out! You should use channels 1 & 2 to run your tower speakers. Then bridge channels 3 & 4 to run your sub. Uhhh...at least I think that is right!


 
By Richard (nauty) on Wednesday, March 29, 2006 - 12:02 pm:    Edit Post Delete Post
Kevin, yes, I am retarded. No, the sub is dual 4 ohm VC, not 2 ohm like I initially said. I'm going to use my other amp to run the tower speakers and then just run the cabin speakers off of the head unit.

I thought I would use the Kenwood amp to only run the sub. I've done some searching on other forums and it looks like the best way to run it would be to bridge channels 1&2 and wire it paralell. This will only give me 220 watts to the sub.

I may just do it this way for now and then get a more powerful 2 channel amp down the road.

 
By bowen (holderbee) on Wednesday, March 29, 2006 - 12:10 pm:    Edit Post Delete Post
Dick - 220 watts RMS will still give you plenty of power for that sub. It will still sound good. No worries! We need to RIDE!
 
By Craig Strait (yosquire) on Wednesday, March 29, 2006 - 10:29 pm:    Edit Post Delete Post
I'm sorry, I based my diagrams off of Two subwoofers. I miss-read your first post and missed your second post as we posted it at exactly the same time. And now after reading this thread I feel like I've taken Sudafed..

I'm not trying to start a flaming response here. But I'm not on the same page as everyone, including the Kenwood tech -- who probably makes $7/hr. So this post is entirely my opinion.

I don't think the brand of subwoofer was established, nor do I think it matters in the context of my message. According to JL's website* they advise NOT connecting each voice coil up to "different signals."
Upload
"it is advisable to...connect the voice coils of the dual voice coil speaker together in parallel or series."

They go on to say "If a dual voice coil subwoofer must be wired to two independent channels, the inputs to both channels should ideally be the same (summed mono) and every effort should be made to match the gains of both channels as closely as possible."

In my opinion, it seems highly unlikely that the amplifier will produce the exact same signal, from an electrical perspective. Yes the ch1&2 and ch3&4 will sound the same. But electrically, they've been through different Taiwan Lowest-Bidder circuitry, and the variation in the different circuitry will cause an output signal difference. If the two signals are different, then the result will be distortion and possible damage. The only way to be absolutely certain you're running the same signal is to wire the coils together (parallel or series) to the same channel. Imagine if you had an electrical motor than had two different input signals, One input signal is saying "Reverse" while the other is saying "Forward." Then a Micro-second later the second one Reverses. Same concept, you could imagine the stress on the motor.

In the end it'll work either way. It probably won't matter and won't have any noticeable sound difference. Though, I personally would not hook my dual-vc drivers up to separate channels.

* http://mobile.jlaudio.com/support_pages.php?page_id=163 Section: What happens when you run different signals into each voice coil of a dual voice coil speaker?

 
By Richard (nauty) on Thursday, March 30, 2006 - 7:09 am:    Edit Post Delete Post
Craig,

I agree with you. I looked at several wiring diagrams from a few car audio websites and parallel or series were the only two ways that were suggested from all the sites I looked at.

After the Sudafed wore off I decided to wire it parallel.

Thanks again.

 
By Bruce Mac (brucemac) on Thursday, March 30, 2006 - 10:25 am:    Edit Post Delete Post
you're saying confirming exactly what adam and i stated above.
 
By Craig Strait (yosquire) on Thursday, March 30, 2006 - 9:15 pm:    Edit Post Delete Post
"Run one vocie coil to 1/2 channel and the other voice coil to the 3/4 channel...take the positive of one vocie coil to the positive of the 1/2 channel. Take the negative and do the same."

^^^ -- No offense, I'm advising against that.



"if you run the sub in parallel off of 2 channels bridged, it would be a 2-ohm load."

^^^ -- I'm quite sure this is not possible.





 
By Rob (lowdrag) on Thursday, March 30, 2006 - 11:22 pm:    Edit Post Delete Post
Don't know about the older Kenwood amps, but the newer ones are only stable to 4 ohms when bridged. Sounds like you've got a couple of choices. Try what you've got, run one voice coil to each of the bridged channels with a mono signal and try to match the gains. Or consider a class d sub amp that can handle your sub wired parallel at two ohms. Last choice, get a different sub with 2 ohm voice coils, wire them in series for a 4 ohm load to one of the bridged channels and save the other two channels for future use if you add speakers.
 
By Bruce Mac (brucemac) on Friday, March 31, 2006 - 7:13 am:    Edit Post Delete Post
wups! sorry you're right, i guess i didn't read adams post closely, but i do know you're not supposed to do that. only because i just went from a single voice coil 4-ohm to a dual voice coil 4-ohm sub. i had asked the installer how they do it and he explained it to me. sorry :-)
 
By Richard (nauty) on Friday, March 31, 2006 - 8:47 am:    Edit Post Delete Post
Just when I thought I had this thing figured out, now I'm getting confused again.

Here is how I wired the sub and amp:

I bridged channels 1 & 2. I then wired the sub parallel. I am not using channels 3 & 4 at all. According to various wiring diagrams this should give me a 2 ohm load...correct?

As to whether or not the amp is stable at 2 ohms, I guess I am unsure? The amp has a two position switch on it that says 4 ohms on one side and 2 ohms with (bridged) in parenthesis on the other side. I guess I am assuming that the amp should be stable at 2 ohms since it gives the option to do so?

Here is a little more info about the amp, from the owners manual:

Kenwood KAC-943

- 4 channel amplifier
- Max power output (4 ohm)
4 channel mode…….. 110W x 4
3 channel mode…….. 110W x 2 + 220W
2 channel mode…….. 220W x 2

- Rated Power output at 12V (4 ohm)
4 channel mode…….. 50W x 4
3 channel mode…….. 50W x 2 + 130W
2 channel mode…….. 130W x 2

- Rated Power output (2 ohm)
4 channel mode…….. 65W x4

- High pass filter : 30hz - 200hz variable
- Low pass filter : 30hz - 200hz variable

Now then.... As I said, I wired the amp bridging channels 1&2 with the DVC sub wired in parallel. The sub sounded great when I fired it up. Did I do this all wrong?

 
By adam Curtis (acurtis_ttu) on Friday, March 31, 2006 - 8:56 am:    Edit Post Delete Post
Wiring (4 ohm DVC ) in parallel will show your amp a 2 ohm load. Mroe than likely your amp will go into protection mode if you wired it incorrectly, either that or it's going to get hot real quick and then shut down. Soudns like you got it though, if it works and better yet soudns good.

Sorry for the wrong advice of trying to wire each vocie coil to it's own channel, but I did cover myself earlier..

"I've never tried that before, I know it gets a little tricky running dual VC subs off multiple channels."

(Message edited by acurtis_ttu on March 31, 2006)

 
By Richard (nauty) on Friday, March 31, 2006 - 8:56 am:    Edit Post Delete Post
Craig,

You said:

"if you run the sub in parallel off of 2 channels bridged, it would be a 2-ohm load."

^^^ -- I'm quite sure this is not possible.


What do you mean? Here is the diagram I used to wire the sub:

Upload

Are you saying because the amp is bridged it would not be a 2 ohm load?

 
By Richard (nauty) on Friday, March 31, 2006 - 10:06 am:    Edit Post Delete Post
Well crap!! I finally did what I should have done in the first place. I called Kenwood and told them my scenario. They said that there is not way to run this sub using this amp. They said the amp is only stable at 2 ohms when in 4 channel mode. He suggested that I get another sub or a different amp.

Thanks again for everyone's input.

 
By Bruce Mac (brucemac) on Friday, March 31, 2006 - 10:21 am:    Edit Post Delete Post
doesn't that just suck. well fortunately, it won't cost you a lot of money to get a new amp. you could pick up a JL 250/1 or even an e1200. The 250/1 is better, but the e1200 would work good too and would give you 200 Watts at 12.5 and 270'ish at 14.4. both are pretty small too.
 
By Richard (nauty) on Friday, March 31, 2006 - 10:34 am:    Edit Post Delete Post
Actually, in my case I think it will be cheaper to buy a second sub. I really don't need that much bass, but I'm trying to keep this stereo project as low cost as possible. Perhaps down the road I will get a more high powered amp to run the subs.
 
By adam Curtis (acurtis_ttu) on Friday, March 31, 2006 - 11:55 am:    Edit Post Delete Post
I have a 250/1 that came out of my g/f's car sitting in my closet. maybe a year old or so, still have the original packaging. Your in Dallas right?
 
By Richard (nauty) on Friday, March 31, 2006 - 12:26 pm:    Edit Post Delete Post
Adam,

Yes, I'm in Dallas, but unless you would like to trade for the 4 channel Kenwood that my buddy gave me for free, it's probably out of my price range.

Normally I would jump all over it, but I just booked a 3 day lesson with Pat McElhinney. The $500 bones I spent on that is just about all that my wife will let me get by with without coming to blows If I want to stay married I better lay low for a while when it comes to spending more money on the boat.

The sub I have is a PYLE 1090BL. It's definitely not on the high end of subs as it only cost me $38. I just took my last $40 and bought a second Pyle sub. I definitely will upgrade the amp for these subs down the road, but for the time being I'll make do with what I have.

On a side note...... I called Kenwood back to get specifics on how to wire two subs to the 4 channel amp I have. The Kenwood tech advised me to wire each of the 4 channels to a VC terminal and switch the amp to stereo mode. I may be naive to stereo wiring, but after this marathon thread I've come to know that there's no way that can be right?

I have found several diagrams which state the best way to wire two DVC subs at a 4 ohm load is to wire them series/parallel to one channel. I plan on bridging channels 1&2 on the Kenwood amp and the wiring the sub series/parallel. Here's an example:

Upload

This will have to suffice until I can get a more powerfull amp.

 
By Craig Strait (yosquire) on Friday, March 31, 2006 - 11:31 pm:    Edit Post Delete Post
I quoted:
"if you run the sub in parallel off of 2 channels bridged, it would be a 2-ohm load."

^^^ -- I'm quite sure this is not possible.


The sub in parallel looks like this:
Upload
And so it's impossible to run the sub "off of 2 channels..."


You said you don't need that much bass, though the nice thing is that you can run these speakers half as hard to get the bass you like out of them.

}

 
By Craig Strait (yosquire) on Saturday, April 01, 2006 - 12:03 am:    Edit Post Delete Post
btw: (off topic -- Texas question)

I'll be in Austin on business next week, the 10th.

I've never been to Texas. Any suggestions?


 
By Richard (nauty) on Saturday, April 01, 2006 - 7:04 am:    Edit Post Delete Post
I'm not too familiar with the Austin aera as far sas riding, but for a beer or 12, 6th street is always good on the weekends. If you can't find a pull while you're down there, the Texas Ski Ranch cable park is about 30-45 minutes south of Austin.
 
By Craig Strait (yosquire) on Saturday, April 01, 2006 - 10:05 am:    Edit Post Delete Post
Cable Park?

Sweet - I'm there. Good thing I asked.

we Don't have anything like that anywhere near the northwest.

 
By Craig Strait (yosquire) on Saturday, April 01, 2006 - 10:09 am:    Edit Post Delete Post
Was thinking about your sub/amp problem a little more.

When you do buy a bigger amp, see if you can find one that is 1 ohm stable.

The reason I say this is, with 2 Subs that are Dual 4 Ohm Voice Coils, You are constrained to either 1 Ohm total load or 4 Ohms total load - When running off the same channel.

OR

You could run them in stereo at 2 ohms load each.

Just something MORE to think about..

 
By matt (supraman) on Saturday, April 01, 2006 - 10:48 am:    Edit Post Delete Post
WARNING LONG POST TO TRY AND HELP RESOLVE THIS:

Richard,

The last diagram you posted is not applicable, as it is based on TWO speakers, each with dual voice coils. As I understand it, you have ONE speaker with a dual voice coil.

There are a number of things we've got to clear up in order to make sense of this:

1) Ohms are measure of how much resistance there is to an electrical signal. Less resistance in a path means more power can flow through – but often the increased levels of power surging through the lines can also heat up your amp.

Using the extreme example of reduced resistance, a "short circuit" is when a line has zero resistance. The usual result of a short circuit is that the amp basically heats up so much it shuts down. There is simply too much juice flowing through the lines.

2) Now, different speakers offer different amounts of resistance. Amp companies know this, and they give you some guidelines on how their amp will interact with different speakers and speaker configurations you might use. Let's look at the specs for your amp:

Rated Power output (4 ohm)
4 channel mode - 50W x 4

Rated Power output (2 ohm)
4 channel mode - 65W x4

Proving what we talked about in point 1, if the speakers have a lower resistance (2 ohms instead of 4) the amp is able to pump out more power (65w vs 50w).

Also, as we said in point one, if an amp sees too little resistance, it can cause a problem. You should also notice that in the original specs you posted, the amp offers a "two channel mode" or "bridged" rating under a 4-ohm load, but it does not offer a two channel mode rating under a 2-ohm load. Why? Because the amp is not capable of running a two ohm load when the channels are bridged – it would just be too much juice in the line. It will overheat.

3) Wiring a speaker in parallel is NOT the same thing as wiring it in series. I'm about to explain this, using single voice coils (one positive terminal and one negative terminal per speaker) for simplicity. We'll bring the discussion back to dual voice coil subs in a minute.

Wiring in PARALLEL cuts resistance (measured in ohms) in HALF. For example, say you have two speakers, each with a resistance of four ohms. By wiring the speakers in parallel, you are cutting the total resistance to two ohms.

Wiring in SERIES will DOUBLE the total resistance. Again, let's use an example of two speakers, each with a rated resistance of four ohms. If you wire them in series, the resistance will increase to 8 ohms.

4) Now how do you wire in parallel? Basically, this means connecting all the positive terminals in your system to each other, and then connecting all the negative terminals to each other. Run a wire from the positive terminal on your amp, to the positive terminal on the first speaker, and then run a wire from the positive terminal of the first speaker to the positive terminal of the second speaker. Pretty easy. Now do the same thing with negative. Wire the negative terminal from the amp to negative terminal of first speaker. Then wire that to the negative terminal of second speaker. That's it. Wiring in parallel simply means connecting all positive terminals in a line and all negative terminals in a line.

How do you wire in series? In this case, you’ll be mixing and matching positive and negative terminals. Run a line from the positive terminal of your amp, to the positive terminal of your first speaker. Then, run a line from the NEGATIVE terminal for the first speaker, to the POSITIVE terminal of the second speaker. Finally, run a wire from the NEGATIVE terminal of the second speaker to the negative terminal on the amp. That’s wiring in series.

5) Now, how does this all apply to you? A dual voice coil (DVC) speaker is kind of like having two speakers in one. The same rules above about wiring to terminals and all that still apply. So here’s the question: how do you wire your system? Well, to start off, we know that you’ve basically got two speakers (figuratively), each with 4 ohms of resistance. If we wire in parallel, we will cut that in half and the amp will see a 2 ohm load. If we wire in series, it will double the resistance, and your amp will see an 8 ohm load. In this case, increased resistance is safer than reduced resistance – the catch is that you will not have as much power surging through the lines to the sub.

If I were you, I would wire your speaker in Series, and then bridge two channels of your amp (combine one and two for instance) to supply it. This will leave you with an 8 ohm load on two of your channels and leave two channels free for later use. Your sub will receive somewhere in the neighborhood of 100-150 watts continuously.

PS -- I just read that you bought a second sub. If that's the case, and it's what you want, your wiring diagram is correct.


(Message edited by supraman on April 01, 2006)

 
By Craig Strait (yosquire) on Saturday, April 01, 2006 - 12:06 pm:    Edit Post Delete Post
Matt,

How would an 8 Ohm load allow the amp to deliver 100-150 watts continuously?

The amp is a 130w RMS @ 4 ohm.


 
By matt (supraman) on Saturday, April 01, 2006 - 12:54 pm:    Edit Post Delete Post
Craig,

Whoops - I used the theoretical max power spec instead of the rated (continuous) power spec. However, I still think he may end up at around 100 watts continous. Here's why: different amps reflect different swings when changing resistance. For instance, on some JL amps, the rated output doesn't change when cutting from 2 ohms to 1, etc. On Nauti's amp, reducing the amp from 4 ohms to 2 ohms yields a 30% increase in power (50 to 65w). If the same variable holds up going the other direction, running it at 8 ohms may only cost him 30%, taking it from 130 to about 100. So it's possible he'd net out at 100 continuous at 8 ohms.

 
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