OHMs law????

I have a question I hope that someone could help me with. Am I correct in my figures that 3 (2ohm sub coils) wired in series than parralled to 3 (2ohm sub coils) = 2.6 ohms????????

I think it would be 1.33ohmshttp://www.edesignaudio.com/site/wiring/3dvcseriesparallel.jpg

I have a question I hope that someone could help me with. Am I correct in my figures that 3 (2ohm sub coils) wired in series than parralled to 3 (2ohm sub coils) = 2.6 ohms????????
Even though ohms law is a mathematical formula for I= V/R where where I is the current, V is voltage drop, and R is resistance, it's easier to think of it logically. Two or more resistors in parallel are slightly less than the lowest resistance value. Two or more resistors in series are generally the sum of their resistances so the set of three two ohm speakers would equal about 6 ohms. Two "set's" of these 6 ohm totals in parallel would be slightly less than 6 ohms or in the 5 to 6 ohms range. So my estimate is a little less than 6 ohms for all six speakers.

Two "set's" of these 6 ohm totals in parallel would be slightly less than 6 ohms or in the 5 to 6 ohms range. So my estimate is a little less than 6 ohms for all six speakers.

No, 6 ohms in parallel with 6 ohms is 3 ohms. Equal resistances in parallel are always half:
1
---------------
1/R1+1/R2+1/R3...etc

Fred is correct, 1.333 ohms for three 4 ohm speakers wired in parallel.

No, 6 ohms in parallel with 6 ohms is 3 ohms. Equal resistances in parallel are always half:
1
---------------
1/R1+1/R2+1/R3...etc

Fred is correct, 1.333 ohms for three 4 ohm speakers wired in parallel.

Correct!!

This is assuming that you are talking about a total of 2 groups of 3 drivers with an individual resistance of wired in series and then the 2 groups are then wired in parallel. If you are talking about 1 group of 3 2 ohm drivers in series and then adding 3 more drivers individually in parallel, the answer is .85 ohms.

Here is a website that contains many useful audio calculators. I find it to be one of the best overall sites for information on the web for quick calculations.

http://www.the12volt.com/caraudio/boxcalcs.asp#por

Fredridge- Nice illustration, but that is not what I came up with. I wish I could make an illistration like that, so I could better explain. How did you do it??
Ok, I decided to just hook up 3 of my new subs and all are 2 ohm dual voice coils. I tried it several ways. I tried on the first sub going + to - to second sub + to - to the third sub + to terminal cup -, same on the other side on the coils. I then parralled the first +'s to the terminal cup and then parralled the third sub -'s to the terminal cup. I am getting 2.6 - 2.7 at the terminal cup. I also checked all + to - on any one of the subs and get the same resistance. The digital volt ohm meter doesn't lie does it????. Anyone else able to get the same results? Thanks I just want to make sure this is going to work before I go too far.

That is a nice illustration, I wish I had that kind of talent. I got it from the elemental designs website (www.edesignaudio.com), I looked on the www.bcae1.com sight, but was a little too complicated to make a simple post.

based on another thread here, I don't think your DMM can tell you what they are actually wired at.

Here's another helpful link.....

http://www.the12volt.com/caraudio/boxcalcs.asp

Ultimately what I came up with (what goes to the amp) is 2.66 ohms. Now if I hook up just one coil (knowing it is only 2 ohm) I get 2 ohms. So I figure that the amp will see 2.66 ohms, which is slightly above its most efficency rating. At mono 2 ohms the amp runs 1,089 watts, according to the birth certificate that came with the amp. At 2.66 ohms the amp is not below what it is stable at and not too high like 4 ohms. The amp should run all day without a sweat!!!!

Here's another helpful link.....

http://www.the12volt.com/caraudio/boxcalcs.asp

great sight, I will be saving and using that one.

Remember that wiring up only one coil of a DVC sub means it can only handle half the power. Be careful.

I would never just hook up 1 coil and leave it that way!! I am only using that as an example. If you ohm out 1 coil of a dual voice coil it will read 2 ohms. Each coil is 2 ohms. Dual voice coil 2 ohm per coil.
I have all voice coils connected. I guess I will have to find out a way to post my schematic of how I wired it. I know for a fact all coils are seeing 2.66 ohms with a total impedance of 2.66 to the amp.

How do you know for a fact? If you're relying on your multimeter to measure ohms, then it's not giving you the true picture. The rating on the subs are for impedance, which varies with frequency. The rating is an average. Your meter measures DC resistance. Resistance .neq. impedance.

If you take (3) 2 ohm DVC subs, and wire each set of (+) terminals in series, and wire each set of (-) terminals in series, you end up with two sets of series-wired (+) terminals, and two series-wired sets of (-) terminals (dual voice coil). If you then combine the (+) terminals and connect them to the (+) side of the jack plate, and combine the (-) terminals and connect them to the (-) side of the jack plate, you have wired the four sets in parallel.

2+2+2=6
2+2+2=6
6/2=3

3 ohms total load

Yeah, thats it !!!! I do understand that the resistance will change with frequency especially as the frequecy drops. But at a static state the resistance is close to 2 ohms. I am only concerned about the stable state at which the amp will run at. If I start at below 2 ohms the amp will have a short death.
Oh, by the way your tone was a little short, but I know I was a little frustrated in what I was trying to explain. Thanks, sorry my bad.....

I did not mean to come across as short at all. I wanted to explain it to you as concisely as possible. I'm not a picture guy.

If your amp is 2 ohm stable you're all set. If it's only 4 ohm stable, set the gains a bit lower and that should keep your amp from smoking.

Good luck with your install.

Yeah its 2 ohm stable, I think it will turn out good. Thanks, I will post pictures of the 3 sub set up, box is almost done.

You should get somewhere between the 2 ohm and 4 ohm output from the amp. Are you going to set the gains with your DMM? I'd use the midpoint wattage and 3 ohms to figure out the voltage.

Well I guess I learned something new today. Are you talking about before it clips?? I wish I would have bought an ossiloscope at an auction (10.00 bucks) I went to once. How do you use the dmm to set the gain?? I have always done it manually before. I know on the jl audio web site it tells how to do this with the dmm on there amps matched with their speakers. Please explain.

Here is a post on that from another forum I am on
http://www.icixsound.com/vb/showthread.php?t=27819

There are tons of multi-page amp gain tutorials on the web.

In a nutshell, let's use your situation as an example. You said that your amp puts out 1089W at 2 ohms. You did not say what it puts out at 4 ohms or how much power your subs can handle. So to keep this going, I'll assume that your amp is linear and puts out half power at twice impedance, and that your subs can handle a jillion watts each. Rounding the 1089W to 1100, that would make your amp's 4 ohm output 550W. You have a 3 ohm load, so we'll take the middle at 825W.

Volts = SQRT(Power x Impedance)

Your volts = SQRT(825 x 3) = SQRT(2475) = 49.75V


Disconnect the sub from the amp. Place your DMM across the amp speaker terminals and set it to AC volts. Set all of the head unit tone and equalization controls flat. Turn off any loudness or bass boost. Turn the volume on the head unit to zero. Turn the amp gains to zero.

Play a test tone on CD. I like to use 50Hz for subs. You can find these on the web and burn your own CD.

Set the head unit volume to the highest setting before you hear distortion. 3/4 is usually a good place to start. Turn the amp gains up slowly and watch the meter climb. Set the gains at the voltage you calculated. If it looks like it's tapering off before it gets there, then the amp is probably clipping. Turn the gain down and back up to just before the voltage flattens off.

Using a true RMS AC meter yields the most accurate results, for a meter. A scope is the best way to go. You don't need a high bandwidth scope for audio, 10MHz is fine.

OK, I figured close to the same somewhere between 45-49 volts ac. I did read somewhere that the speaker needs to be connected, but that doesn't sound right. Anyway, I also read that you should use the frequency where the sub is crossed over at. I am currently using 71 hz for low pass at 30 db slope. I have the capeability of 31 bands per channel. I use a PAA2 which is a 1/3 octive spectrum analyser, which came with a disc of test tones. It has pink noise, phasing etc, but the only test tone near my 71 hz is 50 hz. This 50hz test tone should work, right???
I now have the subs installed and they show 2.7 ohms at the terminal cup. I will post pictures of the box finished in carpet soon.

I would not use the crossover point because traditionally, levels are -3dB down at the crossover point. 30dB is such a sharp slope, though, this may not apply. I would think 50Hz is fine.

You may find that the 0dB tones on the CD are not loud enough. If so, try -3dB and then -6dB if you have to.