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Old December 2nd, 2010, 01:11 PM
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Question regarding differences between 2ohm and 4ohm speakers connections

Hey all, anyone here good with car audio? I googled this but am still a bit confused with my specific question. On my 5 channel amplifier manual, it states the rms power rating for both 2ohm and 4ohm setups. The power output on the 2ohm set up is much more higher than it is for 4ohms and I'm not sure if my speaker set up is for 2 or 4 ohms. I'm running components on each of the 4 channels in my D. Each channel has a seperate crossover that you stick behind the mid speaker, than it branches out to a tweeter and that mid-speaker. Than on my last channel, it goes to a sub wired simply to the + and - terminal. Does anyone know if this is a 2 or 4 ohm set up? Not sure what the components were set up for but they are made by polk. Any help is appreciated, wondering if I will have enough power for my 15 inch kicker sub. The manual says the speakers uses 750 watts rms (peak is like 1500 or something). On the manual for the amp, it says the monoblock output for the sub puts out 280 watts rms on 4 ohms, and 600 watts in 2ohms. Kinda confused how to get the 600 watts to the sub.

------ Follow up post added December 2nd, 2010 10:21 AM ------

I found this diagram, I see 2 voice coils on my kicker 15inch sub, wondering if this is the right way to do it.

http://www.the12volt.com/caraudio/wo...s.asp?Q=1&I=22
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  #2  
Old December 2nd, 2010, 02:14 PM
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Neill Thornton
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It all depends on the subwoofer. Do you know what model it is, and it's already in a box I assume.

Break out your trusty multimeter (yay!) put it on the "Ohms" setting, and measure what your sub is by placing the probes on the plus and minus terminals on the box while disconnected from the amp. Should be 2, 4, or 8. Then you will know. Depending on the sub you may or may not be able to re-wire it.

You can do the same for the crossovers, measure the input. You must disconnect them from the amp first.

But in the end... forget about the numbers. How does it sound? Who cares if its 2 ohms or 4 ohms, as long as it provides the sound you want.
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Old December 2nd, 2010, 02:18 PM
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Your speakers are probably 4 ohm units and the crossovers may or may not up that to 2 ohms. It has to do with whether or not they are wired in series or parallel. The subwoofer could be 4ohm or 2ohm...if you post up the model numbers I may be able to help a little more but I would try running everything in a 4ohm condition before trying to bridge to 2ohm. 600W to a 15" sub is cool but can also be deafening! I once ran a system that consisted of 9 speakers/subs in a '93 Mustang and included almost 2000W of power...while neat in theory, I really didn't need the 160+ decibels it created at the driver's seat!

As a side note, the wiring diagram you posted is correct if you do want to make your 4ohm subwoofer run at 2ohms
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Old December 2nd, 2010, 02:20 PM
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Ahh, I just saw the addition you have to your post. Measure each coil with your multimeter. if they are already 2 ohm coils, you are either going to have connect just one, or wire them in series (the second picture of your link) to power them both. This will reduce your total power.

If they are 4 ohms a piece, you can wire in parallel (the first picture) and get a 2 ohm resistance total. This will give you more current output.
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  #5  
Old December 2nd, 2010, 02:35 PM
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The speaker impedance cannot be measured with an ohmmeter as it is impedance not resistance. Speaker impedance ratings are nominal as they vary some with frequency. Still ohm ratings are used for general guidance. More important is speaker efficiency - db/m/w. The higher the efficiency the less power necessary to obtain desired volumes. It takes 10 times as much power to drive an 87db/m speaker as an 97db/m. Stated another way, a 10 watts in 97db/m speaker will be as loud as 100 watts into a 87db/m speaker. Most speakers are damage by matching them to inefficient / underpowered amplifiers. You would be hard pressed to supply too much power and thereby damage a speaker because as you turn it up louder, applying more power, the speaker moves more thereby cooling the driving coil. In good systems pain is reached before speaker damage. Speakers are more commonly damaged when someone attempts higher volume with underpowered amps. In an attempt to obtain the desired volume they overdrive the amp, to cutoff. That 750 watt rated speaker can be supplied by a 1000+ watt amp without damage. Since you've already selected your speaker I suggest a bigger amp just to supply the sub because they will suck up some power attempting match the volumes of your other speakers and to overcome outside noise in a car. Just my 2 cents, fwiw.
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Old December 2nd, 2010, 03:04 PM
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Found the manual, lots to read here as well! Im at work but I'll read when I'm at lunch. Heres the link to the manual
http://www.kicker.com/sites/default/...gual%20e01.pdf

I got the Soloclassic 15" SC15 sub due to the small profile space of the box needed.

I see the 2 diagrams on the pdf and I'm trying to figure out if 2ohm is the one on the left or on the right. But I guess my main issue is trying to figure out if the component set up I got on each of the channels of the 4 channel part of the amp is running the amp on 2ohms.

Ok I see what you guys mean now, I think mabye I bought too much sub for this amp. Because the amp in rms is 750 watts and this amp pushes only 600 watts rms in a 2ohm load. Damn, if I gotta buy another amp I gotta figure out where to put this, thats why I bought a 5 channel to make it easier, or I could just buy a smaller sub I suppose. Ok I just read the manual again and I see that to drop the sub to 1 ohm you wire it in parralell, like on the left. I'm just curious what the ohms are when you run it with the stereo channels with those crossovers. brb
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Old December 2nd, 2010, 03:12 PM
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Look at the subwoofer itself and there should be a number behind the part number...such as S15C2 (2Ohm) or S15C4 (4Ohm)
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Old December 2nd, 2010, 03:24 PM
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Quote:
Originally Posted by DieselDef View Post
The speaker impedance cannot be measured with an ohmmeter as it is impedance not resistance.
Damn, you are right... ugh. That was my blonde moment for the day.
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Old December 2nd, 2010, 03:25 PM
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Quote:
Originally Posted by jefhuf View Post
Look at the subwoofer itself and there should be a number behind the part number...such as S15C2 (2Ohm) or S15C4 (4Ohm)
I will look when I get home, I thought they were all the same, the shop didn't say a thing about what I was trying to do, guess they were just trying to move product. Do you guys think that 600 rms is enough to hit that 15" 750 watt rms? Or should I buy a new amp or subs? I'm pretty sure the shop will still let me trade down to a 12" sub which I see is rated at 600 rms. I don't know what do you guys think?
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Old December 2nd, 2010, 03:46 PM
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From what you posted earlier, and not seeing your amp instructions, it sounds like your amp will supply 600 watts max when wired to supply one speaker. The fifth output can most likely be used to drive a separate dedicated amp for your subwoofer. That is a common occurrence because of the high power demands of subwoofers, commonly taking 4 or 5 times or more as much power as your sides. A separated amp for the sub may not be as space consuming as you think.
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Old December 2nd, 2010, 04:14 PM
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Here is the specs as listed in their website. http://www.polkaudio.com/caraudio/sp...nnel/pa1100_5/ Supposedly its 600 rms at 1 ohm, which is what i was planning to do as. Just want to run only one sub. Your right about the bridging the subwoofer channel, I see it now on that site. It says you can bridge the sub channel to a PA600.1 If I have to bridge to another amp than so be it, I was hoping this one amp would be enough. Guess that fifth channel is more for like 2 10's or mabye 1, 12 perhaps, or any combo of speakers that don't have much power demands. Thanks all.
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Old December 2nd, 2010, 05:32 PM
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The site doesn't state if the power ratings of the amp are rms or peak power. Preferably they're providing rms ratings. The power that amp makes available for the sub would have to be for a smaller sub than you've selected. But, given that your side speakers are not likely to be high efficiency, 95db/m/w or better, (probably eight inch?) you're still going to better off with a separate amp for a subwoofer. You'll most likely need the 125watt per channel for the sides.
That amps sub out can most likely be tapped to simply be a driver for a dedicated sub amp. You may be able to get away with using that amp if you use it with a subwoofer that's high efficiency and thereby get accurate reproduction. In order for a speaker to produce frequencies below 45-50 hertz they have to have a LOT of power. You can only get away with less power when high efficiency speakers are used. This is one time when it's generally true that if some is good then more is better and a whole lot is best.
I hope I haven't fogged the issue.
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Old December 2nd, 2010, 06:07 PM
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Quote:
Originally Posted by DieselDef View Post
The site doesn't state if the power ratings of the amp are rms or peak power. Preferably they're providing rms ratings. The power that amp makes available for the sub would have to be for a smaller sub than you've selected. But, given that your side speakers are not likely to be high efficiency, 95db/m/w or better, (probably eight inch?) you're still going to better off with a separate amp for a subwoofer. You'll most likely need the 125watt per channel for the sides.
That amps sub out can most likely be tapped to simply be a driver for a dedicated sub amp. You may be able to get away with using that amp if you use it with a subwoofer that's high efficiency and thereby get accurate reproduction. In order for a speaker to produce frequencies below 45-50 hertz they have to have a LOT of power. You can only get away with less power when high efficiency speakers are used. This is one time when it's generally true that if some is good then more is better and a whole lot is best.
I hope I haven't fogged the issue.
I believe continous means rms and dynamic means peak. It's on the brochure that I have at home, the peak power rating was at 1200 watts I believe. And whats weird is the amp they recommend on their site to bridge is the same power rating as the 5 channel amp, does this double the output to like 1200 rms? Oh I found the link to the manual, gives the rms rating and for both 2ohms and 4ohms, its still 600 watts rms. http://www.polkaudio.com/downloads/m..._31March08.pdf
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Old December 2nd, 2010, 09:09 PM
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I'm just going to run 2 L58's, the square eights, those are 300 rms so shouldnt be any trouble, guess I'll have a spare 15 in the bedroom lol
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Old December 2nd, 2010, 09:34 PM
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It looks like the 1100 amp will drive a sub but doesn't allow bridging for more power at the sub. Your sub is rated at 2 or 4 ohms, 87db/m/w and 750 watts. The rated power for the speaker is not nearly as important as its efficiency. I've driven speakers rated 88db/m and 250 watts with 1000watts per speaker. If the power is clean the speaker can take 100% higher power, or more. An amp rated at half the power of the speaker will sound lousy if played loudly and sooner or later damage the coils. You might want to use that amp for the sides and either a second higher power amp for that sub or another, higher efficiency sub.
I've been stating this under the assumption that you'll be driving the speakers loud enough to hear the music clearly, and want channels balanced, over the ambient sound levels (quite loud in a Rover). If your not, you may get away with using only that amp for everything. No matter what you do it won't sound as good as your home system.
It is because of the power requirement to reproduce low frequencies that the better home subwoofers have their own integral high power amplifier.
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Old December 2nd, 2010, 10:10 PM
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Neil, I would recommend going back to the shop and listening to some 8" subs before you commit to that route. For my personal taste I do not think that anything smaller than 10" will produce the lows efficiently/effectively. I installed a single 10" (2ohm Alpine) in my D90 with a Rockford Fosgate Punch 300 amp and I think it is a great combination. It's in a sealed box so the bass stays tight and accurate
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Old December 2nd, 2010, 10:43 PM
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Good advise from Jeff. As a rule, it takes a larger cone to be able move the amount of air necessary to reproduce the bass notes. Some long travel smaller cones do a decent job but they are power hogs. Usually the larger cones with better efficiency sound better and don't require as much power.
Unfortunately, most stores selling car audio equipment don't explain all the factors that should be considered before buying. And something to remember, they always sound differently in the store than in the car.
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Old December 3rd, 2010, 12:27 PM
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I'm calling a polk technition today just out of curiosity so lets see what they say, thanks for the advise everyone.

------ Follow up post added December 3rd, 2010 10:44 AM ------

Ok so I talked to a tech at Polk and he said it will work but that it depends on how loud i listen to my music. He said there is little difference between a good 600 watt amp or an 800 amp watt, whats important is what I expect out of it. If I want to do SPL's he said to get add another amp to power the sub but if I'm just going to listen to it with normal expectations than it should be fine. But as far as damage he said shouldn't be any problems as long as I don't turn it up to a level wheres its clipping or distorting. So I guess I'll hook it up and see what happens. Also I forgot to look at which speaker I have again 2 or 4ohm, he said that makes the difference as well.

------ Follow up post added December 3rd, 2010 11:15 AM ------

Ok I called Kicker as well, and the tech said that it really matters if the sub is 2 or 4ohm, he said it makes the difference because if its a 4ohm speaker I will get the full 600 watts from the amp, but if its only 2ohm than I'll only get 280 watts so he said to make sure I got the 4ohm, if not I should return it, gonna rush home during lunch to check hehe.

------ Follow up post added December 3rd, 2010 11:15 AM ------

I apologize for the speaker drama.
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Old December 3rd, 2010, 04:07 PM
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As an FYI, sure it will say 300 watts into 4 ohms and 600 watts into 2 ohm, but in reality the sound level is not that different. First, doubling power only gets you 3 decibles. Second, even if it does double in power when resistance is halved, the limit on the amp is the power supply so you will be limited in the peak volume of the speaker. ie 600 at 2 ohms will result in 700 watts peak and 300 rms at 4 ohms will result in close to 700 watts peak too.

In the end, I am pretty sure 1 15in sub will be plenty loud and even two 8s will be really loud down to about 30hz. By way of comparison, my lotus with a fosgate punch 200 and one 10in is near ear bleed levels. When I was running 2 12in orions (very efficient speakers) with the same amp I could make the windows rattle in my old car.
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Old December 3rd, 2010, 05:01 PM
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Hmm that makes sense, but I just want to do it right just so I don't have to think about it or when something does get damaged I want to make sure its not my fault hehe. Ok I made a mistake above, its suppost to be 2ohms subs wired in parrellel will get kicked down to 1ohm for the full 600 watts, the 4ohm sub (which I just found out I have...crap) than it gets kicked down to 2ohms and gets only 280 watts. I called another tech at kicker and he says it would work but he wouldn't recommend it, he said get another sub amp with at least 1000 watts rms and be done with it, so I think thats my choices, exchange this 15 for a 2ohm one (4ohms are used for 2 subs or more wired in parrellel then it lowers the ohm but ups the power) and then get a seperate sub amp, or use smaller speakers like those 2 L5 8's I already have. Decisions decisions. I remember orion, are they still around?
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