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Old 24th August 2012, 02:01 PM   #1
diyAudio Member
Join Date: Aug 2012
Default amp power distrabution

Tried searching but no luck.

I have a 900w rms mono amp. 2 JL shallow mount single 3 ohm jl 13.5s.
If I run these in parallel does the amp send 900w to both subs or does it get split between the 2?
Now my understanding of parallel is wire one speaker to the other speaker then out to the amp. I hope this is the right term.

Amp is 900 rms @ 4 ohm so yes I know the actual would be a bit more in 3 ohm load.

Last edited by drk hitman; 25th August 2012 at 12:13 AM.
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Old 24th August 2012, 02:22 PM   #2
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Ok just found out the car audio guys I work with are flippin idiots. Asked this question to them and they said that only a mono amp is 1ohm. And if I hook 3ohm to a 1 ohm it will blow the subs because I would be pulling 6ohm from a 1ohm amp. I was stoopified. Then he said to never run a cap cause he ran a 3.0 ferad cap to his 1800 peak amp and it fried his head unit. I tried to explain that he should have been running a .5 ferad or maybe a 1.0 ferad. He said why would I do that? 3.0 is as big as u can get... I was done talking to him at that point.

So could someone with intelligence help me understand how this works. I don't know much but I know more than that guy.
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Old 24th August 2012, 05:36 PM   #3
macboy is offline macboy  Canada
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If you connect two 3 Ohm subs in parallel you will create a 1.5 Ohm load for the amp.
If the amp is rated to drive 1.5 Ohms, then all is good. If not, you will likely damage the amp. If the amp can only handle 4 Ohms (or higher) then you can wire your subs in series to get 6 Ohms. Then your amp will be happy, but will not likely put out the full 900W.

Make sure to google series and parallel so that you understand what you are doing. You clearly do not yet.
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Old 24th August 2012, 09:04 PM   #4
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So I think this is what I need.
My subs are 2 13.5 jl shallow mounts 600 rms
Amp is Kenwood 1800 peak/900rms 1ohm stable.
If I can wire the subs to a 4ohm load it should run the subs at third max rms. These 3ohm subs have me confused.

Thank you macboy for giving me an idea about the wiring. I had the terms flipped.
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Old 24th August 2012, 09:31 PM   #5
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Location: Rotterdam Netherlands
iirc that amp will also be 900W at 2 ohm.

So wire the speakers in parallel, and you'll give them 900Wrms (max) which will then be split evenly between them, so 450Wrms per speaker.

As for caps: there have been many discussions about this and the best ones with loads of measurement date being presented, showed the cap will hardly do anything. So add it, or don't. Won't make much difference.

BTW, you said in the first post you had 12's, now they are 13.5's so which is it (13TW5's? Tried getting one of those, but am sticking with my Aliantes for now...)
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Old 24th August 2012, 11:32 PM   #6
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caps do the same thing that they do inside the amp. help smooth electrical "noise" in the power system. i don't/won't run one in a car, unless there is such a ripple to dampen, that the batteries cannot react to, but i do use a 2farad on my bench supply. if the guy's head unit fried, this is simply because he did not have good wiring in his system, and it caused an issue, like rca grounding/shorting/looping, or the remote grounded out. the only difference the cap could have possibly made, was the presence of extra wires/connections to get in the way. btw, you can get much larger caps. about 2k, my best friend had a 16farad alumapro? cap unit. made a purdy looking distro block, but did little more than kill the battery repeatedly.
the only place power is made/supplied is the alternator. the battery stores it, but it still has to be replenished 2x by the alt. 1 farad is about 1/100th of a stock battery storage....
as mentioned, power is split-up between the 2 subs.
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Old 25th August 2012, 12:17 AM   #7
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Oops sorry bout the sub size mix up I corrected it.
The amp is a KAC-9105D
For some reason the wiring link did not show up in my last post.
I'll try this

Last edited by drk hitman; 25th August 2012 at 12:22 AM.
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Old 25th August 2012, 08:38 PM   #8
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Location: Rotterdam Netherlands
Yep, that wiring is correct.

If the pic I found on the net is correct, you will have double outputterminals for the subs on the amp. So run a set of wires to sub 1 (from this connector) and run a set of wires to sub 2 (from the other half of this connector). If the subenclosure permits this obviously, as this won't work if you only have a single input into the enclosure...

Last edited by ric-paul; 25th August 2012 at 08:40 PM.
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Old 25th August 2012, 09:14 PM   #9
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So by wiring 3ohm to 3ohm like in the above link, what would my final ohms be.
I just don't want to fry the subs by over powering them to much.
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Old 25th August 2012, 09:50 PM   #10
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3 ohm parallel with 3 ohm makes 1.5 ohm

The amp is limited to 900Wrms @ 1 ohm. The amp is 900Wrms @ 2 ohm, so it is safe to say it will do 900Wrms @ 1.5 ohm.

Hence me saying it would deliver 450Wrms per sub.

Do note these are all theoretical numbers you will only achieve by actually playing testtones, but for all intend and purposes, this is how we normally discuss an amp's maximum useable continuous output.
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