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Old 11-18-2015, 12:49 PM   #1
OldElPaso

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4ohm output to 8ohm load

Hello everyone. I had a post about this but my explanation was to long and I think I confused people. So my question in simple.
What will happen if I connect 2x4ohm speakers in series to a final 8ohm load, and then connect that 8ohm load to one of the outputs on my head unit. The outputs on my head unit are 52W@4ohm

My main concern is will it fry. I know doing the opposite will destroy your head unit. So connecting a 4ohm load to an 8ohm output.

Hope you can help. Thanks
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Old 11-18-2015, 01:17 PM   #2
basicxj

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It is very rare that a head unit will actually put out 52 watts X 4 (most times this is a "max" rating at full clipping).

Yes, you can connect an 8 ohm load- if the internal amp can drive a 4 ohm load it will have no issue with an 8 ohm load, but you will only see about half the head unit's "RMS" rating for 4 ohms when doing so.
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Old 11-18-2015, 01:38 PM   #3
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Look, I understood the first time you asked this question. The short answer is YES, you can wire two 4 ohm speakers in series presenting an 8 ohm load, NO PROBLEM, YOU ARE COMPLETELY SAFE. This will present absolutely no danger to your HU, PERIOD.

But the reason you may have not gotten as simple an answer as you were looking for was, in my case anyway, I was wondering not WHETHER it can be done (it certainly can), but why in the world you would WANT this done.

Most folks have problems with their front and rear speakers NOT BEING ABLE TO KEEP UP WITH THEIR SUBWOOFER, not the other way around. Which causes me to want to ask a lot of questions about how your system is set up. For instance, by wiring the front and rear speakers in series, you will lose fader control...why is this worth it? I understand you are level matching the gains of your sub amp, but honestly dude, if the front and rear speakers are too loud, just turn the subwoofer amp gains up to match them.

I mean, the TRUE RMS power of your HU, although I do not know the model, is probably something like 20 watts RMS, not 52 watts at 4 ohms which is more than likely peak. So doubling the impedance (and cutting two HU channels out for that matter) of two channels will cut the power down to about 10 watts RMS at 8 Ohms.

I just don't see why you can't raise the sub amp gains to match the other speakers. As long as you are careful not to push your subs ionto gross audible clipping and distortion, you should be fine.

Is there something I'm missing here?
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Old 11-18-2015, 04:07 PM   #4
neillio

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You are better off buying an inexpensive 2ch amp.

http://www.ebay.com/itm/CADENCE-XAH-...UAAMXQiNdReBss
80wrmsx2 would be great for a front sound stage.

You can then use 2 channels of the 18-20wrms that the headunit puts out (4 ohm load) for rear fill speakers.

Do you really want 9-10wrms going to your speakers? You'll constantly have to crank it to 90%+ volume just to hear above road noise.
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Old 11-18-2015, 06:02 PM   #5
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Quote:
Originally Posted by neillio View Post
You are better off buying an inexpensive 2ch amp.

http://www.ebay.com/itm/CADENCE-XAH-...UAAMXQiNdReBss
80wrmsx2 would be great for a front sound stage.

You can then use 2 channels of the 18-20wrms that the headunit puts out (4 ohm load) for rear fill speakers.

Do you really want 9-10wrms going to your speakers? You'll constantly have to crank it to 90%+ volume just to hear above road noise.
This is likely the best solution to the problem.
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Old 11-18-2015, 09:17 PM   #6
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I concur.
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Old 11-19-2015, 12:45 PM   #7
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I agree to MOSFET's concurrence with Mordrid1's confirmation of Nellio's extension of Basicxj's excellent answer.

OP - you will not fry anything with what you propose. It just won't sound good.
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Old 11-19-2015, 05:07 PM   #8
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HU's rms power is very limited to start off with even at 4 ohms, at 8 ohms you will be barely even getting any wattage. Get an amp to power them properly.
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