OK, because of cost concerns I've decided to go with a 2 channel, quality amp, instead of a 4 channel amp that, to get, I would have to sacrifice quality. I understand, that by running four (4 ohm) speakers on a two channel amp the OHM load drops to 2, correct? How you get this number I'm not sure, so if anyone can explain, in layman's terms please do so. Now, after reviewing several specs of amps I see that the RMS rating of a typical 200 watt 2 channel amp would be 50 watts/rms into a 4 ohm load. Now, here's what confuses me. The 2 OHM load continous power jumps UP to, let's say 75 watts rms with an increase in the THD, generally not so much as to be noticeable to the human ear, well mine atleast. My question is why does this happen when you are putting more of a load on the amp and is it generally safe to do so?
Your responses will be greatly appreciated.
Thanks,
Razorbacx
ok first off 4 subs at 4 ohms each would be a 1 ohm load not 2. if all subs are the same ohm then divide by the number of subs,ex 2 subs each at 4 ohms 4/2=2ohms you see?? now a lower number resistance means more power can flow,more resistance means less power can flow .
on a 2 channel amp if you run 2 speakers on each channel in paralell you have 2 ohms per channel which is ok. It is called 2 ohm stereo. you would take 2 subs and put both positives to the positive on the amp and both negatives to the negative on th eamp ,then you do the same for the remaning two subs on the last channel of the amp.
To clarify the issue, I am running two JBL GTO635 6 1/2's upfront and two MB Quart DKC169 6x9's in the rear. Both are 4 ohm speakers and I want to run them in paralell off of a 2 Channel amp. So, I would need to run on the front speakers two sets of POSITIVE Wires and two sets of NEGATIVE Wires straight from the amp on channel 1 and the same for the rear on channel 2. That will give me my 2 OHM load in stereo? See my attached figure that I roughly put together.
If the amp is in the back i would run speaker wire from the amp to the rear speakers then i would run wire off the rear speakers to the front speakers, i would run both rear left and front left together and do the same thing for the right this setup should give you double the power than the amp would do in a 4 ohm configuration. It dont matter how you run the wire just as long as each channel only has 2 speakers on it.But instead of running two sets of wire off the amp i would run the wires normal to the rears and then take wire and go to the fronts from the rear speakers. This is a rlatively easy setup to do and as for the distortion going up it should not be noticeable in a decent amp.
if you can run an amp at 2ohm stereo, your better off. Everone around where I live bridge everything, no matter what, then the do not understand why it blows up.
Keep in mind that if you run the front speakers from channel 1 and the rear speakers from channel 2 then you'll be losing Balance control. If you run both left speakers from channel 1 and both right speakers from channel 2 then you'll be losing Fade Control. If I had to make that choice, I'd prefer keeping the Balance control for the stereo effect (run the left's together and the rights together).
In Layman's terms, when you wire in Parallel the ohm load gets cut in half. When you wire in Series the ohm load gets doubled.
Example (this is for Single Voice Coil speakers and subs)...
Two 4ohm speakers wired in Parallel = 2ohm total load.
Two 4ohm speakers wired in Series = 8ohm total load.
Let me know if you want an explaination of wiring DVC subs...
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Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
Donate to the12volt.comThanks for the outstanding advice! wvsquirrel brings up another good question regarding OHM loads on an amp. If you run your speakers in paralell and get a 2 OHM load does the amp become more efficient than say running your speakers in series and achieving an 8 OHM load?
Can I get a recommendation from one of you out there regarding a brand or model of an amp that would be appropriate for my installation? I'm running two JBL GTO635 6 1/2's up front and two MB Quarts DKC169 6x9's in the rear (no sub). Both sets of speakers are rated at 60 WRMS.
BTW...I got my MB Quarts (DKC169) hooked up and they sound incredible right off the HU. I would highly recommend them. The Bass is solid and tight and the highs are crisp and clean. Best pair of speakers that I have ever purchased!
Thanks,
Razorbacx
The12volt gave me some clarification of efficiency a little bit ago. I used to think that just because a lower ohm load would allow the amp to produce more power that it also meant the amp was running more efficiently. He helped to clarify that this was not necessarily the case. Efficiency has more to do with factoring in the current draw and power lost to heat dissapation then just the impodence (ohm) level. So it actually looks like in some cases an amp may run more efficiently at a higher ohm level. Here's an excerpt from the12volt from that
thread I mentioned...
"My point is that efficiency of an amplifier and power output of an amplifier are not the same. Yes, an amplifier will produce more power at a lower resistance, however it doesn't mean that the amplifier is more efficient at a lower resistance. In some cases, current draw may be more than twice as much at 1/2 the resistance and the loss to heat may also be more than twice as much, making it less efficient while producing more power. Efficiency with an amplifier would relate more to the ratio of power output to current draw, and power output to power lost to heat."
And you would not necessarily be sacrificing "quality" if you went with a 4-channel amp. The main difference between most 2 and 4 channel amps is the power output. I haven't really seen that many 4-channel amps that can put out 150+ x 4 @ 4ohms. You can find some that would do that at 2ohms or at 4ohms mono, but usually not 4 channels @ 4ohms.
Since most component/coaxial speakers are 4ohms, your best solution for optimum SQ (if your headunit only has 1 set of RCA pre-outs) is finding a quality 4-channel amp that's rated at RMSx4@4ohms (in your case 60x4@4ohms). You would retain balance
and fade control, and would only have to worry about installing 1 amp. I said "quality" because a manufacturer of junk equipment will produce junk equipment regardless of if it's a 4-channel amp, 2-channel amp, mono amp, subs, etc... Junk is still junk, but in most cases it's more the manufacturer then a particular type of amp (ie 2-channel vs 4-channel).
If your headunit has 3 sets of RCA preouts (Front, Rear, and Sub) then you have some more options for optimum SQ (you can run multiple amps from 1 set of RCA pre-outs using RCA Y-adapters, but you end up losing either Balance or Fade control). You can either
a) Find two 4-channel amps rated at RMSx2@4ohms mono (in your case two 4-channel amps rated at 60x2@4ohms mono) and run the Front Left and Right speakers from 1 amp and the Rear Left and Right speakers from the other, or
b) Find two 2-channel amps rated at RMSx2@4ohms (in your case two 2-channel amps rated at 60x2@4ohms) and run the Front Left and Right speakers from 1 amp and the Rear Left and Right speakers from the other.
Either way (a or b) would also allow you to keep balance
and fade controls.
Obviously you will more than likely pay more for 2 amps then you would if you bought just one. It all comes down to
1) What you can afford
2) How patient you can be (i.e. it may take a little longer to find a quality 4-channel amp rated 60x4@4ohms at a decient price then it would finding 1 or 2 lower rated amps).
2) What you're willing to sacrifice (SQ, balance, fade, etc)
3) How much extra current draw your alternator can handle (because multiple amps will draw more power from the alternator than just 1 amp).
I'm getting ready to switch my system over to my Explorer, and will be installing 2 Kenwood KAC-649S 4-channel amps to push my components. Each amp is 80x2@4ohms mono, and retails for about $200-$250 a piece. They've actually come down in price since I bought mine a few years ago. But they are still running strong and work great for my mids and highs.
Hope that helped
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Squirrel
"No more Cpt. Kirk chit chat"
If its too loud, then you're too old
Donate to the12volt.com