Amp help

polarity · 10-07-2009, 08:52 AM

From Car Audio 101

Quote:

Ohm's

Okay ohms or Ohm's law is the rule of resistance that something has. Most of you probably think about things like rubber and all having high resistance and that is correct. But in car audio we use ohms for what a speaker's resistance is at. For example if you have a sub that has a 4 ohm single voice coil. Than that sub can be wired up to an amp with the resistance of 4 ohms.

The next part of Ohms is power. If you look at any amp's specs you will see that is has something like 100 watts RMS x 4 at 4 ohms (150 watts RMS x 4 at 2 ohms) 300 watts RMS x 2 bridged output at 4 ohms (4-ohm stable in bridged mode) so lets look at the first one. This one states that is can run 100 watts per channel "or speaker" as long as each speakers has a resistance or Ohm's of 4. The second one states that as long as all the speakers are at 2 ohms the amp can put out 150 per channel. The last one shows that it will put out to 2 channels 300 watts a channel if there ohms are 4 ohms. "you will also notice that is says 4 ohm stable at ridged mode." This states that the amp was built for the load of 4 ohms and is able to be bridged.

The thing with ohm's is that the higher the ohms the more resistance. So when you go with a lower ohms rating it can have much more power to run that speaker. You may be asking well can I wire different ohm rated speakers to two different sets output on an amp? You can ONLY do this if the amp is setup for it. If you want to get relay technical about Ohms law just google it and click on any of the first few links that come up. Or just simply ask.

RMS

Now you may have notice in the previous section when watts were being explained it said RMS. Something like 100 X4 at 4 ohms RMS. This is very important when choosing an amp. RMS stands for root men square. In normal terms this means what an amp can continue to produce for long periods of time none stop. You may bee seeing things like 1200 watts MAX. In a few simple words this is a gimmick the amps will never produce this power and no matter how hard you try there just not going to make it. You always look at RMS when shopping for an amp. You will even see it on head units saying 50 X 4 max it is rely putting out around 12-15 watts RMS.

But I still don't understand why if I purchased 2 speakers that are 4 ohm when I look for my amp am I looking at what it outputs at 1 ohm. Just so I'm clear before I order something thought if I find a dual channel amp that is putting out 250 watts per channel at 1 ohm then I have the power I need to run them?

Thanks again man
-William

OVERZLUS · 10-07-2009, 02:37 PM

When you wire the 4 ohm DVC subs to a 2-channel amp, the total impedance will be 4 ohms with the amp bridged. So whatever the amp is rated at 4 ohms will be what you get out of it. I would look for this : *** watts RMS x 1 at 4 ohms (4-ohm stable in bridged mode).

10-07-2009, 02:37 PM	#2 (permalink)
OVERZLUS Base Member Join Date: Aug 2009 Location: VA Posts: 34 Drives: 09 Nissan 370Z Sport Rep Power: 16	When you wire the 4 ohm DVC subs to a 2-channel amp, the total impedance will be 4 ohms with the amp bridged. So whatever the amp is rated at 4 ohms will be what you get out of it. I would look for this : *** watts RMS x 1 at 4 ohms (4-ohm stable in bridged mode). __________________ '09 Magnetic Black 370Z 7AT \| 35% Tint \| Audio System \| Fast Intentions CBE w/ 12" Resonators Last edited by OVERZLUS; 10-07-2009 at 03:18 PM.