amp question - please help me understand

How does an amp push out more watts with less ohms?
For example:
100W x 2 @ 4 Q
vs.
200W x 2 @ 2Q

Which is better? Please explain the difference in sound.... thanks.

ohms is resistance, if you remeber elementry electronics, electrons follow the path of least resistance. With half of the resistance(going down from 4-2ohms) the amp is able to do twice as much work(watts) with same voltage.

do a search on the internet for "ohms law" ...start reading. (4 variables makes up ohm's...voltage, amps, resistance, watts) Ohms is a measure of resistance....lower resistance = more wattage. Distortion usually increases as resistance decreases. The biggest issue with running at 2ohm is overheating, not sound.

Thanks. I think I understand. How can I make sure I get an amp that doesn't overheat and/or how do I keep them cool?

In the instruction manual or at the shop that sells the amp should be able to tell you low the amp can run stable. Most are 4 ohm stable with a few from each manufacture being stable at 2 ohms. There are only hand full that are stable to 1 or even a .25 ohm load.

Also, most specs give the RMS at 4 ohm. How do you know what the RMS is at 2 ohm??

I don't understand what you're saying Jason.
Should I look for an amp that says 2ohm stable in the specs??

I am assuming you are looking at a sub amp. The first question is what subs are you running? One 4 ohm? Two 4 ohm?(will run in a 2 ohm load when wired in parallel) One 2 ohm?
Once you know what you are running with it, you can pick out an amp that will handle the load

Actually I need an amp to run four speakers inside the boat. They are rated at 50watt RMS and 220 watt peak.

Ok you are running speakers and not subs. If these are the only speakers in the boat, you really should use a 4 channel amp. The one you are asking about is a 2 channel. You can run the 4 speakers off of it but you won't have as much adjustment as a 4 channel

okay. I've been getting conflicting advice about the 2 channel vs. the 4 channel.

I have a sub, no idea what it is just yet since I have to take it out of the boat. The amp that is attached to the sub right now is a
Pioneer GM3000T
200 watts
2 channel
40watt RMS x 2

Should I sell that and get something bigger to run the sub since I'm going with a new system anyway??

P.S. I'm looking as cheap as possible for a 4 speaker 1 sub set up inside the boat, no tower speakers.

that is the same amp 100 @ 4 is the same as 200 at 2 right?

Alan,
It's the same amp as what? I only have one amp. My thread started with a question regarding the ohms, not a specific amp.

If that is in the boat already go with atleast 40W x 4 amp. You should be able to get one for around $200. It will be a two amp setup but it will be alot cheaper and easier than trying to go with one larger amp to run both speakers and a sub

Thanks Jason. I will look into getting a 40watt RMS x 4 amp for the speakers and stick with the amp I have now for the sub.

I picked up a sony 4 channel 444w off ebay for like 50 bucks. Would probably work just fine for your application with the gain turned down a bit. do a search on 4-channel amps. relatively inexpensive.

"gain" is an adjustment on the side of the amp; how much power the amp is pushing.

yea there is a lot of inexpensive good stuff on ebay. if I have the chance to get a more powerful amp for the same $$, should I do that since I will be building a much bigger system in the future??

yes, but be leary of certain brands that claim high max wattage. If you can always find the RMS values, that is a good determining factor in how good the amp really is. For example I can get a 2000 watt audiobahn for the same price as a 600 watt diamond, but the audiobahn lists 2000 watts max(if lighting hits it) where as the diamon lists 600 watts rms. Sorry if this confuses you more

For instance, this item # 5752604058 would be a good amp to get

ronia if im not mistaken a 100 watt two channel amp @ 4 ohms will put out 200 watts at 2 ohms since there is 1/2 the resistance.

yes you are correct but that wasn't my question. My question was why and what effect does it have on the system.

http://jlaudio.com/amps/5005.html this amp will deliver all the power you need to all 5 channels. Not sure how much you are looking to spend. You can find it online for about $600 and if you ever wanted to upgrade speakers the amp will handle a pretty good setup.

fewer ohms = more watts with the same equipment. i realize this is not addressing lots of variables. but essentially, if you can run lower ohm levels, your amps can generate more watts.

Nacho,
what would you recommend to power 4 speakers inside the boat rated at 50watt (or 100watt) RMS .... would you recommend a 4 channel amp and going with 4 ohms or would you recommend a 2 channel amp going with 2 ohms??
Everyone has a different opinion on what to do.

Ryan,
Thanks but I'm trying to stay as inexpensive as possible.

1st thing. I can't tell if you're confused on this issue or not. Channels and ohms = Different things/not correllated at all. Again, i can't tell if you understand this completely or not at all. Channels are the outputs on the amp. like front and rear/ left and right. But you don't have to run a 4-channel in 4 ohm. or a 2 channel in two ohm. it all depends on the speaker setup.

As stated above, a 2 ohm load (resistance) is going to be more efficient = more watts with same amp draw.

Also, unless you're ready to unload a fat wad on a 5 channel amp like stated above, you need to consider separate amps for subs and "highs" (5 1/2s; 6x9s; etc).

Basically, it sounds like you need a new amp for your highs. It could be a 4-channel if you're concerned with fading and balance (like more or less volume in the bow area, or more on the tower. I know you're not to that point yet. just example.) Or a nice 2-channel that you simply wire to four speakers.

the Ohm load is determined by the speakers. I would guess they're 4 ohm. are they factory speakers?

Ronia ~ you are not looking to due a killer set up so just keep it simple. Use the amp you have now for the sub and get a new 4 channel amp for your boat speakers. If your speakers are rated at 50w RMS your amp should be the same are bigger. Just run each speaker to each chanell and rock on.

Ronie,

This may be more information then you asked but it explains in detail the anwser to your original question.

http://www.bcae1.com/bridging.htm

Nacho,
I understand the 4ohm, 2 ohm thing. I was told that running speakers 2ohm causes the amp to heat up and also has more distortion in the speakers. But the speakers are inside the boat in the open air, direct drive so I doubt I'll notice the distortion.

I just want to power 4 speakers inside the boat rated at 50watt RMS as inexpensively as possible. Be that with a 4 channel amp running two speakers into each channel, or with a 2 channel amp and running the 4 speakers in parallel.

With mids/highs the ohm setting isn't likely to be something you can control. Its determined by the wiring in the speakers - the resistance. I just bought two JL 12" subs and I might try to figure how to get them to 2Q. Just grab a 4-channel (I mentioned sony 444, I put this amp in last weekend) w/ a name behind it. Try to get one w/ input and outputs. That way you can run the signal wires into the new amp, then out to the sub amp, if you can mount them close in the boat. 2 channel 200 watt RMS, it will save you some cash.

Distortion can be higher, but is usually not very noticable, especially in a high quality amp. As far as overheating...when an amp is running in 2ohm there is close to double the current flowing through it, when the current flows through the transistors, a by product is heat. With a decent amp you'll be fine, but pushing an amp @ 2ohms during the summer can cause some to shut down, in order to cool down.

Nacho,
so which do you recommend, the 4 channel or 2 channel? I have a seperate amp for the sub.

I guess 4. I run 1 2-channel and 1 4-channel on my highs. I think have 10 high speakers. It would be nice to have a channel to each speaker, but whatever. so obviously 4 channels are shared 2 are independent. Grab a four channel, more versatility.