how to tell

doberman_52 · #1 10-22-2006, 11:28 PM

whats the thing about the ohms on an amp and subs, 2 ohms wont work with a 4 ohm stable amp or something like that, where can i learn that, i hear this stuff all the time and dont know what it means, have a set of 12" rockford fosgate he's (200 rms, 400 max) and was wondering what would be a good amp for those

vinnym86 · #2 10-22-2006, 11:40 PM

ohms is the measurement of resistence. you can learn more here. continue reading afterward, there's a button to the next chapter at the bottom.

doberman_52 · #3 10-23-2006, 12:11 AM

that still doesnt tell me why a 4 ohm stable sub wont work with a 2 ohm stable amp or something like that, ive known what ohms were, learned that in computer systems
i was told this when i was looking for an amp for my rockfords

vinnym86 · #4 10-23-2006, 04:04 AM

if you read the next chapter...

Quote:

Originally Posted by bcae1

Lets say we have a 100 watt (we'll cover 'watts' soon) amplifier and it can drive a minimum ohm load of 4 ohms. This means that it can produce 100 watts into a 4 ohm load and any lower ohm load will cause the amplifier to fail.

read on to understand why.

doberman_52 · #5 10-23-2006, 08:58 AM

i read both pages, so the higher the ohm number the lower the resistance, i didint quite understand that page after reading it 3 times

PaulD · #6 10-23-2006, 10:53 AM

it's kind of a paradox until you understand what the ohm load of a speaker really does to an amp. If it's rated at 100 watts RMS into a 4 ohm load, the 4 ohm speaker is kind of like a knob on a faucet to the amp. 4 ohms is a certain resistance to the flow of electricity - the higher the ohm number, the greater the resistance to the flow. If I put a 2 ohm speaker on the amp, it will (in theory) draw twice as much current (and power, so it will TRY to put out 200 watts RMS) - it would be the same as opening the faucet knob to allow twice as much water to flow thru. All that extra current will cause a LOT more heat to be built up in the amp, heat the amp may not be capable of dissipating, and will destroy the amp sooner or later.

Remember the lower the ohms, the more current and power pass thru.

doberman_52 · #7 10-23-2006, 11:28 AM

ok, so the resistance differances heat the amp to much, causing it to go, som my 2 ohm amp would be puting to much power to the 2, 4 ohm subs, or is that ok (I think this is how mine is set up, my amp is a 100x4 jenson, looking to get a new amp though), a 4 ohm amp cant power a 2 ohm sub because the resistanc is to high, causing it to overheat, right?

PaulD · #8 10-23-2006, 01:06 PM

some "4 ohm" amps are designed to play into 2 or even 1 ohm loads .... all depends on the design. I would keep the 4 channel amp for your midrange/tweeter type speakers and get a class D amp for sub(s) that is designed for lower loads.

doberman_52 · #9 10-23-2006, 01:30 PM

its still a little confusing though, does it change if u put 2 or more subs on one amp? also the jenson isnt mine, i currebtly borowing it from a friend till i can get a new one,

vinnym86 · #10 10-23-2006, 04:23 PM

yes it does. Say you have Two 4ohm drivers, and you wire them in series to your amp. the amp will see an 8ohm load. this is because of the way you've wired the drivers. Now, if you wire them in parallel, then the amp will see a 2ohm load. You can have even more options with Dual Voice Coil (DVC) subwoofers. remember though, even though a 2-ohm load will allow for theoretically double the power, it doesn't mean the amp can supply it. That is why you need to make sure the amp you buy is built to handle it.

doberman_52 · #11 10-23-2006, 05:16 PM

I have them set up as a series, 2 of 4 chanels, will it be ok to hook them up parallel? they are the fosgate he, the amp is a jenson a4000 100Wx4 channel, it says to use 2, 4 or 8 ohm speakers
thanks
still confusing, but electricity can be

vinnym86 · #12 10-24-2006, 12:00 AM

^that post confused me...

you're saying you want to use your 4-ch amp to power your subs? why? no, buy a mono-amp (a 1-ch, d-class). use the 4-ch amp to power your component speakers. If your subs are rated at 200rms @ 4-ohms (you have 2 of them, right?), If they have a single voice coil, then buy a 400w rms mono-amp stable at 2-ohms and wire both subs in parallel.

doberman_52 · #13 10-24-2006, 09:01 AM

this is an amp that i am borowing from a friend until i can get one of my own, ur saying get a 400w bridgable? ive been thinking about that, i just need to pay my insurance here and in a month or so i will be getting a new one, what is a decent 400-500w amp for cheap,
thanks

vinnym86 · #14 10-24-2006, 09:45 AM

no, not a bridgeable amp. bridging is theoretically drawing more power by combining two channels together. This is a 1-channel amp.
If you are looking cheap, consider Profile or HiFonics. They're about as cheap as they get before getting too crappy.

doberman_52 · #15 10-24-2006, 11:25 AM

Ok, I get the bridging thing now. Would any of theese amps be ok, i like the AP1000, 480W RMS x 1 Bridged or 240W x 2 both are for 4 Ohm speakers, it should be good for my HE's I think
http://www.crutchfield.com/S-xvnf0IO...rand%7CProfile
What is tri-way capable mean? - 2 speakers and 1 sub?

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