i have a quick question for you audio techs on this forum. I have a dual 4 ohm sub 300 rms which is wired at 8ohms and i have a 300 watt rms bridged amp at 4ohms.. will i have any problems running this setup as far as quality of sound, sound level, etc...

 

bump?

 

I have a similar set up in my G. I still have plenty of volume with running at 8 ohm. Your only going to be getting about 150 watts though.

"Dont start none, Wont be none"

 

It will work fine, you'll just be "wasting" half the capacity of the amp. If you replace the amp, get something that puts out full power to 2 ohms (or something that works on a range of impedances, like the JL amps).

-- Rob

 

could u clarify all this with the ohmage... what are benefits of running different ohms?


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ohm is the impedance on your current.. the more ohm the less the current (wattage) so if u have a 2 ohm amp running at 800 watts, it will be 400 watts if u run it at 4 ohms.. thats all i kno so far.. haha

 

Here's a question for you guys:

How does the ohm rating of an amplifier relate to the ohm rating of a speaker? What will happen if I run an amp at 2 ohms in conjunction with a 4 ohm speaker?

 

like mentioned above, the power is going to be cut in half

 

The ohm rating of an amplifier isn't adjustable. How ever much power your amp outputs depends on the ohm load(speaker) it is driving. Most car audio amps will drive loads between 1 - 8 ohms. Say an amp specs states it drives a load of 4 ohm with 400 watts and 2 ohm with 800 watts. You can find a 3 ohm subwoofer and hook it up and it'll get about 600 watts. The load varies linearly with the output of an amp due to Ohm's Law.

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A clarification as to what an ohm is..... Ohm is a measure of resistance. The more resistance (ohm's) your speaker is the less flow (watteage) your amp can push though the wire. An amp rated at 400 watts RMS @ 4 ohm's is only going to put out that wattatage to a 4 ohm load. Now lets say that speaker you connect only has a 2 ohm load the amp now has less resistance to work against and can put more power out to that speaker. The issue is that if you have an amp that is only stable down to 4 ohm and you hook it up to a speaker load of 2 ohm the amp will put out more power, but it will most likey overheat too. So thats why I say to connect it such that the amp sees an 8 ohm load. this way the amp shouldnt overheat on you. And im sure you will have enoough power. Hope that made some sence.

"Dont start none, Wont be none"

 

Amp Ohmage, 101:

Lets start with the most common scenario. You are using a bridged two channel amp to power your subs that outputs its maximum rated power at 4 ohms mono. You goal, with this amp, is to buy a sub or subs that ultimately give the amp 4 ohms.

If you're going to buy one sub, you want to buy the 4 ohm model. If you buy the 8 ohm model, the amp will only output half the power.

If you are buying *two* subs, you want to buy the 8 ohm versions, and wire them in parallel to give the amp the 4 ohms it wants to see. If you bought two of the 4 ohm models, you must wire them in series for 8 ohms and lose half the power of the amp. If you wire them in parallel to 2 ohms, you could overload the amp.

Amp Ohmage, 201:

We have monoblock amps designed to be used with subwoofers that typically expect to see less ohms than the usual bridged two channel amp (usually, 2 ohms). And now we have flexible amps like the JL ones which aren't locked into a specific impedance.

Most of the higher end subs today are DVC, meaning they have two voice coils. A DVC with dual 4 ohm coils can be configured to effectively be either 8 ohms or 2 ohms. A DVC with dual 2 ohm coils can be configured as 4 or 1 ohm. This adds more options, especially when you have more than one sub.

Bottom line: Pick the amp, find out what it expects to output maximum power, and then choose your subs accordingly. Or if you've already got the subs, pick an amp that can deliver maximum power to them. If it works out to 4 ohms, that usually means a bridged two channel amp. If it works out to 2 ohms, that usually means a monoblock amp.

<small>Disclaimer: I just woke up so there may be errors in the above. </small>

 

thnx dj.. good post

 

1 more interesting note that kinda contridicts the norm (well the norm for my limited knowledge of all amps) for amps. The higher end JL amps boast continuous power rating from 1.5ohm to 4ohm. So you can have a 4 ohm load and get 75W. Or a 3 (2, 1.5) ohm load and still get the same 75W. One thing that gets lost in the small print is that there is only 1 power supply for all channels so the power is adjusted to the least resistive load. So just make sure you use the same load across all channels and you are set=).

-JustICE