Ohms

RoboCod · 25 Sep 2006 at 00:27

Can someone just explain how higher Ohms is better for sound?

I have just purchased a new 4 channel amp for the car and it has the choice of 2 or 4 ohms. If Im right it means better clarity in the sound? :confused:

./dunce

daz · 25 Sep 2006 at 10:22

An amplifier is designed to work with a certain matched load. This can be any number, but it is at the matched load that the amplifier will generally produce the most power at the lowest THD.

Higher or lower is not inherently better.

Dr.EM · 25 Sep 2006 at 10:24

When an amp has a rating like this, the lowest load it can power is 2ohms. Smaller loads take more power, so using a 2ohm load over a 4ohm produces twice the power (bear in mind that only sounds 10% louder though). It is often the case that an amp driving very small loads produces more distortion, which is why you may have heard 4ohm is better to use. Also, 2ohm is low in any terms and you'll have to make sure the cabling is thick and the connections are good to avoid loosing too much power. Ultimately though, I wouldn't worry about using either, it's an advantage you are able to drive 2ohm speakers, but a vast majority i've seen are 4ohm anyway

daz · 25 Sep 2006 at 13:58

Dr.EM said:
When an amp has a rating like this, the lowest load it can power is 2ohms. Smaller loads take more power, so using a 2ohm load over a 4ohm produces twice the power (bear in mind that only sounds 10% louder though).

That's not true, an amp designed for a 2 ohm load will product twice the power. If not designed for a 2 ohm load, you'll get efficiency losses.

Dr.EM said:
Also, 2ohm is low in any terms and you'll have to make sure the cabling is thick and the connections are good to avoid loosing too much power.

Thicker guage cabling is only required for extreme amounts of power, usually reserved for car subwoofers taking 500W RMS+. The gauge of cabling required is unrelated to the impedance of the speakers you want to power.

Dr.EM · 25 Sep 2006 at 15:06

daz said:
That's not true, an amp designed for a 2 ohm load will product twice the power. If not designed for a 2 ohm load, you'll get efficiency losses.

I didn't dispute that it produces twice the power, however I pointed out that twice the power in any circumstance does not equal twice the volume to our ears. Since our ears are logarithmic, a power increase of tenfold will sound twice as loud

daz said:
Thicker guage cabling is only required for extreme amounts of power, usually reserved for car subwoofers taking 500W RMS+. The gauge of cabling required is unrelated to the impedance of the speakers you want to power.

In a car system, I would say it is relevant to the impedance. Since the voltage will always be 12v (bar said subwoofer systems), the only parameter that will affect the power is the impedance of the speaker (ignoring bridging circuits). The lower it is, the more current and thus power it will take from the 12v source and as such, more power could be dissapated as resistive losses in the cabling. Your probably right about the amount of power involved making this somewhat of a non-issue though. I expect the pre installed cable is adequate

daz · 25 Sep 2006 at 18:37

Dr.EM said:
I didn't dispute that it produces twice the power, however I pointed out that twice the power in any circumstance does not equal twice the volume to our ears. Since our ears are logarithmic, a power increase of tenfold will sound twice as loud

Nicely clarified!

I expect the pre installed cable is adequate

Pretty much the case. It's best to go for a low AWG gauge cabling if you're running an incredibly high powered install (some people use 0 guage when running 1k W RMS

... think cabling the thickness of a finger or a thumb!) Otherwise in most amplifier wiring packs you'll get the correct guage wiring for your average system.

james.miller · 27 Sep 2006 at 01:06

and just to note its not always twice the power even if it is designed to power 2ohm loads. Thats a best case and you rarely see that with any amplifier. 8 to 4 ohms yes, but not often when moving from 4 to 2 ohms.

daz · 27 Sep 2006 at 12:08

james.miller said:
and just to note its not always twice the power even if it is designed to power 2ohm loads. Thats a best case and you rarely see that with any amplifier. 8 to 4 ohms yes, but not often when moving from 4 to 2 ohms.

Class D amps designed for subwoofers, many of which are capable of handling loads down to 0.5 Ohms will get 95-99% close.