Audio 0hm Knowledge

[Shamonee]

I have a 4 Ohm amp which need to drive 4 2ohm speakers.

Does anyone know how I should wire this?

Do i wire them in series?

Thanks

[lagerland]

Many of the amplifiers on the market today are touting excellent performance with 2 ohm load impedances. Some also state that "continuous operation" with 2 ohm loads is possible. While such statements are probably true, it is not really a good idea to run under such conditions!

First, a word on speakers is in order (for much more detail see my article on speakers). All speakers have a characteristic known as impedance (measured in ohms), with most speakers being either 8 ohms or 4 ohms. Lower impedances represent more difficult loads for amplifiers to drive. Two 8 ohm speakers connected in parallel will result in a 4 ohm load at the amplifier. And, two 4 ohm speakers (wired in parallel) result in a 2 ohm load. In actuality, speaker impedance can vary by a factor of 10 or more over the audio frequency range. When a speaker is said to be 8 ohms, it is understood that this is a nominal or approximate rating (the same goes for 4 ohm speakers). An 8 ohm speaker could have an impedance as low as 2 or 3 ohms and as high as 50 ohms (impedance is frequency dependent)!


Further, a speaker load is not the same as a resistive load, speakers are reactive loads. A reactive load is a load that has inductive or capacitive properties. Depending upon the input signal frequency, speaker loads may be resistive or resistive with an inductive or capacitive component. Without going into a ton of technical explanation, what this means is that speakers are often difficult loads for amplifiers to drive. Driving difficult speaker loads is where better amplifiers are separated from lesser designs.

Even though an amplifier may be rated for continuous use at 2ohms, there are several reasons why this is not the best thing to do:

Paralleled speaker loads may be lower than you think: No speakers that DJ's are likely to use have 2ohm ratings. However, a pair of 4 ohm speakers paralleled will yield a nominal 2 ohm rating. As stated before, the actual impedance varies and the minimum impedance may dip considerably below 2 ohms at certain frequencies. Lower impedance loads mean more losses and more heat dissipation in the amplifier (see next item).

Heat Considerations: Operating an amplifier with a low impedance load increases the heat dissipation of the amplifier (try it if you don't believe it!). This is because low impedance loads require more current, which taxes the amplifier***8217;s power supply more severely. More current means more losses (which translates to more heat). Excessive heat is unhealthy for electronic devices and should be avoided.

Increased Line Losses: As the speaker impedance is lowered, more of the audio signal is lost (in the form of heat) in the speaker cables! This can become significant if you run long cables. Speaker wires have resistance (the value depends on the thickness and length of the cable); if the speaker impedance becomes very low the resistance of the speaker wire may no longer be insignificant. To prevent this problem, the cross sectional area of the speaker cable conductor must double for each halving of speaker load impedance! In other words, running 2 ohm loads means using VERY heavy speaker cables.

Damping Factor degradation: Using super low impedance loads on an amplifier will degrade the system's damping factor (discussed in detail below). Degradation of damping factor means that the amplifier will have less "control" over the speaker system, possibly resulting in "boomy" bass response.

So, just because an amplifier has a super powerful 2 ohm rating, don't look for ways to wire up multiple speakers in order to "use" this power! Treat the 2 ohm rating as "headroom" and know that your amp has the ability to more easily handle the most difficult "normal" speaker loads that you are likely to ever encounter. If you need more power, get a second amp. Two medium powered amps are better than one monster (what if your one big amp dies? With two smaller amps at least you can still run!).




Check this link..................

http://www.talkaudio.co.uk/ipb/index...-ohm-speakers/

And this one...............

http://en.wikipedia.org/wiki/Ohm's_law

[blankichu98]

sorry, I dont know...

[R_J]

speakers in series. 2 ohm in series with 2 ohm = 4 ohm
speakers in parallel, 2 ohm in parallel with 2 ohm = 1 ohm
connect positive of one speaker to negitive of the other.