What is Speaker Impedance and Amplifier Rating

What is Speaker Impedance and Amplifier Rating

It's quite easy to get confused these days by all the specifications which are provided by manufactures on their Loud Speakers and Amplifiers. One of the important pieces of information you should be paying attention to is "Impedance". This will usually be provided by most reputable Speaker Manufactures and is also mentioned in the Specifications of most Amplifiers.

But we commonly get asked I need an Amplifier which will output a 4 ohm signal. What if we told you there was actually no such thing? Confused.. Well let me explain in more detail what impedance is and how it applies to both Loud Speakers and Amplifiers.

What is Impedance?

Impedance is an electrical measurement for a loudspeaker's internal resistance. This is the opposition to the flow of electrical current through the speaker drivers and voice coils from your Amplifier. This can be simplified to think of it as an electrical "friction" which resists the flow of the signal through your speakers. Impedance is measured in Ohms. The lower the Impedance the more resistance there is in the circuit, thus making the Amplifier need to work harder to power these kind of Speakers.

Speakers commonly come in 8, 6 and 4 Ohm nominal loads. The term nominal is used as the Impedance will actually vary depending on the frequencies being played at that particular time and the average reading will be close to those given values.

What Impedance Is The Best?

Well Impedance does not directly influence sound quality so should not be used as the only deciding factor when purchasing some new Speakers. Though you will find alot of the higher end Speakers will have a lower Impedance rating.

With Amplifiers it will depend on what you are intending to use them for. As of course better quality models are designed to work with lower Impedance and have better current handling transistors and will allow for better heat dispersion.

But if you are only looking for a small compact little system to power a single pair of 8 ohm speakers it would then be overkill to purchase a large 4 ohm stable Amplifier, as you will not see the full range of benefits to using one and it's really not what they are designed for.

Amplifiers and Impedance

Earlier I mentioned that there was no such thing as an Amplifier which would output a 4 ohm signal, you should know now that Impedance is the force which apposes the signal and not the signal itself. Lower Impedance's will make your amplifier need to use more current to "push" the signal through your speaker wires and into your speakers.

The problem is with more current you get more heat which is the nemesis of all electrical components. So if an amplifier is not designed to power a 4 Ohm speaker it will overheat and cause the amplifier to shut down at best and be damaged at worst. Decent quality amplifiers will be designed to run at these Impedance by the use of higher current transistors and large heat-sinks to help dissipate the heat which is generate by the higher currents.

Key Take Away Points

When purchasing some new Speakers and/or Amplifiers you:

  • Need to look at the nominal Impedance is of the Speakers.
  • Know that Impedance does not affect sound quality on its own.
  • Check if your Amplifier is designed to run at these levels of Impedance without over heating.