Especially when you consider that listening volumes are a much larger factor. Fudging specs aside, even a speaker that is unquestionable 8 ohms would not draw that much less power than our Verus II Grand Bookshelf. Here at Aperion, we like to be honest and not overstate specs, but of course the same can’t be said for every speaker manufacturer out there. I have no doubt that there are in fact speakers out there that are labeled as “8 ohms” that have impedance graphs with dips the same or more severe as our curve. The thing is, there really aren’t any hard and fast rules when it comes to nominal impedance. Which is more important, a speaker that we feel delivers the signature Aperion sound that our customers know and love, or a speaker that is slightly easier to drive? Of course we chose sound as the most crucial attribute for our speakers. So going back to the original question, why did we make a 6 ohm speaker when we could have just designed an 8 ohm speaker and had it draw less power? The honest truth is that we would have had to make sacrifices in terms of sound in order to get the impedance higher. For further reading, you can check out more technical details behind speaker impedance here. That is, the speaker’s impedance will not be below 6 ohms for the vast majority of the time. Because of that, we can say the speaker has a “ nominal” impedance of 6 ohms. For the rest of the frequency response, the impedance is well above 6 ohms. So when we say that the speaker’s impedance is “6 ohms”, what do we mean? Well if you look closely, you can see that the impedance only dips below 6 ohms ever so briefly around 200 Hz. Looking at the graph one thing should be clear, there’s a wide range of impedance values across the speaker’s frequency response, which is true for nearly all speakers. Then on the right hand side of the graph you can see a gradual rise as the frequencies get higher due to inductance. There are three big impedance peaks in the graph, which correspond to the resonance frequencies of the port, woofer and tweeter moving left to right. To illustrate this, take a look at the impedance graph of our Verus II Grand Bookshelf. The other reason for impedance variance is an increase in inductance of the voice coil at higher frequencies which also causes the impedance to go up. At that frequency the free movement of the driver generates what is known as “back electromotive force” which opposes the flow of current and creates a large spike in impedance. First, every driver has a resonance frequency at which it moves freely once it is tapped or otherwise engaged. There are a few reasons for this, but there are two main factors. The reality is that a speaker’s impedance will actually vary quite widely depending on which frequencies it is producing. Speaker Impedance is Really Just an Average To answer that question we need to dig a little deeper into what it really means when we label a speaker as “4 ohm” or “8 ohm”. Since a 4 ohm speaker takes more power than an 8 ohm speaker, you may be wondering why anyone would design a 4 ohm speaker. Because of that, a 4 ohm speaker is considered more “power hungry” and will tax your amp more than a 6 or 8 ohm speaker. Since impedance is a measure of how much the speaker resists current, the lower the impedance in ohms, the more power the speaker will draw from your receiver. If you’re shopping around for speakers and take a look at the specs, you’ll notice that most speakers are rated between 4 and 8 ohms. Now speakers on the other hand, do in fact have measurable impedance because of the crossover network and the impedance of the drivers themselves. So when people ask “how do I match the impedance of my receiver to my speakers”, they aren’t really asking the right question. There isn’t sufficient circuitry or components between where the power is being amplified inside your receiver to the speaker outputs for any significant impedance to build up. The truth is, since your receiver is the source of power in your system, its impedance is negligible. The biggest of which is that your receiver’s impedance is something that you need to keep in mind when you are buying speakers. All pretty simple, right? Well, there’s still many misconceptions around the topic of impedance when it comes to speakers. The unit of measurement of impedance is ohms, often symbolized by the Greek letter omega: Ω. Impedance, it’s a fairly straight forward concept, all electrical circuits and components resist the flow of electricity (or current) to some degree and the way we measure that resistance is impedance.
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