I have noticed in several speaker reviews recently the impedance of some commerical speakers dropping below 3 ohms for a limited region. And, it appears that these speakers weren't really causing any problems, or at least not enough that the manufacturer was concerned about it.

So, I decided to experiment a little, Below is the impedance of a vented speaker that uses three identical woofers wired in parallel. These are crossing over to a single midrange at about 350Hz using first order slopes in the crossover region. The plot is for woofers and midrange only with their crossovers (the tweeter is not connected here).

With crossover elements in place, the impedance runs about 2.9 ohms for a DC resistance and has a minimum impedance of 2.41 Ohms at 180 Hz. However, as is the case with paralleled drivers, the phase angle is very mild in this range and typically runs in single digits whenever the impedance is below 3 ohms.

So, my question is - Do you think this is still a fairly benign load since the lower impedance is limited in bandwidth (the region with the mid and tweeter will probably run above 8 ohms), or do you fell that 2.4 ohms minimum is pushing it, even with the low phase angle?

Give me your thoughts.

So, I decided to experiment a little, Below is the impedance of a vented speaker that uses three identical woofers wired in parallel. These are crossing over to a single midrange at about 350Hz using first order slopes in the crossover region. The plot is for woofers and midrange only with their crossovers (the tweeter is not connected here).

With crossover elements in place, the impedance runs about 2.9 ohms for a DC resistance and has a minimum impedance of 2.41 Ohms at 180 Hz. However, as is the case with paralleled drivers, the phase angle is very mild in this range and typically runs in single digits whenever the impedance is below 3 ohms.

So, my question is - Do you think this is still a fairly benign load since the lower impedance is limited in bandwidth (the region with the mid and tweeter will probably run above 8 ohms), or do you fell that 2.4 ohms minimum is pushing it, even with the low phase angle?

Give me your thoughts.

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