Hartke cab with ohmage switch - wtf?

[Steve Browning]

I see that someone is selling a pair of Hartke cabs that have a switch allowing them to be 4 or 8 ohms. How is this done and does this mean any (I am guessing) 8 ohm driver can be converted to 4 ohms (or some other value)?

[ikay]

Some Hartke speakers apparently have a dual voice coil design which allows impedance switching. Here's an extract from a Hartke manual:

"The HyDrive HD112 has an innovative dual voice coil design that allows the cabinet to operate at either 4 or 8 ohms impedance. The cabinet has a impedance selector switch on the rear jack plate. If you are using a single speaker cabinet, and the amplifier has a minimum impedance of 4 ohms, set the HyDrive HD112 impedance selector switch to 4-ohms to get the maximum power from the amp. If you are using two HyDrive HD112 together in parallel, for a total impedance of 4 ohms, or adding a HyDrive HD112 to your current rig, set the impedance selector switch to 8 ohms."

[AdrianP]

As ikay said, it's because some Hartke Hydrive drivers have two voice coils. One at 4 ohms and one at 8. For instance, my HY112 cabs can be run on their own at 4 or, together, at 8 ohms each for a combined load of 4 ohms. Mind you, I have run one cab on its own at 8 ohms and there isn't a massive difference in volume when compared to running it at 4. But it does provide a certain amount of versatility.

By the way, I don't think that all Hartke cabs have dual voice coils, or even all Hydrive cabs. The one in my KB12 combo is definitely 4 ohms only (as confirmed by their tech support line).

Edited June 6, 2018 by AdrianP