Kef Reference 1 Meta Impedance Puzzle

It’s a 2 Ohm speaker with no good reason.  

It's not a 2 ohm loudspeaker. KEF lists it at 4 ohms. Many loudspeakers dip down to 2 ohms, not that unusual. The phase angle is pretty manageable in the low impedance region. It happens. 

Hey Russ, Take a look at the grey line. That’s the equivalent impedance given the phase angle. The current requirements of this amp are equivalent to about two Ohms from 1kHz on down. The high current and breadth of frequency is pretty breathtaking, and in my opinion, which is informed, hard to drive.

Also note the phase angle being negative. It’s highly capacitive in this range, when most speakers would be be a little inductive as the woofer impedance should dominate the bottom octaves..

These two items, plus missing two impedance humps make this a very unusual 3 way. In fact I’d say we are missing 2 humps, a mid/tweeter crossover hump and the port hump. After looking at maybe hundreds of speaker charts in Stereophlile over time and my own simulations and builds I would judge this as very unusual.

Based on that chart and the experience of audiogoners, the 4 Ohm rating is a deceptive guide for buyers.

My best guess right now is that there’s a poorly designed or implemented impedance compensation circuit in there.

I think KEF deliberately made the woofer that way to get as much bass out of the speaker as possible.  I own the non-meta Reference 1 speakers, and the bass is shockingly good when using an amplifier capable of delivering a lot of current.  With a less capable amp, the bass output is very unremarkable.

Hey @80s_forever - Indeed, high current = high output.... but... where are the missing impedance peaks??  And why is the phase angle negataive??

The simple answer, that they used a low impedance, high current woofer just doesn't explain the rest of the impedance data.