846a Impedance Curve

[Paully]

Does anyone have or no where I can see the impedance curve for the Model 846a? I know the horn are nominally 16 ohm, no idea about the woofers. Changing the taps on my amps isn't tough but it isn't easy either. I would just like to see what the swings are and how low it goes so I can know whether I should hook up 4, 8, or 16. Would like to avoid having to solder and unsolder the wires multiple times if I can. Thanks!

Paul

[SMKSoundPro]

The 864A Valencia uses a 416z 16 ohm woofer with a n800f crossover.

Scott.

[Paully]

So we have both the woofer and the horn at 16 ohm. But I assume that is nominal. Do we know how far down either dip? Or an impedance curve for the speaker itself would be great if anyone has one. Probably not, but it can't hurt to ask. Thanks!

[HastyCroke]

Hi....Ported enclosure has two impedance peaks and a dip between. That dip is both the resonant frequency of the woofer (minimum movement) AND the port (maximum output) - it is the tuning/resonant frequency of the ported box. Optimal resonant frequency depends on Thiele-Small parameters and the size of the box and the tube. For maximum efficiency choose more port area.

[grumpy]

So, 1) that question was 10 years ago. :D
2) The minimum impedance between peaks (as noted) for the woofer would likely be close to Re.
Unlikely that there would be issues further up in frequency that would require a change in tube amp tap for this kind of design.