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Impedance question: Met subs, monitors, ribbon tweeters

T

Tom Fred

New Member
Hi all:

I'm having trouble figuring the correct impedance matching for my setup:

• A Pyramid/Sequerra 8w subwoofer (2 or 4 ohms, depending on strapping), Met 7 (4-8 ohms), and T-1 ribbon tweeter (12 ohms) for each channel

• Each channel driven by a McIntosh MC2100 in mono/bridged mode (which offers me a choice of 2, 4, or 8 ohms)

Wiring goes: MC2100 > 8W sub (with crossover) > Met 7 + T-1

The fifth-generation samizdat literature I have on the speakers is not terribly helpful on this point. Do I calculate all three speakers independently (which comes to either 1.4 or 2.2 ohms, depending on how I strap them) and go with the 2 ohm option on the MC2100? Or does the fact that the 8w is/has an interconnect and crossover change that calculation somehow?

Anything else I should be aware of in wiring up this combination of speakers?

FWIW I have been running this setup at 4 ohms for years without blowing up either the amp or the speakers, but I figure it's never too late to learn the proper/preferred way to do things.

Thanks!
 
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The 4 Ω connection is probably correct - the crossover in the subwoofer should prevent the total impedance from going lower than that, assuming you keep the strapping at 4Ω. It's possible that you'll go slightly below 4 Ω in the frequencies where the ribbon and satellites overlap, but I wouldn't worry about it.
 
Impedance is frequency dependent. Nominal impedance is a made-up number that could be the minimum impedance over the frequency range, the average impedance, or whatever the manufacturer wants to use.

To determine the impedance seen by an amplifier, combine the impedance of individual speakers only over their common frequency range. For full range speakers it is easy. But your 3 speakers operate over different ranges. For example, your subwoofer impedance is independent of your tweeter impedance because the frequency range of each do not overlap, therefore the two values do not need to be combined when figuring amp load.
 
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