Axiom Home Page Forums General Discussion Technical Questions M60 impedance when bi-amping

Hi guys,

I was wondering, the M60 is a nominally 8 ohm speaker. I'm assuming this is measures with the jumper on between the Mid+tweeter and the woofer terminal. Since the jumper effectively connects the two in parallel, does that mean each of the mid+tweeter and woofer terminals are 16 ohms?

That would present a 16 ohm load to the power amp if one is biamping each speaker with 2 channels.

Similarly, that would make the M80 8 ohms for each of the terminals?

Would appreciate if some light can be shed on this.

From what I have read, the impedance doesn't change when bi-amping. I'm not sure why, but I'll wager it has to do with the crossovers.

Long time no see, slack; welcome back. As Ken pointed out, no, the impedance doesn't change(appreciably), and yes, it's because of the action of the crossover. An "8ohm" speaker with two sections being connected in parallel through the crossover doesn't consist of a 16 ohm high frequency section and a 16 ohm low frequency section, resulting in an 8 ohm speaker because of the parallel operation. Each section is 8 ohms(nominally)and when one of the sections is presented with material out of its operating range(e.g., a 100Hz signal to the tweeter)the resistance in the high frequency section of the crossover feeding the tweeter is greatly increased so that, for example, the overall resistance to the tweeter at that frequency might be 160 ohms rather than its inherent 8 ohms. So, the combined woofer/tweeter impedance at 100 Hz would be the reciprocal of the sum of the reciprocals of the two sections, i.e., 1/8 + 1/160=21/160; 160/21 would be the effective net impedance of about 7.6 ohms. The fact that the resistance in the crossover causes the effective resistance of the driver in question to be much higher than its nominal value when the signal is out of its designed operating range results in the impedance changing relatively little, instead of being cut in half(e.g., 1/8+1/8=2/8; 8/2=4ohms)by the parallel operation.

nice explanation!

Hi JohnK,

Glad to see everyone still as active and helpful as ever on the forum. I've recently noticed that Axiom now offers free shipping to Singapore where i stay, and hence the renewed interest, : ).

Truly great explanation, now it makes sense.

Just came back from the local HIFI store, heard a pair of B&W 804S. The vocals and midrange are incredibly smooth, highs effortless and razor sharp transients. Wonder if anyone has had the opportunity to audition the M60 or M80 in comparison with the 804S.

I guess i should post this in another part of the forum...

Cheers!

There are many posts on this forum regarding the m60's being comparible to the 703's, not sure about the 804's. Pricewise there is no comparison.