Does impedance of a speaker change when one bi-amps?

@steve59 

WOW, you guys complicated that conversation.

My Integrated amp rated at 250/8-425/4 shut down driving my power hungry speakers that have 2 pair of binding posts on back they’re 4 way 6 ohm rated and manufacturer recommends 500 watts. My question for the experts assuming I can get the amps output levels matched is, Would my integrated be less likely to overheat at the same spl if I added a 2nd amp, removing the strap to horizontally bi amp the speakers? also if I got output levels matched would amps of identical power be necessary or could I wire a pair of 350 mono's to the bass of each speaker and use the int to drive the top end?

Sometimes getting technical gets to the answer far better than a stack of nontechnical thought.

 When I tried to run my  ESLs off a high quality integrated I learned a lot. For instance the rated power is only deliverable into a resistive load. Anything reactive shut the amp down and a message came up  "check for shorted speaker wires"  That speaks volumes. The amp thinks anything below X ohms is a short. 

After reading the manual carefully I found that we could selectd 4 or 8 ohms but that did not affect the output power at all, only where the protection cut in. Selecting 4 was worse than 8 and shut downn sooner. This is not the behavior of a good solid amplifier.

Integrateds are not rough and ready power amps in general. 250/425 watts is power amp land and I mean big power amp land. How much does your amp weigh? Would you care to tell us its model? 
Sounds like a simple case of amplifier does not like speaker. A second amp will help indeed. Let the current integrated take the lighter load. 

Have you found an impedace curve for the speaker. Usually you can just google its name + impedance curve using images.

@byfwyne

So the bottom line is that there seems to be something to be said for light loading.

It was rather obvious to me from the start. The tubes love it.

Does anyone have any questions about why it works so well? The distortion reduction is usually 5 to 1 or more and the damping (regulation) doubles. Noise goes down 3 dB. All you give up is imaginary headroom.

When I tried to run my ESLs off a high quality integrated I learned a lot. For instance the rated power is only deliverable into a resistive load. Anything reactive shut the amp down and a message came up "check for shorted speaker wires" That speaks volumes. The amp thinks anything below X ohms is a short.

Yep. ESL's are basically giant capacitors. 1/3 of an ohm at the top of the spectrum is not unheard of. Fortunately there's very little music power at 20kHz, but it is not an easy load in general.

Thanks for the interest. My Int is A Hegel H360 and the speakers are Revel salon2's. Though I chose the unit to go with the salon1's I had at the time i'm happy with the synergy with the new speakers and now i've had the Hegel just over a year and the new speakers since march I did manage to trip the thermal protection once. I know heat kills and I horizontally bi-amped my R105/3's successfully in the past. The 2nd amp made a big difference with the kef r105/3 speakers really filling out the bottom end. 

The current .7 series Maggies have series crossovers, and are therefore not candidates for bi-amping. The .6 and earlier have parallel crossovers, and can be bi-amped. An electronic x/o is used in place of the external one supplied by Magnepan with the 3.6, and the speaker benefits greatly from bi-amping. Not just for the benefits mentioned above (eliminating the possibility of amplifier IM distortion, etc.), but because instead of one, brute-force amp on all the speaker’s drivers (Maggies need lots of current), two smaller, perhaps better-sounding amps can be used. A ss on the bass panels, a tube on the mid/tweeter is a favorite combination, one I myself employ with my Tympani T-IVa’s. Some long-term Maggie user/owners have therefore chosen to stay with the older models (the .6 is a favorite), primarily to be able to bi-amp.