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

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.

For the record, almost all passive crossovers also include some form of EQ. If you plan to remove and replace a passive crossover you need to be prepared to do both.

A local speaker builder brought over a pair of his speakers without crossover for me to play with bi amping. The drivers are a $225 Scanspeak woofer and $60 Tweeter. $225 woofers only show up in $10,000 speakers. Most of the price of a complete speaker is in the cabinet and margin for the dealer. When an interested party took at a $10,000 speaker, priced out the components and found the drivers plus crossover to be about $1,000 or less. Its just the economics of the speaker business.

The drivers my local guy had chosen had such flat response that no EQ is needed nor does he build any into his series crossover. The impedance was amazingly constant and he feels this is the main virtue of his speaker. If a speaker has a flat impedance curve then damping is not so big an issue. Good drivers have pretty flat response, that is what you are paying for. 

I have never found a need to add EQ to a bi-amp system if the drivers are good quaity. Besides, in a bi-amp system you already have a woofer and tweeter control (you need only one) to adjust the tonal balance which I do at my own pleasure. The knob is right next to the volume control which I also adjust for my own pleasure. Its all so simple, but so hard to get across. I have to climb the wall of marketing just to get someone's ear. 

@shkong78 

Yes, turn them off when not listening. The cap died due to continued high temperature. Electrolytic caps do that.

There are companies offering DIY loudpseaker kits, the drivers and speaker-level passive x/o parts, along with required enclosure (or OB baffle) specs, provided. You make the enclosure (or buy one with the specified internal volume; Parts Express sells good ones) or OB baffle, and install the drivers and x/o. One such is Danny Richie at GR Research, located in Texas. He is a renown x/o designer, doing work for other speaker makers. Very high performance-to-cost-ratio speakers. Danny specializes in high-sensitivity designs (and is a fan of OB's) for use with low-power tube amps. Details on the GR Research website.

@steve59 

I found a review at Sound Stage mag. Looks like a nice amp. This is interesting, from the review   https://www.soundstagehifi.com/index.php/equipment-reviews/934-hegel-music-systems-h360-dac-integrat...

  Like its predecessor, the H360 boasts a whopping 250Wpc into 8 ohms, or 420Wpc into 4 ohms. Its damping factor is over 4000 -- four times that of the H300. It should have no difficulty driving just about any pair of speakers it’s hooked up to.

I see he is impressed with daming factors that are very large and 4 times larger is, 4 times better?. We know 1000 or 4000 makes no difference. 

If you trip the thermal something has to be done. Can you now put your hand on the heatsinks after extended playing? If not you are still too hot.