Speaker mash up ?

Is it possible to use two different speakers at once. Could i use Magnepan 1.6 for the highs and proacs for the lows ? I was thinking of running biwire cables . Highs to the magnepans high inputs and the lows to the proacs low inputs. I do not have the maggies yet to test ,but plan on getting a pair. Just curious if anyone has thought about this or even tried it .
Oh Boy!
You would be best off using the full Magnepan speaker, and adding some sort of other speaker as a 'cheap' subwoofer (really a low midrange, upper bass boost)
But yeah, not that it is great, but certainly some folks would enjoy it.
A few posts of folks using multiple sets of loudspeakers and loving it.
We each have our own wants.
Purists would complain, but who actually cares?
My experience is that instead of accentuating the virtues of each you bring forward the bad side of both. The way you propose to do it will be very bad if I understand it properly as the crossover point will be god knows where and how will you achieve the right sound balance between the speakers. Are you using an electronic crossover with level controls? Can you do it? Sure. Should you do it? I wouldn't do it but it is your money.
I had a bud who ran a pair of pre outs to two different amps hooked up to two different pairs of speakers and all playing at the same time. All mid-fi mass produced stuff. I'll tell you what- there was nothing missing! Okay so it could definitely sound congested and confusing sometimes but his music collection and knowledge far outshone any deficiencies in his system.
Stan makes some excellent points, and for the reasons he states the results in this particular case (as well as many and probably most other cases using a similar approach) would be a sonic mess, IMO.

I see in one of your other threads that your ProAc speakers are the Response 2.5s, which have their crossover point at around 3 kHz, per Stereophile's review. The Maggie 1.6/QRs have their crossover point at around 600 Hz.

So by using the internal crossover networks of the two speakers, as you have proposed, the result would be that both speakers would be simultaneously reproducing frequencies from significantly less than 600 Hz to significantly more than 3 kHz, meaning essentially all of the mid-range, and more. You would therefore have mid-range frequencies arriving at your ears from multiple directions and distances, and therefore with different arrival times, resulting in comb filter effects. You would also have a level imbalance between those frequencies and treble and bass frequencies. There would also probably be a level imbalance between the treble and the bass, due to differences in the sensitivities of the two speakers. There would also most likely be issues related to the crossover slopes, and issues resulting from differences in the intrinsic sonic character of the two speakers.

Not a good idea, IMO.

-- Al