I have a pair of LS50s.
What are the forum thoughts on a pair of new passive LS50’s for $799?
I have a pair of Q150’s I am very happy with in another room that I paid $350 for..
If you look at the post above yours, I talk some about my experience with them.
I paid $800 shipped for mine a few years ago on sale. It is a great price; it is actually the typical refurbished price.
Mine are powered by a Cambridge CXA60, which is rated for 60W RMS at 8 Ohms and 90W RMS at 4 Ohms. (It once measured significantly stronger at ~75 / 105W, but I can't seem to find that article again.) I find it to be plenty for a room my size and at my listening distance. I rarely set the volume control higher than 9:00 and listen at an average of ~75dB, with peaks on dynamic music occasionally reaching the 85dB range.
I also have a Peachtree Nova 150 (150 / 250W) that I have used with them, but I do not hear any benefit to the extra power in that room. (I need to send that Nova 150 to Amir for measurements, since none of the new Peachtree stuff has been reviewed here.)
I do not have Q150s, but I do have Q100s in my living room. The LS50s are very different speakers in terms of frequency response and quality of construction.
LS50s are leaner in the bass octaves and have more of a BBC curve overall. You can easily see this in the measurements on page 1. This can actually work to your advantage in some rooms like mine. In other rooms, it is easily overcome by careful integration with 1 or more subs.
LS50s have much better built cabinets and do not exhibit much in the way of cabinet resonances, which has been a "problem" with Q Series speakers.
LS50s do not have any audible port noise, whereas Q100s (front ported) do: midrange leakage at all levels, chuffing at high levels.
Both speakers have excellent dispersion and are very forgiving with seating position relative to the tweeter.
In summary, the LS50 is a much better built speaker that is tuned differently. That tuning works well in some applications and less well in other applications. And, they do require a decent amount of power to sound their best.