According to this review of the QLX series you're right Fro. Sonically, the two products are the same with their "Quadrature" something or other tech. The real differentiator to me between the two products is the RF capabilities. They both play in the same frequency spectrum, but the ULXD series does a lot more with it, splitting the spectrum into some 2500 different channels vs. something like 60 on the QLXD. Plus you can have higher power transmitter packs, which will instantly help combat RF interference.
So, even if you don't need to have 100 wireless channels, the more robust RF agility of the ULXD may be worth the extra cost if "Failure is not an option".
From review:
So, even if you don't need to have 100 wireless channels, the more robust RF agility of the ULXD may be worth the extra cost if "Failure is not an option".
From review:
As I alluded to earlier, QLX-D shares much with the pricier ULX-D — same digital transmission, and anecdotally, the same sound quality — but ULX-D brings pro features such as Dante, dual/quad-channel receivers, and the option of a stronger 20W transmitter power. There’s also Shure’s ULX-Pro analogue system, with QLX-D almost certainly taking much of its market share — only the die-hard ‘analogue or nothing’ wireless stalwarts will insist on ULX-Pro.
Meanwhile, if you’ve got more than a handful of wireless channels and you find yourself spending, say, 30 minutes before every gig configuring the system and checking/replacing batteries, you deserve to upgrade to a system like QLX-D. Anything cheaper is false economy. Anything more expensive, could well be unnecessary for all but those ‘failure is not an option’ applications I mentioned earlier.