After keeping the amazing Line 6 wireless demo about 3 months longer than I'd promised, I've finally had the time to use and measure it and - amazingly - finally send it back to Craig who's been way too gracious to me.Conclusion
You'd be a fool not to check this system out if you're looking for wireless anywhere near its price range. This type of wireless system or something similar to it is the future. Occupy one frequency region that already has approval for use over most of the civilized world due to wifi while using data headers to differentiate between audio streams seems like the "duh" moment of what to do about diminishing white spaces. Still, this digital thing is in its infancy and not without hiccups, but if you place the receiver carefully it's quite reliable. The older school stuff seems more robust in avoiding dropouts in my experience, but it doesn't sound as good and costs more, a lot more if you're into quality.
My favorite features are (1) sound quality, (2) build quality - not Lectrosonics or the high end Shure, Sennheiser, etc., but a real step up from most of the stuff out there, (3) Shure capsule compatibility on the handheld and Shure standard TA4F connector on the beltpack, and (4) cost.Measurements and Comments
The (3) wireless systems I have access to are compared to the Line 6 XD-V70, we'll go from worst to best from a sound and measurement perspective. The XD-V70 is covered last. :) In each case I took the easy way out and made measurements on the beltpacks since they have wired inputs. It is assumed that the transmitter technology employed in the handhelds is the same.Shure ULX-Pro
This has been a tried and true piece in my rental inventory for 6 years or so. Beat, dropped and repaired once by Shure's marvelous service dept. I trust it to work and it seems quieter in use than the better sounding UHF-R, probably due to the old school companding and high input level compression that the UHF-R seems to make much less use of in the first case and eliminates in the second. Looking forward to corrections on my guesses, but the measurements point in this direction.
In each case when measuring at various input levels, I started with -50dBu and increased levels in 10dB steps through 0dBu (.775v) if the unit could handle that much level before clipping. If the unit could handle more than 0dBu, I added one more trace at the higher level. In the case of the ULX-Pro, you'll notice that Shure has a compressor that not only lowers the output up to 4dB, but reduces its bandwidth while doing so. The lower traces are the higher input levels with the increasing compression. You never notice this in use because folks are screaming at these levels and it's usually ugly anyway. Not a very flat spectrum, but fine for rock 'n roll and general use.
Now you'll note what I've come to understand as a tell-tale sign of classic wireless companding - that is you can't measure the thing with a swept sine (black trace). This type of system is reasonably expecting a fairly broadband signal and if you use a slow sine sweep (or worse, one frequency at a time via a stepped sine measurement), you'll find out in a hurry that you should NOT use such systems with percussive instruments with a lot of LF energy. Then again, you can get a who-knows-what-it's-gonna-sound-like LF expander effect with these things on a drum kit if you want. :) Ever used a ULX-Pro beltpack on a picked acoustic guitar and been amazed at the "dynamics"? Now you know why. Finally, distortion measurements are only practical on systems that can tolerate swept (or even better - stepped) sine stimuli.Shure UHF-R
This has been a tried and true piece in my rental inventory for 4 years or so. Also treated roughly at times, but not nearly so much given the upper scale rentals. It has proved trustworthy after an initial spate of blanking transmitter LED screens that were fixed under warranty. These things sound much better than the ULX-Pro, are built much nicer and priced accordingly.
This unit does much better with swept sines, but still has some companding going on thus still has a preference for pink noise measurements. Compression at higher input levels is eliminated - what you put in is what you get out - yea.
Swept sine vs pink noise. Yes, Ethel, you can use this on percussive instruments without much issue.
Now that we have a unit that can tolerate sine waves, we can have a look at distortion at the highest input levels. The following uses a fairly long stepped sine stimulus.
And now the main reason I dropped over 2 grand on the CLIO measurement system, a very short term gated stepped measurement - only 6.5ms down to 300Hz or so where the wavelengths get long enough that you have to open the "meter on time" enough to get at least a couple of sine periods in to make a reliable distortion measurement. These very short term sine bursts allow peak measurements of loudspeakers and amps without melting things. In the case of wireless measurements, it'll reveal which systems can pretend to be hardwired and which cannot - not that you'll ever find any real music with 6.5ms events. You _might_ find high Q issues with loudspeakers that would have been missed with a log sweep or noise based stimulus.Lectrosonics TM400
Ever driven or just closed the door on a Mercedes Benz and thought how different really well made stuff is? That's what my Lectrosonics TM400 wireless measurement system feels like. It also works extremely well plugged into a Neumann KMS105, which like most Neumann capacitor mics, is no piece of cake to power correctly.
Very little or no compression going on. No need for pink noise measurements with this unit.
Stepped sine distortion measurement.
Interestingly, some of the very short 6.5ms sine bursts poked their heads out of the magnitude trace as you can see here in black. Again, 6.5ms ain't nature, but the XD-V70 can handle it and does an amazing impression of a mic cable as you'll soon see.Line 6 XD-V70
This unit amazes, but has to be used with a bit more care to get dropout-free and clean HF performance. On the first issue, you need to keep the receiver on stage near the transmitter in my experience. On the second issue, I found by accident that of the (12) "frequencies" the unit said were available, channels 2 and 12 showed a fair amount of HF noise in the measurement traces that I initially thought was an issue with my test setup. I have no idea at this point if it's audible. Changing channels to anything but 2 or 12 fixed it. My Apple router was about 10' away and happens to use channel 2 in its transmission, but I have no idea if this has anything to do with it or not - this is new territory for me. I should have turned the router off to find out, but only thought of this just now. :)
There are (3) "environment" modes you can choose with this unit; OFF, NORM, and TALK. With OFF, it acts like a wire and neither companding or compression happen. With NORM, companding and compression don't happen, but expansion with increasing LF extension happen with increasing levels. Must be an attempt at gating noise at low levels. You can also yell and you get the voice of God effect. TALK mode is more of the same. You'll notice that the expansion circuit doesn't like swept sine measurements - again reasonable given the broadband signal expected. Personally, OFF is "norm" for me. :)
Environment OFF swept sine. Wireless bass and guitar users need not apply elsewhere.
Environment OFF gated stepped sine.
Environment NORM and TALK swept sine (expander not happy).
Environment NORM pink noise at various input levels.
Environment TALK pink noise at various input levels.
We sure torture ourselves in the quest to replace a $25 mic cable.