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Author Topic: Line 6 XD-V75 for Wireless Measurement  (Read 4571 times)

Langston Holland

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Line 6 XD-V75 for Wireless Measurement
« on: November 16, 2017, 03:17:32 pm »

Hi Everybody:

Things in life have finally calmed down for me and though I never quit playing with my measurement toys, family stuff pretty much kept me too busy to do more than that. Anyway, I needed a wireless measurement system and the lovely Lectrosonics TM400 system isnít workable anymore now that they have chosen for some unknown reason to build a 300Ω load into their plug-on transmitter. Thatís too low for many line level devices to drive, much less a measurement microphone. I noticed a thread in the Audio Measurement and Testing section that asked about using Line 6 wireless for measurement and I think this belongs here instead.

Oddly this sent me to the opposite direction in the market - the super inexpensive Line 6 XD-V75 WiFi system with a beltpack. Though more than twice the cost of this wireless system, the battery powered Earthworks M30BX is an ideal mic to use given its accuracy. A phantom powered mic will need a portable battery supply such as the Countryman AXBPM. It supplies 18V which is fine for the majority of measurement mics.

The XD-V75 has very good build quality for the money. It provides the highest quality wireless transmission Iíve ever come across and does so at a very reasonable 2.9ms latency. WiFi makes it legal everywhere but comes at the expense of low channel count. Battery life is excellent. The beltpack can handle +6.5dBV before clipping with new batteries, +5.4dBV from about 3/4 battery life to empty. Battery, RF strength and scanning as well clipping indicators are accurate and well designed. The manual is unusual - itís well written. This isnít the system Iíd use for mission critical stuff where avoiding interference is life and death or for more than about (8) channels.

Setup

Shureís WQ302 TA4F mini XLR to 1/4" TS phone plug is a great cable to use to interface a self-powered measurement mic to the beltpack. Simply cut off the phone plug and solder on a female XLR. Shield goes to pin 1, center conductors (thereís two of them for some reason) to pin 2, then a jumper between pin 1 and pin 3:

Before:



After:



Measurements

Log swept sine at max undistorted drive level:



Log swept sine level plots from max to max -80dB:



15ms tone bursts, 24 per octave, at max undistorted drive level:



The above plot is a very tough test for a wireless system. This basically simulates the quickest acoustic impulse youíll find in the real world and the XD-V75 continues to behave like a wire. Hereís what a tone burst looks like at 914.2Hz:



These are the selectable EQ curves available in the beltpack. I guess this would be helpful with a live sound system that didnít have a console. The funny curve designations come from the manual (SF = speech filter, IF = instrument filter):



A bonus measurement - completely useless in this case - but pretty. This is a wavelet analysis where the time axis has been recalculated to show cycles at each frequency. Wavelets are like the tone bursts shown earlier, the plot shows what would have happened had a single tone burst at a single frequency been injected into the system and then a plot was made of how it died down over time. This is most useful for resonance studies where the DUT continues to make sound after the stimulus is removed (not good). That does not happen in this wireless system but what does happen (that you can easily see in the phase plot) is that above 6kHz the output begins to lag behind the lower frequencies:



Post Script

Thatís a pun! :) A related post I made a long time ago is helpful for more background on all this trouble we go to avoiding the best solution - a mic cable.
« Last Edit: November 16, 2017, 03:27:29 pm by Langston Holland »
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God bless you and your precious family - Langston

TJ (Tom) Cornish

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Re: Line 6 XD-V75 for Wireless Measurement
« Reply #1 on: November 16, 2017, 04:22:37 pm »

Hey Langston - welcome back!  I'm glad life is a little simpler for you now.

TJ
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Mac Kerr

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Re: Line 6 XD-V75 for Wireless Measurement
« Reply #2 on: November 16, 2017, 04:25:26 pm »

Langston, welcome back! I hope everything is OK with your family, there have certainly been long time members who have expressed concern for you in the intervening years. I'm glad you made it through whatever you have been dealing with and look forward to your continued participation here.

Mac
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TJ (Tom) Cornish

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Re: Line 6 XD-V75 for Wireless Measurement
« Reply #3 on: November 16, 2017, 04:29:31 pm »

More on topic, I own several channels of Line6 XD-V70 and 75.  I have experienced a very high failure rate - both of my bodypacks are now unusable, possibly due to RoHS-related soldering issues, I have a receiver with a dead RF input, and one of my hand-helds literally broke in half when dropped.

I also had to repair a cold solder joint in one of my paddles.  2.4GHhz RF is also increasingly problematic.

When they work they sound great, but I no longer rely on them for show audio.  For a pre-show measurement application, though, they may be just the ticket.

I'm curious for you to do your tests with Shure QLX-D.  Many of us have had great luck with this system, and being digital, I wonder if it would perform similarly to the Line6 for measurement as there is no compander.
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Langston Holland

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Re: Line 6 XD-V75 for Wireless Measurement
« Reply #4 on: November 16, 2017, 05:33:24 pm »

More on topic, I own several channels of Line6 XD-V70 and 75.  I have experienced a very high failure rate...

That is the kind of thing is genuinely helpful and sad. So much promise. I've had the XD-V75 for all of (3) days now.

I'm still using a (9) year old set of (8) UHF-R's for live sound. I bought beltpacks and handhelds for each channel and have had to have about 1/4 of the transmitters repaired over the years - but they got a beating and I consider the UHF-R's one of the best purchases I ever made in this sport.

If someone would send me a QLX-D I'd get it done in a day. I'm also looking forward to measuring the Axient digital system to see if it's just a very nice veneer on the ULX-D or something audibly better.

Thanks so much for your kindness - it's been quite a ride but everyone around here including me is better for it. :)
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Loren Miller

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Re: Line 6 XD-V75 for Wireless Measurement
« Reply #5 on: November 20, 2017, 08:56:39 am »

Wow never thought of using my qlxd for measuring! Thanks for the inspiration, time to warm up the iron!

Rabbit trail- I wonder if there is a capsule that would screw onto the handheld out there that would do a decent job for a quick and dirty room tune?
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Mac Kerr

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Re: Line 6 XD-V75 for Wireless Measurement
« Reply #6 on: November 20, 2017, 09:49:20 am »

Wow never thought of using my qlxd for measuring! Thanks for the inspiration, time to warm up the iron!

Rabbit trail- I wonder if there is a capsule that would screw onto the handheld out there that would do a decent job for a quick and dirty room tune?

It needs to be an omni, and have very flat response. It's probably easier to use a good omni lav on a pack.

Mac
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Ike Zimbel

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Re: Line 6 XD-V75 for Wireless Measurement
« Reply #7 on: November 20, 2017, 10:58:06 am »

It needs to be an omni, and have very flat response. It's probably easier to use a good omni lav on a pack.

Mac
I'm curious to know what effect the latency in the digital systems will have when taking measurements in an actual hall. At the very least it seems like it would skew any delay finder results, yes?
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TJ (Tom) Cornish

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Re: Line 6 XD-V75 for Wireless Measurement
« Reply #8 on: November 20, 2017, 11:28:09 am »

I'm curious to know what effect the latency in the digital systems will have when taking measurements in an actual hall. At the very least it seems like it would skew any delay finder results, yes?
Delay finder is inclusive of the whole path - the desk, the DSP, the air, the wireless mic, etc.  Other than the measured delay being slightly longer, there will be no ill effects as long as the Comesouta equals the Gozinta.
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Mac Kerr

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Re: Line 6 XD-V75 for Wireless Measurement
« Reply #9 on: November 20, 2017, 12:45:24 pm »

I'm curious to know what effect the latency in the digital systems will have when taking measurements in an actual hall. At the very least it seems like it would skew any delay finder results, yes?

As TJ pointed out, in setting delay offsets to speaker zones each measurement will include the same base latency, so the relative offsets between them will still be correct. Any measurements that require accurate data on actual time of flight delay will have to have the system latency subtracted out. In most cases only the differences between zones are important.

Mac
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