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Author Topic: Lectro plug-on transmitters for Smaart  (Read 1257 times)

Don Boomer

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Re: Lectro plug-on transmitters for Smaart
« Reply #10 on: November 19, 2021, 01:21:13 PM »



Line6 technically works very well (certainly better than Xvive, if only for the deterministic latency), but the lack of a plug-on transmitter makes using it with existing microphones a bit painful.


Latency isn't an issue as you can correct for timing errors inside Smaart.  The important thing is that the wireless does not use a companding scheme or data compression as either of these will screw up your measurements.
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Don Boomer
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Michael Lawrence

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Re: Lectro plug-on transmitters for Smaart
« Reply #11 on: November 21, 2021, 05:51:42 PM »

Latency isn't an issue as you can correct for timing errors inside Smaart.

but deterministic latency is critical. I tested one of those Xvive systems and found that they are not time invariant, meaning the latency between Tx and Rx is not stable over time. Some days it was pretty stable, some days I was watching the phase trace wrap over the course of a few seconds. That is not something I want in my measurement loop. As a practical limitation, I had trouble getting them to work at distances of more than about 50 or 60 feet line of sight, which is needless to say, not very helpful for a wireless system.
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Russell Ault

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Re: Lectro plug-on transmitters for Smaart
« Reply #12 on: November 21, 2021, 08:48:54 PM »

but deterministic latency is critical. I tested one of those Xvive systems and found that they are not time invariant, meaning the latency between Tx and Rx is not stable over time. Some days it was pretty stable, some days I was watching the phase trace wrap over the course of a few seconds. That is not something I want in my measurement loop. As a practical limitation, I had trouble getting them to work at distances of more than about 50 or 60 feet line of sight, which is needless to say, not very helpful for a wireless system.

In my experience with it I would say I kind of agree, kind of disagree.

The lack of latency stability can definitely be annoying (although I've never seen it as bad as you've described; I wonder if that means you were seeing a lot of background noise/interference that day? Did you try a different channel?), but I wouldn't have said it renders the system unusable (although some caution must be exercised). The distance limitation is, for me, another real "it depends": for a lot of my applications, I tend to view a wireless measurement mic as a speed-enhancer, rather than a range-enhancer, and the Xvive does a fine job for that.

Is the Xvive a serious, big-name tool for serious, big-name applications? Clearly not. Neither is my RF Explorer, or my "Real World Certifier". But for those of us who exist in the strange middle ground between the LAB and the Lounge (a divide that isn't nearly as clear-cut as it used to be) I think there is a place for "mediocre" gear in non-audience-facing applications, particularly if it means cutting the price by an order of magnitude.

-Russ
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Karl Winkler

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Re: Lectro plug-on transmitters for Smaart
« Reply #13 on: November 22, 2021, 10:09:08 AM »

Still looking to find out what the actual differences are between HMa and DPR when used for audio measurement.
Why buy one over the other? TM400 is not a current product, AFAIK.

Hi Andrew, the difference between HMa and DPR technically is that the HMa transmits a "Digital Hybird" signal based on an FM link with our proprietary digital audio processing, and the DPR transmits a "pure digital" signal based on an 8PSK link. In practical terms, the HMa can be used with older Digital Hybrid receivers like the R400a, the LR, and the Venue/Venue 2 (all in use out there for T&M) AND with the latest crop of digital receivers like the DSQD and DCR822. The DPR being a digital transmitter means it can only be used with digital receivers (DSQD, DCR822, DCHR).

In terms of test & measurement use, The HMa has 3 ms (fixed) of latency, it has a -3dB down point at about 40 Hz (with the filter set at the lowest available value of "35"), and an upper end -3 point at 20 kHz. The phase response, while being within reason, is determined by the high pass filter. The UH400TM, the the HM, now the HMa have been widely used for T&M for the last 15 years.

The DPR has a 3dB down point at about 20 Hz (with the lowest available setting at "25"), it is also a bit flatter in the upper end, and the in-band phase response is quite a bit more linear than the HMa - we did this on purpose - see the frequency and phase trace comparison in Rational Acoustics' article linked from Michael Lawrence's post above. The latency of a DPR link is 1.4 ms (fixed).

The "TM400" is our generic term for our T&M kit - we do still sell them in several forms. The most common is still the HMa sold with the R400a. In Europe, where the R400a isn't available, the HMa is paired with the LR portable Hybrid receiver. Those looking for multi-channel setups generally choose the HMa and Venue 2 (up to 6 channels in a rack space) or now the DPR with the DSQD (4 channels in a 1/2 RU with Dante).
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Andrew Broughton

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Re: Lectro plug-on transmitters for Smaart
« Reply #14 on: November 22, 2021, 10:15:47 AM »

Thank you, Karl, for that detailed explanation. Exactly the information I was looking for.

So... it sounds like the DPR would perform better when being used in measurement applications. Why is the HMa/R400a combo being sold more than the DPR? You'd think compatibility would not be a concern if purchasing a transmitter/receiver combo (the TM400 package as you say) at the same time.
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Karl Winkler

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Re: Lectro plug-on transmitters for Smaart
« Reply #15 on: November 22, 2021, 11:22:00 AM »

Thank you, Karl, for that detailed explanation. Exactly the information I was looking for.

So... it sounds like the DPR would perform better when being used in measurement applications. Why is the HMa/R400a combo being sold more than the DPR? You'd think compatibility would not be a concern if purchasing a transmitter/receiver combo (the TM400 package as you say) at the same time.

Probably habit and price. The HMa/R400a combo has been sold for many years, and still does a good job for a "street price" of about US$2,500 (complete kit with case & M30 adapter), while the least expensive DPR system would be DPR with the DCHR portable digital receiver would run about $3,740. The price per channel would of course come down when pairing multiple DPRs with a DSQD, but still not inexpensive by any measure.
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Tim Hite

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Re: Lectro plug-on transmitters for Smaart
« Reply #16 on: November 23, 2021, 01:19:55 PM »

All good, but who cares what it “sounds like”?

As long as the mag/phase response is good to go that’s all that matters.  Even that can be compensated for with a reference file.

Of course, but with a ~$3000-$4000 price tag maybe it would be nice to use the system for other applications, as well, in which case fidelity would be important.
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Bad Quail
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Re: Lectro plug-on transmitters for Smaart
« Reply #16 on: November 23, 2021, 01:19:55 PM »


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