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Help with understanding Zaxcom ZHD wireless system


Mike H

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I would appreciate some help in understanding this system. I will likely buy either Zaxcom or Lectrosonics. I haven’t been able to reach anyone in Zaxcom Sales or Tech Support for two days.

 

I don’t want to start a debate on the two systems. They are both top quality professional systems. I have a decent understanding of Lectrosonics L Series and just need the same understanding of Zaxcom.

 

The initial use will be very simple for commercials/promos/documentaries, with expansion for indies later:

        - A DPA 4060 lav mic wired to the transmitter (as an option to our Sennheiser MKH-416 shotgun mic).


     - The receiver will be wired into a Sound Devices 702 recorder.


     - The 702 will record, and also will output its input to a RED Weapon camera to facilitate syncing waveforms in post.

-      

 

Questions

-      As I understand it, Lectrosonics Digital Hybrid technology converts analog to digital in the transmitter, encodes in digital, converts back to analog and then transmits analog FM, along with the digital encoding. How does ZHD differ?

 -   I would want to buy the TRXLA3.5 transmitter, correct? (It provides 100mW capability for only $100 over the TRXLT3).

 -   The dedicated ZHD receiver is not yet available. Any ETA? Any description?

 -   If I buy now I would need to buy the QRX200 receiver if I want to use ZHD modulation, correct? When the dedicated ZHD receiver is available, will I being missing out on any capabilities if I just hold on to the QRX200? I worry about buying just before the new receiver is released.

 -   What is the latency of the ZHD system?

 -   What is the bit rate and sample rate of A-to-D converter in transmitter?

 -   What are the major advantages Zaxcom claims for its system, in addition to a recorder in the transmitter?

 

Thank you. Wonderful to have choices between great equipment.

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Hi Mike, sorry you have not been able to get your questions answered. Our dealers are usually the direct source of this kind of sales info. I will be happy to respond to your questions later. I am on cell phone now.

Best wishes.

Glenn Sanders

President Zaxcom Inc.

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Thank you Glenn.

Subsequently, I did get some good info from Nick at Gotham Sound NYC, plus your Tech Support:

- I should be looking at the TRXLA3.5 and the QRX200.
- The QRX200 can receive ZHD modulation, but cannot take advantage of the narrow bands. For my simple system with few channels this is not an issue. In fact, I should use XR instead because of slight advantage in sound quality and latency.
- Your transmitter converts A-to-D, then transmits digital. The QRX200 can send either analog or digital to the Sound Devices 702, so digital out will avoid any conversions at that end.
- There was some confusion on ADC sample rate (32kHz vs 48kHz), but in the specs for the TRXLA3 on your website I find it says 24-bit/48kHz. (48kHz is just right, much better than 32kHz).
- Major advantages: Recorder in transmitter for backup (a big one); only one conversion (A-to-D) versus several (a big one); potential to use narrow bands with a different receiver in the future if my system becomes much more complex (maybe useful, but not any time soon)..

So, for right now I have my questions answered, Glenn............except for a few more:

- I am nervous about buying a receiver just before you produce a dedicated ZHD one. However, am I correct that a dedicated ZHD receiver is a poor choice for a simple system, since I could only use ZHD with the new receiver?
- I am planning on buying the DPA 4060 mic, but I have gotten some advice that I should buy the 4063 to properly match bias. Then I've been told no, some users have had problems with the 4063 and Zaxcom receivers. I wish to buy the 4060, a tried and true product.........is this OK?
- Any other major advantages I missed?

Thanks, Glenn.

 

 

 

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get the 4063. it is the same specs as the 4061, apart from only needing 3.3v to work to its full specs, compared to 5v for all the other mics in the DPA range (apart from the discontinued 4073)
I have used the 4063 with no issues. as have many others here, so would say that the 4063 is also a tried and true product.

if the 702 has a sample rate converter on its digital input, then it will make no difference what the output sample rate is of the QRX200.
there was much discussion about the 32KHz output if you feel the need to look for it. but basically, for 99.99% of what the radio mics will be used for, there is nothing that will be missed above 16KHz in your signal. 
and when i tested it a while back, i was hard pressed to tell the difference between the analogue and digital outs from my QRX200 into my 788.

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The QRX200 is the best choice for a sound mixer. The QRX300 is best used by broadcasters who need the maximum number of channels per MHz. The DPA4063 is the proper mic for our transmitters but others will work almost as well. At one point DPA4063 had some issues with RF but that problem has long been fixed by DPA. I would reccomend the DPA4063.

 

Best Wishes

Glenn

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48 minutes ago, rich said:


if the 702 has a sample rate converter on its digital input, then it will make no difference what the output sample rate is of the QRX200.
there was much discussion about the 32KHz output if you feel the need to look for it. but basically, for 99.99% of what the radio mics will be used for, there is nothing that will be missed above 16KHz in your signal. 
and when i tested it a while back, i was hard pressed to tell the difference between the analogue and digital outs from my QRX200 into my 788.

rich, I was referring to the sample rate of the A-to-D in the transmitter. There is no need to convert in the receiver.
As a mixing/mastering guy for almost 20 years, I will respectfully have to disagree with you on 48kHz vs 32kHz (although I will admit I certainly may be wrong for more common uses, versus mixing music). Just say it is a bias I cannot overcome. But as I said above, the spec sheet says the TRXLA3 sample rate is 48kHz:

https://zaxcom.com/products/trxla3/

If this is correct then I am happy.

48 minutes ago, glenn said:

 

 

Glenn and Jack,

Thank you.  :mellow:

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26 minutes ago, glenn said:

QRX200 outputs either 32 or 96KHz sample rates.

Glenn

Oh, I missed that.  :mellow:

So, in looking at the QRX200 manual, I can set the digital output sample rate to either (1) Normal [which I assume is 32kHz rather than 48kHz] or (2) 96kHz.
Do I read this correctly that, if I select 96kHz:
- the QRX200 will upsample the 48kHz digital file from the TRXLA3 to 96kHz
- I will thus retain all the 48kHz information in the 96kHz digital output to the Sound Devices 702
- I can then sample rate convert back to 48kHz in transferring to Pro Tools in post and not lose any original 48kHz information.

Am I correct on this?
 

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17 minutes ago, Constantin said:

Whatever you do in ProTools, the frequency response of the TRX LA3.5 is limited to 16kHz

I'm sorry but I don't understand what you said. 
The TRXLA3 A-to-D conversion sample rate is 48kHz (if I read the TRXLA3 specs correctly). 
So the digital files being sent to the receiver should retain the 48kHz-sampled file information.............or does the wireless transmission change this somehow?

I also note that the specs say 24-bit. This should define the operable frequency range, shouldn't it?

Sorry but I am not knowledgeable about the effect of the wireless transmission on content of digital data. Clearly I am missing something. Sorry.

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I'm sorry but I don't understand what you said. 

The TRXLA3 A-to-D conversion sample rate is 48kHz (if I read the TRXLA3 specs correctly). 

So the digital files being sent to the receiver should retain the 48kHz-sampled file information.............or does the wireless transmission change this somehow?

I also note that the specs say 24-bit. This should define the operable frequency range, shouldn't it?

Sorry but I am not knowledgeable about the effect of the wireless transmission on content of digital data. Clearly I am missing something. Sorry.

This has nothing to do with digital transmission or sampling rate (the latter possibly). The frequency response tops out at 16kHz. Doesn't matter if the sampling rate is 48 or 96kHz, and nothing will get lost that isn't there to begin with

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The main problem I see (from what I remember from my 744T days)  is that the 702 doesn't have SRC on the AES inputs , So you will be only able to record on the 702 at 32Khz or 96khz if not you will have a SR mismatch


If that is the case, he will have to clock the recorder to the receiver which also means that he would only be able to use one digital receiver.
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if you want full range frequency response. use a cable. simple.
for wireless then the current digital systems will get you as close as you can get for what is commercially available.
i only know the Zaxcom and Audio Ltd systems. 
there is data compression at play in order to get the audio information into the rf spectrum limits required by law. time and technology will improve this. there will always be a compromise between audio performance, rf performance, battery life, size and features.
increasing bit depth and sampling frequency increases the amount of data you have to squeeze into a finite amount of rf space. again, time and technology will improve this.

Audio Ltd have told me that their system operates at 44.1KHz. increasing the sampling frequency increased processor overhead thereby decreasing battery life, and also will increase processing required to get the signal into the rf footprint which increase latency of the system. see. compromises everywhere.

this isnt really a group of people who are overly fussed about the specs of the system. once the equipment is out in our 'normal' working environment, then there are so many other factors that affect what we record, which have a far greater effect than the on paper specs of the gear. once you get to the top end of gear, you can be pretty sure that the gear will sound just fine. its just a question of what suits your needs / method of working / what logo you would prefer to have on your gear / what your friends have / what the internet advises you to get.

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14 minutes ago, rich said:

if you want full range frequency response. use a cable. simple.
for wireless then the current digital systems will get you as close as you can get for what is commercially available.
i only know the Zaxcom and Audio Ltd systems. 
there is data compression at play in order to get the audio information into the rf spectrum limits required by law. time and technology will improve this. there will always be a compromise between audio performance, rf performance, battery life, size and features.
increasing bit depth and sampling frequency increases the amount of data you have to squeeze into a finite amount of rf space. again, time and technology will improve this.

Audio Ltd have told me that their system operates at 44.1KHz. increasing the sampling frequency increased processor overhead thereby decreasing battery life, and also will increase processing required to get the signal into the rf footprint which increase latency of the system. see. compromises everywhere.

this isnt really a group of people who are overly fussed about the specs of the system. once the equipment is out in our 'normal' working environment, then there are so many other factors that affect what we record, which have a far greater effect than the on paper specs of the gear. once you get to the top end of gear, you can be pretty sure that the gear will sound just fine. its just a question of what suits your needs / method of working / what logo you would prefer to have on your gear / what your friends have / what the internet advises you to get.

OK, well stated, I won't belabor it anymore. That I can understand. And I understand that a more limited frequency range can be adequate for speech (rather than music). I would only suggest to Zaxcom that the TRXLA3 specs be changed or elaborated upon because stating 24/48 implies (at least to the uninitiated like me) that these will be the specs of the digital data transmitted. It just seems misleading to me. Enough said.

I agree that the sound is what matters. We will rent gear and compare Zaxcom and Lectrosonics sound quality before making a final decision (DPA lav mics, Zaxcom TRXLA3/QRX200, Lectrosonics LT A1/LR A1).

Regarding sample rate of the 702 recorded material, I don't see a problem recording at 96kHz and then SRCing when later going into Pro Tools. Any problem with this, other than doubling the amount of recorded data?

Thanks again for all the help. I'll report back on the results of the sound quality comparison. 

 

 

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For me, LISTENING is the only truly relevant "spec", but I always have an interest in knowing the stated specifications of any of the gear we use, as well as an understanding of what any given spec means in relation to how it sounds. One thing which you need to know (and may not be mentioned before in this particular discussion) is how frequency response, sample rate and s/n noise floor spec relate to any analog system (like Lectrosonic) and a pure digital system (like Zaxcom and new Audio, Ltd.). With an analog system even if it is capable of "20 to 20K" frequency response and a specific noise spec, in real world use there will be degradation of the signal in both frequency response and noise, depending on wireless range (distance), multi-path, compander distorsion, intermod, etc. With a pure digital system, you get full frequency response and the noise spec throughout the usable range (distance) of the unit. There is an inherent stability and predictability of a pure digital wireless system which I have found to be very valuable during the last 15 years I have been using digital wireless.

Additionally, as someone else pointed out, if you want the cleanest and fullest and most honest audio possible, don't use wireless --- hardwired will always be best. So, if you are wanting to record symphony music at 96K, hardwired to the console or recorder is the way I would do it. I will say that in my experience, the Zaxcom digital wireless with Neverclip preamp and pure digital RF is about as close to hardwired as will ever be possible and the subtle differences are almost impossible to hear.

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There is a vast disparity between the practical world of location sound and the theoretical world of specsmanship.  To say it's only spoken word shows a misunderstanding of what location sound involves.  Myself, and others here, want the best quality sound we can obtain under the conditions we're given. Typically, those conditions affect the sound greatly while sampling rate has a minimal impact that is only discernable under carefully-compared and highly controlled listening circumstances that have no reflection of actual workflow.

I've chosen the system I'm using at any given time, based on a combination of sound quality (actual, not theoretical), features, range, form factor, battery use, and reliability.  Once that choice is made I count on it to perform well and sound as good as a wireless can.

Now, on to the real world...

If I'm on set for a film gig and need to hide a mic on an actor wearing three layers of crinoline, one thought that never enters my mind is the sampling rate of the wireless I'm using. If I'm on a corporate gig and engaging a producer about the uncontrollable room air handler sounding like a wind tunnel, the subject of sampling rate still never enters the discussion.  If a last minute shot change has the talent flailing his or her arms about, again, sampling rate isn't on the radar.

In other words, choose good tools and use them as well as you can under the conditions at hand.  Geeky specs are for idle online discussions but don't carry an ounce of weight compared to, "What does it sound like?"

 

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21 minutes ago, Jeff Wexler said:

Additionally, as someone else pointed out, if you want the cleanest and fullest and most honest audio possible, don't use wireless --- hardwired will always be best. So, if you are wanting to record symphony music at 96K, hardwired to the console or recorder is the way I would do it. I will say that in my experience, the Zaxcom digital wireless with Neverclip preamp and pure digital RF is about as close to hardwired as will ever be possible and the subtle differences are almost impossible to hear.

Jeff,

Is the audio recorded to the Zaxcom transmitter recorder ever used for the final product, rather than the wirelessly transmitted signal? For example, wirelessly transmit the signal to headphones for monitoring and to the camera to enable audio wave sync in post, but otherwise not use the wireless signal?

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The wireless signal and the recorded "signal" (audio) are the same, and yes, the audio recorded on the transmitter card is used in a variety of situations: if the transmitter goes out of range, like if a shot starts with someone getting into a car and then they drive off to a great distance way out of range, the recording on the transmitter (which is timecoded the same as your recorder recording) can be used. There are shows that rely on the transmitter recording almost exclusively and really could not be done any other way. Many people who use Zaxcom wireless and Deva recorder will playback the tracks off multiple transmitters and re-mix and re-record a scene --- this is done even on some episodic TV shows, either to improve a mix or to pick up dialog that was missed due to sound mixer's error or wireless transmission problem.

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