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Lectrosonics has long owned a majority stake in the North American film and television audio market. Their Digital Hybrid wireless is massively successful. Using digital audio processing in the transmitter and receiver, they effectively removed the companding noise used in traditional analog wireless systems. Lectrosonics has finally answered the all digital call of their competitors with the D4 Digital Wireless system.
The D4 is a simple send and receive wireless in the 902-928 MHz range. The increasing number of four channel production cameras, such as the RED, gives an immediate home for the D4 in workflow. The BEC Group is already working on a camera mounting product for the D4R.
Starting at the transmitter, the D4 has external power input and four line level analog balanced TA3M audio connections. The first two connectors also double as four channel AES input jacks. The front or top panel of the system displays each input in an easy to read backlit LCD. Menu options on the transmitter include frequency tuning, audio trim, AES3 modes, 2 or 4-channel mode, and a system lock. The transmitter outputs 200mW of power. The receiver has identical rear connections as the transmitter. The menu options are also identical with the addition of a headphone volume control and calibration tone. The D4 system processes audio at 48 kilohertz and 24 bit. Lectrosonics own documentation states “ruler flat 20-20,000kH” response.
With the assistance of my good buddy Rob Milner from our Nashville sales department we performed three walk tests. The first two tests set the transmitter in the center of our service department–surrounded by walls, cables, and a steel & concrete structure. I took a walk.
The first thing you notice about the D4R’s LCD readout is the obvious bar across the screen. This is most useful RF signal readout I’ve ever experienced. Unlike LED’s, subtle changes are more obvious, allowing me to adjust my position for optimum reception. Walking down the parking lot from our front door, I began taking hits at about 210 feet in 4-channel mode. Rob was reciting a fascinating brochure from our service department about service for SQN mixers.
In the next test we switched the units to 2-channel mode and set out. This time, the system stretched to about 320 feet. Considering the concrete and steel building between us, we were impressed. Having line of sight changed this dramatically. For our final test, also in 2-channel mode, Rob went official–Sound Devices 442, with a Sanken COS-11 out of the mixer and into the transmitter.  This time Rob did the walking. I stayed just outside of the Trew Audio front door. We arranged some hand signals and sent Rob on his way. A side story now develops.
We enjoy doing walk tests in the parking lot across from our store. A larger insurance conglomerate owns it. We generally take bets on how long or far we can get before their roving security and parking lot shuttle drivers interrupt our tests and ask us why we are on their property. (I’ve personally been asked to leave a blood drive on their premises, because I am not an employee.) Â So sure enough, half way across the lot Rob was stopped and questioned. Of course, for me back at the store listening to Rob’s grace under fire was much more enlightening than his reading of the SQN service paperwork. Rob asked the security personnel if they would rather he continue across their parking lot to the public road, or return the way he came. This confused them, so he continued in his original direction.
He made it .09 miles, before the signal dropped out. That is 475 feet give or take an inch. Lectrsonics Digital Hybrid systems have similar distances, but don’t carry two channels of audio, let alone four. And the D4 audio quality was impeccable. Lectrosonics first mass market digital product blew us away in our distance tests. It definitely impressed us as it weathered a hot July day (and some hot air to boot) without flinching. We look forward to finding the perfect niche for the D4 system in your kit.
Learn More about the Lectrosonics D4 Wireless System (280K PDF)
Lectrosonics D4 Wireless System Instruction Manual (1768K PDF)
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When feeding a camera or recorder with 4 channels of digital output at 48kHz 24 bit how does one feed a clocking signal to the receiver in order to reduce jitter?
As far as we're aware, their is currently not a clock input or output.
There are only four freq's to use. I wonder if, when this gains the popularity that I imagine it will, will cam/sound teams be stepping on each other at crowded news and media events.
Is the D4 receiver compatible with UM400 series transmitters? I could see this being a great thing for ENG bag use. One small format receiver for 4 transmitters on separate individuals.
Sorry, Matt the D4 is full digital. The UM400 is a digital hybrid (analog transmission) product. The D4 also does not broadcast in the same frequencies.
Oh boy, another format of hardware to buy with no backward compatability. Looked at the 3 channel Fostex mixer on this page as well, Looks good , be better if it had 6 channels.
In response to Matt's and Thomas' comments:
Matt, the Lectro D4 system is a single transmitter and a single receiver. To help clarify: The transmitter is not a box with four transmitters and the receiver is not a box with four receivers; The system is one transmitter, one receiver, and four audio channels. Sound impossible? Think of it as a wireless Firewire cable system (like Metacorder) that can stream multiple channels with a single cable.
Thomas, aside from being on a different frequency spectrum, the reason that the D4 system cannot be used with other commonly used Lectro 200 and 400 series systems is because the D4 system transmits digital audio while the 200 and 400 series transmits analog.
The obvious use for the D4 is as a wireless high quality audio mixer to camera link (Red Camera and others come to mind), but other uses are starting to come to mind, too, even as I write...
I was recently working on a movie scene that took place in a drive in theater, and, because of the distance and obstacles involved (rows and rows of moving cars), we needed to get the audio from from the projection house wirelessly. As it turned out, a mono feed was adequate (a Lectro 400 system worked fine), but the D4 system would have allowed a stereo track. Come to think of it, communication from the projection room would have been very helpful, and the D4 system would have also accommodated a talkback channel from the projectionist. See... it's happening already... When we have the technology, we often find ways to use it to our advantage.
Glen Trew
Wow. That is great. Truly a shift in thinking. I guess I was still thinking about it like an old Quad Lectro system. I still hope they come out with something that would allow me to use something this small in my bag with multiple transmitters. The Venue Bag system is just too big and clunky.
Thanks for the technical clarification!
-Matt
Glen,
Without a clock input on the transmitter or receiver, how does one avoid jitter when using digital throughout?
Tom Hidderley
Hi Tom,
There is no external sync on the receiver, so if using the digital outs of the receiver, the receiver AES signal becomes the reference for the input device. As automatic SRC (sample rate conversion) becomes more common (the newer Deva 5 and Cantar come to mind), master/slave clocking becomes less of a concern.
Glen Trew
I'm curious how it will work sitting next to my 201/401 receivers in my bag. I have had some problems with transmitters near my receivers in the past. I think very careful allocation of frequencies reduces this but really, I don't have the time (and brainpower) to carefully allocate frequencies of 4 wireless talent and 2 wireless hops in my normal Eng shoots. Especially since I am choosing my freqs at the last moment based on location scanning on the receivers. Placing the wireless hop transmitter on my belt away from my bag is an option but then my body will at times be in between the camera and my hop transmitter. Maybe thats not a big deal.
I can't wait to hear more about it.
Robert
Hi Robert,
There is such a wide gap between the frequencies of common analog wireless mic transmitters (even the Lectro hybrids) and the frequencies of the D4 system, that the interaction should be negligible to nonexistent.
Glen Trew
A couple more questions seeking anwers or opinions.
First is Power. Powering the receiver from a large camera is simple enough but what when using with an HVX or similar small camera. As far as I know those cameras do not have a power port for external devices. I have in the past placed two 9v batteries in parallel to power things like my old shure mixer and am curious if that might be an option for powering the D4's. Especially the Transmitter since I do not use a central powering system in my bag (just more stuff to carry). What powering options are people using or considering.
My second questions is about using this system indoors in tight quarters and spending most of the day within feet, or inches of the camera person and therefore putting the transmitter and receiver in close proximity. How will it handle multipath reflections, (RF reflections) in a small box of a room? Of course you might say just go hard wired here and that is what I do now but anybody who has been tied to a camera operator in a small room with 6 or eight people shooting a reality show understand the desire to go wireless. Any thoughts.
Robert
Hi Glen,
Am I right in thinking that as this is only one transmitter, one receiver (& I gather the signal is multiplexed) that a drop-out wont affect just one of the channels but will actually affect all four? What I'm getting at is whether the D4 can be used for redundancy purposes.
Still a marvelous device in any event.
Thanks,
Ben
Ben,
In the digital realm it is all or nothing. The receiver only receives one frequency from the transmitter. That frequency carries all four channels of digital audio. So if you have one drop out, that means you have a four channel dropout. Hope that answers your question.
> First is Power. Powering the receiver from a large camera is simple enough
> but what when using with an HVX or similar small camera. As far as I know
> those cameras do not have a power port for external devices. I have in the
> past placed two 9v batteries in parallel to power things like my old shure
> mixer and am curious if that might be an option for powering the D4’s.
> Especially the Transmitter since I do not use a central powering system in
> my bag (just more stuff to carry). What powering options are people using or
> considering.
>
> My second questions is about using this system indoors in tight quarters and
> spending most of the day within feet, or inches of the camera person and
> therefore putting the transmitter and receiver in close proximity. How will
> it handle multipath reflections, (RF reflections) in a small box of a room?
> Of course you might say just go hard wired here and that is what I do now
> but anybody who has been tied to a camera operator in a small room with 6 or
> eight people shooting a reality show understand the desire to go wireless.
> Any thoughts.
>
> Robert
Hi Robert,
Since the transmitter does not have an internal battery compartment, it must be powered by an external source of some kind. I measured the current draw of the D4 transmitter, which turned out to be 0.45A (450mA) at 12V, or 0.6A (600mA) at 9V. External battery choices that com to mind for bag use are NP-1, V-lock, or a handful of 9V batteries in parallel. So, since the D4 would have to be powered with an external supply anyway, you probably might as well use that same supply to power the rest of the bag (less stuff to carry :) ) In case anyone is wondering, I also measured the receiver (idle, no audio) which pulled 0.2A.
The closer a transmitter is to the receiver, the less significant multipath from reflections will be. Because of the "trip factor", a wireless link to the camera is very helpful when working in a crowd of people, even if you can stay very close to the camera. The walk tests that I have done have been specifically to see how far away the transmitter can be from the receiver (not how close), but I did not experience any dropouts that were caused by being too close.
Glen Trew
Ben Hooft said on August 9th, 2009 at 12:07 am:
> Hi Glen,
>
> Am I right in thinking that as this is only one transmitter, one receiver (&
> I gather the signal is multiplexed) that a drop-out wont affect just one of
> the channels but will actually affect all four? What I’m getting at is
> whether the D4 can be used for redundancy purposes.
>
> Still a marvelous device in any event.
>
> Thanks,
>
> Ben
>
Hi Ben,
You are correct... All of the audio channels are sent together as one bundle of information. Think of the transmission like an invisible firewire cable that carries many audio channels of information.
If I understand your question about redundancy, you are also correct that more than one transmitter cannot be used to feed a single receiver. However, for the sake of redundancy, more than one receiver may be used with a single transmitter (such as when feeding multiple cameras).
Glen Trew
Hi Glen,
Thanks for your response. What I was getting at as far as redundancy is concerned is sending 2 channel mono from a mixer to a single camera. If you were using a dual Tx/Rx set-up one would act as a back-up to the other (it's unlikely both signals would both drop-out being on completely different frequencies).
With the D4 however, it would seem as all the channels are bundled together, you can't use it in the same way. All channels will fail during a signal drop-out, not just one.
Cheers,
Ben
You are correct, Ben... one transmitter channel, up to 4 audio channels. However, an advantage of redundancy can be achieved in two or more audio channels. For example, one input channel can be set a few dB low in case of an unexpected hot peak. Also, 2 or more audio channels will give some insurance against a mixer output failure (or operator error) or input/output cable failure.
Glen Trew
(sent from my iPhone)
V2.0 of the D4 system firmware adds up to 8 channels for stereo mode (2 channels) and 4 channels for Quad mode (4 channel). I have been beta testing this system for over 2 months now and you can read more about this on my blog under "Lectrosonics" - http://web.me.com/farroutpro
I recently tried using a Lectrosonics SR kit as a bag-to-camera hop and at first could not figure out why I intermittently had an unusually high noise floor jumping between the two channels, rendering the link unusable. After much production-interrupted fiddling and troubleshooting I discovered the problem-- RF overload. Anything closer than three feet between the transmitters and the SR receiver caused a problem.
It will be interesting to see if this new Lectro D4 system exhibits a similar inconvenience, shall I call it.
Larry
I just wanted to point out a significant compatibilty issue for those considering importing or using the D4 in Australia.
The following has been taken from http://www.comlaw.gov.au & can be verified on numerous other web pages.
"The ISM band around 900 MHz that is specified in the national and international standards for Industrial, Scientific and Medical (ISM) equipment is not correct for Australia. The standard shows the international allocation for the ISM band (902 to 928 MHz) where the ISM band in Australia is limited to 918 to 926 MHz. The frequency range between 902 to 918 MHz is used for GSM mobile services in Australia. The remarks column therefore amends the application of the standard to the correct ISM band for Australia pending modification to the International Standards to address these issues."My understanding of this is when using the D4 in 4-Channel mode in Australia only one of the four 4 MHz channels would be available (unless you were out of GSM range). Thus only ONE D4 could be used at once NOT FOUR because the 907, 912 & 916 MHz channels are being used by GSM services in Australia. Though unlikey, if two Sound Recordists showed up to one location, both sporting D4s in 4-Channel mode in Australia, there would certainly be issues.
So Australian buyers beware, not to mention visiting fellow Sound Recordists from the other side of the Pacific! :-)
I will try to answer some of the questions raised above:
1. We recently added the capability to divide the spectrum into 8 two channel frequencies or various combinations of two channel and four channel frequencies. There are some restrictions but normally you can get to where you want to go with the right frequency selections. Each 2 channel frequency is half the band width of a four channel frequency.
2. The 908 MHz band is far enough away from current part 74 frequencies, 470 to 700 MHz, that we have not been able to cause any problems with a D4T and our receivers in the same bag.
3. It works superbly in high multipath situations such as in a car parking lot or in a small box of a room. Each bit of information is sent 4 times at different frequencies, that is to say it is spread spectrum.
4.As noted above, the signal is already highly redundant. Dropouts are much fewer than any analog or digital part 74 wireless. We are using huge bandwidths and sending redundant signals over a spread spectrum link.
5. Yes, you will have total 2 or 4 channel dropouts but they are much more rare than a regular wireless of any type. Also the dropouts at extreme ranges are very gentle.
6. We have not been able to induce problems from having the transmitter too close to the receiver. It has two stages of AGC to prevent that.
7. The problem with the SR overloading at a three foot distance is a known problem, has a factory fix and is covered under our "We screwed up and we'll fix it free at any time" policy.
8. I'm currently confused about Australia regs so I'm no help.
I have a question about the antennas. Are they a hard rigid plastic or are they flexible like other radio mic antennas. The reason I ask is when considering mounting the Rx on a RED do the antenna flex if they were bumped or if they had pressure placed on them. I also understand that they have a movable right angle joint at the bottom, and this is not what I'm asking about.
The antennas are stiff and will break if you bend them anywhere other than at the hinge point.
Reference the 900 MHz ISM band in Australia.
Ben Hooft is on track with his general statement about our ISM band being smaller than in some other countries. My understanding is that it is 915-928 rather than 918-926 MHz (according to ACMA’s Radiocommunications (Low Interference Potential Devices) Class Licence Variation 2007 (No. 1)
Maybe it has changed since 2007?
In either case, that does not necessarily imply that you can operate wireless mikes up there.
Here in Oz, we operate wireless mikes under the provisions of a Class Licence for Low Interference Potential Devices (LIPD). The only specific UHF spectrum for wireless mikes is on unused TV channels between 520-820MHz.
The 900MHz ISM band, however, does have a general concession for ALL TRANSMITTERS of 3mW peak power.
Also a provision for DIGITAL MODULATION TRANSMITTERS, of one watt output, on the provisos that;
1. The radiated peak power spectral density in any 3kHz is limited to 25 mW per 3kHz.
2. The minimum 6 dB bandwidth must be at least 500kHz.
FREQUENCY HOPPING TRANSMITTERS are also acceptable at the one watt level providing they use a minimum of 20 hopping frequencies.
I’ll leave it to Larry to state whether his product complies with any of the above specs as I have no specific knowledge of it.
Hoping this helps….
Bill White
Microphone Magic.
Has anyone tried the D4 with the Panasonic HDX 900 camera?
Gary
I have been testing the D4 system since June 09 and used it with just about every camera we would use in production.
The HDX900 in a analog input camera and you would use the D4R in analoge mode to feed the camera. The HDX900 as well as all other full size cameras with power on the Hirose or the Anton Bauer tap will provide power to the D4R.
The last time I checked The BEC Group was going to offer a cage for the D4 system but they are not shipping yet. The maker of the straddle bags in Santa Monica is offering a soft case that will hang from the camera for approx $35 USD.
You can follow my continued testing of the system with new firmware on my blog. link at the top of this posting.
Hi Scott,
Thanks for your comments. Were you using a dual female XLR to 5pin male to the front camera input to access channels 3/4. Any distortion problems? Did you use the AGC?
No I wont use inputs 3/4 on the camera. You can not turn off the AGC. You have no control of the levels. But you can use two female TA3's to a male XLR5 to feed those inputs. Remember that it is a mic level only input with no controls.
So then you are using the D4 to feed only 2 channels of audio to the HDX 900?
When I used it with that camera, and most others, yes. But mostly I use it to feed a mono mix on ch1 and send timecode on ch2 if the camera can accept external timecode and I am recording sync sound.
I must have missed the earlier comment but is it correct that there is NO BATTERY COMPARTMENT in either in the D4 transmitter or receiver?
I ask as I happily run my mixer & all my equipment on internal batteries. Indeed 2500mAh NiMH AA's provide my mixer with over 12 hours operation time (with Phantom Power).
I just used the D4 system for the first time as camera hops and was very impressed with the sound quality and the range. I did have some issues that I'll explain.
The mixer I used was a SD 442 and the camera was a panasonic Hdx900. Pretty standard fare in reality world. I had a hard time getting proper levels sent to the camera. With tone coming from the mixer to the D4t analog to the D4r, line level input into the camera, I could never get tone to line up at -20db ( defacto standard on most cameras) and not have the mics clip at the camera. In other words, no matter what I tried, the signal to the camera was either too low or clipping. I like to have my meters match on the mixer and camera so I can monitor both but this was tough to set up.
If anyone has experience with using the d4 to a camera as a wireless-to-camera hop set up I'd like to know how it worked for you. The show I'm working on has a lot of shouting which Makes it tough. Thanks!
When working with cameras like the hdx900 or varicam etc you also need to go into the camera audio menus and adjust the settings there to reach unity at either mic or line level. I haven't had any trouble getting line level across the board and I use -18db as my base.
James,
I am currently working on a reality show under the exact conditions. Out of my 442 I had to set the D4 transmitter to -12 then I had to set the D4 receiver output to +8 in order to achieve -20 at the camera.
Let me know if this works for you.
Gary A. Bruckner
Check the audio section of the hdx900 user guide - page 129
http://web.mac.com/farroutpro/sound/user_guides.html
Thanks Gary and Scott. I'll be back on that job on Sunday and report back. Scott- the manual page you indicated shows 3 choices -3, 0 or +4. What setting in the camera have you used with the D4?
+4 is my guess.
I thought that -3/0 and +4 were simply output settings for the camera
Got the D4 dialed in finally. Settings are -20db on the D4t and +6 on the D4R. I have the line input gain on the panasonic HDX900p set at -3db in the menu (thanks Scott Parr). That allows me to send tone from my 442 and have -20db on the camera meters and most importantly be happy with the audio.
My camera op broke an antenna already. I'd like to de flexible antennae in the future.
Football world cup S.Africa.Many cameras,plenty of D4's.Will you be able to use D4's in this environment.Will there be interference from one D4 to the next.How!!
You have a total of 8 RF freqs to pick from in two channel mode. In four channel mode you only get 4 RF freqs. Just like any other system if you have two transmitters on the same freq you will get RFI.