Design CAT cabling for mixed DMX and audio use.

[techfunk]

Hi Guys,

I'm very new to lighting and audio installations, however I've come across an opportunity to supply a fairly large outdoor beach club with a substantial light and sound budget. Whilst not being an engineer I have a reasonable level of knowledge, but lack the formal background to make decisions with confidence on the more technical sides. Of course I will have an engineer to assist me with the project but I will be battling with a language barrier with him being Thai. So I'd like to hear some opinions if I may on the architecture in distributing the audio and dmx signals throughout a quite large venue with 3 separate areas.

I've researched the use of Cat 5, Cat 5e cables etc for transmitting the signals with balun connections. My question is, can I send the lighting DMX signal down the same cable as the audio signal without interference? From what I understand the cable matches the parameters for both signals. To my logic this would work??... Please advise. Also can I
My only concern here is that my goal of lowering costs by using cat cable will be eaten up by the expensive balun connectors and perhaps the suggested conduit for the cable. I can only seem to source the xlr balun connectors for about $20 a piece online. Any suggestions on where to source for cheaper?
My current non Cat cable installation audio proposal has about 600m of speaker cable and 60 odd audio connectors amounting to over $1500 USD. I haven't begun to calculate the DMX cabling requirements yet. At an estimate, there may be 300 m cabling required for up to 20 light fixtures. I guess with this sort of expenditure on cabling, it'll be worth my while using cheap CAT cable?

Thanks so much in advance for your help.

 

[gcpsoundlight]

Yes it is possible, but not as simply as baluns.

While cat 5 (and 5e/6) meet the specifications for both audio and lighting control, to get both down the same cable you would need to encode the signals.
One way would be to use art net for lighting control (effectively dmx over ip), and then use a native protocol such as Dante for your Audio (an open audio-over-ip protocol).

Now, without a decent budget and time to configure, this could be a tricky problem. Plus, if you ask almost anyone, they will tell you running audio and lighting control on the same ip network is asking for problems.

Imagine your lighting console decided to start sending data all over the place. You probably wouldn't notice the change in lighting hugely, but if it happens to collide with an audio packet(s), you would definitely notice the loss of audio.

So, in summary, I would say yes to using cat5 for dmx (you don't even need a balun IIRC) however I would stick with standard cabling for audio.

 

[techfunk]

So, in summary, I would say yes to using cat5 for dmx (you don't even need a balun IIRC) however I would stick with standard cabling for audio.

Thanks so much for your response Gcpsoundlight So Can I assume that a cat5 cable can simply be re-wired directly into a xlr/dmx 3 pin connector with no issues without baluns connector, providing I'm not using the same Cat cable for audio also?
Will need to research exactly which wires go where... I 'm assuming that with double the Cat5 cabling running around the venue,1 for audio, one for dmx light control, then the costs for all that cabling will still come in below speaker cabling and DMX cabling specced prices?
Appreciate the help.
Cheers

 

[gcpsoundlight]

Yes and no. For the lighting side, you would be correct. For the audio, it depends on what you want to do. If you are connecting your amplifiers to your speakers (assuming a passive system) then you would need to use proper rates speaker cable.
If it is an active system (ie: the amplifiers are built into the speakers) then in theory you could use each pair in the cat5 (there are 4 pairs - blue, green, brown and orange) for a signal assuming it was shielded cable.

For microphone or other input sources, you really should use proper microphone cable.
The reason being is that your outputs from the mixer or CD player is line level (usually +4db) whereas your inputs are low level (between -50 and -30db). This means that the line level signal will be much less susceptible to interference.

 

[JD]

Let me jump in and play devil's advocate here: Cat5 is 4 pairs. DMX uses 1 pair per universe (plus ground/common.) One would think if there are spare pairs available, one could put an unrelated digital signal down the pair. (digital audio) Here's where I have a problem: CAT5 is only suitable for DMX if run through metal conduit. The conduit provides the mechanical protection as well as the missing shielding. If you are running digital signals from separate sources, there is nothing shielding the signals from each other. CAT5 has enough twists per foot to keep the line isolated from digital noise crosstalk, but not from good-old analog ground loop interference. Although the noise level between the equipment would have to be substantial enough to obscure the differential signals, it could still happen. CAT5 is cheap enough that I would not risk it. Separate conduits would be ideal, but separate cables would suffice. Why set yourself up for an obscure problem months or years from now? at 10 to 14 cents per foot, CAT5 is just too cheap to not run separate.

 

[Morte615]

It's my opinion (YMMV) that the only reason to run cat 5 or cat 6 at this point for lights or audio is if you are doing it over an IP based system (ArtNET, NET3, ect.)
Yes you can run it directly over the cable itself but for the extra added cost (and not much when you consider the cost of the balun) you should go for an IP based system to simplify everything and make troubleshooting easier down the road. Also it will make the system a lot more future proof.
I should probably qualify this opinion and say that my background was IT before getting into theater so to me this is second nature. But even so networking is becoming main stream now.

 

[JD]

DMX on CAT is direct wired. No Balun needed. KnowledgeBase: DMX Over CAT 5 - Electronic Theatre Controls

 

[derekleffew]

Some thoughts:

...I haven't begun to calculate the DMX cabling requirements yet. At an estimate, there may be 300 m cabling required for up to 20 light fixtures. ...

300m for 20 fixtures seems excessive and is pushing the practical limits of distance for one stream of DMX512. Unless this is an outdoor architectural installation lighting a large building.

... So Can I assume that a cat5 cable can simply be re-wired directly into a xlr/dmx 3 pin connector with no issues without baluns connector, providing I'm not using the same Cat cable for audio also? ...

There's a problem with terminating UTP cable's solid conductors to an inline connector. You can't just solder the solid conductors--that's an invitation to failure.

Don't forget that category cables with solid conductors can only be reliably terminated into insulation-displacement (vampire tap) wiring devices intended for the purpose.

Don't strip the cable and terminate to compression screw terminals, crimps or solder joints--that will cause big reliability issues!

Terminating to IDC type RJ45 connectors solves this issue, but as you've found, CPoint products or similar do quickly add to the cost, negating most of the savings of the less-expensive wire. I don't think they actually qualify as balun s; they're really just adapter s.

Further, planning infrastructure based on 3pin XLRs is neither wise, nor DMX-compliant. High-quality lighting equipment follows the ANSI E1.1-2008 standard and uses 5pin XLR.

 

[TimMiller]

Honestly dmx install grade cable is cheap. Buy snake cable to run from front of house to the stage, this will be some of your most expensive cabling but saves money in the long run. Also if the building isn't built yet get them to put in conduit runs in the slab where necessary. A spool of 14 awg 2 pair speaker cable isn't much money either. I wired up a church with dmx 3 adc patch bays, all cabling came out to be less than 3k. I also ran cat 5 all over the place. Also are they using conventional lights or movers? What about dimmers and all of their cabling. Even if you are doing the communications side of the wiring try to meet with the electricians as much as possible to find out where they are putting things so you can run wire accordingly. Also run any type of communication wire as far away from electrical lines especially dimmer and high voltage as possible. Personally I do not like to try and take the cheapest route because if it fails you eat the cost to make it right. Also if you are going to be hanging the speakers and such do you have a certified rigger and the liability insurance to cover you if something were to happen? Also speakers designed to fly cost substancially more than those that do not.

 

[Footer]

First, This is all a bad idea. You should never pull a run of cat 5 beyond 100 meters, ever. After 100 meters the digital signal will degrade and it will be unusable. Even if your going to use it for something besides Ethernet it is still a bad practice.

Now, without a decent budget and time to configure, this could be a tricky problem. Plus, if you ask almost anyone, they will tell you running audio and lighting control on the same ip network is asking for problems.

This is not at all true anymore. First, you can segment audio and lighting via network segment or VLAN. There is no reason why they can not both exist on the same backbone. JohnHuntington does it, and if it works for him it works for me.

 

[Chris15]

The Sydney Opera House runs ONE network.
Sure there are VLANs ( I think it's 20+ of those), but it's one network and it is running a variety of show critical systems including automation, DMX and a bunch of other things. Dante was also running on that network but they've reverted to AES for reasons unrelated to the network or Dante itself. And email. And the SOH website. And...

The only reason not to run a converged network is when multiple contractors are involved and that's just politics at play...

 

[gcpsoundlight]

I understand that you can, and I have seen many examples of it working properly. However, I always like to be sure in show critical applications. Often when I am implementing something like this I don't have the budget to get the hardware required to do it reliably, and it often works out cheaper to use 2 cat 5 runs and isolate the systems.
Anyway, by the sounds of it the OP was wanting to use it as a substitute for analog cable, not run a AOIP situation.

 

[Chris15]

I don't have the budget to get the hardware required to do it reliably

If you can't afford reliable ethernet infrastructure, then how are you affording signal over IP hardware?

So that we're perfectly clear, anything over IP is NOT the recommended solution for low budget operations - this is "big boys toys" - Ethernet can be rock solid, but it is going to cost you in both upfront capital and in having people who KNOW how to drive it.

Cobbling together networks from whatever is just asking for trouble...