Now that I'm well on the wrong side of the big four-oh, I find it's the little things that can create truly big aggravation. Like having a hard disk crash days after the last backup. Like waiting in the EZ-Pass toll lane behind the guy who magically remembers, 4' from the toll booth, that he doesn't have an EZ-Pass. Like having to deal with 3-pin XLR connectors on DMX512 systems.
Now, I can hear you saying, "Really, Steve, 3-pin XLR connectors? Aren't there more important things to get aggravated about?"
Last week I decided to punish myself and consider the total expense caused by the use of 3-pin XLR connectors on DMX512 systems in rental stock at Production Arts. That cost includes carrying a completely separate cable inventory, countless adapters, and a separate inventory of 3-pin optically isolated splitters. It also includes the annual labor to manage that separate inventory of gear. Having wound up with a very large annual amount, I moved on to think about all the permanent installations that we have done that needed both 3-pin and 5-pin DMX512 cable plans to service various pieces of DMX512 equipment. Then I thought about all the other lighting companies worldwide that have to carry dual cable inventories, and the technicians who must load-in shows with two cable inventories. By then I was truly aggravated.
Why, I asked myself, has our industry allowed itself to get into this mess? Turns out that back before DMX512, a couple of moving-light manufacturers decided that the 3-pin XLR would be a good connector to use for their relatively low-speed data link. This would have the added "advantage" of encouraging the end user to use microphone cables, a basic commodity item in the manufacturers' primary market: nightclubs. Then one day these manufacturers found themselves getting a portion of the professional market where DMX512 was a requirement. Presto! The 3-pin XLRs were now carrying DMX512 data with no additional hardware cost to the manufacturer. The additional cost of two 5-pin panel-mount XLR connectors (one input, one daisy chain output) had been saved by the moving-light manufacturers. They justified this by arguing that it kept the prices of their products more competitive. To put this in perspective, the marked-up difference in cost for two connectors was perhaps $15.
But what really happened to that $15? Where did it go? Because the majority of the industry stayed true to the DMX512 standard's requirement to use 5-pin XLR connectors, the $15 landed squarely on the shoulders of the end user. But because he or she had to acquire adapters, separate cable inventories, and separate splitters, that $15 grew by an order of magnitude when it was "transferred" to the end user.
It turns out that I'm not the only one who is aggravated. The VPLT (the German trade association equivalent to ESTA in the US and PLASA in the UK) recently conducted a survey of the market on the DMX512 connector issue. The results are interesting, to say the least:
*91% of respondents use 5-pin connectors, while only 9% use 3-pin;
*73% of respondents need to use 5-pin-to-3-pin adapters;
*An overwhelming 91% of respondents' conventional control consoles use 5-pin connectors;
*86% of respondents' moving-light consoles use 5-pin connectors;
*82% of respondents' dimmer packs and interfaces use 5-pin connectors;
*And here's the rub: Only 45% of respondents' moving lights use 5-pin connectors, while 55% use 3-pin XLRs.When asked to give their opinion on the "c onnector problem," a whopping 91% of respondents said, "Use the 5-pin XLR exclusively." I'm no statistician, but it sure looks to me like the moving-light manufacturers are the mavericks here and the market wants 5-pin connectors in compliance with the standard!
While we're at it, let's talk about compliance with the DMX512 standard. The standard states: "Where connectors are used, the data link shall utilize 5-pin 'XLR'-style microphone connectors." It does not say "Use 3-pin connectors if you feel like it." At a recent meeting of the ESTA Control Protocols Working Group, a proposal was introduced to recommend to USITT that the standard be modified to allow 3-pin connectors. The proposal was soundly defeated by a very broad spectrum of manufacturers and end users that make up the Control Protocols Working Group, including a representative from one moving light manufacturer that is one of the biggest 3-pin offenders! Go figure!
The DMX512 standard has been a success because it allows simple interoperability of equipment made by different manufacturers. It seems to me that the most basic requirement of such interoperability is a standardized connector that allows the equipment to plug together, without having to get out one's soldering iron to make an adapter! Is a device with a 3-pin connector compliant with the DMX512 standard? The answer is no. If the manufacturer uses a 3-pin connector and states that the product is DMX512-compliant, it is misleading the buyer. But unfortunately, these manufacturers have got the market well-trained. The buyer must pick up the costs associated with the 3-pin connector, because there is not much choice if he or she wants to use the equipment.
The ESTA Control Protocols Working Group is in the process of developing a tool for equipment purchasers: the DMX512 Protocol Interface Compliance Statement, or PICS. The PICS will be a questionnaire that takes every declarative statement in the DMX512 standard and turns it into a question to be answered by the manufacturer of a piece of equipment, for the benefit of a potential buyer. The results of the questionnaire will allow the buyer to quickly "score" a piece of equipment for compliance with the standard. This should give some indication, in advance of a purchase, of how much effort the end user will need to expend to interconnect the equipment to a standard DMX512 network. For example, Question 21 of the draft PICS says, "Are the connectors used all 5-pin XLR-type microphone connectors?"
The results of the VPLT survey and the recent defeat of the 3-pin proposal in the ESTA meeting raise a question for me: Who is it who actually wants to use 3-pin connectors in this industry? Some manufacturers have told me that their customers "want to use microphone cable." I don't see the use of an improper cable that is not designed to transmit 250kbps data as a plausible reason to use 3-pin connectors. Another argument I have heard is that it would be "too painful" to make the transition to 5-pin connectors since there is such a large volume of 3-pin connectors in the installed base. Too painful for whom? For many end users, every additional 3-pin connector that they purchase creates an ongoing expense and painful headache that never stops. And every 3-pin connector creates a new "roadblock" for users of the second data link on pins 4 and 5 for the DMX512 data link.
I think it is time to tell manufacturers that our industry is no longer going to accept the "transferred" costs of non-DMX-compliant equipment using 3-pin connectors, no matter how good the rest of the product!
Steve Terry is the executive vice president of Production Arts, where he heads the Systems Integration Group. He is a member of the ESTA Technical Standards Committee, and the co-chair of the ESTA Control Protocols Working Group. He is a USITT vice commissioner for engineering, and the alternate USITT representative to National Electrical Code Panel 15. In the distant past, he chaired the USITT committee that wrote the internationally accepted DMX512 standard.