Issue #6, August 2002

Save those DMX512 cables!

Over five years ago, when ACN started, Doug Fleenor Design assured hundreds of concerned clients that support for DMX512 would continue for years to come. Now, more than five years later, the ACN furor is likely to confuse the industry once again; ESTA has voted to hype the project.

At the ESTA meetings held last month, the ACN task group reconfirmed their belief that ACN will replace DMX512. Yea, right! Cell phone developers thought they d obsolete wired phones and e-mail proponents felt the postal service would shrivel and die. Sure new technologies have an impact on tried-and-true solutions, but ACN will never replace DMX512.

ACN lacks a major factor that made DMX512 successful: interconnectability. ACN doesn t specify a connector, doesn t specify a physical media (twisted pair, fiber optics, coax, etc.), and doesn't t insure interoperability. ACN is a software suite offered up for manufacturers to use as they see fit. With luck, ACN may help make today s incompatible Ethernet based products work together, but replace DMX512? Hardly.

ACN is still years away. There is a misconception that ACN is almost done. True, the task group has produced a draft for a portion of the specification. But 2/3 of the specification has yet to be written. After the entire draft specification is complete it has to be voted on by the Control Protocols Working Group and then by the Technical Standards Committee before being released for public review. Public review can take 6 months or more after which any public comments have to be addressed. Changes required by public review will take additional time after which the voting and review process starts all over. A draft can go though several public review cycles before becoming a standard. Plan on two to three years after the draft is complete before ACN is released.

ACN will not be cost effective in most devices. A $20,000 console or a $10,000 dimmer rack can bury the additional cost of ACN but a $200 fog machine or a $1,000 dimmer pack probably cannot. Luckily companies like Doug Fleenor Design will offer ACN to DMX512 interfaces to bridge the gap.

My prediction is that in five to ten years ACN will be running over Ethernet as a back bone in permanent installations. The console(s) will output Ethernet incorporating ACN protocols. This will run directly to permanent dimmer racks, and will be distributed throughout the facility to DMX512 interfaces. Most portable devices will continue to run DMX512.

The folks that maintain the Ethernet standard have a current project titled Ethernet, the first mile. This group is writing a standard that will allow Ethernet to run great distances over virtually any wire, including 120 ohm shielded twisted pair. So in twenty years, if DMX512 becomes as rare as Analog 0-10 is today, you will still have use for your old DMX512 cables.