Economic but reliable DMX splitter with RDM support

[jeiw]

Hi,

 

I just installed a fixed DMX installation in my small theatre. I have 12 distinct DMX lines running to the ceiling and stage floor and both my lighting console (Zero88 FLX) and my fixtures (ETC SourceFour Series 2 Lustr, ETC ColorSource PAR) are RDM capable so I need one or many DMX/RDM splitters in order to use my devices at full potential (RDM is especially useful to me as I have a fixed ceiling rig that is not very easily accessible, so remote configuration of fixtures will save me quite a lot of time and spare my back from carrying ladders back and forth...)

 

As I spent all available money on the console and fixtures, I looked for the cheapest DMX/RDM splitter available and decided to buy two Showtec DB-1-8/RDM, thinking that if it is advertised as a RDM capable splitter, it must do the job, maybe with a shorter lifespan than higher-end devices, what was OK. So I daisy-chained my two splitters to the console using their Thru port and terminated the line, then I plugged my 12 DMX lines into the splitters' outputs. I then tried to discover the devices on my DMX network and everything went sideways.

 

After several tests and a discussion with people from Highlite (manufacturer of Showtec devices), it seems that de device is not a "smart device", meaning that it only copies the signal back and forth on the wires without paying attention to DMX/RDM timing, what leads to collisions and unreliable signal. Maybe it was obvious given the very low price tag on the devices, but still I find it unbelievable to sell a device that will not work for the purpose it is supposed to serve.

 

Anyways, now that I completely the trust I once had in the documentation of lighting devices, I'd like to know if someone has experience with DMX/RDM splitters that work and do not cost an arm in order to avoid buying other bad devices. All advice is welcome!

 

Thanks

Edited April 22, 2021 by jeiw

[Tomo]

How many actual devices do you have, and is it feasible to rearrange them into a pair of daisychains by adding a few link cables?

[kgallen]

Is it feasible to return your two Showtec splitters as not fit for purpose and buy one Zero88 Spliiter8 and daisy chain a couple of your existing chains (per Toni)?

[jeiw]

How many actual devices do you have, and is it feasible to rearrange them into a pair of daisychains by adding a few link cables?

 

I have 24 RDM devices, plus one non-RDM 12-channel dimmer. Technically it would be feasible to link all my ceiling DMX lines together (although highly impractical given the fixed nature of the rig), and to link the floor lines together. But as I'd prefer to have the dimmer on a separate line, this is still too much for the two outputs of my FLX console. So I do not think I can avoid using a splitter.

 

Is it feasible to return your two Showtec splitters as not fit for purpose and buy one Zero88 Spliiter8 and daisy chain a couple of your existing chains (per Toni)?

 

I'll definitely try to return the Showtecs.

 

The Splitter 8 seems great, but also quite expensive. As reference I got my splitters for about 100 pounds each. I guess I could convince the board of my theatre to scrape enough money in order to invest 3 times as much for at least 12 working splitter outputs.

 

I've listed some references in that price range found on the internet, but I have no idea wether these devices work properly or not :

• https://www.thomannmusic.ch/botex_dmx_splitter_dd_6_rdm.htm
• https://www.thomannmusic.ch/stairville_dmx_splitter_6_rdm.htm
• https://www.thomannmusic.ch/showtec_booster_pro_2_8_dmx_rdm_5_pin.htm
• https://www.thomannmusic.ch/major_dmx_booster_1in12_xlr3.htm

Does anyone have (good) experience with one of those devices, or another suggestion of a suitable device?

[sandall]

No practical experience of RDM, but I did notice that the Showtec 2-8 claims to have adjustable DMX timing & opto-isolated outputs. Maybe worth giving Highlite another call.

[alistermorton]

I have 24 RDM devices, plus one non-RDM 12-channel dimmer. Technically it would be feasible to link all my ceiling DMX lines together (although highly impractical given the fixed nature of the rig), and to link the floor lines together. But as I'd prefer to have the dimmer on a separate line, this is still too much for the two outputs of my FLX console. So I do not think I can avoid using a splitter.

 

This is the bit I don't understand really - if you can run a DMX line to each fixture from a splitter, is it not possible to run a DMX line to the first fixture and then daisy chain DMX from fixture to fixture? Or is the rig very sparse, needing long, awkward runs of DMX cable?

 

If the rig is fixed, you're not going to be regularly plugging and unplugging the line, and if they all came off a splitter before, then they're all on the same universe I guess. This just needs one DMX line, using just one output of the FLX, the other output can go directly to the non RDM dimmer rack. So although a splitter is nice, and arguably good practice, it's not essential, here.

 

 

 

[jeiw]

No practical experience of RDM, but I did notice that the Showtec 2-8 claims to have adjustable DMX timing & opto-isolated outputs. Maybe worth giving Highlite another call.

 

Thanks for the advice. I'll probably go this way, but I hope I can find some user feedback on that product first to convince myself that it will work.

 

 

I have 24 RDM devices, plus one non-RDM 12-channel dimmer. Technically it would be feasible to link all my ceiling DMX lines together (although highly impractical given the fixed nature of the rig), and to link the floor lines together. But as I'd prefer to have the dimmer on a separate line, this is still too much for the two outputs of my FLX console. So I do not think I can avoid using a splitter.

 

This is the bit I don't understand really - if you can run a DMX line to each fixture from a splitter, is it not possible to run a DMX line to the first fixture and then daisy chain DMX from fixture to fixture? Or is the rig very sparse, needing long, awkward runs of DMX cable?

 

If the rig is fixed, you're not going to be regularly plugging and unplugging the line, and if they all came off a splitter before, then they're all on the same universe I guess. This just needs one DMX line, using just one output of the FLX, the other output can go directly to the non RDM dimmer rack. So although a splitter is nice, and arguably good practice, it's not essential, here.

 

Thank you for your time spent thinking about my problem!

 

I probably wasn't clear enough (sorry, my mother tongue is french and my english is a bit rusty). To clarify : my rig is constituted of 10 tubes that run across the room above the stage and the tiers. Every tube is equipped with a DMX cable that runs through walls to the control room where the console and the splitters are located. The remaining two lines run from the control room to the stage. Working with only one daisy-chain would not only be impractical but also force me to recable the entire thing or do some dirty stuff like using inverter cables to alternatively plug together cable ends in the control room and between two tubes. Maybe the whole thing was poorly designed, but I guess I now am stuck with it...

Edited April 23, 2021 by jeiw

[Don Allen]

But having a separate DMX line to each lighting bar can be a good design choice. If a budget LED PAR goes faulty and decides it want to be a master and output DMX onto the DMX lead, it will only affect the devices on that chain or bar.

[Fleeting]

Hi,

Once your rig is patched and working would you really need to soft patch it again? RDM is great, but you can always guarantee that one fitting won’t be compatible. I’ve had issues with a chilli rack running a old version of RDM. Every time the desk(flxs48) was turned on It found the dimmers and decided to re-patch them 24channels higher. Took a while to work that one out. If you have a look at the Artistic licence range. Have used them in the past with great success. Nice guys to deal with.

My go to DMX splitter is the Luminex Lumisplit 2:10, but get the feeling this will be out of your price range

 

Regards

 

Ian..

[DrV]

"Pathway Connectivity - 1009 DMX/RDM Splitter" https://www.pathwayconnect.com/index.php/products/DMX-distribution/142-1009-DMX-rdm-splitter is a four way device but again is probably too expensive for you. I have no experience of this particular unit but wouldn't expect any problems with their kit.

[dje]

As an alternative take on this (on account of RDM stuff being typically quite expensive).

 

How about you stick with the Showtecs.

 

Then in the event you need to reconfigure something over RDM, go in the patch room, plus a DMXCat into the DMX line running direct to the bar, change your config, and plug it back in the splitter?

[alistermorton]

But having a separate DMX line to each lighting bar can be a good design choice. If a budget LED PAR goes faulty and decides it want to be a master and output DMX onto the DMX lead, it will only affect the devices on that chain or bar.

Indeed so, which is why I said having a splitter was arguably a good thing.

[DrV]

As an alternative take on this (on account of RDM stuff being typically quite expensive).

 

How about you stick with the Showtecs.

 

Then in the event you need to reconfigure something over RDM, go in the patch room, plus a DMXCat into the DMX line running direct to the bar, change your config, and plug it back in the splitter?

This is a great solution if you want RDM capability only for configuration purposes, which is what the OP stated at #1. It also adds a diagnostic tool to the box in case of any problems with the rig further down the line.

[indyld]

I assume that you and Highlite tested this by not using the THRU but instead connected the second splitter to an output of the first splitter? Also, did you try just using a single splitter and this also didn't work properly during polling?

 

There is usually very little that is 'smart' about a DMX thru connection, it's just connected to the back of the IN. At least a proper output is re-timed - although a second splitter is re-timed. A lot of 'RDM compatible' kit on the market is so called just because it doesn't block the return signal, rather than because it has some magic sauce inside it.

 

Common practice with RDM rigs is that the RDM is off 95% of the time. This means that there is no need for it for the majority the time using the rig and any RDM admin that needs doing can be done in different ways such as direct connection of a single line or a single splitter. The thing that isn't clear to me in this case is, if the rig is fixed and accessing it is difficult, what regular RDM admin do you even need to do? The rig doesn't change, the controller doesn't change, presumably you don't just re-address or re-mode stuff for the sake of it. On the face of it, it's not obvious what this 'RDM always on, all connected, all the time' need is for?

Edited April 24, 2021 by indyld

[jeiw]

Thank you all for your suggestions, really helpful. Also thanks for the device references, I did not know most of those brands, this gives me more options.

 

As an alternative take on this (on account of RDM stuff being typically quite expensive).

 

How about you stick with the Showtecs.

 

Then in the event you need to reconfigure something over RDM, go in the patch room, plus a DMXCat into the DMX line running direct to the bar, change your config, and plug it back in the splitter?

 

Sadly I do not have a DMXCat (seems like a great tool, I'll put it on my wish list for my theatre's next budgets). I tried to do something similar directly with my FLX console, with no success until now.

 

I assume that you and Highlite tested this by not using the THRU but instead connected the second splitter to an output of the first splitter? Also, did you try just using a single splitter and this also didn't work properly during polling?

 

Actually no, my tests were made with the second splitter connected to the thru port of the first one (I thought that an already re-timed signal shouldn't need be re-timed again, and that on the contrary it might add more delays that could throw the whole communication out of specification). But I do not think this really matters in my case as I also tested using a single splitter and observed the same problem.

 

The thing that isn't clear to me in this case is, if the rig is fixed and accessing it is difficult, what regular RDM admin do you even need to do? The rig doesn't change, the controller doesn't change, presumably you don't just re-address or re-mode stuff for the sake of it. On the face of it, it's not obvious what this 'RDM always on, all connected, all the time' need is for?

 

 

Sorry, I guess I did not give enough context, and my approximative english did probably not help. By "fixed rig" I meant that I have a permanent structure (aluminium tubes equipped with power sockets and DMX lines) right under the ceiling that cannot be lifted up and down with hoists. But the fixtures on this rig do regularly get new positioning and lighting function, depending on the show. Additionally, between two shows the venue can be rented. So after each show a default fixture implantation must be restored, with fixtures set to a mode with a minimum of DMX channels in order to be easily controlled by a small manual console whe have for that purpose (the FLX is too complex and also expensive to leave in the hands of inexperienced users). And although we have a lot of identical fixtures (ETC S4 LED), whe use them with several optic blocs depending on the needs of a particular show (fresnel, cyclo, wide and narrow zooms) so it is likely that it is not always the same light engines that will be used at the same position for that default stage lighting. For all those reasons being able to reconfigure devices through RDM seemed useful to me.

 

As for the "always on" part, this comes from the RDM implementation on the Zero88 FLX console (called "RigSync"). The idea is that the console constantly monitors the rig and either adapts the patch according to changes made on the fixtures, or automatically reverts those changes if you do not want modifications made on the fixtures. On the console itself one can of course edit fixture mode and adressing. I've just started to use RDM, so the idea of Zero88 seemed quite clever to me, but now I see that if the whole rig is not fully RDM compliant this approach might not work at all. Of course the FLX has an option to disable RigSync, but then there is no RDM functionality at all.

 

I think I'll invest some more time to deeply understand RigSync and see if I can for instance connect the FLX to a single DMX line when I need to make changes to the fixtures' addressing or personality, enable RigSync and do the changes, then disable it and reconnect the whole thing to the splitter again. Maybe using one output of the FLX without RDM for normal operation, and the other with RDM for configuration purposes. If not, I guess I'll go buy a DMXCat

Edited April 25, 2021 by jeiw