Firing two flashes off camera

I have a 5Dmk4 and two Speedlites, a 580EXII and a 430EX. If I set the 430EX to Slave with the 580EX on camera, then the two flashes fire at the same time as expected, the 580 triggering the 430. If I take the 580 off camera and fire with a Calumet trigger, then the slave fires a fraction of a second after the 580. The setup apparently thinks it is a test shot where all flashes fire in sequence. Am I missing something, or is it not it possible to have the master and slave off camera with this setup?

Thanks.

Are you using a receiver on each speedlight, or just the one on the 580? I notice that Calumet's instructions tell you to use one receiver on each external light triggered. Using the 580 as a 'master' in this setup obv does not work because the 580 isn't communicating with the camera directly. The Calumet does not transmit TTL instructions (which is likely why the 580 is getting confused). Unfortunately, a 430EX (idiotically IMO) does not have optical slave function, which would probably function properly, but, to use this way would require an optical slave hotshoe trigger.

Hi Marcus, thanks for the reply.

Yep, that's probably it. I didn't think the 580 needed to be on the camera in order to trigger the 430 properly. The 580 can see the 430 as it does fire, just a split second too late. I shall just have to buy an extension cord for the 580 so that it can communicate with the camera.