Hanif, welcome to the forum. When you get a chance please post to the Mackoid roll call thread to tell us a bit about how you're using this wonderful machine. This is a small, but growing group of users, there is no OFFICIAL support here, so please be patient.

I haven't done it myself and don't own a D8B (i mix analog here).
I'd try setting the HDR to chase MTC and connecting the sequencer's mdid out to the hdr midi in as a starter.
Have you downloaded the techref from the HDR2496 website? SEE: http://www.mackie.com/hdr_web/downloads/HDR_TechrefB.pdf for the download.
Appendix D on P90 has a detailed description of syncing to MTC which I think is what your sequencer would output. The examples aren't specific, but if you haven't been through the techref, should help get you started.

Larry,

Would it be possible to spit mtc out of the HDR into the XP-60?

I'm certainly not the most qualified to comment on specifics of the HDR as I am not a user. But there are some basic principles I've picked up working with other machines that should work for HDR as well.

One principle is that you should use the highest resolution and most stable clocking available as your master. Anything that needs to slave to a lower resolution on the side (such as an external sequencer) won't suffer as a result. In my experience, MTC and beat clock definitely ain't the thing to use for syncing digital stuff. (I'm picturing a horse pushing a wagon instead of pulling it. Stop-go-stop-go instead of one steady stream of pull-pull-pull-pull. Don't know what that has to do with anything, but I thought I'd share that with you anyway.)

I see in the other thread you have an apogee sync card for the d8b. Use the apogee card as the master for all 3, make a tempo map on the HDR, and spit beat clock with SPP out for the XP-60. You should still be able to send MMC out of the XP-60, if you are used to working that way.

Regarding your difficulty getting everything to slave to the apogee card as you posted in the other thread, we'll need more info to make more specific suggestions. I'll start with a few general areas of question.

As Larry suggested, there may be some simple parameter hidden in plain sight. If I had $1,000 for every time I forgot to hit the "sync" switch on some piece of gear, the one that flashes bright red when it's active, right next to the play button... well... I'd be driving a little nicer car. :) How long are your wc cables? Are they the proper impedance, as specified by the manuals? Do you have to tell these units what sample rate they are supposed to be receiving, or do they all detect that automatically?

Hopefully we can help you resolve this problem quickly.