Hi

> It would be interesting to have a little 4" or 5" speaker built into
> the portable case...Doepfer doesn't make such a thing, do they I'd
> imagine it would be very easy to build. Any DIY'ers ever try this
> Do you think I would need a powered opamp stage, or is the audio
> output strong enough to power a low-wattage speaker on its own

The module sizes and also the powersupply-voltages are very common for
industrial modular technologies. I could imagine, there are active
speaker modules available for non music industrial systems, or e.g. for
intercoms or for audio distibution systems as used in hotels,
supermarkets or similar locations. May be this is a hint to search for
such a module.

Florian