Well...a DECtalk also weighs about 15 lbs and is packed with components. So it was probably a weight/quality tradeoff considering it needed to be mounted on a wheelchair.

I understand Hawkings last version use a Raspberry PI, with the original voice.

I think the unit was more or less the shape/size of a VT-240. Is that right?

It's heavier as noted, but yeah that's a pretty good description.

I was a kid when I saw one, in Brazil, at a computer convention. It was, probably "Feira Internacional de Informática" in Brazil, in the early 1980s. The DEC team was incredibly friendly, even to two kids (I went there with a cousin) who would, maybe, be their customers, 20 years later.

I became one. My cousin followed another career.