I actually bought a couple of these for one of my theremin projects.
They are better than many other stands I have tried (on this project I used both stands for one theremin)
But IMO, Coalport is right - Mic stands wobble, they all wobble - these are better than most and dont wobble enough to bother me, but I ended up buying a loudspeaker support stand with tripod legs (and these arent without their problems) which was much more stable..
Alas, I got the last of these stands from Rapid Electronics, and they have been discontinued - they were robust and cheap - have looked for them from other sellers but they really have gone - the manufacturer is no more..
Having said all the above, I have seen many thereminists playing with mic-stand supported theremins, and I couldnt hear any wobble effects other than what one would expect even if the theremin was stood on a solid oak table ;-) - And some quite brilliant precision thereminists seem to manage with a wobble stand to perform without me being able to notice any wobble... So I really dont know who's right! ;-)
But as Coalport said, anything on a pole will bobble as a result of movement or instability at the base - So if one must stick your theremin on a pole, then the base and pole need to be as stable as possible.
Fred.
Just found this - never tried it, but its the same sort of price as the speaker stand I bought and doesnt have an awkward tripod..
http://www.studiospares.com/stands-speaker/studiospares-triangle-base-speaker-stand-single/invt/448870
I really suspect that speaker stands are better suited to theremins than mic stands.(or uplighters ;-) - my uplighters were re-assembled when I moved so that they became lights again, and my mic stands now support a laundry drying fixture - but my speaker stand has a theremin on it... and only wobbles if I bang it hard! ;-))
Tripod stands are probably the most stable IF the floor is absolutely level and even.
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Ignore the following - I leave it here just because I have some compulsion for long pointless postings! ;-)
One type of stand that is cheap and quite usable - probably about the same wobble factor as a reasonable mic stand but perhaps not quite as good as the ones above - is Ikea floor standing uplighter lamps - these have a heavy circular metal base and threaded steel sectional tubes.. Height is not adjustable except by fitting enough sections and cutting the tube for your required height - and one needs some DIY as they dont fit mic connectors - but I think they cost about £9.
I cannot find the exact model, but it was something like this:
http://www.ikea.com/gb/en/catalog/products/50139877/