Can anyone explain cable risers?

Nonoise,
I agree with your statement concerning the effect of synthetic carpet. When my cables are lifted off that surface there`s an improvement in clarity,or as you say less smearing. The change is subtle but consistent.I can`t comment on other flooring materials.
Regards,

There is a firm, scientific basis for raising cables off of the carpet changing the way that electrons flow through them. The carpet actually acts as part of the dielectric covering the conductors:

http://en.wikipedia.org/wiki/Dielectric

Taking the cables out of contact with the dielectric of the carpet will hence change the electron flow and fields within the cable.

Of course, the audibility of all this is up for discussion. Personally, my life is too short. But I would never dismiss the idea.

I use plastic-pipe couplers.

http://i89.photobucket.com/albums/k220/jeffreybehr/Room/12Sep2012_frontfloorcable_1200h.jpg

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http://s89.photobucket.com/albums/k220/jeffreybehr/Room/?action=view¤t=12Sep2012_frontfloorcable_1200h.jpg
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Tried some home-made ones. Couldn't tell the difference with or without. Try it yourself. You'll never know...