why go against REL setup recommendation?

Generally speaking, I find it interesting when people say the subwoofer "sounds better" here or there. A properly integrated subwoofer for 2 channel audio is sonically invisible. It should not call attention to itself.

The specific recommendation is in the corner behind one of the main speakers. I suppose if your speakers are out in the room, or part way along the longer wall, then the sub placement may change also.

A lot of REL's market is outside the US, and mostly only us American have these large dedicated media / listening rooms. The III series REL's are very adjustable. You should be able to adjust the sub to the chosen placement in most cases, instead of adjusting the sub by moving the placement.

Many folks have only one place for the sub in a multi-purpose room, or those with WAF placement issues.

My experience was that the sub sounded terrible in the corner, no matter how it was adjusted. Since I have a 8x10 listening room (spare bedroom) I really would have liked it to be in the corner, but now I choose to step around it ... it's really in the way, but it sounds fabulous. If I had to run it in the corner I would have sold it ... it was really that bad. I would buy with an option to return if I was not sure that I could get away with placing in the middle of the room.

There's no one right place for a sub, but I have found that subs are even more finicky than the mains in terms of placement, to the point that if they're not placed correctly you're better off without one. Bear in mind when deciding to buy one, especially an expensive one.

Once I get a subwoofer properly integrated for 2 channel audio it will actually sound good placed almost anywhere in the room, simply because I can't listen to the just the subwoofer. It is blended perfectly into the music. It does not call attention to itself one single bit.

I can only "hear it" when I forget to turn it on, and start to wonder why the music sounds a little flat today.

This was Richard E. Lord's (aka REL) goal in designing the ST series. If you like to listen to bass, I agree, save your money and get a cheaper REL Q Series sub, which is a more typical subwoofer design, but still very musical in its own right. Or choose another brand.

I have a REL sub and it did not work in the corner of my room- boomy wobbly bass. Ultimately, the sub worked best when it was placed on the same plane as the speakers.

I agree with the above post on not having enough sub for the room and using corner placement as a substitute is not a good solution.

Once you have enough output, though, you will most likely get better bass using two good subs versus one really good sub. Most people do not understand that it is not always about output, but rather equalized sound pressure in the room. Yes, I've heard all the theories about bass not being directional, but to my ears stereo subs work better.

The Classic way of placing a Sub is on his Knees... just kidding.

Best way for me is placing the sub in my listening spot and crawling around the room, looking for the most clear and precise sub bass reproduction. That is where you place your Subwoofer.