You can do that with the HC-1, in fact I have. But keep in mind there are rails at the bottom of the HC-1 for its base that would look a little strange when used on its side. If that slightly odd appearance doesn't bother you, you can use the HC-1 speakers as vertical MTMs just fine. One thing you will want to do if you choose to do that is unscrew the horn of the HC-1 and rotate it 90 degrees. Since it is bisymmetrical, it is easy to do and only takes 5 minutes, but the way the horn is mounted is intended for good dispersion in a plane perpendicular to the way you would use it if you set it on its side.