Placement of Single Subwoofer Affecting Sound of Main Speakers

The effect you may be having is that the sub is acting like a tuned bass trap, OR you are finding it’s reflecting a lot from the speakers.

Yes, either one must be true. Somehow any furniture in the room will affect the sound, especially things placed very close to the speakers. I tried placing a 2nd set of speakers just beside the main speakers in an attempt to run 2 pairs of speakers in the system. I hoped it would work but the sound was ruined. In the end only a pair of speaker can remain in the room.

Should ask what sub are you using and what speakers? Also consider using white noise and a sound meter ( app on smartphone) to get an idea of what is going on in regards to sub filling in lowest octave at your listening location smoothly.

The sub is a PMC TLE1 (dual 6.5" woofer, transmission line) and the speakers are Marten Duke 2. Will try the more advanced set up method you brought up sometime. At the meantime, using the ears will do it for me. I have a Radioshack SPL meter though.

The previously mentioned "crawl" method does have some credibility. Also the "swarm" setup may be the optimum option for using subs but since you are limited to only using a single sub that option is out.

Sub integration into any system/setup is one of the most challenging for audio/HT listening, A sub can offer so much enhancement to any system if done right. I have read MANY  posts since I once faced the same challenge. After reading about a lot of different scenarios people on this forum several times I have responded with a link that explains almost everything about subs. It's lengthy and quite technical bit if you look through the info you may find something that helps......

http://www.soundoctor.com/whitepapers/subs.htm

If you only have three (?) locations for the sub that "work" (WAF at work here?) but none of them really work, get rid of the sub unless you're willing to find the actual optimum position for the sub sonically.  Placement in the wrong position in the room can result in bass suck-out and a non-integrated sound that is worse than no sub.

One other possibility in those locations is to move the sub up off the floor a foot or two and see what happens.

Also, if you don’t have a room measuring system, try this:

if you have a tv in your listening room that can connect to your audio system and to YouTube you can run a frequency sweep video and listen from your seated position and you will hear the peaks and nulls. Then move your sub around and see what changes… hopefully the room isn’t too bad and you can improve things at the listening position with slight moves left right forward backward or up off the floor… and you might find the solution by moving the mains or even the seating position just a few inches as well.

Good Luck