Ever really thought about the connection between your speaker and floor.
It's highly possible that the reason you have not had success with your speakers is not necessarily the speakers fault but the way the speaker is interfaced with the rooms floor. Most speakers come with some type of stand or landing or spikes at the bottom (we gotten that far) but this is not enough to get a true interconnection between the energy in your speakers and the vibration in the floor. De-coupling is not the answer. There is no way to remove the sound of the floor but there is a way to tune the speaker to the floor.
People throw around words in this industry without thinking sometimes. Why would you for example want to decouple something from something else if the energy flow is going to end up going through that foundation anyway? Makes no sense to say I'm de-coupling a product from the floor. Your not removing the floor, at best your allowing the energy to dissipate into the floor in tune, but so much of the time the energy is entering the floor out of tune which makes the object being grounded out of tune.
I've been designing tunable speaker platforms for 25 years now and have only found 3 floors where the floor was actually in tune and the platform was not needed for the speaker. No ones perfect, but that means 99% of the floors out there with speakers sitting on them right now are causing the speaker and floor interconnection to be out of tune.
Big deal right, so it's out of tune a little. Out of tune a little as far as speakers go can mean decreasing the size of a soundstage dramatically, not allowing the drivers to co-exist in a cabinet or even change the dynamic range so much that whole parts of the perfromance sounds flat and lifeless.
When we took our platforms on tour in Nashville we set up one night at one of the rows popular night spots. The complaint was the bass was always muddy in the hall and almost not even there by the time you got to the back of the 135 foot long room. Sammy Kershaw's bass player assisted me as we put the bass amp on the platform, "sounds like a bass solo" was the comment of the house engineer afterword. We then put the other speaker components on theirs and the sound was "clear as a bell, I'm able to hear every note".
Speaker platforms are one of the biggest missing links in the high end audio industry today. There are huge tonal shifts that take place when a speaker is moved from the speaker designers facility to the end users home. Part of this is the acoustics but another is that the speakers are not able to form the same full range signatures designed into them. Many clients sit there disatisfied not realizing that the speaker is wanting to perform but not able to because an in-tune connection has not been made.
If your speaker is cold sounding, or the music is stuck in the speaker, or if you get a weird U shape stage in your room, or your sitting there saying "something is not quite right" one of the problems could be that your speakers are in need of a speaker platform.