Timwat, it has been my experience that isolation of a TT does more harm than good. Yes, it may isolate floor borne vibrations if it is done right, but alot of the problems are also airborne vibrations, so you are not eliminating vibrations even with a good isolation base. This may be good for a "partial" fix, but not total.
The problems introduced with most isolation designs is that they allow movement of the TT in one or more planes. The most destructive is the vertical plane. In my opinion and experience, the de-coupling of the TT in the vertical plane causes a reduction of bass and dynamics. This is generally why mass-loaded non-suspension TT's exhibit better bass weight than suspended ones. By using a flexible isolationlike an air bag or sorbothane, etc., you effectively transform the TT into a suspension TT, thereby losing some of the advantages and reasons for a mass-loaded design. In a suspension design, rigidity to the floor still is better there, because suspended designs are tuned to a particular resonant frequency which will be changed by a flexible isolation material, and possibly(likely) adversely affect the tuning of the suspension. Linn discovered this years ago, and recommended the Sound Organization lightweight rigid stand for their suspended TT's. And all mass-loaded designs have always been designed for additional mass loading to a heavy stand/base with high rigidity.
So, if you gain anything by way of isolating floor-borne vibrations, you lose other things by altering the design principles of your TT. This is not a good trade-off IMO. It is better to address the floor-borne vibration issues in the floor itself, by positioning the TT is an area of the floor that exhibits the best results regarding vibration transfer to the TT. The airborne vibrations can also be addressed this way, by locating the TT in a bass null. If you can find an area of the floor that has little floor-borne vibration characteristics, and also located in a bass null zone, you have an ideal location, and do not have to resort to measures that screw up one thing to solve another. This may sound difficult, but with a little experimentation, a suitable location can generally be found in any room.
If after all this consideration, you do not want to move your TT for decorative purposes or WAF or something, then be aware that you are losing something in the bargain. And you are still going to get airborne vibrations at higher volumes no matter what you use.
The problems introduced with most isolation designs is that they allow movement of the TT in one or more planes. The most destructive is the vertical plane. In my opinion and experience, the de-coupling of the TT in the vertical plane causes a reduction of bass and dynamics. This is generally why mass-loaded non-suspension TT's exhibit better bass weight than suspended ones. By using a flexible isolationlike an air bag or sorbothane, etc., you effectively transform the TT into a suspension TT, thereby losing some of the advantages and reasons for a mass-loaded design. In a suspension design, rigidity to the floor still is better there, because suspended designs are tuned to a particular resonant frequency which will be changed by a flexible isolation material, and possibly(likely) adversely affect the tuning of the suspension. Linn discovered this years ago, and recommended the Sound Organization lightweight rigid stand for their suspended TT's. And all mass-loaded designs have always been designed for additional mass loading to a heavy stand/base with high rigidity.
So, if you gain anything by way of isolating floor-borne vibrations, you lose other things by altering the design principles of your TT. This is not a good trade-off IMO. It is better to address the floor-borne vibration issues in the floor itself, by positioning the TT is an area of the floor that exhibits the best results regarding vibration transfer to the TT. The airborne vibrations can also be addressed this way, by locating the TT in a bass null. If you can find an area of the floor that has little floor-borne vibration characteristics, and also located in a bass null zone, you have an ideal location, and do not have to resort to measures that screw up one thing to solve another. This may sound difficult, but with a little experimentation, a suitable location can generally be found in any room.
If after all this consideration, you do not want to move your TT for decorative purposes or WAF or something, then be aware that you are losing something in the bargain. And you are still going to get airborne vibrations at higher volumes no matter what you use.