Hi Marco,
You are correct that the pointed spikes are coupling your speakers to the floor and their vibration is causing negative effects such as directing unwanted vibration towards the equipment rack, your listening location, possibly to neighbors, etc. Much of the speaker's energy is being used to set your flexible floor in motion rather than is producing music. Not only is your bass response being compromised but much of the musical range is being affected as well. This is the case for all suspended wood floors and is a significant issue for many audiophiles. It is also an issue for concrete floors but not quite to the same degree.
The best method to deal with your issue would probably be more expensive than you have in mind but there are a few inexpensive solutions that will be helpful. If you mass load the floor under the speakers much of the floor's flexing will be minimized. Some other areas of the floor may also benefit from mass loading. You mentioned that you are on a loft so floor jacks under the joists is probably not an option. You should also decouple the speakers from the floor and from any massive supports (the exception would be a high mass support that is also highly absorptive). There are high quality and inexpensive compliant feet available that will accomplish this. You can contact any of the major audio suppliers for a specific recommendation.
Best Regards,
Barry Kohan
Disclaimer: I am a manufacturer of vibration control products.
You are correct that the pointed spikes are coupling your speakers to the floor and their vibration is causing negative effects such as directing unwanted vibration towards the equipment rack, your listening location, possibly to neighbors, etc. Much of the speaker's energy is being used to set your flexible floor in motion rather than is producing music. Not only is your bass response being compromised but much of the musical range is being affected as well. This is the case for all suspended wood floors and is a significant issue for many audiophiles. It is also an issue for concrete floors but not quite to the same degree.
The best method to deal with your issue would probably be more expensive than you have in mind but there are a few inexpensive solutions that will be helpful. If you mass load the floor under the speakers much of the floor's flexing will be minimized. Some other areas of the floor may also benefit from mass loading. You mentioned that you are on a loft so floor jacks under the joists is probably not an option. You should also decouple the speakers from the floor and from any massive supports (the exception would be a high mass support that is also highly absorptive). There are high quality and inexpensive compliant feet available that will accomplish this. You can contact any of the major audio suppliers for a specific recommendation.
Best Regards,
Barry Kohan
Disclaimer: I am a manufacturer of vibration control products.