Reposted from a earlier thread on audio isolation, I tried and use the Soundeck Constrained Layer Damping (CLD) squares under my loudspeaker:
The core problem that I had is that the loudspeakers sit on a suspended floor which has a large air volume beneath them which gets excited with a significant bass content in the music.
I am in the process of building some loudspeaker stands that are very similar to awkwardbydesign and have most of the parts but due to health reasons I have not put them all together. As an intermediate experiment I tried the Soundeck CLD squares:
https://soundeck.bigcartel.com/product/third-product
Between the pucks that the loudspeaker spikes go into and the laminate floor. As I would ideally like to use this approach (constrained layer damping (CLD) absorbs energy across a wide frequency range and does not re transmit the energy in a delayed form as the motion in the visco elastic glue dissipates it as heat) as the main sheet under the loudspeakers in my stands.
I measured (with the internal iPad accelerometer) and felt the vibration in the laminate floor (which acts as a big surface area to add bass distortion to the room) by the loudspeakers and at the listening position. With the CLD sheets in place the amount of energy transferred into the floor was reduced (both on the iPad accelerometer app and felt through my fingers). And it sounded clearer in the bass and had a clearer soundstage. Their measurements of vibration energy in and out suggests as a user we can expect up to 20 dB reduction in energy transfer.
Prior to all this I used tuned Helmholtz Resonators to reduce the effect of the main room resonant modes.
Provisos:
1. The iPad accelerometers are going to be narrow band (0 to 50 Hz, +/- 7.5g) and the display of the data is limited and it is difficult to say much from this other than the levels decreased.
2. I do not yet have a microphone to use to measure the sound at the listening position before and after the constrained layer damping squares were added. Also as it is a dynamic situation (vibration in the floor (distortion) takes time to build) I would need to think about the best way to compare and display the before and after measurements.