By Wilde Becker. Speaker Stands. At Wednesday, July 24th 2019, 02:05:04 AM.
If the output from the sub seems uneven, you need to try and find a location where it produces a less lumpy response. A good tip for doing this is to temporarily place the sub where you normally sit to mix, and then listen at different places around the edges of the room while playing back a same level chromatic (semitone) scale of sine waves from a sampler until you find the spot that produce the most consistent level across all notes.
All that unwanted movement can colour and distort the sound. We do our best to prevent vibrations by adding bracing to the cabinet, but that doesn’t really help with the movement.
One way to improve the situation is to add mass by means of a platform fixed to the top surface of the foam. Primacoustic do this in their Recoil Stabilizer by using a very thick steel slab with rubber matting on top, while Auralex and other companies use MDF topped with dense rubber on their more up–market platforms. IsoAcoustics take yet a different approach, by using a frame made from rigid components joined by resilient isolators.