Speaker Tilt Back benefits?

The idea is that tilting the speaker to the rear moves the tweeter a bit further from your ears, so their output (in theory) arrives at your ears at the same time as the output from the other drivers in the speaker. The tweeter cone has much less mass than the other drivers, so they propogate sound faster than mid-range or woofer drivers.

When sound waves arrive simultaneously at the listener's ear, it is referred to as time alignment (which is a feature of certain speaker designs such as Vandersteen). Time alignment, however, is also somewhat dependent on the distance from the speaker to the listener. Ideally, time aligned speakers should be at least 8-10 feet from the listener.

The idea is that tilting the speaker to the rear moves the tweeter a bit further from your ears, so their output (in theory) arrives at your ears at the same time as the output from the other drivers in the speaker.

because the tweeter isn't as deep as the rest of the drivers, and if they are all mounted on the front of the cabinet then the tweeter is actually a little closer than the other drivers.

All sound frequencies travel at the same speed. It is not true that

The tweeter cone has much less mass than the other drivers, so they propogate sound faster than mid-range or woofer drivers.

Tilting them back changes the relative position of your ears to the drivers. Also either takes or puts your ears on the drivers' combined axis. If you seem to be sitting too low or too high (for tonal response relative to the drivers) then tilting can help this.