Hi Robert,

I've just had a look at mine and the top of the speaker cabinet measures front to back, 23.5cm (0.235m).

Just in case you later require dimensions for the bottom, the measurement front to back is 31cm (0.31m).

Apologies for only getting this info to you this evening. I'm afraid I don't get to visit the forum very often nowadays. 

Hoping this is of some help to you.

Cheers,

Si