Speakers on top of subwoofer

@soix  What exactly is the "design change' allowing the Wilsons to have the speaker on top of the sub cabinet?

Maybe as @steakster points out... Wilson uses The new V-Material, which is used where two parts of the cabinet come together, "behaves like a vibration absorber," according to Wilson.

You can add a world class 'vibration absorber' on the Harbeth/subwoofer also!  Vibration absorption is not exclusive to just Wilson audio. Easily measured also.

'the best place to put subs for optimal bass in a room is pretty much never where the speakers are placed'

Then, according to this statement, you can conclude that the Wilsons can "never" be correct. Since the speakers are always connected to the subs and according to you, they shouldn't be.

Another thought is that subwoofers and speakers are different sizes, so placing your speakers on top of your subwoofers might make them too high or too low for proper listening.

FWIW, I would never put my speakers on my Sub.😀

It's not optimal, but it's far from the worst thing you could do.  A bowl of water can help give you a visual impression of how much vibration is present on the top surface of your sub.  It may not be a lot.  You'll have plenty of options on how to decouple the sub from the Harbeth.  I would start with rubber/cork HVAC pads.  They are a few dollars at most hardware stores, or you could go audiophile approved expensive.

Mijostyn made a good suggestion.

@gdaddy1 

Good counter example.

Then, according to this statement, you can conclude that the Wilsons can "never" be correct. Since the speakers are always connected to the subs and according to you, they shouldn’t be.

@gdaddy1 No, and as with most things in audio it’s a compromise. While the designer gets to implement the crossover and there are some advantages of things like potentially better impulse response, it comes at the high price of having to design/build much heavier/more expensive cabinets and placing bass where it’s not optimal and most likely creates significant bass problems in a room. And in this particular case, which is what we’re really talking about here, where the OP already has subs it would be both silly and counterproductive to place them where they most likely will not sound best and cause room-induced bass issues. Plus, putting a speaker on a big, vibrating beast if not necessary is just a stupid idea — vibrations negatively affect sound, so adding significantly more vibrations into the speaker is just never a good idea, period. And on top of that and as someone else mentioned, it’s also likely the speakers will not be at the proper height plopped on top of a subwoofer, so for all these reasons it’s just an awful idea to put those excellent and expensive speakers on subwoofers.