I want a kitchen speaker and it needs to be fairly shallow like the Google Home Max.

I want the speaker to have good off-axis performance so that it sounds good whether I am sitting in front of it or standing at the cooker or work surface 60 degrees to the right.

I need real bass not the fake DSP tricks the GHM plays

If I want bass and good off axis then that means a 3 way speaker rather than a two way.

There are bass drivers like the Dayton Audio Epique 150HE that would work well in a two way but if I did that then I would need to cross the bass at something like 1.5khz or 2khz and at that freq the sub would be on the edge of 'beaming'. Also pulling any tweeter down to 1.5k is likely to lead to distortion.  So I think I need to cross the Epique lower say 1k and cross the tweeter higher at say 3k and that leaves a gap in the middle to fill with a mid range woofer. So 3 way..

I want it reasonably small. My previous speaker project was a subwoofer with internal volume of about 9.8 litres and it's too big for the counter top in the kitchen and that is before adding a tweeter and mid woofer to make a 3way.

So I'm aiming for an internal volume for the subwoofer enclosure of about 6 litre. A midrange can be isolated from the subwoofer in its own mini compartment of about 1 or 1.5l.

So maybe I can get by with 7.5l approx?

But a tang band W5-1138smf or Epique 159HE driver for the bass will make little sound in a sealed enclosure of 6l So I need to add some passive radiators or a port.

Having done some initial simulation then a pair of ND140-PR passive radiators would do if went with a TangBand W5.  

I know a little about the W5-1138smf as it was the driver I used in my previous subwoofer project which was a ported enclosure. However that was bigger than 6L and it was ported not passive radiator.

That previous project was 25cm external x25 x25 cube of 18mm MDF and the internal vol was 9.8l and it works well but is too big.

Coincidentally I also have a 20cm x 29cm x 20cm cube of MDF that I made for another subwoofer experiment that I never finished. This has an internal volume of 4.9l and is much closer to the small format I'm looking for.

So I've decided to use that existing box to see how the W5 will perform in 5l with a pair of ND140+PR - if it works out ok then I will size the bass chamber of my GHM killer speaker to be 5l. That would be  great because with the extra 1.5 l needed for the mid range means total vol would be something like 5l + 1.5l and 6.5 is only a bit bigger than the GHM 

So thats the driver and PR experiment needed to help size the box.

Meanwhile I need to figure out how to get smarts Into my speaker.

But that's for another day.