Buchardt S400 Mk II vs Sony SSCS 5 in Bass

Sounds to me you have a low power amp problem. I have listen to the 400mrk 2 with my Pass integrated 250 and I could not tell if my Sub was on . The Buchardt have excellent bass. 

@dwest1023 

That could be it. I see Pass 250 renders 500 wpc into 4 ohm and S400 is rated a 4 ohm speaker. I had Parasound A23 and NC 2125 v2. Both are high current rated 225 wpc into 4 ohm but maybe still not powerful enough to push the woofer and radiator well. Wow. I thought with the 88 db/w/m sensitivity my amplifiers should be able to handle it well BUT I could be wrong for all this time... 

I wish I could afford Pass int. 250.  Do you other recommendations for that powerful amp. under, say, $2k-$3k that could do the trick?  My 45 days' trial is ending soon.

If you have a high current amp pushing 22wpc, you should have no problem driving the 400’s. It could be your placement of the speakers. Try moving them closer to your back wall. 

Maybe I was over reacted to the lesser wattage of my Parasound amp.  I wrote to Buchardt and they also mentioned the amp is a great one and should not be a  concern/issue.  They were saying S400 is a neutral speaker aiming for flat response.  The mid-bass is not boosted like most of the ported speaker (like Sony) so S400's bass might not be that strong as a comparison but it hits deeper notes for sure.  As you have suggested, they recommend to move the speaker closer to the wall even to the corner.  I did find the bass is essentuated but still prefer leaving its tweeter 3 ft away from either back or side walls to give the speaker space to breath.  I found also the soundstage depth suffers a bit when I move it closer.

Lastly, Buchardt suspects one of the speakers may not be airtight enough (which is important to being a closed-enclosure speaker) and asks me to do the airtight test.  The test goes like gently push in the passive radiator on the backside, and then noticing that the front woofer get pushed out and see how long time it takes for the front woofer to return to its default position. It should take 3-4 seconds, maybe a bit less.  I am going to test both speakers tonight.

@dwest1023  

I will appreciate if you could also perform the airtight / leak test as described above  on your S400, and let me know how long does it take the woofer or PR to get back to its normal position / equalization of internal pressure.  I have read somewhere that it will actually take longer time (say 6-8 seconds instead) to return to its default position.  Appreciated.