I wanted to share some anecdotal evidence as something quite interesting happened in my theater recently that's quite relevant to the subject at hand.
So I'm currenlty in the process of upgrading the overall acoustics and the sound quality of the theater and waiting on 4 funk subs on order as well as speaker upgrades.
I was never happy with the base produced by my B&W subs. My room was done by a professional acoustician that supposedly did big mastering rooms and yada yada.
But I never really "felt" the base as much as I expected and there were more other acoustical problems in the room that I was able to measure with REW and wasn't quite happy.
Long story short I brought another acoustician to look at the room and what he immediately pointed out was a "rookie mistake" where all of my front speakers/subs were placed on a wooden built pedestal.
This pedestal was quite heavy but not nearly as heavy as the speakers or the subs (each weighing at around 70-80 pounds).
What this meant in his words is that the speaker is not able to efficiently push air since some of the energy is being absorbed by vibrating the pedestal.
We did a quick test where we took the LR speakers and the 2 subs from behind the transparent screen and placed them on the floor.
This is how theater "debugging" looks like...
I have calibrated the system with Dirac after it to get the same frequency response as before. The waterfall chart - identical, FR - almost identical, SPL measrued - identical. RT60? identical.
But WHAT A HUGE FREAKING DIFFERENCE IN SOUND
I couldn't believe how much better both the speakers and the subs sounded when positioned on the floor...
In fact I'm now listening to a system with just the 2 subs and not 4 as I used to! The two back subs are disabled for the sake of testing as well as them being put on the equipment rack carpentry so I'm trying to avoid the same "vibration problem"
The mud in the sound is gone, the couch is going crazy and I can feel the close to "single digit" vibrations with low base drone slides.
So in both cases the subs are playing the same signal, the waves are measured the same SPL and same FR but the tactile response is VERY different.
In both cases these were the same sealed subs and the difference is staggering.
Note that the pedestal wasn't very high and in both cases there's Dirac EQ so the difference in FR is minimal (if any) so it can't be attributed to speakers being closer to the floor. Not the character of the sound and the transparancy.
This is why I think the actual shape of physical waves produced by the sub matters just as much for the resulting TR.
Maybe having a "sharper" and less compressed or smeared base means that you get more vibration just because of the nature of waves.
I will have to look into how to rebuild the front wall to accomodate this since I'm going with bigger subs and speakers too...
Super excited to hear how Funk Audio subs will sound since that's a whole different beast comparing to B&W.
I'm also looking into proper base trapping using diaphragmatic absorbtion that should further decrease "echo" in the base in the room and make it even sharper with less wave cancellations in MLP which should result in an even better TR (I hope).
Note that RT60 in this room is quite great - under 150-200ms for all frequencies. But still pre-Dirac FR has some dips and peaks in the response which means that there's phase cancellation happening due to the reflections of the base within the room. Using 4 subs makes the measurements much better but it does not minimize the reflections and the resulting "phase craze" that's happening. Only true base trap can clean up the base and restore the proper "impact", most say. So I'm looking forward to the difference this will make.