"Room shaking" is a wrong accusation received by low extension subs too many times. High fidelity infrasonic bass extension for music has nothing to do with room shaking. Perhaps, the ’room shaking’ notion comes from the extreme hometheater dudes who like to show off their platoon of 18inch ported subs hitting 120db+ every minute or something.
On the other hand, when hifi subs get down to infrasonic 10 hz levels like a couple of Rythmik F18s in one of my rooms (for example), you will experience/’feel’ something in music tracks (tracks you may have heard a thousand times) that otherwise will be fully denied to you. It’s hard to articulate color to the blind, but, once you hear/feel it integrated correctly, you won’t be able to unhear it/go back. There is always a volume knob that can be turned counterclockwise on infrasonic subs to prevent ’room shaking’ and continue to have a high fidelity experience. In fact and in most cases, it is phase integration errors that will make the room shake, and yet you can’t experience anything. If done right, one can be a hifi bass enthusiast without shaking any room, even if the sub got down to 10 hz.
On the same note, 10 hz to 20 hz is an entire 1 octave, 20 hz to 40 hz is another entire octave as far as human listening goes. For reference, 5000 to 10000 hz is also 1 octave. Perceptively, the 2 lowest octaves are also the foundation that upper octaves build up from. Why is some guy obsessed with a measly 5 or 10 hz more extension on the low end, one might think? that’s the reason...If a 35, 40 hz ’woofer’ posing as a ’subwoofer’ (missing a couple of octaves) is good enough, one doesn’t need to spend thousands of dollars on a true ’subwoofer’. A Verafi Caldera 10 priced at 200 dollars these days (a well designed musical ’woofer’) should do the job really well. OP could save himself a lot of cash.
Rythmiks are practical pricewise/sizewise for the performance they provide for most guys. On the other hand, here’s an extreme example..the sub got down to 3hz for 120k...but can it provide a hifi experience without shaking rooms? sure it can.
https://www.youtube.com/watch?v=8QOuobNCigU
Certainly these Rels not earth/room shaking but that’s not what I’m looking for. I want my subs to be invisible, simply be an extension of the main speakers, hese Rels fit the bill. Now, there is an added consideration with Rels using class a/b amps vs class D, T9x use a/b. I run mine on same dedicated circuit as main amps, this 10 AWG cryo’d Romex, 20amp, Oyaide R1 receptacles, and use quality power cords, no power conditioning. The only reason I bring this up is class a/b amps far less efficient than the typical class D amp you find in subs. This means quality of AC being fed to subs will likely have greater affect on sound quality vs class D subs. For best performance you need to supply plenty of current with the REL T9x or any class a/b sub , greater impact and articulation is the result. For those who’ve experienced wimpy sound from class a/b Rel or any a/b sub, AC not up to need. Keeping high level cable length short as possible helps, and the quality of that cable makes a difference. Using twisted multiple runs of Duelund tin plated copper litz wire to equal 13AWG, this so perfect haven’t experimented with others, I have VH Audio Airlock, a solid core wire ready to go if desired. This just to point out the high level cable used can make a difference. And all this not to say Rel a/b won’t work without all this tuning, plenty using sans this. I’m just pointing out these Rels have potential some may not be extracting.