Subwoofer Footing - Connect or Isolate?

The last thing you want to do is put a subwoofer on springs. At some low frequency it will start shaking.

<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>

WRONG... Just wrong..

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>

Giant generators are isolated from the concrete pad they sit to control vibration that turns into LF hum that can penetrate an entire building and make it impossible to work.

<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>

I don’t know what constitutes "Giant" I’ve worked on Cats 1250kW mobile and stationary gen sets.

That same "Isolation Tech" Springs, Gummy Puffers and point of contact accumulators, keeps just about anything isolated, One from the Other.

12 to 15 tons of Generator can really put out LF harmonics. You couldn’t keep concrete UNDER it.
It would crumble it.. The engine perches would break, nothing would hold up. It has to be isolated.
They have used cancellation tech in machinery for a long time.. Joe Blow, human hearing application not so long.
30 years or so..

Regards

A REL engineer told me that the only thing I might want to try is some BlueTak under each foot. But with or without the ’Tak, he said the sub will perform properly on my hardwood floors over a crawl space using the T5 as REL designed it. I tried the BluTak, and in my room, but while I could discern no dramatic differences, I left it on the sub feet because, well, it’s just sooo sticky. :)

I suspect that REL knows how to build subwoofers a heckuva lot better than I do.

Knowing how to build subwoofers is of course a completely different subject.

oldhvymec is right. Springs are of course the best thing to put your speakers on. All speakers, sub or otherwise.

Yes the springs do need to be matched or tuned to the load. Duh. Too soft and the spring will fully compress and cease to be a spring. Too stiff and it will not compress at all and once again cease to be a spring.

In between these two extremes, where the spring is matched to the load so that it compresses about half way under load, this is where the load becomes an independently suspended mass.

This is a range, just as it is a range for cars. People with actual experience tuning suspensions will know the idea the spring being a function of the cars weight are nuts. They will have a hard time explaining why a 1200 lb F1 car uses springs 5X as stiff as a 4000lb sedan.

In cars or audio tuning matters. Read mahgister, he has tuned his by adjusting the weight and noticed a change with as little as 1/4 lb.

Another factor is damping. Fine tuning weight matters a lot more with undamped springs because the adjustment is really resonance tuning. Damping controls resonance making this sort of tuning much less important. It still matters, but damped springs like Pods have a very wide range of outstanding performance compared to ordinary springs.

The moving mass of even a large woofer cone and coil is only some tens of grams. The mass of all the rest of the sub is some 30 to 40 kg or roughly ten thousand times as much. For sure some acoustic energy is lost on springs. For sure if you know Newton, f=ma, it is infinitesimally small.

Again, note the difference between those who have done and those who talk as if they have done. Would be nice if all the people repeating nonsense about springs would include a statement to the effect they do not really know what they are talking about, because they have not tried.

Go and try it. Then get back to us.

Something else that is interesting about conventional VC drivers, they have a return spring sometimes TWO.

That which moves forward is pulled back and there is a dampening factor via the amp too, if it’s direct coupled.. Much like a shock that is used for dampening, more in one direction than the other. The exact reason for different bleed ratios between compression of the shock or the expansion of the shock.. AND then gas assist for speed.

Those shocks under your car or gas assist accumulator for the 200 lb rear door on soccer moms SUV. WORK to do different things..

But they sure work better than Fred Flintstones giddy up. Feet, A$$, and a little spotted hide. All the cushion Fred had.. Stone vacuum tubes, stone record player, Dodo bird for a stylus.. Thing change.. LOL

Innertubes work well, I’m telling you.. Now fill that innertube 1/2 way with water, I’ll bet you couldn’t stay in the room.. Water transfers LF pretty darn good.. Isn’t that the whole sonar thing.. It can be very destructive.

Air is fast enough. A more viscous material like different weights of oil would be slow enough. Both are very effective materials one for dampening one for isolation, BUT both in the same (for ease of application) flexible tube.

The initial shock, the air and tube take the brunt via expansion of the tube, then dampened by the oil. NOT amplified like a less viscous material would act..

It’s not rocket science but you do have to think a bit.. It’s right in there with the "Farmer Astronaut", HECK NO!... but a great example. Great movie. I’d forgotten about it.. I think I'll watch it...

Regards

Speakers and subwoofers like to be solidly mounted to add structure to the enclosure, they do not like to be in micro motion.
The ONLY reason you would ever want to iso mount a speaker or subwoofer is if the energy of the speaker is transfering into something such that it is audibly resonating, e.g. a suspended wood floor.
In that case you would introduce isolstion of some sort because not using it is worse than using isolation.
isolation is a compromise solution, the speaker is now in micromotion.   no isolation is always best if the speaker isnt causing something else to vibrate audibly.