Awesome! Great tests and info! I love this stuff!
Wow that single 24" is way powerful even at 1 foot to 18" away!! And attached to the cone at 6hz!!
Originally Posted by coolrda
All of this shows just how capable VS/iPhone 7 is and the power a sub can generate. The question is how can we limit that loss and couple our tactile components to the seating more efficiently.
Great question and one I've thought about more than a few times!
As far as coupling the TR to the seating for the acoustical coupling, I think you nailed it with showing what it can do in the VS tests by moving the driver closer to the seat. IME, inches really can make a real big difference, especially a foot or so like your test shows with the one 24" as you moved it closer. Also form my experiments, its not just the TR/Shake that is has a big effect on, it's what you feel in your body as well, which I kind of think of a Slam. So for me, this means the closer I can get that driver the more TR and Slam I can get out of it.
Another question is would this be better/more efficient or just different feeling (effects the axis differently) with the driver behind you on the floor so it hits you on your lower back/butt area or up a little higher, OR like Scotts sub riser where the driver is right under your seat? I'm mainly talking sealed subs here, but would apply to ported as well, but will have the port position to take into consideration as well as the driver itself.
One thing I'd like to bring up or 'question', is how much difference does room gain effect TR compared to actual output from the driver without much room gain when it's positioned VNF right behind you or right underneath your seat? I wonder about this. Take a look at this info...
This VS was done almost a year ago on EOT with subs only (3 VNF's + FF), but probably looks pretty similar now even with a slightly different calibration. This is with a 5lb weight (bag of rice) at -10mv. For each 5 lbs you weight with, you loose about 10db difference on TR levels and it also effects the overall PSD TR slope across the board and around that 8-12hz and under like you were saying. But we can talk about that later. At -10mv with subs pretty flat with speakers or maybe a hair above, my TR on the PSD reading follows the EOT source pretty closely, not exact but still pretty close (slight dip at 15hz and 10hz could be a hair higher), meaning it climbs higher and higher as its steps from 30hz to 10hz (30, 25, 20, 15, 10).
Now with that shown, since I basically don't get any room gain in my nearly 10,000cuft huge room, my VNF sealed 18's have to be LS'd pretty good (LS 9) to get the low end picked up to where its pretty flat down to around 15hz or so before it starts falling off. So this is pretty much what my seating is getting like this close mic measurement:
Ok now then, how would this differ in TR on the PSD on EOT if I got enough room gain that I only needed maybe 1-2db of Low Shelf on the low end to get flat down to that same 12hz or so before it starts falling off? Is room gain as powerful for TR as the actual drivers output raised with an LS (or LLT ported that doesn't need an LS)? I'm thinking probably not because VNF can be so damn powerful, but I cant say for sure because I've never experienced it or tested it. I'll get to find out soon though I guess, as I'm in the process of moving all my gear upstairs to a small 1350 cuft room, but will also be on a suspended floor (which will add another variable and will have an effect on TR). Also I'm talking TR/Shake here, not room pressurization, which I think would most definitely go to the room with more room gain, which would also most likely be a smaller room vs the large with not as much room gain.
So if this is indeed the case and you can get more TR from the actual driver output VNF (LS'd to be flat with close mice measurement - basically what your seat is getting) vs not as much driver output (not LS'd so the low end tapers off on the sealed sub for close mic measurement) and the difference is made up with room gain, would a person with the room gain in a smaller room be able to go ahead and LS to a flat FR down low on the close mic measurement (again what your seats gets with the driver that close) + the room gain which will give you a pretty Hefty rising house curve down real low, be able to stand the pressure in your ears etc in a smaller dedicated room while getting the TR (or maybe even a little more) to match the EOT source track (or what ever the ULF source)? Make sense? Sorry for the mega run on sentence, I think I may have tried to cram to much of what I wanted to say in there LOL.
I know its still very early, but I was going to ask you about this with your latest EOT measurements with your VNF subs only and trying to get those last 15hz and 10hz raised a little more. Is your FR pretty flat at the MLP down to around 10hz? Did you have to use much of a Low Shelf to raise the low end FR on your sealed VNF's or is room gain helping you out quite a bit to get you there? How does a close mic FR read on one of your subs that you are using VNF behind your seat with your current current cal that you got your VS reading from? Just curious, as room gain vs what the driver is actually doing may be coming into play here. I'm sure seating has a big effect as well as room and other things.
If ear pressure does become a problem at this point by LSing down low + the room gain, then I'm sure the MA's will be even more important on the 10hz and under stuff (may require an army of them to match the 10hz and above TR) and may be one of the only other ways to attack the problem, besides maybe a suspended floor. I'm sure suspended floors have their problems to and can differ from one another, maybe a little ore quite drastically. One suspended floor might have a crazy 10hz and single digit resonate frequency while another might not or a little higher etc.
So I'm mainly referring to TR from around 30-50 down to around 8-10hz here with the VNF subs. IDK about the single digit stuff under about 8hz, I'm sure it gets way harder and harder to get that couch moving the lower you go with acoustical coupling to match the stuff above 10hz like you were saying, but I have no doubt the closer you can get the driver, the better the chance.
As far as mechanical coupling goes with the MA's or TT's, beside the usual tricks of having a good hard surface to push against for the MA's (bottom and top), having them in the best place on your seating (probably the rear of chair, but maybe not), and maybe a few other little things, IDK, at least for the singe digit stuff to read well with VS/iPhone like you shown it's able to do with your test directly on the cone. Like I mentioned up above, maybe just an army of them to allow you to EQ the crap of them under 10hz or so to get the readings up around the stuff over 10h-12hz.
So about the VS weighted vs no weight. I agree about how it effects the readings. Not only does each 5 lb bag of rice effect the TR reading by about 10db across the board (which is ok), it also effects from about 15-20hz and below quite a bit. With more weight, you get a little deeper extension readings but it also slopes off more from abut 20hz and lower (a lower reading) compared to the rest. So another words, a little flatter PSD response (unless you start getting much over 5 lbs where the 15-20hz and under starts to drop off or get smashed down even more) vs more of a gradual sloped downward PSD response across the board, which I think is what we are after (or maybe I should say the most accurate) from all the many different VS readings with white noise that folks have posted.
The problem with no weight on the devise as you all know, is the phone can loose contact with the seat. Maybe not such a big problem if you readings are down around 1e-04 or thereabouts, but you start getting up around 1e-03 to 1e-01 or higher, then its a problem - that phones is going to be catching some air off the seat cushion. I think if one is going to be taking these VS readings with no weight, you'll just have to find a way to secure the phone to eliminate the bounce (or a least real close to it). My last few reading I posted in this thread a couple months back I actually took with no weight and kind of preferred it. I think I still got a tiny bit of bounce up off the seat but not by much, at least on one end of the phone. The other end kind of tucked under the lip of the seat back barely, where the top of seat cushion meets the back of seat and therefore eliminated most of the overall bounce. Seemed to work great, but I'm sure a piece of artists tape or something would work even better and probably not mess with your seat surface at all when removed. Yes, PSD readings go up by about 10db and you loose a little extension under 10-12hz with no weight, but it doesn't start smashing it down under 15-20hz and under, while also giving a nicer gradual slope on the white noise files, which is what I think we should be after IMO with everything I've seen so far.
did you take these EOT measurements weighted with rice or no weight? Which do you prefer and what do you think we should all use? It would probably be best if we all start trying to use the same method, whether it's 5 lbs of rice, 2 lbs of rice, or no weight with the device secured with tape or something to eliminate the measuring device (iphone or whatever) from loosing contact with the seat surface and effect the accuracy.