I suppose you can be lucky and it works as you planned....but...if not? I would opt for predictable solutions! For more info: http://www.recording.org/ftopict-28648.html http://www.recording.org/ftopict-20719.html http://forum.studiotips.com/viewtopic.php?t=1586 Florian"my question wasn't answered... :-\ "
Drum riser: poor man's floating floor? *DONE! WITH PHOTO!*
Originally posted at johnlsayers.com, topic 3771.
thanks ..
I wish I could find again the link where they were saying that putting a tyre below a sub is a good way of decoupling the HP from the floor ...
great job! i'm gonna build one too, or maybe three for amps too.
i noticed an inconsistancy in the design plan. the liquid nails goes in between the two layers of mdf, right? not between the insulation and mdf?
thanks
Guys,
Do you think you would get the same/similar result glueing 4"x4" 1/2" 60duro rubber pucks to the bottom of the first layer of MDF rather than using rockwool or rigid fiberglass?
If my riser was 6'x8' how many do you think I would need?. one every 2 foot square? less/more?
The benefit would be a small saving on headroom.
I brought some for a floated floor that didn't happen!!
JohnG
See my EPDM Compression Test Data which I paid a machine shop to do for me (back in the days that I was planning to float a floor on the stuff). Ideally you want a loaded compression rate of about 10-15%.
It may not be exactly correct, since it may not be the same type of rubber you plan to use -- but you can at least ballpark it. Since it's just for a riser and not a floating room, the risk of being incorrect is a lot less disasterous!!
--Keith
Hi Keith,
If I do the rough sums with your data I will only need to use one 4"x4"x1/2" puck for the whole riser which of course will not work.
My sums are:
materials, drums, person = approx 350-450pounds
your compression test on one 3 1/2" x 1 1/2" x 1/2" rubber = average of about 500pounds for 10% compression
so what gives, or am I doing the sums wrong somehow.
I will need at least one puck every square foot or so to actually make the platform stable but according to your tests and my sums this will be about 600o%!! overkill that will defeat the purpose of doing it as the rubbers compression is the key to the riser actually working.
I suppose my question is roughly what size do I need to cut each puck of 1/2" 60duro rubber too so I can use more pucks to make a stable riser and still get the desired rubber compression.
Bet there's not many replies to that one!!
JG
I hadn't done the math, John, but I feared that would be the case for you.
60 duro rubber is pretty darned hard, as the data shows. In order to allow for more pads for less weight, you need a softer rubber, or smaller pads, or both.
Bear in mind that if you cut a puck in half, you will probably be able to apply more than twice the weight to it. That's because of the nature of this elastomer -- it spreads out in its deflection. The smaller the puck, the greater the "edge surface to face surface" ratio (I'm sure there's a technical term for that, but I don't have enough -- meaning any -- letters after my name to know what that would be), and thus the more it deflects under the same weight proportion.
--Keith
No problem Keith,
I think what I will do is cut them into 25mm x 25mm x 12mm (1x1x1/2) cubes, start with 2 foot square placement and then add or subtract as required before I glue them down.
Gotta finsh the room first!! - starting ti get ahead of myself!!
JohnG
Couple of problems I see with using rubber for something this small/light - one you've already mentioned, getting the pucks small enough to be able to use enough for stable support. Two, with the possible exception of Butyl and Sylomer, the damping of rubbers such as neoprene and EPDM isn't very good at all - so without some sort of damping in the form of insulation "caressing" ALL the MDF or other flooring, you will very likely get more ringing/boom than you bargained for.
Since this means that you would need to use insulation ANYWAY, it just seems easier to throw down a 2" thick chunk of mineral wool and lay your double thickness (offset seams) of MDF on top. You've already heard from the thread originators that this works well both for isolation AND for sound quality... Steve
Point taken Steve,
Just trying to find a use for $100 worth of rubber pucks I brought when I thought floating a floor was my thing!!
JohnG
As taught by Eric D: it's the shape factor.The smaller the puck, the greater the "edge surface to face surface" ratio (I'm sure there's a technical term for that, but I don't have enough -- meaning any -- letters after my name to know what that would be
Ha -- I'm happy just to be able to paraphrase that genius correctly! 8) Thanks, Florian!
Hi !
Finally I am going to do the Steve solution ! (yes I am slow ;-)
Got one question about density of the rockwool :
Can you tell me if the 2,5 PCF = 48 kg/m3 or 60 kg/m3 ?
And other question : dont you got rockwool "in the air" at each drummer kick ? little afraid about laying rockwool with "no protection" ....
thanks for any response :wink:
If you're doing this freestanding in a room - just build a simple 2x frame flush to sit on the floor that's with the top of the riser - make it 3/4" larger (in both directions) than the riser - then just set this so you have a neat 3/8" clearance all around the riser - attach to the existing floor with angle clips - and use backer rod and caulk to finish the edge seal. Neat clean edge finish - doesn't stop free movement of the riser itself - and solves your concerns about kicking fibers in the air........... BTW - just for reference - 3pcf 703 (or equivilent) rigid fiberglass is acceptable from a bearing point of view with the rockwool if it's more readily available to you. Sincerely, RodHi ! Finally I am going to do the Steve solution ! (yes I am slow ;-) Got one question about density of the rockwool : Can you tell me if the 2,5 PCF = 48 kg/m3 or 60 kg/m3 ? And other question : dont you got rockwool "in the air" at each drummer kick ? little afraid about laying rockwool with "no protection" .... thanks for any response :wink:
hi rod
thanks for the quick response ! I plan to do the work friday so I want to be sure to command the right material
for me the prob is that I have plenty of choice between mineral wool with lot of different density ... it begins from 30 kg/m3 to 160 kg/m3 and I dont know what density corresponds to 3 PCF ???
thanks also for the idea of the frame around the riser .. but maybe I can do what is in the picture in this thread (make a trim that goes near the ground but that doesnt touch it ... should be enough ... it is not in a room, it is in my studio, so it doesnt have to be perfect clean but I dont want to inhale wool at every session ;-)
and also 4'' corresponds to 10 centimeters and I wanted better to use 8 cm, do you think I have to use 10 cm or 8 should be enough ? :?:
This link downloads a free (freeware) and rather good unit convertor. It's easy if you are used to think in metric units on sites dominated by American units to have something like this on your desktop: http://joshmadison.com/software/downloa ... ertExe4.10 You can find this typical conversion under the tab density. You can calculate both ways. 3 pcf = 3 pound/cubic feet = 3 pound/feet3 = 3 lb/ft3 = 48 kg/m3 There are several manners of writing the same. PCF is normally not written in capitals (in as far as I know). 2.5 pcf = 40 kg/m3 1 pcf = +/- 16 kg/m3it begins from 30 kg/m3 to 160 kg/m3 and I dont know what density corresponds to 3 PCF ???
HUGE thanks to Eric !
Endly I have THE answer about that pcf thing !
so I have to find another product ... I was going to buy 60kg/m3 ... It wont do a "correct" ressort ? (in the mass-ressort-mass system)
or maybe I can use 8 cm of 60 kg/m3 instead of 10 cm of 48 kg/m3 ?
is the 4'' dimension a minimal one (for being in th 100 Hz area) or just an example ?
Looks like Steve was giving all these precious infos without having them tested in real ?
Density is one thing. One can have boards with higher density and still feeling softer than others with lower density.
It depends on brands and types of material.
The basic idea is: Whatever you use, you should have a deflection of ca 2.5 mm under static load (riser + drum + you). The lesser the deflection the worse your decoupling will become. With 2.5 to 3 mm you have a rather perfect decoupling (is relative of course) of your drums.
You also need enough cavity (> 2.5 cm better 5 cm) since the air also acts as a spring. If you acoustically close the edges then more than this 5 cm could be advisable (but it all depends of mass of this top floor).
Making a riser in itself as heavy as possible (top floor) will make it less sensitive to the difference in load, with and without musician, and the exact position of drums. The riser becomes more stable be making it heavier.
If you have mineral wool which is too stiff to obtain this 2.5 mm (or more) deflection you can solve that by cutting stripes of this mineral wool and use less than 100% coverage, as such that the total static load is carried by less mineral wool and as a result will deflect more.
I saw (I think here in the forum) someone using tennis balls to obtain the same effect (sounded as a good idea to me). You could use pucks, pieces of foam, whatever.
However you do it, try to get this 2.5 mm deflection under load, and if using pucks or tennis balls fill the empty parts with mineral wool or fibreglass (absorption in cavity), without that wool carrying load.
If you directly use mineral wool, that part is taken care of of course.
thanks for these infos
so you mean I need to have this 2,5 mm of "move" between riser without drums and drummer and riser with drums and drummer ?
I planned to add some piece of wood behind the drums in order to maintain a bit the sound ..
well I think that the only way now is to try !
if i dont have these 2,5mm reduction when I arrange the drums I should remove some material
thanks again for the advice !
In fact it's the deflection between the elastic (whatever) material without +/- anything and the loaded material. Hence the riser itself belongs to the load. Let's assume you use rockwool (but can be whatever). 1) put a nice cut piece of say 5 cm thick, 30 x 30 cm or 20 x 20 cm on a table. 2) put a thin piece of plywood on it. The deflection will be close to nothing and can be ignored. 3) Shift that to the edge of the table. 4) measure the thickness between plywood and table. 5) now find some means to put gradually more load on that plywood (books, weights, bucket or can you can fill with water or sand). 6) Check when that measured thickness diminished with +/- 2.5 mm. Check the weight you've put on it. 7) That weight is the target weight per surface unit the whole thing should be loaded with in order to work OK. Don't overload material. For rockwool should be somewhere around 5%, I assume for fibreglass you can go to 10%. For puck and neoprene as well 10%, for tennis balls that must be easily more. Note: this are all just rules of thumbs, no absolutes. You could also do it directly on real live things, but this experiment gives you the feel how stiff your material is allowing you to calculate in advance how much you need. Any other manner to obtain the same idea is OK as well. This whole story is based on the relationship between this deflection and the mass-spring resonance. The larger this deflection the lower this mass-spring resonance and the better your decoupling. This is based on the approximation (correct for linear bahavior): fo = 15.8/sqrt(d) d=(15.8/fo)^2 fo = resonance frequency d = deflection in mm For the USers fo = 3.13502/sqrt(d) d = (3.13502/fo)^2 fo = resonance frequency d = deflection in inches A lower resonance frequency will enhance TL and decoupling over the whole subsequent frequency range. Hence it's not just a matter of getting that resonance below the peak frequency of the kick drum. The more deflection the more that riser will feel elastic if you walk on it (loosing stability), and the more risk you run that asymetric load (musician, drum, empty) will degrade the principle. Therefore it's good if that riser staces in place that you make that top floor heavy and stiff (good pressure/load distribution), improving on all these side effects.so you mean I need to have this 2,5 mm of "move" between riser without drums and drummer and riser with drums and drummer ?
(1) if I put 8 cm
6) also 2,5mm ? or more ? proportionnal ... of what I think it should always be 2,5 mmm)
edit : sorry I re-re-read and I understand it has to be always 2,5 mm ...
thanks again !
Pulse,
2.5 mm or more.
The more the better, but without exceeding the maximum deformation allowed by the material.
The basic idea is the following:
You can press any fibreglass or Rockwool that hard that you compress it for more than 50%.
But then that material will not restore itself to it's original thickness after removing that load. Hence that material doesn't work as a spring anymore. You just damaged that material.
Therefor the lower you want to go in resonance frequency, which is a good thing, the higher your absolute deflection must be. But since that absolute deflection may not exceed a certain percentage of the initial material thickness in order not to degrade these material properties, your initial material thickness must become thicker when you want to have a higher absolute deflection.
Does this makes sense to you?
But in order to keep things simple for you:
If you use 50 mm material (mineral wool) and compress it that far that you have a deflection between 2.5 and 3 mm, you will have a better riser than most who didn't knew these relationships.
But since you don't seem to grasp yet the effect of the airspring and the mass of that top floor I should like to see heavy, play safe and use this 80 mm wool.
At Galaxy studios the control room bunkers, mounted on springs, where calculated to have a deflection between 27 and 28 mm. Don't aim to these values here, that has no sense at all. I just mention this to show that this 2.5 mm to 3 mm is no constant value, but it's a good target value for traditional risers as often discussed in forums like this.
thanks Eric !
You really know the thing ... impressionning !
So I will go with th 80 mm (100 mm seems not necessary)
will try to do a quick test as you mentionned
my riser will be quite charged as there will be the drummer and his drum and also a few wood panels ...
will post pictures when finished !
Rod this is a very neat solution, much better than affixing the outer frame to the riser, thanks for the idea !If you're doing this freestanding in a room - just build a simple 2x frame flush to sit on the floor that's with the top of the riser - make it 3/4" larger (in both directions) than the riser - then just set this so you have a neat 3/8" clearance all around the riser - attach to the existing floor with angle clips - and use backer rod and caulk to finish the edge seal. Neat clean edge finish - doesn't stop free movement of the riser itself - and solves your concerns about kicking fibers in the air...........