Neoprene will work like Auralex MoPads?

that's true? how much thicker must it be? 15 mm is enought?

Have a look at this thread, http://www.recording.org/ftopict-20719.html Particularly the 15% bit by Eric Desart.

Hi z60611, My english is not quite well and I don't understand what that 15% exactly means. :oops: I have a pair of genelec 1029 on two vaulted hifi speaker. I think this is the worst position they must be because the resonance. weight is 6 kg one monitor (13,2 lb.) how much neoprene I need?

hello hugo, i'm certainly no expert, the guys will correct me if i went astray :D i attached an explaining picture also consider what they say about instability on the other thread. think about a steel plate.....

ok, I understand it now. thanks!

If you're looking for neoprene to substitute for MoPADs, you won't need it to be anywhere near as thick as the MoPADs. Look for (and I'm estimating) ~1/2" neoprene pads or sheet stock with a hardness of 40 durometer. If you can find neoprene "waffle" pads, they'll probably work even better. Also note that neoprene won't last forever like MoPADs will! :D

Hi dreamer, You should shift the action range of the speaker 50 % down and make it much shorter (that small black I shaped symbol you used). This deflection level becomes the equilibrium level around which the speaker vibration will oscillate. So say as a rough approach with 15% static deflection and depending on level of speaker reproduction, that the speaker will oscillate between -14.5% and -15.5% to much less (frequency dependent). In fact one normally will not see this displacement = very small, but can be calculated per frequency when all variables should be available. De largest oscillation range when you should visibly notice this displacement, means that you come in the neigborhood of the mass-spring resonance frequency, which by definition means that the design is badly wrong and that this resonant frequency is excited by the speaker and starts working as an amplifier in this range rather than a decoupler.

For Z specific: This relates also to my question marks (several months back) about this AVS DE comment related to the helical spring ceiling hangers, where this comment sounded as if this ceiling could start jump up (helical springs are linear) due to the large deflection. Such a ceiling will balance itself around the equilibrium and will show a hardly measurable displacement around this equilibrium.

As such the picture showing a working range between -0% and -15% is not correct. The picture is correct to show the static load deflection. With linear springs the upward and downward oscillation will be ca equal. Linear spring are things as helical steel springs and other springy material. I think the MoPADS will act about like that. Standard for synthetic and lots of other materials this will be asymmetric (non-linear springs). But for any practical use, just shift your symbol down assuming a symmetric oscillation (but make it much smaller or you're drafting a desaster design how things should NOT be). Added: I've seen the MoPADS foam (Jeff I think that's correct isn't it? I'm not mistaken here?) It indeed looks and feels as high quality material. Jeff reference to the waffled neoprene is based on the fact that materials as rubber, neoprene, EPDM etc. do NOT work on the compressibility but on deformation. The compressibility is that bad that you can't count on it for standard decoupling purposes. So they work by deforming their volume rather than diminishing/compressing the volume. This means that the shape and edge factor (for flat pieces the edge factor is defined by the ratio of the vertical edge surface versus the horizontal surface, read: size of piece) are mainly defining for the load they are designed for. For very lightweight objects this can become complicated since those pieces must become rather small (loosing lateral stability). Therefore such waffled or striped neoprene (or whatever) is designed to leave space next to this profile, for sideways deformation/expansion of this profile. This small profile one notices one the RSIC I decouplers is really functionally designed, to make the decoupler sensitive to low dynamic loads, while symultaniously integrating safety by higher loads (the body if the RSIC I itself) If one shouldn't allow neoprene or rubber to expand sideways (or wherever), as such counting on compressing (diminishing) the volume they just shouldn't or hardly work as decouplers (unless with extreme loads). MoPADs, Sylomer, glassfiber and the likes work mainly on compressibility of the material itself. Some of them are also more or less influenced by deformibility. The more solid the material the more this deformation factor will come into the picture.

Hi Eric, I'm sorry for the late reaction...haven't been around for a while. Thanks a lot for your input.

As such the picture showing a working range between -0% and -15% is not correct. The picture is correct to show the static load deflection.

The latter is what the pic was intended for...to answer hugos question. I extended the pic above according to your explenation. at least if I got it right, english is not my mother language. If I missed, please tell me. Thanks.

the dreamer wrote:

Hi Eric, I'm sorry for the late reaction...haven't been around for a while.

:wink: It's been a long while for me too. So I was surpriced I got an email referring to a message. :lol: That's indeed what's called: late response Don't worry, better late than never (as long within the same life time)

Reading the thread and had an IDEA! 15% deflection on some Dr Shoals. Probably will need to cut them in strips so the deflect unless your speakers weigh about as much as you do. Phil Abbate