Nobsound springs - load range


I want to try out the Nobsound springs as damping footers (mainly under my mono blocks and my streamer). I ordered a first set of them and now I wonder about the amount of springs to put in for different weights of equipment.I remember one post that said it works best when 50% compressed (was it @millercarbon?).

I measured the compression of the springs, it takes ~2.5 kg per spring to compress it to 50%. Based on 50% compression target, this yields the following sweet spot configurations (only stable ones, total equipment weight):
- 3 units, 3 springs each: 22.5 kg
- 4 units, 3 springs each (or 3 units, 4 springs each): 30 kg - 4 units, 4 springs each: 40 kg
- 3 units, 6 springs each: 45 kg
- 3 units, 7 springs each: 52.5 kg
- 4 units, 6 springs each: 60 kg
- 4 units, 7 springs each: 70 kgLoad can be considerably higher than expected (somewhere I read about 36kg, which is presumably for 4 units).

Any comments?What about ~10 kg streamer, seems to be too light to compress the springs enough? Does anyone have experience with Nobsound springs under light equipment like this?
Based on your experiences: Would you even dare to put an 80kg floor standing speaker on Nobsound springs?
hm9001

Showing 8 responses by hm9001

Some thoughts based on my experience meanwhile. I have Nobsound springs under my Streamer/DAC, my heavy mono blocks (44 kg each) and my Powerfilter unit. My initial attempt with the DAC (~12.5 kg) was with 3 units with 3 springs each, as this was the least number of springs per unit that I thought was stable in itself. This results in a situation where the Nobsounds don't  compress much. The hearing result was intimidating: added sharpness, less resolution and less dynamics. 

I then tried to use less springs and ended up with 4 units with 1 spring per unit. At least for the 12kg DAC this is still stable enough. On one side (where the transformers sit), I have two springs. In total this results in a situation where all units are compressed about equally and about 50% (gap of the unit compared to uncompressed, by rough eyesight). The acoustic result is great and I kept the springs since then: Instruments appear to resonate more freely, there is more room, and bass apears to reach deeper. The number of springs corresponds nicely to the rule of thumb mentioned in the OP (2.5kg per spring). For me this is helpful to determine at least a starting point for finetuning by listening.

For the monoblocks, the result of adding the springs is very similar and synergetic to the DAC. Under the power filter, the effect is the least. I would not claim that it would withstand a blind test, but I kept the springs there for optical reasons.

I really like the ideas of dampening the springs with foam ear plugs and/or PTFE tape. I will definitely try (on my DAC first).

 

I don't have the Townshend pods, but I have the podiums under my heavy floorstanding speakers. They use pods on all four sides that are fixed to the podium and that have a knob to adjust the preload on the springs (in a certain range, there are different pod types for coarse load adjustment). With my speakers the Townshend podiums were a huge improvement, by some factor more than with the Nobsound springs under the components.

The Townshend pods are much enhanced, as they are also rather free in the horizontal directions (Nobsound is more or less stiff there), and the Pods are also dampened in a controlled way.

@ryder yes I have the aluminum Nobsounds. I just remeasured, the gap unloaded is ~14mm, the gap with 1 spring and 2.5kg load is ~7mm. Maybe the springs in your Nobsounds are different.

@musicaddict I try to put in some physics about spring mass systems (have to dig a little since this is long ago since I had to deal with that in my engineering study).

A spring extends or contracts in a linear relation with the force you are applying, or the other way round, the force F the spring excerts is proportional to the distance x that you are forcing the spring from its neutral (unloaded) position:

F = kx , where k is the spring constant. Your assumption that the force stays the same is wrong, the force gets higher the more you compress the spring. That is the reason why it settles in at a compression that depends on the mass you put on top.

From the formula above I can calculate k for my springs: k = F/x. Putting 2.5kg and 7mm gives me:  k = 3500 kg/s^2 (sorry for international units, but as continental European I cannot get used to imperial ;-)

Now let's calculate the resonance frequency, it is given by formula

f = 1/2Pi  sqrt(k/m), where m is the mass you put on the spring. You can see that for the same spring (or amount of springs), the frequency gets lower with higher mass. At the same time if you put two springs in parallel, you double the effective spring constant, and, with the same mass, increase the resonance frequency.

Putting the values for my DAC and spring configuration in the equation (mass ~3kg per spring), I get a resonance frequency of a little more than 5Hz, which is about what I would estimate when exciting the DAC and watching it swing.

Which resonance frequency does one want to get? The springs should decouple/isolate the component from its base, so that no vibrations are transmitted either way. The spring mass is a low pass system, it decouples above the resonance frequency, but kind of transmits vibrations below. What you want to avoid is transmitting vibrations for audio frequencies, so the resonance frequency should be below the audio band.

Thanks for the ideas for dampening the Nobsound springs, this works great. The PTFE tape (wrapped around each spring) did not have much effect in my case (However, I tried it only on my DAC).

The dampening with the ear plugs however does magic, the effect for the money can hardly be beaten (I used the ones from 3M, 30 pairs for 10 EUR). It had similar effects on my mono blocks and on my DAC (a little less). The effect (compared to undampened Nobsound springs) is: Foremost, I get a blacker background, there is more air around instruments. Bass gets clearer and more structured, and soundstage gets deeper. In total, music gets more emotional.

I also tried another tweak: Since the springs did make some audible noise when you compress them (metal of the spring scratching against the bore in the aluminum block), I lubricated the bores with PTFE spray. This improved the Nobsounds quite a bit further.

@ryder Guess what, I am now on 2 footers with 1 spring in each. 

Have you tried to stick with 3 units and put some weight on your DAC to reach the desired compression?

All the calculations are a waste of time.

I always get cautious when hearing such dogmatic statements. I would rather consider starting in the dark and doing erratic trial and error on all possible permutations of changes to different variables of a system a waste of time.

I prefer to have at least a basic understanding (or sometimes a hint or theory, e.g. 50% compression for the springs) of the variables and dependencies of a system and how they probably work. It is always good to derive a starting point and some hints/directions for experiments. This saves time in my opinion. And yes, the fine tuning and verification needs to be done by ear. The learnings should then be used to adapt the theory (maybe it's then 75% compression or even different compression for different components or something totally different). This can at least help others for their systems.

Only repeating statements like "the only way is by hearing" renders this forum useless.

@tweak1 Well, I started pulling springs out late yesterday with 3 springs/ 3 Nobs under the Oppo first (decent improvement).

The streamer/DAC I was talking about is also an Oppo105 (heavily modified: clock, improved XLR output stage, IEC inlet, LPS, fuse). The  best result I get with the Nobsounds is 4 units with 1 spring each, springs dampened with ear plugs and bores lubricated with PTFE spray. On the left side the springs are more compressed (as the transformers are on the left). Since I cannot further reduce the number of springs, I will maybe try with some weight on the right side.