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How shape/material of speaker footers impact their effectivness

Fitzcaraldo215

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125 Hz tone played through speaker
Lower curve is floor signal when speaker on spikes

osc2.gif



Same sine wave and speaker on soft feet - and the floor signal amplified x2 to even show something:

osc1.gif
Interesting, but not clear in terms of how the "floor signal" was measured or what the vertical scale is. Presumably, the test tone is as received by a mike, but how far away? No idea how the floor signal might have been measured simultaneously.

Personally, I would be interested in seeing overall response measured both ways by a normal omni mike at the far field listening position, not on the floor. Sure, the soft feet floor measure looks nicer, but does it produce a measurably different sound at our ears?

The test waveform speaker output is not obviously different between the two, though it might be slightly different. Hard to tell. But, the wavy peak/valley floor resonant behavior with spikes does not appear to be reflected in the output from the speaker. I suppose it is still possible that the induced floor "sound" and the direct speaker sound combine at our ears across the room.

Measurements are good. But, the real question to me is audibility to the listener. If the measurements from the listening position show nothing, I think audibility is highly unlikely. Even if measurements at the listener position show a difference, is the presence of the added floor sound audible or is it perceptably obscured by musical signal and other aspects of room acoustics?

Testing, as usual, might be tough. But, I continue to be inclined to believe that expensive, fancy spikes just ain't worth it in sonic terms.
 

Nightlord

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Interesting, but not clear in terms of how the "floor signal" was measured or what the vertical scale is. Presumably, the test tone is as received by a mike, but how far away? No idea how the floor signal might have been measured simultaneously.

Personally, I would be interested in seeing overall response measured both ways by a normal omni mike at the far field listening position, not on the floor. Sure, the soft feet floor measure looks nicer, but does it produce a measurably different sound at our ears?

The test waveform speaker output is not obviously different between the two, though it might be slightly different. Hard to tell. But, the wavy peak/valley floor resonant behavior with spikes does not appear to be reflected in the output from the speaker. I suppose it is still possible that the induced floor "sound" and the direct speaker sound combine at our ears across the room.

Measurements are good. But, the real question to me is audibility to the listener. If the measurements from the listening position show nothing, I think audibility is highly unlikely. Even if measurements at the listener position show a difference, is the presence of the added floor sound audible or is it perceptably obscured by musical signal and other aspects of room acoustics?

What the scale is isn't the important part, the important part is the absolute difference between the spikes-signal and the softfeet-signal (which is scaled to double height).

That the room plays along is normally quite easy to hear... especially when you make it stop doing so. You get a much tighter definition in the sound when the floor isn't adding a distorted sound to it.
 

Kal Rubinson

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We typically have wooden floors here. Especially in the main room which is typically where the speakers would be. Parquet, laminate or solid wood. Swedes leave the shoes by the door when entering.
Can I assume they are sprung or beam-supported and not on a cement foundation?
 

Kal Rubinson

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I don't have an idea, those measurements were done before I started with hifi even.
Those responses might be what I would expect from my CT listening room which has a hardwood plank floor over beams but I doubt it would represent my NYC room has hardwood over 2 feet of reinforced concrete. I have found that isolation strategies need to differ between the two sites.
 

fas42

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Apparently you can also get resonance of the driver, where the magnet assembly "bounces" on the compliance of the basket. Some designers advocate mounting the driver by its magnet, strongly braced to the enclosure, with a flexible foam seal between the front of the driver and the baffle.
The latter is a thought that I have toyed with, because it makes excellent sense to me ... but I haven't progressed to trying it yet.
 

fas42

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Those responses might be what I would expect from my CT listening room which has a hardwood plank floor over beams but I doubt it would represent my NYC room has hardwood over 2 feet of reinforced concrete. I have found that isolation strategies need to differ between the two sites.
Strategies would vary. In my first go at this sort of thing I had tremendous weight on spikes which directly contacted the concrete subloor - other homes had timber, so here it was Blu Tack to the floor, with extra weight on top. Carpet on timber is a problem, so here a high mass platform on the carpet, and Blu Tack to that platform. Overall, what has worked is strongly coupling the cabinet to mass which is much greater in comparison; the more extreme the ratio, the better.
 

March Audio

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OK, finally got round to it :) Lets look at some vibration on speaker baffles and the difference the stand fixing makes.

Unfortunately I cant get hold of my usual Bruel & Kjaer Pulse measurement system so I had to get creative. I do have a B&K 4533 accelerometer to hand but I had to build an ICP constant current power supply for it and then feed it into my usual TI PCM4222EVM ADC. Arta used to generate the FFTs.

Stuck the accel to a wine glass and gave it a flick just to test out. Now because ARTA is just doing an FFT (ref is dBV) we are not going to directly get any absolute engineering units out of the results, but I'm not worried about that as we just want to do comparisons of the different mounting methods. For the hardcore who want to work out the acceleration levels the TX sensitivity is 10mV/G.

I will follow up with the speaker measurements

20170420_122800.jpg
20170420_123322.jpg
20170422_131727.jpg
 
OP
C

cjf

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Cool...will you be taking requests? :)

Will this device be able to record/show the elapsed time it takes for the object being tested to stop ringing/resonating in addition to the Freq that caused it?
 

Blumlein 88

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OK, finally got round to it :) Lets look at some vibration on speaker baffles and the difference the stand fixing makes.

Unfortunately I cant get hold of my usual Bruel & Kjaer Pulse measurement system so I had to get creative. I do have a B&K 4533 accelerometer to hand but I had to build an ICP constant current power supply for it and then feed it into my usual TI PCM4222EVM ADC. Arta used to generate the FFTs.

Stuck the accel to a wine glass and gave it a flick just to test out. Now because ARTA is just doing an FFT (ref is dBV) we are not going to directly get any absolute engineering units out of the results, but I'm not worried about that as we just want to do comparisons of the different mounting methods. For the hardcore who want to work out the acceleration levels the TX sensitivity is 10mV/G.

I will follow up with the speaker measurements

View attachment 6075 View attachment 6076 View attachment 6077

Okay perfect. Now I think I can see the proper path for testing. Firstly you did the glass empty. Now you should do the glass full. Then empty the glass in the usual way. Then test again. Then give us the measured difference in sound vs wine consumed and determine if vibration or inebriation is more effective. :)
 

March Audio

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A few glasses of vino always improves the sound

1 glass = blacker blacks
2 glasses = veil lifted
3 glasses = any audiophile accessory (cable/anti vibration) can do anything you like based on principles observed in Dr. WHO.
 

iridium

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OK, finally got round to it :) Lets look at some vibration on speaker baffles and the difference the stand fixing makes.

Unfortunately I cant get hold of my usual Bruel & Kjaer Pulse measurement system so I had to get creative. I do have a B&K 4533 accelerometer to hand but I had to build an ICP constant current power supply for it and then feed it into my usual TI PCM4222EVM ADC. Arta used to generate the FFTs.

Stuck the accel to a wine glass and gave it a flick just to test out. Now because ARTA is just doing an FFT (ref is dBV) we are not going to directly get any absolute engineering units out of the results, but I'm not worried about that as we just want to do comparisons of the different mounting methods. For the hardcore who want to work out the acceleration levels the TX sensitivity is 10mV/G.

I will follow up with the speaker measurements

View attachment 6075 View attachment 6076 View attachment 6077

Is that globe-glass thing in front of the monitor a >brain vacuum tube<?

iridium
 

March Audio

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OK, found a few minutes to grab some measurements, pictures should show what I did with the setup.

I performed a bump test to get an idea of the speakers panel natural frequencies, plus a wide band stimulus with pink noise to see how it correlated.

This is with the speaker in my normal configuration. It has four small hard rubber sitcky pads underneath the base but is also bolted down to the stand top plate.

20170425_135914.jpg


20170414_163801.jpg


be718 bump test uniform.png


be718 pink noise kaiser high res.png


OK, so played tones at 100Hz and 5kHz in this configuration at about 85 dB(A)

be718 100hz.png


be718 5khz.png


Then inserted sorbothane squidgy feet underneath

be718 100hz sorb.png


be718 5khz sorb.png


Spot the difference.
 
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RayDunzl

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March Audio

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Sorry, but a bit time poor at the moment. Just a couplre of things. That is a measurement in one position only. The baffle will have a deflection shape, simply put vibrating differently across its surface. Look up you tube vids of sand on vibrating plates.

I will also try putting the speaker directly on a tiled/concrete floor, then on sorbothane pads as a comparison. Not much difference to see above.
 

RayDunzl

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cjf

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No No No.... Your using the wrong feet!

Veils will only be lifted if you use Stillpoints or similar high dollar options. Do you have any on hand?

Truth be told, I have no idea what you are attempting to show here but you do get an "A" for effort :)
 

Don Hills

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What he's attempting to show is how much vibration there is in the baffle plate of the speaker, comparing bolted to the stand versus "squidgy sorbothane feet". And the difference is 3/5ths of 5/8ths of sweet FA.
 
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