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How shape/material of speaker footers impact their effectivness

Blumlein 88

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I didn't read the entire thread so just jumping here. Hope it hasn't been covered.

Townshend's idea is a bit different than other people. They contend the speaker sends out bass notes, which come back to a speaker via the floor causing movement. Enough movement to equal the movement of tweeters which can smear or blur sound. So decoupling is to prevent this from occurring. They have this video to show what they have in mind. Also in some cases vibration from other sources can interfere with the speaker providing sound cleanly. My question would be if the amount of movement is enough to really make an audible difference.


There once were a couple in my opinion more effective videos showing the effect, but I can no longer find those. Their idea is rather like a TT suspension. Decouple by having a low resonant frequency of compliance and therefore block transmission of vibration to the speaker.

Certainly one can find information that ball and cup isolators can be effective in isolating a speaker from horizontal movement from the floor it sits upon. Is this enough to matter? Since we have some people who professionally work with vibration maybe they could comment effectively.

Also there have been people all along who claim suspending speakers by thin wire or string makes for better sound. That has not caught on which I think it never will for obvious reasons.

EDIT to ADD: I see Nightlord has already been speaking about some of the similar ideas. Essentially a damped low resonance spring under speakers. Some early footers were basically springs wrapped in rubber to damp the movement. Also some had the inside sealed so a small air leak could tune the damping somewhat.
 
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Blumlein 88

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Here is a picture of one of the Townshend Seismic load cells. Obviously a spring with some rubber material around it and metal end caps.

Townshend-Seismic-Isolation-load-cell.jpg
 

fas42

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Well, what I am buying is from a company that specializes in feet for speakers, either you go for the cheaper way and pick in a weight range, or you weigh your speakers front & back (or every corner if unsymmetrical) and tell them the weights and they pick out the right feet for you. They're called Sonic Design and resides in Stockholm, Sweden. How they source the material and what it is, is of little concern to me. That it works - is.
Fair enough. I see that they use the word "damping" repeatedly, which implies viscoelastic. Easy to test: apply pressure sufficient to make a strong indentation in the material, and watch how it reverts back to normal - if it takes significant time then you have viscoelasticity.

What I find interesting is that they disparage spikes, on their website! They "prove" that spikes cause problems - two approaches, which is right? They also don't like Blu Tack ...

What is 100% clear is that changing the mounting of a speaker alters the sound, in some direction. Personally, the locking into position with a stiff, sticky substance has always worked; it always gets me that much closer to "convincing" sound.
 

fas42

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I'm forever hearing subjective anecdotes about ' tighter bass' ' all boomyness has gone' ... that should show easily on a in room frequency response test..
Not necessarily. A chap up the road who uses DEQX to correct FR to an inch of its life, and who has massively heavy, sealed subwoofers to get the bass done right should have that under control; and on a FR sweep it all sounds in order, the drop to the lowest audible notes was very impressive - super clean, no anomalies, one of the better performers I've heard doing that test. But, on trialling a couple of my demo CDs, with "intense" bass, quite disappointing - the impact wasn't there ...
 

March Audio

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It may alter some of the bass response, but I'm interested in 'tight' bass, not wooly sound - the gains in reduction of distortion from the speaker cabinet being constrained to a much greater degree far outweigh any alteration of the nominal response curve.

Not might, it will. Wrong. You still refuse to accept yhe cabinet is vibrating regardless of how well your blutac fixes it to the stand.
 

March Audio

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I'm forever hearing subjective anecdotes about ' tighter bass' ' all boomyness has gone' ... that should show easily on a in room frequency response test..

Of course if it were that significant. Boominess is an acoustic issue, either the room modes or possibly a resonance being kicked off through coupling to something else like the floor.

If the speaker itself sounds boomy then it is one shit speaker that wont be saved by a bit of blutac. You can always play it in the garden to to check :)
 
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March Audio

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I didn't read the entire thread so just jumping here. Hope it hasn't been covered.

Townshend's idea is a bit different than other people. They contend the speaker sends out bass notes, which come back to a speaker via the floor causing movement. Enough movement to equal the movement of tweeters which can smear or blur sound. So decoupling is to prevent this from occurring. They have this video to show what they have in mind. Also in some cases vibration from other sources can interfere with the speaker providing sound cleanly. My question would be if the amount of movement is enough to really make an audible difference.


There once were a couple in my opinion more effective videos showing the effect, but I can no longer find those. Their idea is rather like a TT suspension. Decouple by having a low resonant frequency of compliance and therefore block transmission of vibration to the speaker.

Certainly one can find information that ball and cup isolators can be effective in isolating a speaker from horizontal movement from the floor it sits upon. Is this enough to matter? Since we have some people who professionally work with vibration maybe they could comment effectively.

Also there have been people all along who claim suspending speakers by thin wire or string makes for better sound. That has not caught on which I think it never will for obvious reasons.

EDIT to ADD: I see Nightlord has already been speaking about some of the similar ideas. Essentially a damped low resonance spring under speakers. Some early footers were basically springs wrapped in rubber to damp the movement. Also some had the inside sealed so a small air leak could tune the damping somewhat.

Yes this will isolate but as you mention is therecactually significant vibration coming back up from the floor? Got to remember the baffle is vibrating.
 

amirm

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Townshend's idea is a bit different than other people. They contend the speaker sends out bass notes, which come back to a speaker via the floor causing movement. Enough movement to equal the movement of tweeters which can smear or blur sound.
Such effects even if audible, will only be so in an anechoic chamber. In any real room there are so many delayed reflections that such effects are built into the sound we hear by orders of magnitude.

Such is also the case with phase delay where they can be audible with headphones and anechoic chambers but not in real rooms.
 

fas42

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Not might, it will. Wrong. You still refuse to accept yhe cabinet is vibrating regardless of how well your blutac fixes it to the stand.
That's not correct, I'm happy to say that the panels of the speaker will vibrate in sympathy with the impact of air movement within the cabinet - and the degree of that will vary with how much shaping, stiffness, bracing, damping the panels have. However, I have not addressed this to any significant degree with the speakers I've used up to now, because it has not been a major issue, for me. I suspect that if I want extreme clarity, at high playback levels, then it will become more important, but I haven't felt the need so far.

What I would be interested in, if you're going to do some experiments, is how much attenuation of panel vibration occurs if various means of mounting the speaker is tried: spikes vs. spongy discs vs. Blu Tack vs. nothing used, etc.
 
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cjf

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So you dont have any idea of the real world practical effect the different metals /their propagation speed in this specific application. Please note I was specifically referring to the three versions with different metals and not the compliant material they are bonded to.

In this instance I've not tried their other offerings so cant comment on how the other cup options function or sound compared to each other. The only data I can go on is via what is published online by those who have tested how sound/vibration travels thru the various metals being used in the other Herbie Cups. I've heard many people say Brass feet in general are a bit "warmer" sounding most likely due to it being denser than something like Alum or Titanium. Same goes for Cork or Sorbothane, many report a warming of the sound when placed under speakers. I've not tried those other materials so cant confirm or deny this. All I know is that I don't want a warmer sound so will not be trying those items.

Just for your information I have been measuring and analysing vibration in a professional capacity in the aero and other industries for many years.

With that said, I do find it interesting that you seem so skeptical about much of the information being discussed on this topic. I've not made any pixie dust or magical veil removing claims here. If you've done work in this field surely there is something to all of it otherwise there would be no work for you to do :)
 
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cjf

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How does the cabinets mass get increased? A spike coupling may affect how the object is constrained at that junction.

Well to "Couple" two objects together is to "make them as one" with each other. If you Couple a speaker to the floor would you not in essence be extending the speaker cabinet to now also include the mass of the floor or platform its attached to? If you take a 150lb speaker and Couple it to the floor via a Pin Head size point the pressure at that point will be much greater then it would be if you were to instead Couple the speaker to the floor via a 1" round/square disk.

Which of these two scenarios would you rather have your finger trapped under? :)
 

Don Hills

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That's not correct, I'm happy to say that the panels of the speaker will vibrate in sympathy with the impact of air movement within the cabinet...

That's a second order effect, and doesn't create a significant amount of force / energy / movement at the speaker to stand/floor interface, assuming an adequately constructed enclosure. The pressure acts equally in all axes. The main effect is the action - reaction between the speaker moving mass and the enclosure mass.
 

fas42

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That's a second order effect, and doesn't create a significant amount of force / energy / movement at the speaker to stand/floor interface, assuming an adequately constructed enclosure. The pressure acts equally in all axes. The main effect is the action - reaction between the speaker moving mass and the enclosure mass.
???? ... The moving mass of speaker driver, typically paper, is minute in comparison to the cabinet - but, there is reaction on the frame of the driver, attached to the front panel, which transfers to the cabinet.
 

Nightlord

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Here is a picture of one of the Townshend Seismic load cells. Obviously a spring with some rubber material around it and metal end caps.

Townshend-Seismic-Isolation-load-cell.jpg
If the movement was straight down, then that would be just fine. Not sure how ideal a spring is in regards to sideways movement - which is the main case for a loudspeaker.
 

Nightlord

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That's not correct, I'm happy to say that the panels of the speaker will vibrate in sympathy with the impact of air movement within the cabinet - and the degree of that will vary with how much shaping, stiffness, bracing, damping the panels have. However, I have not addressed this to any significant degree with the speakers I've used up to now, because it has not been a major issue, for me. I suspect that if I want extreme clarity, at high playback levels, then it will become more important, but I haven't felt the need so far.

What I would be interested in, if you're going to do some experiments, is how much attenuation of panel vibration occurs if various means of mounting the speaker is tried: spikes vs. spongy discs vs. Blu Tack vs. nothing used, etc.

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
 

Don Hills

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???? ... The moving mass of speaker driver, typically paper, is minute in comparison to the cabinet - but, there is reaction on the frame of the driver, attached to the front panel, which transfers to the cabinet.

Indeed. But do the math. Typical 12" driver 50 to 100 grams mms. Typical enclosure for that driver 20 to 50 Kg. Mass ratio about 500:1. Assuming the enclosure is rigid, the radiation from the enclosure is only about 55 dB down on the radiation from the driver. (Actually, it's worse, because the radiating area of the enclosure is several times greater than the cone area.)
Or if you have the enclosure measurements, you can work out the force (and vectors) present at the corners of the enclosure base.

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.
 

March Audio

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In this instance I've not tried their other offerings so cant comment on how the other cup options function or sound compared to each other. The only data I can go on is via what is published online by those who have tested how sound/vibration travels thru the various metals being used in the other Herbie Cups. I've heard many people say Brass feet in general are a bit "warmer" sounding most likely due to it being denser than something like Alum or Titanium. Same goes for Cork or Sorbothane, many report a warming of the sound when placed under speakers. I've not tried those other materials so cant confirm or deny this. All I know is that I don't want a warmer sound so will not be trying those items.



With that said, I do find it interesting that you seem so skeptical about much of the information being discussed on this topic. I've not made any pixie dust or magical veil removing claims here. If you've done work in this field surely there is something to all of it otherwise there would be no work for you to do :)

Saying that the different metals used in the different herbie cup versions sound different is fairy dust.
 

March Audio

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Well to "Couple" two objects together is to "make them as one" with each other. If you Couple a speaker to the floor would you not in essence be extending the speaker cabinet to now also include the mass of the floor or platform its attached to? If you take a 150lb speaker and Couple it to the floor via a Pin Head size point the pressure at that point will be much greater then it would be if you were to instead Couple the speaker to the floor via a 1" round/square disk.

Which of these two scenarios would you rather have your finger trapped under? :)

And the mass still hasnt changed has it?

No you wouldnt be making them as one wrt vibration. Look up modal / fea analysis on youtube. You are constraining one end. It may change vibration, but not stop it.

Btw, why are you worried about having this spiked contact when it sits on a compliant bit of herbie super dooper wobbly stuff?
 
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March Audio

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What I would be interested in, if you're going to do some experiments, is how much attenuation of panel vibration occurs if various means of mounting the speaker is tried: spikes vs. spongy discs vs. Blu Tack vs. nothing used, etc.

That is exactly what I am planning to do when I mange to get hold of the measurement gear. Might be a week or so.
 

Kal Rubinson

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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
What kind of floor?
 
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