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Revel Salon2 measurably and ABX audibly improved by $5 silicone pads

neutralguy

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My Salon2s had long been sitting flat on my hardwood floor, whereas the manufacturer recommends using the supplied spikes. Do speakers supports matter so much that it's worth potentially damaging my floors and raising an already high tweeter? Intuitively a compliant support such as blutack or silicone pads could absorb some of the cabinet's vibrations. Wouldn't that be better for the sound anyway? I had done an investigation previously using my Revel M105 speakers on a desk, a setup much more susceptible to vibration, and found that silicone resulted in the lowest vibration to both speaker and desk, beating out spikes and flat placement with no spikes. Here I report on a similar experiment on my Salon2s.

To measure vibration, I used an AKG C411 vibration microphone as an accelerometer. When attached to say a guitar, the C411 turns the instrument's vibrations into electrical signals for amplification. Mounting the tiny C411 using blutack onto the Salon2 and using it as mic input for REW, it measures the speaker cabinet's vibrations as the speaker plays REW's sine sweep. I took measurements from two spots on the front baffle, near the Salon2's upper bass driver (baffle bass) and near the tweeter (baffle tweeter). Here's how it looks when mounted on baffle tweeter.

baffle tweeter.jpg


I compared two placement options, flat (speaker touching floor) and silicone (pads between speaker and floor). I did not test spikes because my previous measurements using a M105 showed spikes to yield even more vibrations than flat, so I wasn't going to spike my floors with a 130lb weight. First is the results of the vibration measurements on the speaker baffle.

results C411 baffle.png


Absolute decibels here do not correspond to sound levels, as these are surface vibrations. What we focus on is relative differences. "C411 noise baseline" is the microphone's response when speakers are muted. All traces show some vibration above baseline. The most drastic difference between the two mounting options is between 100-200hz. There's a massive bump of around 20db peaking at 115hz at baffle tweeter for flat vs silicone, and a lesser bump at baffle bass. 20db suggests a 100x difference in vibrational energy. Where did this upper base energy go? To check whether it could have been transferred to the floor, I took vibration measurements of the floor 6 inches in front of the speaker.

results C411 floor.png


There does not apppear to be large differences in floor vibration. There may be a small difference in the high frequencies, but around 100-200hz it looks very close, with silicone vibrating less if anything.

I also took vibration measurements at the middle of the speaker's side panel.

results C411 side.png


The differences here are more minor. There is a small bump around 50hz for silicone, but as we see below this difference does not appear significant enough to affect the output sound. If using a subwoofer the Salon2 would be alleviated of duties at this frequency anyway.

Let's now look at how the sound output is affected. These frequency response measurements were taken 6 feet in front of the speaker, upper midrange axis, using a Shure SM81 microphone for reasons explained below. Its response for this purpose is very close to my calibrated UMIK1 except for a moderate bass rolloff.

results 6feet FR.png


We see that flat and silicone are basically the same except around 115hz. Zooming in:

results 6feet FR zoom.png


We see a 1.5db bump around 115hz for flat. Given the above measurements showing the baffle vibrating 20db more for flat, I'm going to assume that this bump is due to additional contribution from baffle vibrations. As such, I assume the bump is undesired.

Since vibrations of the cabinet and floor, as well as the sound output, are all equal or reduced for silicone, my conclusion is the cabinet's vibrational energy at 100-200hz must have been absorbed by silicone pads and turned into heat. Sounds like a good thing to me.

But how does this affect the sound subjectively? If I came on ASR and said these $5 pads with a 1.5db Q=5 effect cleared up the midrange and upper bass, I might be laughed off the forum and called a snake oil salesman. Even I doubted what I was hearing, which was a fairly noticeable difference. Swapping the pads in and out takes too much time and effort for an ABX test, so what to do?

This is where the SM81 comes in. I placed a pair of level matched Shure SM81 microphones, 2' in front of each Salon2's tweeter, and recorded them playing music in stereo. This microphone was chosen for its low noise and flat frequency response. Its cardioid pattern helps reduce sound from room reflections. The recorded files, which sound surprisingly good with stereo imaging intact, were played back on speakers using Foobar's ABX plugin. On a sample of music I'm familiar with (a Bach concerto), I was correct 14 out of 16 trials (p = 0.0021), with almost no practice. If this forum allowed it I can upload the recorded files and everyone can try too.

ABX results brandy.png
I distinguished a difference by listening for exactly where the measurements showed differences, in the upper bass. The flat placement recording seems to have extra oomph and bloom in that region. The difference is minor, but if it can be discerned even through distortions of the recording process, in all likelihood the actual difference is at least as audible or even more so. While ABX proves a difference audible to at least one person, it does not mean it will be preferred to an average listener. I do think silicone definitely sounds better in my listening, but I may be biased from being aware of the measurement results.

TLDR

My main takeaways from this experiment:

1. Silicone pads placed under Revel Salon2 on a hardwood floor, compared to flat placement, reduces vibration between 100-200hz and makes a measurable and audible difference. They can be found on Amazon.

2. Using a vibration microphone can show significant differences for a seemingly minor tweak. Correlation with regular frequency response measurements of sound suggests these vibration measurements are relevant to sound output.

3. Recording speaker output and using Foobar's ABX comparator on the recorded sound can show audibility for a tweak that otherwise seems minor.
 

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5-pot-fan

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Congratulations on undertaking, and publishing, such a test.
I am not well enough informed to comment on the scientific validity/integrity of the test, or the interpretation of the results, but I hope we see more such tests here. With the availability of good (and inexpensive) hardware and software it should be possible for more of us to do similar things and hopefully the results will benefit more than just the tester.
 

More Dynamics Please

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Checking the Amazon link for the silicone pads I followed a couple of additional links and landed on some Sorbothane pads that caught my attention. That reminded me that years ago I had some shoe insoles made of Sorbothane that did an outstanding job of reducing impact and stress on my feet when I was doing a lot of work on concrete floors. I'd expect Sorbothane to be even better than silicone but it would take similar testing to objectively determine any additional benefit for speaker performance.
 

jonfitch

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Checking the Amazon link for the silicone pads I followed a couple of additional links and landed on some Sorbothane pads that caught my attention. That reminded me that years ago I had some shoe insoles made of Sorbothane that did an outstanding job of reducing impact and stress on my feet when I was doing a lot of work on concrete floors. I'd expect Sorbothane to be even better than silicone but it would take similar testing to objectively determine any additional benefit for speaker performance.

Doesnt sorbothane pads damage wood finishes over time? I think you would need some kind of additional buffer if placed directly under speakers.
 

More Dynamics Please

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Doesnt sorbothane pads damage wood finishes over time? I think you would need some kind of additional buffer if placed directly under speakers.
The pads I linked to have adhesive backing so no direct contact between Sorbothane and the speaker. If adhesive isn't desired it would be simple enough to have a neutral thin spacer between Sorbothane and any wood finish.
 

Matias

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Very nice!

The IsoAcoustics Gaia feet also reduced about 20 dB vibrations although "slightly" more expensive :), and in different frequencies because it is a different speaker, of course.

chart-GAIA-vs-Spikes-2048x1147.jpg
 

Thomas_A

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The effect varies with speaker and floor type but what can happen is that the transmission to the floor with hard coupling leads to distortion.

#43
 

Steve Dallas

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Doesnt sorbothane pads damage wood finishes over time? I think you would need some kind of additional buffer if placed directly under speakers.
I use Sorbothane discs and hemispheres on some of my stands. Wax paper placed between the speaker and Sorbothane discs keeps the Sorbothane from affecting the finish. I make no claims about whether Sorbothane is better than any other material, however.
 

theREALdotnet

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What does the C411 record when, during a measurement sweep, it is near the baffle but without touching it?
 

Lsc

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I use the supplied spikes with the round end down. I felt like my salons sounded better post spiking too.
 

restorer-john

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Cork is really good for speaker/surface interfaces IME. It has just the right amount of stiction to prevent speakers sliding, isolates very well and depending on the texture/thickness, you can experiment until the desired isolation is achieved. Cork also lasts a very long time and doesn't mark either the speaker or the surface. And, very low cost, easy to cut up and use.
 

mainframe

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The jiggly pads from Darko's video on the S400 MKII's look like interesting candidates for this conversation

"Moongel Resonance Pads"
 

Sancus

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Chromatischism

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Checking the Amazon link for the silicone pads I followed a couple of additional links and landed on some Sorbothane pads that caught my attention. That reminded me that years ago I had some shoe insoles made of Sorbothane that did an outstanding job of reducing impact and stress on my feet when I was doing a lot of work on concrete floors. I'd expect Sorbothane to be even better than silicone but it would take similar testing to objectively determine any additional benefit for speaker performance.
I have been using Sorbothane discs under S400 MKIs since 2019 and now MKIIs. At the very least they:
  1. Help my speakers stay put when I make small changes to positioning, ala Blu Tack or UHU Tac
  2. Raise the tweeter 1/2" which is good for my seating
I have not spent the time to do a formal investigation as to any differences, so good job to @neutralguy on his work here.

However, the stands vibrate less with the pads on, very noticeably, when holding them with my hands. This makes sense if you understand what the material is doing.

The pads I linked to have adhesive backing so no direct contact between Sorbothane and the speaker. If adhesive isn't desired it would be simple enough to have a neutral thin spacer between Sorbothane and any wood finish.
I use Sorbothane discs and hemispheres on some of my stands. Wax paper placed between the speaker and Sorbothane discs keeps the Sorbothane from affecting the finish. I make no claims about whether Sorbothane is better than any other material, however.
I actually left the adhesive backing paper on in order to make them non-marking. There is a very thin ring around the edge that does make contact once they squish a little, and that's enough contact for my purposes.

For readers wanting to try them, choosing sorbothane discs isn't just a random affair. You want a certain % of compression so it depends on the weight of the speaker and number of discs used. You'll want to refer to the official website and do a little math of your own to buy the ideal part #. You generally want the softest material, but if the speakers are really heavy, you'll choose a stiffer version.
 

Jdunk54nl

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I should have taken some measurements on my Philharmonic BMR's from spikes on my hardwood with those little plates under them to the svs sound isolation feet that are now on them.

Good work OP.
 

MattHooper

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Fascinating, neutralguy, thank you!

Someone posted a link to my own less formal experiments, I see.

As for sorbothane, I have all my external hard drives (for my work) sitting on sorbothane pads. Without it they are sitting directly on my desk and in a wooden cabinet which amplify their vibration (e.g. from the fans or just the general hum) to an obnoxious degree. Sitting them on sorbothane makes them almost silent.
 
OP
N

neutralguy

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Thanks for the comments everyone. It sounds like sorbothane is the people's choice candidate for an improvement over silicone. I'll get some to compare.
 
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