Measurement Thread: Measured Effect of Speaker Isolators

amirm

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Just saw this from Ethan Winer, investigating the measured in-room effect of various speaker isolation devices. The test is DIY so not without faults which Ethan himself volunteers: http://ethanwiner.com/speaker_isolation.htm

These are the variations/products tested:

* No Isolation elevated, also not elevated
* IsoNode Isolation Feet (3/4 inch high)
* Auralex MoPADs (2 inches high)
* Empty Cardboard Box (2-3/8 inches high)
* Primacoustic Recoil Stabilizer (2-5/8 inches high)
* DIY 705 & Plywood (2-7/8 inches high)
* IsoAcoustics Aperta (2-7/8 inches high)

Here is sample result from the test:



Read and discuss :).
 

DonH50

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I will read better later (at work now, alas), just skimmed. From what I saw, the table holding the monitor is not a great platform and may influence the test results.

I will note that many years ago I took measurements trying various feet under a few speakers. They were all floor-standing models as I recall, including a couple of Magnepans, Quad ESLs, B&W 801 (original, this was ca. 1982~1984 timeframe), a pair of Polks popular at the time, and a few others I've forgotten (*). The floor was concrete with commercial carpet (thin with limited foam beneath). I measured the impulse response, do not recall frequency response showed much, but you could clearly see changes in the impulse response on a 'scope. However, listening tests did not show significant change with various feet (spiked, several flavors of isolators, and in one case bolted a pair of Magnepan's feet to the floor). I also measured Magnepan and Quad (I think) panels with added stiffeners to brace them, same results (measured differences were not readily if at all heard). The biggest difference by far was in the bass, which makes sense given relative mass and such, and that does appear to jive with Ethan's measurements though my foggy memory is that I saw more difference in impulse response than he measured.

That was long before things like Stillpoints and all the high-tech isolation devices of today, be interesting to repeat the experiment.

Interesting - Don

p.s. Measuring other components we did see the effect of vibration on some tube gear, less (virtually none) on SS, and of course all kinds of stuff out of a turntable playing a silent groove.

(*) In college I was lucky enough to work for several high-end stores, and one in particular had an owner who loved running all sorts of experiments. We spent many evenings and weekends with other local 'philes and engineers setting up all sorts of things, and often roped local audiophiles in for various listening tests. One of my biggest regrets is that the mass of notes, data, and various papers I helped create and co-write during that time has been lost through the years. Along with a number of manuals for my stereo system from that vintage. I am convinced we either lost some boxes in a move, they were thrown out by accident (my wife saves newspapers and a box with that data and a few papers on top may have been tossed in the belief it was simply a box of old newspapers), or is lurking in one of several black holes of storage around the house and shed.
 

DaveC

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Pretty much anything you do to a mechanical device will change something. The obvious thing is the stuff at 20hz showed some significant changes and a few other places showed some 5 db swings, but as most tweaks, after you do that, is the response more correct or less correct?

IMO floor standers should come with whatever coupling or spikes or isolators the manufacture finds most useful to tune their speaker, anything else is just making a change in sound, the never ending treadmill of changes for changes sake because we can hear a difference, no matter if it is better or not, and how would one know, really. A

Anyway thanks to Ethan for doing some measurements for us.

This seems completely disregarded by most mfg'ers. But isolation is not just a change, it's an obvious improvement in clarity of the bass extending into the midrange, and not just a lateral change. As far as why it's disregarded, there are a lot of reasons... cost, complexity, ignorance...

--------------

He's really measuring the wrong thing, frequency response is the last thing I'd measure. Think about what isolation does... maybe we should be measuring how much vibration is transmitted to the floor? That's the entire point of isolation devices, they prevent cabinet vibrations from being transmitted into the floor. Why this would have an effect on frequency response is a mystery to me, it shows some changes but not within the realm of normal deviation from one measurement to another. Every measurement you do indoors at low frequency is different no matter how much you try to keep everything the same. These results are completely useless imo... they show nothing and prove nothing, a complete waste of time.

I'd propose a much better test would be to measure the vibration in a few different spots on the floor around the speaker using a variety of tones, if that's not possible you could measure how much some random object in the room rattles around. In fact you really don't need to measure it at all. Just crank up some bass-heavy tune on repeat and walk around the house observing what rattles. Then throw the speakers on IsoAcoustics stands and check out the same stuff and notice that most of it stopped rattling entirely while the rest is rattling at a much lower level. It's a night and day difference vs spiking the speaker to the floor, whether the floor is wood or concrete.

The effect it has on what you're hearing is very obvious but I'm not sure how you'd measure it directly. Distortion measurements may reveal some good information, as there will be more bass distortion without isolation from the surroundings vibrating. But the valuable result that makes isolation worthwhile is the increased clarity, definition and detail in the bass that extends into the midrange. The whole soundstage becomes more holographic. It's VERY obvious.
 

dallasjustice

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Ethan should be commended for doing all this work. I have 2 criticisms.

1. A distortion plot may be helpful in this case but he didn't post those. If he still has the files, maybe he can post them.

2. I also very much disagree about the 3db cutoff he required for there to be an audible change. I'm not sure where he came up with that number. IME, a little as -1db makes an audible difference when applied over a wide bandwidth. It appears that there is at least such a difference in his SPL plots. I base my conclusion on experience using target curves. 1-2db over a wide HF bandwidth can shift the soundstage back or forward depending on the frequencies attenuated. Maybe the small SPL differences we see are due to imprecise measurement position. I can't say.
 

dallasjustice

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I have to disclose something. I just ordered a custom pair of isoacoustics stands for my new JBL speakers. Currently the JBLs are mounted on H dollies I purchased at Lowe's for $19/. The H dollies are great. Maybe I can take a couple of before and after measurements between the H dolly and the isoacoustics stand. The H dolly and the isoacoustics stand is 5.25" tall.

I'm biased. :D
 

amirm

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Love to see the results Michael. Just make sure you get some decent electricity to power your system. I hear it is horrible in Texas.
 

amirm

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BTW, Ethan has contacted me with some responses to your posts. I don't want to be the go-between. You all OK with him coming back and participating in these discussions?
 

GaryProtein

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Absolutely yes.
 

dallasjustice

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I also think Ethan's measurements can't have sufficient resolution to only measure the speaker at those frequencies. Even at 1m, the measurements get swamped by the room. We can see that the measurement can't be quasi-anechoic as evidenced by the floor bounce, which Ethan mentions. If Ethan windowed the impulse to only be impulse before the first reflections off the floor or other walls, there wouldn't be enough resolution in the measurement to be useful. I really think an outside/elevated measurement would be much better.

This criticism is mainly aimed at how Ethan measured the primacoustics "recoil stabilizer." That product's claim is that it improves the speaker's performance. Not all of these product make the same claim or supposedly work in the same way.
 
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DaveC

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DJ, you could get a short spiked platform to put the IsoAcoustics stands on, if you have carpet. That way the Iso stands would be on a flat, smooth surface rather than carpet. But I've had a couple people I know try them right on carpet and they reported the same improvements. I need to see if there's a way I can get Iso to make bottom feet that can either be the standard rubber material or a carpet spike... I suppose I could fabricate spikes to be used with Iso stands but that seems like a lot of work. :)

On measurements I still don't see how isolating the speaker will change it's frequency response. What is the hypothesis that's being examined here? If it's that isolation changes FR, that might be misguided, and will be be very difficult to measure accurately. It might change distortion, but you'd have to find the resonant frequencies of the floor to find the peaks and a sine sweep probably won't put enough energy into the system to get full response. I think you'd need to measure distortion at various frequencies manually, which could be pretty labor intensive, or maybe pink noise at high volumes would do it. A long sine sweep might give enough info to figure out where the resonances are so they can be excited by a single-frequency test tone... In any case high volumes would make the differences more apparent so I'd lean to testing at high volumes for everything. Floor vibration and distortion should be possible to measure much more accurately vs FR, at least for relative levels.

I'm not sure you'll be able to measure differences in some things, like midrange clarity, because the reason the midrange seems to clear up when isolation is used is really due to less distortion in the lower frequencies, so muddy bass and room/floor resonances aren't interfering with the mids anymore. There really may be no change in the mids at all, but in subjective listening the increased clarity is very obvious and this is frequently reported in reviews of isolation products.
 

DaveC

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I also think Ethan's measurements can't have sufficient resolution to only measure the speaker at those frequencies. Even at 1m, the measurements get swamped by the room. We can see that the measurement can't be quasi-anechoic as evidenced by the floor bounce, which Ethan mentions. If Ethan windowed the impulse to only be impulse before the first reflections off the floor or other walls, there wouldn't be enough resolution in the measurement to be useful. I really think an outside/elevated measurement would be much better.

This criticism is mainly aimed at how Ethan measured the primacoustics "recoil stabilizer." That product's claim is that it improves the speaker's performance. Not all of these product make the same claim or supposedly work in the same way.


I've been doing a lot of speaker measuring lately and I agree, it's just not possible to get meaningful measurements at those frequencies. Random variation measuring short sine sweeps can be significant without changing anything at all.
 

dallasjustice

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Gregadd

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BTW, Ethan has contacted me with some responses to your posts. I don't want to be the go-between. You all OK with him coming back and participating in these discussions?
I am hardly neutral on the subject. Ethan is well known around Internet audio forums.
I think a life time means just that.
I vote no.
 

amirm

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Thanks Greg and everyone else. I re-instated Ethan's membership. He will only be posting in this specific forum.
 

rbbert

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0%; I'm with Gregadd here
 

GaryProtein

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I also think Ethan's measurements can't have sufficient resolution to only measure the speaker at those frequencies. Even at 1m, the measurements get swamped by the room. We can see that the measurement can't be quasi-anechoic as evidenced by the floor bounce, which Ethan mentions. If Ethan windowed the impulse to only be impulse before the first reflections off the floor or other walls, there wouldn't be enough resolution in the measurement to be useful. I really think an outside/elevated measurement would be much better.

This criticism is mainly aimed at how Ethan measured the primacoustics "recoil stabilizer." That product's claim is that it improves the speaker's performance. Not all of these product make the same claim or supposedly work in the same way.

Are you saying the speakers need to be brought outside to the driveway or patio to make the measurements?
 

NorthStar

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Are you saying the speakers need to be brought outside to the driveway or patio to make the measurements?

Is that a problem Gary? ____________________________________________________________________________________________________________ ;-)
 

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