Any one measured the EMI/RFI attenuation performance of audiophile power conditioners?

@tvad: Thank you for your kind words.  Indeed, we supply EMI filters for very broad applications around the world (including Antarctica).  Most of top U.S. universities (Caltech, MIT, U.C. Berkeley, and so on) use them in their R&D work.  Quantum computing here in the U.S. and in Japan use our filters to be able to work with very weak signals.  Nuclear power industry likes our filters too.  And, of course, various industrial applications.  If you don't meet or exceed published specification, you won't be in business for long...  Audio is a relatively small segment for our filters, just FYI.

Regarding impact on sound:  EMI filters (such as our CleanSweep) or any power conditioners are not supposed to affect sound in any way except to remove extraneous artifacts, otherwise they become a part of your sound path.  If you want to improve sound quality, then perhaps a filter shouldn't be your first choice...

Regarding measurements: people often make critical and/or expensive decisions based on measurements (think of a spot on a CT scan - was it caused by a spike on ground?).  Both tools and methodology must be considered and exercised carefully. If you are curious, here is a link to an article I wrote on the subject for inCompliance Magazine, a publication for EMC professionals.  Amazon-grade instruments aspire to provide "easy" and meaningful measurements, but you can get only that far on spirit alone without solid engineering foundation.  Their typical problems are insufficient bandwidth, lack of true peak measurements, and, importantly, missing common-mode measurements (i.e. between Live or Neutral to ground) - just to list a few.  This doesn't mean they are useless - any instrument, no matter how sophisticated, has limitations - just don't make surgery plans on that white spot on CT scan measured by Amazon...

Vladimir Kraz/OnFILTER

To answer @Audio phool's question (sorry for a long reply - didn't have time to condense it):

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QUESTION: "@vk_onfilter I saw the productline of your company which looks impressive & you seem to serve diverse industries including chip manufacturing, R&D centers etc. and you have provided the performance chart for your products. Besides you seem to have more than 40 years of experience in the field of EMI/RFI reduction/compliance. Is application of EMI/RFI filtering to audio any special than other industries you serve which allows one to not to specify the performance data? Can such practice will be acceptable if the same product was to used in other industries than in Audio?

Audio_phool"

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The basic foundation of any technical product is a specification.  Engineering Bible starts with "In the beginning there was a specification" :)  In a number of ways a specification tells the designers of the products what a product should accomplish, in very specific terms (not "it should reduce noise a whole lot" but by how may dB at which frequency, and how it should be measured).  It tells the manufacturing group of the company that every single manufactured unit needs to meet or exceed very specific parameters (again, not just "sound good").  It is also a commitment that a supplier of a product gives to a customer - after all, the customer gives similar commitment to the supplier in a form of money.   Whenever you see a product that claims a whole lot but lacks that very specific commitment, it tells you quite a bit.  In the most benign case this would mean that a manufacturer has no idea what does this word "specification" actually mean - not a good notion for any product, especially a technical ones.  Anything else points to either knowing what that specification actually is and not being willing to present it to the customers; or thinking of a customer as an idiot who would buy anything "shiny" that is accompanied by flowery language and inflated price.  
In your own business, whatever it is, you likely buy and/or sell products and/or services.  Would you pay money in your business for something that has no "specification" of the sufficient type?  Would you feel right selling something where your customers have no idea what they are buying?

All our filters (of which AC EMI filters is just only one segment) have specification - sufficient to those in the industry who are in a need of noise reduction.  If we didn't have specifications and didn't stand behind it, truly, very few companies would even consider working with us.  From our perspective there isn't a difference between an EMI filter for a R&D center in a major university and the one for home audio - the only difference is so-call leakage current requirements to comply with the safety regulations - UL1283, UL/IEC 60939 (all our AC EMI filters are safety-certified by an independent accredited laboratory).  We have two basic kinds - industrial type, and hospital/medical/residential grade - grouped by the leakage current limits.

The sole purpose of a filter is to block to the best of its abilities incoming electrical noise and not affect in any adverse way the power itself.  Anything else is not a filter's job.  I believe it would be a mistake and an unreasonable expectation that somehow a filter (or a power conditioner) will improve sound quality, short of reducing incoming electrical noise.  Whatever quality problems you may be experiencing, don't start by adding a filter, unless all you need to reduce is noise.  Now, a poorly-designed filter/conditioner can add plenty of problems by itself, including intermodulation distortion, clipping, and so on - this is where a professional-grade product works, and the "shiny" ones may or may not.  

I do hear time to time from our customers in audio market that our filter either improved sound quality, or it didn't.  I would LOVE to know which specific parameters were affected - if only we knew it, the sky is the limit for the future improvements.  Studying for my MSEE specializing in audio I went through a good number of courses such as psychoacoustics, medical aspects of hearing, and alike.  I remember how at the conclusion of our course on Acoustics (a very demanding course because it is half-analytical and half-empirical) our professor said to the class "Now you know all that a man knows about sound, but only God knows what a man wants to hear" - that's sums it up.  I fully respect a huge subjectivity aspect of listening; I am also cognizant that if one buys an expensive "shiny" piece of equipment, one's brain works overtime to convince itself that it now sounds better for sure.

So, to conclude way-too-long of an essay, no, there is no difference for us in the filter design nor in requirements for the detailed specification for audio and for industrial or R&D market, short of safety regulations.

A note on input/output impedance: most measurements in RF domain are made in a 50 Ohms termination.  Conducted (i.e. on wires) EMC test per regulations is also conducted with 50 Ohms termination.  Appliance filters (this is the UL and IEC classification of the filters built into equipment to make it comply with EMC regulations) such as made by Schaffner and so many others are therefore optimized for 50 Ohms termination. One may say "tuned" for such termination for maximum attenuation. The problem is, I haven't met a power line of 50 Ohms yet.  More realistic matching impedance accepted in the industry is more like 0.1/100 or 1/100 Ohms, where the lower impedance is the source (i.e. your outlet) and the higher one - your load.
Some of the better appliance filter manufacturers like Schaffner (give it to the Swiss - they have specifications) and Schurter used to list in their datasheets performance at both 50 Ohms and 0.1/100 Ohms.  However, lately Schaffner has "sanitized" quite unfavorable data (I do have saved their datasheet from before the "cleansing") and for the most of their products they list only 50/50 Ohms data.  The only one I found which still has complete data is their FN343.   
Schurter still provides "honest" data for their filters - see this  as an example (you would need to figure your way on this page).

Scroll down and find the attenuation curves.  What you see is that 0.1/100 and 100/0.1 curves show "negative" attenuation at lower frequencies, meaning actual EMI amplification.  In short, in an EMC test lab this filter will help to comply with CE/FCC requirements; when plugged into real outlet - it will amplify noise. 

I wrote an article for inCompliance Magazine on the discrepancies between EMC regulations and the real world which, in part, addresses it.  

Look at the section called "50 Ohms Question"  You can find this and other articles in our online Technical Library

A corollary issue is the frequency range.  When you look at the above-mentioned Schaffner or Schurted data, note that the real-life attenuation curves end at 1MHz. There is a reason for that.  Parasitic capacitance and inductance of power cables essentially kills higher frequencies.  Now, what are the sources of the signals in a typical residential environment (for audio purposes)?  It is, in no particular order of significance, switched mode power supplies encompassing LED lighting, solar and other inverters, plug-in supplies for just about everything, TVs, and the list drums on.  Another source would be variable frequency drives (refrigerators, pumps, A/C, washers, dryers, etc.).  All of them operate at lower frequencies - SMPS, for example, work somewhere between 40kHz and 150kHz.  1MHz attenuation data that I see are not that relevant for real-life applications.