I bought iFi’s ieMatch impedance matching tech based on Amir’s review, and it solved significant problems for me—problems that I think are significantly underappreciated by many who might not realize that their sensitive cans or IEMs might have impedance mismatch issues with their amplifiers.
The ieMatch he tested comes in 3.5, 2.5 and 4.4mm versions as a separate headphone cable adapter, and offers three user-selected attenuation settings—0, -12 and -24db. IFi has a headphone calculator on their website that gives you setting recommendations based on a large database of commercially available cans. In my case the ieMatch came built into the 4.4mm jack of my iFi Pro iCAN Signature amp, and apparently applies variable attenuation based on the load it senses when headphones are connected.
I have several sets of headphones, including Focal Utopias, Sennheiser HD800s and a Sony Z1R, and despite the amp putting out over 14 watts of power, I was experiencing clipping with both the Utopias and Z1Rs at not unreasonably high volumes, particularly with any added DSP low shelf bass boost.
The amp comes with three gain settings—0, 9 and 18 db—and when using the non-ieMatched XLR headphone output, I had to set the gain at 0db to achieve appropriate volume ranges. The Sonys and Focals have impedance ratings of 60 and 80 ohms respectively, while the Sennheiser impedance is 300 ohms. The Sennheiser had no clipping issues at all.
When I finally got 4.4mm cables for the Utopias and Z1Rs, I plugged them into the ieMatched jack, and at first was puzzled because the volume dropped dramatically. But then I turned the gain up from 0 to +18db, and the headphones sprung to life. The resulting sound was considerably smoother and markedly less sibilant, with audibly less background noise—and I couldn’t get them to clip no matter how much volume or bass I threw at them.
@amirm found similar results in his review, with more sensitive cans only (the sound quality was expectedly worse with the high impedance headphones he tested). His review kind of came and went without much fanfare, but it brought to my attention the importance of being attentive to the output impedance of my amplifier in relation to the headphones I choose, and gave me a solution that opened up my options without having to part ways with my existing gear.
This is a review and measurements of iFi Ear Buddy which is the cheaper, non-configurable version of iEMatch. I purchased it for USD $20 from Amazon. The purpose of both devices is to reduce the output power of a headphone amplifier. This is needed often when the headphones are too sensitive...
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