Strangely enough, the Grado SR325i at first proved to be inferior to the much cheaper SR80 in terms of sound scene, frequency balance and reproduction of details. It turned out that this was caused by the cups pressing to hard to the ear. The default ear-pads do not provide enough space between the diaphragm and the ear conch while it is highly necessary for the Grado SR325i. The similarly designed SR80 is free from that problem. There are two ways to correct it. You can remove the ear-pads from the cups, squeeze them slightly and put them back on one side only (on the top of each cup, for example). This will move the speaker away from your ear. You can also buy additional ear-pads from other headphones or use them together with the default ones. After these simple procedures the sound of the SR325i changes dramatically. The bass does not muffle the medium frequencies, in which every detail becomes audible, while high frequencies become much smoother. As a result, the SR80 was out of competition instantly, losing to the SR325i in every parameter: it has a less detailed bass, a flat but lifeless middle, and serrated high frequencies. Although the sound of the SR80 is energetic, light and not tiresome, it does not create a full music picture. It is too sketchy – here is a beat of the drum, here is the cymbals, and here is the singer. The Sennheiser HD 600 and Grado SR325i carry much more information, so it took us more time to learn their peculiarities.
The fundamental difference between these two headphones is about the bass and the reproduction of space. They form the audio scene differently. The Sennheiser moves the virtual sound sources away from you and wide from each other, which results in an unpleasant feeling of vacuum in your head with some specifically mixed recordings, but it is superb at reproducing live unprocessed recordings. The SR325i places the sound sources closer to each other and merges them into a single whole, but in some recordings you get a feeling of a musical instrument pressed right to your ear.
It is hard to tell what is better when it comes to reproducing space, but the Grado SR325i is obviously better in reproducing bass. It is not about its quantity (there is enough of bass in the Sennheiser, too) but in the level of detail: it is deep and energetic, variegated and superbly controlled. Sometimes there is even too much of it. The Sennheiser HD 600’s bass is not very solid and seems vibrant in its top part. This adds more charm to the contrabass but is no good for drums or tomtoms. The high frequencies are not quite natural with both models. The Grado SR325i has an increased middle of the high-frequency range and some jingles just deafen you while the ambient noise is hissing irritatingly. The Sennheiser HD 600 emphasizes the top of the sound range, which is sometimes discomforting.
The sound of medium frequencies is similar between the three headphone models, but the Grado SR80 cannot match the other two in the liveliness of reproduction. The Grado SR325i is superb at reproducing string and wind instruments, the piano sounding lush and energetic. The specific acoustic enclosure of the speakers adds some reverbs to all medium-frequency sounds, enlivening them. Male vocals are natural and energetic with pleasant bass tones but the emphasis on the bottom middle is not good for female vocals. It seems that the singer is forced to sing one register lower. It’s all otherwise with the Sennheiser HD 600: male vocals lose the bass tone but female vocals are just splendid. The HD 600 also has a minor advantage when it comes to the sound of the fiddle, reproducing the resonance of the instrument’s case better. A special feature of the Sennheiser headphones is that they show all insignificant sounds such as the touch of the lips and the tongue, the rustle of clothes, the touch of the strings and case with the fiddlestick, etc. All these sounds are audible in the Grado SR325i, too, but they do not distract you from the music proper. The emphasized detailedness allows the Sennheiser to reproduce the harp perfectly, but the vibrating top bass makes the sound of trumpets and saxophone rather unpleasant. The electric guitar sometimes lacks the drive you want from it, the bass guitar lacks strength, and the acoustic guitar has an emphasized high-frequency jingle of the strings. The HD 600 is especially unconvincing when reproducing symphonic recordings where the Grado SR325i sounds superbly. The relaxed sound of the Sennheiser proved to be optimal for compositions of The Doors, Mylene Farmer, Madonna, and many calm live recordings, though.
While listening to music with the Sennheiser HD 600 we had an impression that they needed a different amplifier, with a smooth decline in the high frequencies, which would be able to enliven this product, excellent in many respects. Unfortunately, we didn’t have a proper amplifier to check this out in practice, but this supposition is confirmed by users’ reports.