I have owned 3 RS1i, yes 3 because they sounded so different from a SR60i that I had to be sure I didn't get odd balls. I've come to the conclusion it's just the way it is. It has a serious level of warmth that prevents any harshness, only smoothness. Poor recordings won't sound so bad on the RS1i unlike all the other grados.
My first listening impression was,
"...err what the heck is this??"
I'm a huge fan of the bright grado house sound and I cannot deny that I was disappointed in hearing the RS1i. Any non ""i models possess that bright grado house sound if you want to know what I mean.
The RS1i strays away from the house sound found on the SR60i. If you are expecting a bright live performance like the SR60i then do not get the RS1i, but get the buttoned RS1. The RS1i instead makes everything sound very smooth, too smooth. To say the RS1i sounds bright is laughable (with comfies,bowls and flat pads), it's a big downgrade in treble hotness from the SR60i. RS1i leans more towards the bass and midrange rather than the usual treble and midrange.
Do not buy the RS1i as your first grado, you will be missing out. Buy the SR60i first and if you find that it is too hot sounding then you can try the RS1i.
The highs are very smooth and delicate. I never get irritated by this presentation but it sounds too safe. Zero shrillness, if you dislike how all the other grado's treble sound then there is a good chance the RS1i will be for you
The midrange is very warm and lush. It does not possess the high mid spike found on the SR60i that makes rock music shine but instead, Grado has changed the RS1i to be more of a all arounder. SR60i excels at rock over a RS1i because of its frequency response even though the RS1i is more about the quality. The RS1i frequency response is different from the graph shown at Headroom, imagine all the peaks just tamed down by 10db or more. Any song I listen to, I always hear the midrange warmth. Some people will not like this thick sound as it takes away transparency. I would not dare us a tube amp with the RS1i, the midrange does not need to be any thicker because it's already too much. The RS1i will never ever sound thin no matter what I threw at it compared to the SR60i, that's how dense the midrange is. The RS1i is not the headphone for rock sadly, no high mid spike energy for guitars and drums. I would say Grados are the rock headphones, however for the RS1i I felt rock is the genre it seemed the least impressive at which is quite shocking. I would say the RS1i was better for pop than rock. The RS1 buttoned is simply better in that genre.
The soundstage depth is considerably better than a SR60i. The width is largely unchanged. A lot of layering can be heard.
The bass is noticeable more and better. The bass has body but there is a lot of midbass presence in a lot of songs that may make the song sound a little odd and congested. These can go low. In a lot of ways the bass is better but some may not like it.
To some it may seem like the sound is refined but to me , it is too tame. I don't think this is the right step as an improvement over the RS1 because clearly, the sound has taken a big change. I hesitate to recommend the RS1i as an upgrade. However, the RS1i is amazing in its own way even though it wasn't the exact sound I was looking for. For some songs, I do enjoy its fullness and warmth as well as its strong bass slam. It still has the speed of a grado and the pacing. The RS1i is by no means a bad headphone, there are many others who enjoy the RS1i. The sound signature I am chasing needs to remain the same as the SR60i without a large change.
On the other hand, if you're in pursuit of the smoothest sounding grado headphone then the RS1i is the jackpot. It is just not capable of sounding harsh, no exaggeration.
Extra notes:
Now trying jumbos on...
Pads make a big difference on the RS1i. If you put on the jumbo pads found on the GS1000i and PS1000i, the RS1i sounds ridiculously close to a PS1000i except for the amount of bass which the PS1000i is dominant in. The treble stands out so very clearly, pushing the mids back so it does not sound so thick. The whole sound in general becomes very transparent sounding. I was very impressed with Jumbos on the RS1i much more than bowls. I did not try a PS1000i with bowl pads so I can't say how closely related the drivers may be.
Interestingly using bowls,if remove the bowls and place them on top of the drivers the bright sound is there but the upper mid spike is not.