Well, I have used both what you term as "fast" cartridges, such as (my current cartridge, the Dynavector XV-1S), as well as the Koetsu cartridges,, (the Black and the Rosewood Signature).
My feeling is that the Koetsu cartridges have positive and negative aspects to them.
First off, they are indeed lush sounding in the mid-range. If you like that sound (I do, as a matter of fact), then you'll love them. If you prefer a more neutral sound, than they might not be for you. If you love vocals, than this might be the line of cartridges you'll love forever.
Second, they have a slightly rolled off treble response, but as you climb the ladder, this becomes a non issue, as the better Koetsu cartridges have excellent treble extension. (IMHO anyway).
Third, and probably the most conerning, is they usually have a rolled off bass response, that is also somewhat loose (i.e. not tight or quick). As you climb the ladder, this becomes somewhat less of a concern. However, from what I have experienced (which does not include the stone body cartridges, but does include the RSP), they never truly have what I would call great bass response. (They were nowhere near as good as either my Shelter 90X or my XV-1S.)
Fourth, I found them to be great tracking cartridges. (In fact neither my Black, my Rosewood Signature, or my friend's RSP ever mistracked, no matter what we threw at them.) Where did you hear that they were poor tracking cartridges, btw?
Fifth, they have a very low noise floor. Ticks and pops are not much of an issue actually. (They were much better than the Benz Micro Glider II, and a bit better than the Shelter 90X.) My Dynavector XV-1S is as quiet as the Koetsu line, if not quieter. (I LOVE quiet cartridges!)
Sixth, yes there is a very stiff markup here in the states on Koetsu cartridges. (Why, I have no clue!) So, if you can either get a used one, or one on the grey market, you can avoid that problem.
My opinion is that they are a great line of cartridges, that are well worth experimenting with. If they work for you, great. If not, you'll, at a minimum, enjoy the lush mid-range for vocals. I managed to get a great deal on the Dynavector or else I probably would have waiting for a deal on a used Koetsu Jade Platinum.
My two cents worth anyway.
My feeling is that the Koetsu cartridges have positive and negative aspects to them.
First off, they are indeed lush sounding in the mid-range. If you like that sound (I do, as a matter of fact), then you'll love them. If you prefer a more neutral sound, than they might not be for you. If you love vocals, than this might be the line of cartridges you'll love forever.
Second, they have a slightly rolled off treble response, but as you climb the ladder, this becomes a non issue, as the better Koetsu cartridges have excellent treble extension. (IMHO anyway).
Third, and probably the most conerning, is they usually have a rolled off bass response, that is also somewhat loose (i.e. not tight or quick). As you climb the ladder, this becomes somewhat less of a concern. However, from what I have experienced (which does not include the stone body cartridges, but does include the RSP), they never truly have what I would call great bass response. (They were nowhere near as good as either my Shelter 90X or my XV-1S.)
Fourth, I found them to be great tracking cartridges. (In fact neither my Black, my Rosewood Signature, or my friend's RSP ever mistracked, no matter what we threw at them.) Where did you hear that they were poor tracking cartridges, btw?
Fifth, they have a very low noise floor. Ticks and pops are not much of an issue actually. (They were much better than the Benz Micro Glider II, and a bit better than the Shelter 90X.) My Dynavector XV-1S is as quiet as the Koetsu line, if not quieter. (I LOVE quiet cartridges!)
Sixth, yes there is a very stiff markup here in the states on Koetsu cartridges. (Why, I have no clue!) So, if you can either get a used one, or one on the grey market, you can avoid that problem.
My opinion is that they are a great line of cartridges, that are well worth experimenting with. If they work for you, great. If not, you'll, at a minimum, enjoy the lush mid-range for vocals. I managed to get a great deal on the Dynavector or else I probably would have waiting for a deal on a used Koetsu Jade Platinum.
My two cents worth anyway.