The following has the usual caveats: IMS, IMHO.
So having had really good experiences with TWL's power cords, I decided to try the Spirit ICs and American speaker cables. Short conclusion is that they are very good and a great value. They are very much of a kind sound wise and thus I've reviewed them as one.
They are also unlike any other ICs and SCs I've ever tried (I've tried a lot).The uniqueness comes in the form of a pronounced forwardness to the sound plane (in front of the speakers) that yet retains very good depth (and width and height). Every other cable I've heard that was "forward" either had an up tilted treble or overly accentuated leading edge transients. These cables have neither. The treble is actually a touch recessed and the leading edge transients are not accented although they are well delineated and not rounded or soft.
So where does the "forwardness" come from? My guess (and it is pure speculation) is excellent dynamics and PRAT combined with a very prominent mid-range. These cables are punchy and fast.
And yet the mid-range is very full and warm. It all gets a little confusing as to how this all is when you finally try to analyze everything but that takes a while because the cables are so seductive sounding that analysis is difficult to get to.
As to frequency response, the bass is extended and tight while, as mentioned above, the treble is a bit recessed and - it seems - slightly rolled off. The treble is also a bit "sweetened". (Edit: these treble qualities apply mostly - perhaps solely - to the ICs.) Enjoyable (I listen to a lot of strings) but not totally accurate. This, it must be said however, is only in comparison with my reference ICs which are a few times the price and provide a treble that is purer toned and more extended than I've ever heard in my system before. The mid-range, as noted before, is very full. The cables also separate out images quite well.
Full harmonics are another excellent quality to these cables. The leading edge transients are clear, and the trailing edge transients have good decay. And the held notes have a roundness I don't think I've heard before. This, their treble sweetness, and the very good PRAT of the cables are what give them the seductiveness I referred to above.
All in all, excellent cables at great prices.