Thought I'd mention, and FWIW, that there's also another very experienced HF'er, MuppetFace, who has rated the SM64s quite highly.
There may be some people in this thread who already know I'm not exactly a fan of Erasonics — I thought their SM3 was a dreadful IEM (BTW, I've yet to see a FR graph after all these years of one of the most hyped IEMs on Head-fi, an IEM, btw, hardly anyone mentions these days [I wonder why] — people still talk about other IEMs that have been around for some time, but the SM3..…). Build quality on the SM3 was poor and Earsonics' customer service (CS) leaves quite a bit to be desired as evidenced by several accounts from unhappy customers who have spoken of the less than stellar CS they received from ES. And, on that note, I was on the phone to, and emailed, ES a couple of months ago, and let's just say I wasn't impressed by the responses I got, to put it very mildly — wasted precious time and money (on long-distance calls).
That said, quite a few people have said the new SM64 is a pretty good IEM. Yet, once again, we have what appears to be a not so great looking FR graph, measurements of which, BTW, were taken from a faulty SM64 unit, no less (!). Those who know me know I'm quite averse to hype, BS, exaggeration, misinformation and so on. But, I'm afraid to say that now we seem to have something approaching the other extreme, ie "if it doesn't measure right / perfect, it can't possibly sound good". I personally appreciate FR graphs and measurements—I really do—as I'm someone who in several ways strives for factual information and honesty.
I've mentioned something a couple of times recently: "for quite some time I've been questioning the accuracy of FR graphs specifically for IEMs (not for full-sized headphones). Apologies to those reading this post if I choose not to rehash what I've said in other threads to explain roughly why this is so.
One last thing, I really wish udauda / Rin didn't use a mouthpiece and, instead, posted himself, or at least did so (much) more frequently. I've no idea whether udauda / Rin would display the same attitude often seen by his mouthpiece. In some ways I applaud udauda's stance regarding some of the audio companies / matters we often talk about in these forum threads (he often tends to be very critical), and feel, for the most part, his findings are valuable…BUT something seems a bit too extreme at times, which sadly spoils some of this often valuable work — another form of bias is how I see it, I'm afraid to say.
Unfortunately, as is so often the case in many parts of our lives, we get the fans, the extremists even, believing only in data in this case (data I personally sometimes question, as noted above) — effectively, and I don't believe I'm not exaggerating here—allowing data / graphs to dictate what sounds good / right, just another for of placebo in my book, ie if the data says it sounds good, therefore it does sound good to my (measurements-biased) ears. On the other hand, we get people who seem to feel threatened by data, perhaps because they've made such outlandish claims that may really be so off the mark at times, they'll just happily say, "I don't believe in graphs". Finding the middle ground is much easier said than done—and often just a mere cliché—as we generally don't even know where the middle ground lies since we can't even recognise where the extremes lie.