I was very sceptical about the E500. I did not expect to like them. I don't like Shures because they put out too much mid range and not enough highs for my taste, E5 has too much bass for me and it sounds too stiff and not dynamic down there to me.
But when I put the E500s on today, I was blown away! First I was blown away by how comfortable they are. The bigger size actually makes them seat better on me than both the E5 and UM2. The angle on the output tube is closer to right angle I think, which works well for me. The metal plated smooth shell is also very comfortable against my concha, no molded-in logos and sandblast finish to irritate the delicate tissue of your ear. Fit and finish is not quite as beautiful as E4, but you can't see them anyway when you have them in your ear and they are the best feeling universal IEM I have ever stuck into my ear. How can so many drivers be this light?
As for the sound, I was blown away by that too! I guess it helps them that I was listening to my super.fi 5 Pro for about an hour before I swapped to the E500, but everything just sounded "right." More "right" than 5 Pro for sure. The highs sound very similar to E4, but smoother. Full and detailed. I don't find it to be rolled off too much to be unacceptable, but I still prefer Etymotic highs. The lows were very tight, dynamic, extends pretty deep down, and most importantly not bloated. Definitely not what I expected from 2 bass drivers. I expected total bloatedness out of proportion but this is not the case. Seems to have a more restrained bass than both 5 Pro and UM2 but I can't say for sure yet. Definitely tighter than both down there, yet not "stiff" like E5. Unlike the rest of the Shure line and the other multi-driver universal IEMs, the mids are not bloated either. Very natural and smooth mids. I think the crossover and the balancing of the drivers are very well done on the E500. Down side of the sound? They definitely sound better without the PTH unit. One gripe only (so far) about the sound of the E500 (minus the PTH), is that soundstage is not spectacular. Everything sounds very close to me, which is good in a way that all the instruments are balanced quite well and the closeness equates to being able to hear fine details unlike most multi-driver universal IEMs (although not as good as any Etymotic, although I am able to say better than E4).
Not so impressed by the PTH, which is very cumbersome and has a mic separate from the unit itself, yet the mic is not in the earpieces where I feel they belong. So you get lumps and lumps of stuff along the cable between your ears and your source. And each of the plugs are huge themselves. Let's see, starting from the source, you get a straight plug that is a bit more than an inch long, it scares me a bit because I can imagine leaning on it a bit too hard and cracking my ipod 5G, with that jack on that dangerous angle. Then up stream you get that huge PTH thing, which looks like a Japanese Samurai Fighting Beetle with no legs, almost the size of an iPod Nano, and almost 3 times the thickness. Go upstream from there you get the mic unit, which is a a bit longer than 2". With or without the shirt clip, it is going to be banging around on your shirt. If you walk while using the PTH you will not be able to avoid the microphonics (amplified by the PTH, I might add), unless you hold it in your hand to dampen it. Connected to that mic unit, there is a plug that connects to the E500 earpieces themselves, and that is another HUGE one. A smaller fighting beetle this time. Too much! Too clunky. Everything upstream from that I am happy with, which is just standard black Shure wire leading up to the earpieces.
About the PTH sound, I have auditioned the Sensaphonics 3D Ambient and was dumbfoundedly impressed by it to the point that probably anything less will seem unimpressive to me, but here is what the Shure PTH lacks that the 3D Ambient has (yes I know, 3D Ambient costs over 3 times the price of E500). 3D Ambient has 2 mics per earpiece, on the earpieces themselves. What this does is that they pick up sound exactly as you hear them, much more accurately than even binaural recording because not only do you have the ability to distinguish left and right due to mics in the left ear and right ear, but you also can distinguish front and rear on the 3D Ambient. Essentially you have front right, front left, rear right, rear left mics, and the panning across these mics gives you accurate directions and distances. On the Shure PTH, nothing. Flat. No soundstage, no nothing. On the 3D Ambient I was stunned that I can close my eyes and listen to someone speak while walking around and be able to tell exactly where he/she is and at what distance from me. On PTH, backgound music coming from ceiling-mounted speakers, sounds of peoples' thighs slapping against their plastic bags over 10ft way, and the voice of the cashier in front of me at the convenience store are squashed together as if they were being picked up, in mono, from one mic (because they are!). No directions, no distances. Very unnatural and very difficult to understand speech. A bit shy in low end so you won't even know if Barry White is speaking to you. Also, you cannot adjust the mix of ambient sound and music. There is a cheap roller pot volume adjuster on the PTH unit that allows you to only adjust the volume of the ambient sound picked up by the mic. The music goes WAY down when PTH is on, to an almost inaudible level. On 3D Ambient you can mix both together because there is a mixer with individual level adjustments built into the belt pack.
I don't have a UE-10, but as soon as the E500 is nicely burnt-in, I can compare it to the Sensaphonics 2XS. For now though, the E500 is definitely a worthy opponent for all the top end custom IEMs, I am sure. Nothing else to compare them with because none of the universals come close, and I've heard/own them all. For audiophiles, dump the PTH, install your eartip of choice, and you are good to go.