I've been through this whole deal and spent way too much money trying to find the best system. For huge deep bass, nothing beats the Future Sonics MG7 Pro. They are useless as far as general listening goes, as the frequency response is too lumpy and they are too sensitive for iPhones, etc., but for onstage bass playing, nothing beats them. IF you get a good fit. That's where I had problems. I went back and forth too many times and what it came down to is that there only seems to be one guy in Colorado who can really make the impressions properly (George Cire) and I didn't know about him when I had them made. If I were wealthy, I'd get him to make some new impressions and jump on these in a heartbeat. The only other time I've heard that kind of low end depth was playing through Mike Gordon's Meyer rig. The MG7s don't give you the thump of a double 18 in terms of hitting you in the chest, but they give you everything else about deep, deep, bass. And it's not one note bass, every note is clear, distinct, and articulate. Some IEMs are simply hyped and it just sounds bloated rather than truly deep.
I also have the MG5 Pros and they are excellent. Still really good bass, but very balanced and listening to music is a joy with these things. Future Sonics are all single dynamic driver IEMs, so their high end is very smooth and the low end blows away all the balanced armature IEMs, although some come close.
Future Sonics also make a universal IEM, but the problem with them is too much bass. And the seal isn't nearly what the custom fit versions are. You can, however, get sleeves that improve the situation. The rest of my band uses them and likes them a lot, but they've never experienced the custom molded IEMs.
So, after all that hoopla and raving about Future Sonics, what do I use every day? Sensaphonics. Two reasons: 1) George Cire did the impressions (I found out about him from the Sensaphonics website, no matter who you buy from, I recommend using their recommended audiologists) and 2) they are not a hard mold but a soft silicone that has a lot more give. So the seal is much, much better. I bet that if George did the impressions for my Future Sonics, my search would have ended there, but I'm glad I threw down for the Sensaphonics. For on stage use, they are hard to beat. I have the basic dual driver model. They do suffer a little bit from being a balanced armature design, so they aren't as hifi or as deep as the MG5 pros, but they are quite good. For that reason, I don't use them for listening for pleasure or mixing.
I would be remiss if I didn't mention Etymotic ER4XRs. They are a brand new model, so I haven't tried them, but I am very tempted to upgrade my plain old ER4 to them. The ER4s, despite being a balanced armature design, have some of the best frequency response of any IEM and certainly give a bunch of high end headphones a run for their money. Where the standard ER4s fall down is in big bass. They have low end, but it's not that huge. The ER4XR is supposed to be even better all around, but especially improved in the low end. They are also the second best seal to Sensaphonics, despite not being a custom molded IEM. I was skeptical about these for a long time, but now that I have a pair, I have to say that I love them. They sound fantastic, seal well, and are not that expensive, compared to a custom molded IEM. I would agree with the above that custom is the only way to get good isolation with the exception of the Etymotics. The isolation is that good.
One of the big issues for me is tinnitus. I have a far amount of it, so I cannot play without ear plugs, but even better is IEMs. I need isolation if I am going to be able to gig. I even lug around a splitter and a computer driven digital mixer to do my own mixes, except at festivals where I don't have time to set it up. It makes all the difference in the world to have great sound and not have my ears blown out.
And Wayne is right as far as other products from Sensaphonics. I have two pairs of their earplugs and have thought about getting a set of sleeves for the Etymotics. They do great work.
They typically do a holiday sale around Christmas time that is well worth jumping on. It can save you $100 or so for the lower priced IEMs and even more as you go up.
One last thing about Sensaphonics. If you have the scratch, they have a system where there are mics built into the IEMs and the belt pack can mix the mics back into the send from the monitor mixer. I haven't tried them, but it seems very cool. If you have $2k to drop on the system. Friends of my mine swear by them and will often just use the mics. You can also utilize a send to record what you are hearing. It's worth scoping out their website to see all the cool things they do.
