[goodvibes]

  Drivers are very different to musicians; single drivers are far better at reproducing complex music than they are at reproducing simple things like pure sine tones.
The BA has no problem with complex music, it plays it just like it plays simple music. When I can't hear a busy passage of music clearly, it's my brain failing to keep up with the instruments because the sound is missing information.
 
The reason why multiple BAs are used is because BAs are naturally nonlinear and have narrow frequency response (the ER4 series would beg to differ, of course).
 
These days two BAs are enough to reproduce the entire spectrum, though. Maybe a few more for tuning, but much more than that and you're heading into "why" territory.

Lots wrong with those generalizations. You could say all the same things about dynamic drivers. None of them are 'naturally' linear and why the diversity of makes and models. That's just as true of speakers and linear wouldn't sound linear as an iem anyway. The rest is tuning and there are plenty of single driver BAs that are full range. Everybody makes one and they don't sound less linear than their dynamic counterparts that also tend to use acoustic filters etc for compensation. I still feel products like an Etymotic HF5 etc are as good as anything in it's price range. It may not be certain individual's personal favorite but it's a wonderful device. 
 
As for the Shure in question, I'd be curious as to what the OP thinks is missing since it's configuration is that of a fullrange driver for the top and mids and bass drivers with a simple phase coherent xover. I'd suspect whatever he doesn't like has nothing to do with it being a multi way device.

 

[tomscy2000]

I'd suspect whatever he doesn't like has nothing to do with it being a multi way device.

 
+2

 

[Yggdrassilious]

I like my single/dual-BA IEMs (ER4PT, UE700) far better than my SE535 and W4R. Less size, more comfort, better sound. 

 

[goodvibes]

The 535 is a 2-way so it has nothing to do with it.

 

[Spyro]

IMHO supposed "crossover issues" with multi-drivers are very often fitament and tip issues instead.  I don't think it's that difficult.  We're not splitting atoms here.

 

[truckdriver]

I wonder what exactly the OP noticed missing in the two occasions using mult-BA (as oppose to a single-BA or DD)?
 
What I notice missing in all the IEMs that I've used is what I believe to be room reflection that aids singing voices. That, of course, is a different issue altogether.

 

[Rollk2]

Did you try high-end IEM like ToGo334 / S-EM6 / JH13 or 1+2 ?

 

[harkohark]

I had some UE's and I felt the same way. THey were of craptastic quality also.

 

[goodvibes]

I've never like most the UE multi driver units either but it's not because they're multi driver. They sound like that because UE wanted the to. Lots of single driver things I don't like as well. 

 

[rawrster]

There's a lot of generalization here. Multi drivers does not automatically mean it's bad just like single driver does not mean it's good. I've owned and heard good and bad from both. I will say that multi drivers have a higher potential to be better but does not always reach it imo of course

I don't know if this applies but my uerm and jh5 are both multi driver and easily among the best I have heard but I don't know if this conversation is limited to universals only or not

 

[Deviltooth]

In my collection of C/IEMs the best by far are those using multiple drivers.  Contrary to the OP I hear more detail with a multi driver setup.  I like the RE-400 and the GR07; it would be fantastic if these offered the same quality of a CA Pro 330 or a JH13fp but they don't.  In truth they don't even come close to the point where I find anyone arguing otherwise a touch ridiculous.

 

[truckdriver]

Well, despite the provocative title of this thread, so far all the OP said was (with the Shure 535) there was something missing in two songs. Without more detail, it hardly indicts multi-driver IEMs (writ large).
 
There's something missing in a few of my songs on one of my phones,  but I suspect a bad sector on my SD card (or some such thing) is the culprit. The same song on another source plays just fine. I know,   it is not the same thing to have a faction of a second skip in a song as oppose to missing musical tones within an otherwise normal passage.
 
.

 

[Spyro]

There's a lot of generalization here. Multi drivers does not automatically mean it's bad just like single driver does not mean it's good. I've owned and heard good and bad from both. I will say that multi drivers have a higher potential to be better but does not always reach it imo of course
 

 
Really?  I think it's always better  For example Shure E4 was an outstanding single driver.  There are things I don't like about SE535 but it is still better no question about it.
 
UM1 versus UM2, W2, etc.....clearly better
 
Super Fi 3 versus Super Fi Pro or TF10....clearly better
 
Not sure if I can think of any example where adding the driver was a step back.

 

[goodvibes]

I actually like the SF3 better but it wasn't because they couldn't blend the drivers. I'm just not into bass heavy or v shaped.