[joesuburb]

I've never really had more than one IEM at a time.  I usually lose them, then replace them.  I usually don't plan ahead, I just roll the dice and find something local I can get quickly.  However, I happen to have 4 sets of IEMs at the moment.
 
I don't know if my perception is normal or perhaps I'm just completely insane, but this is how my brain is working with the IEM's.  I've never noticed this at all with my home hi end audio system and I have 2 totally different setups that I would consider hi-end.  Dyne/B&W Nautalis.
 
I own Sennheiser IE8s, Monster Coppers, Monster Golds, and some old Shure 410s.
 
 

1. When I put in the Sennheiser IE8s for the 1st time after the coppers, they sound fine immediately.
2. When I put in the Monster Coppers for the 1st time after the Sennheiser IE8s, they sound small and it seems less pleasant at 1st.  

 
Now here is the kicker.  If people would ask me which one I like better, I would say the Coppers every time.  I think they just sound much better and are more enjoyable for me.  But, not back to back.  I think I might be insane, or my brain just accepts the open sound of the IE8s more easily.  Anyway, just a weird experience.  But it's great having all the different units to enjoy.

 

[ClieOS]

Psychoacoustics, or as we like to call it here: "Brain Burn-in"

 

[arcticears]

"Brain Burn-in" indeed.  The brain does seem to imprint the last sound signature it has been exposed to.  I have noticed this over and over.  I think it explains, in a large part, the fact that you read many responses in the threads where people receive a new iem and right out of the box it sounds bad but it quickly begins to sound better and after awhile it sounds great.  We saw this with the DBA 02, people were getting them and selling them almost the next day.  I recently experienced this when I got some Westone W2s.  Right out of the box my first thought was these have to go back, all mids and treble and no bass.  I kept trying them and by the end of the next day, hey, where did all of this bass come from.  Part of it was finding the right tips but it was also my brain adjusting to the sound.  You can try this yourself easily, listen for an extended period of time to an iem with strong bass then switch to one that is balanced such as the IE7 to a DBA 02.  The DBA 02 will have sharp highs and no bass.  Then listen to the DBA 02 for a good while, even stop listening and rest your ears for several hours.  Now go back to the DBA 02 and it will be balanced, the bass will be there and the highs will be in-line.  It is almost like the brain has its own equalizer.  It tries to adjust what it is receiving and when you switch to a different iem the brain's eq is stuck on the old setting and it makes the new iem sound bad.

 

[joesuburb]

Isn't the brain an odd thing.  I'd assume there is all sorts of science around this.  I wonder why I've only noticed this with IEMs and not my home hi-fi setup.  Both are very nice, and they are different, but they sound, how they sound, all the time

 

[Photofan1986]

Yes, I experience the same quite often. I have the SM3, IE8 and RE252, and wanted to sell one of those, and sometimes I really feel like one of them simply should go (every single iem was in this position, one day or another). Then, two days later, when I listen to the phone I've decided to sell (as it sounded so much worse than the other two), I realize how good it is and that I certainly won't part with it.
But at the moment, it seems so evident (which one is the loser) that it's frightening to hear that several days later, I really enjoy its sound quite a lot!

 

[mark2410]

this is why i never realy listen to one thing for more than a day at a time, keeping the pallet clean and what not

 

[arcticears]

The effect does not seem to be very great when switching between iem's with similar sq, but when you go from an iem with a pronounced response in one area, bass, treble, etc. to a very different sq the effect is pronounced.
 
With a home (speaker) system there is much more going on with the sound we hear, room interactions, etc. that may lessen the effect.  With an iem the sound we hear is so focused or dependent on the iem the effect may be more apparent.

 

[Bennyboy71]

Easy solution: sell brain, buy more iems

 

[arcticears]

Yeh, but I would not get much for my brain.

 

[rawrster]

Imagine how some other people feel who have much more than a couple pairs (ClieOS, joker, etc) I only have a couple but usually I just spent my time with 1-2 over the course of a month and then rotate although my collection has gone down by a decent amount lately.

 

[11amaberry]

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It burns! Lol.​

 

[JeFFz]

lol that's weird for you or might be the same for me i don't know. Having owned the MTPC and i liked it a lot, i went to demo the ie8 and right at once i was in love with it. Going back to the MTPC sounds tiny like you said lol...
 
Im not sure will i still like the ie8 after longer hours of use but maybe the ie8's sound signature is easier to get used to at the beginning?