mystery muffled mids

I suggested trying different speakers as a process of elimination. It would rule out other potential sources. 

following suggestions here, i tried another pair of speakers. it's definitely not the speakers. Thanks! 

Your description sounds like your bass is overwhelming the soundstage. Sounds like room interaction bass problem. Speaker placement 

could you elaborate what makes you think bass is an issue? And why it would impact only some music but not others? thanks!
I forgot to put that I have a sub, B&W ASW610. 

Anything by Bill Frisell, for instance, sounds phenomenal. You feel you can grab the instrument from the air. I mention this since he uses similar instruments to Zeppelin. Bowie's stuff sounds awful, as does Queen. I know they should sound better. Kind of Blue is fantastic. Gaucho, Sea Change, Elephunk, Wildfloflowers, Know what I mean? -- all great. To a friend, I said that this means bad recordings sound bad. The friend said that's not it. what do you say? How can I improve the sound? 

Any of a number of ways. But that's not the question now, is it? You clearly have great sound already-

Anything by Bill Frisell, for instance, sounds phenomenal. You feel you can grab the instrument from the air. 

To think you have a system that can do this, but yet it has something so strangely wrong it cannot do it with Zeppelin, is just nuts. You even have the answer already, and yet no one here can see it. Why am I not surprised?

Technically, it is not the recording. To understand what is going on you have to really know and think about all the various steps involved between the performance in the studio and your playing it at home.  

The only way to say for sure it is the recording is to have the master tape. Never gonna happen. Next will be a copy printed at the time. With Zeppelin that will be a vinyl record.  

We know the Zep was really well recorded because, well look:  https://better-records.com/products/ledze3_2104?_pos=3&_sid=3c678aa90&_ss=r  You simply do not get anyone paying $800 for muffled mids. Tom gets big money for these for one reason and one reason alone: they sound freaking fabulous! (I know, I have several.) 

Yours sounds muffled. It's not the recording. What, then?  

Original Master tapes represent a tremendous investment no one wants to risk, so right away they start making copies. These copies almost always are what is used to make the records and CDs we buy. They can be any generation, any quality. Then too the care taken in making the pressing can vary widely.   

If you are streaming Zep guess what? They bought a crap file, probably made from a crap copy of a copy of a copy of a master tape. Something like that. Last thing in the world it has anything to do with is your system. Everyone here should know this. Jeez Louise!