ATH-M50x headphones have me questioning my bass mix

I just got the ATH-M50x headphones.  These were at Sam Ash, where they had a nice display where you could listen to a dozen different headphones.  I did some blind testing with a friend.  As an aside, some of the best sounding headphones, IMHO, were Samsons in the $60-$90 range.  But this ATH-M50x had an extra bit of clarity, even beyond the best Sennheiser phones they had on display, according to my ears anyway.
 
When I got home, I immediately listened to some music I had recently mixed.  I was shocked by how strong the bass was -- to the point of booming and somewhat crowding out even mid-range material.  I went back to my near-field monitors, which are Yamaha MSP5 and the bass was quite subtle.  Granted the Yamahas have only 5" drivers and I don't use a sub, but I really didn't expect THAT much difference.
 
I also tried a set of decent ear buds, which sound a lot like the Yamaha mix to me.  I had already tested the mix through some mid-range Altec computer speakers and again, the balance was a lot like the MSP5.
 
So it really is the AT headphones that are different.
 
I wonder how common this is to find the bass much stronger in high-end headphones.  And considering that few people will be listening to the music through such headphones, do you adjust the mix based on what you hear in the headphones?  I think I could adjust the compression on the bass to keep the punch but limit the boom after the transients and that might be a little better for all listening modes.  I'll have to check the mix again, but the bass may have been running into the verb buses a little, and I could probably dial that back.
 
A few weeks back, the client for that recording project was playing the music through his car stereo and the bass was really dominant.  He liked it that way, even though I didn't think that was a very natural sound.  I had assumed he had an EQ on the car stereo with the bass really cranked.  He did have the bass cranked a bit, but I am thinking his car stereo might have had a similar response curve to these AT headphones because I had the same reaction to both cases.
 
I wonder if it is time to upgrade those MSP5s.  I suspect they roll off below 150 Hz more than I thought.

JonD
The ATH-M50x phones are giving you a truer representation of your low end.  Think about it -- you've been using speakers with 5" woofers -- no way you're going to come close to an accurate bass on those.  

 
Thanks for the ideas.  I guess that is what I suspected, but it helps to hear it from somebody who has been there.  I don't think I will go with a sub because I work almost exclusively with jazz and classical stuff.   I don't do much music where a thundering bottom is expected.  And when you use a sub, there is a question of how true the LP stuff is.  I think I will look for a pair of studio monitors that are true  down to 35Hz or lower.
 
And then I'll go back and re-mix those recent projects.  I had been thinking about redoing the mastering step now that I have the new Ozone, but I really need to fix most of this in the mix, I think.

Also, keep in mind that Closed-back headphones can sometimes exhibit a perceptively tighter, fuller bass than open-back cans. The headphones bitflipper referenced, the HD-600's, won't exhibit a build-up of bass, even naturally. What sets those more expensive ones apart is that, ideally, they aren't exactly designed to be 'pleasant' to listen to for hours. They should expose issues in a mix (if touted as 'reference') headphones. Accuracy over enjoyment.

I shot out three sets of reference style cans here and I could tell difference, even with these headsets. None of them exhibit a real noticeable bass boost. I kept the AKG k712 Pro, not really because I found them to sound the best of the three sets, but because I felt they would make my judgements of a mix much more translatable to other systems. They do pretty well, although I think vocals/elec.-guitars tend to be slightly lower in the mix in these headphones. Minor things.
 
I've used AT-M40fs cans for years, and have multiple pairs for tracking bands. They are notably stronger/fuller in the bass than the reference sets I tried. But they still sound quite good, considering. I never had any complaints--beautiful, deep low-end. I can only surmise that the M50x's are even better, and certainly for the price!!

Double helpful on what Dave said. I have used those headphones for years. First the ATH M50 and now the ATH M50x. I never rely on them when I mix bass, or any headphones. I get better mixes on monitors when mixing bass.
They are good for mixing the mids and highs. Even the upper ranges of bass. Not so good for mixing bass though.
 
Long mix sessions on monitors at lower volume seems to help my ears hear the balances better. Long mixes on headphones cause ear fatigue which changes how I hear a mix. We tend to want the music louder on headphones. Probably trying to hear the mids over the bass. This causes ear fatigue, and in turn, causes us to make bad mix decisions.
 
Try mixing on phones for three or four hours. Get the mix sounding good. Now the next day listen to it again on monitors. I have never save a mix I made like this.

cparmerlee
 
Having said that, it seems all "wideners" are not equal in this regard.  The Waves and Izotope wideners seem to be more mono-friendly than some others.  Could that be true or am I imagining it?

It is very true. It really depends on what the wideners are doing.
 
Regards,
Dan

When I mix only on headphones my bass seems to suffer on stereo speaker systems. If I get it right on the monitors, then it usually sounds good on earbuds, this statement seems like it should be opposite, but that's how it usually works. I make bad bass decisions on headphones, usually pulling out too much bass and then the music on monitors is bass wimpy. 
When going back to headphones on the same mix, the bass is ok. The outcome might be different for someone who uses monitors in an untreated space. I use ARC when I monitor without headphones. ARC tends to notch out a lot of the bass. In reality it really isn't eliminating the bass, what it's doing is eliminating the influence of that small room and evening out the frequencies Anyone who is in a smallish like 12' square or less room will have standing bass waves. The ATH-M50X has a slight bump in the mid bass ranges. As long as you know about it you can compensate for it.
I use the ATH-M50's mostly for mixing anything above the mid bass. I might even run my bass down when I mix on them which isn't a bad idea to make sure you have everything above that right. Then the bass is a back and forth kind of thing I do between the phones and the monitors. NEVER have I had the bottom end right only using the headphones.
 
I've spent 2 hours on a mix late in the evening on headphones, came back the next day and almost cried the mix was so bad.
 
 

the audio models are the best headphones in existence in my opinion. Best sound by far.