A/Bing against the HA-M750. I can clearly tell the superior tuning on the HA-S500. The better resolution on the drivers. Now the bass is strong on the HA-S500 but where they differ from the older HA-M750 is the rest of the sound. The HA-M750 bass is so strong it does have some mid bass hump. It warms out the overall sound a bit and lacks some clarity because of this. Not the case for the HA-S500. I would say sub bass wise it is a bit less than the HA-M750 but not by much. But to me strong sub bass is ok it is the rest of the sound I am more concerned with. If you want less bass I would look into a M-80. Will be more to your liking. Much more neutral in that respect. I also got a tip on these portables. Neutral and perhaps less bassy all around.
$100 Noontec Zoro. I got a PM from BBlord about these. These are getting rave reviews even though they look like beats..Might be worth checking out. Steve Guttenburg says these are more neutral and pic off more detail than the M-80. So does the HA-S500 so it seem we are seeing more advances in sound for your cash.
The tuning on the HA-S500 are superior and has much better control, clarity, imagery, dynamics over the older HA-M750. The HA-S500 are like a newer more refined version of the HA-M750. This is a fine example of the advancements for JVC. The older HA-M750 lean more toward a bassy sound yet don't have the technicalities to pull off the sound right which results in the warmed over veilish sound..The HA-S500 corrects this issue resulting in one of the best musical sounds I have heard not only not lacking in any part of the sound but excelling at it.
Don't know if your ok with on ears but these throw out a full sized sound for certain. These have imagery and clarity on all parts of the sound over the HTF600. The HTF600 was and still is one of the best for the cash but these for being a bit more not only have a better build but the sound is one of the best I have heard for anything under $100 I have ever heard. And bass wise. The bass on these actually are stronger than the HTF600 and reaches deeper. Very high quality bass on these headphones.
Sorry never had the HM3s. I am sure in due time one of the guys that get these will chime in with your answer..Another great budget headphone. Would be interesting to read up on an A/B against these HA-S500.