After getting through many cheap nasty wired sets of headphones which kept breaking, I decided to purchase wireless Philips SBCHC8440 Wireless Headphones.

Technically they work fine apart from one problem. I am an avid music listener and listen to my collection many hours a day and have complex aircraft sounds on my flight simulator which I use.

I have noticed a weird issue with the volume control whereby the headphones literally try and keep any part of a song or music I listen to at exactly the same volume, therefore meaning there are absolutely no volume dynamics in the music which the composer intended to include. If a louder part of a song comes up the headphones "adjust" and that part sounds quiter than normal. Likewise it adjusts quieter sounds to sound as loud as the louder parts.
I find it extremely distracting, personally. I don't know if there is any way this can be sorted out, because some music just doesn't sound normal like that. Various parts of the music do not sound correct as all parts of it are the same volume and the more instruments etc.. there are playing together at a certain volume, the quiter the overall sound will adjust. It doesn't sound right.

I didn't notice this problem with previous pairs of headphones and I can't continue to enjoy listening to the music if this continues to occur. These weren't very cheap either. So yes an unusual problem but hopefully someone will know how it could be sorted!

Edit: I was wondering if this issue is what is known as "volume distortion".

Could be a few things:

Some new headphone/earphone devices are coming equipped with "hearing protection". For example, a new iPod won't let you play more than xx minutes of music above a certain volume each day...or something to thtat effect. As I understand some of these, they do not permit the user to over-ride the "protection".

Far as I can tell, the real "protection" they are attempting to provide is from lawsuits against headphone/earphone/audio device manufacturers.

Your headphones may have something like that as part of the design. It may be something you can over-ride.

It's also possible your applications or drivers are "normalizing" the audio for that headphone for some reason, or it's just the normalizing has become more noticeable with that headphone when it wasn't so noiticeable with the other brands you've tried. It can vary depending on frequency response.

edit to add-
I also have an audio recorder that provides "compression". It automatically boosts the level of softer sounds, and reduces the volume of louder sounds. It's primarily for recording meetings and lectures, where sound levels of all frequencies can vary widely, and the intent is to provide a more uniform volume level of all the talking going on in the room, whether it's the microphone amplified lecturer or some one in the audience asking a question. That feature is selectable by a switch on the recorder. Your headphones (or the transmitter) may have a similar switch hidden away somewhere. edit to add--on some products at the store, I've seen this switch labeled "AGC on/off" for Automatic Gain Control.