I was able to listen to the GMP 435 S thanks to the ongoing loan program in Head Fi. I received the cans on January 8, 2010. This is not my first experience w/ a German Maestro headphone, having previously listened to the GMP 8.300 D.

I do not know how many hours of burn-in this unit has; they should have plenty of burn-in since it has gone through several HF members before reaching my hands. Since I have no way of knowing and since I will be able to keep them for two weeks I will start by burning them in for 100 hours or so.

For now straight out of the box my initial impressions are:

Like:

- Very lightweight

- Extremely comfortable, plus it easily adjusts w/ the built in mechanism

- Very easy to drive, only 35 ohms

- Nice feature to provide extension relief w/ the built in coiled cable section

- Nice wide soundstage

- Nice thick and deep low bass

Do not like:

- Top end is way too energetic

- The mids are a bit thin sounding, lacks depth

Here are a couple of pictures:

More to come

Any more thoughts before you send them on to their next owner?

I used the velour pads after logging over 135 hours of additional burn-in. The velour helped tame some of the energetic highs but the bass lost some of its definition. These were not my cup of tea and if I needed an open can in the $350 range or less I would go w/ a K501, HD580/600, or a Grado RS-2.

Any comparisons by memory to the 8.300D?