Headphone Isolation question

I can't seem to find an answer to my question. I have searched the internet, called Sweet Water, the Guitar Center, Pearl cooperation of America, and Beyerdynamic corporation as well as posted this question on the pearl forum. All I have gotten so far is referred to another source.

I am hoping someone on drummerworld may know or have some personal experience with the Pearl PDM-250 headphone.

http://www.pearldrum.com/CMSPages/GetFile.aspx?guid=227e895b-97af-4c21-a24d-0d3ec132c381

Back to the problem.

I have cross referenced the spec and other details of the Pearl PDM-250 with the Beyerdynamic 770 Pro. They appear to be the same headphone. They even weigh the same.

The one difference is Pearl PDM-250 claims 35db isolation and Beyer 777 Pro claims 18 db isolation. Now the Beyer 770m for drummers claims 35 db isolation, but the Pearl PDM-250 is more like the 770 Pro than the 770m.

The Pearl PDM-250 and 770Pro both have the same ear pads and bass reflex openings, which reportedly sacrifices db isolation while adding better sound quality. The Beyer 770m for drummers has a different ear pad and lacks bass reflex to achieve better isolation but sacrifices sound quality.

Can there be a 17 db difference between the Pearl PDM-250 at 35db isolation and the 770 Pro at 18 db isolation when they appear to be the same headphone?

I was all set to buy the Pearl PDM-250 when I noticed the 17 db discrepancy. Sound isolation is important for my purpose but getting better sound quality is a bonus. If I cannot get this puzzle solved, i will just buy the 770m, but I like the features of the Pearl PDM-250 better, but I am not willing the sacrifice the isolation.

Thanks

One reason for the discrepancy could be Pearl's figures. Beyerdynamic tend to give an average -dB reduction across the whole range (20Hz-20KhZ). Pearl might be quoting the maximum -dB reduction at one specified frequency.

Why don't you check out these:

http://www.gk-music.com/ultraphones.htm

These are the GK Ultraphones developed by Gordy Knudtsen, who's a professional drummer too. I love these things. He takes the Peltor shooter's earphones, and installs the Sony MDR-7506 drivers in them. I can actually mix a band from behind them wearing these earphones. These are awesome.

+1 on the UltraPhones, I've used them exclusively on stage and the studio for years.

Bermuda