Anyone add more isolation to closed headphones?

[gustav29]

I have a pair of Beyer DT831s and 770 pros. I can still pick up a lot of outside noise on them, and want to add more isolation to them.
I also tried a pair of AKG 271s and found that I could hear a lot of outside noise on them.
Has anyone successfully modified their closed headphones to add more isolation to them?

Thanks in advance for responses.

 

[KT88]

One of the side effects of the Blu-Tak mod I have mad with my A900's was better isolation. Now that I have taken the Blu-Tak off, its very noticeable.

 

[gustav29]

What did you use to make them more closed?

 

[KT88]

Blu-Tak and some cotton, the Blu-Tak made most of the difference. Notice, it will also change the sound of the headphones. I liked it, maybe you wont.