Wyred 4 Sound DAC owners

Fast or slow rolloff?

fast is the default setting, which is how I've used it till today. Switched to slow. Damn! 
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so tell me what you like better about the slow roll off.  I have a Wyred dac 2 dsd and Femto clock upgrade and I am interested in your observations.
I too have the Femto clock which I think is a very good thing

slow = more air;  the highs just float
I have the W4S DAC.  I'd like to here more about this.
It's part of the menu options- it's there for you to try
On the W4S DSD SE, I also prefer the slow setting and feel the soundstage is more open and highs generally better.   However, with DSD the default BW setting sounds best to me after much experimentation.