Three questions about turn resistance, damage reduction and SR

[Tarril Wolfeye]

Is turn resistance cumulative?
Damage reduction can be Su or Ex, but which?
Why doesn't the spell Lower Resistance (from Draconomicon) work on Undead?

The long version:

If you combine turn resistance from two sources, e.g. racial and the spell "Armor of Darkness" from Dieties and Demigods, is this cumulative or do you just use the better one?

In the back of the DMG damage reduction is said to be "Ex or Su", but I can't find when exactly it is one or the other. Are there any rules for this? This came up when some monster with DR 10/- ended up in an antimagic field.

The spell Lower Resistance from Draconomicon specifies a Fortitude Save and doesn't work on objects making Undead immune to it. Why? I'm thinking this should also work on objects and undead (and constructs) as it's not dependent on any metabolism. Either that or it should not be a Fortitude Save. What do you think?

 

[hong]

If you combine turn resistance from two sources, e.g. racial and the spell "Armor of Darkness" from Dieties and Demigods, is this cumulative or do you just use the better one?

Since no type is mentioned for the turn resistance, I'd be inclined to let them stack as an unnamed bonus.

In the back of the DMG damage reduction is said to be "Ex or Su", but I can't find when exactly it is one or the other. Are there any rules for this? This came up when some monster with DR 10/- ended up in an antimagic field.

No hard and fast rules exist. I'd treat DR /magic or /alignment as Su, and anything else as Ex.

The spell Lower Resistance from Draconomicon specifies a Fortitude Save and doesn't work on objects making Undead immune to it. Why? I'm thinking this should also work on objects and undead (and constructs) as it's not dependent on any metabolism. Either that or it should not be a Fortitude Save. What do you think?

Seems like an oversight to me. I'm not sure why they chose a Fort save in the first place; Will would seem a more intuitive choice.

 

[Tarril Wolfeye]

Since no type is mentioned for the turn resistance, I'd be inclined to let them stack as an unnamed bonus.

You could also say it's a turn resistance bonus to HD, which would make it named and not cumulative.