Addcondition In Search() Using >= Or <=

Hi everyone, I've been looking for a solution to use >= and <= in search(), I've found lots of workarounds about like and others...

But I need to add 2 conditions in order to filter a data in search() method, I've tried:

$criteria->compare('t.telefono',$this->telefono,true);
....

$criteria->addCondition('t.f1 >= :f1','AND');
$criteria->params[':f1']='1356994800'
$criteria->addSearchCondition('f2 <= :f2','AND');
$criteria->params[':f2']='1388444400';

But it doesn't work...

In SQL it would be :

where ... and t.f1>=X and t.f2<=X

Does anyone know anything about this?
Thx!