different sidebar for custom taxonomies

I want to have different sidebar for custom taxonomies. I already create sidebar.php and use conditional tags

my sidebar.php :

<?php
if (is_tax()) {include (TEMPLATEPATH . '/sidebar-tax.php');
}
else { include (TEMPLATEPATH . '/sidebar-default.php');
}
?>

but it’s not working. when i go to http://website/?mytaxonomy=test its still go with sidebar-default.php

in my sidebar-default.php i used dynamic_sidebar
<?php /* WordPress Widget Support */ if (function_exists('dynamic_sidebar') and dynamic_sidebar(1)) { } else { ?>

also in my sidebar-tax.php
<?php /* WordPress Widget Support */ if (function_exists('dynamic_sidebar') and dynamic_sidebar('Taxonomy Sidebar')) { } else { ?>

Please help me to fixed the problems.. thanks!