The ventilation box is not noticeably quieter than...

The ventilation box is not noticeably quieter than the Itho ventilation box from 1992, which still worked well.
Kemkes hung the new box transversely, for no reason.
The old one hung neatly straight (see the edge of the box in the photo).
Kemkes returned because the canals were not cleaned as promised.
Conclusion: Using a glove and the vacuum cleaner myself would have given a better result and saved me E.432.00.