Troels gravesen PMS: riddle this for me

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
My PMS speakers are almost ready bar the crossover and one little thing that i cannot solve:


-------------------What the hell is the size & lenght of the middle enclosure went?----------------------


"Two vents towards the floor will be placed on each of the ÒwingsÓ and IÕll use PVC tubing of 4.7 cm internal diameter. From a ~38 litres cab and a vent tuning of 38 Hz, the vents should be 80 mm long. IÕll cut them 120 mm to enable some fine-tuning after driver installation.
The mid cabs are 4.3 litres net volume and the vent is a 40 x 70 mm PVC tube with an ID of 37 mm. Actually this vent doesn't do much in the traditional way of a vented box. I made it because the mid shouldn't be in a closed box. I don't dig closed boxes for larger midrange drivers! It kills the midrange. Actually I have a small amount of wool material stuffed in the vent, so it's function is more like an acoustic vent. So take your pick."


Is there some kind of simple communication problem as english isn't my native lanquage or why i can't understand this: "the vent is a 40 x 70 mm PVC tube with an ID of 37 mm"?

So what is the vent lenght??? internal size is 37mm, right?
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.