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-   -   Troels gravesen PMS: riddle this for me (http://www.diyaudio.com/forums/multi-way/101118-troels-gravesen-pms-riddle-me.html)

matsuru 2nd May 2007 12:16 PM

Troels gravesen PMS: riddle this for me
 
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?

Sonusthree 2nd May 2007 12:22 PM

I think he is saying that the port is:

70mm 'vent length'
40mm outside width (external size)
37mm inside diameter (internal size)

Regards,
Martin.

matsuru 2nd May 2007 12:28 PM

Quote:

Originally posted by Sonusthree
I think he is saying that the port is:

70mm 'vent length'
40mm outside width (external size)
37mm inside diameter (internal size)

Regards,
Martin.

Sound feasible, thanks i'll do that and email with troels if there seem to be problems with middle range.

gcolnaghi 5th January 2008 01:45 PM

Sorry for this "stupid" post but i am quite new in speakers DIY ... What about the positioning of this vent ? Is it external (towards the back panel) ??? or internal (towards one of the mid cab sides) ??? thanks in advance Gio


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