PDA

View Full Version : A question regarding bass port tuning.



twelvebears
21-06-2009, 15:34
I'm sure there won't be a simple answer to this question, but for an enclosure of a given size, with a port of a fixed diameter, what would the effect be of varying the length of the port?

Obviously it changes the frequency to which the port and enclosure is tuned, but is there a general rule of thumb which says short port (of a given length) is tuned to a higher frequency than a longer one?

It just seems to me that with a sliding sleeve within a round port (made of say a piece of rolled sheet plastic), it would be relatively easy to alter the length of the port and play around with the tuning frequency.

DSJR
21-06-2009, 15:50
You can certainly do that, but it wouldn't hurt to contact the driver manufacturer giving the volume of the enclosure and diameter of the port "hole." They may, if they're a friendly lot, be able to give suggestions of the tube length. There are so many parameters to do with the setup of the driver-damping etc which have an effect.

You could even try an IB prospect with no port at all, which may give an extended bass which gradually rolls off quite early. Tuning the port gives a lower resonant frequency below which the bass plummets in level - all horses for courses.

This really is an area where objective science can give a series of calculations as to what the results are likely to be, but obviously listening will tell you which compromise is the best one for you - Alan Shaw of Harbeth is a firm supporter of CAD techniques to get the basics right, but then he spends months fine-tuning to get the sound he wants. He seems to do a good job IMO..