# PR tuning

Discussion in 'Home Theater Projects' started by Lewis Besze, Oct 25, 2005.

1. ### Lewis Besze Producer

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I've heard that there are simulation programs out there to determine the weight that needs to be attached to the PR to tune it to a certain FR.Is there a simple math to calculate it, based on internal volume and equipment displacement?
Thanks!

2. ### Rory Buszka Supporting Actor

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http://www.stryke.com/prfaq.htm
http://www.stryke.com/diyprdesign.htm

It is based on the density of air. Calculate the necessary port in a box program, with the port having the same diameter as the PR. Then, calculate the volume of a cylinder having the same diameter as the passive radiator, but with a height equal to the length of the port that is recommended by the box program, and then multiply that volume by the density of air, and you get the mass necessary for the passive radiator. Keep in mind these things:

1. V = pi*((d/2)^2)*h for a cylinder. d is diameter, and h is height, which in this case represents the length.
2. If the port length that the box program gives you is really ridiculously long, don't be afraid. The AE Speakers 1400g PR represents a 46-foot-long port.

What driver are you looking at using?

3. ### Lewis Besze Producer

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This is an existing box with a Blueprint 1503.It was built by a friend a few years ago and he tuned the PR's[Adire 15"x2] to 18hz, he made it that I could add or remove washers to tune it myself. Anyway a recent storm here induced a power outage[cycle], when the sub was on, powered by a Crown CE1000, there is also a BFD in the chain which is known to create huge thumps when turned on/off, combine that with the rapid powercycle and you get the picture. Interestingly the driver suffered no damage what so ever but the 2 pr's were destroyed at the spider beyond repair.
In a stroke of geniuos I throw them away withought removing the wegths that was used to tune them, so I don't know how much it was now that I need a replacement.

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