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Old 2nd August 2007, 01:11 AM   #1
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Default PR tuned to different freq

When using more than one passive radiator in a cabinet would there be any advantage to tuning them to different frequencies to even out the impedance and response?

mike
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Old 2nd August 2007, 02:09 AM   #2
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I would say no. The air inside will take the path of least resistance. Your higher tuned passive would have more output and below its tuning it will be like playing below fb in a ported box. The heavier PR would not have much of a role in the design.

If you wanted to play with the idea you can look up an "abc" box which has 2 chambers with their own tunings.
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Old 2nd August 2007, 09:09 AM   #3
Svante is offline Svante  Sweden
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Default Re: PR tuned to different freq

Quote:
Originally posted by mashaffer
When using more than one passive radiator in a cabinet would there be any advantage to tuning them to different frequencies to even out the impedance and response?

mike

No.

Adding mass to one of two identical slaves is equivalent to having two vents "tuned to different frequencies"*. The thing is, there will still only be one tuning frequency, the mass of the slaves will act as one. The only effect of using different masses is that one of the slaves will move more than the other; this results in that Xmax of the (most moving) slave is reached at a lower level than necessary.

*By this I mean two differently sized vents in the same box, for example two of the same diameter but different lengths.
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Old 2nd August 2007, 09:19 AM   #4
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I don't know about passive drivers but if you have 2 ports in the same cabinet and one of the them is significantly nearer the floor than the other is often a good design principle to make the one nearest the floor slightly longer than the other or the other one slightly shorter than the one nearest the floor. This is done for level matching as the bottom port otherwise would have slightly higher acoustic output.

It's often seen in professional subboxes with a slot port on the top and bottom.
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Old 3rd August 2007, 01:10 AM   #5
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Thanks guys. Of course what you say Svante makes perfect sense. I should have thought of that myself.

mike
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