Effect of enclosure volume deviation on vent tuning? - diyAudio
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Old 6th January 2007, 04:30 PM   #1
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Default Effect of enclosure volume deviation on vent tuning?

Hi everyone,

I have a Peerless 850146 driver in a 70.3 L sealed box, but I want to change it into a vented enclosure, if possible.

The problem is that the box is a bit too small for a SBB4 alignment. According to the design charts in Dickason, the volume needs to be 78.3 L (Qts = .35, alpha is 1.84 assuming QL of 7 from the design chart, Vas = 144 L).

So my questions are: what would be the effect of just using the slightly smaller volume, assuming I calculated vent length based on the actual enclosure volume? Would it be disastrous? Or alternatively, is there any way that I can artificially increase the box volume, or are there other design tweaks that would be helpful in this situation? (I know that for a sealed box, adding stuffing increases the effective volume but I don't think the effect is the same with a vented box). Any help or suggestions would be much appreciated.

Thanks everyone
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Old 6th January 2007, 05:02 PM   #2
Ron E is offline Ron E  United States
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the ~10% volume difference doesn't matter much - the vent output will drop this much: dB=20*log10(70/78)

Just do it.
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Old 7th January 2007, 10:18 AM   #3
Geoff H is offline Geoff H  Australia
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As Ron says, just do it.

The smaller volume will increase the res freq of the enclosure. You have lowered it back by adjusting the port length. The result is you will be somewhere between two alignments.

You will still get the lift in the bass, with a faster roll off, compared to sealed. If it gets lumpy, you can dampen the port, or block it up again.

Geoff.
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