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Old 7th May 2004, 02:08 AM   #1
netgeek is offline netgeek  United States
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Default Linkwitz transform in vented enclosure??

Has anyone tried using a Linkwitz transform on a sub in a vented enclosure? I'm sure you'd have to come up with some extreme LF cutoff that was set above the "meltdown/destruct" limit - but might there be advantages?

I was thinking about a super-cheap (and limited SPL - say a target of 100 dB MAX - more likely around 85 dB or so) subwoofer using something like the Dayton DVC 10" - PE #295-485. Using WinISD and playing around it seems that this could be done in a sealed enclosure - with Linkwitz - by adding about 12 dB of gain for an F3 of 24Hz. Net requirement ends up being around 88 watts - considering that anything above 100 Hz can reach 100 dB with only 5.5W input.

For some reason these numbers just don't look right. If I input 88 watts to the thing in a sealed enclosure @ 25 Hz, do I exceed the excursion limits (xmax = 6mm)??????

So, I was wondering what happens if I use a vented - but undersized - enclosure (let's say 1.5 cu. ft.) to reduce the excursion, but compensate for the LF roll-off with the Linkwitz transform? Ridiculous idea?

The Dayton DVC is only US$27 so it wouldn't kill me if I fried one or two experimenting - just wanted to see if anyone here had some input beforehand.....

Thanks,
Bill
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Old 7th May 2004, 01:12 PM   #2
Did it Himself
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You can do Linkwitz with a vented box, but it's not a trivial task. Sizing the box is not easy. Fitting the Linkwitz transform curve is very hard indeed. Accommodating the port requirements is tricky. You won't get 100dB from a 10 incher even with room gain.

Doesn't your speaker modelling software show you max a SPL graph with corresponding power input? You can use this to determine if the 88W will be too much.

Consider a 6th-order system. Nice efficient ported box with a little EQ and sub-sonic protection. 100dB may be achievable with that.
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