Bottlehead Forum
Other Gear => Speakers => Topic started by: Llewellen on April 08, 2017, 07:20:43 AM
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I have the original woofers and now have the original plans (thanks Doc). As I study the plans and think about matching the subs to my intended speakers, a couple of questions arise:
- if one wanted to narrow the pass band and lower the point at which the sub begins rolling off at the top end, say to 65Hz for example, how should the design be altered?
- what effect, if any, would there be from having the port firing down against a hard surface, such as a concrete patio slab or similar, and how high above the slab should the port opening be?
Thanks
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Doing that kind of change is pretty much starting over. Your best bet is to find an online bandpass subwoofer box modeler and try some different box designs. When you change one parameter lots of other things change and the modeling software will help you figure out the best compromises. The bottom vented port should maybe sit at a height that is at least equal to the diameter of the port.
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Thanks Doc, except I think that all of the T/S values for that original woofer are not included in the Valve article. Maybe they're lost in the mists of time :) Any approximations come to mind?
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That was 20 years ago. I can't even remember what I had for breakfast.
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OK, OK, it's simple and cheap so I'm going to stick with it as you originally designed, with the additional bracing (dowels) and stuffing discussed in subsequent Valve articles.
The intended speaker match has a published spec of 75-20K Hz for the driver and supposedly 60-20K Hz in the back horn box. You were working to a 75 Hz cutoff with the Superwhamodyne towers so this match might be close enough.
Thanks for the help Doc.