Madison Knight-12 Sealed Subwoofer - Page 2 - diyAudio
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Old 26th February 2007, 06:24 AM   #11
ScottG is offline ScottG  United States
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Quote:
Originally posted by maxdd_nj
Is this the correct part (Parts Express #: 296-546)?
http://www.partsexpress.com/pe/showd...number=296-546

Can I still use my dimensions (about 2.025 cu. ft. before the fill and brace) if I line my rear baffle with the 3 Scan Speak resistance vents?

---or---

Should I increase the depth to 20" which gives me an internal area of about 2.998 cu. ft. (before adding fill and the center brace) & also use 3 flow resistance vents per enclosure?

ScottG - Thanks for your help!
The more space the better the extension - even with a large increase in volume you will be lucky to get more than about 30 Hz at any appreciable sp-level. Less volume results in less extension and a higher peak in the midbass/lower midrange (even with an aperiodic vent).

While it certainly isn't a "sub" - used properly it can augment your Fostex's rather nicely, making for a FAR more dynamic sound. Additionally it free's up your fostex for more unusual uses. Perhaps open baffle like this:

http://www.arduman.com/aa/Sayfalar/peder/speak.htm

As to the parts express part:

Yes, those are the vents. Have some myself. The "surface area" of the vent is more about the driver surface area than volume. Really though, you could easily fabricate this yourself - there is no need to have a round vent. Some quarter round trim in a rectangle "frame" with some stiff fiber glass insulation panel and some pegboard covering to keep it in place would suffice. You could even do without the trim if you route the edges of the hole you make in the back cabinet panel. In fact it could be a superior solution (especially considering that the scan speak vents do have a bit of "depth" to them that could become somewhat resonant.

Your welcome for the help.

Oh, and you might want to try it with and without using fiber fill/insulation. Particularly concerning the walls of the cabinet.
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Old 26th February 2007, 08:14 PM   #12
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Default v_3.0

ScottG, I made the changes you mention...let me know how this looks.

http://www.maxdd.com/_diyaudio/Maxdd_bass_v3.pdf
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Old 26th February 2007, 11:42 PM   #13
ScottG is offline ScottG  United States
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..put an extra "run" of holes top and bottom (i.e. 5 "lines"). If you can make the cab. larger great, if not - thats OK too.

Good luck, looks like you are just about there.
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Old 27th February 2007, 02:39 AM   #14
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Default best material to cover-up an aperiodic vent

I made the cabinet 4-inches taller (the internal volume is now greater than 3.5 cu. ft.) and I added 2 more rows of vent holes to the rear baffle.

Anyone want to recommend the best material to use to cover-up the vent holes? I have some cotton felt left over from a previous project so I'll probably use that but I read here about others who used dense fiberglass insulation.

I updated that last PDF for all who want to build, comment, tweak.
http://www.maxdd.com/_diyaudio/Maxdd_bass_v3.pdf

I'll wait awhile before I buy the bb-ply and start the build incase anyone wants to chimes in. I'll post photos along the way. Thanks for the help!
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Old 1st March 2007, 10:13 PM   #15
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No further advice?

Everyone agrees this design is right on track and can't be taken further? There's no better enclosure to build for the Knight-12s to get my desired results (great sounding, fast, musical bass to complement a fullrange driver)? Or am I so far off no one wants to go there?

Anyhow, some last minute questions before I start buying wood and bust out the saw.

Does it make sense to have the driver centered top-to-bottom on the front baffle or should it be moved either up or down?

Would I get better results using the 3x Scan Speak flow resistant vents per enclosure than with the custom 1/4" holes and cotton felt (like in my drawing)? Are the 1/4" holes too big/small a diameter?

Does anyone know of a speaker building software package that runs on a Mac (latest OSX)?

Thanks everyone.

Max
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