Mike Keith

Maelstrom Sonotube with closeable Port Valve finally finished!

I posted about this subwoofer project earlier this year with some pictures of the construction and a description of an idea for a closeable port. So I went on a journey to have a Port Valve turned from Oak. Well the guy who was going to do the turning gave up on me so I went and bought a lathe and did it my self. I’m actually glad I got the lathe, beside it being a lot of fun I was able to get the valve just the way I wanted it and the valve seat fits so tight that I will only need a thin gasket to finish the seal, so I’m very happy with the functionality of the entire Vale mechanism, it works very smooth and only a few twists of the knob and the Valve is closed very tight.

Besides the 5 month delay to get an acceptable Port Valve turned the project so far has taken about 300 hours over 4months and cost about $1200 US for each of the 2 Maelstrom 18” Sonotubes. I still have a few details to finish but this one is ready to go into the listening room. Next I will silkscreen the plate behind the Valve knob with a placard that will show the “Open” and “Close” position, and a felt gasket on the valve seat to complete the seal. The prototype worked very well so I’ve already had many hours to listen to a working version of the port valve in a real world situation, and it does work very well to tighten up the bass when the valve is closed, pulse it’s somewhat decorative and functional as a display shelf. Now all I have to do is fix all the rattles in the house that just one of these has brought to my attention. Hopefully early this New Year I will have both subs in the listening room and have the BFD E.Q. set up properly.

Here is a link to another site that the pictures are posted at.
http://www.diyaudio.com/forums/showt...421#post292421

TimForman

I remember when you first proposed the idea. I'm very impressed with your perseverence.

My hobby site
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Wayne Ernst

Very nice work. Very nice.

\"My reality check ... just bounced\"

Jack Gilvey

I love it. You are one talented MF.

dave alan

Unique, beautiful, Brutal and versatile. Drink it up, it don't get better than that!

Simply excellent work.

Mike Keith

Thanks guys, I owe a lot to this forum where I got all the basics and inspiration to do a Sonotube, at first I thought a Sonotube would be too ugly and plain for my taste, and after many prototypes I ended up with a port sticking out which I didn’t like, but it sounded better than the others which were larger and had a flush port, so I just tried to make this protrusion to my advantage and dress it up a bit.

I’m very happy with the sound but integration into my system will take some time and I still have to make many mods to the original prototype so it will be identical to this one, then I have to shoe horn both into my 14’X15’ listening room that already has 7 speakers. This would not be possible if I were married, I just purchased a Mackie 1400i that will supply 700W per channel to these subs and I already have 1600W for the rest of the system (all Active) and I still have to wade thru Tony Gomez’s PEQ program to set up my BFD. I may not need the 4 Aura bass shakers in my couch any more, either way I think I should have enough bass to suit my taste for now.

Thanks to all who helped me directly and thanks to the entire community which has made this project possible due to the vast resources and knowledge available here.

DanWiggins

Mike,

That is truly a work of art. And quite creative, too! Kudos for one of the coolest cabinets I've ever seen!

Dan Wiggins
Adire Audio

Mike Keith

Thanks a lot Dan.

Also I'm trying to use Tony Gomez's PEQ spreadsheet and I noticed it has all fractional values for the test tones, do I need to generate all these tones or can I round off to the nearest HZ? Also where can I find a tone generator that will do fractional frequencies like 22,4 HZ?

Should I do one sub at a time or both?

How do you get the PEQ program to plot a graph from your entered "Raw SPL" values?

Thanks for any help.

Mike Keith

I just got some correction values entered into the BFD for Music "vented" and "Sealed", OOh the Behringer is a marvelous product, boy did it shape things up, of course I also had to do some vibration control on the windows and doors, but it's night and day different, and now when I close the valve and use the proper correction the bass really comes alive, in fact I might have to tune it down a bit as it's far more tubby then with the vents open. I have too many adjustments and too many variables this might just drive me crazy, I used all 12 filters on the sealed correction just to get it within +/- 3db.

Mike Keith

Here is a link to a .xls plot of my final room response for HT (valves open) both subs together. If there is another way to post graphs I would sure like to know, this is a real PIA, why won't this forum add picture upload capabilities. Thanks Anthony Gomez for this excellent program for setting up the BFD.

http://www.diyaudio.com/forums/showt...018#post299018