Martin Poulin
48x 36x 24inchs about 500liters internal volume
X and Y axis brace done Z axis to be added
about 60 pounds each after first primer coat
48x 36x 24inchs about 500liters internal volume
December 2018
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Bass bin build in progress.
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4 x Fane Colussus Prime 15XS per box (sealed)
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24" x 36" x 48" (around 500 liters internal volume before bracing)
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Once drivers, bracing and stuffing added, I expect Qtc to be around 0.5 or even a tad lower. I like the sound of oversized boxes (technically called under-damped)
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¾” regular construction grade plywood with double thickness front and rear baffles and double bottom as well.
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Roxul SAFE’n’SOUND used internally
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¼” thick metal plate to finish top. (~60 pounds of extra weight)
1st failure... (or learning what doesn't work)
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Added 3 uni-struts in back, to reinforce the panel. Screwed them in and used PL adhesive. Barely doing anything as far as "knock test" goes.
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You win some… you lose some. Lesson learned.
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Added 1 more layer of ¾” plywood in back to reinforce it more and result are better. Paint is cheap. Will have to repaint the back again I guess.
In testing...
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Preliminary sound test were very promising.
~260 pounds each bass module :)
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Measurements to be posted...
DATS test of 4 woofer boxes. (series parallel connection)
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QES and QTS is higher than specifications due to internal passive resistors added in parallel to each 15XS voice coil (4 x 26 ohms)
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No resonance seen on the impedance trace:)
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Note that impedance doesn't go more than ~22 ohms VS 100 ohms for Fane graph specification.
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This is due to my 26 Ohms resistor in parallel to every driver tweak.
August 2019
I realized I never published the result of the bass bin. My bad.
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Of course, in a rental house with limited bass absorption and a severely vibrating wooden floor, doing measurements below 200 Hz proved very tricky. The kitchen pots and pans are dancing and 105 dB at 40 Hz excites huge room mode.
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The graph clearly shows 40 Hz peak. However, it is the room. Perhaps one day I'll go measure them outside and get the true result.
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Also, not having done a prototype prior to building those two fridge sized boxes, flaws were discovered and the enclosure could use a "MKII" upgrade.
I'm currently building a 3rd enclosure (for a center channel), and incorporating a few changes to see how much better (or worse) it’ll compare to the original MKI. Stay tuned.
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Nevertheless, below are some measurements with the microphone 6" away from the enclosure center (in the middle of the box, not middle of one of the 4 speakers, as this is about the worse measurement position.)
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Time domain measurement (step response) is a bit long to settle. This clearly shows the " air spring effect" of the big sealed enclosure. I may go Aperiodic loading in the future to improve that, it usually work great.
yellow= knock test fail red= weak bridge for strength
August 2019
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Rarely is anything is ever perfect on the first try :)
Modification time...
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My enclosure weakest spots is at the center, (see picture on left) where it vibrates the most and relies on triple internal bracing, reaching the rear wall to reinforce the front.
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The knock test everywhere on the enclosure is solid but not in the yellow area. It could use some improvement.
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I added a 32'' x 48'' sheet metal, 1/8" thick to the rear in an effort to solve the issue. ( single 4' x 8' sheet that I cut in 3 equal pieces).
Internal bracing connect the now much stiffer rear wall to the front baffle. What a difference that made, happy.
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The 32" x 48" sheet weighs ~50 pounds each...
My cabinets will now exceed 300 pounds each!
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I have three quad 15 inch bass bins, at 300 pounds each, my next move will be expensive...
June 2020
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​New center channel!
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-Bass bin is exact same dimension and construction as my original stereo pair seen above but I've painted it black. (used leftover paint)
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-Use same 1/4" thick metal plate mounted on top and metal plate on back for extra weight and incredible rigidity.
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-Used 4x Celestion FTR15 4080F as they had a wicked sale on them when I was shopping.
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-I did not finished the side perfectly smooth as my plan for the next audio room will hide the side anyway.
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-not weighted it but should exceed 300 pounds as well. The FTR15 driver is a tad lighter than the Fane 15XS prime as it has less excursion capacity.
Yet, it is much more that what I require, as usual, I maintained a margin of safety.
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You can see on top a 350 Hz Tractrix horn and the Radian 950PB mounted on it. Ready for the move in my new home.
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I should test them and post result one day.
I'm yet to listen to the Tractrix and the center bass bin...
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