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| Re: skywave's 3Pi subwoofer build [message #74957 is a reply to message #74613] |
Sat, 15 December 2012 14:27   |
skywave-rider
Messages: 104
Registered: May 2009
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Wayne,
I finally found some Baltic birch in NYC. Very expensive, and I hope the shop can make straight cuts for me (they have a table saw, nothing fancier.)
Hoping not to bend your ear too much, I have a few questions.
The sub build is being done at my school as a Professor-financed student project. So we are not going fancy. I am a poor college professor! Hahaha.
I need it all done and integrated for a sound final exam exhibition and after party by Friday. So it has to be built in 1.5 days max.
But, in the room, a rectangular classroom, I want to use flanking subs. There is only one 3 Pi to be built. I was thinking of, if the wood was available, making 2 identical 3Pi boxes and loading the second with a Dayton classic sub and plate amp. (I already built this into a too small box for mediocre performance. What if I put the Dayton into that extra 3Pi box and tuned it for similar LF response?)
I understand that it's really the low mid-bass performance of the sub which is critical for flankers set up for stereo operation. So I don't know if it's worth a shot.
Another idea I had which would be less effective in eliminating the backwave rear wall bounce cancellation would be 1 mono sub between and behind the stereo mains, another at the mid point of an adjacent wall. I realize that would collapse the stereo image somewhat.
If I don't feel like spending the extra dough for the extra 3Pi box, I could borrow a Genelec sub from the recording studio. Don't know how that would flank with the 3Pi. It has some decent rolloff selections however.
Any good ideas here? Remember, the power requirements will not be much and excursion issues are unlikely.
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| Re: skywave's 3Pi subwoofer build [message #75039 is a reply to message #74958] |
Sun, 23 December 2012 11:31 |
skywave-rider
Messages: 104
Registered: May 2009
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Viscount |
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Just a quick note reporting that the sub got built with just enough time for the glue to dry and was immediately thrown into service:
(Pardon the hyperbole)
The Earpocalypse
Some things might be of interest to newbie box builders like mysef:
I followed Wayne's T-Nut Installation Instructions and those suckers went in like a dream. I used 2 dabs of Gorilla Glue on each T-Nut for mounting the LAB 12 driver. However, the 4 T-nuts used to mount the PE speaker grill used Phillips head screws, so I could not get enough torque to pull them in all the way. I got them half way and gave then 2 shots with a hammer. All seems well.
I live in Manhattan and have no workshop, so I and the students built the box in the hallway and a tech closet at school. That meant I had to find a lumber yard which had Baltic birch ply and could do straight cuts. Nearly impossible here. I finally found a little storefront wood guy who had a RATTY table saw; but he had a 5X5 sheet of wood, so I took the chance. His cuts were fairly consistent except for one panel which was a little small in one dimension. I only noticed it during the dry fit. Of course we went with it anyway. I have to say that is nice strong wood. It looks nice too. I laid out the panels so the edges could be seen from the top, which I like. If all the panels were the same size it could have been an acceptable "furniture" or home use build. I realized after seeing it together that the box is a rather nice side table.
We went glue and screw. I bought 4 big clamps because I wanted to use the no screw method, but now I know you need a nice work table, 1 million clamps and skill to do that. So, screw it.
We never had time to apply the truck liner paint I bought, so we ran it raw. I will paint it next week during my grading period.
I added wood blocks to the bottom and attached casters. I did not know if they would be rattlers, but in use, they were quiet and great for a mobile sub.
As a guy with little experience with a router, I am proud to say I made the port cutout the correct size to accept a snug press-fit of the tube, flush with the front of the baffle. I ran a bead of Gorilla Glue around it on the inside.
We loaded the woofer in after an overnight dry and immediately put it into service. It kicked ass. I ran it with another, smaller sub, both crossed low, in hopes of smoothing some modes. Because of time constraints, I was not able to do the set up with measurements. But tuned by ear. Placement of the 3Pi near mid point of a side wail, the other sub was offset mid point along the front wall.
One other thing: We used some 1 1/4" stock ripped into a right triangle for corner bracing in the cab. I literally found this wood on the street already cut like that. My bad is that I did not calculate how much volume that took up in the cab and adjust. I am pretty sure it would be negligible, though.
I'll post pics later.
I want to thank Wayne for providing this great design and all the help, tips, expertise and mega good will.
Thank you Wayne from my self and the student builders.
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