Build your mockup to the correct interior dimensions and fill with plastic peanuts to determine the volume. I gave up trying to calculate the volume and took that "empirical" path....Originally Posted by John W
Build your mockup to the correct interior dimensions and fill with plastic peanuts to determine the volume. I gave up trying to calculate the volume and took that "empirical" path....
You can do that... or if you would like send me the dimensions. I have software that calculates this sort of stuff quite painlessly... well it was painful to buy, but...
Widget
Yes, in that range. You need to nail down the volume to get accurate estimates on the port dimensions.
In any case, it's not critical if you don't have the requisite depth. Elbowed ducts work fine, too.
Also, I've found that heavy fill is easier using rear porting. Don't have to worry about avoiding the interior port ends with the insulation that way....
I can't find my documents on the 240Ti and 250Ti right now but I think they were ~ 3.5 cu ft @ ~ 30-32 Hz and 4.0 cubic feet @ ~ 28-30 Hz respectively. The Citation 7.4 box was ~ 3.4 cu ft @ 28-30 Hz. The 1400 Array box was ~ 3.2 cu ft @ ~ 30-32 Hz.
I currently have four LE14H boxes, two ~ 2.0 cu ft @ ~ 32-34 Hz as well as two stock 240Ti boxes. I personally prefer the 2.0 cu ft boxes due to their increased portability but that's my personal preference. They're "bookshelf" size as opposed to "floor standing" size. At any rate, you should see a pattern here - 1.5 to 5.0 cu ft tuned in the 28 to 34 Hz range - nothing has really changed since the 70's in that respect. I personally feel that the 250Ti box is the largest practical volume with the lowest practical tuning - that's just my opinion.
I would not recommend trying to make long diagonal cuts on a table saw. Use a straightedge guide clamped firmly in place. Since I have a jointer (and before that a Stanley Bedrock jointer plane) I've made my own out of wood in the past, but they tend to move in the weather and need to be retrued. I just bought a commercial one the other day. It's made of extruded aluminum about four inches wide and has three ridges, one at each edge and a third about half inch from one edge. It's an improvement over angle stock because it has a lower profile, and I've also found that angle stock is not necessarily straight. It comes in two pieces, each a little more than four feet long and they can be splice together end to end with a coupling piece provided. Very neat and very rigid in either configuration. Two small C-clamps included. Price was in the $16-17 range.
The tricky thing about making beveled cuts with this kind of rig and a portable circular saw is that the offset distance you need from the cut line to the guide changes with every change in the angle of tilt. Using scrap ply of the same thickness, adjust your saw, trying your bevels, until you have the tilt right and then clamp your guide to a piece of scrap; make a cut with the chosen tilt and measure the offset.
David
These are well underway now.
I ended up making a hinged angle jig for the table saw to cut the triangles. This isn't my idea they make commercial versions of these. It worked very well.
The correct angle on the jig is definitely the most critical measurement. I layed out the cut full size on the panel, then established the angle on the jig. Using my cardboard mockup I also captured the angle needed to butt the panels at the correct angle for gluing. Width and height of the starting rectangle where a couple inches large to start, then I screwed the jig directly to the panel, set the fence and made the cut. Then, depending on what was already established, I would either cut the triangle to the exact width or height needed. If the jig angle is set correct, once you cut width, height follows. In practice, with all the angles involved be prepared to be somewhat flexible on one side of the triangle.
Another trick was that for the back side I needed compound angles equally centered, so I cut one side of both speakers, then used the cut-offs from these to establish the angle on the other side.
I used hardwood for the narrow strips on either side of the front panel for added strength and ended up going with the 2 – 2 inch ports. According to WinISD, this setup is a good compromise between port length and air-noise at the ports.
The boxes here are getting ready for painting. I used some body glazing to fill in any of the small cracks remaining after glue up.
The paint I am going to try is called Dura-Tex. It is on order and should arrive at the end of the week. http://www.acrytech.com/DuraTex.htm.
And, AND,
... how do do they SOUND?
[May have to pad down the HF a bit....]
You using stock NL200t3 crossovers, or some you built?
And 16-Ohm HF drivers?
(((mmmm))) how cool is that!!!
John W - nice work, thanks for the photos of the angle jig and the cabinets.
I love the way music makes me feel.
The current crossovers are home built NL200T3. They are sort of pieced together with inductors from other crossovers and are padded down about 3db on the top. Initial tests where very positive. I was suprised at the depth of soundstage from these horns and the bottom end is quit nice too. I want to work out some of the kinks and then order some parts for a charge coupled version.And, AND,
... how do do they SOUND?
Try this 16-Ohm version with your "J" drivers, maybe:
http://audioheritage.org/vbulletin/s...276&#post71276
More results with 2426J:
http://audioheritage.org/vbulletin/s...3-16#post71329
And with four 2425J's (two of them apparently defective) two posts further down.
I didn't bias the cap in the LF in my "economy" implementation there....
About $75 apiece to build, complete with quality binding posts and lithium battery in holder.
Parts list for the 8-Ohm version is here:
http://audioheritage.org/vbulletin/s...214&#post70214
Substitute the requisite different parts for 16-Ohm version. I used two 7-Ohm Mills in series to make up the 14-Ohm resistors. Percy carries the 14, but he has a $25 minimum....
Thanks! that's perfect. I was going to make it my weekend project to wade through the quick and dirty thread for the optimal crossover, but looks like you saved me some time.
What's your source for Zilchpins, those look pretty handy?
Those are Vector T9.4DP, discontinued 20 years ago and the tooling scrapped. Their big plus is the bottom end is bifurcated and makes wiring the back side of the board simple.
Alas, I'm out of them now, and using the smaller Vector breadboard pins instead. May have to tool up to make a bunch of the originals. I threw out a bag of thousands of them in a purge of old stuff here about 5 years ago.
If you root around you local electronic surplus and old-school parts stores, you might just luck onto some. PM me with seller contact information if you find some, please....
Nice work John...I like the "edge" design work. Looks like you physically aligned the top plates of the drivers(?) like the 4430.
Edgewound...JBL Pro Authorized...since 1988
Upland Loudspeaker Service, Upland, CA
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