I can't wait to see the follow-up. Quite a few guys in the UK also watching.
I can't wait to see the follow-up. Quite a few guys in the UK also watching.
The body of the cabinet is now complete. This bugger is big and heavy. It is getting increasingly difficult to move about as I add mass to it. I am guessing that it will weigh in at 250 plus pounds when completed. Industrial casters will be going on the bottom for sure!
I have yet to build the exit section of the waveguide that assembles immediately below the driver bucket. There are also two stiffening ribs that fit between that and the back of the cabinet that I have yet to install.
In the above PIC I am about to secure the flexible MDF that will form the lower scoop.
Here is a closeup shot showing detail of the driver bucket. The driver baffle board will mount flush with the forward edge of the cabinet. A piece of 3/4 x 1 1/2 inch trim will wrap the front edge of the cabinet just as JBL did with their scoop cabinets.
I probably spent too much time 'futzing' with the body of the cabinet, but I wanted a nice square box with tight corners. I've still got a couple of days work (weekends??) before I am ready to load the drivers. I've ordered a gallon of primer. It's a big cab. Maybe that's not enough!
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Best Regards,
Carl Huff
Hi Carl.
Small progresses are better than standing still. Good job. Please have a look at Shorty's Waldorf and check how the front panel is recessed, allowing reinforcement strips all around. Do you think you'll be able to do the same on yours?
http://www.myspace.com/soundmanshorty/photos/33496214
Hello Lee,Originally Posted by Lee in Montreal
It may look like small progress but getting that cabinet square was an all day test of my physical fitness, patience and skill! Ha, ha ...
Yes! That is my intent. The recess that you describe will be created by the 3/4 by 1 1/2 trim board that I described in my previous post. The drawing that you sent to me did not include a trim piece applied to the forward edge. I thought that not having one might lend itself to splintering when the cabinets are being muscled about. I studied the online PICs of the Waldorf and JBL scoop cabs and saw that they all had a forward trim board (as shown in the PIC that you posted) that stands proud of the cabinet face. As result of seeing that I adjusted your drawing to include a trim board. I was sure to keep your overall dimensions and left all internal elements unchanged. The addition of the trim board to the face of the cabinet is the only change that I have made to the drawings that you sent me. I hope that you approve!
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Best Regards,
Carl Huff
The baffle is recessed by 1" and uses 1" x 3/4" extra framing. The total width of the frame becomes 1.5"
Lee,
What you proposed exposes the end grain and laminates of the plywood to potential tearing and splintering.
And here is what I proposed. The plywood edge would be protected from potential abuse. No big difference
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Best Regards,
Carl Huff
Both will work ;-)
Lee
Yea, I wouldn't have made the change if it were not for the crappy 'import' plywood that I am using for this project. This plywood seems prone to damage easily. It is much softer than what I usually buy for projects and as such is much harder to work with. I've learned my lesson. It's back to Baltic Birch for me!
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Best Regards,
Carl Huff
Carl, enjoying your progress & look forward to seeing the results
With the intention of simplifying the understanding of building a rear loaded bass horn, here are 4 simple formulas to help get a little understanding of the basic elements. There are more formulas, but it's a start to help understand how they work.
Fc is cut-off frequency
It has been a while since I posted anything. Altho obligations have slowed me I haven't quit work all together. Here is a recent PIC showing that I have the majority of the cabinet completed. As you can see the scoop flare and bracing are complete. The next step is to cut and apply the baffle board. I have two freshly reconed JBL 2240s on their way as I write this. They should arrive mid next week. This weekend will be about tidying up and applying primer to the box. Hopefully next weekend will the first round of tests and measurements using a pair of JBL 2240 drivers.
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Best Regards,
Carl Huff
Ah.... Look at that mouth. It's huge.
BTW Great job Carl. I like very much the double skinning around the rear chamber. Perhaps you could make some holes in the center section/brace.
I've thought about that. The reason that I haven't cut holes in that center section brace is that part of what I want to do is evaluate the possibility of having two different loudspeakers in the cab, in particular an ALTEC 604 duplex or PAS 15 inch coaxial next to a JBL 2240. I want to experiment with different sized rear chambers when different drivers are loaded. Perhaps I should drill the holes that you suggested but make myself a plate that could be attached to seal off the two compartments from one another when I get to that part of the experiment.
A while ago when I worked up the numbers for the optimum recommended rear chamber behind a single JBL 2240 the volume worked out to be roughly the volume now afforded by leaving that center section brace solid. What do you think?
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Best Regards,
Carl Huff
As far as I know, wether in a horn or bass reflex cabinet, you can't have two different drivers. Unless perhaps the only difference is the tweeter section. You'll be sharing the same "space" anyway as the horn path is common to both drivers.
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