Front panel edge rounding

[BrianGT]

I would recommend not to use the 1 1/2" radius it by hand. I find it to be quite unsafe. I picked up a $2 old craftsman router table at a flea market, and cut a larger opening it, and put a piece of plexiglass on top, and it works great on a budget.

Here is a picture of the top of the table:

The key to this bit is to take your time. If you try to go too fast, it can tend to chip off chunks of mdf. It also removes a lot of material, quite quickly. I am thinking about getting a variable speed box for my router.

I have bought a few bits from MLCS woodworking ( http://www.mlcswoodworking.com/ ) and the prices are good, and the bits seem to be of good quality.

--
Brian

 

[BrianGT]

bottom of table

--
Brian

 

[BrianGT]

It is also possible to do a large radius without power tools, as Bob Brines has done here:
http://www.geocities.com/rbrines1/Pages/PP_Construction.html
on step 12. It seems like it would take quite a bit of time and a decent hand plane.

--
Brian

 

[pinkmouse]

It seems like it would take quite a bit of time and a decent hand plane.

If you have a decent, sharp plane, you would be suprised how quickly you can do that sort of thing, especially if you cut most of the waste material away first on a table saw.

 

[BrianGT]

If you have a decent, sharp plane, you would be suprised how quickly you can do that sort of thing, especially if you cut most of the waste material away first on a table saw.

I am aware of that. I was implying that it would take a lot of time to follow the process he details on his webpage:

"I chose a 1 1/2" round-over. I started by making a template, easiest if you have a CAD program. I cut a 45 degree flat and then 22 1/2 degree flats using a hand plane. Next, I added more flats until I had seven equal flats. From there, 60 grit sandpaper finished the round-over"

This would take a considerably longer time to do then using a roundover, which would take a few minutes for one edge.

I borrowed a power hand planer from my parents, and I might try to make a large dual bevel, starting with a 1.5" roundover, as described in AudioXpress some time in the future.

--
Brian

 

[Bricolo]

what edges need to be rounded?

Only the bafle's edges? or rounding the other edges also gives a better sound?

bump

 

[GM]

The closer the cab mimics a sphere, the better. If that's too much effort, then at least it should mimc a hemisphere. http://www.o-d.co.uk/technested.html

As noted, you can approximate this by laminating or shaping wood, or you can mount the drivers on pillars and make a contoured 'baffle' by gluing on rigid foam and shaping/finishing it with shurform files/sandpaper.

Or you can do as I prefer and XO the LF low enough to a horn so that it's a non-issue.

GM

 

[Bricolo]

The closer the cab mimics a sphere, the better. If that's too much effort, then at least it should mimc a hemisphere. http://www.o-d.co.uk/technested.html

As noted, you can approximate this by laminating or shaping wood, or you can mount the drivers on pillars and make a contoured 'baffle' by gluing on rigid foam and shaping/finishing it with shurform files/sandpaper.

Or you can do as I prefer and XO the LF low enough to a horn so that it's a non-issue.

GM

Nice!

"J" is the best shape after the sphere.

But I wonder if making a cabinet like "J" but with the back side rounded improves something

 

[GM]

Right, since "J" mimics a hemisphere, doesn't it seem reasonable to assume that since spherical (A) is best, then shaping the rear of a "J" cab to be a like its front is mimicing a sphere, making it the best compromise?

GM

 

[faustian bargin]

i dunno, just judging from the curves on that site (and assuming they are accurate), adding bevels to the back would only give you diminishing returns, if any at all. i'd say if you're going to go to all that extra effort, it might be more useful to add a dual bevel to the front and leave the back flat.

again i refer to the audioXpress article, which is pretty well documented.

other thing is, seems like a square box might not be the best shape in terms of all that wave resonance stuff. but i could be wrong, i'm not a speaker builder, just a guy who reads stuff.

/andrew

 

[Bricolo]

i dunno, just judging from the curves on that site (and assuming they are accurate), adding bevels to the back would only give you diminishing returns, if any at all. i'd say if you're going to go to all that extra effort, it might be more useful to add a dual bevel to the front and leave the back flat.

again i refer to the audioXpress article, which is pretty well documented.

other thing is, seems like a square box might not be the best shape in terms of all that wave resonance stuff. but i could be wrong, i'm not a speaker builder, just a guy who reads stuff.

/andrew

but a rectangular box housing a folded & tapered transmission line is nice, in terms of resonance

 

[GM]

i dunno, just judging from the curves on that site (and assuming they are accurate), adding bevels to the back would only give you diminishing returns, if any at all.
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They're close enough for illustrative purpoes, and diminishing returns. It just depends on where you draw the line at 'good enough'.
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>other thing is, seems like a square box might not be the best shape in terms of all that wave resonance stuff. but i could be wrong, i'm not a speaker builder, just a guy who reads stuff.
====
Mine's primarily from experience, and you're right, if the transition from hemi to spherical isn't very smooth. This is why flat baffles should be done in either an acoustic or golden ratio, with the driver(s) similarly offset, so that all the standing waves can average out, thus minimizing the peaks/nulls amplitudes.

GM