Using router, can I round front panel's edges AFTER the loudspeaker box has been built (ie: the front panel has been glued)? My plan is to round front panel's edges with 1.25 inch & 1 inch radius.
Router bits are damned expensive, so I think I'm going to round the edge (using appropriate router bits) later.
Thx!
Router bits are damned expensive, so I think I'm going to round the edge (using appropriate router bits) later.
Thx!
Two thoughts: If you are rounding edges to minimise diffraction, the rounding needs to be pretty dramatic -- just putting a small curve won't have much effect. And especially if you are rounding heavily, make sure that you aren't weakening the integrity of the front baffle/sidewall joint. If the whole thing isn't braced to compensate for loss of thickness, you might end up with more problems than you started with. I remember looking at a junked Infinity speaker, whose curved edges were made by cutting lots of slots in the particle board, and then just bending. Most of the strength of the joint seemed to come from the vinyl wrap. This can't be good.
A double check
I used a 1 1/4" roundover on one of my projects. I made the front baffle 1 1/2" thick, so as not to reduce the strength of the joint much. The look was good. I doubt that sound was effected much, however.
One thing to keep in mind, in case it hasn't already been mentioned, is that large radius bits have extremely high tip speed. It is best to use them in routers with variable speed. Honestly, I don't think much about using my 3/4" bit, but the 1 1/4" bit commands my respect. You may have to make a custom baseplate as well. Most routers don't have a 2 3/4" opening for the bit. Of course, even with the speed control, take no less than 4 or 5 passes (more depending on material) at increasingly smaller depth changes. I did 5/8", 7/8", 1 1/16", 1 3/16", 1 1/4" on MDF and the finish was very good.
I know the above is probably all obvious, but I'd hate for it to have been overlooked. Ruining a $$$ bit or a nice box makes for a bad day.
Sandy.
I used a 1 1/4" roundover on one of my projects. I made the front baffle 1 1/2" thick, so as not to reduce the strength of the joint much. The look was good. I doubt that sound was effected much, however.
One thing to keep in mind, in case it hasn't already been mentioned, is that large radius bits have extremely high tip speed. It is best to use them in routers with variable speed. Honestly, I don't think much about using my 3/4" bit, but the 1 1/4" bit commands my respect. You may have to make a custom baseplate as well. Most routers don't have a 2 3/4" opening for the bit. Of course, even with the speed control, take no less than 4 or 5 passes (more depending on material) at increasingly smaller depth changes. I did 5/8", 7/8", 1 1/16", 1 3/16", 1 1/4" on MDF and the finish was very good.
I know the above is probably all obvious, but I'd hate for it to have been overlooked. Ruining a $$$ bit or a nice box makes for a bad day.
Sandy.
You obviously have more practical experience with rounding than I have, and making the baffle thicker is obviously one way of keeping joints strong enough. But a thick baffle creates another problem, that of cavity resonance behind the driver. Rounding might be even more important here than on the front of the baffle -- any thoughts?
Not really
I don't really have much experience at all. . . I did it once so far and that's what I figured out on the way. If you're up for a quick read, I did a decent job documenting the speaker construction on my site. I haven't been pumping it much recently, as I am reworking it trying to make it more user friendly. Right now, the colors are pretty bad. What looks good after a few beers at night just isn't the same the next day. . .
Anyway, I did as you mention, specifically radiusing the back of the speaker cutouts as well. The pictures don't necessarily show it well, but I basically laminated 2 3/4" sheets of MDF, cut the holes out with the Jasper jig, made a few passes with the 1 1/4" cutter on the inside of the cutout until I got to around 7/8" deep. Including the flush mount depth, the back of the cone 'seems' pretty free from obstruction. However, after spending some time in aerodynamics, intuition I know is not always correct. But, it was a starting place for this project.
Anyway, good points to keep in mind, as you said. I've seen many people drastically open up behind the driver, just leaving meat around the mounting screws.
Sandy.
I don't really have much experience at all. . . I did it once so far and that's what I figured out on the way. If you're up for a quick read, I did a decent job documenting the speaker construction on my site. I haven't been pumping it much recently, as I am reworking it trying to make it more user friendly. Right now, the colors are pretty bad. What looks good after a few beers at night just isn't the same the next day. . .
Anyway, I did as you mention, specifically radiusing the back of the speaker cutouts as well. The pictures don't necessarily show it well, but I basically laminated 2 3/4" sheets of MDF, cut the holes out with the Jasper jig, made a few passes with the 1 1/4" cutter on the inside of the cutout until I got to around 7/8" deep. Including the flush mount depth, the back of the cone 'seems' pretty free from obstruction. However, after spending some time in aerodynamics, intuition I know is not always correct. But, it was a starting place for this project.
Anyway, good points to keep in mind, as you said. I've seen many people drastically open up behind the driver, just leaving meat around the mounting screws.
Sandy.
actually theres a pretty cool site i think the name is tape-ease.com where they sell varying radius corners...3" all the way up to 48" or some crazy junk like that...i've used the odd shaped 1/4 round ones for some dipoles and they came out impressively well...just took a little material off the bottom for a slight back tilt and had great success with them...
You don't have to use a router...
If you fit batten around the inside edges of the sides, then the baffle can be fitted to this, and doesn't need to be any bigger than the hole. You can then fit quadrant moulding round the baffle to give your rounded edge with a great deal less fear and more strength.
If you fit batten around the inside edges of the sides, then the baffle can be fitted to this, and doesn't need to be any bigger than the hole. You can then fit quadrant moulding round the baffle to give your rounded edge with a great deal less fear and more strength.
good reference
check out the feb 2003 audioxpress article, "Acoustic Diffraction: Does It Matter?" by James Moriyasu.
pretty good real-world analysis of diffraction effects of different baffle edge treatments, both radiused and beveled.
conclusion was, the higher the radius, the better. he went all the way to 4". that's a big radius, probably requiring bent plywood or a slice of sonotube with veneer.
small radii and any 45° beveled diffraction was not so good.
however he did a test of a dual-bevel design, which was *almost* as good as the 4" radius while at the same time being much easier to construct.
the dual bevel starts with a gradual 22° slope, then goes to 45° for the outer portion. i can't find what dimensions he used, but i imagine the total beveled width was 2" + 2" = total 4" wide.
no reason why you couldn't try refinements of this idea - triple bevel? 11° - 22° - 45°. ...etc.
hope that helps,
/andrew
check out the feb 2003 audioxpress article, "Acoustic Diffraction: Does It Matter?" by James Moriyasu.
pretty good real-world analysis of diffraction effects of different baffle edge treatments, both radiused and beveled.
conclusion was, the higher the radius, the better. he went all the way to 4". that's a big radius, probably requiring bent plywood or a slice of sonotube with veneer.
small radii and any 45° beveled diffraction was not so good.
however he did a test of a dual-bevel design, which was *almost* as good as the 4" radius while at the same time being much easier to construct.
the dual bevel starts with a gradual 22° slope, then goes to 45° for the outer portion. i can't find what dimensions he used, but i imagine the total beveled width was 2" + 2" = total 4" wide.
no reason why you couldn't try refinements of this idea - triple bevel? 11° - 22° - 45°. ...etc.
hope that helps,
/andrew
sianturi said:
Is the box built yet? It is unclear whether:
A) you already have a box built and want to add a bevel, or
B) were just planning to add a bevel after the box was built.
I realize A is far more likely, but you never know.
I have not done it this way, but following Faustian's suggestion of multiple slopes, I think you can add the multistage bevels with a table saw, assuming you can handle the piece or assembled box easily. After all, table saws do have adjustable blade angles.
Definitely recommend that you get a few pieces of scrap wood/particle board to try this out first!
After the multiple angle cuts, I imagine you could smooth them over with sandpaper to make it look good.
I could help you out with the math involved on the issue of how thick the board should be, etc.
New territory for me, but if the scrap boards come out looking good, it should be worth a try.
Bevelling both the sides and the top and bottom might create difficulty veneering, if you plan to do that.
Just to spitball this idea around a little, I suppose you could put succeeding layers of thin wood upon each other, each smaller than the last, to create the slope.
I made the following crude drawings to illustrate the idea. Of course, the illustration looks like you are taking a 15 inch baffle and mounting a 3" woofer on it, (not a likely design),
but it shows the principle.
I haven't used thin strips for bending or whatever, but I am told they are available from lumber yards. As to gluing them together without voids, and other issues, you would have to ask someone else. But it looks like it might be possible.
I made the following crude drawings to illustrate the idea. Of course, the illustration looks like you are taking a 15 inch baffle and mounting a 3" woofer on it, (not a likely design),
but it shows the principle. I haven't used thin strips for bending or whatever, but I am told they are available from lumber yards. As to gluing them together without voids, and other issues, you would have to ask someone else. But it looks like it might be possible.
Attachments
Head on over to the FRD group and download Paul V's baffle diffraction simulator for Excel. Everything you ever wanted to know (and more) about the effects of baffle size, shape, roundover, and locating the drivers on the baffle.
http://www.pvconsultants.com/audio/diffraction/downloadbds.htm
http://www.pvconsultants.com/audio/diffraction/downloadbds.htm
Re Raduis edges:
Most of the advice is good here. About router bits there are excellent asian brands that I use regularily. Locally branded of course. The radius idea of stacking up mutiple boards is frought with problems for people wthout the ability to do serious clamping. I have done radii up to six inches and at that size it does matter. But it is done with thin plywood in multiple layers and a form. You either need a positive and a negative form or a positive form and a lot of clamps. I have over 300 and there are some jobs where everyone of them was in service. I switched to a vacuum press and that simplified things a fair bit. The idea of planing a radius is good. I have done that countless of times and it works well with this importannt caveat. PRACTICE FIRST
Mark
Most of the advice is good here. About router bits there are excellent asian brands that I use regularily. Locally branded of course. The radius idea of stacking up mutiple boards is frought with problems for people wthout the ability to do serious clamping. I have done radii up to six inches and at that size it does matter. But it is done with thin plywood in multiple layers and a form. You either need a positive and a negative form or a positive form and a lot of clamps. I have over 300 and there are some jobs where everyone of them was in service. I switched to a vacuum press and that simplified things a fair bit. The idea of planing a radius is good. I have done that countless of times and it works well with this importannt caveat. PRACTICE FIRST
Mark
Rounding edges is important
I believe that rounding edges is very important. Imagine a soundwave, like a ripple in a pond. Now apply this to your speaker, the sound wave spreads out smoothly across the front of you speaker, if it hits an upraised edge on a driver, or the sharp edge of you baffle, it makes a secondary sound source. This can muddy your imaging, and cause ripples and minor cancelation in your frequency response.
One way of making rounded edges is to use some quarter round mdf stock for your edge. They come in all sizes.
The other one that you mentioned is to use a roundover router bit. The largest I have found is 1 1/2" round over bit.
I used this in a hand router, but it is really a shaping table bit, so it is probably not a safe practice.
Anyway here is an image of my router being dwarfed by the 1 1/2" roundover bit, it measures about 3 5/8" across.
James
I believe that rounding edges is very important. Imagine a soundwave, like a ripple in a pond. Now apply this to your speaker, the sound wave spreads out smoothly across the front of you speaker, if it hits an upraised edge on a driver, or the sharp edge of you baffle, it makes a secondary sound source. This can muddy your imaging, and cause ripples and minor cancelation in your frequency response.
One way of making rounded edges is to use some quarter round mdf stock for your edge. They come in all sizes.
The other one that you mentioned is to use a roundover router bit. The largest I have found is 1 1/2" round over bit.
I used this in a hand router, but it is really a shaping table bit, so it is probably not a safe practice.
Anyway here is an image of my router being dwarfed by the 1 1/2" roundover bit, it measures about 3 5/8" across.
James
An externally hosted image should be here but it was not working when we last tested it.
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