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Round over bits

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rajesh srinivas

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May 30, 2015
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hubli (karnataka)
I am in process of rounding over my inner bracing cutouts as well as on front mdf baffle,thickness 2 layers x 18mm (1.5in)

1. What size of bit is advisible for bracing and for front baffle,i read that for bracing a radius of 12 to 14mm is good and for front baffle min. 18mm (3/4in) radius required for effectly reducing defraction.

2.For front baffle should we roundoff all the 4 edges or only sides is enough.

3. How to roundover both sides of bracing,coz when we do one side its flatness goes off for doing the other side.

4. For rear speaker cutouts is 45deg chamfer or roundover (what size??) is prefered,to make the speaker breath freely.

Thanks
R/S.
 

sadik

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Jun 14, 2015
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970
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Vadodara
I am in process of rounding over my inner bracing cutouts as well as on front mdf baffle,thickness 2 layers x 18mm (1.5in)

1. What size of bit is advisible for bracing and for front baffle,i read that for bracing a radius of 12 to 14mm is good and for front baffle min. 18mm (3/4in) radius required for effectly reducing defraction.

2.For front baffle should we roundoff all the 4 edges or only sides is enough.

3. How to roundover both sides of bracing,coz when we do one side its flatness goes off for doing the other side.

4. For rear speaker cutouts is 45deg chamfer or roundover (what size??) is prefered,to make the speaker breath freely.

Thanks
R/S.

1. What is the thickness of bracing? If it is 11 mm use 6 mm radius bit, adjust the depth to 4 mm and do the rounding. If your bracing is 18 mm think then use 8 mm radius bit adjust the depth to 7 to 7.5 mm and do the rounding. We don't have to worry much about the radius of bracing.

2. Is this radius related to edge diffraction? if so I don't have a knowledge about it so cant comment on that, But I have seen many Hi-End speakers which are rounded only on 2 sides. Rounding on all 4 sides will be equally good.

3. For your 3rd Point i have answered it in my 1st point.

4. For rear speaker cuts, 45 degree chamfer will be best for the speaker to breathe easily.
 

Naveenbnc

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Oct 12, 2016
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Location
Hyderabad
Hey guys...generally what size (thread size) of screws do you use for joining speaker boxes??

The reason for asking is.... the head of the screw should go into the mdf, and still there should be space for round edges.

(I mean, the screw head should not expose out after rounding the edges. )
 

keith_correa

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Jan 17, 2009
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To what purpose are you rounding the bracing?

For the baffle, use the largest radius you can live with. The larger the better. Top and sides are effective, bottom is mainly cosmetic.

Rear of the cutout - what Sadik said.
 

rajesh srinivas

Active Member
Joined
May 30, 2015
Messages
377
Points
28
Location
hubli (karnataka)
1. What is the thickness of bracing? If it is 11 mm use 6 mm radius bit, adjust the depth to 4 mm and do the rounding. If your bracing is 18 mm think then use 8 mm radius bit adjust the depth to 7 to 7.5 mm and do the rounding. We don't have to worry much about the radius of bracing.

2. Is this radius related to edge diffraction? if so I don't have a knowledge about it so cant comment on that, But I have seen many Hi-End speakers which are rounded only on 2 sides. Rounding on all 4 sides will be equally good.

3. For your 3rd Point i have answered it in my 1st point.

4. For rear speaker cuts, 45 degree chamfer will be best for the speaker to breathe easily.

1. Its mdf 3/4IN X 2nos = 19mm, in some thread bijin has mentioned that A 13mm or 15mm radius router bit can bring that impression to the edges (bracing) as in pic, i want to do the same and even for baffle edges the same bit size can be used.
usually they say min 3/4in radius is required to tame the baffle edge defraction.

IMG_20150917_181023_Copy.jpg

2. It is for taming sound defraction from the baffle edges.

4. 45deg chamfer is excellent,i will go with that,in such a way that the place for mounting nuts at the rear are untouched as in pic.

Thanks for adivice.
 

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rajesh srinivas

Active Member
Joined
May 30, 2015
Messages
377
Points
28
Location
hubli (karnataka)
Hey guys...generally what size (thread size) of screws do you use for joining speaker boxes??

The reason for asking is.... the head of the screw should go into the mdf, and still there should be space for round edges.

(I mean, the screw head should not expose out after rounding the edges. )

A #8 wood screw at least 2 1/4" long (if single baffle) or 3in long (if double baffle), with the first 3/4" of the screw having no threads better do the roundover first then insert the screws and can fill up with woodfiller or best is use dowels to join woods.

Its mdf 3/4IN X 2nos = 19mm

Hi sadiq its 38mm ( i am using double baffle 19mm each)..wrogly typed.
 

Naveenbnc

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Oct 12, 2016
Messages
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Location
Hyderabad
Length is fine... I'm concerned about screw head size. As you said, doing the round first is better if it's possible !!! Good idea.
 

rajesh srinivas

Active Member
Joined
May 30, 2015
Messages
377
Points
28
Location
hubli (karnataka)
To what purpose are you rounding the bracing?

For the baffle, use the largest radius you can live with. The larger the better. Top and sides are effective, bottom is mainly cosmetic.

Rear of the cutout - what Sadik said.

You are right keith,the larger the better even 45deg chamfer will do ,but for both (looks and effectiveness) roundover 3/4in radius..
with top and sides only,bottom as you say is just for cosmetic..

Any idea how do you do the roundover on both sides of bracing,since when we do on one side we will be loosing the edge for the bearing to ride for doing the other side of braciing.??/

I am thinking of using router fence to guide against straight edge on the outer side of the bracing panel..
 
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