Round Over on Titan Horn Opening

[Ollie]

Hi folks.
I am getting close to finishing my two T39 x 20" project. Thay have been a while in the making, but thats another story.
Anyway, regarding routing the round over on the cabinet edges, specifically the horn opening.
I read on the forums most use 3/8th inch or 1/4 inch radius which translates to 8 mm & 6 mm in the metric world.
This seems fine to me but I got wondering about the mouth opening, where a round over of 3/8 will leave approx. 1/8 width on the single width of ply.
Any suggestions? Any close up images of the finished edge?
Ollie

[djohnson573]

Hi folks.
I am getting close to finishing my two T39 x 20" project. Thay have been a while in the making, but thats another story.
Anyway, regarding routing the round over on the cabinet edges, specifically the horn opening.
I read on the forums most use 3/8th inch or 1/4 inch radius which translates to 8 mm & 6 mm in the metric world.
This seems fine to me but I got wondering about the mouth opening, where a round over of 3/8 will leave approx. 1/8 width on the single width of ply.
Any suggestions? Any close up images of the finished edge?
Ollie

Ollie, I was a little skeptical at first about using a 3/8 roundover on 1/2 ply, but it turns out fine and matches the penn corners perfectly. I don't understand the 1/8 width as you will still have 1/2, it will just be rounded on the outside. Just be extra careful around the horn openings as the guide bearing on the roundover bit is hanging on by a millimeter. Alternatively, you can clamp on a guide bar for the router, but if you are just careful and don't apply a lot of force you should be fine.

[David Carter]

Alternatively, you can clamp on a guide bar for the router...

That's what I did. Easy to do and makes it a lot easier to run the router across without having to worry about it.

[LelandCrooks]

5/8 brad nails. Just long enough to hold it in place, easy to pop out. You really want to do this for those edges. Way too easy for the router to tip just a teeny, then you have a divot to fix.

[SoundInMotionDJ]

I assemble the horn assembly before mating to either side.



That allows me to mark the sides and use a 1/4" round over bit in the router table to round over both the inside & outside edge of the horn mouth. I do the same for the bottom panel that is also in the horn mouth. And I round over both edges of all the horn mouth bracing at the same time. After the cabinet is fully assembled, I use a 1/2" radius to round over all the other edges.

Even using traditional techniques, it would be easy to mark the location of the horn mouth and round over the sides before beginning assembly.

I don't have any good closeups of the horn mouth that show this detail.

--Stan Graves

[Harley]

I assemble the horn assembly before mating to either side.

Do you use dados to do this and make your braces in one ( joined ) piece?

[SoundInMotionDJ]

I assemble the horn assembly before mating to either side.

Do you use dados to do this and make your braces in one ( joined ) piece?

Yes. The brace is a single piece of 1/4" ply. I use 1/4" dados to get everything to line up. I use the router table & fence to make the dados.

--Stan Graves

[novasak]

I did mine with a 3/8 bit. They turned out a little pointy in the middle, but nothing some sanding can't round out. I used 1/2 ply for the mouth braces, and routed them before installation.

[Larry Acklin]

I add a 1x2 of clear pine on the flat to the inside of the mouth opening, not including the sloped panel. I glue/brad this into place, it beefs up the most fragile part of the cabinet, not much extra weight, and makes a good hand grip when moosing them over thresholds and onto stages.

I've been doing this to all the subs I have built and it really helps.

Larry

[AntonZ]

It may be a language issue (not a native english reader), but I have trouble visualizing that. Can you draw a sketch, or post a pic please Larry?

[Larry Acklin]

here you go...

[bgavin]

This also provides a handy way to mount a recessed grille, should you want one.

[AntonZ]

Thanks Larry. Looking back I don't understand why I didn't understand