What is this recessed hole referred as ?

[3rutu5]

hello first time on this forum for me, I'm about to embark on a journey by attempting to make a new tv/hifi cabinet and seriously looking at kerfing and yes a bit of a noob. Im looking into some options of having speakers in there and have no idea what this style of speaker hole is called nor what piece of machinery does it? I'm guessing a router as those larger hole saws seem to leave it quite rough around the edges.

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[AlexS]

I'd guess it's been cut using a holesaw, then cleaned up using a router with 45 deg cutter. A template with a hole to run the bearing guide on was probably temporarily fixed to the front.

[auscab]

Hi 3rutu5 , First post , Welcome .
Id be trimming up the hole with one of these . https://www.google.com.au/search?q=circle+cutting+jig+for+router&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj1yKr__8raAhVIT7wKHQvYCC0Q_AUIDCgD&biw=1120&bih=571

(https://www.google.com.au/search?q=circle+cutting+jig+for+router&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj1yKr__8raAhVIT7wKHQvYCC0Q_AUIDCgD&biw=1120&bih=571)There are plenty of ways to make them , it just depends on what you have to work with. I like to get the MIG welder out or the Oxy set and braze such things together.
The trick to good clean finishes with routers is taking most out with a saw or the router in steps and leaving a small amount for the final pass. By then if you have gone round a few times you will have figured out any hiccups that could effect a clean finish and a speed that doesn't leave burn marks. Stopping to change hand position can cause this as well.

Edit.
Its a bit more work making a jig to cut circles . Good if you intend on doing more than two maybe. This post has me searching because its an interest of mine since making one for cutting the hole in a guitar top and a few larger ones for round table tops. I just found this which is different and solves the smaller size circles in a nice way!
Router Circle Cutting Jig Plans • WoodArchivist (http://woodarchivist.com/2346-router-circle-cutting-jig-plans/)


Rob

[elanjacobs]

It's not really "called" anything, it's just a hole with a bevelled edge.

I'd guess they're punched out by the thousands on a CNC router. To DIY it's just a matter of making a round template to follow.

[3rutu5]

Thanks guys for the responses. I thought i was googling wrong as i wasnt getting much. I think i'll be getting a jig, not really that skilled to make most of my gear. I'm great at designing, just not so much with the follow through.

I was liking the idea of the taper on the hole and mounting the speakers from the rear to hide the screws and speakers.

[3rutu5]

i guess i had a crack, cut a hole with a holesaw and then got a 45deg fillet with bearing bit for a cheapo trimmer router. On a different project i did make a circle jig with the trimmer and some ply and the saw dust almost caught on fire due to not getting out of the way :) made for an interesting experience.


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[elanjacobs]

and the saw dust almost caught on fire due to not getting out of the way
What bit were you using?

[BobL]

What you should be using is known as a "Bellmouth port" profile and the edge should have radius of curvature of 1/2 of the radius of the opening.

There should also be a hole in the back or sides of the speaker with a similar shaped profile but it can be smaller in size than the speaker diameter.

The profile can be obtained with a suitably radiused router bit or placing a square shaped piece of timber onto a wood lathe and turning the shape.

These profiles are the least resistive in moving air in and out of an enclosure and so produce the most efficient speaker action.

For the hole in the backs of speakers the shape can be moulded from PVC pipe.
Here is an example of the Bellmouth port in the side of a Logitech speaker.

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For more details including how to make them from PVC look up "Bellmouth hoods" in tehtheDust extraction Forum