Layperson Needs Help With Woodworking Term!

[Baz]

Hi All,

I joined this forum as I really need some help! I know nothing about woodworking or carpentry so I will need to get someone to do the work for me. I need to have some very basic rings cut from 12.5mm MDF (or other material that can be painted). These rings will act as supports/mounts that will hold spherical speakers that are about 106mm wide. Due to the spherical shape, the hole of the ring needs to have a "curved" cut so that it matches & aligns the curvature of the spherical speaker at point of contact. As a layperson, I do not know what this type of cut/profile is called & hours of googling has not been fruitful so I need someone to help me! I have attached an image of what I mean so I can be accurate when I try to describe things to the woodworker/carpenter - the curved curt is the one in green. If anyone can help me out or even do this for me at reasonable cost, please let me know! I need six rings made!

Many Thanks,

Baz!

 

[miles_hot]

How accurate does the curve need to be? I ask as if there is a sonic reason why you want to have a 100% fit then we need to be sure it is 100%. If not we have more latitude on that curvature so it can be arranged so that the top and bottom of the plate is in contact with the speaker... Forgive the probably stupid question but if these are spherical and this ring is sitting on a flat surface the bottom of the ring isn't going to be in contact with the speaker (is it? :? )

If you move this post the the turning section will will undoubtably find someone who can run up 6 of these - I'd offer but I'm having enough trouble getting out into the garage to turn one thing a month!

Miles

 

[Sgian Dubh]

... the hole of the ring needs to have a "curved" cut so that it matches & aligns the curvature of the spherical speaker at point of contact.

The curved element in your drawing, in profile, is an arc of a circle, ie, part of a circle's circumference. If a router cutter was used to form this arc you would use a cove cutter because this is what most woodworkers (and possibly other professions) call that profile. You may also hear the description 'cavetto' to describe the profile, although a cavetto is really an arc that is approximately one quarter of a circle's circumference. Slainte.

 

[bugbear]

How accurate does the curve need to be? I ask as if there is a sonic reason why you want to have a 100% fit then we need to be sure it is 100%. If not we have more latitude on that curvature so it can be arranged so that the top and bottom of the plate is in contact with the speaker...

Yes - as long as the radius of the profile is smaller than the speaker (likely) the speaker will fit.

Perhaps filler/mastic - the joiner's friend - could do the rest?

BugBear

 

[jumps]

How accurate does the curve need to be? I ask as if there is a sonic reason why you want to have a 100% fit then we need to be sure it is 100%. If not we have more latitude on that curvature so it can be arranged so that the top and bottom of the plate is in contact with the speaker...

Yes - as long as the radius of the profile is smaller than the speaker (likely) the speaker will fit.

Perhaps filler/mastic - the joiner's friend - could do the rest?

BugBear

Indeed - it would look like a perfect fit, and feel like one!

I am still intrigued as to how the rings, speakers and other elements interact - as has been pointed out the speaker sphere will be proud of the 'bottom' of the rings.

Finally, am I the only one who cringes at 12.5mm mdf - would you be cutting back from 16mm to get this?

 

[Eric The Viking]

If I may be so bold, I wouldn't approach it that way at all.

At a guess, these are tweeter housings (the spherical part). Whatever anyone thinks about separate tweeters (not for this forum, really), any planar surface intersecting with your sphere at right-angles to the tweeter's mounting plate will cause nasty and undesirable comb filtering effects for the listener (phasing and cancellations). The wider the plate, the more pronounced this will be. Assuming your sphere is 10cm diameter, the effects will be noticeable from around 2.8kHz upwards (at HF, say 6kHz upwards, it won't matter quite as much, and you can reduce/eliminate the effect with something like felt on the flat surface).

My personal preference is the Irish solution*, but if you are going down the spherical enclosure route, I'd instead stand the sphere up on three points, keeping it further away from the top of the other cabinets (or whatever surface it is sitting on), and leaving a reasonable gap underneath the bottom of it.

Despite the comments about MDF (this is a 'woody' forum, after all!), it's not a bad choice for acoustic applications, as it's fairly dense and doesn't resonate as much as natural timber, but is is very hard to finish it nicely wherever it's 'on show'. You could instead build up some quite interesting looking cones by glueing blocks of good quality plywood together.

So, for acoustic reasons, I'd support the sphere on three narrow cones instead of a flat ring. With a bit of careful drilling, you might even conceal the wiring in them (would look neat).

That's probably not the answer you were looking for but hey.

Regards,

E.

* "To Dublin, eh? Well I wouldn't be startin' from here..." It's very hard/impossible to achieve an omnidirectional radiator at high frequencies, and there are other ways of stabilising the stereo image. As I said, not for here really.

 

[jumps]

Despite the comments about MDF (this is a 'woody' forum, after all!), it's not a bad choice for acoustic applications, as it's fairly dense and doesn't resonate as much as natural timber, but is is very hard to finish it nicely wherever it's 'on show'. You could instead build up some quite interesting looking cones by glueing blocks of good quality plywood together.

Eric - for clarity, my observation re MDF was the specification of 12.5mm (rather than 12) - not a comment on MDF itself.

 

[Eric The Viking]

Despite the comments about MDF (this is a 'woody' forum, after all!), it's not a bad choice for acoustic applications, as it's fairly dense and doesn't resonate as much as natural timber, but is is very hard to finish it nicely wherever it's 'on show'. You could instead build up some quite interesting looking cones by glueing blocks of good quality plywood together.

Eric - for clarity, my observation re MDF was the specification of 12.5mm (rather than 12) - not a comment on MDF itself.

I see what you mean

Cheers, E.

 

[Baz]

Hi All,

Thanks for getting back to me - sorry I took some time to reply - I have not been well. To answer some of your questions:

Q: 'How accurate does the curve need to be?"
A: As long as thee is enough contact with the speaker to hold it flush from one side, so it might not matter if it is not a super accurate curve. the speaker is painted so I do not want to ruin the finish - I planned some kind of double sided sticker tape to fix onto the cut curve to aid it holding flush. The speakers will also be securing by strong wire on the non visible side which will be screwed into a joist in the loft.

Q: "If these are spherical and this ring is sitting on a flat surface the bottom of the ring isn't going to be in contact with the speaker (is it?)"
A: Well sort of yes, if you have a look at the new images I have posted, you might get a better idea?

Q: "I am still intrigued as to how the rings, speakers and other elements interact - as has been pointed out the speaker sphere will be proud of the 'bottom' of the rings."
A" I have posted new images which I hope will give a explanation as to what I mean?

Q: Finally, am I the only one who cringes at 12.5mm mdf - would you be cutting back from 16mm to get this?
A: I have two sheets of plasterboard in my ceiling & I would really prefer to have the rings fit flush With & into the plasterboard once I have cut out the holes in them. My thoughts were to cut the first hole in the lower plasterboard (visible in my room) at the diameter of the rings so it fits flush & another smaller hole in the upper plasterboard (visible in the loft) so that the rest of the speaker can protrude through into the loft. This way, a large part of the upper flat surface of the ring can be bonded on to the upper plasterboard for stable placement. This is why I assumed 12.5mm thickness as I thought that was standard plasterboard thickness? I will find out but if the is a way to use 16mm instead, I have no objections! If the sheets of plasterboard are only 9.5mm thick, then I guess I will have to use that?

Q: "At a guess, these are tweeter housings (the spherical part)" etc, etc...
A: These are small spherical satellite speakers from a company called Orb - nothing as bespoke or high end as you had imagined (I am just a working class lad!). They are very much like the Anthony Gallo Nucleus/Micro Speakers if you are familiar with them? I have also posted an image of the Orb's for you so you know as well as the Anthony Gallo speaker into its ceiling mount to give a near exact idea if what I am trying to achieve - the Gallo ceiling mounts do not work on the Orbs sadly!

I am sorry if I have been verbose & unclear but like I said, I know nothing about woodwork. The rings do not have to be MDF - they can be any wood/material as long as they can be painted in Matt White in a fairly smooth finish - I also need some other stuff made from MDF & everyone seems to use MDF so I assumed that it was the best material! I hope the images provide a better idea of things than I am able to explain!

Many Thanks All!

Bazzy!

 

[miles_hot]

Thanks for the additional explanation and pics - much clearer now. My thoughts:
1) the thickness doesn't need to be 12.5 mm - it just has to be thick enough to take the weight and fixing means; you can get the flush bit with shims behind the board. This will allow you to use 12mm board which is going to be a lot easier than cutting a 16 mm board down to 12.5.
2) A turner will be able to knock these out fairly easily (sadly I just don't have time unless you mind waiting for a few months) however it would be useful if they had a speaker to check curves etc with
3) Are you planning to leave some fixings visible so that you can get at the speakers if you need to? There are some pretty good looking hex hole bolts around
4) How confident are you of the hole that will be cut to hold the wood ring? Will this be very neat or will you need to fill it? This could influence the design in some way...
5) something that is nagging at the back of my mind that others far more experiences than me might be able to answer: how strong will the fine edge which provides the visual intersection with the sphere from below be? By the I mean will it a) be susceptible to damage b) provide enough strength and c) be robust enough during the production? If not I would consider either creating a slight step (thicker edge) or finding some way to take the weight of the speaker and then mask this with a plate or maybe just plastering in the speaker if you don't ever expect to extract it.

Hope this helps

Miles

 

[Oryxdesign]

This could be done easily with a router and a jig, where are you Bazzy so that we can help find you someone local.

 

[jumps]

Baz

1. As Miles has pointed out you can use 12mm mdf and, in 12.5mm plasterboard, you will simply have 0.5mm for your adhesive - sounds about right. The problem with 'flush' in this context is that you will have an unfinished plasterboard edge next to your neat painted ring - if you plan to fill and paint so that the ring disappears then I guess that's OK, but then I have to wonder why you are bothering with a ring at all (rather than setting them straight in the plasterboard for example). I think I would have a small rounded over lip on the outside of the rings to hide the plasterboard cut and provide a clean transition.
2. You show the sphere with the ring around the middle (which will of course be impossible if it's a one piece ring) but whether you have the bulk of the sphere above or bellow the ring you don't need to cut a curved side to the ring - simply cut on an appropriate angle to give a single line of contact at the lower face. The angle and size will depend on the position you wish the rings to be. The critical thing will be a nice clean lip at an aperture the correct size. If you want the ring just bellow the middle, with the speaker sitting in it, you will probably find a simple 45% angle will work - and a router will cut this easily.

 

[Baz]

Hi All,

Very sorry I have not been able to respond sooner - I have been in sheer agony & in tears from unceasing back pain! I will post again soon with some further pics once the system allows me to do so & will answer questions then!

Baz!

 

[Baz]

Hi All,

Sorry, I forgot to mention, but I am based in Harrow, NW London in case anyone is close by & can help!

Baz!

 

[TEO]

Hey Baz,

I'm with Oryx, Router and jig's the way to go.

I think the shape you're looking for is toroidal,

pm me and I'll do what I can to help out.

T

 

[Baz]

Hi All,

Very sorry I have not been able to respond sooner - I have been in sheer agony & in tears from unceasing back pain! In order to help convey things better, I have attacged a photobucket album of some pics of the actual speaker in a pre-cut 6mm ring (which is laminated so cannot be painted). Hopefully this will give a much better idea of things? Originally, I was going to just surface mount the rings so wanted a thin thickness but as I would now prefer for the rings to be inset into the thickness of the ceiling plasterboard, I think I can use a thicker (>6mm) ring thickness? The back of the speaker has a screw post which I can affix some strong cables & in turn secure those cables to joists so as to maintain tension & ensure the speaker is kept firmly in place (that is the idea unless there is a better way?)!. I have tried to answer your questions s best as I can below:

http://s296.photobucket.com/albums/mm17 ... %20Angles/

@Miles:

Q1) the thickness doesn't need to be 12.5 mm - it just has to be thick enough to take the weight and fixing means; you can get the flush bit with shims behind the board. This will allow you to use 12mm board which is going to be a lot easier than cutting a 16 mm board down to 12.5.

A1) I am open to any changes needed - I will need to go up into the loft to check whether the ceiling plasterboard is 9.5mm or 12.5mm thick - I have two sheets one on top of the other.

Q2) A turner will be able to knock these out fairly easily (sadly I just don't have time unless you mind waiting for a few months) however it would be useful if they had a speaker to check curves etc with

A2) I can supply a speaker if need be?

Q3) Are you planning to leave some fixings visible so that you can get at the speakers if you need to? There are some pretty good looking hex hole bolts around

A3) I was planning on it being a flush finish but have to admit, I really do not understand what you mean - but I can always get to the speakers in the loft above was my thinking

Q4) How confident are you of the hole that will be cut to hold the wood ring? Will this be very neat or will you need to fill it? This could influence the design in some way...

A5) I was of the thought that as I have two sheets of plasterboard in my ceiling, the hole does not have to be perfect as any rough edges will be covered by the flat surface of the speaker ring width which will be stuck to the upper sheet of plasterboard?

Q5) something that is nagging at the back of my mind that others far more experiences than me might be able to answer: how strong will the fine edge which provides the visual intersection with the sphere from below be? By the I mean will it a) be susceptible to damage b) provide enough strength and c) be robust enough during the production? If not I would consider either creating a slight step (thicker edge) or finding some way to take the weight of the speaker and then mask this with a plate or maybe just plastering in the speaker if you don't ever expect to extract it.

A5) I was hoping that as I would be using a rubbery type of glue with the fine edge & speaker body as well as strong wires connected at at screw post on the back of the speaker to ceiling joists, this would be strong enough? I am open to creating a thicker edge if need be?

@Simon:

Q) This could be done easily with a router and a jig, where are you Bazzy so that we can help find you someone local.

A) I am based in Harrow, NW London - hopefully someone will be close!

@Jumps:

Q1. As Miles has pointed out you can use 12mm mdf and, in 12.5mm plasterboard, you will simply have 0.5mm for your adhesive - sounds about right. The problem with 'flush' in this context is that you will have an unfinished plasterboard edge next to your neat painted ring - if you plan to fill and paint so that the ring disappears then I guess that's OK, but then I have to wonder why you are bothering with a ring at all (rather than setting them straight in the plasterboard for example). I think I would have a small rounded over lip on the outside of the rings to hide the plasterboard cut and provide a clean transition.

A1) I was planning to paint & getting someone to cut the oles so the ring edges should fit almost perfectly within the hole & rest against the upper sheet of plasterboard? I wanted the support rings for extra support, aesthetics & I fear that as I have two sheets of plasterboard in the ceiling & the speaker being a sphere, there will still only be a very small contact area & a straight cut hole will need lots of filling in which I do not want to do as it will mean securing the speaker in without ever being able to change it (in case it blows & needs replacing)

Q2). You show the sphere with the ring around the middle (which will of course be impossible if it's a one piece ring) but whether you have the bulk of the sphere above or bellow the ring you don't need to cut a curved side to the ring - simply cut on an appropriate angle to give a single line of contact at the lower face. The angle and size will depend on the position you wish the rings to be. The critical thing will be a nice clean lip at an aperture the correct size. If you want the ring just bellow the middle, with the speaker sitting in it, you will probably find a simple 45% angle will work - and a router will cut this easily.

A2) Thanks for the help - please have a look at the pics attached & advise if that will still work?

Many Thanks All,
Baz!

 

[Baz]

Hi All,

Teo,

I have sent you a pm as requested - please kindly check!

Many Thanks,
Baz!

 

[Oryxdesign]

Baz, did you get this sorted?

If you just want the rings cut from 6mm mdf and can give me the size of the hole and the outside diameter I could probably knock them out and post them.

Simon

 

[Baz]

Baz, did you get this sorted?

If you just want the rings cut from 6mm mdf and can give me the size of the hole and the outside diameter I could probably knock them out and post them.

Simon

Hi Simon,

Not sorted yet! That would be great if you can help out - if need be, I will gladly send you one of the speakers so you do not have to guess at things - would that be helpful?

Very Many Thanks!

Baz!