Official Luthiers Forum!

Thank you very much for all the input on my previous post regarding sound ports, all my questions got answered by all you veterans!

Now, does anyone know where I could find a good article on HOW TO MAKE A SOUND PORT?

How to bind it,cut it, re-enforce it,etc....?

Thanks again for all the help!

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

I'll be adding one to my current build and I'm planning to reinforce the inside, tape off the area and draw the design on the tape,then cut it with a dremel and router base.

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Tickle your guitar daily, and it'll tickle you back.

I made up a shaped set of blocks that are clamped on inside and outside, and drill the hole with a Forstner bit. I like to reinforce the inside with 1/32" poplar plywood from the model airplane shop, held on with epoxy.

On the 'corker', which has 20 holes in the side, I used wide cotton-poly bias tape , and it's holding up fine so far.Alan Carruth38751.6396180556

Here's a little mini course.
1) cut the side w/ taper.
2) glue on a patch to the INSIDE (don't ask me why I enphasize that word INSIDE). I make the patch the full height of the side and run it from the neckblock to the middle of the waist. Somewhere in the neighborhood of .070"
3) Cut the hole. If you plan to do this a lot, you might make a pattern in a piece of Lexan and use a pattern bit with your router.
4) bind the hole. Very important to do this before bending.(again, don't ask me how I know). Otherwise you'll be trying to bend in three dimensions and that SUCKS!
5) You might want to make a plug of wood to fit in the hole snuggly. This will help keep the binding from trying to pull away from the 'ends' of the curve during bending. Tape will probably work as well.
6) bend the sucker.
That's all there is to it. Any quesions, let me know. P

Paul, how do you bend the side with the patch glued onto the side?

It seems to me that the side wouldn't fit prperly in the mold!

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

Sorry to jump the topic off track somewhat, but it is related.

What ** I ** am interested in knowing is the procedure to adding one of those little baffels that open and close like Linda Manzer has used and John Monteleone has used.

I think those are very slick.

I understand about bending them to match the inside of the guitar, but if the upper bout is not perfectly circular I am not sure how they open and close.

Does anyone have any insight?

What do you do about finishing these things?

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Peter, I've just been throwing them in the bender and doing everything as normal. Has worked fine for me.

[QUOTE=Alan Carruth] On the 'corker', which has 20 holes in the side, I used wide cotton-poly bias tape , and it's holding up fine so far.[/QUOTE]

Going a bit OT here:
Al C., what are you using to glue the cotton/poly bias tape. I've been using the straight cotton for side reinforcements but can no longer find it, only the blend and it doesn't seem to glue well with Tightbond. Sticks OK but peels off easily.

Alan D.dunwell38751.7006365741

Brock, if you've got a good GAL library there is an article on Linda Manzer "Meet the Maker" where she shows pictures of how its done. Her set-up is essentially a pocket inside the upper bout that uses a leather gasket to hold the louvre snug against the side of the rib. Another builder is Harrison Guitars - his look even cooler (a google search will turn up his website).

The louvre (or sliding cover) is made out of Ebony or Ebonized veneer.Anthony Z38751.7598958333

[QUOTE=Anthony Z] Brock, if you've got a good GAL library there is an article on Linda Manzer "Meet the Maker" where she shows pictures of how its done. Her set-up is essentially a pocket inside the upper bout that uses a leather gasket to hold the louvre snug against the side of the rib. Another builder is Harrison Guitars - his look even cooler (a google search will turn up his website).

The louvre (or sliding cover) is made out of Ebony or Ebonized veneer.[/QUOTE]

Ok. Thanks for the tips. I have a full compliment of back Guitarmaker issues, but I will hunt that GAL one out.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Brock - the Manzer article is in GAL#56. If memory serves me right - she fits a leather gasket against the inside of the rib cut slightly larger than the port hole. The leather gasket snugs the louvre as well as stops it from rattling. The louvre (or sliding piece) is sandwiched in a pocket that is bent to the shape of the rib.

Sounds like a lot of work to me for little functionality.

Ok... I think I understand. So when the louvre is pushed all the way open, it just sort of hangs there inside the box "pinched" at the edge by the gasket and support.

That is different than what I was envisioning, but it would work.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

[QUOTE=Pwoolson] Here's a little mini course.
1) cut the side w/ taper.
2) glue on a patch to the INSIDE (don't ask me why I enphasize that word INSIDE). I make the patch the full height of the side and run it from the neckblock to the middle of the waist. Somewhere in the neighborhood of .070"
3) Cut the hole. If you plan to do this a lot, you might make a pattern in a piece of Lexan and use a pattern bit with your router.
4) bind the hole. Very important to do this before bending.(again, don't ask me how I know). Otherwise you'll be trying to bend in three dimensions and that SUCKS!
5) You might want to make a plug of wood to fit in the hole snuggly. This will help keep the binding from trying to pull away from the 'ends' of the curve during bending. Tape will probably work as well.
6) bend the sucker.
That's all there is to it. Any quesions, let me know. P[/QUOTE]

Hi Paul,

In the other thread regarding side ports recently, it was obvious that some are cutting (drilling etc.) the ports after bending. Wouldn't this solve some of the problems you referenced? I ask because my sides are already bent and I am considering ports. The pattern I have envisioned lends itself to doing AFTER bending. Is there a reason why you do it before or is it personal preference?

Thanks, Steve

I cut mine after the box is closed up but as you already know I am usually the odd man out

Sound port installation instructions:

List of materials:
Dremel with router base
1/8" Downcut spiral bit (StewMac)
1/2" dia Dremel sanding drum
180, 220, 320 sand papers
Brush on super glue (Stew Mac)
2" masking tape

Tape the area off with two layers of masking tape. Be generous so you don't risk scratching the surrounding finished area around the port.

Look inside your guitar and see if there are any internal side braces. If so, transfer the brace locations onto the outside on the masking tape. This is the area that your sound hole must be located as you don't want to sever a brace. Stay well below the top and back kerfed linings too.

Draw out the port shape on the masking tape. Smooth designs seem to produce a better tone. I use a port roughly the size of a Large Egg. Remember the larger the sound port is the higher pitch your guitar will be. Start out smaller and you can always make it larger.

Use the Dremmel , router base and down cut spiral cutting bit. Stay 1/16" inside of the line and cut the hole out.

Put the sanding drum in the Dremmel and now sand to the finished shape outline.

Use 180 sandpaper and round over the internal and external edges of the hole. Progress to 220 and finish with 320. Be very careful NOT to sand the finish on the exterior of the guitar.

Coat the edge of the hole with superglue. It will dry hard and shiny. Use the edge of the brush to apply the glue and make a circle around the freshly sanded edge.

Remove masking tape. If the glue is rough (usually it isn't) you can smooth with 600 wet or dry sandpaper and then buff.

Get a glass of iced tea, kick back on the couch and let me know how big your smile is when you first hear the port.

And no, I don't bind the port edges either.

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tim...
http://www.mcknightguitars.com

In a word: binding. If you bind the hole, it will be a bugger to do after it's bent.

Tim, do you not re-enforce the port with anything from the inside?

Paul, thanks for the mini course!

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Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

I always cut and bind after bending and cutting the contour of the sides, so
that the hole will be centered top to back, and located at the spot where i
want it along the side. Your binding doesn't come loose in the bender?

_________________
Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

Howard, how do you get the binding to bend in the 3rd dimension? Or do you find a flat spot along the side that doesn't require it?
I haven't had much of the binding coming loose in the bender. Only at the "ends" of my oval it would pull away slightly. That's what the plug is for. It holds everything together nicely.

[QUOTE=Tim McKnight]
I use a port roughly the size of a Large Egg. Remember the larger the sound port is the higher pitch your guitar will be. Start out smaller and you can always make it larger.
[/QUOTE]

Tim, I would say they are more like a small egg. Well, maybe the eggs down your way are just runts!

I'm confused by what you are saying. Are you saying that the larger the port, the higher the pitch that the PLAYER will hear or the higher the guitar's pitch?

Thanks, Steve

Al D:
I use hot hide glue. In the comparison test I did it worked measureably better than Titebond with either cotton-poly or nylon tape. Brush a stripe of glue onto the side, lay in the flattened out tape, brush on some more glue to saturate it, and wipe off the excess with a paper towel. I also shellac them afterward, when the liners are in, to protect the glue from air, and that also helps stick them down.

sfbrown:
The port raises the pitch of the 'main air' resonance. The farther the port is from the 'main' soundhole location the more it will change that pitch for a given sized hole. You can compensate by reducing the 'main' hole size a bit, but it's a little hard to tell by how much for a given port size and location.

The port will also 'vent' some high frequency interior air resonances that you probably would not normally hear. Often these are 'wasters' on standard guitars: things that suck up energy without producing sound, and they would be 'dips' in the output spectrum. The port can more than double the output at one of these frequencies; but remember, that's twice a small value, which is still a small value. However, by adding more power at mid- to high-range frequencies the port will tend to make the guitar sound 'brighter'.

The larger the port, the greater both of these effects, the rise in the 'main air' pitch and the output from high-end interior resonances, are. This can be percieved as more 'treble balance', or more 'brightness', and the guitar may or may not 'carry' better. Whatever gains there are, are not without costs. Generally speaking you lose bass tone, and the overall power of the guitar is not increased by much [1-2%], even though more of that power might be in frequency ranges where your hearing is more acute.

Paul, I run it through a Klein bottle to twist it through the 4th dimension.
Works like a champ.

When I don't have time for that, I take advantage of my holes being round
and either bore out the binding as a ring from a solid block, or turn it on
a lathe. Some of my fancier lathe-turned ones are done in two pieces--
one piece goes through the hole and the other fits around it and is
shaped to the curve of the sides on its underside. But lately I've just been
doing them flush on the outside like binding. You couldn't do this if you
bore the hole before bending; it would then no longer be round after
bending when looked at on axis. By using a deeper piece for the binding,
I can create a duct for the port, which lowers its resonant frequency and
creates the opportunity for some impressive sounding talk about
Helmholz resonators and ducted reflex ports.Howard Klepper38753.6202430556

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.