Could I use a triangular bass drum port?

AtomicFlapjack

Senior Member
Hi guys, I know there have been plenty of threads on ports, discussing how the size and placement of the port (and also number of ports) affects sound and feel. However, I'm wondering if anyone has ever used a port any shape other than circular? Does anyone know whether using a triangular port would affect sound and feel to using a normal circular port? The only reason I ask is that I just got a new head for my bass drum with my bands (The Aurora Skies) logo on it. You can see where the triangular port would go, inside the Penrose triangle. The triangle that would be cut out is isosceles, the base is 10cm and the two long sides are 13cm. The area is 60cm. Thanks.
 

Attachments

Netz Ausg

Silver Member
I imagine it'd be more likely to tear from the corners - circles work well as they don't have any. Saying that, though, you could reinforce the edges. Otherwise the shape might disturb the vibrations somewhat.

Try it, let us know!
 

Naigewron

Platinum Member
Yeah, I'd look out for those corners tearing once you start tensioning the head, but if you can reinforce those I don't see any problem with it. The port is there to let air escape, so the shape shouldn't matter much.
 

AndyMC

Senior Member
I can't imagine there being any major problems, just make sure to round off the corners enough to keep the tension spread out. They made triangular drums in France, and they looked dumb and didn't sound great, but they work. You'll probably want to take another drumhead and cut out a reinforcement triangle and glue that on the back.

On a separate note my band that just broke up was called Aurora Dreams, lol.
 

tard

Gold Member
I cant see a problem but I think I would take the head off and put it on a block of wood and use a forstner bit to cut clean circles in each corner before cutting the rest of the triangle.
 

GruntersDad

Administrator - Mayor
Staff member
Using the head in the photograph, use an Exacto knife and cut the center triangle out making sure that one straight line does not extend past the others and it should not rip beyond the cuts. As for using a forsner bit to cut a drum head, that is a recipe for disaster.
 

Dr_Watso

Platinum Member
I cant see a problem but I think I would take the head off and put it on a block of wood and use a forstner bit to cut clean circles in each corner before cutting the rest of the triangle.
Yea, either this or just round them slightly so there's no real sharp angles.
 

B-squared

Silver Member
Jet planes once had rectangular windows until a couple lethal jet crashes revealed that the corners on the windows were attracting fatigue stresses; which ultimately led to the fuselage tearing apart in midair.. Of course the windows are oval now, but the point is sharp corners attract stress. In your case, your head will tear.

I'm a structural engineer and I'm familiar with this kind of stuff. There are a lot of drum myths (people believe what they want to believe despite inconvenient things like physics) but in this case, the tearing and potential problems are all too real. If I were you, I would draw triangles on your head if you want them there. I wouldn't cut them.
 

evolving_machine

Silver Member
Since the drum head is pulling evenly in a radial pattern, the straight lines across the radial pattern will actually pull in such a way as to be a loose flap.

As others have suggested, the corners of the triangles would have to be rounded so they will not rip.

There will be less tension on the straight lines of the triangle and it would be very loose and of course the rounded corners of the intersections will have a concentration of stresses. At the concentration of stresses, there is a higher risk of ripping the head.
 

LukeSnyder

Gold Member
As others have said, you would have to round the corners. And I think the rounding should be fairly significant, as well. Additionally, you could reinforce the corners a number of different ways. The simplest method (and quite possible the most effective) would be to apply duct tape on the inside of the head at the corners. This should help prevent any tearing. However, I think no matter what you do, the chance of tearing would still be very high.

Perhaps another solution would be to create a circular hole with a diameter as large as could fit into the inner triangle of the logo, and then paint the remaining inside corners matte black to create the illusion of a triangular hole. It wouldn't be that the best, but it still might look cool.
 

evolving_machine

Silver Member
Go a-head try it.
What the heck is the cost of a new custom bass head?
About a hundred bucks with the art work?

You may glue pieces of head on the back of the intersection area to reinforce it instead of the duct tape.

Stress concentration is an area of mechanical engineering that deals with such things as irregular shapes that disrupt the stress in materials.

Many have attributed this stress concentration to the demise of the Titanic. But others felt it was the steel not having enough carbon to make it steel and not iron.

Guntersdad's web page does not apply to this situation because it is assuming a linear stress where in this situation you have a radial stress. The first cross product shows and X and Y variable in the rectangular coordinate system where in this situation you would have an R -theta varable in the polar coordinate system.
 

THC

Senior Member
Since the drum head is pulling evenly in a radial pattern, the straight lines across the radial pattern will actually pull in such a way as to be a loose flap.

As others have suggested, the corners of the triangles would have to be rounded so they will not rip.

There will be less tension on the straight lines of the triangle and it would be very loose and of course the rounded corners of the intersections will have a concentration of stresses. At the concentration of stresses, there is a higher risk of ripping the head.
This is what I was thinking when I first read it. The three corners will bear all the tension stress, and the straight edges will have no tension at all and will be loose no matter how tight you make the head.

I wouldn't do it.
 

Toolate

Platinum Member
Just make nice round corners and color them black to add the look of the points.

You could also cut a round inside a black triangle.. I would go for the ttriangle tho.
 

evolving_machine

Silver Member
This is what I was thinking when I first read it. The three corners will bear all the tension stress, and the straight edges will have no tension at all and will be loose no matter how tight you make the head.

I wouldn't do it.
You said it much better than I could, thanks.
 

tard

Gold Member
As for using a forsner bit to cut a drum head, that is a recipe for disaster.
Tried it on an old head last night. Worked perfect, nice clean holes. Thats the whole point of a forsner bit to cut a clean edge. A regular drill bit would chew it up bad but the bladed edge of the forsner bit will cut the circle out of the thin material before the bit goes down far enough for the teeth to touch the head. I have used forsner bits before to make nylon washers out of similar material like that before.

BTW If you didnt have forsner bit you could use a compass out of a protractor set and just put a hobby knife / exacto knife where the pencil would go to cut a perfect clean circle that way.
 

GruntersDad

Administrator - Mayor
Staff member
I have always used an Exacto knife or a disposable scalpel. Never needed a drill bit to cut thru a drum head.
 

Otto

Platinum Member
suggest heating the knife/razor before cutting....will keep the corners stronger and less likely to tear(the problem Ive seen with non circular ports)
 

tard

Gold Member
I have always used an Exacto knife or a disposable scalpel. Never needed a drill bit to cut thru a drum head.
Its just hard sometimes to get a perfectly smooth cut start to finish, especially on smaller circles and anywhere you stop and start again can be prone to tear at that point.


suggest heating the knife/razor before cutting....will keep the corners stronger and less likely to tear(the problem Ive seen with non circular ports)
Hey, thats a really good idea. Heating up a piece of 1/2" copper water pipe to make a circle in each corner then cut out the rest of the triangle would work quite slick I think..
 
Top