Design Study of 3D Printed Loudspeaker Port

[ssashton]

Hello Everyone!

I would like to share with you the conclusions of a study I have been working on over the past months to design an optimised 3D printed port for a desktop loudspeaker. I tested various methods to reduce unwanted resonances, while keeping an eye on port turbulence.

3D Printed Loudspeaker Port Design Study < Clicky Click

Here are a few snap-shots:

There is a whole lot of info in the paper beyond this including the effect of holes in ports, reduced wall thickness, constrained layer damping and what bending ports does to the response. I encourage you to check it out, since it took me a lot of work

While I unveil the fruits of the efforts, I must confess I have the intention of eventually offering a DIY kit and a finished product for sale based on the methods revealed in this study. I hope this doesn't detract from my wish as a fellow enthusiast to share what I discovered.

Simon

 

[jetlag72]

Hello Everyone!

I would like to share with you the conclusions of a study I have been working on over the past months to design an optimised 3D printed port for a desktop loudspeaker. I tested various methods to reduce unwanted resonances, while keeping an eye on port turbulence.

3D Printed Loudspeaker Port Design Study < Clicky Click

Here are a few snap-shots:
View attachment 346307
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View attachment 346303

There is a whole lot of info in the paper beyond this including the effect of holes in ports, reduced wall thickness, constrained layer damping and what bending ports does to the response. I encourage you to check it out, since it took me a lot of work

While I unveil the fruits of the efforts, I must confess I have the intention of eventually offering a DIY kit and a finished product for sale based on the methods revealed in this study. I hope this doesn't detract from my wish as a fellow enthusiast to share what I discovered.

Simon

Simon, if you are interested in comparing impacts of different materials, feel free to reach out!

I find myself with an 'abundance' of 1.75mm filament spools, all purchased within the last 12 months. I need to put them to some sort of use. The list below are unopened or highly sealed w/ desiccant after passing through heating and all are stored in a mild climate basement in a my family home at 65-72 deg F.

COLLECTION in order below are BASICS, NYLONS, ODDBALLS, THERMO$$$, METALS
==============================
(1) PLA/PETG/ABS/ASA...with and without CF; more than I can list + Lots of TPUs, but these are mostly generics without labeled Shore Hardness

(2) Lots of Name brand NYLONS in spools from 500g up to 3KG... PA-6s, PA11, PA12 many in multiple colors (including GF in different primary colors!) with and without varying levels of CF & GF (10-30%)

(3) PP, Ryno, Lexan, TPE (higher grade than the no-name TPUs in line (1)) and other oddball types

(4) Thermo and ECD rated from 3D-Xtech (PEI 1010, 9085), PPSU, PEKK, (all 3D-Xtech) and even a spool of PEEK

(5) Virtual Foundry and other metallics including copper, a couple of steels. bronze, iron; and COLORFABB metallic as well

All of my printers are consumer grade, heated bed, single extruders (.2 -.8) Prusa mk3is and 2xBBXCs but I do have a QIDI capable of mildly heated chamber and larger footprint commercial CreateBot F420 sitting unopened in a crate that is intended to process the $$$ filaments in line (4)

 

[ssashton]

Simon, if you are interested in comparing impacts of different materials, feel free to reach out!

I find myself with an 'abundance' of 1.75mm filament spools, all purchased within the last 12 months. I need to put them to some sort of use. The list below are unopened or highly sealed w/ desiccant after passing through heating and all are stored in a mild climate basement in a my family home at 65-72 deg F.

COLLECTION in order below are BASICS, NYLONS, ODDBALLS, THERMO$$$, METALS
==============================
(1) PLA/PETG/ABS/ASA...with and without CF; more than I can list + Lots of TPUs, but these are mostly generics without labeled Shore Hardness

(2) Lots of Name brand NYLONS in spools from 500g up to 3KG... PA-6s, PA11, PA12 many in multiple colors (including GF in different primary colors!) with and without varying levels of CF & GF (10-30%)

(3) PP, Ryno, Lexan, TPE (higher grade than the no-name TPUs in line (1)) and other oddball types

(4) Thermo and ECD rated from 3D-Xtech (PEI 1010, 9085), PPSU, PEKK, (all 3D-Xtech) and even a spool of PEEK

(5) Virtual Foundry and other metallics including copper, a couple of steels. bronze, iron; and COLORFABB metallic as well

All of my printers are consumer grade, heated bed, single extruders (.2 -.8) Prusa mk3is and 2xBBXCs but I do have a QIDI capable of mildly heated chamber and larger footprint commercial CreateBot F420 sitting unopened in a crate that is intended to process the $$$ filaments in line (4)

Thank you for your kind offer! I'm in the UK so that may present a difficulty. I do know some 3D printing enthusiasts in the US who might take the lot off your hands for a price (they are trustworthy guys).

I do plan to try some PETG and maybe ABS if I can stop it warping enough. I currently have only open printers, but have a stalled build of an enclosed printer that I'll finish one day.

I was going to have an Anker V6 multi-head printer but they cancelled it. I was hoping to try making a TPU damping layer integral as part of the print, like keyed in to the constraining layers.

It also crosses my mind that 'designing' the infill to absorb energy in flexing specifically may work as an alternative to a damping layer. There are so many possibilities.

 

[jetlag72]

You're welcome! Thank you for your offer as well, as I think my spool collection overran my output capacity on the second or third week of the hobby

Infill is key, and full of different possibilities in a single medium. Just with the flexible filaments-->Using and IDEX machine running 2 spools with differing Shore hardness ratings could produce some interesting internal geometries with consistent material asymmetries centric mode. 99% would probably sound like crap, but ya never know!

 

[ssashton]

Hello Everyone!

The design study has been significantly revised to include more information and correct some erroneous conclusions. I added a study of the effect of woofer position on the baffle.

3D Printed Loudspeaker Port Design Study V2

 

[GreenTea]

Interesting paper. I am wondering if it's really necessary to produce this complicated port shape rather applying some of these same methods to a more conventional round port tube. None of the effective port noise reduction methods seem to be dependent on this port shape.

 

[ssashton]

Interesting paper. I am wondering if it's really necessary to produce this complicated port shape rather applying some of these same methods to a more conventional round port tube. None of the effective port noise reduction methods seem to be dependent on this port shape.

I used this 'slot port' style because it was suitable for the small loudspeaker box. I do not know how it will work with a round port. I believe the port walls must move to absorb energy, so maybe a round port that has greater structural stiffness will not benefit as well from CLD. I also believe this slot port is helping absorb cabinet modes, so in a larger box where the port is a smaller percentage of the internal volume it may not show as dramatic effect.

One thing that really surprised me is how sensitive the woofer position is (page 31). I did not expect 10mm to make many dB difference at a frequency so low as 600Hz. The position of the port internal mouth inside the cabinet will also be sensitive in the same way.

P.S. Can a moderator DM me to update the first post in this thread with the new study?

 

[GreenTea]

Yea, I believe you are right about the rigidity of a tube port. I remember reading a white paper on the KEF LS50 on the flexible material they used in that speaker's port to tame its resonance. That would be an interesting read as well.

The modes inside a small speaker box is highly complex. While these reflections are easy to model in theory due to the simple shape of a rectangular box, minor variations in dimensions, reflectiveness, and absorption characteristics cause shifts in the position and magnitude of the peaks and nulls inside the cabinet. Since the slot port occupies such a large surface area inside the speaker box, it potentially "touches" more of these hot spots and is therefore very sensitive to woofer position as that has a direct effect on where these modes appear. Another possibility is that the woofer's vibration is exciting modes on the front panel depending on its position. This is why the front panel of a speaker is often thicker, and there are specific recommendations about placing braces around the woofer to control/damp its mechanical vibrations. Another interesting observation from the KEF white paper is their use of a floating faceplate with a CLD layer, which isolates/absorbs the vibration of the woofer from the rest of the box.

I know designers will often play with the port location and even use bent port tubes to locate the inside mouth of the port at a relative null inside the cabinet. But a lot of this comes down to trial and error - maybe a company like KEF is taking a more methodical modeled approach. Anyway, your paper's topic just reminds me so much of the KEF white paper.