DIY Tube Bass Trap and frequency tuning

[abdo123]

You may not be sure but thankfully many people are. We have calculations and theories in place for a good few decades -- for some even more than a millennia! I was sure enough to design and built mine and it works as expected.

Standing waves are easy to measure. Helmholtz resonators are also easy to design and built. The secret of resonators had been out for a pretty long time

Pipe organs invented by the Greek in the 3rd century BC. They were called hydraulos and the air was piped in via water pressure. However, they had open pipes that work on the same physical principal as a Helmholtz resonator, which is what a closed pipe organ use. Since the 5th century AD organs are operated by bellows and their numbers increased. By the 9th century pipe organ was part of the music scene. Lots and lots of people learned how to design, build and repair them.

I wasn’t trying to argue i was actually asking.

I would like to build some and i want to be sure of how many i would need because these things can escalate in size very quickly.

 

[Razorhelm]

They are standard plastic pipes of 10" diameter. They are much, much bigger version of these.

Cool thank you , my plan is to buy the pipes and 3d print tops with different size openings until I get absorbtion at the frequency i need.

 

[sarumbear]

I wasn’t trying to argue i was actually asking.

I would like to build some and i want to be sure of how many i would need because these things can escalate in size very quickly.

Then, I apologise. I interpreted your phrase "I’m still not sure if it is possible to determine..." as disagreement to what is being said.

They are indeed large. Very large! I wouldn't use a bass trap inside a room as part of the furniture. There are some vibrating bass traps that are much smaller but they do not work much below 70Hz, if that. In order to tame a 30Hz or lower standing wave you need something the size of a dishwasher! That is why I chose a long tube. It was narrow enough to hide it inside the false ceiling and there is ample space for multiple traps, and tuning the trap is easy; you just alter the length by moving the stopper at one end in and out.

 

[sarumbear]

Cool thank you , my plan is to buy the pipes and 3d print tops with different size openings until I get absorbtion at the frequency i need.

There are quite a few calculators online that may help you to get going.

 

[Frgirard]

Whoever knows how to make an HR with the right tune the first time can aim for the Nobel Prize.

 

[sarumbear]

Whoever knows how to make an HR with the right tune the first time can aim for the Nobel Prize.

HR?

 

[abdo123]

HR?

Helmholz Resonator.

 

[sarumbear]

Whoever knows how to make an HR with the right tune the first time can aim for the Nobel Prize.

It is not difficult if you measure the unit correctly. I build one of my resonators for 43Hz, it resonated 41Hz, I had to move the tuner piston ever so slightly. I agree though, it is trial and error if you are dealing with holes only and with multiples of them. Mine are tuneable by adjusting the length of the tubes.

 

[Razorhelm]

There are quite a few calculators online that may help you to get going.

That calculator is great! first top designed and printing!

 

[sarumbear]

That calculator is great! first top designed and printing!

Good luck with your journey.

 

[Frgirard]

It is not difficult if you measure the unit correctly. I build one of my resonators for 43Hz, it resonated 41Hz, I had to move the tuner piston ever so slightly. I agree though, it is trial and error if you are dealing with holes only and with multiples of them. Mine are tuneable by adjusting the length of the tubes.

it's not a question of measure but be lucky with the simulation, the materials and be careful in the assembly.
Bravo.

 

[Razorhelm]

If anyone ends up down the same path this article is very useful

Helmholtz Resonant Absorber

A listening room, defined by its dimensions, can be mapped in terms of a series of pressure peaks and nulls, in all three dimensions. This refers to the creation of standing waves (modes), and the

www.audioholics.com

 

[sarumbear]

it's not a question of measure but be lucky with the simulation, the materials and be careful in the assembly.
Bravo.

Thank you.

Just to clarify when I said "measure the unit", I meant the physical dimensions not the acoustic response. I'm an engineer and I don't believe in luck in design. I expect what I calculated and then designed to work within tolerances that I'm working with. A Helmholtz Resonator is such a simple device that there is no point to simulate it. A port attached to a volume of air, that will resonate at a single frequency. That is all to it.

 

[Worker]

Thank you.

Just to clarify when I said "measure the unit", I meant the physical dimensions not the acoustic response. I'm an engineer and I don't believe in luck in design. I expect what I calculated and then designed to work within tolerances that I'm working with. A Helmholtz Resonator is such a simple device that there is no point to simulate it. A port attached to a volume of air, that will resonate at a single frequency. That is all to it.

Hi, #sarumbear

Would you mind sharing the practical details of the Helmholtz Resonators you have designed and built?

In particular the theoretical basis you used for your design, the physical construction details, materials used and deployment/positioning within your room would be very helpful.

Some photos and/or sketches would be perfect.

The results of your before and after measurements in the relevant low frequencies would of course be of interest to many members and might inspire others to follow.

Thank you.

 

[sarumbear]

Hi, #sarumbear

Would you mind sharing the practical details of the Helmholtz Resonators you have designed and built?

In particular the theoretical basis you used for your design, the physical construction details, materials used and deployment/positioning within your room would be very helpful.

Some photos and/or sketches would be perfect.

The results of your before and after measurements in the relevant low frequencies would of course be of interest to many members and might inspire others to follow.

Thank you.

I used a 10” (25cm) plastic water pipe. I blocked one end and placed a moveable block on the other end, like a medical injector. That allows the volume to be adjusted. The resonator is placed at approximately middle of that main pipe. It is made of a short 5” (12.5cm) pipe glued to the main pipe.

I do not have any images to share I’m afraid. The system had been in place for a long time. However, each pipe had been sufficient to cancel the three main standing waves of the room. I needed three pipes but as many can fit inside the ceiling, out of site, I could use as many as I needed.

I used my trusty HP calculator but these days you can find many online calculators. I posted a link earlier.

 

[Andysu]

I used a 10” (25cm) plastic water pipe. I blocked one end and placed a moveable block on the other end, like a medical injector. That allows the volume to be adjusted. The resonator is placed at approximately middle of that main pipe. It is made of a short 5” (12.5cm) pipe glued to the main pipe.

I do not have any images to share I’m afraid. The system had been in place for a long time. However, each pipe had been sufficient to cancel the three main standing waves of the room. I needed three pipes but as many can fit inside the ceiling, out of site, I could use as many as I needed.

I used my trusty HP calculator but these days you can find many online calculators. I posted a link earlier.

no pictures and where is the video? the video? they land on the moon take pictures and had video and audio and you have no video.

 

[sarumbear]

no pictures and where is the video? the video? they land on the moon take pictures and had video and audio and you have no video.

Sorry. Those were done before smartphones...

 

[Andysu]

as for the tube thing i tried that some years ago and increased the SPL dB and lowered noise artifacts it was almost close to +10dB increase and the tube was 6" wide i think '8 long

 

[MRC01]

... I am having trouble with long decay times for bass in my listening room, an open plan living room and kitchen. I would like to build some bass traps and tune them to the frequencies where I have the most trouble. I think tube traps would be a good fit but I have struggled to find out what dimensions I need to deal with the frequencies which are causing my problem. the worst frequencies are 75hz and 55hz but a broadband absorption below 100hz would be great.

I feel like length, diameter, filling material and thickness of filling must matter but I can't seem to find how to work out what you need.

Does anyone know of a good guide to follow? or a calculator to work this out?
...

Do you want to affect a broad or narrow frequency range? That will determine what kind of treatment to build.
Porous absorbers are the broadest, tube traps narrower but still broad, resonators narrower than tube traps.
The tube traps I built are about 2' diameter and 7' tall. They made a noticeable difference, lifted 40-80 Hz trough by +6 dB, lowered some peaks by -2 dB with corresponding improvements to spectral decay. Details in the link. The steady state FR measurements don't do the difference justice. It really made a difference!
PS: unlike a resonator, with a tube trap the diameter tunes the frequency and the length determines how much impact it has. But with a tube trap it's not as important to nail an exact frequency because they affect a broader spectrum. Just make sure they're big enough to affect the bass, say at least 16" diameter.
PPS: you may enjoy this old Stereophile article.

 

[bo_knows]

Thanks for all this, is there any information about tube traps? I am starting to think they are just normal absorbers in a tube shape!

No tube trap will provide sufficient absorption in the 75hz and 55hz range. They will work OK above 100Hz.

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