Helholtz Resonators DIY Input

Rather than go into details it is better to first understand what is going on and why these things work at all. Because once you do understand then you will be able to answer all your questions. It is for example that I do understand the principles that I am able to look at Mahgisters room and see what looks like a gas can with a straw in it and understand it is a tuned HR.

The general principle is a Helmholtz resonator is more like a shock absorber that we can tune to absorb certain frequencies. The way it works, a pressure wave comes along and pressure forces the air into the tube or passage and enters the body of the resonator. There it expands again and vibrates around inside the cavity. This creates a high pressure inside. When the pressure wave passes this pressure comes back out the opening.

But as it comes out notice it has been both delayed, and attenuated. Some energy was lost going through the opening. Some delay was achieved by the time it took to expand into the cavity.

These can all be modeled mathematically. The effect is to smooth out and make smaller what would otherwise be a big peak or mode. Just like the way a shock absorber on a car slows the wheel bouncing up, but then also slows it coming back down again, resulting in a smoother ride.

HR are by the way very similar to or closely related to the way a ported speaker cabinet works. With a speaker it is the volume of the enclosure, together with the diameter and length of the port, that tunes the cabinet to a certain frequency. Just the same, only different.

@millercarbon  Thanks for the explanation but I already understand those principles through my research.  I am looking for some hands on real advice that would be helpful in making the process go quicker and smoother.  Tinkering with all the variables seems almost endless.  Thus the questions….input was much appreciated.

I cannot help much here...

I use what was in my basement...

I only use one bottles or pipes at a times...Adjusting it mechanically for a better timbre instrument perception...

It takes me almost a year after the passive material treatment to increase the Helmholtz grid or the mechanical equalizer like i call it because it is a grid not a couple of bottles......

I did not count them but i have more than 40....Under 50....

I tune them almost one at a times and fine tune the lenght of each one neck with ears like someone fine tuning a piano...

Some are traditional Helmholtz resonators with a neck... Other are a tubes with no neck and work more like a diffuser than a damper...Anyway each resonator absorb and diffuse...The diffuser simply diffuse more...

Dont desesperate about the variables.... You must confide and trust in your ears perception of very well known instrument....( piano choral voices)

Any errors or imperfect tuning you will make will be corrected and fine tuned at the end by another one.... After more than 40 pipes i feel no distortion of the sound at all.... All improvement in a relatively large bandwith sample like a human voice, is a TRADE-OFF, corrected by another pipe...And the process go on...

This grid cannot be implemented in a living room....

And dont do it if you dont enjoy the experimenting process...There is no short cut way.... You cannot compute S.Q. with an A.I. for now...You must use your ears....

I did it because learning was fun.... And incredibly each addition was a relative improvement.... At the end i stop because any addition was a decrease in improvement... Simple...

I cannot help you for the material used or the proportion because i did compute nothing.... It was way more fun to listen and correct it... One at a time...with my basement junk...


Sometimes using an " approximation walk" experimental method tthrough all variables, of plus and minus guessing estimates, with multiple tubes tuning , is way more powerful than 9 identical tubes on the main reflective spot of the room... Like the ready made product "Argent room lenses" that inspire me one evening 2 years ago and which cost more than my audio system....My Helmholtz grid cost me nothing and is more powerful anyway....

A cue: locate them around the first reflective point on the wall beside each speakers, and dont use the same tubes nor the same proportion symmetrically...I place some behind my listening position between the speakers but on the opposite wall.... Anyway experimenting is key.... No room is similar...

And remember that the passive material treatment between diffusive surface, reflective one and absorbing one is complementary with the grid and cannot be spare... Active mechanical control by the grid and passive material treatment are complementary... One cannot replace the other ....


By the way the gas cans millercarbon has seen were there BEFORE i created my grid with plumber pipes and tubes... my virtual page has no image of this grid.... I even use paper toilet empty rolls then i dont want to attract the smile of " idiots" with photos of my " mad scientist" audio room....I am not crafty person at all.... But i can read psycho-acoustic articles or book.... This inspire me...

By the way they are cues about my journey in my thread : "miracles in audio.... "
And dont put any water in the tubes it is not necessary.... 😊



My best to you....

https://www.researchgate.net/publication/223804282_The_relation_between_spatial_impression_and_the_law_of_the_first_wavefront

By the way this article spark my journey....It is not about Helmholhz method but inspire me for undertanding
the general "imaging" process and how to improve it with the location of some Helmholtz tubes near my speaker...


Very illuminating for me....

More details in my thread personal journey : "miracles in audio.... "

Dont read the first pages begin with the end when i talk about Helmholtz method of mechanical equalization........

@mahgister  Thank you for you kind input and sharing your expertise.  You are an inspiration.  I will continue to do experiments with bottles for now to see if I achieve positive results the are worthwhile.
No,  i cannot and do not aspire to have a “mad scientist” room like your’s but do enjoy experimenting with sound enhancements within my constraints.  Your input is very much appreciated. Regards.

Some people have too much time on their hands!

Some people have too much time on their hands!

You are perfectly right!


Thanks for enlightening us about this fact and illustrating very clearly how some with too much time take experiments in acoustic and some other clueless dude hanter constructive audio thread with bullshit remark....

Mahgister got me started down this path & I'm very grateful for that. What a learning experience!

OP,
IMO as well, You really can't do this without a lot of experimentation. That alone will get you to know your equipment & room a lot better. It will also sharpen your listening skills. 

jasonbourne52,
Why
   

If you want absolute best result have wife make gallon of mushroom tea and have party. The acid work well too but the collective mushroom treatment get you smoother more organic sound with less potential for tweak and edginess over acid party.

Tin foil and LSD jokes dont reveal great creativity in humor or litterature...

The Trolls need to find a new playhouse to play in and have Barbe make them some shroom tea that just might inspire some creativity in how they use their time more productively!

@mahgister. Enlightened by reading about the Argent Roomlens resonators.  It gave me an understanding in the use of tubes as diffusers and why you moved into them. Not sure I want to go there.  I did have a good session with success moving a few bottle resonators which make a positive impact on SQ.  Some locations giveth while others take it away. Reflection points seem good while ones between the speakers and sitting position I did not like.  This is a journey of learning.  Thanks for sharing your experiences with the forum. 

Diffusers are only there to compensate for my resonators grid....It is not a road to  take but necessary compensation....Like reflecting materials and surface and absorbing and diffusive surfaces must be in the right balance... Also resonator bottles or tubes must be in a right balance with the more diffusive one...

Anyway any resonators diffuse also the frequencies which are not damp by it...

Thanks for your kindness to me....

My best to you....