DIY - Helmholtz Resonator

[EHT007]

Been having so much fun with Umik recently that i decided to make my own helmholtz resonator. 

I think im having issues with standing waves from the ceiling 2.94m high.  

Let me know what you guys think. 

 

While drawing up the box, i figured i might as well make something to complement my sonus faber stads. 

 

the hole opening of the resonator will have f-note from Stradivari Violin.  I managed to recrate in fusion and scale up to give me this 916cm2 opening. 

 

I don't understand the calculator what the  F1 Low and F2 High are so im slowing increasing box hole opening. haha  

 

Here is roughly target. 

 

 

 

Edited July 18, 2021 by Pasic007

[EHT007]

Progress so far. Slowing increase the opening and measuring it. Before I get F-hole cnc'd.

 

 

[EHT007]

Currently the opening is 686.26cm2 

 

The box is built so that corner foam bass traps can fit in

Edited July 18, 2021 by Pasic007

[EHT007]

WOW this thing works. Too well..

 

Ive dropped 10db at 52 hz ! When playing tone at 52hz it feels like sub is off lol.

 

White line is "Stradivari Resonator" tuned to 52hz (new name ive given it).  

 

You can see Blue line is no "Stradivari Resonator" and orange is when in place.

 

Time for me to go drill more holes !  

 

 

Edited July 18, 2021 by Pasic007

[EHT007]

More holes! 164 to be exact. At 20mm

[caminperth]

Wow - very interesting results!

 

I wonder if something like this would help my situation - lots of bass available everywhere in the room with the exception of the listening spot. Once the bass levels are increased to compensate, other areas of the room are not much fun to be in..

[EHT007]

2 minutes ago, caminperth said:

Wow - very interesting results!

 

I wonder if something like this would help my situation - lots of bass available everywhere in the room with the exception of the listening spot. Once the bass levels are increased to compensate, other areas of the room are not much fun to be in..

 

From what ive seen its very effective at single frequency that it's tuned for. ( big cabinet, fewer holes )

 

The addition of multiple 20mm holes was me trying to aim for higher frequencies, trial and error. It also has less impact as it targets more then one area i believe. 

 

My calculation the opening is 1216cm2 and HR web calculator suggest 1100cm2 based on my REW measurements.

 

my target now is to open it up to 1400cm2 this should get  Primary peak into 62.45hz and 117hz.    

 

This is what the the "SR" resonates like now.  This has foam inside otherwise the 200-400hz is a mess.  You can see Primary peak at 58.4hz and second 88.8hz

 

 

 

DrSK has given me more insight. Ive done more reading up on it. But if you want HR for higher frequencies you need smaller volume with 100s of small holes. 

 

 

 

[EHT007]

This sub is DIALED in ! 

Not too sure about waterfall, there is bit more sound treatment left on that front. 

But this is one flat frequency response line from nice little 12" Rythmik sub. 

 

 

 

[EHT007]

More pictures. 

 

Edit more pictures.

Cabinet sits 400mm of the back wall. And I found it if it lays on floor it just doesn't resonate as well. So I have it 110mm of the floor sitting on small mdf dolly. 

 

 

 

 

Edited July 19, 2021 by Pasic007

[EHT007]

This is poo. No sugar coating here. 

 

I think its back to the drawing boards, it fixes some issues but creates others. Plus other issues in midrange, it might be to do with lots little holes, or to maybe new reflections introduced by the big cabinet.  On weekend ill run a string based on some new ETC spikes.

 

Here is the sub with no EQ on minidsp. There is big peak at 46hz and i have PEQ on -12db on that set on back of the sub.  HR seems to suck life out still at 54hz even though the opening is now over 1200cm2. 

 

Got few different ideas going forwards. 

 

1) build enclosure within the box lid for the 110holes in the middle section and aim for high frequency resonator.  Down side the position of the cabinet where i get most SPL at low hertz and not 117hz that i would like to treat.

2) Create two smaller cabinets from single.  I've noticed the left and right speakers do respond well at different locations. So more of these is on cards for sure. 

3) 3d print ports to insert into slots and hopefully i can bring this down to 46hz and might allow me to turn off PEQ. 

 

Trial and error and best part. This is fun except for the part of cleaning all the mdf dust.

I want to get table saw and table router for some future works.  

 

 

 

 

 

 

 

[davewantsmoore]

On 7/19/2021 at 12:24 PM, caminperth said:

Wow - very interesting results!

 

I wonder if something like this would help my situation - lots of bass available everywhere in the room with the exception of the listening spot. Once the bass levels are increased to compensate, other areas of the room are not much fun to be in..

 

The best solution by far is to try to  move the listening position(s), move the bass source(s), and/or add more bass source(s).

[caminperth]

48 minutes ago, davewantsmoore said:

 

The best solution by far is to try to  move the listening position(s), move the bass source(s), and/or add more bass source(s).

 

Agreed Dave, though sometimes it ain't that easy! 

 

@Pasic007 - does it make a difference if the holes are facing either upwards or backwards?

[EHT007]

5 minutes ago, caminperth said:

 

Agreed Dave, though sometimes it ain't that easy! 

 

@Pasic007 - does it make a difference if the holes are facing either upwards or backwards?

 

Moving it around makes a lot of difference.  I havent tired upwards or backwards since i drilled more holes but ill give it crack this weekend and ill post the results. 

 

Do you run subs ? That was my issues Strads produce bit of bass, just 0 in listening position. Addition of a sub has fixed that completely.  All of my issues are main speakers related. 

i've got a few bits on order, over the weekend ill make a perforated helmholtz, and ill give a membrane a go as well. 

 

On positive note this project is keeping out of the classifieds page. 

 

[Misternavi]

On 7/18/2021 at 10:21 PM, Pasic007 said:

More holes! 164 to be exact. At 20mm

Stick that lamp in there. Makes for a really cool lampshade.

[EHT007]

1 hour ago, misternavi said:

Stick that lamp in there. Makes for a really cool lampshade.

I said that to my GF, I thus doesn't work out. It's not going to waste. 

I place RGB floodlight inside. 

 

 

https://youtu.be/sn6jNFzgAWY

Edited July 21, 2021 by Pasic007

[EHT007]

More toys to play with.

500$ spent of materials so far and 330$ on tools. 

 

[caminperth]

8 hours ago, Pasic007 said:

 

Moving it around makes a lot of difference.  I havent tired upwards or backwards since i drilled more holes but ill give it crack this weekend and ill post the results. 

 

Do you run subs ? That was my issues Strads produce bit of bass, just 0 in listening position. Addition of a sub has fixed that completely.  All of my issues are main speakers related. 

i've got a few bits on order, over the weekend ill make a perforated helmholtz, and ill give a membrane a go as well. 

 

On positive note this project is keeping out of the classifieds page. 

 

 

Sub - yea, using a Wilson Torus. Works well, but there is still a bit of a null in the listening position - hence the interest in your project.

 

Agree with your comment on the classifieds!!  

[EHT007]

59 minutes ago, caminperth said:

 

Sub - yea, using a Wilson Torus. Works well, but there is still a bit of a null in the listening position - hence the interest in your project.

 

Agree with your comment on the classifieds!!  

Yeah Dave is very right try different position. 

 

Last week I actually repositioned sub behind rack in the middle. I took a measurements, I'll try find tomorrow... You would not believe the difference. You just couldn't hear it. I tried adjusting phase. No go. Within an hour I had my gf giving me hand trying to place it back where it used to be. Lucky I had market it with tape.

 

Currently it's in a corner behind front right speaker firing at 45 degree towards  side wall.  I couldn't try any other positions as my rca is way too short. But I'm happy with results. 

Edited July 21, 2021 by Pasic007

[crtexcnndrm99]

25 minutes ago, Pasic007 said:

Yeah Dave is very right try different position. 

 

Last week I actually repositioned sub behind rack in the middle. I took a measurements, I'll try find tomorrow... You would not believe the difference. You just couldn't hear it. I tried adjusting phase. No go. Within an hour I had my gf giving me hand trying to place it back where it used to be. Lucky I had market it with tape.

 

Currently it's in a corner behind from right speaker firing at 45 degree towards  side wall.  I couldn't try any other positions as my rca is way too short. But I'm happy with results. 

Good fun this project by the look of it! I have been talking about giving some diffusers a go. I like the appearance of your strad front design but have also been keen on the lots of small holes appearance you see in the concert hall type rooms... 

 

Concerned about backfiring and having midrange suck out if I go in blind without a measuring set up like you’re using though.

 

Interestingly, I have a 12” REL and also found it worked best, in the limited positions I could test on my own, in front of the right speaker firing at an angle into the right wall! Odd.

 

 

[EHT007]

1 hour ago, crtexcnndrm99 said:

Good fun this project by the look of it! I have been talking about giving some diffusers a go. I like the appearance of your strad front design but have also been keen on the lots of small holes appearance you see in the concert hall type rooms... 

 

Concerned about backfiring and having midrange suck out if I go in blind without a measuring set up like you’re using though.

 

Interestingly, I have a 12” REL and also found it worked best, in the limited positions I could test on my own, in front of the right speaker firing at an angle into the right wall! Odd.

 

 

Great thing about measurements is it rules out the placebo effect especially when you spent half day marking up and drilling holes whilst selling a story to your self... this will be amazing.

 

80hz range was on my radar to fix. And you could clearly tell without measurements 8db improvement. However it would be very hard for me to pick up all the issues across other frequencies without measurements and you can't go back and test a/b. 

 

Strangely enough the other way I fix 80hz dip is by leaving front door of the house open! 

 

Haha that's funny about your rel, there must be some science behind our madness. 

[EHT007]

@crtexcnndrm99  as for diffusers this seems easy enough. 

http://arqen.com/sound-diffusers/

 

I'll probably just end up buying some. Unless I get a cnc router. I like consistency, and I can get by in Fusion 3d. Then something like this is easy to make. However, my design would have no r&d. Unless I buy one panel, laser scan, remodel and cnc. But that's naughty. 

 

 

[crtexcnndrm99]

6 hours ago, Pasic007 said:

@crtexcnndrm99  as for diffusers this seems easy enough. 

http://arqen.com/sound-diffusers/

 

I'll probably just end up buying some. Unless I get a cnc router. I like consistency, and I can get by in Fusion 3d. Then something like this is easy to make. However, my design would have no r&d. Unless I buy one panel, laser scan, remodel and cnc. But that's naughty. 

 

 

Oh if I had access to a cnc then the list of projects for it would be very long. Thanks, yeah it’s a bit more involved than absorption panels, although I reckon replicating the hybrid ones (foam with plywood face cut out with many holes) would be simple. A proper 20-30cm deep well diffuser of those arqen designs between the speakers would be nice.

[EHT007]

New design. 

this kicks ass. I've focused it on 42hz. I need to make it 44hz but wow. 

 

Trend is new resonator vs old design. 

 

Without the HR I get massive peaks and nulls. 

 

 

Still working on positioning. I really need 2nd box. As both speakers love it. But one positioning doesn't suit both speakers.

 

 

 

 

 

 

Edited July 26, 2021 by Pasic007

[EHT007]

Also made 2 new bass traps. 

 

3x 75mm polyester inside enclosure 19mm pine with 12mm plywood back.  I can place 4kg mass loaded vinyl on front to get better effect but will experiment at later time. I actually place one behind curtains and it made big difference.  This was going to be the lid but I just left it behind curtain.

 

 

[EHT007]

As I'm sitting here writing, I'm just listening bit of viking drum music, no subs. And  O  M F G.. my strads got bass now !!!