Pipe Dreams.....50hz Helmholtz resonator out of PVC pipe. Bass trap or money trap?

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nwickliff

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Joined 2020
geoffkait said:
Re article on Plane Absorber Resonance posted earlier today: in the last paragraph it is mentioned that putting some damping material (fiberglass in this case) inside the device increases the device bandwidth. Hey, whaddya know, just like for Helmholtz resonators! 🤗
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It’s like saying hitting the point of a thumbtack with a hammer will make it a broad point instead of a sharp point. Technically true but in the grand scheme of things, you wouldn’t want to stand on the Thumbtack because it will still pierce your foot. The resonator will still be very high q, and will be less efficient as well.
 
tubelectron

tubelectron

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Joined 2008
nwickliff said:
Love it man! You've been at this a while! Some nice Cornwalls there. Always wanted to try some. Closest I got was Chorus Speakers. You'd pic REW up in a flash! Very intuitive.
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Thanks @nwickliff ! First will be to add/rebuilt a suitable/practical hardware to make measurements and calibrations instant-easy, even automatic like it was with my obsolete LspLAB and SpectraLAB softwares...

For the curiosity : what hardware do you use with REW ? Do you have an audio interface box like I have ?

Yes, those Cornwall clones were a good project - I ended with a CW+ project, that I finally sold because I never had the room to build and install it in finished version... :confused:. Tweeter was KP-250, Squawker K-57-K, Woofer was Crites CW1526C, crossover was custom-made, base on Crites T2A transformer. I used two cab prototypes : a 160L (CW original volume) and a low-tuning 232L SBB4 (that I called CW+, a neat improvement).

aJHYJb-CORNWALL-by-GUILHEM.jpg


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nwickliff

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Joined 2020
geoffkait said:
How to increase the absorption frequency bandwidth of a Helmholtz resonator by 100%.

https://www.nature.com/articles/s41598-019-49222-w
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Interesting read. 2x the Q isn’t nothing but I believe my thumbtack analogy remains cogent. Interesting use of two separate cavities at what seem like different frequencies to increase broadband absorption. Now to find some lossy material. They used foam. I don’t know that I want to use my rockwool. Maybe I’ll move the poly that’s on the bottom to the mouth of the neck and measure again.
 
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geoffkait

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Joined 2004
machinadynamica.com
I already mentioned the best lossy material, it’s hollow fiber wool. Grapefruit size.

Room Lens by Argent was popular with audiophiles some years ago … 1997 Yikes! 😲 Quite a clever design AND they can be replicated by the intrepid audio enthusiast.

1997 was the year I exhibited by Sub Hertz iso platform in Vegas.

https://www.soundstagenetwork.com/noisy14.htm
 
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tubelectron

tubelectron

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Joined 2008
As you are speaking about acoustic absorbent material, I use this - currently available in DIY supermarkets :

1704486074405.png


Here are the specs :

1704486178863.png


This is recycled Cotton Wool - I use it for years in all my speakers with success, and moreover it's harmless - unlike Rock or Glass Fiber Wools...

1704486436787.png


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nwickliff

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Joined 2020
tubelectron said:
@nwickliff : are you still here ? ;)
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Yes, sorry! We have all the kids this week so busy house, plus just spent the last day making 5 more absorption panels, removing almost everything from my room and measuring the introduction of all the panels and then my resonators.

I’ll have measurements posted soon.

Umik 1 or 2 from miniDSP
$100 bucks and you’re off to the races.
What laptop do you have?

Umik 1 is usb A and 2 is usb-c
Something to consider depending on what type of ports you have.
 
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tubelectron

tubelectron

Member
Joined 2008
nwickliff said:
Yes, sorry! We have all the kids this week so busy house, plus just spent the last day making 5 more absorption panels, removing almost everything from my room and measuring the introduction of all the panels and then my resonators.

I’ll have measurements posted soon.

Umik 1 or 2 from miniDSP
$100 bucks and you’re off to the races.
What laptop do you have?

Umik 1 is usb A and 2 is usb-c
Something to consider depending on what type of ports you have.
Click to expand...

Aw ! Well, no problem @nwickliff ... :D;)

I see :

1704579836940.jpeg


1704579857491.jpeg


My laptop is an ASUS VivoBook 17 (W11 pro), and it has the USB-A and USB-C connectors.
I'll also check what USB ports have my external soundcard (ESI Maya22USB).

Thanks for your input ! :cool: And good luck for your 50Hz damping/trapping adventure...:)

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