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Diaphragmal LF Absorbers (aka LMBT) damping and calculation

bo_knows

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I'm 60% there, 2 smaller corner boxes are to be built. It's a time-consuming process...
The first impression by ear is that those 3 boxes work. If I can describe the difference in what I'm hearing will be like comparing a ported bass reflex subwoofer with a sealed design. The Bass is tighter and it's easier to distinguish or hear the kick drum and the bass guitar. Those two instruments a lot of time overlap in the song and it's hard to tell them apart when that happens. It just sounds like one deep bass note if you know what I mean. The biggest shock was the gain in the upper frequency and clarity. I assume this is due to the removal of the original 2 large fiberglass panels which made mid to high frequencies tamed (fewer reflections). I like the new sound but my right ear starts to get fatigued now after playing 30-40 minutes where before I could withstand it. That is what I'm learning about small-room acoustics. It's like a balloon. You squeeze on one end and it will bulge on the other. LOL. So far, I can live with the tradeoffs and will complete this project. Here's the pic of the room and boxes. They are not fully finished. The front part will be covered with a frame that will have black fabric speaker cloth material for a more finished look.
Once I build all the boxes and have time, I'll perform the REW measurements just to see if there's any improvement. The problem is that I didn't document this process with proper "before" and "after" measurements (the microphone being in the SAME SPOT is a crucial part). I just don't have the time or patience or knowledge to document this the right way.
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FeddyLost

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If I can describe the difference in what I'm hearing will be like comparing a ported bass reflex subwoofer with a sealed design
In fact it's an indication of correctly working absorbers. Resonanse tails are shortened. Reduction of peaks might be not so audially evident.
The biggest shock was the gain in the upper frequency and clarity
It's hard to identify exact reason without proper exploring of measurements "before and after". In my case LMBA was mounted behind the inner shell and worked in bass area only.
I like the new sound but my right ear starts to get fatigued now after playing 30-40 minutes where before I could withstand it.
Personally I'd like to avoid such clarity. Maybe some nasty resonanses was induced?
Try to cover membrane with some kind of foam and check if it will change fatigue.
I'll perform the REW measurements just to see if there's any improvement. The problem is that I didn't document this process with proper "before" and "after" measurements (the microphone being in the SAME SPOT is a crucial part). I just don't have the time or patience or knowledge to document this the right way.
Unfortunately any work regarding some "not-so-obvious-materies" require some registration of intermediate steps.
Otherwise it's tought to identify if you are going the right way or it's just placebo effect.
 

bo_knows

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It's been crazy busy at work so I didn't have time to provide the update.

I'm (I think...) 100% done. The last step was to create a nice frame with the speaker cloth material to cover the front of the membrane.
Overall, this is the best sound I have achieved today in my room. Working on this project and swapping the old (fiberglass panels) treatments exposed some of the "shortcomings" and reduction of high-frequency reflections that took some "life" out of the sound. As far as bass, I like what I'm hearing. These things work and they work well. I know, I need to back this up with some REW diagrams and I will when time permits. :)
If I was to do it all over again, I would create all boxes to Tim Farrat's specifications and dimensions.
This way, I would be able to fit 6 of them and they will all match visually. Oh well...live and learn.
Highly recommended as a DYI project. Making them (5) took a long time, I would say I spent 8 hours or more making one box from start to finish. I have no idea how FeddyLost could build 60 of them!! My hats off to you sir!
 

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Niklasmagnus

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It's been crazy busy at work so I didn't have time to provide the update.

I'm (I think...) 100% done. The last step was to create a nice frame with the speaker cloth material to cover the front of the membrane.
Overall, this is the best sound I have achieved today in my room. Working on this project and swapping the old (fiberglass panels) treatments exposed some of the "shortcomings" and reduction of high-frequency reflections that took some "life" out of the sound. As far as bass, I like what I'm hearing. These things work and they work well. I know, I need to back this up with some REW diagrams and I will when time permits. :)
If I was to do it all over again, I would create all boxes to Tim Farrat's specifications and dimensions.
This way, I would be able to fit 6 of them and they will all match visually. Oh well...live and learn.
Highly recommended as a DYI project. Making them (5) took a long time, I would say I spent 8 hours or more making one box from start to finish. I have no idea how FeddyLost could build 60 of them!! My hats off to you sir!

They look great nice work!

Would love to see some REW measurements when you find the time.

BR
Niklas
 
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