Sadly I don't have a TL right now so I had to guesstimate the effects by ear. I realize its not the most accurate method but with this test if you cant hear the effects to the ear then it doesn't matter anyway.
Using this 6th order I just built I wanted to lower the tuning of the 31hz side. Using this chart Polyfill Chart from the enclosure sticky I started by placing 32 oz of poly in my 2.2 cu ft enclosure. I couldn't notice much if any difference. If it had worked as it did in the chart I should have had a similar perceived increase as they did which was around 29%. 29% increase on my 2.2 box would have made it 2.8 and tuned to 27.5hz instead of 31hz.
Taking it a step further you notice in the chart he has an increase in enclosure size up to about a 1.5 pound to 1 net foot ratio. Going off of this I increased the amount of poly to 50oz. Thats 1.42 pounds of poly per net foot of my enclosure. When he tested a 1.4 to 1 ratio he saw a 43% increase in enclosure size. If that were the case in my box I should have had a net size of 3.15 cu ft and a tuning of 26hz. Very simply I didn't have that result.
Using my handy access panel I tested no fill at all and up to 50oz.
Using test tones I sought to find when sound became noticeable and if there was any change at all.
In both cases (0 fill and 50oz) the tuning was not lowered at all.
-A very light humming became noticeable at 27 hz. Very light, not real bass by any stretch.
-At 30hz the bass was reasonably noticeable but not loud at all.
-Real bass started in the Car at 32hz.
-More importantly, output around 34-37hz suffered in the box when it had poly. My guesstimate was proximately a 3-4 db loss at that frequency.
-There was no perceived increase at any of the lower frequencies.
My conclusion, it doesn't work, or at least doesn't work in a parallel 6th order.
that sounds more like your having cancellation issues than proving the poly fill doesn't work.
i really don't like the idea of using it anywhere other than a sealed chamber.
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