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Discussion Starter #1
I was bored so i decided to take some measurements.

Sub is an adire brahma 12.

Box is .66 cft

The blue line is no poly

the black line is with poly


What caught me off guard is the poly made the sub LOUDER

I expected the increase in lower end performance but not the volume increase.

pay attention to this part.

The blue line was measured with a fixed mic position and the radio volume at 28.

The black line was measured with identical mic position(mic was not moved during the addition of the poly) and the radio volume at 26! 2 clicks DOWN, which equals about 3 db in my truck.

I reduced the radio volume 2 clicks to make the measurement amplitude align better. I am seeing a pretty substantial increase in volume and extended low and upper bass.


Both measurements were taken with identical mic position.

I did the swap with the sub facing up and did not move the box at all. I simply removed the sub, added poly then remeasured. After seeing the increase in over all volume I turned the radio down 2 clicks so that the graphs would line up better.

I had an almost 6 db gain at 30hz!

If i didnt have thta room mode at around 88hz i have no doubt that area would have gained amplitude as well.


Im familiar with poly and have used it often but actually measuring the results has me shocked at the added performance. I would have never guessed it would add volume through the entire sub range.

I was looking at a video online and it seemed inconclusive. This seems pretty darned conclusive to me.

For anyone interested, I used the blackhole "STUFF". Thats literally the name. The rep got all huffy when i called it shredded denham lol and started ranting about acoustical this, acoustical that.


Have you guys ever seen poly add this much performance?
 

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Why not show the real apples to apples graph? I understand your reasoning, but a graph with them both at same head unit volume would be more revealing.
 

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Discussion Starter #4
Why not show the real apples to apples graph? I understand your reasoning, but a graph with them both at same head unit volume would be more revealing.
The graphs were for me. I wanted to see apples to apples frequency response comparison and to do that I needed the graphs to be at the same amplitude. Posting here was an afterthought.

I thought it was pretty neat how much sensitivity it added. If course if you build a proper sized box you dont need poly, but for those working in tight spaces its pretty great.
 

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Discussion Starter #5
Why not show the real apples to apples graph? I understand your reasoning, but a graph with them both at same head unit volume would be more revealing.
It's almost over. I got a sub that will work and as soon as I iron out how to make it fit and get my mids installed and tuned I'll be out for a couple years.
 

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Does it sound louder to your ears? Try adding more stuffing.
 

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Drop 1, I think you are single handedly keeping diyma alive with your threads... Lol
 

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That is funny. That 'stuff' is exactly what I've been saving up from my meal delivery Freshly to be placed in my outer doors to do the same as what they claim. "Superior resonance control". And it already comes wrapped in plastic for water protection.

https://photos.app.goo.gl/j3XfYTmNpEiz3hQz7
 

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Discussion Starter #12
That is funny. That 'stuff' is exactly what I've been saving up from my meal delivery Freshly to be placed in my outer doors to do the same as what they claim. "Superior resonance control". And it already comes wrapped in plastic for water protection.

https://photos.app.goo.gl/j3XfYTmNpEiz3hQz7
I've never seen it treated for door. If I didnt already have my doors covered in 1.5 inch thick foam/mlv tiles I would try it.
 

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Discussion Starter #13
Does it sound louder to your ears? Try adding more stuffing.
Box wont hold anymore.

But yes, I can hear it. It's almost like I added a second sub. 40hz and down is night and day.

To top it off, I can turn it up louder without breakup so I gained somewhere around 7 to 8db.

That's more than adding a sub or porting.

Cant wait to get it ported.
 

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That is funny. That 'stuff' is exactly what I've been saving up from my meal delivery Freshly to be placed in my outer doors to do the same as what they claim. "Superior resonance control". And it already comes wrapped in plastic for water protection.

https://photos.app.goo.gl/j3XfYTmNpEiz3hQz7
Thats to funny, I have been saving that from my Freshly meals as well, have a whole closet full of it waiting to go into vehicle lol
 

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Thats to funny, I have been saving that from my Freshly meals as well, have a whole closet full of it waiting to go into vehicle lol
I'll have to keep hoarding them. Whenever I get a new vehicle it could be used in a lot of places. Trunk, floor, doors, behind panels. Just stuff the whole damn car :)
 

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Does it sound louder to your ears? Try adding more stuffing.
Box wont hold anymore.

But yes, I can hear it. It's almost like I added a second sub. 40hz and down is night and day.

To top it off, I can turn it up louder without breakup so I gained somewhere around 7 to 8db.

That's more than adding a sub or porting.

Cant wait to get it ported.
7 or 8 db just from polyfill? That's a huge just and doesn't sound right at all
 

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I'm in the middle of doing the same experiment and will be posting a video on my YouTube channel.The box I have has two Alpine type r 12's at around 1.8cuft. So I lined the walls with about 5 layers(approx 2lbs) of polyfill.Just gotta get around to taking measurements which I'll do once I get the A-pillars back in.Right now the system is disabled.
 

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I can't find the link to this, so here's the pdf. View attachment 251613
Or not.
Thanks for sharing the pdf. I used to subscribe to Car Stereo Review and Car Audio back then and remember reading stories by Tom Nousaine. Also used to mail order from MCM... that seems like from another time - I'm 56! What did we do before internet?

And back on topic I've just always preferred the sound of a sealed box and have been stuffing with polyfill probably since about the time the CSR story was published! Gotta stuff (within reason)!
 
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