polyfill/pillow/eggcrate question

**jsink77** · **10-19-09, 03:35 PM**

Just about done with my box and I do not have a good understanding of the different 'fill' materials and which I should use. I have the following

mal-x gen II - ep2500 amp
11.75 internal volume (this has bracing, port, and sub already removed - 14.28 cu ft total internal vol)
2 - 5.875 ID ports that are 35 inches long
Fairly large room - 25 X 16 X 8.5 ft

Would I gain anything in this ported enclosure by placing pillows/polyfill in at the 1 lb/ cu ft rate? Or should I just put some eggrate bedding material on the walls of the enclosure?

Thanks

**Kevin Haskins** · **10-19-09, 04:14 PM**

Quote:

jsink77 wrote:

Just about done with my box and I do not have a good understanding of the different 'fill' materials and which I should use. I have the following

mal-x gen II - ep2500 amp
11.75 internal volume (this has bracing, port, and sub already removed - 14.28 cu ft total internal vol)
2 - 5.875 ID ports that are 35 inches long
Fairly large room - 25 X 16 X 8.5 ft

Would I gain anything in this ported enclosure by placing pillows/polyfill in at the 1 lb/ cu ft rate? Or should I just put some eggrate bedding material on the walls of the enclosure?

Thanks

Skip the egg-crate, and use polyfill. There isn't a hard and fast rule about the right amount, it depends on the design but for sealed designs I tend to stuff them close to 100%. For ported designs, I look at the model but I always use at least 10-20%. I use more if I'm trying to damp the port output because of a peaky design. For your design, you shouldn't need anywhere near that much. Overstuffing it will just rob port output and you don't need the extra volume.

Kevin Haskins
Exodus Audio

**jsink77** · **10-19-09, 04:55 PM**

Thanks Kevin - what exactly do you mean by 10-20%? If I assume 1lb/cu ft that would be about 12 lbs for 100% stuffing. Then 10-20% would be 1.2 to 2.4 lbs. Is that what you mean? Not sure how to correlate 10-20% to some real world measurement (ie 10-20% of what?)

**Kevin Haskins** · **10-19-09, 05:00 PM**

Quote:

jsink77 wrote:

Thanks Kevin - what exactly do you mean by 10-20%? If I assume 1lb/cu ft that would be about 12 lbs for 100% stuffing. Then 10-20% would be 1.2 to 2.4 lbs. Is that what you mean? Not sure how to correlate 10-20% to some real world measurement (ie 10-20% of what?)

Sorry.... I talk about this stuff so much that I forget that not everyone knows what I mean.

About 16oz. of poly-fill per cubic foot is 100% fill. So... figure 2oz./cubic foot for 10-20% and you are close enough. The fact that you are off a little one way or another means very little. The differences are swamped by the room issues anyway.

Kevin Haskins
Exodus Audio

**jsink77** · **10-19-09, 05:03 PM**

thanks

**Ryan Anderson** · **10-19-09, 06:31 PM**

I read here a while back not to stuff vented enclosures

**Kevin Haskins** · **10-19-09, 06:42 PM**

Quote:

Ryan Anderson wrote:

I read here a while back not to stuff vented enclosures

Not from me. There may have been a post where I said it wasn't necessary because how much I use depends on the circumstances but I use fill in pretty much every enclosure.

It isn't a world changer though. I tell people to experiment. It doesn't take a lot of effort to put fill in/out.

Kevin Haskins
Exodus Audio

**Mike P.** · **10-19-09, 06:47 PM**

Quote:

I read here a while back not to stuff vented enclosures

Depends on how much. It's my understanding you don't stuff a vented enclosure at the rate of one pound per cu.ft like a sealed enclosure unless there is a design issue like a peaky response.

**Ryan Anderson** · **10-20-09, 02:20 AM**

how much efficiency is lost in the process?

**evilskillit** · **10-21-09, 01:57 PM**

I made a pair of ported subs that had a fat peak around 60hz and started falling off quickly below 45hz. I have put some EQ on them since then but I also took out the drivers and stuffed the enclosures fairly heavily. They are now somewhat quieter but the bass is so much more even, combining the stuffing with eq they now actually clearly play a full range of bass notes instead of being one note wonders, which is fun at first but gets old quick.

**fredk** · **10-24-09, 11:40 AM**

How do you tell if you have peaks generated by a design issue, close miking of the driver and port?

**evilskillit** · **10-24-09, 03:43 PM**

Well mine showed up in the WinISD and was also noticeable simply by listening, but yes if you have not modeled the driver in Unibox or WinISD or something or can not the best way is by measuring frequency response with a mic.

Mine had a hump because the speakers I was using were less than ideal, and due to size/space limitations I did not want to make them any bigger than 4 cu ft or so, and the peak wasn't really evened out till they were way too large for my tastes, probably over 8 cu ft. Also this caused excursion issues all over the place. So I went with a smaller enclosure and added some stuffing, then EQd the peak down and called it good.

FWIW here are the threads that pertain to my original cheapo spare parts sub build. And the thread where I talk about stuffing it a bit.
https://www.hometheatershack.com/for...ng-around.html

https://www.hometheatershack.com/for...ney-nasal.html

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