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Discussion Starter · #1 ·
Hi, I'm about to finish two Dayton 18" subs in Erich's 4 cubic foot boxes.


I thought I needed to add about 2 lbs of Polyfill to each. Is this correct?


If I don't add Polyfill, do I need to line the inside of the box? I've already glued and veneered it, so I'm hoping I don't have to.


Thanks

Dan
 

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You shouldn't really "need" to stuff a subwoofer enclosure, I think most would agree.

That being said, I usually throw a Wal-mart pillow in the back part of my boxes, they don't budge jammed inside the bracing.


I don't glue it or use a lot though, as too many will change the Q of the box.
 

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Discussion Starter · #3 ·
I did a search and read that the Qtc (I think that's what it's called) of the 4 cu/ft box is .6.


From what I understand, it should be .7.


So maybe I'm close enough already? Seems like if I added anything it would be minimal. But I don't know how much that would be.


I'm itching to finish these tonight and get them up and running.


Dan
 

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http://www.data-bass.com/data?page=content&id=79

 
Quote:
 

Overall, stuffing or damping the inside of a subwoofer’s enclosure is generally a good idea to prevent the internal reflections inside of the enclosure from bouncing around and coloring the response and sound. If you are looking for the utmost in uncolored and well-damped sound or if you intend to use the system extra high in frequency up into the lower midrange, it is recommended. If you are trying to be as absolutely loud and efficient as possible, then leave it out. 

 

In general, there is probably a sweet spot for most systems where the system's major response issues are cleaned up and damped, but further addition of material will only serve to further decrease efficiency.  Unfortunately, finding this sweet spot probably involves trial and error or other testing.
 

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Discussion Starter · #5 ·

Quote:
Originally Posted by Mrkazador  /t/1524882/quick-question-for-build...b-boxes-polyfill-or-no-polyfill#post_24545350

http://www.data-bass.com/data?page=content&id=79

Thanks. I just gave it a read. I'm still not exactly sure what to do as there seems to be pro's and cons. Here's my scenario:


I'm will have two 4cu/ft flat pack subs with the Dayton HO drivers. They will be in a room that is about 1,800 sq/ftt with an open stairway heading downstairs. I will be crossing them over the the L/R/C speakers at 80hz. (The surrounds will be higher but I'm assuming that is irrelevant.)


It sounds to me like a bit of Polyfill would help. But I have no way to measure how much. Maybe I should just leave it as is? Or put 2 lbs in each?
 

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Two sealed 4cuft enclosures in an 1800sq/ft room?? I would seriously consider building some ported enclosures as 1800sq/ft is a monster of a room!
 

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Discussion Starter · #7 ·

Quote:
Originally Posted by Martycool007  /t/1524882/quick-question-for-build...b-boxes-polyfill-or-no-polyfill#post_24546367


Two sealed 4cuft enclosures in an 1800sq/ft room?? I would seriously consider building some ported enclosures as 1800sq/ft is a monster of a room!
Whoops, I made a mistake there.


The room is 19 feet long from front to back and 11' 6" wide with an open set of stairs. So 220 square feet.


1,800 was cubic feet, factoring in ceiling height.


These subs should be more than fine. The boxes look huge in the room.
 

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Quote:
Originally Posted by dftkell  /t/1524882/quick-question-for-build...b-boxes-polyfill-or-no-polyfill#post_24546435


Whoops, I made a mistake there.


The room is 19 feet long from front to back and 11' 6" wide with an open set of stairs. So 220 square feet.


1,800 was cubic feet, factoring in ceiling height.


These subs should be more than fine. The boxes look huge in the room.

I figured that was what you meant!


Yes, those duel sealed Dayton HO18's should do pretty well in an 1800cu/ft room. I would highly recommend getting an iNuke3000dsp or a balanced MiniDsp 2 by 4 with advanced plug in along with a good amp. That way you can boost the low end and EQ the overall response to be flat in your room. Might want to pick up some measurement gear as well!
 

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Discussion Starter · #9 ·

Quote:
Originally Posted by Martycool007  /t/1524882/quick-question-for-build...b-boxes-polyfill-or-no-polyfill#post_24547087


I figured that was what you meant!


Yes, those duel sealed Dayton HO18's should do pretty well in an 1800cu/ft room. I would highly recommend getting an iNuke3000dsp or a balanced MiniDsp 2 by 4 with advanced plug in along with a good amp. That way you can boost the low end and EQ the overall response to be flat in your room. Might want to pick up some measurement gear as well!

Thanks Marty.


I've already purchased two of the Dayton 500 watt plate amps. They have some parametric EQ if I want to boost the low end, or cut a nasty peak. I have Fuzzmeasure to measure my room. It's one of the best--and most fun--pieces of equipment I've purchased for my home theater.


I have a pair of 10" subs that I've built (in my signature) that I've measured in multiple positions and configurations in the room while building these. I was able to get a pretty smooth response with nice extension from room gain. I'll post a picture of the graph when I'm home tonight. Ironically, the best results were achieved when both subs were in the rear corner of the room back to back in a mock dual opposed configuration. I never would have guessed that. When I have the dual 18's in the room, I think the results will be very nice. We'll see when they're in place.


Unfortunately, I still don't have a definitive answer regarding Polyfill yet from this thread. PE suggested .5 lbs per cubic foot. I saw another really nice build on HTShack where the guy used .75 lbs per cu ft. And the data bass article above doesn't really specify how much to add if someone chooses to do so.


I'm a perfectionist and I thought there would be a definitive answer on this to achieve the optimal results. Maybe .5 is a good compromise between a flatter response and good extension and efficiency.


Thanks,

Dan
 

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Grab the salt and pepper........how much do you put on your fine steak? Depends on your tastes......


If qts on your driver and box are low enough then you can go in either direction ie. more/less depending on YOUR tastes......experiment.


I'm just lining with 1 inch Linacoutic RC........because I have it, it's free and is easy to use spray adhesive for attaching. If I'm not happy with result, I'll add another inch and stuff polyfill pillows if need be. Knocking down resonance in box is my only goal since qts values are fine.
 
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