Subwoofer question

[neilmaui]

just purchased a Sub kit from Parts Express and it states this in the description...The sealed enclosure design creates a subwoofer system with a Qtc of 0.644 and an f3 of 40 Hz when used with the Dayton Audio RSS460HO-4 and minimal fill. Adding five pounds of Acousta-Stuf will create a critically damped subwoofer system.

my question is this...what is a 'critically damped' subwoofer ? do I need the extra fill and what does it give me ? its a 4cuft box with the Dayton Audio 18" Reference Series HO Subwoofer and the Dayton 1kw plate amp.

thanks!

[tcpip]

just purchased a Sub kit from Parts Express and it states this in the description...The sealed enclosure design creates a subwoofer system with a Qtc of 0.644 and an f3 of 40 Hz when used with the Dayton Audio RSS460HO-4 and minimal fill. Adding five pounds of Acousta-Stuf will create a critically damped subwoofer system.

my question is this...what is a 'critically damped' subwoofer ? do I need the extra fill and what does it give me ? its a 4cuft box with the Dayton Audio 18" Reference Series HO Subwoofer and the Dayton 1kw plate amp.

thanks!

A Qtc of 0.64 is good. Adding more filling will make the enclosure behave like a bigger box, lowering the Qtc. Maybe it'll reach 0.5, and that's what the author is referring to as "critically damped".

IMHO, the precise Q can be anywhere between about 0.5 and 0.7, and you'll not know what's "right" for your room. So, leave it as it is, do some in-room measurements of room modes, and then do some room correction using DSP. Plenty of devices available to let you do it. That is what really matters to get the sub fit into your room.

[neilmaui]

so Ive just finished building this sub and have a question regarding filling....I attached ( spray glued) soft reconstituted padding ( looks like chopped up blue jeans fibres ) its about 3/4 inch thick on all interior surfaces of the cabinet. Now I want to fill with extra fibers and not sure what to use....I did initially fill with glass fiber insulation , the pink stuff, it came on a roll and I pulled it apart to tease it into a more open weave but not sure if the fibers will get bounced around inside the cabinet and end up messing with voice coils, cones etc??? I know I could just order some acousta stuff....but I also have some old polyester pillows...is that filling essentially the same stuff?

[agrippa]

I have used fIberglass but I prefer https://www.parts-express.com/acoust...b-bag--260-330. I bought 50lbs years ago from Parts Express and might not ever need more. Fiberglass does not improves bass as well IMO. Pillow stuffing... depends on what it is. Some is very light weight. I like material that is all natural.