14 replies to this topic

[HERTZ-1]

Please share your opinions and experiences with using dacron (white fluffy stuff, acrylic filler, sub box stuffing, etc).

Should it always be used? Should it never be used? Sealed? Ported? MDF? Fiberglass? If the box is too small?

Let's hear it all!

Edited by HERTZ-1, 13 May 2012 - 10:59 PM.

[peaandham]

Dacron will make the sub act like it is in an approx 20% larger box, so you need it is when your box is too small.

[occa]

Geez i've never heard that ^^^^^ before.

i thought an Aperiodic vent would make the sub act as if the box was ~%20 bigger, but not Dacron

you learn something everyday!

i have heard it can help prevent standing waves if your baffle and rear of the box is parralell, and i've also heard it can help to reduce port noise if your vented box has strange or uneven surfaces inside it


edit:spelling

Edited by occa, 14 May 2012 - 12:51 PM.

[Dylby1]

I will be using it in mine, as much for standing waves as the fact it's Gunna be a bit small.

[Captn_Awesome]

Ask Tiger

[SQXPRT]

It does have some effect on the apparent "volume" of the box.- I suspect 20% is somewhat optimistic.

the actual effect is to decrease the compliance of the box.

Glass fibre wool works better, but it's heavier and itchy.

[HERTZ-1]

As in pink batts? (AKA roof and wall insulation?)

Posted from my portable device.

[TMM]

For a sealed box it'll make it act like a slightly larger box.

For ported the best way is to try with and without.

[TERRA Operative]

In a sealed box, I loosely fill the box.
In a ported box, I just line the walls so the ports aren't restricted.

[JohnDB]

I Dynamatted mine (sealed enclosure), rear panel bottom panel and side panel, the damping material in each dimension will absorb rear reflections which would otherwise attempt to transmit through the cone of the sub(s).

Sounds great.

Its a different story for ported enclosures.

[HERTZ-1]

Thanks for all the comments guys.
John, I was considering doing that. Because I'm doing fiberglass spare wheel well and false floor sealed, I'm doing double 18mm baffle braced to the 18mm base, which will unfortunately be parallel with the baffle.
A few people have said don't use RoadKill inside a box, but one person said use it, but cut curved lines in it to prevent standing waves.
Did you test before and after dynamatting?

[Big_Valven]

Guys, I think we need some perspective. We're talking about 80Hz and down, 80Hz has a wavelength of around 4.3 metres - many times larger than your subwoofer box and large enough that cutting curves lines in Roadkill and stapling down ~50mm of insulation is going to make absolutely no difference to the idea of standing waves. As frequency gets lower that wavelength only gets longer. It is only when the wavelength is smaller than any dimension of the box that you really need to consider that sort of thing...

Roadkill and Dynamat are mass-adders. All you stand to do by sticking it inside the box is to make the timber / fibreglass heavier. If your box is of suitable construction, there's not an audible reason to do it.

Pulse-R is on the money. It's not really a life-or-death product, it may make a small difference in some cases, or it may do nothing at all to the sound. I nearly always stuff with polyester filling (non-fibreglass household type insulation) because I like the feel of it and I want the subwoofer to stay warm in winter

Don't forget that "Dacron," mineral wool, fibreglass and polyester insulation are all different products too (albeit virtually the same to use in this application.)

[~Spyne~]

It's been said before, but some people have obviously missed it...
There are no standing waves in a normal subwoofer enclosure.
Think about the frequencies the sub is playing; generally up to 70-80Hz. Now work out the wavelength of that frequency; 80Hz = 4m!!
Even at 1/2 wavelength, you still need a box that has a dimension of 2m to get a standing wave (standing waves in a box only occur at multiples of half-wavelength)
Dacron can change the compliance of the enclosure, which has an effect of making the 'box' seem larger than it really is. This increase in apparent volume is generally quite minimal, a 10% increase is about right for the vast majority of applications.

[HERTZ-1]

Thanks Callum and Adam. You've been very informative.

so bottom line, if the box is a bit small, stuff it. lol

[SQXPRT]

yes, stuff it. but make it a bit small on purpose perhaps :evil:

as to the standing wave theory - we're not talking supression of fundamentals, but of the harmonics associated with distortion.

5th harmonic of 80Hz = 400Hz. this has a 1/4 wave length of ~20cm - enough to build a 1/2 wave in a box. - so dampen the walls
3rd harmonic of 80Hz = 240Hz. This has a 1/4 wavelength of ~35cm - as above
2nd harmonic of 80Hz = 160Hz. 1/4 wavelength = 50cm. the node of many boxes about this size... so the woofer "sees" it's reflection off the walls of the box, creating a null.