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Discussion Starter · #1 ·
For a while I've been trying to wrap my head around stuffing vs lining. My understanding is that typically a ported sub should be lined and a sealed sub stuffed. I have seen some recommend stuffing a ported sub (perhaps taking quality over spl?) -- using less than 100% fill (Kevin Haskins recommended in some application notes for Exodus drivers), And this dated article by Nousaine talks about filling a ported sub: http://www.nousaine.com/pdfs/Box Stuffing.pdf

I found an interesting post from Bill Fitzmaurice re: stuffing vs lining a sealed box:
"Always line, otherwise internal above bandwidth internal reflections back to the cone will color the output. Stuff the box if the Q is above .7, to reduce Q and tame boomy response. " and "... Lowering Q with stuffing tames boomy response, but at the cost of sensitivity...."

In another thread where I've asked similar question- the recommendations seemed to vary between some foam, 2" 703, 4" 703, filling the box with 703... I'm thinking if rebuilding a couple cabinets I have (sealed Exodus Tempest 15" and Mal-X 18") -- and I found myself thinking, what's so different about filling a box with 703 than filling with polyfill? (I imagine 703 would be more absorptive and much more expensive)...

But my real question is - how are results from filling..lining..various amounts... actually quantified? I've read some people say "put in x polyfill, try more, try less - see what sounds right". But in measurement terms the ideal balance would be what? a flatter frequency response? I'm not sure what reflections would look like in a measurement. A muddy transient response??

Maybe I need to invest the time to do some comparisons but I'm just not sure how audible differences between 50% fill, 100% fill or a box full of 703 would really be?
 

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Elite Shackster
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There is only one real perfect solution to this dilemma for you, and thats to simply try it. If you have a DIY sub you can experiment on, then my suggestion is to spend a day doing it. All the reading in the world is no substitute for experience, and doing the practical experimentation helps put what you read into perspective much better.

It may also be worth keeping in mind that a great many high end manufacturers use fibre fill in their cabinets. Lining is generally used to absorb and cure resonance issue, which is especially good in ported designs or unusual shaped cabinets i.e very long and slim designs etc. Fibrefil is used to make a subwoofer sound deeper and cleaner. Which you wish to use is dependant on your own requirements.
 

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Discussion Starter · #3 ·
It may also be worth keeping in mind that a great many high end manufacturers use fibre fill in their cabinets. Lining is generally used to absorb and cure resonance issue, which is especially good in ported designs or unusual shaped cabinets i.e very long and slim designs etc. Fibrefil is used to make a subwoofer sound deeper and cleaner. Which you wish to use is dependent on your own requirements.
I wish I could see more of the internals of some higher-end subs to see what they do.

The sub cabinets (ported) that I've seen use lining........ but pretty much as little as possible. It really seems like it's the one component that manufacturers tend to cheap out on......... But then again, for all I know, they've determined that 1/2" is enough and 1-2-3-4" doesn't make much difference.

It's much like poly-fill vs Acousta-Stuf debate. Many people say makes no difference and others think it's a big deal. I just can't see how it would make much difference.
 

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In general...Any cabinet you build will have some internal resonances, reflections, standing waves, etc. The bigger your cabinet dimensions the lower in frequency some of these will occur. These cause cancellations, blips, or spikes in the frequency response and usually ring out, which is bad. Ports also have a resonance which acts negatively as well. Adding stuffing to an enclosure, or dampening will cut down on these or eliminate them entirely in some cases, since the sound instead of bouncing back and forth around the cabinet it has to go through the material multiple times. IMHO this is the best reason to use fill materials as this can clean up and dampen your response and improve the sound. The big tradeoff is that it cuts down on system sensitivity and efficiency. As usual there is no freee lunch in audio. It can also lower the system corner, even for ported subs slightly but again efficiency is lost in the process. Most of the apparent deepening of response comes from the top end efficiency being cut. The best way to do this IMHO involves measurements and adding material until the detrimental enclosure related issues are sufficiently damped and stopping there so you don't sap more efficiency than needed.
 

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Discussion Starter · #5 ·
Hey Ricci - long time no see. Thanks for your info. I think the one phrase that you mentioned that stands our is "sufficiently damped" - and achieving that isn't something you can easily simulate.

Thanks for your response.

The reason why this interests me so much is I used to have this "holy-grail type pursuit" for the most bass.. the deepest bass. Efficiency -- and now my interest has shifted more towards quality, good transient response, balanced bass and tweaking that.

I'm more willing to sacrifice some SPL for improving the quality these days.. :)
 

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Elite Shackster
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Now thats what I like to hear :T Anyone can stick a massive driver in a huge cab to rock da house, but fine tuning to a specific requirement is a little harder :neener:

We can say everything and anything about this, point you to numerous links and discuss this till the end off time, but you still wouldnt truly understand till you experiment yourself, and audibly experience the changes for yourself. Only then do you get a feel for what it does, and crucially, form your own opinion on the subject based on your own experience. Theory is fine, but talking about something and doing it are different things entirely.
 

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Discussion Starter · #7 ·
So since I'm in agreement I need to find the time (yeah time...) to test....

Who has done comparisons and spent time trying to find the magic balance? Dan - I assume you've played this game before? :)

For my 3 ways I bought WAY TOO much bonded-logic/ultratouch insulation - so yet something else to play with.

 

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Elite Shackster
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I have spent a bit of time messing. Most of what I did what based around the audible change, as most of what I read at the time suggested this was the biggest impact and the main reason one would use the stuff. I did do some in room before and after measurements, but from memory there was little measurable difference.

I use polyester fibrefill though, not the thicker insulation stuff. I now use the stuff in every sub I do, it certainly helped the MK sub sound cleaner, and thats the main effect I observe, a sealed sub will sound a touch deeper and cleaner. Ive used it in ported subs, not least to try ensure no resonances are audible from the port, but I have never bothered to try a ported sub empty to compare.
 

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I think installing a liner or stuffing is a holdover from the manufacturers who built two and three way speaker cabs and had to eliminate internal reflections from the mid and high freq drivers.
Subs, especially ported, benefit from stuffing to clean-up some reflections. In sealed boxes, stuffing can be used in a small box to make it "appear" larger to the driver, that's one of those sonic mysteries I'm not sure I believe.
I use enough liner/stuffing to make the inside of the box sound dead like I want the walls of the box itself to sound, no added squeaks, rattles, thuds, or clunks.
I've read that stuffing also benefits some reflection of frequencies back through the driver cone and surround. I don't know that I've ever (heard) anything coming through the cone, especially an aluminum or titanium cone.
In the end, I figure if you're going to use ROOM treatments you should use box treatments too. It's only fair.
 

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I have a question here. I've read repeated statements that putting the proper stuffing in a cabinet makes the driver "see" a larger internal volume. Of the posts I've seen, it seems the conclusion is asserted without argument or explanation that I could see - it could have been there but rolled right past my vague understanding of physics - I took a college class dismissively called "Physics for Poets," though it was taught by a full Professor of Physics. Not sure why I stuck that information in there, but . . . . Well, onward. So, I've been rolling this stuffing question with the few tools of understanding of physics I have and have a thought/question on the possible reasoning.

Might it be that the stuffing is excited by the air moving (compressing/uncompressing) inside the cabinet. In a state of excitation, perhaps the stuffing heats up (one of the laws of thermodynamics?) and that causes the air to appear less dense; thus the box seems bigger? Frankly, that seems bogus, too, but that's another idea to throw against the wall.

Larry
 

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Elite Shackster
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Funny you should come up with that as its more or less how things work, as explained in the link in post #1

The term about the driver seeing a larger cab comes mainly from the fact the resulting sound change is akin to placing the driver in a larger cabinet. That is the effective result of using the wadding.
 

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Dan, this is where my liberal arts education limits my ability to perceive, I guess. It seems that post #1 hints at it, but no one seems to identify the action that makes it occur. I suppose it makes no difference in some respects, but my mind has been unconsciously busy with figuring out the action.
BTW, I'm sitting down to spec out a second cabinet for my second AE AV15 driver. I'm going to build another 2.1 ^ft cabinet. Any thoughts?
Larry
 

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Elite Shackster
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Well, as a drivers motor works it generates heat, which in turn heats the air inside the cabinet. The theory goes that the wadding resonates and acts to dissipate the heat, and keep the air (and motor) cooler, just as it would in a larger cabinet with a larger internal volume of air. A cooler system will suffer less from the effects or power compression, so will remain cleaner in its output.

IIRC, you have a thread on your own build dont you? Post in there and I will reply in your thread rather than take this one off topic :T
 
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