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  • Lining sub woofer cabinets?

    From what I believe that I have learned by a lot of reading here, it seems to me that lining of a sub woofer cabinets' interior is unnecessary unless of course, the cabinet is to be of a sealed alignment. I've been lining my ported sub woofer cabinets with a high quality, carpet pad (glued with spray adhesive) in the past, but that has to do more with deadening the mdf panels. Even though well braced, the old knuckle rap test gives a "deader" sound than without the pad.

    I'm building the Voxel sub by Paul Carmody now and my current "wisdom" is not to line the interior with anything.

    Your comments are appreciated in advance!

    Blackie

  • #2
    Re: Lining sub woofer cabinets?

    Originally posted by blackie View Post
    From what I believe that I have learned by a lot of reading here, it seems to me that lining of a sub woofer cabinets' interior is unnecessary unless of course, the cabinet is to be of a sealed alignment. I've been lining my ported sub woofer cabinets with a high quality, carpet pad (glued with spray adhesive) in the past, but that has to do more with deadening the mdf panels. Even though well braced, the old knuckle rap test gives a "deader" sound than without the pad.

    I'm building the Voxel sub by Paul Carmody now and my current "wisdom" is not to line the interior with anything.

    Your comments are appreciated in advance!

    Blackie
    Lining and stuffing can be useful in any cabinet, even ported:

    http://www.moodym.com/audio/fiber.html

    http://www.nousaine.com/pdfs/Box%20Stuffing.pdf

    I usually line and stuff all my cabinets, sealed or ported. I stuff until it starts sounding congested and then back off from that by removing some. YMMV.





    “I cried because I had no shoes until I met a man who had no feet”

    If we all did the things we are capable of doing, we would literally ASTOUND ourselves - Thomas A. Edison

    Some people collect stamps, Imelda Marcos collected shoes. I collect speakers.:D

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    • #3
      Re: Lining sub woofer cabinets?

      I agree that it can be beneficial in a sub cab as well. Be cautious not to over do it (from a sq standpoint). As mentioned above, add some and listen, remove if too much (you will hear when there is too much). I usually am very sparing on fill use, usually resorting to a lining on three non-opposite walls and/or a very light fill with a hollow behind the woofer to the vent (like if the fill were a lining). Play around with different materials and amounts and see what you find to sound the best. Lots of different ways, these are just my ways

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      • #4
        Re: Lining sub woofer cabinets?

        +1 (to thekorvers)

        You can make the argument that sub boxes don't see the frequencies that resonate inside them. I'll make the counter argument that sub's weak point is THD, especially when pushed, and the harmonics sound less bad the more of them you can absorb. Measure an unlined ported box sometime if you thinK the lining doesn't matter!

        That said, bracing comes first!

        Have fun,
        Frank

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        • #5
          Re: Lining sub woofer cabinets?

          You don't stuff vented enclosures, as that upsets tuning and costs sensitivity. You do line them, to damp harmonics that otherwise can reflect back to the cone or out of the port. The only subs that I've found to not benefit from being lined are folded horns, as the horn bends and horn itself act as low pass filters, which filter out above bandwidth harmonics not filtered by the crossover and those created by the driver itself.
          www.billfitzmaurice.com
          www.billfitzmaurice.info/forum

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          • #6
            Re: Lining sub woofer cabinets?

            Thanks for the wisdom guys.. and keep it coming. We get diverse opinions here but all are valid in their own. Here's what I think that I've learned so far: My previous thinking was that since I'm only producing frequencies 100 hz and below that there would be no frequencies that would have a short enough wavelength to reflect around and perhaps out the port. I had not thought about using a lining to contain harmonic distortion inside the cabinet. Great point!

            Second.. I had heard, but not taken too seriously that poly fill could increase the "effective volume" of the cabinet. I didn't get too excited about that as it takes a bit of trust to believe this AND the fact that if I've tuned my enclosure for optimum anyway, why would I want to effectively increase the volume? It would seem that doing that would force me to reconsider the port geometry and then we end up with fill chasing port chasing tail... However, the Voxel was designed by Paul Carmody, I would think, to showcase how small of a cabinet one can use to get this good of extension. Well now, when I model Paul's Voxel, I can see a benefit in moving to a larger volume and port geometry, but at the sacrifice of increased box volume. Well now... hmmm... why not keep it really small as Paul intended, but use fill to increase the "effective" box volume and then design the port geometry on the estimated "effective" box volume based on the guidelines that one contributor posted above?

            For once, I am going to leave a side of this box removable and play with this some!

            Thanks again all!!

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            • #7
              Re: Lining sub woofer cabinets?

              I never heard it about poly fill, but I have heard the argument that fiberglass insulation increases the "perceived" volume. The argument most used is that the FG turns some rear wave energy into heat, thus making the box seem bigger to the driver. No idea of the physics, but that is what has been floating around for as long as I can remember. Could be completely wrong though, just what I have heard over the years.

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              • #8
                Re: Lining sub woofer cabinets?

                I have also repeatedly heard the volume increase theory based on heat, and have read some spirited debates on it, but get the general feeling that if it actually does, it isn't much (less than ten percent "increase") I'd never rely on it for the purpose of "bigger box in a bag"..

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                • #9
                  Re: Lining sub woofer cabinets?

                  Originally posted by kanemack View Post
                  I never heard it about poly fill, but I have heard the argument that fiberglass insulation increases the "perceived" volume. The argument most used is that the FG turns some rear wave energy into heat, thus making the box seem bigger to the driver. No idea of the physics, but that is what has been floating around for as long as I can remember. Could be completely wrong though, just what I have heard over the years.
                  It's not completely wrong, but mostly. Stuffing works by altering impedance, which lowers Q. That can help tame a midbass peak, but it does not work the same as a larger box. If you have WinISD Pro you can see the effect on impedance, Q and response in the Box window, clicking on 'Advanced' to reveal Qa. The default is 100, which is an unlined cab. A lined cab is emulated by changing the Qa value to 50, a heavily stuffed cab by changing the value to 5. Note that it shows the effect on impedance, Q and low frequency response only. It won't show the effect on damping internal reflections. HornResp will do that with a sealed box sim, but only to the extent of showing the damping of box resonances, not harmonics.
                  www.billfitzmaurice.com
                  www.billfitzmaurice.info/forum

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                  • #10
                    Re: Lining sub woofer cabinets?

                    Fiberglass and polyfill (in their many forms) don't actually make the driver "see" a bigger box, but they CAN lower the system Q (similar to the way a larger box would). Semantics? Probably. BTW, that "Q" effect only applies to closed box systems, not vented.

                    I DO line vented boxes (w/Wal*Mart mattress-topper), but stopped lining vented subs years ago. No problem.

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                    • #11
                      Re: Lining sub woofer cabinets?

                      Gentlemen. Thanks to all of you for your comments. I find the last two comments by Chris Roemer and Billfitzmaurice to be very enlightening. I did as one advised and played with the Qa value of my modeled Voxel sub in WinISD Pro and found that altering the Q of my alignment isn't anything that I would want to do on purpose to my particular build.

                      Just for grins, here's a snapshot of the alignment that I am shooting for with my Voxel build.
                      Attached Files

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                      • #12
                        Re: Lining sub woofer cabinets?

                        Here's a test proving that Damping lower's Port Tune ?:http://www.troelsgravesen.dk/vent_tuning.htm

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                        • #13
                          Re: Lining sub woofer cabinets?

                          That article was an interesting read. Thanks for posting that Radnyc1

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