Inventing two 12" R's

[moparerrnocar 10+ year member]

I'm looking to get some extra vol until I can build a new box. My question is... How do R's react to being inverted? What other pros/cons are there? Also, my HU has sub phasing setting (0 or 180), is this for inverting? Any other setting I might need to change?

Also is it possible to use polyfill in a vented enclosure? If so, how do I keep it from flying out? If I staple it to the walls, will it have the same effect as being loose and fluffy? Idk how much I'd need, I heard 1 lb for every 1.5 cuft. I think my box is 2.97 after port displacment, so I'd need 2 lbs? Would more be better?

Thanks

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[subzero 5,000+ posts]

poly fill, use a wire mesh, chicken wire fencing type. Invert will give you the speaker displacment back. 180, then yes switch to 180, but listen to how it sounds bout ways. Down fall is dependant on mechanical noise exposioure

 

[TaylorFade 10+ year member]

There's no real downside to inverting subs. Well, other than having to line them up on the baffle juuuuuust right so the surround doesn't rub on the cutout. If you can, mount them traditionally first so you can use the screw holes to line it up when you flip them.

You don't need to wire them any differently. I always hear that phase switch is to "center" the sub bass in your sound stage. But I never use it. Lol. It's a useless knob on my amps.

I always read that it's 1lb/1cf for proper damping (dampening?). You can adjust the amount until you get it right. It's usually easy enough to add or take some out. As far as using it in a ported box, just put some chicken wire across the throat of the port and you shoudl be good. You don't need to staple it or anything.

 

[moparerrnocar 10+ year member]

poly fill, use a wire mesh, chicken wire fencing type. Invert will give you the speaker displacment back. 180, then yes switch to 180, but listen to how it sounds bout ways. Down fall is dependant on mechanical noise exposioure

Wow thanks for the quick reply... I like the chicken wire idea. How far should I keep it from the port? Its a center slot port thats 3.75 from the back wall. Should I line the entire back? Or should I leave 3" from the port and not pad the port wall all? Any idea how much vol 2 lbs will add?... I've messed w/ the phasing b4 w/ them mounted normally but didn't notice a difference. What do you mean by "dependant on mechanical noise exposioure"?

 

[moparerrnocar 10+ year member]

There's no real downside to inverting subs. Well, other than having to line them up on the baffle juuuuuust right so the surround doesn't rub on the cutout. If you can, mount them traditionally first so you can use the screw holes to line it up when you flip them.
You don't need to wire them any differently. I always hear that phase switch is to "center" the sub bass in your sound stage. But I never use it. Lol. It's a useless knob on my amps.

I always read that it's 1lb/1cf for proper damping (dampening?). You can adjust the amount until you get it right. It's usually easy enough to add or take some out. As far as using it in a ported box, just put some chicken wire across the throat of the port and you shoudl be good. You don't need to staple it or anything.

I must have just missed your post. I see now, you just use the chicken wire as a grille/screen. At first I thought subzero meant to "matt" it down. Duh that makes sence cuz then its still fluffy.

Thanks

 

[subzero 5,000+ posts]

1lb for every 1/2 cub gain.

 

[Chad1]

Sorry bud, they've already been invented

 

[moparerrnocar 10+ year member]

So 2-2.5 lbs would be good, does the box's tune matter? Idk how to figure that out and maybe it doesn't even matter. Like I said its a center slot. It measures 3x11.5x12.25 (or 4.5x11.5x12.25 O.D.) and If you or anyone else has the formula I'd be glad to "try" and figure it out if you dont feal like crunchn' numbers. Also the box measures 36x13x16. Btw what did you mean by dependant on mechanical noise exposioure. Do you meen they'll sound like crap?

 

[moparerrnocar 10+ year member]

Sorry bud, they've already been invented

Aggh, typo... I bet I cant change it lol... Good catch //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[moparerrnocar 10+ year member]

Nope, oh well

 

[TaylorFade 10+ year member]

So 2-2.5 lbs would be good, does the box's tune matter? Idk how to figure that out and maybe it doesn't even matter. Like I said its a center slot. It measures 3x11.5x12.25 (or 4.5x11.5x12.25 O.D.) and If you or anyone else has the formula I'd be glad to "try" and figure it out if you dont feal like crunchn' numbers. Also the box measures 36x13x16. Btw what did you mean by dependant on mechanical noise exposioure. Do you meen they'll sound like crap?

Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators

 

[moparerrnocar 10+ year member]

Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators

Cool, all kinds of calculators. I got 40hz w/ my subs mounted normally, but Idk if the box vol they wanted was w/ or w/o port displacement. I'm guessing its w/o.

So w/ them inverted that would gain .2 ft^3 for total of 3.5, and if Subzero is correct, then 2 lbs should net me 4.5 ft^3 for a final tune of 35hz correct?

Do you got a link for the actual formula? I trust the calculator, but I'd like to know incase I cant get to the calc.

Thanks, I sure appreciate the help guys.

 

[TaylorFade 10+ year member]

I've never actually seen a formula for how much volume you net by using polyfill. If @subzero is correct, that's friggin awesome.

 

[Dirtrider4eva 10+ year member]

I've wondered about this.. Does poly fill effectively work with ported boxes? Say I put 4 lbs in a 6 cube box, would it react similarly to a 8 cube box?

 

[keep_hope_alive Premium Member]

in the Loudspeaker Design Cookbook, Vance Dickason compares various fill materials. Polyfill scores the lowest. it's cheap and doesn't itch, which is why it is used. but it's absorptive qualities are poor. fiberglass is king, but working with fiberglass is a PITA. Refer to LDC 7th Edition Table 1.21.

recycled denim acoustical batt is an excellent alternative.

UltraTouch Acoustical*– Thermal Insulation for Walls & Ceilings*– Green Product

you want to review tested/published sound absorption (ASTM tested)

From the LDC:

"Traditional enclosure damping, to suppress standing waves in a vented-box system, consists of lining one of each opposite side with 1"-2" of fiberglass. It is recommended, however, that you cover all surfaces directly behind, and adjacent to, the woofer. Colloms recommends that such damping material be placed within the volume or open area, not on the box walls.

The effects of damping can be observed by computer simulation. Using the same 12" woofer and QB3 enclosure from Section 2.50 simulation, three enclosures were built with 0%, 10%, and 50% fill of standard R19 fiberglass. The 10% was made by lining one of each opposite sides with 1" fiberglass. The 50% sample would be equivalent to lining all four sides and the rear wall with 3" thick material. The computer-generated graphs shown in Figs. 2.58-2.60 show the results. The SPL curves in Fig 2.58 show minor response changes, while the damping changes seen in the group delay in Fig 2.59 are also slight. The impedance curves in Fig. 2.60 likewise indicate only minor changes. This being the case, the primary benefit would be from decreased response changes due to box standing wave modes, making the 50% fill an attractive choice. Be sure you do not obstruct the vent with fill."

the "minor" changes are a shift lower in frequency.