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Car Forum / Driving, Maintenance, Tuning / Car Audio / April 2004Too much polyfill??
I recently built a sealed box for three jl audio 12w6v2's with each in its own cabinet. I put polyfill in the box and it seems to not hit the lows like I like. I was wondering if the polyfill might be a problem. or it needs some time to break in or I need more space. Anyone have any comments. I just dont want to be too hasty pulling out the fill. I was always told that about a pound of fill to a cubic foot. One pound per cubic foot is in the right ballpark. How big is the enclosure volume for each sub? Polyfill will mimic the effects of a larger box, but it will only get you so much. Scott Gardner >I recently built a sealed box for three jl audio 12w6v2's with each in its >own cabinet. I put polyfill in the box and it seems to not hit the lows like >I like. I was wondering if the polyfill might be a problem. or it needs some >time to break in or I need more space. Anyone have any comments. I just dont >want to be too hasty pulling out the fill. I was always told that about a >pound of fill to a cubic foot. The chamber for each sub is around 1.1 gross cubic feet. > One pound per cubic foot is in the right ballpark. How big is the > enclosure volume for each sub? Polyfill will mimic the effects of a [quoted text clipped - 8 lines] > >want to be too hasty pulling out the fill. I was always told that about a > >pound of fill to a cubic foot. Well, you're on the small side there, so that might be part of the problem. Considering the driver displacement, you've only got about 1 cubic foot per driver, and the recommended size is 1.25 cubic feet per speakers. What's the overall impedance of your subwoofer setup, and how much power are you providing to them? Scott Gardner >The chamber for each sub is around 1.1 gross cubic feet. >> One pound per cubic foot is in the right ballpark. How big is the >> enclosure volume for each sub? Polyfill will mimic the effects of a [quoted text clipped - 12 lines] >> >want to be too hasty pulling out the fill. I was always told that about a >> >pound of fill to a cubic foot. I put them in a 1 cubic foot to try and get agood tight beat but it seams to be losing the low end which I didnt think should happen. The space req. is between .90 and 1.5 cubic feet. I have the three running at about 2.67 ohms with about 1100 good watts going to it (Rockford fosgate 1050S, 4 ohm stable bridged but does 2 ohms just fine.) > Well, you're on the small side there, so that might be part of the > problem. Considering the driver displacement, you've only got about 1 [quoted text clipped - 24 lines] > >> >want to be too hasty pulling out the fill. I was always told that about a > >> >pound of fill to a cubic foot. Yep, you're right that the allowable range goes all the way down to .9 cubic feet net per driver, I was just going off of the recommended enclosure size from the data sheet that suggests 1.25 cubic feet. You will lose some of the low-frequency extension as your box gets too small, but it's hard to say exactly how much. Have you tried modeling your speakers in one of the software programs and seeing what kind of a diffference the extra 25% volume would make? Scott Gardner >I put them in a 1 cubic foot to try and get agood tight beat but it seams to >be losing the low end which I didnt think should happen. The space req. is [quoted text clipped - 33 lines] >about a >> >> >pound of fill to a cubic foot. I plugged in the new numbers and there was not a significant change. There was a little in the lower end though. I guess I will just take out the fill and see what the change is. > Yep, you're right that the allowable range goes all the way down to .9 > cubic feet net per driver, I was just going off of the recommended [quoted text clipped - 43 lines] > >about a > >> >> >pound of fill to a cubic foot. > I plugged in the new numbers and there was not a significant change. There > was a little in the lower end though. I guess I will just take out the fill > and see what the change is. Taking out the fill is not the solution. The fill is helping to give the subs the illusion of more space. Is it possible for you to invert the subs? That will gain you the displacement and should help you decide if another 0.1 - 0.15 cuft helps the low end you are looking for. Also, what frequency are you crossing the subs at? good suggestion.... Another question for Robert? where and how are the subs installed? what kinda car/truck? FHLH > > I plugged in the new numbers and there was not a significant change. There > > was a little in the lower end though. I guess I will just take out the [quoted text clipped - 6 lines] > 0.1 - 0.15 cuft helps the low end you are looking for. Also, what frequency > are you crossing the subs at? They ate in a sealed box each in its own chamber. A little less than 1 cubic foot for each. The vehicle is a 2001 nissan pathfinder. Powered with a rockford fosgate 1050s at 2.67 ohms > good suggestion.... > Another question for Robert? [quoted text clipped - 15 lines] > frequency > > are you crossing the subs at? |
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