by Jonathan » Sun Jan 01, 2006 10:05 pm
But basically with fill, you're converting the enclosure from Adiabatic to Isothermal. The fill just converts more energy into the form of heat and makes the enclosure more lossy (better damped), so in effect the air pushes less on the speaker. I think the bigger difference you'd notice is the flattening of the impedance peak, which won't be a humongous difference, but it's audible.
The main reason I'm not a fan of sealed enclosures from a SQ stance is because it's pretty much impossible to fully dampen the resonance of the enclosure. You can fill, foam, deaden a sealed enclosure all you want and it can still be outdone by a well designed ported enclosure, much less an AP or Transmission line. IB tends to have such a low resonance that it isn't a big issue. With sealed, nearly any application of a typical 10" or 12" sub in a car is going to have the resonant frequency at least above 40hz, but usually in the 50s and 60s, right in the meat of the bass range. It's also the point where the sub has the least control and the highest distortion. There is the argument that you can equalize it, but I think we all know that you can't really rid the audibility of a resonance. I think this is a lot of the reason that SQ competitors are doing more and more IB applications in vehicles, with some doing AP, but it's hard to hit cap with an AP membrane and your average SQ subwoofer.
But basically with fill, you're converting the enclosure from Adiabatic to Isothermal. The fill just converts more energy into the form of heat and makes the enclosure more lossy (better damped), so in effect the air pushes less on the speaker. I think the bigger difference you'd notice is the flattening of the impedance peak, which won't be a humongous difference, but it's audible.
The main reason I'm not a fan of sealed enclosures from a SQ stance is because it's pretty much impossible to fully dampen the resonance of the enclosure. You can fill, foam, deaden a sealed enclosure all you want and it can still be outdone by a well designed ported enclosure, much less an AP or Transmission line. IB tends to have such a low resonance that it isn't a big issue. With sealed, nearly any application of a typical 10" or 12" sub in a car is going to have the resonant frequency at least above 40hz, but usually in the 50s and 60s, right in the meat of the bass range. It's also the point where the sub has the least control and the highest distortion. There is the argument that you can equalize it, but I think we all know that you can't really rid the audibility of a resonance. I think this is a lot of the reason that SQ competitors are doing more and more IB applications in vehicles, with some doing AP, but it's hard to hit cap with an AP membrane and your average SQ subwoofer.