True, but I have also noticed the dayton Reference HF drivers like a vented enclosure too. For example, WINISD modeling shows the HF drivers as being more flat with a steep roll-off down low. But, I do agree that the HF will offer more accuracy and less distortion in a sealed enclosure. Appreciate your input though.
The HF drivers do very well in sealed or ported applications. The Quattro on the other hand does not appear to do well in lower tuned ported enclosures. If memory serves me correct it does not tune well much below 30hz-35hz. In my opinion a 15" woofer should be able to play well down into the 20hz range or lower.
Any woofer that is ported will have a steep roll off as they (ported enclosures) naturally rolloff at 24db/oct. below the tuning frequency. Some woofers, specifically those that are really not ported enclosure woofers, can start rolling off well before the tuning frequency of the enclosure. Then, at the tuning frequency, begin falling away at 24db/oct. compounding the effect.
Sealed woofers naturally roll off at 12db. per octave below the Fs of the sub system (woofer and enclosure, not the sub's Fs). However, in sealed systems the Fs tends to occur at much higher frequencies than where a ported enclosure can be tuned. Even the best sealed subwoofers usually have a FS (when sealed) in the low to mid 40hz range. Room gain effects and parametric Eq's are the saving grace for sealed systems as far as extened low frequency response is concerned. That, and they can be a just a slight bit better in transient response. Well executed ported systems and passive radiator systems can be nearly on par with a sealed system in this respect.
I hope that helps a bit in terms of enclosure choice.
Personally I was a sealed guy for years until I really started playing around with low tuned vented enclosures. I found you can get nearly the same type of transient performance (of sealed) with even more extended low frequency response. Not to mention you need significantly less amplifier.
The only time I will probably consider a sealed system now is if I have a woofer that has significant linear excursion and a high power compression threshold to allow for a parametric eq. A la the JL Audio W7 and W6v2 along with a few others. As I have one(W7), I will be playing around with that avenue in the future.
I really like the idea of well done passive radiator systems as well.
