I have been giving a lot of thought to the port chuffing issue over the past few months, and since the subject has come up again, I hope that no one will mind me sharing my perspective on the issue. I certainly don't claim that this is the last word on the subject, but it does represent some preliminary conclusions of my own. Let's start with the proposition that any ported sub can chuff under the right conditions. As Bscool noted, those conditions could include the extent to which a limiter has been employed. And, let's also agree that every sub represents a potential compromise in cabinet size and overall cost, versus performance.
Given the above, why do some subs of the same make chuff under some conditions, and not under others? FWIW, I believe that the room is a major factor with respect to port chuffing. There is the obvious issue of how distant the sub is from the listening position. The further away the sub is, the more output will be required to produce the same amount of SPL at the MLP. But, beyond that, there are some specific aspects of the room itself (and of our attempt to achieve a good FR in the room) which could affect port chuffing.
First, there is boundary gain. For instance, a corner-loaded sub would be much less likely to chuff than a wall-loaded sub, due to the additional boundary reinforcement which would add SPL. And, the type of wall construction could also be a factor with drywall providing less sound reinforcement than concrete or brick.
Second, I believe that room modes could be a significant factor in port chuffing. If someone had a room mode at or near a port tune, that could certainly reduce the possibility of port chuffing at, or near, that frequency. And, the reverse would also be true. If someone had cancellation, or even a large dip at a particular frequency, that might make a sub more susceptible to chuffing prematurely.
Third, I think that automated room EQ is a wild card in the equation. The goal of room EQ is to make all frequencies play relatively flat, irrespective of room modes which create peaks and valleys. I believe that the various types of room EQ which address very low frequencies also limit the amount of boost that can be applied to a dip or to a null. Audyssey, for instance, is limited to providing 9db of boost, although it can attenuate a peak by up to 24db. That 9db limit is implemented because the Audyssey algorithm isn't sophisticated enough to differentiate between a null and a dip, and will simply try to apply boost up to its limits to either one. But, a null won't be affected by boost, so the effort will be fruitless and will consume headroom, potentially causing a ported sub to chuff prematurely.
This isn't an indictment of automated room EQ. It typically helps much more than it hurts, especially with bass frequencies. But, that help may have an impact on a sub's propensity to chuff. I think that people who have ported subs, and who are really concerned about the possibility of chuffing, need to be particularly aware of the value of having multiple subs, with similar capabilities.
For instance, the value of having multiples lies not just in the 6db of headroom that we typically get in very low frequencies when we go from one sub to two. The value also lies in the fact that adding a second (strategically located) sub may help to reduce or eliminate cancellation (nulls) or dips, that would otherwise reduce a ported sub's ability to play strongly near its port tune without chuffing, or without making other audible sounds of distress. And, that's something that even room EQ alone may not be able to do.
Finally, although I think that while ported sub owners need to be somewhat mindful of port chuffing, as a trade-off for additional low frequency output, it isn't something that most of us need to be concerned about. As others have previously noted, that's partly because in normal operation other sounds are likely to obscure any mild chuffing noises to begin with. As a general rule, unless port chuffing is extremely overt, we aren't likely to notice it except for something like the stand-alone (and totally irrelevant) 10Hz sine wave at the beginning to Edge of Tomorrow
. At least we aren't likely to unless we are standing right over the sub, instead of listening at our MLP.
My own preference would be to trust the many anecdotal experiences of other sub owners, like those who have spoken up on this thread, and not worry too much about port chuffing. If, in a specific instance, a particular sub is chuffing more than it should be, and if the chuffing becomes overt and annoying, there may be something wrong with that specific sub. Or, the owner may not have the sub in an optimal location. Or, he may simply be exceeding that single sub's capacity, and it's time for a larger sub, or for a companion sub, or both.
I think that in a large room, and particularly on a concrete floor, ported subs can be the best thing since sliced bread. They can give us a way to have all the <20Hz content we are ever likely to want, without having to have as many individual units as we would if we tried to achieve the same objectives with sealed subs. In the greater scheme of things, the remote possibility of port chuffing is small potatoes, in my opinion.
This is not, incidentally, intended to take away anything from anyone's preference for sealed subs. There are also good reasons for preferring sealed subs. And, anyone who really likes subs will probably be as interested as I am to hear about what the new S7201 will do, either as a single sub, or ideally in pairs. But, I did think that it might be worthwhile to share some personal reflections on the issue of port chuffing for those of us who do end up using ported subs. In the vast majority of rooms and situations, port chuffing just isn't a very big deal.