Woofing "Q"

If the Q of your sub is a lot higher than your speakers then you will lose detail in the bass and lower mids and the sound will not be as clean and tight.

Sealed subs are really the only way to go if you seek quality rather than an HT sound - but the investment in a sealed sub could be wasted if your speakers are designed with high Q (most speakers with impressive bass extension and small woofers with a port are tuned to a high Q)

Can you adjust the damping of a box,either sub or sat, acousticaly, by putting a 'brick' in the box or a 'sock' on the port? Thanks all for your patient answers

"And may powdered sugar fall gently upon your ears"

Can you adjust the damping of a box,either sub or sat, acoustically by putting a 'brick' in the box or a 'sock' on the port?

You can but it may change the freq response in an undesirable way even if it improves the transient response (group delay)...some subs like the PBUltra13 can have the ports plugged. It is certainly an option but there is a rule of thumb for whether a woofer works best in a ported design or a sealed box...

Shadorne's comment re: "sealed subs only" is probably, as a practical matter, good advice for a music only system, but it may be a bit of an overstatement. The SVS subs he mentions shouldn't be dismissed. Their top model, in it's fully ported configuration, outperforms most sealed boxes on group delay tests. This test usually favors sealed, highly damped designs - but the SVS Ultra shows awfully well. Also, like all ported subs, it offers more deep, clean output capability than a typical sealed box design of similar size and amp power.

That latter item may not be critical for most music (how much musical program material has deep bass info <30hz, anyway?), but it begs a question:

How do you intend to install the subs?

If you're going to roll off the bass to your mains and cross at or above 60ish hz, I'd say sealed boxes are safer bets. If you're gonna run the main speakers full range and "snug up" a sub below their natural roll-off, then it becomes a more open question. Many users on this forum run their subs in this fashion, often rolling off their sub's upper response somewhere below 50hz. In this configuration, a ported box (particularly a good one like the SVS seems to be) may make more sense.

Good Luck

Marty

Shadorne's comment re: "sealed subs only" is probably, as a practical matter, good advice for a music only system, but it may be a bit of an overstatement.

Marty,
Who me ...make an overstatement...never !
LOL - Marty is right - my context is uncompromising bass response. I am not sure where the OP sits, and admittedly for many people "more bass" is better and a low Q device or a sealed sub may sound unimpressively bass light for their taste and $$$ invested.