Originally Posted By: bridgman
Speaking of port plugs... any idea how they impact the frequency response, ie whether they just reduce port output or whether they shift the enclosure tuning as well ?

Reason I'm asking is that when I look at the FR charts for speakers with the HP woofers they seem just a bit peaked-up in the 50-100 hz range which usually ends up bothering me, however...

(a) I remember there being some discussion about the anechoic chamber readings needing adjustment below a certain freq (80 Hz ?) due to finite size so maybe there is some room reinforcement already present, and

(b) if the port plugs have the same effect as they do on SVS subs (they seem to lower the port tuning, so bass drops off a bit sooner but extends lower) a bit of port plugging would probably make the FR ideal for me. The legend on this chart has 4 entries and only 3 lines (with no colours), but I'm pretty sure green is all 3 ports open and purple is one port plugged.



Obviously I'm hoping someone got bored one rainy day in Dwight and ran a set of tests on an M*HP with and without port plugs.


Check out http://www.data-bass.com/systems


More specifically look at the SVS PB13 Ultra. If you click on the different modes (15 Hz, 20 Hz and sealed) you can see how many things change. For example, the long term output compression, waterfall plots and distortion measurements vary quite a bit from one mode to another. The same ideas will be true if you have the SVS PB12+. Just it will have a bit less extension and a bit less maximum output before compression sets in and distortion begins to rise, in comparison to its bigger brother.