Originally Posted by cannga
Questions for the subwoofer experts here; In a subwoofer that is designed from the start to be either ported or sealed such as the gorgeous
new SVS PB16, does plugging all 3 ports make it measure/sound/behave, etc., more or less identical or very close to its sealed counterpart SVS SB16?
If so for those who would like to experiment and/or could not be sure how a subwoofer would behave once it's actually in the room
, the PB 16 would seem to be a much better choice? Price and size notwithstanding. TIA
You asked for the subwoofer experts to chime in and they have given a tutorial of subwoofer theory and operation, and that may be exactly what you were looking for. From a layman's perspective, the answer is Yes a ported SVS sub (PB16) operating in sealed mode will perform very close to its sealed counterpart (SB16).
We don't have data on the 16 Ultra line yet but we do have data on the 13 Ultra line, and the comparison will be very similar.
(from data-base.com) is the max output of the PB13 operating in sealed mode verses the SB13, as we can see the outputs are similar, with the sealed PB13 having more output from 20hz to 50hz mostly due to the bigger box size of the PB13.
Next if we look at the 10hz-200hz frequency response of the PB13 in sealed mode vs the SB13 they are also very similar in nature and only really vary in output (see attachment #2
also from data-base.com).
Now for some on these forums, if anyone would sacrifice a single db of output on a subwoofer for any reason, this is a crime punishable my death or a life of shame and ridicule....but by using a sealed configuration it does reduce group delay and improve time domain behavior.
Below is a excerpt from Ed Mullen (Director - Technology and Customer Service
of SVS) regarding this topic in 2013 from Sound and Vision:
If we look at a sub like the SB13-Ultra, the phase response is quite benign, the roll-off slope is shallower, and there’s less phase rotation below the –3 dB point so there’s less group delay. Subjectively you get that stop-on-a-dime bass that enthusiasts describe as faster or tighter. We specifically designed the SB13-Ultra to have optimum group delay and time domain behavior. That doesn’t mean our bass-reflex subs are bad for music, because we do everything we can to maximize frequency response and bandwidth linearity [equality of maximum output at all frequencies], and to shift the phase rotation below the music bandwidth. With that said, if you plot the group delay and look at time domain behavior, you will see distinct ringing near the port tuning as compared to the sealed box."
See attachment # 3 (from data-bass.com) plotting the group delay of the PB13 in open port mode and sealed mode. As we see, the group delay for the PB13 in sealed mode is very similar to the SB13.
Once we do seal the PB13/PB16 and change the DSP setting, there will still be some differences in operation when compared to the SB13/SB16 because the drive topologies are different. The PB13/PB16 use a underhung driver while the SB13/SB16 use a overhung driver, which may exhibit different cone excursion and linearity at max output between the two configurations.
An overview is here at Audioholics.com http://www.audioholics.com/subwoofer-reviews/svs-pb16-ulta-and-sb16-ultra-subwoofer
and illustrated at https://en.wikipedia.org/wiki/File:V...l_geometry.svg
So at the end of the day if someone wanted "to experiment and/or one was not sure how a subwoofer would behave once it's actually in their room" and didn't want to order both versions (PB16/SB16) - Yes they could order the PB16 and configure it open mode and sealed mode (which is very similar to the SB16) - and then compare which is better for them in their room with their equipment, with their material and for their taste. And if they are not using room correction sw, they could readily switch back and forth between sealed and open port mode freely whenever they wanted to.
Because as shown, when you plug the ports and change the DSP settings, the sealed PB models test and sound very similar to the SB models.
Now regarding the nuances of overhung vs underhung, gap height vs coil height, operating in ported vs sealed boxes - we now return back to the experts