SVS Sub-Sonic filter setting question

[stevefish69]

Finally had an afternoon to play so thought i'd post some results on here.

When you have a look at the attached file, this will all make sense. The 12.3 driver had definantly loosened up a bit after running in, and this managed to help me make a few cuts in the BFD from my previous settings.

I plotted the 20Hz tune, and got the best line that i could get. My room plays games >80Hz but i think this will soon be sorted with new fronts.

I then played with the 16Hz tune, and as expected the overall SPL was lower but there was a massive increase from 22Hz down to 16Hz. This setting only needed 2 filters to be used though.

I then thought i'd be a bit silly just to see what would happen. I removed the port bung BUT LEFT the Sub-Sonic filter set to 16Hz. The results are now the best i've ever had, and appear to be rulker flat from 16Hz to 56Hz.


QUESTION ????

Will leaving the ports open but the filter set to 16Hz Shag my sub ????
Obviously the manufacturers recommend that the port tuning and filter are set the same, but i'm sure i've seen users not matching the port and filter tuning before. Surely those few extra Hz leaking though can't hurt THAT MUCH

Thanks for any help in advance. Off to watch Nemo now, so will post back if my sub ends up in a puff of smoke

Steve

[SteveCallas]

Ilkka's charted the different EQ profiles of the 20, 16, and 12hz settings, and I'd have to imagine the center frequency of the highpass gets changed as well, maybe 18, 14, and 10hz (guesses). By keeping all three ports open, the enclosure is still physically tuned to 20hz, yet with the 16hz filter setting, a boost is being applied down low and the highpass is lowered to maybe 14hz, putting you at risk for potential bottoming with high output, low frequency material. If you don't play your media very loud, you'll be ok, it's not like you're hurting the driver, but you'll be losing some protection in the event that a demanding low frequency scene does come up. You have to assume they created the filter profiles for the tunes they did for a reason

What model do you have and how loud do you typically listen at?

[stevefish69]

Hi ya,

Thanks for the reply

I have the 20-39PC+ with the new 12.3 driver recently installed.

I would not say that i listen at extreme levels. Normally -15db, but i do run the sub a few db's hot. I have managed to bottom out the old 12.1 driver on WOTW and FOTP but this was at -10db

I've just picked up some Kef Ref 3.2's today, so need to do a complete system re-tune anyway. God knows how long thats gonna take me.

[SteveCallas]

If you've had some previous occurences of getting the sub to bottom, I wouldn't leave it in this current configuration. I'd stick to the 20hz tune with 20hz filter.....or buy a second sub

[Geoff Gunnell]

Stevefish, I agree with SteveCallas that you are increasing the risk of bottoming on demanding LF material. If you are the kind of chap who never goes near his sub once he gets it set, match your filter and enclosure tune settings.

If, however, you are like me, changing your sub(s) settings depending on what you are playing, at least for non-1812 Overture music you have found the best EQ in your room -- use it. Just remember to flip the switch before WOTW etc.

[Tom Vodhanel]

Hi Steve,

"shag" your sub...that is a new one..

The problem with mismatching the port configuration and the amplifier setting is the potential for extremely large cone movement. With a ported subwoofer, the woofer "unloads" with frequencies under the "tuning point" of the enclosure. This means the cone loses back resistance (from the enclosure) and can easily move further than it was designed to do. So an electronic subsonic(highpass) filter is usually applied near the "tuning point" of the enclosure so attenuate frequencies under this(tuning point) to protect the driver(this is the control on the amplifier marked 12hz, 16hz, 20hz, 25hz). If you set the amplifier control HIGHER than normal...it isn't a problem for the subwoofer because you are simply filtering the deepest bass a little before the "tuning point" of the subwoofer enclosure. For example, if you had all ports open and set the filter to 25hz. BUT, the opposite can lead to trouble. With all ports open the driver will begin "unloading" <20hz. That in itself presents a risk. But with the amplifier set to 16hz...instead of electrically attenuating the signal(<20hz)...you are actually applying a BOOST to that signal.

I guess you can think of the subsonic filter settings on our subwoofers as a "rev limiter" on a race car.. And with all ports open and the amp set to 16hz...instead of the rev limiter capping the engine revolutions at say 6000 RPM...when you hit 6000...the rev limiter automatically increases the engine revs to 6500. Yes, the "engine"(subwoofer driver) can handle this most of the time...but it only takes once to end up with some "metal on metal" noises(in the engine and subwoofer driver).

Tom V.
SVS

[stevefish69]

Thanks a million people

The little dial is set back at 20Hz and will stay there

I can feel an Ultra upgrade on the way though

[suniil]

glad to read this now! just finished calibration and left as steve's one.