30Hz or 50 Hz High Pass Filter

[MrHotMark]

I use QSC RMX2450 amps (and swear by them). They have a Low frequency cutoff filter choice of either 30 Hz or 50 Hz of which I usually set to 50 Hz. When playing LIVE, or when DJing, just exactly how much MUSICAL information is missing by setting the filter to 50 Hz? i.e. if you use a larger sub box that REALLY goes down to 30 Hz (read 18" sub in a 10+ cu ft box) is that merely a waste of energy? I am redoing my setup yet again.

[toxrtp]

IMO, use the 50 Hz setting. There is precious little info between 30 and 50 Hz, unless you're using something like a Subharmonic Synthesizor, such as AudioControl and DBX used to make. Pianos, virtually all synths, etc. simply do not put out usable dB to be reproduced at those frequencies. Even most P.A. subs don't go that low. Many speaker-rated frequency response stats are at -10dB, as compared to stereo-hifi specs which are at -3 dB. So, even if your amp was putting out those frequencies, I doubt your subs (even 18" subs) would be reproducing much of anything at 30 Hz. In my experience, while subs do go lower than 15" and, certainly, 12" woofers, what they do even more effectively is give you the ability to plays those very same frequencies at higher volume without breaking up the speakers. There is, as I say, a bit of low-end extension, but not to 30Hz unless you specfically design your sound/mix to provide such low-end info.

[tlbonehead]

Depends on your sub cabs,IMO. I set mine at 30 on my PLX's. But I have large e-horn 18" subs which are probably a bit more immune to "box unloading" since the inner box is actually enclosed.

[agedhorse]

30Hz is fine for larger subs that have substantial response down there (say even 7-8dB down around 30), but you would probably have good performance on most smaller subs w/ the 50Hz filter.

[dboomer]

I think 50 Hz is more appropriate for a live system ... save 30 for the recording studio. Remember, that number is a corner frequency not a brick wall. It does not stop anything below it, it just begins to attenuate there. The difference translates to more than double the speaker protection from over excursion.

[RickJ]

 

Originally posted by dboomer The difference translates to more than double the speaker protection from over excursion.

 

... and prevents wasting precious amplifier power on frequencies that will never be heard.

[tlbonehead]

I've used the 50hz cuts on my PLX amps and there was definitely a difference. There was a noticeable absence of the lowest frequencies. Personally,I think 40 hz would be a perfect frequency to roll off sharply at. I like the 30hz setting better. Of course,if I didn't have quite enough power or speakers,50hz would be a better tradeoff than taxing the components. But I like to have some reserve on hand so I don't have to do so. I do cheat a bit for outdoor shows when I need to.