Multiple narrow notch filters

[Ken G]

I have been having a big problem in a particular venue with a strong magnetic hum field. It makes ribbon microphones completely unusable, and even capacitor microphones with electronically balanced head-amplifiers (i.e. no transformers) deliver enough hum to need attention. The same setup is quite clean elsewhere, and practical positions of the mike and cable make little or no difference, although turning the mike on its side, an unusable position, gets rid of it. The hum by the way is not a buzz from say a lighting fader, but 60 Hz with traces of odd multiples.

Adobe Audition is the only program I have found so far that provides multiple very narrow notch filters which allow me to remove the hum without audible impairment of the music (a small chorus), but frankly I am reluctant to spend $200+ just for the sake of the filters. Other editing programs have various equalization options, but not narrow notches.

Has anyone any suggestions?

Ken G

[Ed Belknap]

Believe it or not, the Behringer Feedback Eliminators (DSP1100 or 1124, I forget the exact model #) can be configured as a stereo 12-band parametric equalizer with bandwidth adjustable down to 1/12th octave. That is one seriously narrow notch! Last I heard one I was underwhelmed by the quality of the A/D converters, so it wouldn't be my first choice, but it'll do what you're looking for for less than $150.

AudioArts used to make an all analog 5-band sweepable notch filter that had some pretty tight notches, you can probably find them on ebay.

[Ken G]

Ed,

Many thanks. I was hoping however that someone would know of a shareware or freeware program that would process my existing wave files (no need for real time). Things like 1/12 octave filters don't cut it; if you make them introduce 20 dB or more attenuation at the desired frequencies, they produce enough loss at intermediate frequencies to give an audible loss of bass. The Adobe Audition filters work very satisfactorily, but my free trial installation will expire before the actual concert recording!

Ken G

[David Klausner]

The Waves Q10 is a 10 band "paragraphic" EQ where the filters can get extremely narrow. They even have a hum removal preset on it that notches 60 cycles and the major harmonics. Unfortunately, it is only available as part of the Native Power Pack, Gold, Platinum, and Diamond Bundles, so while it's pretty inexpensive in context, a bundle may be more than you are looking to spend. A less expensive single choice might be BIAS Soundsoap, which is a broadband noise reduction software.

[Ed Belknap]

Originally posted by Ed Belknap
Believe it or not, the Behringer Feedback Eliminators (DSP1100 or 1124, I forget the exact model #) can be configured as a stereo 12-band parametric equalizer with bandwidth adjustable down to 1/12th octave.

Actually, I forgot about the "fine" mode on the Behringer DSP1100P; engaging that changes the bandwidth of the parametric filters to 1/60th of an octave.

I trust you wouldn't find 1/60th octave cut (at *any* frequency) to result in a "loss of bass"

It's not freeware, but they're pratically being given away. I know, 'cuz I just gave mine away!