Topic: High Pass Filters on the SD 702

[piperedworm]

Hello my friends!  I have been wondering about this topic for some time now.  What exactly does the High Pass Filters on my 702 do.  In the manual it states that the first set of filters are Analog and the rest are digital.  Will using the 40hz 6db/12db filter get rid of some of that deep bass in my recordings?

If anyone has any idea or have used these setting let me know.  I am getting ready to run the "Pepsi Challenge" in my kitchen tonight.

Sorry if this is a dumb question.

Jeff

[page]

It will; the lightest setting you can run though is 40hz/12db. As of the 2.65 firmware, there is always a digital stage active whenever the analog is.

What it will eliminate is the deep room reverb or sub-bass (for better or worse). Sometimes thats good, sometimes it isn't. I've tried the 12db, and whatever the strongest one was, and I'd consider running the 12db again in special situations, but I wouldn't run anything stronger then that. At that point I'd roll it off in post if that was the problem.

[piperedworm]

Thank you my friend!  Anyone else used these settings or have any other advice.  All comments are welcome and appriciated.

Jeff

[ghellquist]

I suggest rolling off in post production. If not captured, nothing to do. If captured you can always test various settings and types of filters til satisfied.

Every sound modifying program has some kind of filter in it. Many can run plugins allowing you an almost endless selection of algorithms. One example of a free program is Audacity.

I do run a 722 for mostly classical recordings. Conservatie levels, single blinks on yellow LED-s. Limiter on to catch when I really botch things. Raise levels in post, and roll off lows.

// Gunnar

[piperedworm]

Thanks.  I have been using Audacity to push the Gain up post production by about 6db.  Ends up sounding nice but with that Bass in the Background.  I notice that the SD does not like it when you push it in the Red.  One Red light seems to be ok.

What setting would you recommend in Audacity to get rid of that Bass?

[DSatz]

40 Hz is a very, very low audio frequency, and a filter set to that frequency won't affect much musical material because there is hardly any musical material down there to begin with. Also, pressure gradient microphones (any kind of directional microphone) have considerably reduced acoustical pickup at or below that frequency, but they have considerably increased sensitivity to wind, breath noise (for close-miked vocals or speech pickup) and mechanical vibration/shock noise, so that by the time you're down around 30-40 Hz, the majority of the signal energy coming out from them is garbage.

Pressure transducers (which are omnidirectional) are a different kettle of fish, but live music (especially pop/rock/jazz) doesn't often go that low, and field recorders such as the SDs are most often driven by directional microphones. So the main purpose of a 40-Hz filter on a recorder like that is for safety--to keep low-frequency noise from overwhelming a recording.

It's not a tone control in most cases; it's too low for that purpose, and it's the wrong shape; it's a filter, whereas most tone controls that are designed to improve musical balance have a "shelving" response. In other words there is a region which they don't affect, and a region which they affect by the amount you've dialed in, and of course a transition region in between--but they don't continue cutting or boosting further once you reach the frequency at which they take their full effect.

So don't use filters as tone controls; they generally won't do the job you intend. Use filters as filters, and tone controls as tone controls, is my suggestion.

--best regards