Topic: 722 HPF frequency selection question

[tim in jersey]

OK, page 15 of the manual reads:

The first pole of the high-pass circuit is an analog filter at 40 Hz, 6dB, per octave and is part of the microphone preamplifier circuit.  Additional poles of high-pass filtering are done in DSP

I'm looking at the menu where you select the HPF frequency and all I see is 40Hz, 12dB/octave, the first of several that are done in DSP. How do I select the 40 Hz/6dB that is done in the analog filter? I have a suspicion it's something really obvious and simple that I am overlooking,  but for some reason I can't figure it out. Any ideas?

[tim in jersey]

posted this question on the SD support site. I will report back when I hear something.

[tim in jersey]

FYI, here's what I asked on the SD forum:

I'm looking at the menu where you select the HPF frequency and I'm given the choice of 40, 80, 160, and 240Hz @ 12,18,or 24 dB/octave, all of which are done in DSP. 12+ dB is a little too steep of a slope for my purposes, and if I need to subtract 12+ dB/octave I'd probably do it in post-prod anyway and tweak it to just exactly what the recording demands.

How do I select the 40 Hz/6dB that is done in the analog stage? I have a suspicion it's something really obvious and simple that I am overlooking, but for some reason I can't figure it out. Help please! Thanks in advance.

-tim

and here's the reponse:

Tim-

That selection isn't currently included. We can add it to our request list.

Regards,
Matt

[Brian]

didn't nick gregory use this HPF?  if you can't select it from a menu how did nick do it?

nick?

[nickgregory]

didn't nick gregory use this HPF? if you can't select it from a menu how did nick do it?

nick?

I selected the lowest HPF available....did it in the field so never went back to verify that what I chose matched the book...knew it was the lowest on the unit and assumed it would align with the lowest in the manual...apparently not, unless the earlier revisions of the FW (I was running 1.15 on that unit) had it and the current units do not...have to verify

[tim in jersey]

I'm running FW v1.37 and the lowest setting available is 40Hz @ 12dB/octave. From what SD says anything >6dB/octave is done in DSP. The 6dB/oct cut in the analog stage is inactive until one of the other frequency slopes is selected. There is no way to have just the analog filter alone be active at the moment. I have asked them to add this as a feature request.

[Brian]

I'm running FW v1.37 and the lowest setting available is 40Hz @ 12dB/octave. From what SD says anything >6dB/octave is done in DSP. The 6dB/oct cut in the analog stage is inactive until one of the other frequency slopes is selected. There is no way to have just the analog filter alone be active at the moment. I have asked them to add this as a feature request.

and i sincerely hope they implement it!  +T for following through with this and updating us here.  you rawk!

[BobW]

I'm running FW v1.37 and the lowest setting available is 40Hz @ 12dB/octave. From what SD says anything >6dB/octave is done in DSP. The 6dB/oct cut in the analog stage is inactive until one of the other frequency slopes is selected. There is no way to have just the analog filter alone be active at the moment. I have asked them to add this as a feature request.

So, you're down 12db @ 20Hz, what's wrong with that ?
You cannot hear it, only the harmonics.
Reproduction of 20Hz takes more than you think, then more than that.
Reproduction of the nasty harmonics of 20Hz is all too easy and that's potentially what you'll hear.
Pure 20Hz is really air and cone excusion anyhow.

Try this:
Rip your favorite Steeley Dan song with great tight bass that sounds good on any box you play it on.
Then look at a spectral plot of it in SF, WL, AA or whatever.
.....surprize !       

Cheers and did I +T you on the SD already ? 
Congrats !