Hey guys, crazy idea? Is there any danger/advantage running my HPF pre-series 3 at 12v?
Maye I didnt have enough morning coffee. I thought I would ask...I dont want to fry mine (I only have two!).
Francis?
No idea, but @fdeck is the one to ask.
In other news, I recently figured out how to do some frequency sweeps with my audio interface (Focusrite Scarlett 2i4 - nothing spectacular) and the program Room EQ Wizard. I tried this with a couple of preamps and with the HPF3. So far, I am mainly looking at SPL vs. frequency, though the program measures myriad other things (like phase relationships and distortion) that I haven't really gotten into. (To be clear, I'm not measuring anything acoustically -- signal is generated from the program and looped from the interface, through the device being measured, and back into the interface.)
I learned that it's easy to make errors that can skew your results (like using inappropriate signal levels or not disengaging the direct-monitor function on the interface, which can feed-back through the device you're scoping and give you skewed results and weird resonances -- which, since you're not monitoring, you don't hear). I'll come back and elaborate (here or elsewhere) on my methodology (not that there's much to it) at some point -- the last thing I want to do is misrepresent someone's work and, if I'm making a mistake somewhere, I want to know.
Meanwhile, though, after several trial runs, checking my results, and running them by @fdeck before posting here, I think that I've got things reasonably sorted.
I measured the response of my interface beforehand and used that as a calibration file in REW.
At any rate, this is the measured response of my HPF3. The title indicates that the numeric SPL levels given are at 35 Hz (the HPF3's minimum adjustment) but they are actually at 34.9 Hz -- couldn't get the cursor exactly on 35 Hz. It was exactly -3 dB there, though, and the -3 dB at max was exactly at 140 Hz (top of the adjustment range), too. Impressive correlation (at least to me) with the nominal specs.
I ran the sweep from 2 Hz to 21 KHz (my interface tops out around 22 KHz), using the response at 1 KHz as my "0 dB" reference. I've zoomed-in on the are of interest for an HPF, but the response from 1 KHz on up is pretty much ruler flat.
I know that we've seen several visualizations of what an HPF is supposed to do, but I thought you might all be interested in an actual, measured response. (There is no smoothing applied to the graphs, btw -- this is how they came out.)
Thx!
