[Wayne A. Pflughaupt]

Hey brucek,

But would the crossover in your receiver not produce exactly what you are describing? As the frequency advances from low to high, the crossover drops the subwoofer output level......

Well, slap me silly. Somehow that managed to get past me.

Crossover bypassed, all is well with the test tones now.

However, we still have the issue of how the meter responds with filters applied. Using pink noise I set three filters, 1/6-octave at 25 Hz, 1/3-octave at 50 Hz, 1/6-octave at 100 Hz, all boosted +16 dB. The meter registered minimal movement, from –10 to –6 dB. With all filters set to maximum cut, there was virtually no meter change.

I’m still trying to get the hang of the REW program, but using Sonnie’s sine waves got better results from the meter. Using a 1/6-octave 40 Hz filter @ +16 dB, the 40 Hz sine wave jumped the meter from –10 to –3 dB. It should have pushed it to clipping. Oh well, at least it registered something...

Also it occurs to me: The BFD equalizes in the digital domain, and knowing what little bit I do about how digital circuitry works, once the signal is digitized you can to anything to it void of analog-world constraints. As such, the signal can be manipulated without concerns of things like headroom. That only becomes an issue once the signal is converted back to analog. Right? Wrong? Enlighten me, o digital guru!

I feel to set up levels for actual use, it's best to use DVD's as we suggest in the guide. There can easily be concentration of signal at specific frequencies and so using DVD signal is somewhat more appropriate.

Well, after seeing all this, that kinda worries me. We typically use an action flick with a loud explosive scene to set the output. The problem is, that low freq rumble is a lot like pink noise – i.e., broadband. No, not 20 Hz – 20 kHz broadband, but certainly encompassing pretty much the entire bass region. Broadband low-passed, if you will. Since that’s what our most demanding movie program material is like, and since the BFD’s meter has problems showing us what’s going on inside its digital brain with such material, I doubt we’re getting an accurate picture when setting the levels with such material, or how the equalizing affected things.

I guess all that remains to be seen is if you get anything audible from the sub when you drive the BFD into clipping. I may give that a shot tomorrow.

In the meantime, I’m not worried enough about potentially loosing 16 dB in S/N ratio to tell folks they should avoid boosting when it’s needed. There are just too many BFD users out there who should have reported back that they had problems doing it, if it were a problem.

Regards,
Wayne