New 2496 not behaving

[jwatte]

My background is in pro audio. I generally don't like Behringer because of the "chinese" build "quality," (call it snobbery or just the knowledge that things get banged up when moved) but for a home theater, it might do OK. Thus, I got an SPL meter, a BFD, and hooked it all up to the laptop with REW.

My home set-up is a Sony AVR, an Ebtech Line Level Shifter (to go from RCA to balanced), a powered subwoofer that does built-in bass management, and powered monitors. Here's the first snag: because the AVR doesn't do BM, I'd really need to EQ all the channels going into the subwoofer. However, as the main problem with bass response is for music (stereo) material, I'm OK with just running EQ on FL/FR, so I hooked up the BFD in stereo mode.

Now, to test it, I dialed in a manual filter. -36 dB at 60 Hz, 0.1 Q. Should make some change in the measured response, you'd think? Well, nothing happens -- the curves look the same. When dialing in a -12 dB filter at 36 Hz, I get a sharp valley at around 120 Hz in the measured response. When I use the REW to find peaks (it finds 4 peaks), and upload the data using MIDI, a successive measurement finds almost no change.

If it wasn't for the valley at 120 I get by dialing a filter at 36 Hz, I'd think the BFD was doing nothing. However, when putting it in Bypass mode, the 120 Hz valley goes away, so it's doing SOMETHING.

What's going on? Is there some bum firmware in my unit? Is there a firmware update I should get?

[brucek]

There could be any number of things you're doing wrong.

I first have to question your filter (-36 dB at 60 Hz, 0.1 Q). The width of filters for the 2496 and 1124 (when selected as the equalizer in REW) express their width in BW and not Q. Do you have the correct equalizer selected in REW?

Be sure the filters are engaged in the eq and not in BYPASS mode.

Either way, the best method of establishing the validity of filter correctness in an eq is to play a single SINE wave with REW (easy to do with the signal generator) and select that frequency for a filter with the equalizers front panel (none of that wacky midi stuff) and set an appropriate bandwidth and start attenuating and observe the audible effect. You'll know pretty quick if it's working.

brucek

[Wayne A. Pflughaupt]

Welcome to the Forum, jwatte!

Don’t know about the 2496, but the 1124 expresses bandwidth as xx/60-octave. If that’s what the 2496 does, and you’re using a bandwidth enumerated as “1”, that’s 1/60 of an octave, which is like the great granddaddy of all notch filters! You might not be able to see a measurable change with a filter that tight.

Regards,
Wayne

[jwatte]

I first have to question your filter (-36 dB at 60 Hz, 0.1 Q). The width of filters for the 2496 and 1124 (when selected as the equalizer in REW) express their width in BW and not Q. Do you have the correct equalizer selected in REW?

This is a manually dialed filter. The range for bandwidth is from 1/60th to 10 -- and I set it at 0.1 (meaning 1/10th of an octave).

I'll try a sine wave as well and report back.

[jwatte]

Alright, I know what's wrong. My AVR sends a COPY of the low frequencies to the sub, when the speakers are set to Large -- and there is no way to turn it off. This means I need three channels of control, which I don't have. If I EQ the mains, the sub still remains un-eq-ed. The only other solution I can see is to set the speaker size to Small, and do all the EQ on the sub out, and basically forego the nice, professionally matched BM that's already part of the sub/speaker set. Grumble.

So, it's a Sony STR-DA5200ES that has this problem. Just if you want to not run into the same problem as I have.

I don't like hard EQ-ing, because of the phase response, and because room modes really should be treated with room treatments, but for general bass shaping, and rolling off the worst of the wive complaints, I think it works fine!