# What am I doing wrong?



## circularduck (Jan 3, 2009)

Or is this normal? I can't yet post images, but I ran REW without the BFD to setup my sub locations. Then I inserted the BFD and in bypass mode, re-ran the measurement. The output below 70 Hz dropped off by 30dB! What's going on?


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## glaufman (Nov 25, 2007)

That's certainly confusing... you're sure it was bypassed? You can go to our post-padding thread to get your post count up to 5 where you should be able to post images:
http://www.hometheatershack.com/forums/testing/21659-post-padding-thread.html


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## circularduck (Jan 3, 2009)

Here's the pic. 



I have all my filters except 4 and 5 off. I had it on 5, which is set to PA. I ran it with it on, then with the IN/OUT button off, both produced the same result. I have a feeling this is just something dumb I've done, but I can't figure it out.


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## circularduck (Jan 3, 2009)

Okay, the picture worked in the preview. I'll try again.


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## glaufman (Nov 25, 2007)

Well, admittedly, experience with the BFD is a weak spot in my experience... have you seen the guide here?
http://www.hometheatershack.com/forums/bfdguide/
An excerpt regarding the in/out (bypass mode)...


> You should be able to understand the connection process from the BFD Manual. On the rear of the BFD, above each Input/Output you will see an "Operating Level" button. Make sure this button is pushed in (the "IN" position) which is for the -10dBV (HOME) setting. Do not use the +4dBu (STUDIO) setting (leave this button in the out position). Once you have your BFD connected then you are ready to set the input level. .....On the top right front of the unit you will see the "IN/OUT" button. Press and hold this button for a moment until the button light blinks. You are now in the "BYPASS" mode with no filtering active. .....The input level is monitored by the LED's in the far left section of the display window. If the unit is not in the "BYPASS" mode then the LED's will monitor the "output" level.


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## circularduck (Jan 3, 2009)

I went into the bypass mode which disables the EQ (pressing the IN/OUT button until the indicator turns off). Total bypass mode is as you indicated (flashing indicator). I haven't tried that yet, but I should to see if anything else is going on. I'll hopefully try it tonight.


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## JohnM (Apr 11, 2006)

Are your sure the sub was still getting a signal after you inserted the BFD? That "after" trace looks awfully like a plot of a main speaker only. Best check your cables and the connections you used on the unit.


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## circularduck (Jan 3, 2009)

JohnM said:


> Are your sure the sub was still getting a signal after you inserted the BFD? That "after" trace looks awfully like a plot of a main speaker only. Best check your cables and the connections you used on the unit.


You're right, that's exactly what it looks like. I'll have to check when I get home what I've done to mess that up.


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## circularduck (Jan 3, 2009)

I'm not sure what fixed it, but I put in a dummy filter of 1dB drop, tried it, and everything seems good now. Thanks for the responses. Now I just have to find a good average between seating positions because the measurements are drastically different.


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## glaufman (Nov 25, 2007)

You can probably fix that drastic difference thing by adding a sub or room treatments, of course bass traps can be pretty large depending on the frequencies you need to hit.


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## circularduck (Jan 3, 2009)

I already have room treatments, corner traps, and 2 subs :help:

I still need to test more, but I have a feeling that in the back row, I'm getting a combination of crossover effects and one of the new filters I just set causing a huge reduction in output from 50-80 Hz (if I remember correctly). I can post the graphs when I get home. Here are some older pics of the theater. I have my 2 subs between my center speaker and L and R speakers behind the screen.


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## glaufman (Nov 25, 2007)

Well, could be that traps (of reasonable size) often don't provide a lot of effectiveness at freqs under 100Hz. Looks like you only have traps in 2 corners, could be that you need more, or put them in different places... Could be that your subs (and/or LPs) are in less than optimal positions.

Sketch of the room layout perhaps? You could also get other ideas over in Acoustics.


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