1st time setting up BFD

[grn1969c10]

I played with the BFD for the first time this afternoon. I dare say I'm impressed with the difference it made. I threw down some heavy filters which may not be ideal. This is my Cadence CSX-15 by itself with BFD in bypass.


This is how it looked with six custom filters.



Filter #, Center frequency, Bandwidth, Cut/Boost
F1, 25Hz, 2/5 octave, +8db
F2, 43Hz, 3/20octave, -6db
F3, 68Hz, 7/60octave, -12db
F4, 82Hz, 2/15octave, -12db
F5, 122Hz, 2/15octave, -6db
F6, 178Hz, 1/6ovtave, -6db

I smoothed out my other sub using the other channel filters.



and then put it all back together to get a mains + sub graph. Compared to some of my earlier graphs this is pretty exciting.



It was interesting to see the CSX respond to a stiff boost in the 25hz range. I was worried that if it were a null the added power would be cancelled out, but this did not seem to be the case. The JBL did not respond as well to added power at 25Hz.

[brucek]

Looks pretty good. How does the waterfall look?

brucek

[grn1969c10]

Probably not so good, but ignorance is/was bliss.

Do these indicate excessive ringing?

CSX-15 by itself with BFD in bypass....




CSX-15 by itself with BFD filters...




Full system - mains + subs (both of em)

[brucek]

You've still got some ringing that you could work on. Try and adjust the filters a bit closer to remove as much of it as possible.... Hopefully you Optimized the filters..

brucek

[grn1969c10]

Try and adjust the filters a bit closer

Would you expand that thought a little more? I'm not sure what aspect of the filter affects ringing. What should I be getting closer to?

[grn1969c10]

The kids came over to see Return of the king Wednesday night. During some of the epic battle scenes, the BFD was starting to flicker the red input level lights once in a while. There's not much I can do about it but turn the whole system down a little because the sub amp is already running wide open. Average spl was bouncing around 85db with the occasional KaWhummPhh tapping high nineties.

[clubfoot]

Did you optimise the sub location before using the BFD? i.e. Try to obtain the best response from the sub w/o the BFD by moving it around and/or adjusting your seating location. Then use the BFD to "trim", without applying +8db of boost.

[grn1969c10]

Did you optimise the sub location before using the BFD?

I moved it all around the perimeter of the room - from in the corner, to 1/3 wall length down the wall in both directions. I tried it facing the seats, facing the corner, parallel to the wall, etc. Nothing seemed to net me any positive gains in the 50Hz and below range. Occasionally the response fell off so rapidly at 32Hz that it appeared there might be a null there, but since that was so close to the subs tuning point, the curve never came back up providing the clearly defined shape of a null.

I'm investigating equalization because location wasn't helping, I haven't located a local source of rigid fiberglass yet, and I was able to borrow the BFD for free just to see what it could do for me. If it provides enough benefit - which I'm thinking is the case - I will have to purchase one.

Then use the BFD to "trim", without applying +8db of boost.

I'm still learning the ropes on selecting filters and how heavy handed I can be before negatively affecting quality and max SPL. That first set of filters was a learning exercise!

[brucek]

Would you expand that thought a little more? I'm not sure what aspect of the filter affects ringing. What should I be getting closer to?

You have some ringing (persistence of the signal at certain frequencies) that would be reduced if the filters were more closely matched to the resonance it is designed to reduce. Did you run the Optimize routine when creating the filters?

brucek

[grn1969c10]

Did you run the Optimize routine when creating the filters?

No. In round 1 I exhibited rookie enthusiasm and went for the KO constructing filters manually observing the effect on the measurements. Rounds 2 and 3 I decided to settle down and follow REW's recommendations.

Since REW only tries to reduce peaks above the target level, it sets somewhat minimalist filters. When I implement the filters and reestablish a new target curve, the target has shifted down revealing the "new" peaks. I detect peaks a second time and get a second set of recommended filters.

Is it OK to run set filter routine twice adding the 2nd set of filters to the first?

Is it OK to have two seperate filters at basically the same frequency?

Wouldn't it be better to manually lower the target level about three or four db before detecting peaks so that the first set of suggested filters would be effective without having to make a second pass?

[brucek]

Is it OK to run set filter routine twice adding the 2nd set of filters to the first?

No, run it once, optimize, tweak the filters while watching the graph and that's it. Use those filters.

You can set any level you like with respect to the target line before you run the filter routine by adding offset to the data. If you go above the target line, the filters will be more aggressive. If you offset it completely below the target line, REW won't recommend any filters.

brucek

[grn1969c10]

Thanks Bruce.

I think EQ-ing the subs is going to make a substantial improvement - enough to warrant the investment. I have ordered a DSP1124P from BSWUSA and am returning the DSP1100P that I borrowed. I think they are functionally equivalent. A 10% coupon from BSW was cheaper than what I could get with the 30% live cash back!

[grn1969c10]

I also ordered some cables from Sweetwater. My "sales engineer" called to confirm I really wanted to order what I ordered. He seemed to think that the budget HOSA cables might be inadequate. If their inadequate, maybe they shouldn't sell them! Anyway I ordered 1/4" TS to dual RCA plug cables so I can connect the BFD to the Subs with one cable and eliminate all of the adapters. I will still have to use a coaxial cable to a splitter to a pair of RCA-TS adapters for the BFD inputs.

Slightly off topic for the REW forum except for the fact that when it all comes in, I can fire up REW and hopefully post some new improved graphs!

[brucek]

He seemed to think that the budget HOSA cables might be inadequate.

Perfect for REW use................