Troy_K
Stunt Coordinator
- Joined
- Jan 20, 2002
- Messages
- 87
... I didn't want to boost unless absolutely necessary.It’s fine to boost when you need to. In fact, look at your filter chart: Ten of the eleven filters are cutting. You didn’t do yourself any favors by doing this – the overall gain is dragged down so far you will have to turn the sub way up. Well, there goes all the “headroom” you thought you were conserving.
In fact, many of those valleys you initiated were caused by unnecessary frequency – like below 36Hz for instance. If the goal is flat response, it makes no sense to EQ a 1-octave area that is almost perfect to begin with - practically half of the sub’s entire frequency range in this case.
Looking at your unEQ’d response, your 32Hz and 100Hz points are pretty much at locations that will make a nice house curve. Don’t mess with anything below 32Hz – it’s flat and it’s fine. Work on sloping down from that point to put 100Hz at 89-90dB (or 5-6dB below 32Hz). This will give you a nice house curve, and you will probably find that the sub’s gain setting will be close to where it was before EQing – maybe even a little less.
So it’s entirely possible you will end up with a lower gain setting on the sub despite boosting the 40Hz area considerably. This is certainly better than before, EQing overall gain down so far that the sub has to be turned way up.
Regards,
Wayne A. Pflughaupt
The multiple filters will each introduce its own phase alteration.I'm not sure that this is true since the BFD does its filtering in the digital domain. Analog filters introduce phase shifts, but I'm not sure that the number crunching of digital filters has this problem.
I'm not sure that this is true since the BFD does its filtering in the digital domain. Analog filters introduce phase shifts, but I'm not sure that the number crunching of digital filters has this problem.Yep, absolutely. Interestingly, the design software I gave the download link for is quite useful in this regard. It displays two graphs. One graph shows the effect of a filter and the other graph shows the resultant phase shift caused by that filter. When you enter all your filters you see the overall response and phase change that will be introduced to the BFD's incoming signal.. This is quite useful in ensuring that you aren't changing the phase around the crossover point..
brucek
What do you suggest I start with for Q? I'm a bit worried about addding too much gain at 40, as I anticipate it will need at least 12-15 db gain which really seems to rattle things in areas other than my listening position. How much of a gain is safe to add?I’d start with a Q of 11.5 (1/8-octave) for the 40Hz problem. The idea is to accomplish your needed boost and not change 36Hz. If you see 36Hz boosting, squeeze the Q a little tighter.
To reduce 56Hz, start with a Q of 4.3 (1/3-octave). Since it won’t be cut much, you might need to open up the Q a little.
For 71Hz start with a Q of 11.5 (1/8-octave again).
Regards,
Wayne A. Pflughaupt