SPL Readings

Martice

Screenwriter
Joined
Jan 20, 2001
Messages
1,077
I have some preliminary numbers after calibrating my sub. I only have the pre BFD numbers and my system was calibrated at 85db.


Here are some corrected Raw readings on the left and and my attempt to flatten the overall response of the readings on the right.

18hz - 72.0-----18hz - 72.0 (0)

20hz - 81.5-----20hz - 81.5 (0)

22hz - 84.5-----22hz - 84.5 (0)

25hz - 89.0-----25hz - 85.0 (-4)

28hz - 94.0-----28hz - 85.0 (-9)

31.5 - 94.0-----31hz - 85.0 (-9)

36hz - 94.5-----36hz - 85.5 (-9)

40hz - 96.5-----40hz - 85.0 (-11)

45hz - 92.0-----45hz - 85.0 (-7)

50hz - 85.5-----50hz - 85.5 (0)

56hz - 85.5-----56hz - 85.5 (0)

63hz - 91.5-----63hz - 85.5 (-6)

71hz - 92.5-----71hz - 85.5 (-7)

The crossover is set at 60hz.

I was able to flatten the overall response quite easily. I don't know how this is going to sound as I haven't entered the numbers in the BFD as of yet but I should be able to do that tonight.


Any opinions or advice about these readings?
 

MingL

Stunt Coordinator
Joined
Mar 26, 2003
Messages
214
You've made it sound so simple.... but there's more than meets the eye. Individual PEQ BANDWIDTH.

The intended values will cut well, but the filter's need the bandwidth to be set and that is more tricky in practise than on paper.

I tend to use varying bandwidths in my BFD and filters tend to affect adjacent frequencies very much. I always like to start with 5/60 as a starting bandwidth setting and work around to as I go along.
 

Martice

Screenwriter
Joined
Jan 20, 2001
Messages
1,077
You've made it sound so simple.... but there's more than meets the eye. Individual PEQ BANDWIDTH.
I don't think this is the going to be the most problematic of responses but I do realize that bandwiths will affect related frequencies and that's when I guess I will have to earn my lunch. Actually, if it weren't for the huge dip (between 50-56hz) in the raw column (on the left) I may have been on to a nice little curve. Although the peak in the mid 20's made my eye brows raise a little as well.

Any opinions?
 

Doug_B

Screenwriter
Joined
Feb 11, 2001
Messages
1,081
Along the lines of what Ming said, I think it may be more useful to try a single, broad bandwidth filter centered somewhere in the 32-36 Hz range and see what that does, versus separate filters at every freq from 25-45 Hz. Also, I would see if raising the 50 and 56 Hz dips by a few db is possible before trying to cut everything else to the current levels of these 2 freqs. If this is successful, you may find it a bit easier to deal with the 25-45 Hz range.

Doug
 

Wayne A. Pflughaupt

Moderator
Premium
Joined
Aug 5, 1999
Messages
6,587
Location
Corpus Christi, TX
Real Name
Wayne
Martice,

I take it you’ve done your research and bought into the oft-parroted “cut everything, boost nothing” nonsense? What you will end up with is, the output signal will probably be too low to drive the sub amp to the levels you need. I saw this happen to a fellow recently on another forum. You might want to take a look at that thread, as well as my post at the bottom that explains why the “cut only” approach is often futile.

Aside from that, what Ming and Doug told you is correct. Equalizing is not surgically cutting specific frequencies. Even if you could do that, there are many frequencies between the ones you have taken readings on, and you wouldn’t be changing them at all. So it really wouldn’t sound much different.

The trick is to select the correct filter bandwidth and change broad or narrow areas as a whole. For instance, if you really wanted to cut the 25-50Hz area, a 1/3-octave filter centered at 36Hz would go a long way, with secondary narrow filters at 28Hz and 45Hz to finish the job. So three filters would do about the same as the eight you’ve proposed for the same area.

Any opinions?
Here’s mine – worth exactly what it cost you.


Start with a 1/6-octave filter centered at 53Hz and boost about 6dB. The idea is to raise the depressed area yet keep the readings at 45 and 63Hz the same. So adjust the bandwidth until you achieve that.

If no change occurs at the depression, then you have a null. If that happens there’s nothing you can do about it, so cancel the filter to save headroom.

The next thing I would try to do is to get better extension with a 1/6-octave filter centered at 22Hz. How well this works will depend on the limitations of your driver and/or amp. Again, adjust the bandwidth so as to not affect changes at the 28Hz reading.

Regards,
Wayne A. Pflughaupt
 

Martice

Screenwriter
Joined
Jan 20, 2001
Messages
1,077
Start with a 1/6-octave filter centered at 53Hz and boost about 6dB. The idea is to raise the depressed area yet keep the readings at 45 and 63Hz the same. So adjust the bandwidth until you achieve that. If no change occurs at the depression, then you have a null. If that happens there’s nothing you can do about it, so cancel the filter to save headroom.

The next thing I would try to do is to get better extension with a 1/6-octave filter centered at 22Hz. How well this works will depend on the limitations of your driver and/or amp. Again, adjust the bandwidth so as to not affect changes at the 28Hz reading.
I will try your above advice and see what happens. I will post my readings pre and post BFD.

Thanks guys.
 

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