ART 351 help please!!

Craig,
Setting up a sub EQ can be tricky business. It certainly helps to know what you’re shooting for going in.
I noted that you were trying to get all frequencies at the same 80Hz SPL reading. Trying to achieve flat response the most common mistake people make when trying to EQ a sub. Flat response does not result in natural-sounding bass. Highly regarded equalizer manufacturers like AudioControl and Ashly correctly recommend a so-called “house curve,” a gently cascading response that slopes downward from the lows to the highs. Such an EQ curve sounds warmer and more natural to the human ear. The severity (for lack of a better word) of the curve is dependent of the size of the room. Smaller rooms require more boost than larger rooms, but the good news is that small rooms naturally boost low end response, so you don’t need to force it with an equalizer.
EQing a proper house curve is difficult and time consuming. The trick is determining how steep or how gradual the response curve in your room needs to be.
Since you are going to equalize your subs, Craig, the first thing I recommend would be to place them in the same corner. Trying to EQ subs in two different locations takes ten times the effort. Trust me, I've done it! You can forget all the talk you have heard about placing subs where they “sounds best.” In moving the subs around the room they are trying to find a place where the inherent room spike is less offensive, hopefully resulting in somewhat smoother response. The equalizer is going to do all that for you. When you are finished, corner placement with EQ will give you lower extension, smoother response, and higher SPL level than unequalized subs will ever realize with “proper placement.”
Despite what I said about EQing for flat response, that is the place you need to start. Achieving response as flat as possible (within a dB or so) will give you a point of reference when you begin to re-adjust for your house curve. You have already noted that moving one band affects the adjacent frequencies. This is common with all equalizers, and is something you have to compensate for by re-adjusting the other affected bands.
You have already determined that flattening response makes it seem like the bass is gone. Well, it has! EQing out say, a 10dB peak is the same as reducing the overall gain by that much, so the next thing you need to do is turn up the volume of the sub until it sounds more correct. I say “more correct” because we haven’t yet dealt with the needed house EQ curve.
The only way to determine the proper house curve is by listening. For your listening test, you need a CD that has a bass line that runs from high notes to low notes. Ultimately, the goal is for the volume of each note to be the same as the others (assuming it is that way on the recording—gotta watch out for that, too).
Pay attention to the lowest notes especially. With your initial listening, you will most likely find the bass gets weaker the lower the notes go (such is the nature of measured flat response), so adjust the EQ to compensate. It helps to know what you’re “shooting at:” The lowest note (E) on a 4-string electric bass is 40Hz; the lowest note (B) on a 5-string bass is 30Hz. If the lowest notes start to get overpowering, obviously at that point you have made your house curve too severe.
When everything finally sounds right, take new dB readings with the test tones. You will find that the lowest frequencies read progressively higher dB levels than the upper bass frequencies, even if they “sound” like they’re the same volume. This is natural, so don’t be alarmed.
At about 30Hz you might want to part ways with the house curve theory. I found that if the frequencies below 30Hz are boosted significantly higher, there is a lot of annoying infrasonic energy that is unnatural and distracting with music, and even videos. Once again, you have a difference between the way it sounds vs. the way it measures. A 20Hz test tone should read a few dB higher than at 30Hz, but to your ears 30Hz will sound louder. Trying to make 20Hz sound as loud as 30Hz will require more boost from the EQ, and then you will run into that annoying low-freq energy thing.
If you can endure all this, Craig, you will find the results worth the effort. You’ll never go back to unequalized subs.
Good luck,
Wayne A. Pflughaupt
------------------
My Equipment List
[Edited last by Wayne A. Pflughaupt on October 12, 2001 at 11:59 AM]