I understand the "basshead" mentality, I was 16 once too, but I figured since this is PG forum, most of you are spending big money on this stuff to get the most accurate sound reproduction possible, and of course to do so LOUDLY. With that said, I figured I'd write up a little something in the way of EQing, more of a HOW NOT to do it with some illustration to make it easier to understand why. At the end of the day, equalization isn't really a right or wrong thing, the end result should make it sound right to you. The purpose though is to flatten out the response if you have a particular frequency range that is louder or not as loud as the rest of the audio spectrum.
So, what is wrong with MOAR BASS???? Well, nothing if you do it right. The problems arise when we start boosting frequencies wildly down in that region without considering what is actually happening when you do so. To start, I'll assume most people are still using CDs over MP3s for tuning to make things easier. CDs technically have a maximum level of 0dB (zero); the below is the track "Ain't No Fun" by Snoop Dogg that I recorded from the 12" single to a .wav file. I've amplified it to a max 0dB to simulate a CD recording since I make my rips with a bit of headroom due to the variance in equipment I used to see in different club installations. So here is the waveform of the track you just popped into your CD player.
Now you're kinda feeling it but you're picking up your girl later and you want to get the fanny butter flowing right away and what bitch doesn't love BASS right? So let's turn up that 50hz knob on the graphic equalizer to boost by 6dB (1/2 way typically). That doesn't seem too crazy to me.
Doesn't look too crazy waveform-wise either. OK well let's be honest, Dre's G-funk stuff rules, but some of it doesn't get down super low apart from the kicks, so let's pump the 125hz knob up 6dB as well.
HOLY FUCK now your shit is slammin right? Here's the problem. See how the peaks of the waveform doesn't fit in the window anymore? Yes, that's a clipped signal. I zoomed in a little bit so you can see it better, so the waveform is stretched out left-to-right compared to before, but you can clearly see it goes beyond where the software can display the peak at 0dB. No matter what you do downline in your signal path, you can't "unclip" it. Technically, it was clipped in the example after the 50hz boost, but not significantly, probably not enough to do any real damage and unlikely audible.
Admittedly, this is a somewhat dumbed down explanation. Remember, we are talking about a music track here, not a sine wave at these frequencies. You may be able to play a 50hz test tone through your shit with your eq at these settings all day and be fine, especially if you have a higher power pre-out. But music is dynamic and somewhat unpredictable from recording to recording. So, what can you do?
1. If your shit isn't near loud enough for you with everything flat equalization-wise, YOU PROBABLY GOT THE WRONG SHIT or maybe you've got some installation issues somewhere that need addressed. If you're spending money on quality high power aftermarket gear, you really shouldn't require huge boosts in any frequency range or use of a "loudness" function.
2. You can try cutting frequencies "out of the way" to make more room for what you want to hear. Below is the same thing we've been looking at with the boosts, only I cut everything above 200hz to -3dB. This brings us back down to just barely clipping, not much to really worry about. This is not super realistic, but just to give you an idea that by cutting what you don't want/already hear enough of, you can create more "headroom" to accentuate what you do want and will likely require less boost to do so. This is zoomed back out again in relation to the last image.
3. ACTIVE CROSSOVERS!!!! Yeah! The only time I would even consider truly boosting 50hz and 125hz signal is down the path, post LPF. You have now filtered out the rest of the audio spectrum, which is what the example above did using equalization, only you did it by sending it to the speakers/amplifiers that will be playing them. You've still created more room for the amplifier to amplify the signal and thus avoid clipping. This waveform simulates a LPF rolling off at 200hz (fairly high) then a 3dB boost at 50hz and a 4dB boost at 125hz and we are still pretty safe. Note THIS IS NOT THE SAME AS BOOSTING AT YOUR EQ THEN SENDING TO THE XOVER!!! If you clip at your headunit/EQ, nothing can save you! Kill yourself! Just kidding, but turn it down fucko! As an FYI, this software is called Audacity, it used to be available for free on the web if anyone is interested in playing around with it. Its actually really great software, especially freeware.
