Q&A with the experts - Kevin Beller on Bass EQ

Question: There seems to be a baffling array of onboard equalizers for bass guitar available in the marketplace. How do I choose what is right for me in terms of frequencies and bandwidths?

Answer: First, ask yourself a few questions.
1. Do you only play one specific style of music or do you routinely play a number of different styles?

2. Do you have a particular tonal objective that you want to pursue or are you looking for general purpose EQ?

3. Do you think you will be making a lot of EQ adjustments on-the-fly or do you tend to set-and-forget your EQ?

Equalizers can be broken down into two basic types, Parametric and Graphic. Parametric EQ gives the user complete control over frequency, bandwidth (or Q) and filter gain (boost and cut). They are more complex in terms of the number of controls. Using one effectively requires a good technical understanding of their operation. They have ultimate flexibility but can be cumbersome, even for the technically advanced and are not well suited to anything more than the most basic on-the-fly adjustments. The circuit topology is more complex, requiring a higher parts count. This translates into higher power requirements, which can be a problem in battery-powered circuits.

Graphic EQ has fixed frequencies and bandwidths. Because of this fact, it is important to select a package that suits your playing style. It is less flexible, but much easier to use and more conducive to on-the-fly adjustments. The circuit topology is simpler with less power consumption; better suited to battery-powered operation.

Reading the manufacturer's spec sheet can give you a good idea of what to expect from an equalizer. There are two critical parameters for a graphic EQ; center frequency and Q. In terms of the overall sound imparted by an equalizer, the treble frequency and Q are probably the most important.

Here are some general guidelines for treble selection:

• 6 to 7 KHz center frequency with a Q of 1.5 is a good frequency range for jazz fusion and funk playing when using active pickups. Boosting this frequency band will give a nice crisp response to pulled strings without adding harshness. Passive pickups typically do not have adequate response up this high; you will only end up increasing noise, so avoid this range if you play passives.

• 5 to 6 KHz center with a Q of 0.8 to 1.2 is a good general-purpose treble control. It will have the flexibility to address many different styles without becoming harsh or adding excessive noise. It will work well for active or passive pickups.

• 4 KHz center with a Q of 0.7 to 1.0 is good for Rock oriented player. It will give a harder attack to help in cutting through the mix but can become harsh if over boosted.

• All of the prior treble control discussion has dealt with peaking type filters, but you will also find another type that is called shelving. The names "peaking" and "shelving" are descriptive of the response shape. Shelving controls work with a much wider band of frequencies than most peaking controls. In a treble control they tend to produce a very "airy" sound that can be made very bright and articulate. They can also add large amounts of noise if excessive boost is employed. I personally prefer shelving treble controls to have a "knee" (-3dB point) of at least 4 to 5 KHz, otherwise they can sound harsh and "clanky."

Next on the critical list is the bass control. Here are some guidelines:

• Center frequencies in the 20 to 30 Hz range can often be felt more than heard if the Q is much higher than 0.6. I prefer a low Q of around 0.3 and a frequency of 30 to 40 Hz for a good all around bass control that adds depth and bottom without sounding too boomy.

• 20 to 30 Hz center with Q 0.6 and above will have a very "sub-bass" sound and would probably work well for Reggae or Hip-Hop.

• Bass controls in the 60 to 100 Hz range can give more apparent bass sound, they are boosting second harmonic more than fundamental, but can easily become too boomy if over boosted.

Next on the list is midrange, and in some ways, this could have been first on the list since it has the most potential for totally ruining your sound. But I put it last because I am going to trust that you all are going to use this control judiciously. Here are my thoughts on midrange controls:

• For bass guitar, I believe midrange frequencies in the range of 500 Hz to 1 KHz with moderate Q of 0.4 to 0.7 to be most useful. Boosting can increase punch and presence in the mix and cutting can hollow out a slap sound nicely. You can tend to get away with more cut, but too much and you will get lost in the mix. When boosting midrange, I tend to limit it to now more than a few dB, too much and you may find it difficult to blend into the mix properly.

There is a lot more that could be written on the subject of equalization, but this should be enough to get you off to a good start. At this point, if you refer back to the initial three questions at the beginning of the article and think about them in context of all this new information, you should be well on your way to selecting an onboard EQ that is right for you. Good luck in your search for tone.

Kevin Beller is Basslines' and D-TAR's Chief Engineer. Check out Bass Player Magazine for more Q&A with Kevin.