Behringer EQ700 Graphic Equalizer

Behringer Graphic Equalizer EQ700

The EQ700 Behringer guitar stompbox is an effect devoted to the sound modeling by means of an accurate shaping of the instrument frequency response. The EQ700 is a 7 bands graphic equalizer matching the native guitar frequency range, allowing the boosting/cutting of each frequency band up to 15 dB.



Figure 1: The Behringer EQ700 Graphic Equalizer

Available frequency sliders are 100 Hz, 200 Hz, 400 Hz, 800 Hz, 1600 Hz, 3200 Hz, 6400 Hz.
An additional fader allows to boost/reduce the overall effect level up to 15 dB. As far as the construction quality is concerned, the Behringer stompbox is made of good quality plastic material, such as all the "Boss style" stompboxes the german brand produces, but plastic can't rival with the metal used by other competitors in this field. Furthermore, the feeling of cheap manufacturing is confirmed by the slack behavior of the 8 sliders, even though the good overall usability of the stompbox is not compromized.

A common con of all such a kind of Behringer devices is the DC socket located on the right side of the stompbox instead of the front side; this better accessible position would allow an easier use of a single 9V DC power supply with a daisy chain connectors cable. Again, the access to the battery compartment cannot rival with the fast release mechanism Boss implemented with the rear screw.

The question I want to address in this article is quite simple: the cheap construction approach of the manufacturer also applies to the musical response of the EQ700? To give an answer not polarized by subjective perception, I used a signal generator and a spectrum analyzer to obtain the real characteristic of this sound processing device. For details about the adopted test methodology, a dedicated article will provide a complete description of the followed approach.

The following Figure 2, shows the result of the calibration of two "White Noise" type signals generated by means of a sound card connected to the PC and then reinserted into the line input of the same sound card to be analyzed by Visual Analyser 2011, a PC based signal analyzer software (http://www.sillanumsoft.org). It can be verified how the two tracks, obtained averaging 20 acquisitions in order to reduce the random signal components, are virtually overlapping, allowing us to use a signal path to feed the stompbox with the test signal and the other as a signal reference.

Figure 2: White Noise signals detected by the Spectrum Analyzer

After connecting the PC Line Out to the IN stompbox socket and its OUT socket to the Line In of the PC soundcard, the first step is evaluate the stompbox behavior in Bypass mode.

Figure 3 shows with the green channel the signal processed by the EQ700; perfect matching with the red channel reference signal provides the confidence that the signal is "uncolored" by traveling through the stompbox when it is in Bypass mode. The Behringer EQ700 is not provided with a "true bypass" function but it may noticed that the level loss is less than 1dB over the whole frequency range of interest.

Figure 3: The green channel shows the signal passing through the stompbox


The first test analyze the frequency response obtained with the stompbox activated and all the sliders in flat position (boost/cut of 0 dB). Figure 4 shows the obtained response. Note how the response is perfectly flat and level does vary just a few tenths of dB as compared to the Bypass mode: this is due to the lack of steady position on the sliders and this do not therefore allow accurate adjustment of the 0 dB reference.

Figure 4: Response of activated stompbox and flat controls

By varying only the level control to its maximum gain value position (+15 dB), and to the maximum attenuation (-15 dB), while maintaining the frequency shaping sliders at their reference position (0 dB), we obtain the plots of Figure 5 and Figure 6 for the signal processed by the stompbox (green trace).

　

Figure 5: Stompbox gain level of +15 dB

Figure 6: Stompbox gain level of -15 dB

The frequency response is always extremely flat over the full range of interest; this is an effective indicator of the good electronic project of this Behringer product, despite the expected 15 dB variation is limited to about 10 dB in boosting mode and about 13 dB in attenuation (the dynamic is about 23 dB instead of 30 dB nominal value).

The frequency responses to a 15 dB boosting of each single slider in turn, among the 7 available ones, are shown in the following figures:

Figure 7: 15 dB Boosting of the 100 Hz band

Figure 8: 15 dB Boosting of the 200 Hz band

Figure 9: 15 dB Boosting of the 400 Hz band

Figure 10: 15 dB Boosting of the 800 Hz band

Figure 11: 15 dB Boosting of the 1600 Hz band

Figure 12: 15 dB Boosting of the 3200 Hz band

Figure 13: 15 dB Boosting of the 6400 Hz band

Figure 13 shows how the last filter of the pedal is not a passband centered at 6.4 kHz but a high pass filter with cutoff frequency at approximately 6.4 kHz.

Conclusions - The instrumental analysis led to the evdence that in spite of the low quality of construction materials Behringer EQ700 is fully satisfactory in pure musical performance, giving an interesting solution in the non-professional applications fields; pro musicians require not only good musical performance but reliability and manufacturing robustness as well. In the field of amateur performance, the EQ700 offers excellent sound characteristics at an unrivalled price: many italian online music stores offer this stompbox at prices around 25 €; in the rest of the world this price could be even less!!

The synthetic rating of this guitar stompox made in China by Behringer is as follows:

CONSTRUCTION: Fair
AUDIO QUALITY : Excellent
RELIABILITY: Data Not Available
PRICE: Excellent