WOW-so many unknowns. How is the system setup-physically. You said 4 mics- what are they? how far away for the sound source are they? What all is going on-instrument wise-you said vocals and drums-anything else (guitars-keyboards etc? If so-how loud are they playing?
Where are your eq's on the channels set?
What are the various meters on the different pieces of gear showing? Mixer-amp etc.
It could be any number of things-or a single big thing-or a combination of lots of little things.
You said 2x15" speaker with voice coils. Well I certainly HOPE SO. Without voice coils they won't produce any sound.
Are there any horns or high freq devices in the cabinets?
We have no amps ran through the mixer..that is being used exclusively for vocal and drum mics 1 shure 58 wireless for vocals and a three piece drum mic kit the drummer bought from who knows when the earth was still forming (but try telling him he needs some new stuff and see where it goes).
Peavey PV 215 Dual 15" 2-Way Speaker Cabinet Specifications:
Frequency range (-10dB, half space): 40Hz to 21kHz
Frequency response (±3dB, half space): 58Hz to 17kHz
Sensitivity (1w/1m): 98dB
Power rating (program): 700W
Peak power capacity (peak): 1400W
Maximum SPL: 123.5dB
Transducer complement: Dual Peavey heavy duty 15" premium woofers, RX14 1.4" titanium diaphragm dynamic compression driver on a 60° x 40° coverage constant directivity horn
Driver protection: Positive temperature coefficient resistor
Nominal coverage pattern: 60° x 40°
Electro-acoustic crossover frequency: 2.6kHz
Nominal impedance: 4O
Input connections: Two 1/4" phone jacks in parallel
Enclosure materials & finish: Trapezoidal, black carpet-covered enclosure with dado-joined 1/2" MDF (Medium Density Fiberboard) and a full-length, black powder-coated steel grille
Dimensions (HxWxD):
Front: 48.25" x 18.38" x 14.25", 122.6cm x 46.7cm x 36.2cm
Rear: 48.25" x 11.75" x 14.25" 122.6cm x 29.8cm x 36.2cm
Weight: 79lb. (35.9kg)
QSC GX3 Stereo Power Amplifier Specifications:
Power Rating:
8Ω / both channels driven / 1 kHz: 300 W
8Ω / single channel driven / 1 kHz: 350 W
4Ω / both channels driven / 1 kHz; 425 W
4Ω / single channel driven / 1 kHz; 500 W
2Ω / both channels driven / 1 kHz; 200 W
Distortion (typical): 20 Hz - 20 kHz: 1 dB below rated power 8Ω: less than 0.05% / 4Ω: less than 0.1%
Signal to Noise: (20 Hz - 20 kHz) 100 dB
Input Sensitivity: 1.2 Vrms
Voltage Gain: (8Ω) 32.2 dB
Output Circuitry: Class B
Power Requirements: (1/8 power, pink noise at 4Ω, 120 V) 6.3A
Frequency Response: 20 Hz - 20 kHz, +0, 1 dB
Dynamic Headroom (4Ω): 2 dB
Damping Factor: 100
Input Impedance (Ω): Greater than 20k (balanced)
Maximum Input Level: +24 dB (16 Vrms)
sorry bout the length of that but figured the actual specs would help