Active crossover. A crossover that splits the signal before the amplifiers, so each band gets its own amp channel. The DCX2496 is the active crossover in this rig; there are no crossover parts inside the boxes except the piezo plate.
Aquaplas. A damping coating JBL put on its horns to stop the metal ringing. The 2350 radial horn is aquaplas damped.
Auto-Align. The DCX2496 function that measures each band with a microphone on INPUT C and sets output delays so every box arrives at the listener together. See Section 2.
Aux send. A knob on each mixer channel that sends a copy of that channel to a separate output. On the M-106 the AUX send is pre-fader and feeds the echo; the EFFECT send is post-fader and feeds the spring.
Balanced. A connection with two signal wires plus ground (XLR) that cancels hum picked up along the cable. Unbalanced connections (TS, RCA) should be kept short.
Bass reflex. A box with a tuned opening (port) whose air resonates to extend the bass below what the driver does alone. The Ruby subs and the Altec 816A are bass reflex.
Bricolage. Making something from whatever is at hand. Mashup Sound is a bricolage of parts from different makers and decades. See Section 1.
Bus. A mixing path that collects channels on the way to an output. The M-106 has four buses; buses 1 and 3 feed the DCX.
Clip. What happens when an amplifier or input runs out of voltage: the tops of the wave are cut flat and it sounds harsh. Clipping can damage tweeters. The GX5 has a CLIP light.
Compression driver. A high-frequency driver with a light metal diaphragm that feeds a horn through a small throat. The JBL 2440 is the compression driver on the 2350 horn.
Cone. The moving part of a woofer that pushes the air. Its edge is held by the surround, its center is covered by the dust cap, and the voice coil behind it moves it.
Crossover. Filters that split the music into frequency bands so each box plays only its part: subs, scoops, kicks, mid and horn. The crossover points are in Section 2.
dB (decibel). A ratio on a log scale. +6 dB is twice the voltage, +3 dB twice the power, and about +10 dB sounds twice as loud.
dBu. A voltage level: 0 dBu is 0.775 V. Pro gear works around +4 dBu. The limiter thresholds in Section 2 are given in dBu and as a DCX setting.
dBV. A voltage level: 0 dBV is 1 V. Home gear (RCA outputs) works around −10 dBV.
Delay. Holding one band back by a few milliseconds so it arrives at the same time as the others. Set on each DCX output by Auto-Align.
Dub. Jamaican remixing that strips a record back to drum and bass and builds it up again with echo, reverb and drop-outs, pioneered by King Tubby. See Section 1.
Dub siren. A small synthesizer that makes rising, falling and pulsing siren sounds, played live over the records. It plugs into channel 4 of the M-106. See Section 10.
Echo. A delay effect that repeats the sound, the main effect in dub. In this rig an echo pedal sits on the M-106 AUX send.
Excursion. How far a cone moves in and out. It grows as the frequency drops, which is why the bass bands are high-passed and limited.
Fader. A sliding level control. The M-106 has a fader on each channel and on each bus.
Gain. The level boost or cut on a DCX output. The gains in Section 2 were set by ear on 2026-10-22.
GuardRail. QSC protection in the GX5 that turns the amp's gain down when it is driven into heavy clipping or runs hot.
Half-space. A speaker on a large flat surface such as the floor or ground. Half-space measurements read about 6 dB higher than free space.
Headroom. The margin between the normal level and the point where something clips or limits.
High-pass filter. A filter that passes frequencies above its setting and cuts those below. It keeps deep bass out of boxes that cannot handle it. A low-pass filter does the opposite.
Horn. A flared passage that couples a driver to the air. It makes the driver louder for the same power and controls where the sound goes. The narrow end is the throat, the wide end the mouth.
Impedance. A speaker's AC resistance, in ohms. Most boxes here are 8 ohm; the 2440 and the piezo banks are 16 ohm.
Kicks. The two Altec 816A boxes with EV EVM-15L drivers. They play 80 to 300 Hz: the punch of the kick drum. See Section 5.
Limiter. A control that stops a band's output going above a set level (the threshold), to protect the drivers and amps. Each DCX output has one; its LIMIT light shows when it is working.
Linkwitz-Riley. The crossover filter type used throughout (LR24 = 24 dB per octave, LR48 = 48 dB per octave). Two Linkwitz-Riley filters at the same frequency add up flat.
Mono. One channel. The rig is mono: there is no left and right, and pairs are numbered 1 and 2.
Mono summing. Combining a record's left and right channels into one signal. Each deck here is summed by an RCA Y-adapter; Section 10 lists every way to do it.
Moving-magnet cartridge. The usual DJ and hi-fi cartridge type (MM): magnets on the stylus move past fixed coils. Its matched coils are what make the RCA Y-adapter safe.
Pad. A fixed attenuator. The −20 dB inline XLR pad before the horn's amp channel lowers hiss and keeps the horn's limiter in a usable range. See Section 2.
Pan. On the M-106, a channel's PAN sends it between the odd and even buses. It is also used for cueing.
Phono input. A turntable input with RIAA equalization and extra gain. M-106 channels 3 to 6 have phono inputs.
Piezo tweeter. A tweeter driven by a crystal that flexes with voltage. The piezo plate holds eight GRS PZ1005s and carries the top octave. See Section 8.
Pink noise. Random noise with equal energy in each octave, used for measuring and for Auto-Align.
Polarity. Whether a cone moves out or in for a positive signal. A box with inverted polarity cancels its neighbor where they overlap. Check every box with a 9 V battery.
Port. The tuned opening in a bass reflex box. Its tuning is the frequency where the port does most of the work.
Preset. A stored DCX setup. Save the rig's settings as MASHUP with the date.
Rack unit (U). The height unit of equipment racks: 1.75 in. Each GX5 is 2U.
Radial horn. A horn with flat sides that fan out, giving a set coverage pattern. The JBL 2350 is a 90 x 40 degree radial horn.
Recap. Replacing an amplifier's electrolytic capacitors. Three of the GX5s were recapped. See Section 9.
Release. How quickly a limiter lets go after the level drops, in milliseconds.
REW. Room EQ Wizard, free measurement software, used with a measurement microphone to check the rig's response.
Scoops. Sound-system bass horns: a driver at the top firing into a folded horn that opens at the front. Here two scoops with JBL 2226H drivers play 50 to 80 Hz. See Section 4.
Selector. The person who chooses and plays the records at a sound-system dance.
Sensitivity. How loud a speaker plays for a given input, in dB at 1 m with 1 W or 2.83 V.
Sound clash. Two sound systems playing against each other for the crowd: the old test of a system.
Sound system. A mobile stack of speakers, amps and records run by a crew, from the Jamaican tradition. See Section 1.
Speakon. A locking speaker connector. Every box here has a Speakon inlet.
SPL. Sound pressure level, in dB. dBA weights it toward the middle frequencies like the ear; dBC counts the bass more fully.
Spring reverb. A reverb made by sending the signal through metal springs in a tank. Here it sits on the M-106 EFFECT send.
Subs. The two Ruby 18 in subwoofers, the deepest band: 40 to 80 Hz. See Section 3.
Thiele-Small parameters. A driver's measured constants (Fs, Qts, Vas and others), used to design or check a box.
Threshold. The level at which a limiter starts working.
Time alignment. Delaying the closer or faster boxes so all bands arrive together. Done with Auto-Align. See Section 2.
Toasting. A deejay talking or chanting over the records, a Jamaican sound-system tradition that led to rap.
Wedge. The planned mid horn box for one JBL 2123H, shaped to match the 2350's footprint. See Section 6.
XLR. The three-pin balanced connector used for line-level signals from the DCX to the amps.
Xmax. The farthest a cone can move and stay linear. Past it, distortion rises fast and the driver can be damaged.
Y-cable. An XLR cable that splits one female into two males, to feed both channels of an amp from one DCX output.