PREMININARY INFORMATION WLX, WLXGS User’s Guide The Martin Experience All material © 2007. Martin Audio Ltd. Subject to change without notice.
Wavefront WLX and WLXGS Hybrid™ Subwoofer Preliminary information Introduction The powerful WLX Hybrid™ subwoofer is designed to complement Wavefront W8L Series touring systems to provide deep bass with maximum efficiency. WLX Rigging options Standard WLX subwoofers are equipped with integral flying hardware. A non-flying version is available – the WLXGS (= WLX Groundstack). Standard WLX subwoofers may be flown from a standard W8LC grid via a single point W8LC lifting bar. W8LC Grid All material © 2007.
A combined WLX/W8LM grid (ASF20003 – not shown) has been designed to enable W8LM miniature line array elements to be flown beneath standard WLX subwoofers. Rear connector brackets (ASF20005) are also available for flying W8LC compact line arrays below WLX subwoofers. ASF20005 connector brackets enable WLX subwoofers to be angled downwards with respect to the W8LC compact line arrays to ensure optimum audience coverage.
Pin-outs and cabling WLX Input NL8 WLX -1 Driver – (& link -1) +1 Driver + (& link +1) -2 Driver – (& link -2) +2 Driver + (& link +2) -3 link -3 +3 link +3 -4 link -4 +4 link +4 All material © 2007. Martin Audio Ltd. Subject to change without notice.
Cable and panel connector part numbers Please note the following part numbers when ordering loudspeaker connectors to make up cables and patch panels Neutrik NL connectors NL8FC NL8MPR NL8MM 8 pole cable (female) 8 pole panel (male) 8 pole inline coupler (male-male) Connectors should be kept in good, clean, uncorroded condition to ensure full, undistorted loudspeaker performance. Corroded or damaged pins and sockets can cause severe distortion or loss of signal.
Sub-woofer crossover and alignment Crossover frequencies The original factory controller settings for W8L, W8LC and W8LM systems are intended for use with subbass systems such as the W8LS, WLX or WSX.
W8LM presets include the WLX sub-woofer so they have two (mono) or four (stereo) unlocked delays. The WLX channel defaults to zero because the WLX has the longest horn. The W8LM LF/Full-range and HF reference delays default to 3.931mS and 3.829mS respectively to time align the W8LM to the WLX when the grilles are aligned. W8L, W8LC & W8LM reference delays and Sub-woofer delays are left unlocked to allow users to align main systems and sub-woofers if placement causes misalignment.
Main to sub-woofer delays Reference settings The following table shows system delays to align various combinations of W8L Series main and sub-woofer system. These should be treated as important initial settings and will work without further adjustments where grilles are alignment. They are a good starting point for further time alignment.
In all cases, set the main (W8L, W8LC or W8LM) and sub-woofer controller output parameters as follows, making sure that controller inputs are initially set flat (no equalisation), 0dB gain, 0ms delay. Flown WLXs Side-by-side arrays Similar length (height) sub-woofer arrays should be placed beside the main system for consistent performance and maximum impact throughout the audience area. ViewPoint™ should be used to design matching arrays using the Match WLX function . . .
4 x WLX + 8 x W8LC mixed array for orchestral applications using Connector Brackets – ViewPoint™ Rigging View Stacked WLXs or WLXGSs WLX or WLXGS subwoofers may be ground stacked below the main system. Ground stacked subwoofers can be up to 6dB more efficient than flown systems – assuming an acoustically solid floor - thanks to half spaced boundary conditions. A solid floor can act as an acoustic mirror, doubling the effective array size. All material © 2007. Martin Audio Ltd.
Stacked system alignment A stacked subwoofer system should be placed directly beneath the main system with the subwoofer and main system grilles vertically aligned. Subwoofer grilles and main system grilles should be closely aligned so that they are at equal distances from a central audience area – preferably a well positioned mix position. If systems have to be physically misaligned, extra delay may be employed to compensate for the differing arrival times.
WLX sub-woofers may be time aligned without test gear as follows: 1) Start with the controller outputs delays set as per the above table 2) Use a laser tape measure to measure the distance to the main system grille and the WLX sub-woofer grille 3) If the WLX sub-woofers are closer than the main system, increase the WLX controller output delay (2.91ms for every meter of misalignment) 4) If the main system is closer than the WLX sub-woofers, increase the main system delay (2.
overpowered models - with suitably set controller limiters - without risking uncontrolled power bursts. The MA series power amplifiers’ regulated power rails also ensure maximum performance under the real-world concert conditions of less-than-optimum mains supplies and low impedance loads. Amplifier load tolerance An efficient subwoofer system in live concert conditions can act as a surprisingly dynamic and complex load.
have been checked and controllers have been set to suit the power amplifiers to be used. Music should be used to check that controllers are receiving and sending the appropriate signal bands and then each power amplifier level control advanced in sequence to check system operation and patching. Assuming that controller output levels and limiters have been left as recommended for WLX subwoofers, power amplifier level controls should be set to full (fully clockwise).
Symmetrically coupled 2-wide columns show a slight improvement in mid-bass amplitude and polar response - but the effect becomes insignificant in large, flat fronted arrays or widely spaced stage apron systems. 2-wide symmetrical columns of WLX/WLXGS may be horizontally arrayed to improve mid-bass coverage. Array shapes vs coverage WLX or WLXGS subwoofers may be stacked and arrayed in various configurations to increase sound pressure and tailor coverage.
Array Approx Boost (wrt single unit) Horizontal coverage Vertical coverage - Wide Wide +12dB Wide Narrow +12dB Narrow Wide +24dB Narrow Narrow In these examples “wide” means that there are no coverage nulls within the forward 180º at mid-bass crossover frequencies. Wide coverage arrays have significant output beyond 180º making them more prone to room colouration. “Narrow” means that coverage will drop significantly before 180º coverage is reached at the mid-bass crossover frequency.
Coverage angle for tightly packed flat fronted arrays -6dB Coverage Here is a simplified formula for calculating the main coverage angle of a tightly packed flat fronted array. * = approximate speed of sound in m/s. Varies with temperature (see Section 2a). Arcsin means “the angle whose sin is ...” Flat fronted cluster coverage patterns will be confined to one main lobe whose mid-bass crossover directivity is proportional to the size of the cluster. All material © 2007. Martin Audio Ltd.
The medium sized array (left) has significant output to ±90º whereas the large array’s ±90º output is dramatically reduced. A note on coverage nulls It is useful to be able to calculate where these first response nulls will occur for various frequencies as they indicate areas where coverage, transient response and directional information would be poor without fill systems. For symmetrical arrays nulls will occur either side of the on-axis line.
For instance, an 8 high ground-based stack of WLX/WLXGS subwoofers will act like the top half of a 16 high stack. It is possible to reach higher seating areas whilst retaining a tall vertical stack by electronically “tilting” the system - see later. Note that flexible floors may actually absorb sound at some frequencies so the situation isn’t always so simple in practice.
Again, a flexible side wall may absorb sound at certain low frequencies. Boundaries should always be treated with caution. Spacing It is possible to space out WLX or WLXGS subwoofers to provide a larger frontal area with fewer units but care must be taken to avoid irregular coverage at higher, mid-bass frequencies. The following formula gives the pressure ratio p(h) (wrt to the on-axis pressure) for any off-axis angle of a regularly spaced linear array: All material © 2007. Martin Audio Ltd.
Far field polar patterns can be quite complicated - even for a simple pair of subwoofers driven in unison. Wide spacing will cause off axis irregularities (combing) because time offsets start to become significant. An odd number of half wavelengths will cause nulls along the line of the loudspeakers (the 90º lines) - see the 2½ wavelength example above. An even number of half wavelengths will cause lobes along the line of the loudspeakers - see the 2 wavelength example below.
Horizontal splays Splaying WLX/WLXGS arrays horizontally will widen their mid-bass coverage. The following sketch shows an 8 wide x 3 high WLX/WLXGS array arranged in four symmetrical pairs for smooth mid-bass coverage. WLX/WLXGS Wide (Splayed with Radius = width) Horizontal coverage 43Hz 86Hz 172Hz 2 4 8 16 Wide 90º 60º 30º 90º 60º 30º 36º 60º 30º 36º 40º Note that lower frequencies remain focussed when large arrays are used with large radii.
Stacked WLX/WLXGS application examples The following sketches show how WLX/WLXGS arrays may be deployed for a wide range of productions and types of venue. All productions and venues present their own unique requirements and these examples are intended as a template or starting point for your own specific design. Examples 1 and 2 show typical set-ups for smaller venues.
(3) WLX/WLXGS set-up for very high power dance/rock production in narrow arena Gives narrow horizontal & vertical coverage up to 120Hz - allowing for ground effects. Example 3 shows a very high power dance or rock set-up for a narrow “shoe box” venue. Note the four-wide left and right WLX arrays for tight horizontal control and the more tightly packed apron systems for central focusing.
(5) Alternative set-up for wide venues Splayed WLX/WLXGS arrays for wide horizontal coverage. Example 5 shows a set-up for a TV shoot in a similar wide venue where sight-lines are critical. Note the lower profile, splayed arrays. Thrust stages Examples 6 show a typical set-up for a large, thrust stage productions.
Island stages (not shown) Island stages are simply four-sided versions of examples 3 and 5 and should be aligned using the same process. Tutorial on spaced systems Whenever two or more loudspeaker systems are fed with the same signal and their coverage overlaps, sound addition and subtraction will take place depending on the listener’s position. In the following example, the off-axis listener may hear delayed sound from the right hand system.
Addition & Subtraction The above shows how two pairs of sine waves (with identical amplitude and frequency characteristics) will sum. Pair (a) are in phase and add. Pair (b) are out of phase and cancel. All material © 2007. Martin Audio Ltd. Subject to change without notice.
Polar variations with frequency Whether particular frequency components add or subtract in the far field will depend on the loudspeaker system spacing, the angular offset of the listener with respect to the centre line, and the wavelength. The following polar responses show what happens when subwoofers are placed 8.6m apart and are driven in unison at various frequencies: 100Hz The polar plot shows the far field polar response of the two subwoofers when driven in phase with the same 100Hz signal.
These lobes could cause low frequency feedback problems on stage with the high microphone gains used for orchestral low string (cello, double bass) sections or for “unplugged” performances. 60Hz At 60Hz the spacing is an odd number of half-wavelengths again so we see side nulls again. 40Hz When the frequency drops to 40Hz, the 8.6m spacing = 1 wavelength. Again, the central response is maintained but there is a dip in response over wide areas either side of the centre.
40 Hz reduced spacing The above shows what happens at 40Hz if we reduce the spacing between the subwoofers to 4.3m. We get better central coverage without 40Hz side lobes - adequate for long, narrow “shoe-box” venues but wider coverage would be required for most arenas. 40Hz close coupled Close coupling would give a wider coverage at that frequency but the spacing could still give coverage irregularities at mid-bass frequencies due to the shorter wavelengths at higher frequencies.
Listeners in the 60º zone will hear the note at a reduced level and may be more aware of room reverberation because the direct-to-reverberation ratio would be poorer for that note. Other notes would give different effects. In practice, these peaks and troughs can be smoothed out with additional fill systems.
Note that it is important to keep the subwoofers tightly packed to avoid polar anomolies caused by spacing. Procedure The normal procedure is to measure the angle from the top of the vertical subwoofer stack to the highest/most distant seats (using an inclinometer) and to calculate the required delay increment with the formula shown. Example We wish to project bass/mid-bass punch to stadium balcony seats 30º higher than the top of our WLX stacks.
The following delay line taps would be required for the above system: t0 t1 t2 t3 t4 t5 t6 = = = = = = = 0ms 0.83mS 1.66mS 2.49mS 3.32mS 4.15mS 4.98mS Going further It is possible to apply electronic shaping to horizontal arrays. For instance, it is common to use curved main clusters for smooth mid and high frequency coverage. Ground-based subwoofer arrays should follow the same curvature to maintain mid-bass crossover coherence but this is often difficult due to flat-fronted stage structures.
