South Gym Audio Plan

Goals

• Provide clear, even audio coverage for spoken word and music playback
• Operate as an independent, self-contained audio system

Current State

The existing DSP is a MediaMatrix Xframe88 (1U) with an MM8802 I/O panel (1U). This is being replaced by two BSS BLU-100 units because:

• End of life: The Xframe88 is a legacy platform (Motorola 56002 DSPs) that is no longer supported or serviceable. Replacement parts and expertise are increasingly unavailable. (See equipment reference for specs.)
• Better AMX integration: The BLU-100 supports direct control via IP or serial, allowing AMX to recall presets, adjust levels, and select inputs natively. The Xframe88’s control interface is more limited and harder to integrate with the current AMX system.
• More capable DSP: The BLU-100 offers modern DSP processing, flexible routing, and the ability to act as the system’s mux point – accepting M32R output as an input and switching between sources under AMX control. (See equipment reference for specs.)

Architecture

The South Gym audio system has two operating modes:

• Base mode (BLU-100): For everyday use – school gym, meetings, announcements, background music for dinner events. BSS BLU-100 processors handle all audio processing and routing, controlled entirely by AMX. No operator required.
• Complex event mode (Midas M32R): For live-mixed events – weddings, funerals, youth worship, concerts, banquets with live music. The existing Midas M32R mixer is the foundation, operated by a live sound volunteer.

The BLU-100s are the always-on backbone of the system. The M32R is patched in when an event calls for full live mixing capability.

Why two systems? The BLU-100s provide preset-driven, unattended operation for everyday use, but they can’t provide the real-time fader-per-channel mixing that a live operator needs for complex events. The M32R fills that role and is an existing investment that works well – there’s no reason to replace it. (See equipment reference for M32R specs.)

Signal Path

The rack-mounted DL16 is the central physical I/O point in the system. Wireless mic receivers connect to its inputs, and amplifier feeds come from its outputs. It connects to the M32R via AES50 when the M32R is in use.

Physical connectivity

 SOURCES                    BLU-100 #1 (U24)              BLU-100 #2 (U25)           RACK DL16 (U26-28)
 ───────                    ────────────────              ────────────────           ──────────────────
                           ┌──────────────────┐         ┌──────────────────┐       ┌──────────────────┐
 MIPRO #1 Ch A ──in 1──►  │                  │         │                  │       │                  │
 MIPRO #1 Ch B ──in 2──►  │  Inputs 1-8:     │ BLU Link│  Outputs 1-8:   │       │  Inputs 1-8:     │
 MIPRO #2 Ch A ──in 3──►  │  all sources     ├────────►│  all DL16 feeds  ├──────►│  sources from #2 │
 MIPRO #2 Ch B ──in 4──►  │  (analog)        │         │  (via BLU Link)  │       │                  │
 Arylic LP10 L ──in 5──►  │                  │         │                  │       │  (AES50 A to M32R│
 Arylic LP10 R ──in 6──►  │  Inputs 9-10:    │ BLU Link│  Inputs 1-2:    │       │   for mixing)    │
 N4321 SVSi L  ──in 7──►  │  M32R return  ◄──┼─────────┤  M32R return    │◄──────┤  Outputs 1-2:    │
 N4321 SVSi R  ──in 8──►  │  (from #2)       │         │  (from DL16)    │       │  M32R main L/R   │
                           │                  │         │                  │       │                  │
                           │  DSP: EQ, mix,   │         └──────────────────┘       │  Outputs 3-4:    │
                           │  MUX, limiters   │                                    │  monitor mix 1/2 │
                           │                  │                                    └────────┬─────────┘
                           │  Outputs:        │                                             │
                           │  1: ceiling L  ──┼──► Amp #1 Ch A ──► Ceiling Speaker L        │
                           │  2: ceiling R  ──┼──► Amp #1 Ch B ──► Ceiling Speaker R        │
                           │  3: sub (mono) ──┼──► Amp #2 (parallel) ──► Subwoofers         │
                           │  4-8: spare      │                                             │
                           └──────────────────┘       Amp #3 Ch A ──► Monitor(s) mix 1  ◄───┤
                                                      Amp #3 Ch B ──► Monitor(s) mix 2  ◄───┘
                                                         ▲
                                                         │ (daisy-chain additional
                                                         │  passive monitors)

                           ┌──────────────────┐
                           │  Midas M32R      │       ┌──────────────────┐
                           │  (cart)          │       │  DL16 (portable) │
                           │                  │ AES50 │  (stage)         │
                           │  AES50 A ◄───────┼───────┤  rack DL16       │
                           │  AES50 B ◄───────┼───────┤                  │
                           │                  │       │  DL16 (portable) │
                           │  Operator mixes  │       │  keyboards,      │
                           │  all inputs      │       │  guitars, etc.   │
                           └──────────────────┘       └──────────────────┘

 FAILURE MODES:
 ─────────────
 #2 fails → M32R inoperable; base mode (#1 sources → amps) still works
 #1 fails → base mode lost; re-cable DL16 outputs directly to amps, M32R drives room

Base mode (BLU-100)

For everyday use – no operator, AMX-controlled:

1. Wireless mic receivers are split to the BLU-100 inputs
2. Arylic LP10 feeds the BLU-100 as a line-level input (background music via AirPlay 2, Spotify Connect, Bluetooth, etc. – see equipment reference)
3. BLU-100s process the audio (EQ, levels, routing) under AMX control
4. BLU-100 outputs feed the amplifiers (via MUX)
5. Amplifiers drive the speakers

The rack DL16 and M32R are not in the active signal path in this mode.

Complex event mode (M32R)

For live-mixed events – operator at the M32R:

1. Wireless mic receivers feed BLU-100 #1, which routes mic audio to the rack DL16 via BLU Link through BLU-100 #2
2. Rack DL16 sends mic audio to the M32R via AES50
3. Portable DL16 on stage sends instrument inputs to the M32R via AES50 port B (independent of the rack DL16 on port A)
4. M32R operator mixes all inputs
5. M32R sends main mix back to the rack DL16 via AES50
6. Rack DL16 outputs 1–2 (main L/R) feed BLU-100 #2, which forwards to #1 via BLU Link for MUX switching to ceiling and sub amps
7. Rack DL16 outputs 3–4 (two independent mono monitor mixes) feed amp #3 directly
8. Amplifiers drive the speakers

Multiplexing (MUX)

The Peavey Pro-LITE 5.0 amps have a single combo XLR/1/4“ input per channel – they can’t accept two sources and switch between them. This means the mux must happen upstream of the amps.

Approach: BLU-100 internal routing. The M32R/DL16 output feeds into the BLU-100s as an input. The BLU-100 DSP selects between its own processing and the M32R passthrough, controlled by AMX. The BLU-100s are the single point feeding the amps in both modes.

This approach was chosen for three reasons:

1. It’s the only viable option for switching – the Pro-LITE 5.0 has a single combo XLR/1/4“ input per channel (see equipment reference), ruling out amp-level input switching. An external AMX-controlled audio switcher was ruled out as unnecessary complexity given that the BLU-100’s internal routing can handle the switching natively.
2. Equipment protection – routing the M32R output through the BLU-100s allows limiters to be applied to the M32R feed before it reaches the amplifiers. This protects the speakers and amps from damage due to operator error at the M32R (e.g., feedback, accidental hot levels).
3. Consistent output processing – regardless of which source is active, the BLU-100s can apply system EQ, delay, and zone routing to everything going to the amps.

BLU-100 to amp cabling

Balanced connections are required between the BLU-100 outputs and amp inputs. The BLU-100s are on UPS-isolated ground (via the RLNK) while the amps are on building ground (dedicated panel circuits). An unbalanced connection would allow the ground potential difference to appear as audible hum. Both devices support balanced I/O (BLU-100 balanced outputs, Pro-LITE 5.0 balanced combo XLR inputs at 20kΩ), so this is straightforward – use XLR cables, not 1/4“ TS. See Electrical Plan – Grounding for the full ground boundary analysis.

Two of the three amps are fed from BLU-100 #1 outputs:

• Amp #1 (ceiling speakers): Stereo — BLU-100 #1 output 1 to Ch A (left), output 2 to Ch B (right). Each channel drives one ceiling speaker.
• Amp #2 (subwoofers): Mono — BLU-100 #1 output 3 to one input; amp in parallel input mode (one input drives both channels, both channels drive subwoofers). The BLU-100 applies an LPF crossover before this output.

Ceiling speaker capacity: The current system has 2x Danley SH69 (4Ω nominal; minimum impedance not published — the spec sheet includes an impedance response curve but does not state a numeric minimum) — one per channel at 4Ω. The amp supports up to 2 SH69s per channel (2Ω parallel), for a maximum of 4 ceiling speakers on one amp.

At 2 per channel, the real-world impedance dip (typical for a 4Ω nominal speaker: somewhere around 3–3.5Ω, but unconfirmed for the SH69 — request the impedance curve data from Danley or measure it) means the paralleled pair could dip to ~1.5–1.75Ω at certain frequencies. Whether this triggers the amp’s protection (ACL) depends on how hard the amp is working — the limiter threshold in the BLU-100 determines the maximum SPL and therefore the maximum current the amp must deliver.

Maximum SPL at the farthest seat (30’ / 9m from nearest speaker with 4 speakers distributed across the 102’ width). SH69 sensitivity: 96 dB (1W/1m into 4Ω, derived from the manufacturer’s 99 dB at 2.83V/1m by subtracting 3 dB for the 4Ω load — see equipment reference). Inverse square loss at 9m: 19 dB.

With 4 SH69s on one amp, the system can produce approximately 103–104 dB SPL clean at the farthest seat before transient peaks begin triggering ACL at the impedance dip. A BLU-100 limiter set to keep output below this threshold ensures clean, protection-free operation. The 103–104 dB figure assumes the BLU-100 limiter is active and managing peak demands — without it, music crest factors (10–15 dB for live music) would push transient peak power well beyond the amp’s burst capacity at the 1.75Ω impedance dip. For reference: 100 dB covers speech, background music, and moderate-level events comfortably; 103 dB covers energetic live music for all realistic use cases in this room. Sustained levels above 105 dB in a ~7,200 sq ft brick-walled gym with no acoustic treatment would be uncomfortably loud regardless of amplifier headroom.

Note on room acoustics: The power calculations above use the free-field inverse square law (SPL drops 6 dB per doubling of distance). In this room — brick walls, rubber floor, no acoustic treatment — the reverberant field will add significant energy at the farthest seat, meaning actual SPL will be higher than the table predicts. This makes the power and headroom figures conservative (safe direction for hardware sizing). However, the added energy is reverberant (smeared in time), which degrades speech intelligibility — the room will be louder and less clear than the numbers suggest. Acoustic treatment (hanging baffles, fabric panels) would reduce the reverberant field, improving intelligibility without requiring more amplifier power. Until RT60 measurements are taken (see open questions), the free-field model is the appropriate conservative baseline for amplifier and limiter sizing.

Amp #3 (floor monitors) is not fed from the BLU-100. Floor monitors are only active during M32R complex events, where the M32R operator controls the monitor mixes. DL16 outputs 3–4 feed amp #3’s two channels as independent mono monitor mixes — the operator can send a different mix to each channel (e.g., a speaker’s monitor with more of their own voice, and a musician’s monitor with more instrument mix). In base mode, amp #3 is idle. See rack DL16 I/O allocation.

The Pro-LITE 5.0 has line-level through outputs (1/4“ jacks) that can pass signal to another amp (see equipment reference). For amps #1 and #2, these are not used.

Monitor daisy-chaining: The existing monitors (2x Community XLT41 + 2x Community CSX28-S2, all 8Ω) daisy-chain via Speakon loop-through connectors. The current 4 monitors fit comfortably at 2 per channel (4Ω load). Additional 8Ω passive monitors can be added up to 4 per channel (2Ω, the amp’s rated minimum) — 8 monitors total across both channels.

At typical stage monitor levels (~100 dB SPL), each speaker draws ~2W — the amp is delivering well under 1% of its output capacity regardless of impedance. Thermal stress, power draw, and supply current are all negligible. The 2Ω minimum impedance rating is the only real constraint: below 2Ω, peak current on transients (drum hits, sharp vocals) exceeds the output stage’s current-limiting threshold, causing the amp’s protection circuits to clamp the output and degrade the audio.

BLU-100 I/O Allocation

Each BLU-100 has 12 analog inputs and 8 analog outputs on Phoenix/Combicon connectors, plus a 48-channel BLU Link digital audio bus (2x RJ45). The two units connect via BLU Link (Cat 5e, up to 100m) to share audio channels between them. See equipment reference for full I/O specs.

BLU-100 #1 (U24) — Primary

BLU-100 #1 handles all active analog I/O and runs the core DSP design in London Architect (input mixing, EQ, dynamics, zone routing, MUX switching, output limiting).

Inputs:

Outputs:

10 of 12 inputs and 3 of 8 outputs are allocated. Inputs 9–10 receive the M32R main mix via BLU Link from #2 (no direct analog connection to the DL16).

Floor monitors (amp #3) are not fed from the BLU-100. They are driven directly from the rack DL16 outputs during M32R complex events — the M32R operator controls the monitor mix. In base mode (no M32R), floor monitors are not active. See rack DL16 I/O allocation.

BLU-100 #2 (U25) — DL16 Feed & Expansion

BLU-100 #2 connects to #1 via BLU Link (Cat 5e, IN/OUT daisy-chain). It owns all I/O that connects to the M32R system via the rack DL16 — both the source feeds (outputs to DL16 inputs) and the M32R return (DL16 outputs to #2 inputs). Wireless mic signals, N4321 SVSi audio, and Arylic LP10 background music enter #1’s inputs, travel across BLU Link, and exit #2’s analog outputs to the DL16. The M32R main mix return enters #2’s analog inputs and is forwarded to #1 via BLU Link for MUX switching. This consolidates all M32R-related I/O on a single unit — if #2 fails, the M32R is inoperable but base mode continues; if #1 fails, base mode is lost but the M32R can drive the room via emergency re-cabling (see failure impact below).

Outputs:

Inputs:

Latency: Routing through #2 adds ~1.6ms to the M32R mic path (BLU-100 A/D at 0.77ms + BLU Link transport at 0.23ms + D/A at 0.60ms). The full end-to-end complex event path (mic → BLU-100 #1 → BLU Link → #2 → DL16 → AES50 → M32R → AES50 → DL16 → #2 → BLU Link → #1 → amp) involves 3 A/D and 3 D/A conversions plus M32R DSP processing, totaling approximately 7ms. Both figures are well within acceptable limits for live sound reinforcement (~10ms perceptible threshold for monitoring, ~20-30ms for reinforcement).

Failure impact:

• #2 fails: The DL16 loses all source feeds (mics, N4321, LP10) and the M32R return has no path into the system. Complex event mode (M32R) is completely inoperable. Base mode still works — #1 has all sources on its own analog inputs and feeds the amps directly.
• #1 fails: Base mode is lost (all amp outputs are on #1). The M32R’s I/O paths through the BLU-100 chain are broken at both ends — rack DL16 source feeds (mics, N4321, LP10) are dead since they depend on BLU Link from #1, and the M32R return has no output path to the amps. Emergency re-cabling is required: (1) Re-cable DL16 outputs 1–2 directly to amp #1/#2 inputs with XLR cables, bypassing both BLU-100s entirely. (2) Re-patch MIPRO receiver XLR outputs directly to rack DL16 inputs 9–16 to restore wireless mic capability through the M32R (bypassing the dead BLU Link chain). The M32R operator mixes and drives the amps directly through the DL16. This sacrifices BLU-100 limiter protection and system EQ (the operator is fully responsible for levels), but it gets audio to the speakers with no software reconfiguration. The M32R operator would use the portable DL16 for stage instruments via AES50 B. Monitor feeds (DL16 outputs 3–4 to amp #3) are unaffected since they already bypass the BLU-100s.

Wireless Mic Routing to DL16

Each MIPRO ACT-727a provides per-channel balanced XLR outputs at line level. These connect directly to BLU-100 #1 inputs (no Y-split cables). To feed the rack DL16 for M32R complex event mode, the mic signals are routed digitally from #1 to #2 via BLU Link, then out #2’s analog outputs to the DL16 inputs.

Why route through the BLU-100 instead of Y-split cables: All routing decisions live in the London Architect DSP design rather than in cable topology. Future changes (adding a mic channel, adjusting gain before the DL16, rerouting a source) happen in software, not by re-cabling. Standard point-to-point cables are used throughout — no custom Y-splits.

The mixed outputs on each receiver are unused. The front-panel headphone jack on each receiver serves as a monitoring point during troubleshooting.

Rack DL16 I/O Allocation

The rack-mounted DL16 (U26–28) is the physical I/O hub for the M32R path. It connects to the M32R via AES50 (port A on the M32R).

Inputs (16 available):

Outputs (8 available):

AES50 routing (configured in the M32R Routing page — not the default; must be set during commissioning and saved as a scene/snippet):

• DL16 inputs 1–16 appear as M32R remote inputs via AES50 A, channels 1–16 (this is the default)
• M32R main L/R bus output routes to AES50 A, channels 1–2, which map to DL16 outputs 1–2 (requires explicit routing configuration)
• DL16 outputs 1–2 cable to BLU-100 #2 inputs 1–2 (balanced XLR → Phoenix); #2 forwards to #1 via BLU Link
• Two M32R mono mix buses route to AES50 A, channels 3–4, which map to DL16 outputs 3–4
• DL16 outputs 3–4 cable directly to amp #3 Ch A/B (two independent monitor mixes, balanced XLR)

The portable DL16 (stage) connects to M32R AES50 port B, providing 16 additional inputs for stage instruments. It is not cabled to the rack — it connects via the AES50 cable in the M32R umbilical.

Requirements

• Full-room coverage for spoken word (meetings, announcements, ceremonies)
• Music playback capability (background music for events, youth nights, wedding receptions)
• Wireless microphone support (handheld and lapel)
• AMX-controlled presets on the BLU-100s for unattended operation
• Ability to switch between BLU-100 base mode and M32R live mixing mode

Considerations

• Room acoustics: Gymnasiums are notoriously reverberant. Acoustic treatment or speaker selection should account for this. The room is 1228“ (102’4“) wide × 844“ (70’4“) deep × 225“ (18’9“) to ceiling rafters, 281“ (23’5“) to metal roof. Brick walls all around to 8’, then wood framing to ceiling. Dark green rubber gym floor, no windows, and no acoustic treatments — all hard, reflective surfaces. See reverberant field analysis below — this room’s reverberation is likely the single biggest factor affecting audio quality.
• Room partitions: No operable walls, partitions, or windows. All walls are fixed.
• HVAC and reflections: No bleachers or in-room HVAC units. The air handler is external with supply/return vents into the room. Ceiling-mounted circulation fans are present. Flutter echo assessment is pending on-site measurement.
• Stage position: Fixed at the front of the room, under the projection screen / future LED display(s). Monitor/fill speaker requirements are TBD.
• Speaker coverage modeling: EASE Focus 3 (free) will be used for speaker coverage prediction — SPL distribution, frequency response, and coverage uniformity. DXF floor plans can be imported as a background reference for tracing room geometry. Speaker manufacturer GLL files provide the directivity data. Room dimensions are known (102’4“ × 70’4“); speaker model is Danley SH69 — coverage modeling can proceed once a Danley GLL file is obtained.
• Speaker placement: Ceiling-mounted or wall-mounted speakers to keep the floor clear for sports and events
• Durability: Equipment must withstand a gym environment (temperature swings, ball impacts on grilles, etc.)
• Mic routing to DL16: Wireless mic receivers connect directly to BLU-100 #1. The mic signals are routed digitally to BLU-100 #2 via BLU Link, then out #2’s analog outputs to the DL16 for the M32R path. No Y-split cables — all routing is in London Architect. See wireless mic routing for details.
• Balanced connections by default: All analog audio connections will use balanced wiring unless there is a compelling reason not to. This applies regardless of cable length – even short in-rack runs. Balanced connections reject common-mode noise and eliminate ground loop hum at ground boundary crossings (see Electrical Plan – Grounding).
• AMX control of BLU-100: AMX communicates with the BLU-100 via serial or IP to recall presets, adjust levels, and select inputs.

Reverberant Field Analysis

This room’s reverberation is likely the single biggest factor affecting audio quality — more than speaker selection, amplifier power, or DSP processing. The SPL and power calculations in the ceiling speaker capacity section use the free-field inverse square law, which is conservative for hardware sizing but does not reflect how the room actually behaves.

The problem: direct field vs. reverberant field

Sound at any listener position is the sum of two components:

• Direct field: Sound traveling straight from speaker to listener. Follows inverse square law (−6 dB per doubling of distance). This is the “clean” signal with good speech intelligibility.
• Reverberant field: Sound that has bounced off walls, ceiling, and floor before reaching the listener. In a hard-surfaced room, this energy is roughly constant throughout the room regardless of distance from the speaker. It is smeared in time and degrades speech clarity.

The critical distance (Dc) is where the two are equal. Closer than Dc, the direct field dominates (good clarity). Beyond Dc, the reverberant field dominates (muddy, less intelligible).

Estimated critical distance for this room

Dc = 0.141 × √(Q × R)

where:
  Dc = critical distance (feet when R is in sq ft; meters when R is in sq m)
  R = S × ā / (1 - ā)           room constant (sq ft)
  S = total interior surface area (sq ft)
  ā = average absorption coefficient (0 to 1, higher = more absorptive)
  Q = speaker directivity factor  (higher = more focused)

The constant 0.141 is 1/√(16π), which is unit-independent — it works in
both imperial and metric as long as R and Dc use consistent units.
(Note: an earlier version of this document used 0.057, which is the
constant from a different formula — Dc = 0.057 × √(Q × V / T60) — where
V is room volume in cubic meters and T60 is reverberation time in seconds.
That constant does not apply when using room constant R.)

Room surfaces:

Estimated values:

• S ≈ 20,956 sq ft
• ā ≈ 0.07 (mid-range estimate for untreated hard surfaces)
• R = 20,956 × 0.07 / (1 − 0.07) = 1,467 / 0.93 ≈ 1,577 sq ft
• Q ≈ 8–10 for the SH69 (60° × 90° horn — much more directional than a typical cone speaker at Q ≈ 2). The solid-angle calculation for a 60° × 90° horn gives Q ≈ 8.7; Danley synergy horns may achieve Q ≈ 10 at mid-to-high frequencies due to their multi-driver design. Using Q = 10 as the estimate:
• Dc = 0.141 × √(10 × 1,577) = 0.141 × √15,770 = 0.141 × 125.6 ≈ 17.7 feet (5.4m)

At the farthest seat (~30 ft / 9m), the listener is roughly 1.7× beyond the critical distance. The reverberant field dominates but not as overwhelmingly as a much shorter critical distance would imply. The inverse square law is still degraded at this range — actual SPL will be higher than the free-field table predicts, and the reverberant energy degrades intelligibility.

Impact

• Hardware sizing (safe): The SPL table’s power estimates are conservative. The system needs less electrical power than predicted to achieve a given SPL target, because the reverberant field adds energy. Amplifier and limiter sizing based on the free-field model has built-in safety margin.
• Speech intelligibility (problem): The extra energy is reverberant — smeared in time, arriving from all directions. This degrades the Speech Transmission Index (STI). In untreated gyms this size, STI is typically 0.3–0.4 (solidly in the “poor” category per IEC 60268-16, where “poor” = 0.30–0.45). A target of 0.50+ (“fair,” with 0.60+ being “good”) is needed for reliable speech comprehension in a meeting or ceremony context.
• RT60 estimate: For an untreated brick/rubber gym of this volume (~135,000 cubic feet), the expected RT60 is approximately 3–6 seconds at mid frequencies. Good speech intelligibility requires RT60 under 1.5 seconds, ideally under 1.0 second.

What can be done

The SH69’s high directivity (Q ≈ 8–10) already helps — it puts more energy on the audience and less on the walls compared to conventional cone speakers (Q ≈ 2). This roughly doubles the critical distance versus an omnidirectional source. But even with good speaker directivity, the room’s absorption is too low for acceptable intelligibility without treatment.

Acoustic treatment options:

Target: To halve RT60, the total absorption must be doubled (Sabine’s equation: RT60 is inversely proportional to total absorption). With current absorption estimated at ~1,467 sabins (giving RT60 ≈ 4.5s), halving RT60 to ~2.25s requires roughly 1,500 additional sabins — approximately 90–125 ceiling baffles at 12–16 sabins each, or an equivalent mix of baffles and wall panels. This is a substantial treatment scope.

More realistically, a phased approach:

The exact quantity depends on the measured RT60 — start with measurement. (An earlier version of this section understated the treatment quantity needed by roughly 4×, confusing incremental absorption with the multiplicative relationship in Sabine’s equation.)

Next steps

1. Perform the REW measurement session (see below).
2. Model with EASE Focus 3 — once RT60 is known, the coverage model can include the reverberant field contribution and predict STI across the listening area. This drives both speaker placement and treatment quantity decisions.
3. Budget and scope acoustic treatment — treatment quantity follows directly from the RT60 measurement and the target STI. This is an open question (see open questions — room acoustics).

REW Measurement Session

All measurements below use REW (Room EQ Wizard) — free, cross-platform. One site visit with a laptop, a USB audio interface, and a calibrated measurement mic can cover everything. Schedule during a typical school day so HVAC and building noise are representative.

Equipment needed

Measurements to perform

1. RT60 (reverberation time)

• What: Time for sound to decay 60 dB after the source stops.
• Method: REW sweep or impulse response at 3–5 positions across the listening area (center, quarter-points, near walls). REW calculates T20/T30 (extrapolated RT60) per octave band from the impulse response.
• Why: Determines how much acoustic treatment is needed and directly feeds the critical distance and STI calculations in the reverberant field analysis above. This is the single most important measurement — everything else depends on it.
• Positions: Measure from the expected speaker locations to at least 3 listener positions (front third, middle, rear third of the room).

2. Ambient noise floor

• What: Background SPL with HVAC running, no program audio.
• Method: SPL meter (or calibrated phone app) at the mix position and at the farthest seat. Record A-weighted (dBA) and C-weighted (dBC) readings, or use REW’s RTA mode for a full spectrum view. Let it average for at least 30 seconds.
• Why: Sets the minimum level the system must exceed for intelligibility. If the noise floor is 50 dBA, speech needs to be at least 65 dBA (15 dB SNR) at every seat. Also identifies whether HVAC rumble is concentrated at specific frequencies that could mask speech.

3. SH69 impedance curve

• What: Impedance magnitude vs. frequency for the installed SH69 speakers.
• Method: Disconnect speaker from amp. Wire the interface output through the 10Ω reference resistor to the speaker. REW’s impedance measurement mode sweeps and plots the curve. Record the minimum impedance value and the frequency at which it occurs.
• Why: The SH69’s minimum impedance is not published. Two SH69s in parallel per amp channel present a load at or below the Pro-LITE 5.0’s 2Ω minimum. The actual impedance dip determines whether the amp’s protection circuits will engage at full power. If the minimum is above ~3.5Ω, the parallel pair stays above ~1.75Ω and is likely fine with BLU-100 limiting. If it dips lower, the amp channel count or limiter threshold needs to be reconsidered.
• Measure both speakers — they should match closely, but if one has a damaged driver or crossover component the curves will diverge.

4. Frequency response at listening positions (optional, but valuable if REW is already set up)

• What: SPL vs. frequency at listener ear height.
• Method: Play a REW sweep through the installed speakers (one at a time, then both) and measure at the same 3–5 positions used for RT60. REW generates the frequency response and can overlay all positions.
• Why: Shows coverage uniformity across the room, identifies frequency-dependent dead spots or comb filtering, and establishes the baseline for room EQ in the BLU-100. Doing this before and after acoustic treatment quantifies the treatment’s effect.

After the measurements

Equipment

Wireless Frequency Coordination

The MIPRO ACT-727a receivers cover 482-698 MHz across three switchable bands, each 72 MHz wide:

ISED Regulatory Restrictions

ISED’s Decision on the Technical, Policy and Licensing Framework for Wireless Microphones and SAB-003-17 define the following rules for the 470-698 MHz range:

Impact on the ACT-727a:

• Band 5UA (482-554 MHz): Safe. Entirely within the legal 470-608 MHz range. This is the primary operating band.
• Band 5US (554-626 MHz): Mostly safe. 554-608 MHz is legal (54 MHz). The top 18 MHz of the band contains a mix of restricted, legal, and prohibited spectrum: channel 37 at 608-614 MHz (6 MHz, avoid – radio astronomy and medical telemetry), guard band at 614-617 MHz (3 MHz, legal), and prohibited auction spectrum at 617-626 MHz (9 MHz, prohibited).
• Band 6UA (626-698 MHz): Mostly prohibited. Only 11 MHz (652-663 MHz duplex gap) is legal. The remaining 61 MHz is auctioned mobile broadband spectrum. Operating in this band risks regulatory violation and interference from/to LTE/5G base stations.

Compliance concern: The ACT-727a’s ACT auto-scan selects clear RF channels based on signal presence, not regulatory compliance. It does not know which frequencies are legally prohibited in Canada. If set to band 6UA, the auto-scan could select a frequency in the 617-652 or 663-698 MHz prohibited ranges simply because no strong signal is detected there yet. Restrict both receivers to band 5UA or 5US only. Band 6UA should not be used unless frequencies are manually set within the 652-663 MHz duplex gap and verified against ISED rules.

Edmonton Market UHF TV Stations

The following UHF broadcast stations in the Edmonton market (which includes Sherwood Park) must be avoided. Source: RabbitEars Edmonton market.

Each TV channel occupies 6 MHz. The ACT auto-scan should detect and avoid these as occupied channels. With 4 stations in band 5UA, the usable spectrum in that band is reduced from 72 MHz to ~48 MHz — still ample for 4 wireless mic channels (each needs ~200 kHz).

Multi-Receiver Coordination

The ACT-727a has pre-calculated intermod-free preset frequency groups. The exact group count and per-group channel structure need to be verified against the ACT-727a manual — the group details previously listed here were sourced from ACT-727 (non-“a”) documentation and may not match the 727a. (The equipment-reference.md cites “15 groups + 1 user-defined group” from the ACT-727 product page; neither figure is confirmed for the 727a.)

For a fixed installation with 2 receivers (4 channels), preset groups are the right approach — not auto-scan. Set both receivers to the same group (e.g., Group 1) and assign different channel numbers: channels 1-2 on receiver #1, channels 3-4 on receiver #2. Since the channels within a group are pre-calculated by MIPRO to be intermod-free, they coexist cleanly. Set once during commissioning and leave it.

The auto-scan is designed for portable use in unknown RF environments. For a fixed install where all wireless is controlled, the preset groups give deterministic, repeatable results.

MIPRO also offers RCS27 software (connects via the rear RJ-11 port) for PC-based monitoring and control, and the newer RCS2.Net for network-based coordination of up to 64 channels — but both are overkill for 4 channels in a fixed install.

Cross-facility coordination with the auditorium’s wireless systems is unlikely to be needed — the auditorium is a few hundred feet away through concrete/brick walls, which should put any signal well below the receiver noise floor. Confirm with a walk test during commissioning (see below).

Recommended Operating Configuration

1. Set both receivers to band 5UA (482-554 MHz) and the same preset group. Band 5UA has the most usable legal spectrum and sits entirely within the ISED-approved 470-608 MHz range.
2. Assign channel numbers during commissioning: channels 1-2 on receiver #1, channels 3-4 on receiver #2 (within the same group). Verify selected frequencies do not land on the 4 local TV stations (RF 16, 17, 25, 27 — see table above). The preset groups should avoid these automatically, but confirm during setup.
3. Band 5US (554-626 MHz) is the secondary option if band 5UA proves unusable. Manually verify selected frequencies stay below 608 MHz.
4. Do not use band 6UA unless frequencies are manually locked to the 652-663 MHz duplex gap.
5. Walk test for cross-facility isolation: During commissioning, turn on the auditorium’s wireless systems and verify no interference is received on the gym receivers. Walk the gym with a transmitter on each band while monitoring the auditorium receivers as well, to confirm isolation in both directions.

Open Questions

Room Acoustics & Speaker Design

• Has any acoustic measurement been done (RT60, STI), or is there a baseline reverberation estimate?
• Is there budget or structural willingness for acoustic treatment (hanging baffles, fabric panels, banners), or must the speaker design compensate for the room as-is?
• Can the ceiling structure support pendant-hung or flown speakers, or is wall mounting the only option?
• Are there existing speaker mounting points, conduit, or wire pulls reusable from the previous system?
• Room aspect ratio – does it favor a center cluster, a stereo pair, or a distributed grid?
• Is stereo imaging a priority for any use case, or is mono coverage uniformity more important?
• What is the maximum tolerable SPL variation across the listening area (+/-3 dB, +/-6 dB)?
• What is the target max SPL at the mix position or far seat for live music events?
• What is the ambient noise floor during a typical school day (HVAC, gym activity)?
• During live music with the M32R, does the PA carry the full mix, or does stage volume from backline/drums compete?
• If subwoofers are added, where can they be placed while keeping the floor clear for sports?
• Has cardioid subwoofer configuration been considered to reduce rear-wall reflections?
• What low-frequency extension is needed – 80 Hz (speech reinforcement) or 40-50 Hz (youth worship, music)?
• What grille material or protective cage is needed to withstand direct ball contact?
• Is the space climate-controlled during off-hours, or must speakers handle temperature extremes?

Signal Path & DSP

• What is the BLU-100 DSP processing chain order (gain trim, EQ, compressor, limiter)?
• What target output level (dBu) should the BLU-100 deliver to the Pro-LITE 5.0 inputs at nominal program level? What is the amp’s rated input sensitivity?
• What speaker delay values are anticipated (per-speaker or per-zone)? Does the BLU-100 have enough independent delay blocks?
• What room EQ target is planned (flat response, speech intelligibility voicing, or a blend)? Has a measurement session been planned?
• BLU-100 limiter configuration: absolute clip limiter, program limiter with release time, or both in series? What threshold?
• In M32R passthrough mode, does the signal bypass all BLU-100 DSP, or still pass through the output limiter and delay?
• What is the expected nominal output level from the DL16 when the M32R is feeding it? Is that compatible with BLU-100 input headroom?
• When AMX switches from base mode to M32R passthrough, is there a crossfade or mute during transition, or a hard switch? A hard switch could produce an audible transient.
• Can the BLU-100 limiter threshold for M32R passthrough be set independently of the base mode limiter?
• What AES50 cable type and max run length is specified for the umbilical? Has the planned distance been confirmed within spec?
• If the portable DL16’s AES50 passes through the M32R, does a rack DL16 fault also drop the portable DL16?
• Has the end-to-end gain structure been documented for both modes (mic capsule → receiver → split → BLU-100/DL16 → DSP → amp → speaker)?
• Pro-LITE 5.0 front panel attenuation controls: set-and-forget trim or operator-accessible? What happens to gain structure if an untrained person adjusts them?
• Is there a documented level agreement for M32R operators (e.g., M32R master at 0 dBVU = X dBu into BLU-100)?
• If AMX loses communication with a BLU-100, does it hold its last preset, fall back to a safe default, or go silent?
• Has cable dressing been planned to separate audio signal cables from power cables in the rack?

Wireless Microphones & Inputs

• With 4 wireless channels available (2x ACT-727a), what is the typical channel assignment for weddings (e.g., officiant + reader + musician + spare)? Is 4 sufficient, or could larger events need more?
• For youth events, what is the maximum simultaneous wireless channel count needed, and is it expected to grow?
• Are wireless instrument transmitters (guitar, bass) or IEM packs sharing the frequency pool with vocal mics?
• What antenna type is appropriate for the gym environment (omni paddle vs. directional log-periodic) given the metal ceiling structure? The ACT-727a uses 50Ω TNC connectors with DC bias for MIPRO antenna boosters.
• What is the worst-case distance from the rack closet to the farthest transmitter location? Does this exceed reliable range without remote antennas?
• Is remote antenna mounting (outside the rack closet, on a wall or ceiling) needed? Where, and what cable type/length? Note: If remote antennas are used, they must be electrically isolated from building ground (e.g., non-conductive mount or isolating bracket). The receivers are on UPS ground via the RLNK – if the antenna mount is bonded to building steel, the coax shield bridges the two ground references and creates a ground loop. See Electrical Plan – Grounding.
• Will the mic split be a labeled patch panel point for troubleshooting, or hidden in the back of the rack?
• How many simultaneous wired inputs are expected on stage at the largest event? Does the DL16’s 16-input count accommodate that?
• Are there instruments or sources requiring phantom power on the portable DL16?
• Is there a floor pocket or wall box for wired XLR drops (backup mics, DI boxes, podium mic), or do all wired sources go through the portable DL16?
• What does the M32R umbilical need to carry (network, AES50 for portable DL16, IEM returns, power)?
• How many stereo IEM mixes are expected, and do IEM transmitters need power and frequency coordination alongside vocal mics?
• What is the planned maximum umbilical length? Has it been verified against AES50 spec (100m for Cat 5e) including the daisy-chain to the portable DL16?
• Does the umbilical floor drop need to accommodate the M32R cart on either side of the room, or is a single fixed drop sufficient?
• What is the battery management plan for wireless mics (rechargeable vs. disposable, charger location)?
• For multi-hour events, who monitors receiver battery status and initiates swaps?
• If rechargeable, does the charge cycle fit back-to-back event scheduling (afternoon rehearsal → evening ceremony)?

Amplifiers & Speaker Wiring

• How many discrete speaker zones with independent level control are needed?
• Will all three amps be used simultaneously in all presets, or are the sub and monitor amps only active for certain event types?
• If the subwoofer and/or floor monitor outputs are removed (both TBD), what happens to the freed amp(s) — repurposed for additional speaker zones, kept as spares, or removed?
• Will the crossover for subwoofers be in the BLU-100 DSP or the amp’s “sub” input function? What crossover frequency and slope?
• What is the minimum speaker impedance the system will present? Confirm amps won’t go below 2Ω under any wiring configuration.
• At what impedance will the system most likely operate? This determines actual per-channel power and heat output.
• Has a room SPL calculation confirmed whether 15,000W of amplification (3x Pro-LITE 5.0) is appropriately sized, or significantly oversized?
• What is the expected speaker sensitivity (dB SPL/1W/1m)?
• If amps are oversized, is there a risk of front panel attenuation at very low levels reducing control resolution?
• What is the distance from the rack closet to the farthest speaker? Has wire gauge been calculated for run length and load impedance to maintain damping factor?
• Speaker wire type: in conduit, plenum-rated, or CL2/CL3? What does local code require for in-ceiling runs?
• Are speaker wires home-run (one per speaker back to rack) or daisy-chained within zones? Daisy-chaining changes the impedance the amp sees.
• Speakon pin assignments: consistent between amp output and speaker ends (NL4 1+/1- vs. 2+/2-)?
• Field-installed Speakon connectors at junction boxes near speakers – who terminates, what is the testing process?
• What is the BLU-100’s maximum analog output level (dBu) vs. the Pro-LITE 5.0’s input sensitivity for full power?
• Critical: do the Pro-LITE 5.0 through outputs carry pre-attenuation or post-attenuation signal? This determines whether amp #2’s input level is independent of amp #1’s attenuation setting.
• Is the BLU-100 limiter threshold set relative to the amp’s clip point or the speaker’s power handling?
• What is the power-on sequencing plan for amps vs. BLU-100s? Can RLNK enforce sequence for RLNK devices, and what about the amps on dedicated circuits?
• Is there AMX monitoring of amp fault conditions (DC fault, thermal protection), or will faults only be discovered when audio stops?