Project Master Blueprint: Hybrid MTM SLOB Tower Speaker

1. System Overview & Architecture

System Type: Hybrid 3-Way Floorstanding Tower (Active Bass / Passive Mid-High MTM).
Target Application: High-output, low-distortion reference monitors

2. Physical Geometry & Acoustic Alignment

Listening Distance: 96 inches (8 feet).
Speaker Separation: 64 inches center-to-center.
Baffle Architecture:
- Front faceplate: width 12.25 inches 18 inches High.
- Flared rear wings: 8" high 4.5" deep for stability.
Cabinet Tilt & Time Alignment:
- SLOB Enclosure features a 10° backward rake (pulls the tweeter back ~200 mm relative to the listening plane).
- SLOB 8-inch woofers sit inside a slot roughly 127 mm deep.
- Net Acoustic Offset: The tweeter/midrange acoustic center sits roughly 73 mm further back than the bass slot center.

3. Driver Complement & Electrical Loads

Bass Section (SLOB): 6x 8-inch woofers wired in a series-parallel matrix. Total Nominal Load: 5.33 Ohms.
Midrange Section (MTM): 2x Peerless SDS-160 paper cone midranges.
High Frequency (MTM): 1x Vifa/Peerless XT25 ring radiator tweeter.
MTM Combined Load: 4 Ohms nominal.

4. Amplification & Hybrid Signal Routing

Mid-High Section (MTM): Powered directly by the Yamaha HTR-5760 full-range speaker outputs (handling multi-channel and stereo sources). Protected by an internal passive high-pass/bandpass network.
Bass Section (SLOB): Driven by the TDA7498E amplifier, fed via line-level pre-outs routed through a Taramps PRO 2.4S DSP.

5. Crossover Topology & Component Values

Active DSP Filters (Taramps PRO 2.4S - Bass Channel)

Subsonic HPF: 25 Hz at 48 dB/Octave (protects sub drivers from over-excursion). Two 12" 4 cu ft Subs are used from 25hz to 50hz.
High-Pass Filter (HPF): 50hz 12db/Octave Linkwitz-Riley.
Low-Pass Filter (LPF): 350 Hz at 12 dB/Octave Linkwitz-Riley.

Internal Passive MTM Board (Parallel-Branch Topology)

Loudspeaker Prototype: Passive Crossover Network Parts & Functions
- Project Enclosure Type: xrk971-Style Slot Loaded Open Baffle (SLOB)
- Configuration: 3-Way Hybrid (Active Bass / Passive MTM Mid-High)
- Crossover Frequencies: 350 Hz High-Pass (Mids) & 2,000 Hz Acoustic Intersection (Mids/Tweeter)
1. Midrange Bandpass & Impedance Compensation Board
This board manages the dual Peerless SDS-160 paper cone midrange drivers in an MTM layout. It restricts low frequencies to prevent distortion from excessive excursion, rolls off high frequencies before handing over to the tweeter, and flattens voice coil inductance.
- 60 µF Bipolar Cap (Chp)
  - Description: Non-polar electrolytic capacitor wired in series with the positive input.
  - Function: Forms the first stage of the 350 Hz High-Pass filter. Blocks low bass frequencies to protect the midrange cones from over-excursion.
- 2.0 mH Inductor (Lhp)
  - Description: Large inductor wired in parallel across the midrange circuit.
  - Function: Completes the 350 Hz High-Pass filter section (2nd-Order Linkwitz-Riley). Shunts remaining low-frequency energy safely to ground.
- 0.7 mH Inductor (Llp)
  - Description: Factory air-core or heavy gauge coil wired in series on the positive line.
  - Function: Forms the first half of the upper low-pass filter, rolling off frequencies above ~1,900 Hz to transition smoothly to the tweeter.
- 10 µF Film Cap (Clp)
  - Description: Metallized film capacitor wired in parallel.
  - Function: Completes the low-pass filter layout, sharply dropping out high frequencies above the crossover point to clean up the top end.
- 4.0 Ohm 10W Resistor (Rz)
  - Description: Non-inductive, audio-grade power resistor in series with the Zobel caps.
  - Function: Part of the Zobel network. Acts as a resistive load to counteract the rising voice-coil impedance caused by driver inductance.
- 10 µF + 15/17 µF Caps in Parallel (Cz)
  - Description: Two capacitors combined in parallel to create a 25–27 µF bank.
  - Function: Completes the Zobel impedance correction network. Keeps the midrange array load flat and predictable near 4.0 Ohms for the filter components.
2. Tweeter High-Pass Board
This board processes the Vifa/Peerless XT25 Dual-Concentric Ring Radiator. It forms a clean high-pass cutoff at 2,000 Hz matching the midrange slope. Note: The tweeter must be wired in inverted polarity to prevent phase cancellation.
- 22.3 µF Custom Cap Bank (Ctw)
  - Description: Parallel cluster of 12 µF DMPC + 5.1 µF DMPC + 5.1 µF DMPC + 0.1 µF DFFC foil bypass.
  - Function: Forms the series block of the 2,000 Hz 2nd-order High-Pass filter. The premium 0.1 µF DFFC copper foil bypass capacitor improves high-frequency transient response.
- 0.29 mH Inductor (Ltw)
  - Description: Factory 0.39 mH plastic bobbin air-core inductor unwound to 0.29 mH.
  - Function: Wired in parallel across the tweeter line. Completes the high-pass filter curve and shunts lower frequencies away from the delicate tweeter voice coil.
- Polarity: Wire the XT25 tweeter in reverse polarity (+ to -, - to +) for correct 2nd-order acoustic phase tracking.
Padding Resistors: None (Targeting a resistor-free design, relying on the 13.5-inch baffle dipole gain and dual-driver parallel sensitivity stacking to match the XT25 efficiency).

📋 Consolidated Reference Sheet

1. Enclosure & System Configuration

Enclosure Type: xrk971-Style Slot Loaded Open Baffle (SLOB) baseline.
System Layout: 3-Way Hybrid Configuration (Active DSP Bass Routing / Passive MTM Mid-High Towers).

2. Driver Complement & Electrical Impedance Matrix

Sub-Bass / Bass Section (SLOB): 6x 8-inch high-displacement woofers wired in a series-parallel matrix per side. Total Nominal Load: 5.33 Ohms.
Midrange Section (MTM Tops): 2x Peerless SDS-160 paper-cone midranges flush-mounted in maximum physical overlap configuration (126 mm CTC spacing).
High-Frequency Section (MTM Tops): 1x Vifa/Peerless XT25 Dual-Concentric Ring Radiator tweeter.
MTM Combined Passive Network Load: 4 Ohms nominal.

3. Power Distribution & Signal Flow

Yamaha HTR-5760

Mid-High Tower Array (MTM): Driven directly by the high-current loudspeaker terminal outputs of the Yamaha HTR-5760 receiver (maintaining full multi-channel and discrete stereo routing flexibility).

Bass Array Section (SLOB)

Driven by the TDA7498E amplifier, fed via line-level pre-outs routed cleanly through the digital processing engine of the Taramps DSP.

Taramps PRO 2.4S

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