Xcelsus XXM425- Competition Series 4 inch midrange pair | Previous Demo

Technical Specifications

"The Best Small Midrange I Have Ever Heard" — Steve Head's Review

When a professional installer who has evaluated Scan-Speak Revelators, Dynaudio Esotan drivers, and dozens of other reference-grade midranges declares one driver "the best" without qualification, you pay attention. Steve Head's August 2021 review of the XXM425 wasn't just enthusiastic—it was specific about why this driver outperformed everything he'd tested:

This wasn't Steve's first encounter with Xcelsus—he had already crowned the XXM325 (3" version) as his favorite small midrange after it bested the Scan Revelator 12M, a driver that had dominated sound quality competition for over a decade. The XXM425 takes the XXM325's core technologies—spiderless suspension, carbon fiber cone, neodymium motor—and scales them to 4" diameter, increasing radiating area, extending low-frequency response, and maintaining the "lightning-fast" transient response that made the 325 legendary. The result, according to Steve, is a driver that delivers spatial imaging, tonal accuracy, and dynamic capability that defies its 4-inch format.

Spiderless Suspension System (SSS) — The Moving Mass Revolution

The single most significant innovation in the XXM425 is what it doesn't have: a conventional spider. In traditional midrange design, the spider (typically a corrugated phenolic-impregnated fabric disc) provides restoring force to center the voice coil and controls excursion. But spiders add moving mass (Mms), introduce nonlinear restoring forces that vary with excursion, and create mechanical damping that slows transient response. For a 4-inch midrange operating from 150 Hz to 10 kHz—a range that includes the critical vocal presence region and upper midrange harmonics—every millisecond of delay and every gram of moving mass matters.

Xcelsus' Spiderless Suspension System (SSS) eliminates the spider entirely, replacing it with a proprietary suspension geometry that achieves several simultaneous advantages:

• Reduced Moving Mass (Mms): Without the spider's mass, the diaphragm assembly (cone + voice coil + suspension) weighs significantly less. Lower Mms means higher acceleration for a given motor force, translating directly to faster transient response. Steve Head specifically cited "lightning-fast" dynamic output as a byproduct of this Mms reduction.
• Elimination of Spider Nonlinearity: Conventional spiders exhibit force-versus-displacement nonlinearity—the restoring force isn't constant across excursion, causing distortion. By removing the spider, SSS eliminates this source of mechanical distortion entirely.
• Reduced Mechanical Damping: Spiders absorb energy through material hysteresis (internal friction), creating damping that slows cone response. SSS minimizes this damping, allowing the cone to start and stop more precisely in response to electrical input.
• Simplified Force Path: With only the surround providing restoring force and centering, the suspension geometry is mechanically simpler and more predictable, improving modeling accuracy and manufacturing consistency.

The practical result? When you play a snare drum strike through the XXM425, the cone accelerates instantly to reproduce the attack transient, then stops with equal precision as the signal decays. There's no "overhang" or mechanical resonance blurring the transient. Vocal sibilance (the "s" and "t" sounds in the 4-8 kHz range) is reproduced with clarity and definition that larger, heavier midranges struggle to achieve. Complex musical passages—fast bass lines, rapid piano arpeggios, layered vocal harmonies—are resolved as distinct events rather than blurred into undifferentiated midrange energy.

This is what Steve Head meant when he said the XXM425's tonality is "so natural and clearly delivered in such an effortless fashion." The driver isn't working hard to overcome its own mechanical limitations—it's simply tracking the input signal with accuracy that feels transparent.

Carbon/Glass Fiber Hybrid Cone — Years of Material Research

According to Xcelsus' official description, the XXM425 cone material was selected "after many samples"—a phrase that understates years of iterative material testing to find the optimal balance of stiffness, damping, and weight for a 4-inch competition midrange. The final choice is a carbon/glass fiber hybrid blend that combines the advantages of both materials while mitigating their individual weaknesses.

Carbon fiber offers exceptional stiffness-to-weight ratio—it's lighter than aluminum but significantly stiffer, allowing the cone to remain pistonic (moving as a rigid unit) well into the upper midrange before breakup modes emerge. High stiffness also means faster sound propagation through the material, reducing internal resonances that color tonality. The challenge with pure carbon fiber is that it can sound "cold" or "analytical" due to minimal internal damping—cone resonances, when they do occur, are lightly damped and can create audible peaks.

Glass fiber (fiberglass) provides better internal damping than carbon fiber—the fiber-to-fiber friction within the woven structure dissipates energy, smoothing out resonances. Glass fiber is also more cost-effective than carbon fiber while still offering good stiffness-to-weight ratios (comparable to aluminum). The trade-off is slightly higher weight than pure carbon fiber and somewhat lower ultimate stiffness.

The carbon/glass fiber hybrid blend in the XXM425 combines carbon fiber's low-mass, high-stiffness properties with glass fiber's superior damping characteristics. The result is a cone that remains rigid across the XXM425's 150 Hz to 10 kHz operating range, avoiding breakup modes within the passband, while naturally damping any resonances that do emerge beyond 10 kHz. Steve Head noted that the XXM425 was tested with both magnesium and carbon fiber cones during beta testing—the final carbon/glass blend was chosen as the optimal compromise for production.

This material choice directly contributes to the "natural tonality" that Steve Head praised. Vocals sound like vocals—not brightened, not muffled, not edgy. Instruments maintain their timbral character. The XXM425 doesn't impose a sonic signature on the source material; it reveals what's in the recording.

35mm Neodymium Motor — High-Energy Flux in a Compact Package

The XXM425's 35mm neodymium magnet motor is described by Xcelsus as "hi-energy," and the choice of neodymium over conventional ferrite is critical for achieving the XXM425's performance in a 4-inch format. Neodymium magnets deliver up to 20× the magnetic field strength per unit volume compared to ferrite, allowing dramatically smaller, lighter magnet structures to achieve equivalent motor force (Bl).

In a 4-inch midrange where installation depth is often limited (the XXM425 uses a "minimal depth" universal basket for factory location fitment), neodymium allows Xcelsus to create a powerful motor without the massive magnet stacks that ferrite would require. The 35mm neodymium magnet creates high flux density in the voice coil gap, generating the motor force needed to accelerate the cone rapidly despite the 60W RMS power handling. High motor force also improves damping factor—the driver's ability to control cone motion electrically, reducing overhang and improving transient accuracy.

Neodymium also contributes to overall driver efficiency. With stronger magnetic fields, less current is required to achieve a given output level, reducing thermal stress on the voice coil and improving power compression characteristics. The XXM425's 86 dB @ 1W/1m sensitivity is respectable for a 4-inch midrange—combined with 60W RMS power handling, you're looking at approximately 104 dB maximum output at 1 meter, more than sufficient for competition-level SPL in a properly designed 3-way system.

150 Hz to 10 kHz Frequency Response — Optimized for 3-Way Systems

The XXM425's 150 Hz to 10 kHz frequency response reveals its intended application: this is a dedicated midrange driver designed for 3-way active systems where a larger midbass handles 60-400 Hz and a tweeter covers 3-20 kHz. The XXM425 occupies the critical midrange band that includes:

• Vocal Fundamentals (150-400 Hz): Male vocal chest resonance, female vocal lower register, bass guitar fundamentals
• Vocal Presence (1-3 kHz): The "body" of vocals, where intelligibility and emotional connection are established
• Upper Midrange Detail (3-10 kHz): Vocal sibilance, cymbal attack, string instrument harmonics, piano upper register

This is the frequency range where human hearing is most sensitive (our ears evolved to prioritize human speech around 1-4 kHz) and where most musical information resides. Get the midrange wrong, and the entire system sounds disconnected or unnatural—even if bass and treble are perfect. The XXM425's design priorities—low moving mass, minimal mechanical damping, natural cone damping—are all optimized for accuracy in this critical range.

Steve Head described the XXM425's frequency extension as "stunning for a 'non-wideband' driver," suggesting that the upper rolloff beyond 10 kHz is smooth and well-behaved rather than abrupt. This matters for crossover design—a smooth rolloff allows flexibility in crossover point selection (typically 3-4 kHz with a tweeter) and reduces phase rotation that can degrade imaging. The 150 Hz lower limit allows crossover points with midbass in the 150-250 Hz region, keeping the XXM425's cone excursion within its linear range while allowing sufficient overlap for smooth response.

Universal 4" Basket — Factory Fitment and Minimal Depth

One of the XXM425's most practical advantages is its universal 4" die-cast aluminum basket designed for "minimal installation depth" and "ease of fitment into a variety of factory 4" locations." This isn't an accident—Xcelsus recognized that many enthusiasts want to upgrade factory speakers without custom fabrication or dashboard disassembly. The universal 4" format means the XXM425 can drop into factory door locations, dash positions, or A-pillar mounts that originally housed basic coaxials.

The die-cast aluminum basket provides several benefits beyond fitment. Aluminum is non-magnetic (important near the motor structure to avoid eddy current losses), rigid (reducing basket resonances that can color sound), and acts as a heat sink to dissipate thermal energy from the voice coil. The minimal depth design—achieved partly through the neodymium motor's compact size—allows installation in shallow mounting locations where larger midranges won't fit.

For competition installations where custom mounting is standard, the universal basket allows mounting in fiberglass or aluminum pods, kicks panels, or sail panel locations with straightforward fabrication. The 4" diameter strikes a balance—large enough to provide adequate radiating area for output down to 150 Hz, small enough to fit in locations that maintain optimal imaging and staging when crossed to a tweeter in the 3-4 kHz range.

Evolution from XXM325 to XXM425 — Scaling Up the Concept

The XXM425 didn't emerge in isolation—it's the 4-inch evolution of the XXM325, the 3-inch midrange that Steve Head had previously declared superior to the Scan Revelator 12M. Understanding this lineage helps explain why the XXM425 represents such refined engineering:

The XXM325 (3" version) established the core technologies: spiderless suspension for reduced Mms, carbon fiber cone for low-mass rigidity, neodymium motor for compact high-energy flux. It proved the concept—a small-format midrange could deliver reference-grade accuracy and dynamics by eliminating mechanical compromises (spider mass/damping) and optimizing materials for transient response. The XXM325's success in besting the Scan Revelator 12M—a driver with decades of refinement and widespread competition use—validated the approach.

The XXM425 (4" version) scales these technologies to a larger format, gaining several advantages:

• Increased Radiating Area: Moving from 3" to 4" diameter increases cone area by approximately 78% (assuming similar surround widths), allowing lower-frequency extension and higher output capability
• Lower Crossover Frequency: The 150 Hz lower limit allows crossover to midbass at 150-250 Hz rather than 250-400 Hz, keeping the XXM425 operating in a range where its small mass delivers maximum transient advantage
• Greater Power Handling: The larger voice coil (implied by 60W RMS rating vs. XXM325's 50W) provides more surface area for heat dissipation, improving thermal power handling
• Maintained Speed: Despite the larger size, the spiderless suspension keeps moving mass low enough that Steve Head still described the XXM425 as "lightning-fast"—the transient advantage wasn't lost in scaling up

Steve Head tested both the XXM325 and XXM425 extensively and concluded the XXM425 takes "the performance of the 325 up to several more notches"—not just different, but objectively better across dynamics, resolution, and tonal accuracy. This suggests that the larger 4" format was the optimal size for the spiderless suspension concept, balancing radiating area with moving mass to achieve maximum performance.

Dawid Koniarski's Legacy — 37 Years of Driver Design Expertise

While the XXM425 was developed after Dawid Koniarski's departure from Xcelsus' parent philosophy, it carries forward the driver design principles he established during 37 years as Chief Speaker Designer at DLS (1979-2016). Koniarski's approach—established through his 1983 invention of the automotive component speaker system and proven through IASCA/EMMA championships where DLS earned 35% of World Finals awards in 2004—prioritized linearity, low distortion, and natural tonality over marketing specifications.

The XXM425's design philosophy mirrors Koniarski's 1983 epiphany: "If coaxials were the ultimate solution, home HiFi would use them." Just as Koniarski recognized that separate drivers allow optimization for specific frequency ranges, the XXM425 is optimized exclusively for midrange reproduction (150 Hz-10 kHz) rather than compromising performance to cover a wider range. The spiderless suspension—eliminating a component that adds mass and nonlinearity—reflects Koniarski's approach of questioning conventional wisdom and removing elements that degrade performance.

When Steve Head says the XXM425 delivers "tonality so natural and clearly delivered in such an effortless fashion," he's describing the same quality that made DLS drivers legendary in European competition—drivers that didn't sound like "car speakers" with exaggerated peaks and resonances, but like accurate transducers that revealed the recording rather than imposing character. The XXM425 carries this legacy forward into Xcelsus' Competition Series.

Condition Notes — Previous Demo Unit

Recommended System Configuration — 3-Way Active for Maximum Performance

The XXM425 is explicitly designed for 3-way active systems—configurations where a DSP or active crossover separates frequencies electronically before amplification, allowing each driver to operate exclusively in its optimized range. Xcelsus states that the XXM425 is "most suited to be used as a midrange driver in a 3-Way set" paired with dedicated midbass and tweeter drivers.

Example Competition Configuration:

• Midbass (6.5-8"): Handles 60-250 Hz — Xcelsus XXM652 or similar high-excursion midbass
• Midrange (4"): XXM425 handles 200-3,500 Hz — Mounted in dash, A-pillar, or kick location for optimal imaging
• Tweeter (1-1.2"): Handles 3,000-20,000 Hz — Xcelsus XXT30 or XXT30W (waveguide version)
• Processing: DSP with active crossovers, time alignment, and EQ — Allows precise optimization of crossover slopes, phase relationships, and driver integration

This configuration allows each driver to operate in its strength zone. The midbass handles excursion-intensive low frequencies without compromising midrange clarity. The XXM425 operates in the critical 200 Hz-3.5 kHz vocal range where its low moving mass and spiderless suspension deliver maximum transient accuracy. The tweeter extends high-frequency response beyond where the XXM425's 4" cone begins beaming. The result, according to Steve Head, is a system that delivers "unparalleled realism & clear and dynamic sound that can capture the entire sound scene."

Who Should Buy the XXM425?

The Xcelsus XXM425 isn't a universal upgrade for every system—it's a specialized tool for specific applications and listeners who will appreciate what it offers:

Sound Quality Competitors: If you're building an IASCA, MECA, or EMMA competition vehicle where judges score vocal accuracy, imaging precision, and tonal balance, the XXM425's "lightning-fast" transient response and "natural tonality" are exactly what winning systems require. Steve Head's background in SQ competition gives his endorsement particular weight—he understands what separates good drivers from championship-caliber drivers.

Audiophile Installers: If you've worked with Scan Revelators, Dynaudio Esotan, or other reference midranges and are seeking something that delivers their accuracy with better dynamics and transient response, the XXM425 represents the current state-of-the-art in 4" midrange design. Steve Head's comparison to the Scan Revelator 12M isn't casual—he's directly claiming the XXM425 outperforms one of the most respected midranges in professional installation.

3-Way System Builders: If you're committed to active processing and understand that proper 3-way configuration requires DSP tuning, time alignment, and careful driver selection, the XXM425 is the midrange component that will elevate your system's midrange accuracy to reference levels. This isn't a driver you throw into a passive crossover—it's a driver you tune meticulously to extract its full potential.

Xcelsus Component Collectors: If you're building a complete Xcelsus Competition Series system (XXM652 midbass, XXM425 midrange, XXT30 tweeter), this demo unit represents an opportunity to acquire a critical component that may be difficult to source as Xcelsus' availability fluctuates. The spiderless suspension technology is unique to Xcelsus in the car audio market—you can't replicate this performance with conventional spiders.

Critical Listeners: If you listen to complex music—jazz with rapid instrumental interplay, classical with layered orchestration, vocals where you want to hear breathing and subtle inflections—the XXM425's resolution and transient accuracy reveal details that conventional midranges blur. You'll hear the difference immediately in A/B comparison.