Review: Progressive Audio Extreme I – Compact Speakers

Review: Progressive Audio Extreme I - Compact Speakers- The Extreme I has therefore become a fully-fledged progressive audio speaker – at a price of around 4,000 euros.


For those familiar with Progressive Audio, it’s no secret that their audio equipment typically commands a premium price. Renowned for their amplifiers, DACs, and speakers that deliver exceptional sound quality but often dwell in the five-digit price range, the question arises: can Progressive Audio replicate their sonic ideals in a more affordable package? Enter the compact Progressive Audio Extreme I, available as a pair for 4,400 euros. In our review, we discovered that even in this more budget-friendly offering, the Extreme I manages to transport listeners into a magnificent realm of sound.

Technical data

Progressive Audio Extreme I
Concept:2-Wege Coax-Compactbox, Bassreflex
Diameter of bass-midrange driver:16 centimeters
Tweeter diameter:25 millimeters (fabric)
Efficiency (2.83 volts / 1 meter):86,0 dB
Nominal impedance3,7 Ohm
Maximum level (duration / short-term)92 / 103 decibels
Power requirement for max. level22,4 Watt
Special feature:Acrylic case (white and black)
Dimensions (W x H x D):19,0 x 40,0 x 35,0 cm
Weight:11,5 Kilo

A Legacy of Sonic Brilliance

My memories of Progressive Audio’s impressive system with their Transformer speakers still linger, and a recent visit to their setup left a deep impression. A friend who recently experienced the Progressive sound in Essen-Kettwich couldn’t help but be moved by it. He remarked, “It sounds so plastic-spatial that your mouth will stay open.” I share his sentiment, particularly in terms of the system’s three-dimensionality and perceived speed—two characteristics that the Progressive systems excel in.

Ralf Koenen: The Engineer Behind the Magic

Central to Progressive Audio’s philosophy are time and phase accuracy, qualities that Ralf Koenen, the company’s founder, consistently prioritizes. Unlike many hi-fi enthusiasts, Koenen is a graduate engineer in communications engineering, bringing a unique perspective to circuit technology in hi-fi, including speaker design. One look at the crossover in the Extreme I, and it’s clear that Koenen pays meticulous attention to detail. Instead of focusing on overall impedance linearization, which can sometimes sacrifice dynamism, Koenen employs multiple individual filters to achieve his vision of phase linearity, resulting in an extensive component count for a seemingly “simple” 2-way speaker.

Innovative Design and Material Choices

Two standout features define the Extreme I compact speaker: its acrylic construction and the coaxial driver from Norwegian specialist Seas. The cabinets are constructed from 10mm thick acrylic panels, meticulously bonded together over seven hours with a two-component adhesive to create a rigid, vibration-resistant structure. Koenen’s choice of acrylic is motivated by its higher attenuation in the low-frequency range. The coaxial driver, consisting of a 16cm magnesium membrane and a 25mm fabric dome, is a proven design that Koenen further refines by collaborating with Seas to develop a variant with an impressive linear stroke of 14mm for a woofer of this size. This design ensures excellent bass capability, uniform radiation in all directions, and, in line with Koenen’s principles, simultaneous reproduction of high and low-mid frequencies through precise alignment of the voice coils.

The Progressive Audio Extreme I not only impresses with its sonic prowess but also makes a statement through its design and build quality. In this section, we delve into the intricate details of its aesthetics and the robust construction that underpins its performance.

  • Acrylic Elegance: The Extreme I’s design is a head-turner. Constructed from 10mm thick acrylic panels, each speaker exudes a modern, minimalist elegance that catches the eye. The use of acrylic is not merely for aesthetics; it serves functional purposes. Acrylic’s inherent stiffness and stability make it an ideal choice for speaker construction. These panels are meticulously bonded together with a two-component adhesive over an extended period of seven hours, resulting in a rigid and vibration-resistant enclosure. This not only enhances the speaker’s durability but also plays a role in mitigating unwanted resonance, ensuring that the sound remains uncolored and true to the source.
  • Innovative Driver Configuration: The Extreme I features a coaxial driver configuration, a testament to Progressive Audio’s commitment to engineering excellence. This design comprises a 16cm magnesium membrane woofer and a 25mm fabric dome tweeter arranged coaxially. The woofer’s linear stroke of 14mm, exceptional for a driver of this size, promises deep and impactful bass performance. The coaxial alignment ensures uniform sound dispersion in all directions, eliminating phase-related anomalies and providing a cohesive, time-accurate soundstage. This meticulous driver choice and arrangement are at the core of the speaker’s sonic brilliance.
  • Meticulous Crossover: A pivotal element in the Extreme I’s design is its complex crossover network. While many speakers seek impedance linearization through a single crossover element, the Extreme I takes a different approach. Ralf Koenen, the mind behind Progressive Audio, employs multiple individual filters to achieve phase linearity and sonic coherence. The result is an intricate crossover with a multitude of components, meticulously fine-tuned to ensure that every frequency is reproduced with utmost accuracy. This level of detail in crossover design sets the Extreme I apart and contributes significantly to its exceptional sound quality.
  • Attention to Detail: Beyond the technical aspects, the Extreme I showcases a keen attention to detail. Even the small touches matter. Furutech connectors adorn the speaker’s rear, exemplifying quality in every aspect of its construction. These connectors not only provide reliable electrical connections but also reflect a commitment to using top-tier components.

In summary, the Progressive Audio Extreme I marries aesthetic brilliance with uncompromising durability. Its acrylic construction, innovative driver configuration, meticulous crossover design, and attention to detail are all indicative of a speaker that aspires to be a masterpiece in both form and function. Whether as a visual centerpiece in a room or as a sonic powerhouse in a hi-fi setup, the Extreme I’s design and build quality leave an indelible impression of craftsmanship and excellence.

A Crossover Like No Other

One of the most remarkable aspects of the Extreme I is its sophisticated crossover, meticulously designed by Koenen to achieve phase linearity. While you won’t find an impedance linearization across the board, the careful attention to phase coherence is evident in the complexity of the crossover, which houses a wealth of components to accomplish this task. Electrical behavior-wise, the Extreme I impresses with its nearly ideal efficiency and impedance/phase behavior, making it suitable for low-wattage tube amplifiers. However, it’s worth noting that while it excels in many aspects, the Extreme I is not a high-volume speaker due to its size.

Sonic Wonders: Listening to the Extreme IAn Astonishing Listening Experience

In terms of sound, the Extreme I defies expectations. Its deep bass, though rich rather than strictly precise, contributes to a warm and expansive listening experience. A slight dip in the upper bass enhances clarity in vocals and ensures an immaculate midrange. The speaker’s coordination and complex filtering shine in the midrange, delivering a tonally accurate and well-organized presentation.

During listening tests, the Extreme I astounded with its clarity, three-dimensionality, and spatial depth. It projected music with unparalleled precision, allowing listeners to feel as though they could touch every facet of the sound, from the snare and bass drum to the guitar and piano. While not a high-volume speaker due to its size, it provides a remarkably large and confident soundstage.

Sound Test and Sound Quality: A Sonic Journey Beyond Expectations

The heart of any audio equipment lies in its ability to deliver exceptional sound quality, and the Progressive Audio Extreme I excels in this aspect. In this section, we embark on a sonic journey, exploring the nuances of its sound test and dissecting the mesmerizing sound quality it offers.

  • Deep, Resonant Bass: The Extreme I introduces you to a world of deep and resonant bass that defies expectations for a compact speaker. While the bass may lean more towards richness than surgical precision, it contributes to an immersive and captivating listening experience. This characteristic warmth adds a sense of grandeur to the music, making it sound larger than life.
  • Clarity in Vocal and Midrange Brilliance: One standout feature of the Extreme I is its ability to render vocals with crystal-clear clarity. In the midrange, it exhibits a remarkable sense of order and precision. This clarity and meticulous attention to detail in the midrange make for a truly captivating listening experience. Even the most intricate musical passages and vocal nuances are faithfully reproduced, allowing listeners to immerse themselves in the music with unparalleled engagement.
  • Exceptional Imaging and Spatial Depth: During our sound tests, the Extreme I consistently impressed with its ability to create an expansive soundstage that transcends the physical boundaries of the room. The imaging is exceptional, allowing each instrument and vocal to occupy its distinct space within the sonic landscape. Whether you’re enjoying a symphonic masterpiece or an intimate jazz quartet, the Extreme I’s spatial depth adds a layer of realism and immersion that few compact speakers can match.
  • Coherent and Balanced Presentation: What sets the Extreme I apart is its coherence and balance throughout the frequency spectrum. The meticulous crossover design ensures that each frequency seamlessly transitions to the next, resulting in a sound profile that feels unified and harmonious. There are no jarring transitions or frequency spikes; instead, you’re treated to a well-integrated sonic experience that does justice to all genres of music.
  • Sensitivity to Electronics: The Extreme I’s efficiency, along with its impeccable impedance and phase behavior, makes it highly compatible with a range of amplifiers. Even low-wattage tube amplifiers can bring out the best in this speaker. This versatility allows audiophiles to tailor their system to their preferences, whether they prefer the warmth of tubes or the precision of solid-state amplification.
  • Comparison with High-End Peers: When compared with other compact high-end speakers, the Extreme I holds its own with flying colors. Its ability to conjure a captivatingly deep soundstage, offer exceptional clarity, and maintain coherence across frequencies sets it in a league of its own. While other speakers may excel in specific areas, the Extreme I’s overall balance and engagement make it a standout performer.

In summary, the sound test of the Progressive Audio Extreme I left us in awe of its sound quality. It delivers a sonic journey that transcends its size and price point. From deep, resonant bass to crystal-clear vocals, exceptional imaging, and a coherent presentation, this speaker consistently impresses. Its sensitivity to electronics ensures compatibility with various amplifiers, adding versatility to its sonic repertoire. Whether you’re a seasoned audiophile or a music enthusiast seeking an immersive listening experience, the Extreme I’s sound quality will undoubtedly exceed your expectations. It’s a testament to Progressive Audio’s commitment to delivering sonic excellence in a compact package.

Comparison with the Best

Comparing it to the XT-1 from Raidho, another compact speaker known for its impressive deep bass and expansive soundstage, the Extreme I manages to take things a step further. Its ability to create a captivatingly deep soundstage with exceptional clarity and coherence is a testament to its engineering prowess.


In conclusion, the Progressive Audio Extreme I stands as an exemplary testament to what can be achieved in the realm of compact speakers without breaking the bank. With its innovative design, meticulous engineering, and a commitment to phase and time accuracy, the Extreme I delivers a listening experience that belies its price point.

During our evaluation, this speaker consistently astounded with its ability to conjure a three-dimensional soundstage, offering exceptional clarity, detail, and spatial depth. While not a high-volume speaker due to its compact size, it provides an immersive and engaging sonic experience that’s sure to delight music enthusiasts.

In the world of compact high-end speakers, the Extreme I distinguishes itself with its unique blend of precision, liveliness, and versatility. Whether paired with low-wattage tube amplifiers or high-end electronics, it excels in faithfully reproducing music with depth and finesse. While its acrylic design may be polarizing, its electrical performance is impeccable, making it a worthy addition to any audiophile’s setup.

For those seeking affordable excellence in the world of hi-fi audio, the Progressive Audio Extreme I is a compelling choice that opens the door to a captivating musical journey.

Advantages of the Progressive Audio Extreme I:

  1. Exceptional Sound Quality: The Extreme I delivers outstanding sound quality with deep, resonant bass, crystal-clear vocals, and a well-balanced presentation. It excels in reproducing music with clarity and precision.
  2. Innovative Design: The use of 10mm thick acrylic panels and a coaxial driver configuration not only adds to the speaker’s aesthetic appeal but also contributes to its acoustic performance. Acrylic provides durability and vibration resistance, while the coaxial driver ensures uniform sound dispersion and accurate phase coherence.
  3. Immersive Soundstage: This speaker creates an expansive soundstage with exceptional imaging and spatial depth. It immerses listeners in a realistic and engaging sonic environment, making it ideal for critical listening and audiophile experiences.
  4. Versatility with Amplifiers: The Extreme I’s efficiency and compatibility with a wide range of amplifiers, including low-wattage tube amps, make it adaptable to different audio setups. It provides the flexibility to tailor the sound to personal preferences.
  5. Meticulous Crossover Design: The complex crossover network, with numerous components, ensures phase linearity and a cohesive sonic performance. It reflects a commitment to precision and contributes to the speaker’s exceptional sound quality.

Disadvantages of the Progressive Audio Extreme I:

  1. Limited Volume: Due to its compact size, the Extreme I is not a high-volume speaker. While it excels in many aspects, it may not be suitable for those seeking extremely high sound levels for large rooms or parties.
  2. Acrylic Design May Be Polarizing: While the acrylic construction is visually striking and functional, some users may find it polarizing in terms of aesthetics. Personal preferences for speaker materials vary, and acrylic may not appeal to everyone.
  3. Premium Price: The Extreme I, while delivering exceptional performance, comes with a premium price tag. It may not be within the budget of all potential buyers, limiting its accessibility.
  4. Complex Crossover: The elaborate crossover design, while contributing to sound quality, results in a higher component count. This complexity may pose challenges for maintenance or repairs in the long term.
  5. Size Limitations: Although the Extreme I offers remarkable sound quality for its size, its compact form factor inherently imposes limitations on low-frequency extension and absolute volume levels. For those seeking deep bass and room-filling sound, larger speakers may be necessary.

In summary, the Progressive Audio Extreme I offers remarkable sound quality, innovative design, and versatility with amplifiers. However, it comes with limitations such as limited volume, potential aesthetic preferences, and a premium price. Its complex crossover design and size considerations are factors to consider when evaluating this speaker for a specific audio setup.


  • Model: Progressive Audio Extreme I
  • Concept: passive, two-way coaxial speaker, bass reflex
  • Price: 3,998 euros
  • Dimensions: 400x 190xx350mm cm (HxWxD)
  • Colors: Black, White
  • Other: Furutech connection terminal, mono wiring, toggle switch to increase the treble by 1 dB
  • Warranty: 2 years