The Pioneer HPM-100. For many audiophiles, the name itself conjures images of the golden age of hi-fi, the 1970s. These iconic speakers from Pioneer need little introduction, instantly recognizable for their robust build and bold sound. Often considered the last “true” speakers from Pioneer before mass consumerism heavily influenced design and pricing, the HPM-100s hold a special place in vintage audio history. Legend has it that Bart Locanthi, formerly head of engineering at JBL and the mastermind behind the legendary JBL L-100 Century, joined Pioneer in 1975 and spearheaded the HPM series to directly challenge JBL’s monitor dominance. And challenge they did, successfully capturing a significant market share, cementing their place in audio history.
There’s no denying the quality construction of these Pioneer Vintage Speakers. You feel it immediately when you attempt to lift them; at a substantial 26.7kg (almost 60lbs) each, your back is the first to register their heft. In an era when many Japanese speaker manufacturers were producing lighter, less substantial “paper” boxed designs, the HPM-100s stood out with remarkable craftsmanship on a mass production scale. It’s difficult to name another mass-produced speaker from that period that boasted a 50mm thick faceplate. The influence of JBL is palpable throughout the design of these speakers, a point we’ll revisit later when we examine driver similarities and crossover performance.
Restoration of a Neglected Classic: Bringing HPM-100s Back to Life
Despite their legendary status, even the most robust pioneer vintage speakers can fall victim to time and neglect. The pair featured in this article arrived in need of significant attention, brought in by a friend for restoration. While acquired at a favorable price, they had clearly seen better days. Unfortunately, no high-resolution “before” photos were captured, but the primary issues were immediately apparent:
- Cosmetics: A common plight for vintage speakers, the cabinets bore the scars of use as unintended furniture. Water rings and circular marks marred all surfaces, alongside scratches on the black faceplate.
- Damaged Mid-range Driver: Decades of use, or perhaps misuse, had taken their toll. The mid-range driver was trashed, a likely casualty of accidental damage.
- Crackling Sounds: Suspect number one was the bass units, exhibiting crackling noises, particularly at higher sound pressure levels. Further inspection revealed a tear in the woofer surround.
- Listening Fatigue: Perhaps the most subjective complaint, the owner reported headaches after extended listening sessions. While potentially humorous, it hinted at underlying sonic issues.
Initial listening confirmed the owner’s concerns. The sound was a mess, chaotic and unbalanced, certainly capable of inducing headaches. It was time for a more objective analysis, starting with acoustic measurements.
Unveiling the Sound: Initial Measurements and Polarity Problems
Before diving into subjective sound assessments, objective measurements are crucial, especially when diagnosing issues with pioneer vintage speakers. It’s important to preface this with a crucial caveat: measurements alone are not the definitive indicator of sound quality. They are tools, and like any tool, their value depends on context and interpretation. Over-reliance on graphs and numbers can be misleading. Measurements don’t reveal the subtleties of micro-details, transparency, soundstage depth, or the nuanced impact of component quality. However, for speaker analysis, measurements are invaluable for establishing a “clean bill of health.” They effectively highlight fundamental flaws: uneven frequency response, poor tonal balance, significant cancellations, distortion peaks, and driver integration problems. Without addressing these basic issues, subjective listening impressions become less meaningful.
With this in mind, the first SPL (Sound Pressure Level) measurements of these vintage marvels were taken.
dBSPL @1 Meter on Tweeter axis, 1/12 octave smoothing, 4ms gate window. Blue – right, red – left speaker. Both attenuators at 0dB.
The initial measurements were, frankly, alarming. The frequency response was far from flat and exhibited a deep cancellation around the crossover region. For anyone familiar with crossover design, this pattern immediately suggests a polarity issue. A common diagnostic technique involves reversing the polarity of one driver to assess driver integration at the crossover point. The depth of the resulting dip reveals the quality of this integration. The measurements clearly indicated that someone had indeed reversed the polarity of both mid-range drivers. But why?
It turns out, miswiring the mid-range drivers in HPM-100s is surprisingly easy. The wiring convention is somewhat counterintuitive: the white wire connects to the positive terminal on the mid-range, but to the negative terminals on both the tweeter and woofer. This unusual configuration makes accidental polarity reversal during reassembly quite likely. Correcting the mid-range polarity yielded the following measurements:
dBSPL @1 Meter on Tweeter axis, no smoothing, 4ms gate window. Blue – right, red – left speaker. Both attenuators at 0dB.
A significant improvement! The frequency response was now much smoother and more balanced. It’s astonishing to consider how long someone might have listened to these pioneer vintage speakers with reversed mid-range polarity, perhaps contributing to the decision to sell them. With the polarity corrected, the “headache-inducing” complaint was likely addressed. However, further irregularities remained, particularly around the woofer-mid crossover and in the high frequencies.
dBSPL @1 Meter. 1/12 octave smoothing. 4ms gate window. Tweeter axis. Mid attenuator at +3dB, High +2dB. Near field stitch @200Hz.
For comparison, here’s the frequency response curve published in a 1977 Pioneer HPM-100 promotional brochure:
From a 1977 US promotional brochure. No details provided.
The measured response, even with remaining issues, showed a reasonable resemblance to the factory published curve. It’s worth noting the extreme settings used for the attenuators (+3dB Mid, +2dB High) in the measurement; these settings would likely result in a very bright and fatiguing sound.
Addressing Driver Issues: Woofer and Mid-range Repairs
With the initial diagnosis complete, the focus shifted to addressing the specific driver problems.
The Whistling Woofer: Surround Repair
The crackling sound emanating from the woofer was indeed traced to a tear in the surround. This was compounded by another issue: an unpleasant whistling sound. Closer inspection revealed the cause. The textile surround of the woofer was heavily treated with a viscous damping compound, likely a phenolic resin-based material.
This treatment was intended to both seal the textile surround and damp its resonances. However, over decades, the viscous compound had migrated downwards, pooling at the bottom of the surround and stiffening it unevenly. This restricted cone movement in that area, eventually leading to the tear. Fortunately, the repair was relatively straightforward.
The first step was to carefully remove the excess damping compound. A hairdryer to soften the material and fine tweezers for removal proved effective. Care was taken to avoid further damaging the already delicate surround. Next, several thin coats of rubberized PVA adhesive, commonly sold as “speaker repair glue,” were applied to both seal the tear and restore some flexibility to the surround. While standard PVA glue could be used, its tendency to become rigid when fully cured makes it less ideal for surround repair, potentially reducing long-term durability.
The Mid-Range Crisis: Replacement Driver
The damaged mid-range driver presented a more significant challenge, both functionally and aesthetically.
While the dust cap could be replaced, the cone itself had suffered more extensive damage. Creases and wrinkles on one side indicated compromised cone rigidity and eccentricity. This distortion meant the voice coil was no longer optimally aligned within the magnetic gap, leading to potential rubbing and distortion, particularly at higher cone excursions.
A measurement comparison between the damaged driver and a functioning unit revealed some interesting results.
dbSPL@1m, 4ms window, good driver (red), damaged driver (blue).
Counterintuitively, the damaged driver’s frequency response (blue trace) appears smoother in the higher frequencies. This is because the damaged dust cap no longer contributes to high-frequency breakup modes in the 10-20kHz range. Additionally, the non-uniform cone rigidity actually suppresses breakup modes in the 5-10kHz range.
THD@1Vrms. Black – Total THD, Brown – Fundamental, Red – 2nd, Light Brown – 3d, rest – higher order harmonics.
However, Total Harmonic Distortion (THD) measurements tell a different story. The damaged driver exhibits significantly higher levels of higher-order harmonics in the critical 1-3kHz range. This distortion, while not immediately apparent in frequency response plots, would be clearly audible, negatively impacting sound quality. The distortion peak around 300Hz is the driver’s fundamental resonance frequency (fs), a normal characteristic.
A replacement was necessary. The hunt for a used Pioneer 10-721* mid-range driver commenced. Fortunately, the popularity of pioneer vintage speakers like the HPM-100 meant that used parts were available, albeit not always inexpensive. Eventually, a suitable used pair was sourced, resolving the “mid-range crisis.”
Cosmetic Revival: Walnut Veneer Makeover
With the drivers addressed, the final major hurdle was the speakers’ lackluster appearance. As the saying goes, “ugly speakers don’t sound good!” While subjective, aesthetics undeniably influence perceived sound quality. Listeners often “hear with their eyes,” and improving the visual appeal was deemed essential.
American dark walnut (left), Straight grain walnut (right).
Replacing the entire cabinet was considered impractical, making a fresh veneer application the most viable option. Walnut veneer was chosen for its classic appeal, but the sheer variety of walnut veneers available was surprising. After considering different options, a lighter, straight-grain walnut veneer was selected to provide a pleasing contrast with the black faceplate. The lighter veneer would also darken to a richer tone after applying a semi-matte lacquer.
While detailed photos of the veneering process weren’t captured, the technique itself is well-established. Oversized veneer pieces were cut, and the process for corner over-cuts planned. Pattern orientation was carefully considered for a cohesive look. PVA wood glue was applied to both the veneer and cabinet surfaces, allowed to partially cure, and then the veneer was bonded to the cabinet using a household iron heated to approximately 200°C. The heat from the iron activates the glue, creating a strong bond. Practicing on scrap material beforehand is recommended for those unfamiliar with veneering.
Corner trimming is the trickiest part. A sharp utility knife with high-quality blades is essential. The final over-cut should slightly overhang the edge, and then finished flush with sanding paper. The resulting bond is incredibly strong, requiring significant force to remove the veneer, often taking a layer of MDF with it.
The veneering process yielded clean, sharp corners. Three coats of TIKKURILA Paneeli–Ässä water-based semi-matte lacquer were applied to the new veneer, enhancing the wood grain and providing protection. Finally, the front baffle received a fresh coat of matte black spray paint, completing the cosmetic transformation. The speakers were beginning to look as good as new.
Box Design Analysis: Understanding Bass Performance
Speaker box design and room placement are critical factors influencing bass performance. While in-room speaker behavior is a complex topic deserving separate exploration, simulating the HPM-100’s box design provides valuable insights into its expected bass response.
Pioneer 30-733A-1 woofer TS parameters.
Thiele/Small (TS) parameters for the Pioneer 30-733A-1 woofer were calculated using the added mass method. These parameters were then input into LspCAD, a speaker design software, to simulate the box performance.
Half space (2Pi) SPL at 1m distance.
The simulation predicted a 3dB bass peak at 65Hz in the factory 68-liter cabinet. This was confirmed by near-field measurements and is even discernible in the original promotional brochure’s frequency response curve. This bass emphasis has significant implications for room placement. Placing HPM-100s in room corners will exaggerate this peak due to room gain, potentially resulting in an overly boomy and unbalanced bass response. Ideally, these pioneer vintage speakers should be positioned on stands, at least 50cm (20 inches) from the floor and away from room corners, to allow for proper bass reproduction. Additional damping material inside the cabinet can also help to tame the bass peak, as can experimenting with foam inserts in the ports.
Beyond the bass tuning, the HPM-100 cabinet is impressively constructed for a mass-produced speaker, particularly the substantial faceplate, contributing to its solid and inert character.
Crossover Examination: JBL Influence or Design Flaw?
One of the initial observations about the HPM-100 was the potential JBL influence, particularly given Bart Locanthi’s background. This influence becomes strikingly apparent when comparing the HPM-100’s crossover network to that of the JBL L100 Century.
HPM-100 original cross-over (left), JBL L100 century original cross-over (right).
The simplicity of both designs is notable, a characteristic often found when manufacturers design their own drivers. Pioneer deviated slightly from the L100’s design by incorporating a first-order (6dB/octave) low-pass filter on the woofer using a 0.6mH inductor, while the L100 woofer runs unfiltered. However, Pioneer mirrored JBL’s approach by using only a capacitor (first-order high-pass) for the mid-range. Both speakers employ a second-order (12dB/octave) high-pass filter on the tweeter. Such minimalist crossover networks raise questions about driver integration and overall sonic coherence, especially in a three-way design.
Woofers: Pioneer 30-733D (left), JBL 123A (right). Tweeters: Pioneer 45-711C (left), JBL LE25-2 (right).
The similarities extend to the drivers themselves. Comparing the HPM-100 drivers to their JBL counterparts reveals striking resemblances, suggesting more than just coincidence. Direct measurement comparisons between these drivers would be insightful but are beyond the scope of this restoration project.
Mid-range: Pioneer 10-721A (left), JBL LE5-2 Alnico (center), JBL LE5-12 (right)
The mid-range drivers show some divergence. The original L100 Century used the highly regarded JBL LE5-2 with an Alnico magnet and more robust construction than the Pioneer 10-721A. The JBL LE5-12, a later, more cost-effective version of the LE5-2 with a ceramic magnet, appears to be the closer inspiration for the Pioneer mid-range.
Measuring the performance of the original HPM-100 crossover reveals its sonic shortcomings.
dBSPL@1m, 4ms window, no smoothing. Black – total, Green – woofer, Red – midrange, Blue – tweeter. Attenuators +0dB.
The frequency response with the stock crossover is far from ideal, particularly in the crucial 1-3kHz region where driver integration is poor. The super-tweeter, a prominent feature of the HPM-100, contributes minimally to the overall sound. Its output is significantly lower (around 10dB) and out of phase with the other drivers. It begins to produce some output above 12kHz, but its contribution is sonically negligible, leading to the decision to disconnect it entirely for this restoration.
dBSPL@1m, Tweeter axis, 4ms window, no smoothing. Green – woofer, Red – midrange, Blue – tweeter.
Examining the individual driver responses reveals the challenges facing the crossover design. The woofer’s roll-off is uneven and exhibits breakup modes around 5kHz. The tweeter struggles to reach down to 4kHz, while the mid-range driver performs relatively well within its intended band.
Simulation of the original crossover network in LspCAD further illuminates its design limitations.
HPM-100 original cross-over filter.
The original front panel attenuators were modeled in the simulation using passive resistors to match the measured SPL at the “0”dB settings.
dBSPL and Phases @1Meter. Blue – woofer, Red – midrange, Green – tweeter.
Initial simulations did not align with measured frequency responses. Further investigation revealed another potential polarity issue: the tweeter. Pioneer, inexplicably, did not mark polarity on the tweeter terminals.
Impulse responses of inverted (green) and correctly connected (blue) tweeter.
By measuring individual driver impulse responses and importing them into LspCAD with corrected polarity, a more accurate simulation was achieved. However, when simulating the original crossover circuit, the results still didn’t match the measured response unless the tweeter polarity was also inverted.
dBSPL and Phases @1Meter. Inverted tweeter. Blue – woofer, Red – midrange, Green – tweeter.
With both the mid-range and tweeter polarities inverted in the simulation, the predicted frequency response closely matched the measured response of the original crossover. This raised a perplexing question: how could these pioneer vintage speakers have left the factory with such fundamental polarity errors?
The HPM-100 wiring diagram indicates that the positive tweeter terminal (red wire) becomes white and connects to the negative terminal on the crossover board. Similarly, the green wire from the positive mid-range terminal also connects to the negative terminal on the crossover board. This suggests that both the mid-range and tweeter are indeed wired with inverted polarity from the factory, contradicting the service manual schematic which shows all drivers in phase.
Further evidence emerged from a reader who provided a schematic of their original HPM-100 units, clearly indicating factory-inverted polarity for both the mid-range and tweeter drivers. This confirmed that the initial SPL measurements, showing phase cancellation due to inverted mid-range polarity, were indeed accurate, and that the service manual schematic was incorrect.
Analyzing the simulated frequency response with both correct and inverted tweeter polarity reveals the inherent compromises in the original crossover design.
dBSPL@1Meter. Inverted & correct tweeter. Blue – woofer, Red – midrange, Green – tweeter.
Regardless of tweeter polarity, the mid-range driver attempts to operate as a full-range driver, overlapping significantly with the tweeter’s frequency range. This creates interference and cancellations. To compensate for these issues and smooth out the overall response, the woofer is forced to extend its response up to 3kHz, far beyond its optimal operating range.
Phase@1Meter. Inverted&correct tweeter. Blue – woofer, Red – midrange, Green – tweeter.
Phase response plots further illustrate the lack of driver coherence. Regardless of tweeter polarity, the drivers operate largely independently, with poor phase tracking, contributing to the sonic shortcomings of the original HPM-100 crossover.
Listening to the Original: Initial Sound Impressions
Before any measurements were taken, an initial listening session was conducted after replacing the damaged mid-range driver and correcting its polarity. The initial impression was underwhelming. Despite the corrected polarity, the sound remained problematic, prompting a deeper investigation into the crossover’s performance.
After fully analyzing the original crossover and confirming the factory driver polarities, a second listening session was conducted with the speakers wired as they came from the factory. The sonic issues remained, allowing for a more precise identification of the strengths and weaknesses of the original HPM-100 sound.
On the positive side, the HPM-100s possess a dynamic and lively character. Running the mid-range with only a capacitor contributes to a sense of immediacy and “sparkle” often associated with full-range drivers. The LE25-clone tweeter, despite its measured limitations, performs surprisingly well in the upper treble, sounding smooth without harshness. The 12-inch woofer, extending into the lower midrange and treble, contributes a unique sonic signature that must be experienced to fully appreciate. Bass is plentiful and, with proper room placement, avoids excessive boominess. The overall presentation is engaging and fun, creating an initial “wow” factor that draws listeners in.
However, prolonged listening reveals significant shortcomings. The soundstage is flat and two-dimensional, lacking depth and instrument separation. The sonic image is cluttered and lacks focus. Classical music, in particular, suffers, sounding distorted and lacking refinement. No matter how the front panel attenuators are adjusted, a proper mid-high frequency balance is elusive. The sound remains perpetually “loudness-enhanced,” lacking subtlety and nuance. Vocals, critically, simply don’t sound natural.
In summary, the original HPM-100 is well-suited for parties and casual background listening, but falls short for critical listening and accurate sound reproduction.
The New Crossover Design: Unleashing the Drivers’ Potential
Despite the shortcomings of the original crossover, the quality of the individual drivers in the HPM-100 is undeniable. These drivers possess the potential for significantly better performance with a properly designed crossover network – one engineered for sonic accuracy and driver integration, rather than solely for sales appeal.
Considerable time and effort were invested in designing a new crossover network for the HPM-100. Through extensive simulations and listening tests, the following design emerged as a significant improvement over the original.
2024 Update: Based on user feedback from builders who have implemented this crossover design, the mid-range capacitor value has been updated from 4.7uF to 3.9uF. While direct evaluation was not possible, this modification reflects a generally preferred voicing. As noted below, mid-range level can be further adjusted using resistor R2011.
New HPM-100 cross-over network (v1.2).
For builders unfamiliar with crossover schematics, a simplified connection diagram is provided. A spreadsheet with a bill of materials, including links to parts-express for component ordering, is available for download here.
Connection diagram for new HPM-100 cross-over network (v1.2).
The new design retains a first-order low-pass filter on the woofer, but incorporates impedance correction to improve phase tracking with the mid-range driver. This maintains the original design intent of allowing the woofer to contribute to the midrange and lower treble. The mid-range still utilizes a capacitor for high-pass filtering, but now includes a second-order low-pass filter for better integration with the tweeter. An RCL network is added to the mid-range circuit to further optimize phase tracking with the tweeter, which employs a simple second-order high-pass filter. While a more complex tweeter circuit could further flatten the high-frequency response, sonic testing indicated that the simple second-order filter was sufficient.
R3021 and R2011 influence for new HPM-100 cross-over network.
The overall voicing of the new crossover leans slightly towards the bright side. Resistor R3021 can be increased to tailor the high-frequency balance to personal preference. Similarly, the mid-range level can be further attenuated by increasing resistor R2011 to 14, 16, or even 18Ω. All inductors, except L1101, should be air-core types with resistance values no higher than specified. High-quality polypropylene (PP) capacitors are recommended for all positions, with Jantzen Standard Z-Caps (or equivalent) being a good compromise between performance and cost. C1021 can be a Jantzen Cross-Cap to further optimize cost.
dBSPL@1Meter. Blue – woofer, Red – midrange, Green – tweeter.
The simulated frequency response of the new crossover shows significant improvements. Driver integration is much smoother, with no major cancellations. The woofer now exhibits a controlled second-order roll-off from a 1kHz crossover frequency, effectively addressing its 5kHz breakup issues. The mid-range driver operates within its optimal range, no longer attempting to reproduce high frequencies. The tweeter is crossed over at a sensible 4kHz with a second-order slope.
Phase@2Meters. Blue – woofer, Red – midrange, Green – tweeter.
Crucially, the phase response shows significantly improved phase coherence across almost the entire audible spectrum. Phase coherence is paramount for accurate sound reproduction, and its improvement is a key benefit of the new crossover design. The design aims for optimal phase coherence at a typical listening distance of 2 meters, rather than the standard 1-meter measurement distance, a subtle but potentially audible refinement.
Speaker impedance – 5Ω minimum.
The impedance curve of the new crossover maintains a minimum impedance of 5Ω, similar to the original design. This ensures compatibility with a wide range of amplifiers, including low-power single-ended tube amplifiers.
Measured dBSPL @1Meter. 1/12 octave smoothing. 4ms gate window. Tweeter axis.
Measured frequency response of the HPM-100 with the new crossover closely matches the simulated response, validating the design. The slight hump around 1kHz in the measured response was attributed to using a 1mH inductor instead of the specified 1.2mH for the woofer during the measurement. With the correct 1.2mH inductor, this slight deviation is eliminated.
Update: For those wishing to retain the original front panel attenuators, the new crossover design can be adapted with minor modifications:
*However, it is strongly recommended to bypass the original attenuators unless they are in pristine condition or replaced with new, high-quality potentiometers. The use of 45-year-old, potentially crackling potentiometers in the signal path negates many of the benefits of upgrading to higher-quality crossover components.
New HPM-100 cross-over network with original passive attenuators.
Minor adjustments to capacitor C2011 and resistor R3021 are needed to provide sufficient adjustment range with the attenuators. The minimum impedance remains above 4Ω even at the highest attenuation settings. It’s important to note that the original front panel markings will no longer accurately reflect the actual frequency balance with the new crossover. The attenuators, being approximately 30Ω (despite being marked as 8Ω), provide a wide adjustment range, potentially making precise tonal balance challenging to achieve. However, for listeners who enjoy experimenting with different tonal settings, this option retains the original control functionality.
Connection diagram for new HPM-100 cross-over network with original passive attenuators.
Listening to the Upgraded HPM-100: A Transformation
The HPM-100, with the new crossover, is fundamentally transformed. It is no longer the same speaker. Listeners accustomed to the exaggerated, “in-your-face” sound of the original HPM-100 may initially be surprised, even disappointed. However, this transformation is a significant improvement in sonic accuracy and refinement.
A week-long listening session with the new crossover, even built with modest components (standard PP capacitors and cored inductors), revealed a dramatic improvement. Despite using only prototype-grade components, the sound quality was captivating.
Classical music now unfolds with a believable three-dimensional soundstage, instruments occupying distinct positions within the sonic space. Imaging and instrument separation are vastly improved. The lively and dynamic character of the original HPM-100 is retained, but now with greater subtlety and control. The harshness and sibilance of the original are gone, replaced by a smoother, more balanced presentation. Vocals sound natural and lifelike, a critical improvement.
The upgraded HPM-100 now performs exceptionally well across a wide range of musical genres. While it may not sound like a “modern” speaker in the strictest sense, all the previously identified sonic flaws have been effectively addressed. The sound is realistic and engaging, making it difficult to find fault. Further improvements can be realized by using higher-grade crossover components, such as premium capacitors and air-core inductors.
Back to Stock: The Owner’s Decision and Final Touches
Ultimately, despite the demonstrable sonic improvements offered by the new crossover, the owner opted to revert to the original crossover design. This decision was driven by two primary factors: a desire to preserve the speakers’ resale value and the owner’s inability to personally audition the new crossover before making a final decision. Having initially considered selling the speakers after hearing their improved performance, the resale value consideration became paramount.
Factory HPM-100 cross-over network remade with quality parts.
To ensure the best possible performance from the original design, the original crossover networks were rebuilt using higher-quality components, mirroring the original schematic but with modern capacitors and resistors. The drivers were rewired using appropriately gauged speaker cable, and new gold-plated binding posts were installed, providing a final touch of refinement. The restored pioneer vintage speakers, now visually and sonically refreshed (albeit with the original crossover), were returned to their owner.
Last Thoughts
This restoration project was a personally rewarding journey, fulfilling a long-held desire to experience the iconic HPM-100 pioneer vintage speakers. It served as a reminder that childhood dreams sometimes require tempered expectations.
Throughout the project, the perception of the HPM-100 as a JBL L100 “clone” persisted. While neither speaker is sonically perfect, the HPM-100, in its original form, falls short of its potential. A brief listening session with original JBL L100s revealed similar sonic limitations. However, the JBLs possess a certain “realness” and “pro-audio” character that is undeniably appealing.
In their stock configuration, the HPM-100s, while not terrible, are not a personal preference for serious listening. However, with the new crossover, these pioneer vintage speakers are transformed into something truly special, capable of delivering a refined and engaging listening experience. While “buy and upgrade” audiophilia is no longer the primary focus, the potential of these vintage drivers, when properly harnessed, is undeniable. For those seeking to unlock the hidden potential of their Pioneer HPM-100s, the new crossover design offers a transformative upgrade.
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