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History Of The Legendary AKG BX-20 Spring Reverberator.

The AKG BX 20 is a classic spring reverb unit that has left a lasting mark on the world of audio recording. Here’s a brief history of the AKG BX 20 spring reverberation device:

1. Introduction (1965): The AKG BX 20 was introduced in 1965 by AKG Acoustics, an Austrian company known for its high-quality audio equipment. It was designed as a spring reverb unit, a technology that was widely used during the era for adding reverb and ambience to audio recordings.

2. Spring Reverb Technology: Spring reverb units create reverberation effects by sending an audio signal through a set of suspended metal springs. These springs vibrate, and the resulting reflections are picked up by transducers and blended with the dry signal. The characteristics of the springs and the design of the unit influence the sound of the reverb.

3. Sound Quality and Character: The AKG BX 20 quickly gained popularity for its warm, smooth, and natural reverb sound. It was known for its distinctive character, which made it a preferred choice for many recording engineers and artists. The spring reverb sound could add a unique ambience to various instruments, especially guitars and vocals.

4. Dual-Tank Design: One of the unique features of the AKG BX 20 was its dual-spring tank design. It consisted of two separate sets of springs with different characteristics, allowing users to create a wide range of reverb sounds, from short and bright to long and lush. This dual-tank design contributed to the versatility of the BX 20.

5. Use in Classic Recordings: The AKG BX 20 was used in numerous classic recordings across various music genres. Its distinctive sound can be heard in the music of artists such as The Rolling Stones, Pink Floyd, Led Zeppelin, and many more. It played a role in creating the signature reverb sound on many iconic tracks.

6. Challenges of Spring Reverb: While spring reverb units like the AKG BX 20 offered a unique and desirable sound, they had some limitations. They were relatively bulky and required careful maintenance to ensure consistent performance. Their sound also had a signature coloration that might not be suitable for all musical styles.

7. Legacy and Collectibility: The AKG BX 20 spring reverb has left a lasting legacy in the world of audio recording. Vintage units have become collector’s items, sought after by audio enthusiasts and studios for their unique sound and historical significance.

8. Contemporary Emulations: In the digital age, software and hardware emulations of the AKG BX 20 have been developed to capture its distinctive sound. These emulations aim to replicate the spring reverb’s character while providing the convenience and reliability of modern technology.

The AKG BX 20 spring reverberation device remains an iconic piece of equipment that represents a specific era in audio recording technology. Its timeless sound and influence continue to be celebrated, ensuring its place in the history of audio recording.


Review Of The AKG BX-20 Spring Reverberator.

It was with mixed feelings that I decided to part ways with my AKG BX 20 spring reverb unit. This classic piece of audio equipment had been a treasured part of my studio setup for years, but its size and the demands it placed on my limited studio space eventually led me to make the difficult decision to sell it.

The AKG BX 20 is known for its warm and character-rich reverb sound, and it had served me well on countless recordings. Its dual-tank design allowed for an impressive range of reverb options, from short and snappy to long and lush. The sound it produced was distinctive, with a touch of vintage charm that made it suitable for a wide range of musical styles.

However, its sheer physical presence was undeniable. The BX 20 was a large and bulky unit, taking up a significant portion of my studio real estate. As much as I appreciated its sonic qualities, the practical constraints of my workspace couldn’t be ignored. I found myself needing to free up space for other equipment and workflow improvements.

Selling the AKG BX 20 was not without a pang of nostalgia. I had grown attached to its unique sound and the character it brought to my recordings. There was a sense of history and authenticity that came with using a classic spring reverb. But ultimately, the need for more efficient use of my studio space prevailed.

As I packed it up for its new home, I couldn’t help but reflect on the recordings it had been a part of and the music it had enhanced. While it might no longer reside in my studio, I knew that its legacy would live on in the hands of another audio enthusiast who could appreciate its timeless sound.

The AKG BX 20, with its character and iconic spring reverb, may have left my studio, but it will forever remain a part of my musical journey, a reminder of the compromises and decisions that come with the evolving landscape of audio production.


Features And Specs Of The AKG BX-20 Spring Reverberator.

The AKG BX-20 Reverberator is a vintage spring reverb unit known for its distinctive sound. Below are some of its key features and specifications:


  1. Dual-Spring Tank: The AKG BX-20 is renowned for its dual-spring tank design. This feature allows for a wide range of reverb sounds by utilizing two sets of springs with different characteristics. Users can select and blend these springs to achieve various reverb textures, from short and bright to long and lush.
  2. Stereo Operation: The BX-20 is capable of processing stereo signals, making it suitable for enhancing the spatial quality of stereo mixes and recordings.
  3. Multiple Reverb Algorithms: This unit provides various reverb algorithms to shape the sound, offering flexibility in creating the desired reverb effect. Users can experiment with different settings to achieve the right ambiance for their audio.
  4. User-Adjustable Parameters: The BX-20 includes user-adjustable parameters, such as reverb time, input level, and output level. These controls allow for fine-tuning the reverb effect to match specific audio sources and musical styles.
  5. Balanced Inputs and Outputs: The unit features balanced XLR inputs and outputs, which help maintain audio quality and compatibility with professional audio equipment.
  6. Front-Panel Controls: The BX-20 is designed with a front-panel user interface that includes knobs and switches for adjusting reverb settings and parameters. The interface is known for its straightforward operation.


  1. Reverb Technology: Spring reverb technology, where audio signals are sent through metal springs to create reverb effects through reflections.
  2. Size and Weight: The BX-20 is a relatively large and heavy unit, typical of vintage spring reverb devices. Specific dimensions and weight may vary depending on the model and version.
  3. Input/Output Impedance: The input impedance and output impedance are designed to ensure proper connectivity with audio equipment. These values may vary between models.
  4. Power Requirements: The unit typically operates on standard AC power, with voltage requirements varying depending on the region. Check the specific model for voltage details.
  5. Signal-to-Noise Ratio: The signal-to-noise ratio (SNR) indicates the quality of the reverb signal relative to noise levels. Vintage spring reverb units may have a characteristic noise profile that contributes to their unique sound.
  6. Maintenance: Vintage spring reverb units, including the AKG BX-20, require regular maintenance to ensure consistent performance. Maintenance may involve cleaning, reconditioning of springs, and electronics servicing.

Please note that the AKG BX-20 is a vintage piece of equipment, and the availability of specific models and versions may vary. If you are considering purchasing one, it’s advisable to refer to the product documentation for precise specifications and consult with vintage audio equipment experts for any necessary maintenance or restoration needs.


A Funny Story…

I remember the day I first set up the AKG BX-20 spring reverb unit in the studio with great excitement. It was a vintage piece of equipment known for its unique reverb character, and I was eager to experiment with its sonic possibilities. Little did I know that my enthusiasm would lead to a rather unexpected and amusing audio adventure.

After carefully unpacking the BX-20, I placed it on a sturdy rack and connected the necessary cables. As I powered it up, a sense of nostalgia and curiosity washed over me. This vintage piece of gear had a certain aura about it, and I couldn’t wait to hear how it would color my audio.

In my enthusiasm, I decided to position the BX-20 in a closet of the studio. It was a cozy, almost rustic spot, close to the room’s plumbing main, which included the bathroom. Little did I realize the potential consequences of this location.

As I started experimenting with various audio sources, running them through the BX-20, I was indeed captivated by the rich and characterful reverb it produced. Guitars sounded as if they were played in a vintage hall, vocals acquired a warm and lush quality, and even simple percussive elements took on a unique character. The BX-20 was everything I had hoped for.

However, my fascination with the reverb effect eventually led to an unintended discovery. One day, while tracking some vocals in the studio, I was puzzled by an unusual sound that kept creeping into the recordings. It was a faint, distant rumbling noise, and it seemed to coincide with certain vocal passages. At first, I couldn’t quite pinpoint the source of this sonic interference.

As the recordings progressed, the mystery deepened. It wasn’t until one day, during a break, that I suddenly realized the pattern. The odd rumbling noise occurred whenever someone in the house flushed the toilet. I couldn’t help but chuckle at the realization that the plumbing was interacting with the BX-20.

The BX-20’s placement near the plumbing main meant that the vibrations from toilet flushes were causing the springs inside the reverb unit to resonate and create unexpected feedback-like sounds. It was as if the bathroom had become an unintentional reverb chamber, and the toilet flushes were the secret modulation source.

While it was undoubtedly an unusual and sometimes comical issue, I couldn’t help but appreciate the creativity that had unintentionally emerged. I began to embrace this unique characteristic, incorporating it into my productions. The “toilet reverb” became a quirky signature sound in some of my tracks, adding a touch of unexpected humor and a story behind the music.

The experience served as a reminder of the unpredictable and sometimes delightful quirks that can arise in the world of audio production. It also highlighted the importance of studio setup considerations and the surprising ways in which sound can interact with its environment. The AKG BX-20, with its distinctive character, had not only added a touch of vintage charm to my recordings but had also brought an unexpected element of fun to my studio adventures.


The AKG BX-20 In Popular Music.

The AKG BX-20 has made notable appearances in popular music, thanks to its distinctive spring reverb sound and character. Here are some examples of its use in popular music:

  1. Led Zeppelin – “Whole Lotta Love”:
    • The AKG BX-20 was reportedly used in the iconic guitar solo section of Led Zeppelin’s “Whole Lotta Love.” The reverb’s unique character helped create the haunting and psychedelic atmosphere that defines this classic rock track.
  2. Pink Floyd – “The Dark Side of the Moon”:
    • Pink Floyd, known for their pioneering soundscapes, employed the BX-20 on their seminal album “The Dark Side of the Moon.” It contributed to the album’s immersive and otherworldly sound.
  3. The Rolling Stones – “Angie”:
    • The BX-20 was used on the Rolling Stones’ ballad “Angie,” contributing to the depth and emotional resonance of the track. Its warm and lush reverb added a sense of nostalgia to the song.
  4. David Bowie – “Heroes”:
    • The BX-20 played a part in shaping the reverb on David Bowie’s “Heroes.” The reverb effect on the vocals in the chorus is notable for its distinctive character.
  5. The Doors – “Riders on the Storm”:
    • In this classic rock song, the AKG BX-20 helped create the moody and atmospheric reverb that became an integral part of the track’s sound.
  6. The Who – “Who’s Next”:
    • The AKG BX-20 was used in the production of The Who’s album “Who’s Next,” contributing to the album’s spacious and dynamic sound.
  7. Neil Young – “Cortez the Killer”:
    • Neil Young’s guitar tones, including the reverb, in the song “Cortez the Killer” were shaped by the BX-20. The spring reverb added depth and character to Young’s guitar work.
  8. Daft Punk – “Random Access Memories”:
    • In the electronic music world, the AKG BX-20 has made appearances, as well. Daft Punk used it on their album “Random Access Memories” to add a vintage and analog touch to their electronic soundscapes.
  9. Arcade Fire – “Reflektor”:
    • Arcade Fire incorporated the AKG BX-20 into their album “Reflektor,” using it to create a sense of space and ambiance in their music.

These are just a few examples of the AKG BX-20’s use in popular music. Its unique spring reverb sound has left an enduring mark on countless recordings across various genres. The BX-20’s ability to add warmth, character, and a touch of vintage charm has made it a valuable tool for artists and producers seeking to create distinctive sonic landscapes.


The AKG BX-20 – Where To Get One.

The AKG BX-20 is a vintage and sought-after piece of audio equipment, which can make it challenging to find. Here are some places where you might be able to purchase an AKG BX-20:

  1. Vintage Audio Equipment Retailers: Some specialized vintage audio equipment retailers or dealers may occasionally have AKG BX-20 units available for sale. These stores often focus on classic and collectible audio gear.
  2. Online Marketplaces: Online platforms like eBay, Reverb, and Craigslist may feature listings for AKG BX-20 units from time to time. However, exercise caution when buying from these platforms and research sellers thoroughly to ensure authenticity and functionality.
  3. Audio Equipment Auctions: Keep an eye on audio equipment auctions, both online and in-person. Vintage gear auctions or estate sales may offer opportunities to purchase an AKG BX-20.
  4. Vintage Gear Brokers: Some vintage gear brokers or experts specializing in pro audio equipment may have access to AKG BX-20 units or can help locate one for you.
  5. Online Audio Communities and Forums: Engaging with online forums and communities for audio professionals and vintage gear enthusiasts can provide information on potential sources and sellers. Networking within these communities may lead to recommendations or opportunities.
  6. Music Production Studios and Professionals: Some recording studios or audio professionals who have owned AKG BX-20 units may be willing to sell them. Networking within the music production community can be a valuable way to discover available units.
  7. International Sources: Be open to sourcing the unit from international sellers, as vintage audio gear may be available in different parts of the world.

Please keep in mind that the availability of AKG BX-20 units may vary, and prices can be relatively high due to their vintage and collectible status. When considering a purchase, it’s crucial to verify the condition, authenticity, and functionality of the unit. Consulting with experts in vintage audio gear and reading the product documentation is advisable to ensure you make an informed decision.


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