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Coles 4001 Super Tweeter

New Coles 4001G & Coles 4001K Tweeters 

 

The Coles 4001 series remains one of the most enduring and critical components in the history of British high-fidelity audio. Originally developed for broadcast and studio monitoring applications, these units are famous for providing the "air" and delicate high-frequency extension that defined the legendary BBC sound.

Celestion HF2000 replacement

The 4001k a Celestion HF2000 replacement where used as a super tweeter (NB not suitable for Ditton range systems, please see SEAS 19TFF-1 for this application available here). 

Why the 4001 Series Matters

  • BBC Heritage: A primary component in the most celebrated monitors of the 20th century, providing smooth response from 5 kHz up to 25 kHz.

  • Unmatched Transparency: Known for its wide dispersion and non-fatiguing character, the 4001 allows for a spacious, open soundstage that modern alternatives struggle to replicate.

  • Versatility in Restoration: Whether you are servicing a pair of Spendor BC1s, B&W DM2s, or large IMF Transmission Lines, the 4001 series provides the exact factory-spec performance required.

Full Manufacturers Guarantee as current production.

Read More about Coles Tweeters

 

The Coles 4001K is a legendary British-made super-tweeter that has been a staple in high-end audio for decades. It is widely respected for its ability to handle extremely high frequencies and is most famous for its role in classic BBC-specification monitors.

Core Technical Specifications

The "K" variant is the 7-8 Ohm version (whereas the "G" variant is the 16 Ohm version).

  • Type: Plastic dome super-tweeter.

  • Frequency Response: Typically used to cover the range from 5 kHz up to 25 kHz (and sometimes beyond).

  • Power Handling: 120W (system dependent).

  • Sensitivity: Approximately 87dB (1W @ 1m).

  • Faceplate: 76mm diameter, usually featuring a distinctive protective mesh or grille.

Historical Significance & Usage

The 4001K is inextricably linked to the "British Sound" of the 1970s and 80s. Its primary purpose was to take over where standard tweeters of the era rolled off, providing the "air" and delicate transient detail required for broadcast-quality audio.

Notable Speakers Featuring the 4001:

  • BBC LS3/5A: In many configurations, it was paired with the KEF T27.

  • Spendor: Used in the classic BC1 and BC3 models.

  • B&W: Featured in the DM2 and DM2a.

  • IMF Electronics: Specifically the large TLS80 transmission line speakers.

Sound Characteristics

Audiophiles generally value the 4001K for its transparency and lack of "shoutiness."

  • Pros: It provides a very wide dispersion, which helps create a spacious soundstage. It is known for being exceptionally smooth and detailed in the uppermost octaves.

  • Cons: Because it is an older design, some modern listeners find it slightly "polite" compared to contemporary ribbon or beryllium tweeters.

Restoration & Modern Availability

The Coles 4001K is still in production today by Coles Electroacoustics in the UK, which is a rarity for such an old design.

  • Drop-in Replacement: It is often sought after as a direct replacement for failing units in vintage Spendor or B&W cabinets.

  • DIY Projects: It remains a favorite for DIY builders looking to replicate the BBC signature sound or for those building high-quality 3-way or 4-way systems.

Whether you are looking to restore a pair of classic studio monitors or are designing a system that requires a vintage-voiced super-tweeter, the 4001K remains one of the most reliable and sonically consistent options on the market.

 
 
 
 
 

The Coles 4001 series represents a cornerstone of British loudspeaker design. While the 4001K and 4001G are nearly identical in construction and sonic signature, the primary distinction lies in their electrical impedance, which dictates how they are integrated into specific crossover networks.

The Key Difference: Impedance

  • Coles 4001G (16 Ohm): This was the standard for many early BBC-style designs. High-impedance tweeters were often used to maintain a stable load when paired with other drivers in complex 3-way or 4-way systems.

  • Coles 4001K (7-8 Ohm): The more common modern standard. It is generally easier to integrate into contemporary crossover designs and is the go-to choice for most current restoration projects or new builds.

 
Shared Technical Specifications

Despite the impedance difference, both units share the same physical footprint and performance characteristics:

  • Type: 19mm plastic dome super-tweeter.

  • Frequency Range: 5 kHz to 25 kHz.

  • Sensitivity: ~87dB (1W @ 1m).

  • Faceplate: 76mm (approx. 3 inches) with a protective metal mesh grille.

  • Dispersion: Exceptionally wide, contributing to a "wraparound" soundstage.