Understanding the Difference
You might wonder: how do OKHO/ BOBs and VIGO differ if they both use the same wide-band driver? The answer lies in the fundamental differences between their cabinet designs, the way they handle bass, and how they influence the overall sound reproduction.
Let's break it down.
Blocks is a common name for BOB – Bass Open Baffle bass modules, and OKHO – full-range monitor. Put together, they create a full two-way speaker system.The Role of the Cabinet in Sound Reproduction
A loudspeaker cabinet is not just a box—it plays a crucial role in shaping the sound. This is due to a key acoustic principle: the acoustic short circuit phenomenon. This occurs because a speaker driver produces sound waves both in front and behind it. If these waves meet and cancel each other out, particularly at lower frequencies, bass output is significantly reduced.
This issue becomes more pronounced as the frequency decreases, since lower frequencies have longer wavelengths. To mitigate this, speaker designers must carefully choose the type of cabinet to shape and guide the rear wave of the driver in a way that enhances bass response rather than canceling it out.
The role of the cabinet is even more important where light paper cone dynamic transducers are used and full range drivers in particular.
Consider two extremes:
The wide band driver EMS LB12 used in OKHO and VIGO has free air resonance - Fs 34 Hz.
1) If played in held in air with no enclosure almost all low frequencies will be lost resulting in a very thin sound.
2) On the other hand if played mounted in a wall, using another room as a giant back chamber it will be able to reproduce down to 34 Hz - amazing! So this would be optimal "cabinet" for it.
In real life it is it is very difficult to have a place in our homes to allow for such a scenario.
Between these two extremes, various cabinet designs attempt to balance bass extension, resonance control, and overall efficiency.
Here we can concentrate on two different and uncommon solutions.
Open Baffle Design (OKHO & BOBs)
OKHO and BOBs (Blocks Open Baffles) utilize a U-frame open baffle design. Since they do not have a traditional enclosed cabinet, they rely on multiple bass drivers to compensate for the natural bass loss caused by the acoustic short circuit.
Characteristics of OKHO with BOBs:
- Uses multiple bass drivers to move more air, compensating for the bass loss inherent in open baffle designs.
- More engaging and impactful sound, especially for large-scale symphonic music.
- Efficiency: 91 dB, making it dynamic but requiring more power than Vigo.
- Sounds best with more powerful amplifiers, though it can still work with lower-powered tube amps like 300B.
Diffuse Resonance Cabinet (VIGO)
VIGO, on the other hand, employs a diffuse resonance cabinet—a uniquely engineered enclosure designed to control and scatter internal resonances without using damping materials. The internal structure of the cabinet divides the rear wave into two separate channels conducting sound waves in two opposite directions:
1. A short, straight path.
2. A longer, more complex path with deflectors.
Characteristics of VIGO:
- Preserves efficiency and natural driver response without damping materials inside the cabinet.
- Heavy, rigid cabinet that prevents uncontrolled resonances while guiding sound waves in a controlled manner.
- Natural, transparent, and well-rounded sound compared to other boxed designs, with a slightly fuller upper midrange.
- Efficiency: 97 dB, making it easier to drive.
- Works well with small power tube amplifiers like 300B or 2A3.
How Do They Sound Different?
Midrange Reproduction
- VIGO: More focused and coherent, with a fuller lower midrange.
- OKHO with BOBs: More energetic and engaging, drawing the listener in.
Bass Performance
- VIGO: Clean, natural bass extension achieved through its unique internal resonance diffusion system, however slower in response compared to OKHO with BOBs.
- OKHO with BOBs: Additional bass drivers compensate for the open baffle bass loss, making it more direct, fast and impactful.
Sound Characteristics in Detail
VIGO:
- Natural, slightly more relaxed sound.
- Pleasant and naturally sounding vocals.
- Well-controlled bass, but not as deep as in the Blocks combination.
- Non-fatiguing and balanced presentation.
Blocks (OKHO + BOB + BOB):
- Fuller and more powerful and vibrant sound.
- Highly coherent and engaging performance.
- Dynamic and impactful bass response.
- Creates the sensation of being at a live concert.
Both systems sound remarkable, yet each has its own unique character. Closer Acoustics Vigo captivates with its natural and precise presentation, whereas the Blocks combination delivers a more authoritative sound with pronounced bass and greater transparency.
How they compare on the frequency response charts
On the following charts we registered Pink noise signal of both speakers in the same conditions.
Pink noise is a type of sound signal in which the power spectral density decreases by 3 dB per octave as frequency increases. This means that lower frequencies have more power than higher frequencies, resulting in a balanced and natural-sounding noise that resembles many real-world sounds, such as rainfall or rustling leaves. Pink noise is commonly used in audio testing, acoustics research, and speaker calibration because it evenly distributes energy across octaves, making it useful for analyzing frequency response in different environments.
Which One Is Right for You?
- If you prefer a natural and all-rounded sound with high midrange clarity and you have a small power amplifier, VIGO is the better choice.
- If you want an engaging, dynamic, and impactful presentation, especially for full philharmonic orchestral works or live jazz concerts, OKHO with BOBs will deliver that emotional intensity.
Listening Recommendation
A great live concert recording to experience these differences is Ahmad Jamal featuring Yusef Lateef LIVE IN OLYMPIA, recorded on June 27, 2012.
With OKHO and two BOBs, you can feel almost as if you're there. The kick drum - very present - soft yet decided; cymbals floating in the room, double bass vibrant and almost palpable, and finally Ahmad Jamal’s grand piano create an immersive atmosphere with rich textures and spatial depth. The sheer presence and realism of the performance highlight the strengths of an open baffle system.
Meanwhile, VIGO offers a more intimate presentation, bringing out the nuances of the recording with effortless transparency.
Final Thoughts
Both designs excel in different ways. Open baffle speakers like OKHO offer a free, spacious sound but require multiple drivers for bass, while VIGO’s diffuse resonance cabinet creates a controlled, natural sound without the need for bass reinforcement.
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A detailed review of the VIGO (both permanent magnet and electromagnet versions) by Andrzej Kisiel, Editor-in-Chief of Polish AUDIO monthly, is available here