Highly directional mic with tight pickup pattern — standard tool for on-set dialogue. Mounted on boom pole or camera, isolates target source reliably.
Technical Fundamentals
A shotgun microphone (or directional microphone) is a specialized condenser microphone with extreme directionality. Unlike an omnidirectional microphone, which picks up sound equally from all directions, a shotgun microphone targets a specific direction and suppresses everything else.
Pickup Pattern: Super-Cardioid vs. Hypercardioid
The polar pattern is represented by a polar diagram:
Cardioid (heart-shaped):
- Front: +0 dB (reference)
- Sides (90°): -10 to -15 dB
- Rear (180°): -20+ dB
Super-Cardioid (narrower, more pointed shape):
- Front: +0 dB
- Sides (90°): -15 to -20 dB
- Rear (180°): -10 to -15 dB (somewhat audible from the rear)
- Null points at approx. 125° and 235° (dead zones)
Hypercardioid (even narrower):
- Front: +0 dB
- Sides (90°): -20+ dB
- Rear (180°): -5 to -10 dB (more audible from the rear)
- Null points at approx. 110° and 250°
Standard for film sets: Super-Cardioid (e.g., Rode NTG3, Sennheiser MKE 600) offers the best balance between directionality and controllability.
Typical Shotgun Specifications
| Specification | Standard Value | Example (Rode NTG3) |
|---|---|---|
| Frequency Response | 50 Hz - 20 kHz | 20 Hz - 20 kHz |
| Pickup Pattern | Super-Cardioid | Hybrid Super-Cardioid |
| Sensitivity | -35 to -40 dBV/Pa | -39 dBV/Pa |
| Max SPL | 130+ dB | 137 dB SPL |
| Self-Noise | 18-25 dB-A | 24 dB-A |
| Length | 20-30 cm | 29 cm |
| Weight | 150-250 g | 285 g |
| Power Supply | Phantom Power (48V) | 1x AA or external battery |
How Does Directionality Work?
The super-cardioid pattern is achieved through acoustic delay:
The microphone has several small sound ports along its barrel. Sound from the front hits all ports simultaneously (constructive interference = amplification). Sound from the side hits the rear ports with a delay (destructive interference = cancellation).
Result:
- Front: Sound waves add up → +0 dB
- Sides: Sound waves cancel each other out → -15 to -20 dB
- Rear: Partial cancellation, but not complete
This is why a shotgun microphone is longer (30 cm vs. 10 cm for omni): the length allows for precise delays.
Frequency Response and Sound Characteristics
A typical shotgun microphone has an intentional presence boost to enhance dialogue:
Standard Frequency Response of a Rode NTG3:
- 50-100 Hz: Slightly reduced (high-pass filter, prevents wind noise and low room resonances)
- 100-250 Hz: Flat (bass region for voice)
- 250-1 kHz: Slightly increased (+3-4 dB presence peak)
- 1-4 kHz: Significantly increased (+6-8 dB, "sibilance" and speech intelligibility)
- 4-8 kHz: Moderately reduced (less aggressive than other ranges)
- 8 kHz+: Reduced (less "air," but also less sibilance)
Why this shape? Dialogue intelligibility lies in the 250 Hz - 4 kHz range. The shotgun is designed to make dialogue sound naturally brighter and more present.
Practical Requirements in Set Operation
Pointing Correctly is Critical
The super-cardioid pattern means directional sensitivity:
- ±15° off-axis: Full gain (-0 dB)
- ±30° off-axis: Slight reduction (-5 dB)
- ±45° off-axis: Significant reduction (-10 dB)
- ±90° off-axis: Heavily reduced (-15 to -20 dB)
Practical Example:
You position the shotgun 30 cm above the actor's head, directly in front. The actor is on-axis = maximum signal. The actor turns their head 45 degrees to the side (e.g., profile shot). The signal drops by about 10 dB – they become quieter and the sound duller.
Boom Op Solution: During lateral movements, the boom operator must rotate the boom pole to keep the mic on-axis to the mouth.
Frequency Response at Different Distances (Proximity Effect)
The shotgun microphone minimizes the proximity effect due to its directional pattern, but it is not eliminated:
- At 15 cm distance: Noticeable bass boost (+6-8 dB below 200 Hz)
- At 30 cm distance: Slight bass boost (+2-4 dB)
- At 60 cm distance: Minimal bass boost
Most boom operators work in the 25-40 cm range, where the proximity effect is still present but moderate.
Standard Equipment and Setup
Top Models in the Industry
Rode NTG3 (Hybrid Pattern, €400-€600)
- Hybrid Super-Cardioid (can switch between modes)
- Robust, neutral sounding
- Industry standard for feature films
- Battery-free operation possible (Phantom Power)
Sennheiser MKE 600 (Super-Cardioid, €200-€400)
- Compact, reliable
- Slightly duller sound (acceptable for most use cases)
- Standard for BBC, many European TV shows
- More affordable, but quality is also noticeable
Audio-Technica AT875R (Cardioid, €300-€500)
- Slightly less directional than Super-Cardioid
- Warmer sound
- Popular in US productions
Sennheiser MKE 400 (Cardioid, cheaper, €150-€250)
- Budget option, acceptable for documentaries
- Not recommended for feature films
- Noticeably noisier and less neutral
Mounting and Shock Mount
The shotgun is mounted with a shock mount (rubber suspension):
- Isolates vibrations from the boom pole
- Dampens handling noise
- Example: Rode Boom Suspension (€100-€150)
Windscreen
A windscreen (or "windjammer") is essential:
- Foam: For interiors or light outdoor breezes
- Furry windscreen (artificial hair): For outdoor shooting or strong winds
- Can reduce wind noise by 10-20 dB
- Cost: €30-€150
Common Mistakes and Consequences
| Mistake | Auditory Consequence | Cause | Remedy |
|---|---|---|---|
| Microphone not on-axis | Quieter, duller dialogue | Boom not rotating with actor | Boom operator must rotate mic with actor's movement |
| Windscreen forgotten (outdoors) | "Whooshing," wind noise | Direct wind on the mic | Attach windscreen immediately |
| Too far from the actor | Quieter dialogue, more room echo | Boom extension too short or hesitant | Move closer, often only possible with tighter framing |
| Directional microphone not "warmed up" | Unstable frequency response | New battery or phantom power supply | Test microphone 10-15 minutes before shooting |
| Polarity reversal (phase error) | Thin voice, canceled bass frequencies | XLR pins 2 and 3 swapped | Check or reconfigure XLR cable |
| Overload with loud dialogue | Distortion, clipping | Mixer input level too high or faulty microphone | Reduce input level, or replace microphone |
Industry Standards for Shotgun Use
Raw Sound Requirements (On-Set Recording)
The sound mixer adheres to the following standards:
- Dialogue Peak Level: -12 to -6 dBFS (large headroom)
- Quiet Noise Floor: -60 to -50 dBFS (very quiet)
- Signal-to-Noise Ratio: 50+ dB (shotgun provides this)
- Frequency Response: Flat or slight presence peak (no aggressive EQ)
- No Clipping: Zero digital artifacts
The shotgun microphone enables these standards through its directionality – it primarily captures the actor's voice, not the environment.
Frequency Range for Dialogue Recording
During the mixing phase, the sound engineer expects the following characteristics from the raw shotgun signal:
| Frequency Range | Characteristic | Desired Behavior |
|---|---|---|
| 50-100 Hz | Very quiet or absent | Clean (no hum, no wind) |
| 100-250 Hz | Vocal fundamental | Neutral, no bass boom |
| 250-1 kHz | Vocal body | Present, but not muffled |
| 1-4 kHz | Speech intelligibility | Clear, present, "intelligible" |
| 4+ kHz | Air and detail | Natural, not artificial or breathy |
Level Comparisons: Shotgun vs. Lavalier
| Aspect | Shotgun | Lavalier |
|---|---|---|
| Typical Peak Level | -8 dB | -3 dB |
| Room Tone | Moderately present | Minimal |
| Clothing Noise | None | Frequent |
| Adjustability | High (boom position) | Low (fixed to body) |
| Proximity Effect | Moderate | Strong |
| Best Sound Quality | Static dialogue | Action scenes |
Practical Checklist for Shotgun Microphones
- [ ] Battery or phantom power set and functioning
- [ ] Perform microphone test: check "pop sound" and silence
- [ ] Windscreen attached (indoor or outdoor version)
- [ ] Shock mount stable, no wobbling
- [ ] XLR cable connected and not kinked
- [ ] Polarity checked (L/R or phase test)
- [ ] Microphone sensitivity calibrated with test measurements
- [ ] Multi-position test with different actor distances
- [ ] Off-axis recording test (to check proximity effect)
- [ ] Frequency response neutral or as expected
- [ ] For feature films: Neutral sound without pre-filtering
Summary
The shotgun microphone is the backbone of film and television sound production. Its super-cardioid pattern allows boom operators to precisely capture dialogue and minimize ambient noise.
A good shotgun (Rode NTG3, Sennheiser MKE 600) combines:
- High directionality (Super-Cardioid Pattern)
- Neutral-sounding frequency response (with a slight dialogue boost)
- Robustness (130+ dB SPL)
- Low self-noise (18-25 dB-A)
With a high-quality shotgun and an experienced boom operator, a production team can ensure that dialogue recordings on set are already of professional quality – which significantly saves effort in post-production editing later.