Key Takeaways
- Speech intelligibility at the back of the room is the primary acoustic objective — not maximum SPL or impressive visual appearance of the PA system
- Room acoustics (reflections, reverb time, HVAC noise) affect speech intelligibility more than the PA system specification in many Indian hotel ballrooms
- A line array produces more even coverage across a deep room than a point-source system at equivalent SPL — the investment is justified above 300 pax
- Front-fill speakers are essential for the first three rows of any seated conference — main line arrays cannot cover this area adequately
- The minimum microphone count for a produced corporate conference: one for the lectern, one for each panellist, one handheld for audience Q&A
Speech intelligibility first
The PA system specification for a corporate conference should be driven by one objective above all others: every delegate in the room should be able to understand every word the speaker says without straining. Not at high volume — at comfortable conversational loudness above the room's ambient noise. This requires: sufficient PA coverage to deliver a consistent SPL across the entire seating area; an SPL level (typically 75–85 dB SPL in the audience area) above the room's ambient noise floor; and a frequency response that prioritises the vocal range (200 Hz–8 kHz) where speech intelligibility lives.
The line array advantage for deep rooms
A line array (a vertical column of small speaker elements that creates a controlled, narrow vertical dispersion pattern with wide horizontal coverage) delivers consistent SPL from the front row to the back row across a deep room in a way that a conventional speaker cluster cannot. The physics: a line array's SPL decreases at approximately 3 dB per doubling of distance (compared to 6 dB per doubling of distance for a point-source speaker). In practice, a 500-person room with 25 metres of depth will have 9–12 dB less SPL at the back than the front from a point-source system, but only 4–6 dB less from a well-designed line array. This translates directly to speech intelligibility at the back of the room. For events below 300 pax in a shallow room, point-source speakers are adequate. Above 300 pax or in deep rooms, line arrays are the correct specification.
The HVAC problem in Indian ballrooms
Indian hotel ballrooms are air-conditioned, and the HVAC system's noise floor is typically 45–55 dB SPL in a ballroom at full load. This is 15–20 dB above an empty room's acoustic floor, and it sets the minimum PA level required for comfortable speech intelligibility. Hotel HVAC systems also produce significant low-frequency noise (80–120 Hz), which sits directly under the vocal range and muddies the perceived clarity of speech. A good audio engineer will calibrate the PA's low-frequency response to account for the room's HVAC contribution. A standard corporate AV setup with default factory settings will not — and every hour of the conference, delegates in the back third of the room will feel slightly exhausted from the mental effort of parsing speech against an HVAC noise floor.
The microphone brief
Every microphone used at a corporate event must be briefed to the audio engineer before load-in: who uses it, what they will be doing while using it (standing at a lectern, walking the stage, sitting at a panel table, holding it while moving freely in the audience), and what their microphone preferences are (lapel, headset, handheld, podium). The most common microphone error at Indian corporate conferences: a single podium microphone for a panel session where three panellists share one microphone by leaning toward it — an audio design failure that is entirely preventable with a three-person panel microphone kit that costs ₹15,000–25,000 to add to the production specification.