Professional audio · SERVICE · REV 2026-10-06
Point Source systems
A point source distributes with a fixed pattern: the horn or waveguide sets the angle, and pattern control weakens below a frequency tied to the mouth size. If the seats sit inside that pattern, the cabinet or a small cluster is clearer than a short Line Array bought for the look.
Definition
The difference from an array is that coverage is not reshaped by angles between cabinets. The useful edge of the pattern is read from the manufacturer curve at frequency, usually at the fall the file names, not from an angle printed on the grille. This page gives neither that angle nor an SPL for a named cabinet. In the free field level falls near 6 dB per doubling of distance, and the room adds reflection, so the figure is not turned into a seat level.
A cluster of point sources — left, centre, and right, or two cabinets side by side — combs if the patterns overlap without splay and delay. One cabinet with the right pattern is cleaner. Under a balcony, the cabinet aimed at the balcony leaves a shadow. The fill is a delayed cabinet matched to the arrival, not more level from the main box as it hits the balcony face. Feedback rises when a wide horn looks at the microphone or a wall behind the talker returns the sound.
When is this service needed?
Seats inside one pattern
The room’s depth and height fall inside the cabinet’s angle at speech frequencies. A vertical line is unnecessary.
The room budget matters more
RT60 or noise sets STI. A suitable cabinet leaves money for treatment and isolation.
Filling a shadow
Under a balcony or behind a column. A small delayed cabinet, not a second array for appearance.
When it is not enough
The last seat is outside the pattern, and more gain burns the front row. That is when an array, or a higher hang point, is reviewed.
Where it is used
Conference rooms
A short throw and a nearby talker. Clarity comes from the pattern and the room, not from the length of the hang.
Small theatres
A cabinet or a cluster above the proscenium frame if it covers the stalls. A balcony, if there is one, is checked on its own.
Small cinemas and screening rooms
The screen constrains cabinet position. The pattern has to cover seats, not only strike the ceiling.
Front fills
The stage lip, where the array or the main cabinet is above the heads. Delay stops the image from splitting.
Parts of the solution
The cabinet and its pattern
A nominal angle from the manufacturer file, with the frequency it is measured at. Without the curve the number is a claim.
The mounting point
Height and tilt put the pattern axis on the last useful seat, not on the ceiling.
DSP for delay and gain
Especially for fills and clusters. A wrong delay makes a comb even if the prediction looked neat.
Under-balcony fill
A cabinet closer to the shadowed audience, at a level that completes rather than dominates, with arrival delay.
The microphone and its place
Off the axis of a wide horn, and away from a nearby reflection. This is part of the feedback margin.
Engineering considerations
Pattern control
It weakens at low frequency when the mouth is small relative to the wavelength. Speech may be controlled while bass from the same cabinet is not.
Distance law
Near 6 dB per doubling in the free field. The room adds the tail. The figure is not an operating level.
Balcony shadow
It starts where the balcony soffit blocks the acoustic view from the main cabinet. The fill goes there, not more gain that hits the fascia.
Feedback
A loop between microphone and cabinet through the pattern or a wall. The remedy is aim, distance, and surface, not only a global cut that kills coverage.
No invented level
No model SPL on this page. A target, if one exists, is measured in the seats against the brief.
Materials
One series in the cluster
Mixing unknown patterns makes gaps and overlap the file cannot predict.
The bracket or the hang
The load comes from the mounting document. A gypsum wall is not a default hang point.
Path treatment
A wall behind the microphone or a specular ceiling raises feedback and echo. Treatment supports the cabinet. It does not replace it.
Related systems
A Line Array if the section changes
If the throw grows and the balcony rises, choose again. No loyalty to the shape.
Subwoofer
A full-range cabinet does not replace low-frequency design in a large hall.
STI
For speech, measure to IEC 60268-16. A handsome pattern on the drawing is not an index.
Stage monitors
A wedge on the floor looking at the microphone is a feedback loop. Its place is part of the system, not an addition on rehearsal day.
Design sequence
- 01
Draw the section and place the proposed cabinet axis. Mark who falls inside the pattern and who falls out.
- 02
Read the manufacturer curve at speech frequencies, not the marketing angle alone.
- 03
If one cabinet covers, stop. A second element needs splay and delay or it combs.
- 04
Find the balcony shadow and add a delayed fill only where the shadow starts.
- 05
Put the expected microphones on the drawing and check the axis they share with the horn.
Delivery sequence
- 01
Tilt is fixed as drawn and locked. A degree upward after the site visit pours energy into the ceiling.
- 02
The fill is delayed from a measured arrival, not from a paced guess.
- 03
Zone gain is set on the edge seats, not only at mid-hall.
- 04
Feedback is tried with the real microphone positions before the audience.
- 05
The DSP file is stored with the hang drawing. A tilt change without a file update misleads the next visit.
Testing
Edge coverage
Seats at the start and end of the pattern. The fall at the edge is compared with the curve, not with an impression.
The fill
Under the balcony: one intelligible arrival, no echo from a late main or an early fill.
Feedback
The highest stable gain with the microphone in place. There is no universal figure on this page.
Commissioning
File and drawing
Tilt, height, fill delay, and measurement positions. Handover without them is a session, not a system.
STI for speech
If the brief asks for clarity, the method is IEC 60268-16. This page does not calculate the value.
Level from measurement
Any level target is documented from measurement or from the manufacturer file under its conditions. Not from this page.
Maintenance
Resetting tilt
After ceiling work, check the tilt. A cabinet that dropped half a degree changed the coverage.
Replacing with another pattern
A wider or narrower cabinet reopens the seat question and the feedback question. The trade name is not enough.
A new microphone
The capsule pattern is different. The feedback margin is checked again, not assumed.
Common mistakes
An array in a short room
The shape costs more and the result is a cabinet. The money belonged to treatment.
A cluster with no delay
Two cabinets covering the same seat without splay make a comb in speech.
Ignoring the balcony shadow
Turning the main up to reach under the balcony hits the fascia and bothers the stalls.
Gain instead of aim
The cabinet looks at the microphone and is then turned down until nobody is heard. Aim comes first.
Short comparison
The comparison is a way to choose a path. It is not a product recommendation and it is not a code.
| Path | Fits when | Weakens when |
|---|---|---|
| One cabinet | The section sits inside a known pattern at the programme frequency. | When the outer edge collapses, or the front row is far louder than the last if gain is raised. |
| A small cluster | The house is wider than one pattern, with calculated splay and delay. | When the cabinets stack on the same axis. The comb is worse than one cabinet. |
| Line Array | The throw is long and a fixed pattern cannot cover the vertical section without burning the front. | When the room is short and the array is bought because the photograph looks like a larger theatre. |
Discussion ranges
Any number here is a preliminary discussion range from practice or a named reference. Replace it with the project criterion, laboratory data, and on-site measurement.
| Item | What is discussed | Limit of this page |
|---|---|---|
| Nominal pattern angle | A figure from the manufacturer file, valid at the frequency and the fall the file names, often around the −6 dB point. | Not even coverage out to the edge, and not an angle this page chooses. Without the curve it is not used in design. |
| 6 dB per doubling of distance | Point-source behaviour in the free field, away from surfaces. | The room adds reflection. The figure is not a seat SPL and not the output of a named cabinet. Do not copy it as an operating level. |
| Fill delay | The arrival gap between main and fill so one source is heard. | Measured at the seat. No ready-made millisecond on this page. A distance guess with no measurement is not acceptance. |
| Feedback margin | The gap between operating level and the onset of ringing with the microphone in place. | A system result, not a cabinet rating. This page gives no margin in decibels. It is checked on site. |
What this page does not claim
No fire classification, absorption coefficient, sound pressure level, or legal capacity on this page may be copied into a quotation. Those values come from a product test report, a measurement, or the local code adopted for the project.
Questions designers and owners ask
When does one cabinet beat an array?
When the seats are inside the pattern and the room is short. You pay less, get cleaner coverage, and keep the budget for the room.
Is a cluster always louder and better?
Louder perhaps, cleaner no. Without splay and delay it combs. One correct cabinet beats two that fight.
What do I do under the balcony?
A nearby delayed fill. Do not turn the main cabinet up to punch through the soffit; it will hit the balcony face.
Why does it feed back with a small audience?
The microphone is on the horn axis or near a reflecting wall. Gain is not the only cause. Turn the cabinet and move the microphone.
Is the cabinet level written here?
No. There is no model SPL. Take the data from the manufacturer file under its conditions, then measure in the seats.
Technical sources
- The manufacturer polar file
Pattern angle and the frequency it is measured at. This page does not replace the curve and does not publish an SPL.
- IEC 60268-16
Speech-clarity acceptance where it is required. This page does not calculate STI.
- On-site transfer-function measurement
Delay, coverage, and feedback are closed by measurement, not by the office prediction alone.
Last editorial review: 2026-10-06. Review means the text was checked, not that a project was measured.
Turn the question into a brief
A study starts from room volume, use, and existing condition, not from a product name. Fill the brief and copy it.
Project study form