Studio monitors: woofer, directivity, maximum SPL and subwoofers.

With the room treated and listening position fixed, a monitor stops being a box and becomes an instrument: read its specification without entirely believing it, and understand what each figure measures. This guide covers the core buying and operating decisions: Woofer size, Directivity, Maximum SPL, Choosing monitors for a small room, Studio subwoofer: when to use one, Sub placement and crossover and Two subs in a studio.

If you came from the previous guide, you have already ruled out monitors too large for your room; we now refine the choice within that framework.

Woofer size

Woofer size—4, 5, 6.5 or 8 inches—is the figure most used for comparison and most poorly interpreted. A large cone moves more air volume, reaching lower frequencies, but also returns more energy to the room exactly where walls already accumulate it: the mode amplifying 45 Hz remains, and the larger monitor feeds it harder.

What inches do not tell you: filter cutoff, allowable excursion, distortion at working level and behaviour near a wall. Two 6.5-inch monitors can differ in extension by a factor of two, and a good front-ported 5-inch monitor can give a flatter desktop response than a poorly positioned 8-inch one.

Decision criteria:

• Small room or desktop: 4 to 5 inches; fill the bass gap later if needed.
• Small room with bass-demanding music: 6.5 inches with a good port, measuring the position first.
• Medium room: 6.5 or 8 inches, or 5 inches plus a sub when budget permits.
• Any size: choose by measured extension and distortion, not the website number.

A reality check: if your music lives between 60 Hz and 10 kHz, almost any current midrange monitor works; the remaining budget achieves more in treatment than inches.

Directivity

Directivity describes how a monitor distributes sound in all directions by frequency. Practically, one thing matters: what reaches your ears directly and what arrives after bouncing from ceiling, walls and desk.

A monitor with smooth, constant directivity sends each surface a balance similar to its forward output. When that reflection returns, it resembles the direct sound, producing a smooth, predictable response. Abrupt directivity—for example, a horn directing treble while a woofer spreads it everywhere—sends the room a different balance from your position, colouring each reflection differently: the room ceases to be neutral even after treatment.

Read these specification points carefully:

• Horizontal and vertical pattern: the vertical axis is often most problematic because the desk and ceiling are there.
• Consistency across frequencies: stability from bass to treble matters more than narrowness.
• Diffusers or undulating profiles: some manufacturers shape the horn edge to smooth directivity, not for appearance.
• Listening-area width: wide directivity gives more freedom to move your head; narrow directivity gives less.

Thus, directivity determines how much colour the room adds. A monitor in a well-treated room but with abrupt directivity still colours sound; smooth directivity lets it sound more like itself in more rooms.

Maximum SPL

Maximum SPL is the peak level a monitor can emit before distortion or electronic protection intervenes. It serves one purpose: checking that at your listening position, allowing for mix peaks, you work below the limit.

How to read the figure correctly:

1. Distance: SPL falls 6 dB whenever distance doubles. A value measured at one metre is not your level at two metres.
2. Content: a pink-noise peak is not the same as continuous level with dynamic music.
3. Headroom: you need 10 to 15 dB above working level so compression does not colour your judgement.
4. Band: bass SPL runs out first and demands the most from the sub and modes.

In small rooms, monitor SPL is rarely the bottleneck: it is usually room behaviour at high levels, where bass escalates and materials start resonating. Raising volume therefore does not improve decisions; it amplifies problems. If your reference level is around 79 to 85 dB SPL at the ear, a midrange monitor reaches it comfortably; the limit is room bass rather than tweeter treble.

Choosing monitors for a small room

Choosing monitors for a small room starts with accepting its limits: short distances, closely spaced walls, exposed modes and little space behind monitors. Here, geometry pays off before specifications.

Practical recipe:

• Near, not far: 1 to 1.8 metres between tweeter and ear, with heights and angles aligned to a seated head.
• Unequal wall distances: avoid the exact room centre; move the position 10% if room symmetry allows without breaking the image.
• Monitors on stands or arms, never rigidly touching the desk: the desk reflection is among the earliest.
• Less monitor: in a small room, prioritise clean response and smooth directivity over bass extension.
• Rear port with space: leave the manufacturer’s required clearance; if it does not fit, choose a front port or sealed enclosure.

Remember the sequence: first fix position and desk reflection, then buy. A monitor bought before fixing the position is calibrated twice and almost always replaced when the room is defined. Buying is easier once positioning is measured and repeatable.

Studio subwoofer: when to use one

Studio subwoofer: when to use one is a question of workload: a sub does not “improve” a system; it takes the band small monitors cannot reproduce with sufficient control.

Arguments in favour:

• Real extension: confidently reaching below 40 or 35 Hz requires diaphragm area and volume, packaged better in a sub than two small monitors.
• Room loading: a sub addresses bass where the room is most sensitive, and calibration can minimise harm.
• Less fatigue: small monitors stop attempting impossible bass and sound cleaner in the mids.

Arguments against, or at least conditions:

• Not without treatment: a sub in a room without treated corners amplifies modes and worsens the mix.
• Not without measurement: find the position causing the fewest problems before fixing it.
• Not without musical need: if your catalogue lives above 50 Hz, a sub puts weight and budget in the wrong place.

The honest test: play reference tracks and check whether real content below 50 Hz is missing, or you simply want the room to feel larger. The former justifies a sub; the latter is almost always better addressed through bass treatment.

Sub placement and crossover

Sub placement and crossover are half the result. Placement determines which modes are excited; crossover decides what work the sub performs and what the monitors stop doing.

Placement, in effectiveness order:

1. Try off-axis: move the sub away from the front wall’s centre; corners amplify more, but offer more adjustment range.
2. Measure at the listening position: seek smooth bass at the chair, rather than the loudest bass in the corner.
3. Fix distance and level: the classic six-inch displacement rule or the manufacturer’s setup-software procedure are covered in its official documentation.

Crossover, with the numbers that matter:

• Frequency: 60 to 90 Hz for small monitors; where monitors start overloading, rather than where the sub sounds loudest.
• Slope: 24 dB/octave or steeper so monitors and sub do not overlap excessively.
• Phase and delay: aligning sub and monitor outputs prevents a hole at the crossover frequency; without this, the system sounds worse with a sub than without one.
• Sub volume: set monitor level first, then hold the sub back until bass integrates without standing out.

The classic mistake is setting crossover too high to “hear” the sub. That puts low mids in a box not designed for them and worsens rather than improves the crossover region.

Two subs in a studio

Two subs in a studio is not decorative luxury: it is a technique with specific physical justification. A single sub, however well positioned, excites both the room’s axial mode—front-to-back or sideways—and lateral modes; the result depends on seating position, with maxima and minima around the room.

Two subs, symmetric relative to the room and appropriately processed—level, delay and sometimes EQ—attenuate the main axial mode because they address the front wall with the correct phase relationship. The room responds much more uniformly between chairs, and fine software corrections face fewer peaks.

When it makes sense:

• A medium room with a clear spatial bass-position problem.
• Work where different listeners or room positions matter.
• A well-positioned single sub has already been tried but measured holes remain.

When it does not:

• A small room with budget for one sub: a single well-positioned sub is better.
• An untreated room: two subs multiply energy in an acoustically poor space.
• Before mastering one sub’s phase: adding a second system to calibrate only adds variables.

The sensible progression is well-positioned monitors, measurement, one phase-aligned sub and only then considering a second.

Next step

You know which monitor size fits the room, what directivity means and when, how and with how many subs to complement the system. What remains is setting the whole system to the correct level and matching left and right: pink-noise calibration, reference level and room correction.

Monitor calibration: reference level, pink noise and room correction