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EQ and filters

Every enclosure has its own filters, in EQ / filters in the Driver panel. They shape the signal before it reaches the driver, so the output, the cone’s travel and the port’s air speed all follow them. The filter most boxes need is a high-pass just below the tuning.

The six filters#

Add, in EQ / filters, offers six kinds. Here is each one’s own gain:

HP

High-pass filter

dB

30 Hz · BW 24 dB/oct

LP

Low-pass filter

dB

120 Hz · BW 24 dB/oct

PEQ

Parametric EQ

dB

100 Hz · +6 dB at Q 1, −6 dB at Q 4 dashed

LS

Low shelf

dB

80 Hz · +6 dB

HS

High shelf

dB

200 Hz · −6 dB

LT

Linkwitz transform

dB

50 Hz, Q 0.707 to 25 Hz, Q 0.5

Worked out with the app’s own filter maths. High-pass, low-pass and Linkwitz transform at the settings Add gives them; the others with example gains, since they start at 0 dB.
FilterShown asWhat it doesSettings
High-pass filterHPRolls off everything below the cutoff, so the cone and port are spared bass the box cannot play.Cutoff, Type, Slope
Low-pass filterLPRolls off everything above the cutoff, as a subwoofer’s crossover to the mains does.Cutoff, Type, Slope
Parametric EQPEQA boost or a cut around one frequency.Center frequency, Gain, Q (bandwidth)
Low shelfLSRaises or lowers everything below its frequency.Shelf frequency, Gain
High shelfHSRaises or lowers everything above its frequency.Shelf frequency, Gain
Linkwitz transformLTMoves a sealed box’s roll-off from its own resonance and Q to a lower, gentler one, with boost.Source F₀ (Fc), Source Q₀ (Qtc), Target Fp, Target Qp
  • Cutoff, Center frequency and Shelf frequency run from 10 Hz to 20 kHz, Gain from −15 to +15 dB, and Q (bandwidth) from 0.1 to 16: lower is wider.
  • The Linkwitz transform takes a sealed box’s resonance and Q as its source (20–200 Hz, Q 0.3–2) and moves them to a target (10–100 Hz, Q 0.3–1.5). For a sealed box the enclosure panel shows both, as its system resonance (Fsc) and system Q (Qtc).
  • A new filter starts at a sensible frequency (30 Hz for a high-pass, 120 Hz for a low-pass, 100 Hz for parametric EQ) and at 0 dB where it has a gain, so it changes nothing until you set it.

High-pass and low-pass slopes#

A high-pass or low-pass has a Type, the filter family, and a Slope, how fast it falls in dB per octave. A new one is BW at 24 dB/oct. Change the Type and it keeps the nearest slope the new family has.

TypeSlopesAt the cutoffGood for
BW6, 12, 18, 24, 36 and 48 dB/oct−3 dBThe flattest passband. The usual choice for a subsonic high-pass.
LR12, 24 and 48 dB/oct−6 dBSums flat with the matching filter at a crossover, so it is the one to cross a subwoofer to mains with.
Bessel12 and 24 dB/oct−3 dBThe gentlest phase, and the softest knee.
HP

High-pass at 30 Hz

dB

  • BW 12 dB/oct
  • BW 24 dB/oct
  • BW 48 dB/oct
  • LR 24 dB/oct
  • Bessel 24 dB/oct
The same 30 Hz high-pass in five slopes. Steeper slopes cut harder below the cutoff and leave more above it; they also turn the phase further near the corner.

Add, switch off and copy#

  1. 1

    Select the enclosure

    Click its row in the enclosure list. Filters belong to one enclosure. A multiple-entry horn keeps a set per driver: pick the driver with the chips above its filters.
  2. 2

    Open EQ / filters

    It is in the Driver panel on the right. Its header counts the filters that are on.
  3. 3

    Add one

    Add › the kind you want. The new filter opens with its settings; click any filter’s row to fold or unfold it. If you have clicked a graph to lock its cursor, the new filter goes in at that frequency.
  4. 4

    Switch off or delete

    The tick box on a filter’s row turns it off and keeps its settings, the quick way to see what it does. The bin deletes it.

Copy from... appears once another enclosure, or another driver of a multiple-entry horn, has filters. It opens Copy filters from: choose a set and a copy of it replaces this enclosure’s filters.

Edit filters on the graph#

EQ in a tile’s header (Edit EQ on graph) draws the selected enclosure’s filters on that tile as handles, and Exit puts the tile back. It is on SPL (dB), Max SPL (dB), Headroom, Excursion, Port Velocity and Transfer Function Magnitude. The EQ Editor tile has its handles out all the time.

  • A high-pass or low-pass is a triangle on a dashed line: drag it sideways to move the cutoff. Click it for its editor, where the HP or LP chip flips it between the two, with the frequency, Type, Slope and Delete.
  • Parametric EQ and shelves are a dot: drag it sideways for frequency and up or down for gain. Selected, it shows a handle either side; drag those to make it wider or narrower. A shelf’s chip flips it between low and high.
  • Right-click a graph for Add filter: each kind, placed at the frequency you clicked. The tile switches to EQ and the new filter opens.
  • On a multiple-entry horn the other drivers’ filters show as dashed chips along the top; click one to edit that driver’s filters.
  • On a phone, tap a graph to lock the cursor, then EQ here adds a filter at that frequency, and a selected filter’s editor opens as a sheet: On a phone.

Undo (⌘/Ctrl+Z) takes back filter changes like any other edit.

Protect the cone with a high-pass#

Below its tuning a vented box stops holding the cone back, and excursion climbs fast. In the 55 L vented example at 200 W, the Ciare 12.00SW passes its 13.5 mm Xmax below 19 Hz. A 25 Hz high-pass at 24 dB/oct keeps it to 6.3 mm and costs 0.6 dB at the 32 Hz tuning.

Excursion

mm

  • No filter21.2 mm at 10 Hz
  • High-pass 25 Hz, BW 24 dB/oct6.3 mm at 24 Hz
Ciare 12.00SW in the 55 L vented example tuned to 32 Hz, at 200 W, half space, 1 m. Simulated when this page was built.

SPL (dB)

dB

  • No filter · F3 30.3 Hz
  • High-pass 25 Hz, BW 24 dB/oct · F3 31.1 Hz
The high-pass takes away the octave below the tuning, where the box makes little sound but the cone does most of its travelling.
High-pass, BW 24 dB/octPeak excursionLost at 32 HzPeak port air speed
None21.2 mm and rising0 dB28.4 m/s
20 Hz9.2 mm0.1 dB27.9 m/s
25 Hz6.3 mm0.6 dB26.0 m/s
30 Hz5.2 mm2.2 dB21.8 m/s
The same box and power, 10 Hz to 200 Hz. 30 Hz is where Add puts a new high-pass.
  • Open the vented example at 200 W, add a High-pass filter and drag it on the Excursion tile until the curve sits under the Xmax line.
  • Set it a little below the tuning. Higher protects more and costs more output at the tuning; the table shows the trade.
  • A high-pass turns the phase, so group delay rises near the tuning: here from 26.7 ms to 41.7 ms at 32 Hz.

Ask your AI#

Ask your AI

Your assistant runs the same solver on your own designs through the 00 Simulator connector, and can try filters without changing your workspace.
Using 00 Simulator, try a 24 dB/oct Butterworth high-pass at a few frequencies below the tuning of each vented box in my open workspace, without saving. For each, tell me the peak excursion against the driver’s Xmax and how much output it costs at the tuning.
or open it inClaudeChatGPT

Connect your assistant so it can open your designs.

EQ EditorExcursionPower and limitsFix a noisy portSealedLimits: travel, heat and air