Power and limits

Set the power#

1. 1

   Select the enclosure

   Power belongs to each enclosure, not to the workspace. Click its row in the enclosure list.
2. 2

   Open Power

   In the Driver panel, open Power. Its header shows the current watts, so you can read it with the section closed.
3. 3

   Set the input power

   Type a value in Input power, drag the slider, or click one of the numbers under it. The slider is logarithmic, from 0.01 W to 100 kW, so each tenfold step in watts is the same distance.

• Load voltage, at the foot of the section, is the drive voltage that power works out to.
• Series resistance stands for the cable and the amplifier’s output, from 0 to 10 Ω; it starts at 0.1 Ω.
• Series capacitor puts a capacitor between the amplifier and the drivers, with its Capacitance (0.1 µF to 100,000 µF) and ESR (0 to 10 Ω). It starts at a stock value sized for the load: 1000 µF for the Ciare 12.00SW’s 3.3 Ω coil.
• With several drivers in one box, the input power is the total for all of them, shared equally. A multiple-entry horn has a power row for each driver, with a button that mutes it, and the header shows the total.
• On a phone, tap the watts in the dock to open the same control.
• Someone viewing your share link can change the power to hear your design at their level. The box itself stays as you made it.

What power changes#

More power raises the SPL curve without changing its shape. In the vented example, doubling the power from 100 W to 200 W adds 3.0 dB of level, and ten times the power adds 10.0 dB. The cone’s travel and the port’s air speed grow with the square root of power: both are 1.41 times as much for the same doubling.

How loud can it go: Max SPL#

1. 1

   Add the tile

   Add Max SPL (dB) with Add tile. Its curve is the loudest each design can play at each frequency, one frequency at a time, before the cone passes Xmax or the voice coil passes its thermal limit.
2. 2

   Turn on Limits

   Click Limits in the tile’s header to draw the two ceilings, heat dashed and Xmax dotted. The Max SPL line follows whichever is lower, so you can see which one stops the design at each frequency.
3. 3

   Check the thermal rule

   Open the tile’s Settings. Thermal limit chooses how the driver’s power rating becomes a heat ceiling, and Voice coil temperature (20–300 °C) models a hot coil. Xmax applies in every rule.

Where an SPL curve rises above the Max SPL line, that power asks for more than the design can give. Here that first happens at 100 W, below 11.8 Hz; at 1000 W it is below 27.4 Hz. Low down the line is set by Xmax, so it is the cone that runs out first. The Max SPL line itself does not move with Input power or EQ: at 50 Hz it reads 117.9 dB at 10 W and at 1000 W.

Check a listening level: Headroom#

Max SPL answers “how loud at most”. Headroom answers “can it play this level cleanly”, for music with peaks above its average, and it counts every limit, port air speed included.

1. 1

   Add the tile

   Add Headroom with Add tile.
2. 2

   Set the target

   Open its Settings. Under Target level, Average starts at the level the design already plays, at its loudest point. Crest is how far the peaks rise above the average, 12 dB unless you change it, and Distance is where you listen, 1 m to start with.
3. 3

   Read the bands

   The coloured bands are what the design can play at each frequency: Clean, then Threshold, then Over max. Its average level is the solid line and its peaks the dashed one, drawn red where they are over the limit; Tgt avg and Tgt peak mark your target. Wherever the dashed line leaves the clean band, a limit is in the way.

What limits what#

Which limit comes first depends on the design and the frequency. The vented example runs out of cone travel below its 32 Hz tuning and of port air speed at it, long before its voice coil gets hot. Read the limits at the power you mean to use.

Ask your AI#

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