What is coolstocks.net?

⚡ What the site does

coolstocks.net is a free online component calculator that designs the classic 2nd-order Linkwitz Transform circuit. This analog filter technique, invented by Siegfried Linkwitz, lets you reshape the low-frequency response of a loudspeaker or sealed-box subwoofer.

In practice, it takes a speaker’s natural resonance and Q, then electronically “transforms” them into a new, deeper target response — extending bass while controlling damping and rolloff shape.

🎛️ How it works

You simply enter a few parameters and the tool does the rest:

• Choose a convenient value for capacitor C₂ (in nF)
• Click Calculate (or load the built-in 80 Hz → 30 Hz example)
• Instantly get ideal resistor & capacitor values (R1–R3, C1–C3)
• See DC gain, design equations, and an interactive schematic with values overlaid
• View a frequency-response magnitude plot of the ideal transform

The calculated values are theoretical ideals. You can later substitute real-world E-series parts for practical builds.

📐 The math behind it

The site uses the classic Linkwitz Transform design equations:

🎧 Who it’s for

Anyone building or modifying active subwoofers, sealed-box speakers, or custom audio systems who needs precise Linkwitz Transform component values without doing the math by hand.

Clean interface, no ads, no sign-up — just the calculator.