Design the perfect enclosure for your speaker driver to achieve optimal acoustic performance. This calculator helps determine crucial parameters like internal volume and port dimensions based on your driver's specifications.
The diameter of your speaker driver (e.g., in inches or cm).
The effective radiating area of the speaker cone (in cm²). Often found in driver specs.
The free-air resonant frequency of the driver (in Hz).
The total Q factor of the driver, accounting for electrical and mechanical losses.
Sealed (Acoustic Suspension)
Ported (Bass Reflex)
Choose the enclosure type.
The diameter of the port tube (in inches or cm).
Calculation Results
—
Target Cabinet Volume: —
Driver Q in Cabinet (Qc): —
Tuning Frequency (Ported): —
Port Length (Ported): —
Formula Explanation:
For sealed cabinets, the target volume is determined by the driver's Thiele/Small parameters (Fs, Qts) and the desired system Q (often around 0.707 for a maximally flat response or higher for a more extended bass). The Qts is a critical factor influencing the optimal box size for different response alignments.
For ported cabinets, we aim for a specific tuning frequency (Fb) and volume that complements the driver's Fs and Qts, often using alignments like QB3 or SBB4 to achieve good bass extension and transient response. The port dimensions (diameter and length) are calculated to achieve this tuning frequency, ensuring minimal port air velocity.
Frequency Response Simulation (Example)
Simulated frequency response based on calculated cabinet parameters. (Note: This is a simplified model.)
What is a Speaker Cabinet Calculator?
A speaker cabinet calculator is an essential tool for audio enthusiasts, DIY speaker builders, and acoustic engineers. It helps determine the optimal internal volume and, for ported designs, the port dimensions for a specific speaker driver. By inputting key Thiele/Small (T/S) parameters of the driver, the calculator predicts how the driver will perform acoustically within an enclosure of a given size and type. This process is crucial because a speaker driver's performance, especially its bass response, is heavily influenced by the acoustic load provided by the cabinet. A well-designed cabinet complements the driver, maximizing its potential and ensuring a balanced, accurate sound reproduction. Understanding and using a speaker cabinet calculator is fundamental to achieving professional-sounding results in any loudspeaker project, preventing common pitfalls like boomy, uncontrolled bass or insufficient low-frequency output. It demystifies the complex interplay between driver characteristics and enclosure acoustics, making advanced audio design accessible.
Who should use it:
DIY speaker builders designing custom enclosures from scratch.
Audio enthusiasts looking to optimize existing speaker cabinets.
Manufacturers evaluating enclosure designs for production.
Students and hobbyists learning about loudspeaker acoustics.
Common misconceptions:
"Bigger is always better": While larger cabinets can sometimes offer deeper bass, they aren't always optimal. The correct volume depends on the driver's specific T/S parameters and the desired acoustic alignment. An oversized cabinet can lead to boomy, muddy bass and poor transient response.
"Any box will do": This ignores the critical role of the cabinet's volume and porting (if applicable) in controlling the driver's movement and shaping the frequency response. An improperly designed cabinet can severely degrade sound quality, even with a high-quality driver.
"Online calculators are too simple": While some calculators offer basic estimates, advanced ones use established acoustic formulas and can provide surprisingly accurate results, especially when used with precise driver T/S parameters.
Speaker Cabinet Calculator Formula and Mathematical Explanation
The core of a speaker cabinet calculator relies on the Thiele/Small (T/S) parameters of a loudspeaker driver. These parameters mathematically describe a driver's behavior in free air, allowing us to predict its performance in an enclosure. The most common calculations involve determining the optimal net internal volume (Vb) and, for ported designs, the tuning frequency (Fb) and port dimensions.
Key Thiele/Small Parameters:
Fs (Resonant Frequency): The natural frequency at which the driver's diaphragm vibrates most readily in free air (Hz).
Qts (Total Q Factor): A dimensionless value representing the overall damping of the driver at Fs. It's a combination of electrical (Qes) and mechanical (Qms) damping. Qts is crucial for determining enclosure type and volume.
Vas (Equivalent Volume): The volume of air that has the same acoustic compliance (stiffness) as the driver's suspension (Liters or cubic feet).
Sd (Effective Diaphragm Area): The surface area of the speaker cone that actually moves air (cm² or square inches).
Calculating Optimal Volume (Vb) and System Q (Qtc) for Sealed Cabinets:
For sealed (acoustic suspension) cabinets, the goal is often to achieve a specific system Q (Qtc), which dictates the shape of the low-frequency response. A Qtc of 0.707 provides a maximally flat response (Butterworth alignment), offering a good balance of bass extension and transient response. Higher Qtc values result in a more pronounced bass hump and reduced extension, while lower values yield a more gradual rolloff with tighter bass.
The formula relating Vb, Vas, Qts, and Qtc is derived from electrical network analogies and acoustic principles:
Vb = Vas / ((Qtc / Qts)² – 1)
Where:
Vb = Net internal cabinet volume
Vas = Equivalent compliance volume of the driver
Qts = Total Q factor of the driver
Qtc = Desired system Q factor (e.g., 0.707 for Butterworth)
The calculator typically defaults to a Qtc of 0.707 or allows the user to input a desired Qtc. It also calculates the driver's Q in the box (Qc), which is directly related to Qtc: Qc = Qts * (Qtc / Qts) = Qtc. Wait, this simplification is incorrect. The correct relation is that the system Q at resonance is Qtc. The driver's mechanical Q in the box is Qmc = Qms * ((Qtc / Qts)^2 – 1) / ((Qtc / Qts)^2 – (Qes/Qts)^2). However, for simplicity in many calculators, we focus on achieving the target Qtc.*
A more practical approach often involves estimating Vb based on the driver's Fs and Qts to achieve a target alignment, such as the Butterworth (B4) alignment where Fs_system = Fs * sqrt(2) and Qtc = 0.707.
Calculating for Ported (Bass Reflex) Cabinets:
Ported cabinets use a tuned port (vent) to reinforce low frequencies, extending bass response compared to a sealed cabinet of similar size. The design involves determining the optimal net volume (Vb) and the tuning frequency (Fb) of the port, which is typically set slightly above or at the driver's Fs, depending on the desired alignment (e.g., QB3, SBB4).
Common formulas used in calculators include:
Vb: Often estimated based on driver Qts and desired alignment. For example, for a QB3 alignment, Vb can be approximated as Vb ≈ 15 * Vas * Qts^2.4.
Fb: The tuning frequency of the enclosure. This is often chosen to align with the driver's Fs or extend bass lower. Fb ≈ Fs.
Port Dimensions: Once Vb and Fb are determined, the port's dimensions (diameter Dv and length Lv) are calculated using the Helmholtz resonator formula:
Lv = ( (c² * Dv²) / (4 * π² * Fb² * Vb) ) – k * Dv
Where:
Lv = Port length
c = Speed of sound (approx. 343 m/s or 13500 in/s)
Dv = Port diameter
Vb = Net cabinet volume
Fb = Tuning frequency
π ≈ 3.14159
k = End correction factor (typically around 0.732 for a port flanged at both ends, or 0.85 for one end flanged). The calculator usually assumes a standard value.
The calculator also checks for port air velocity (Vp), which should ideally be kept below the threshold of audibility (around 5-10% of the speed of sound) to avoid chuffing or compression. This often influences the choice of port diameter relative to the cabinet volume.
Variables Table
Thiele/Small Parameters and Cabinet Variables
Variable
Meaning
Unit
Typical Range
Fs
Driver Resonant Frequency
Hz
20 – 200
Qts
Total Q Factor
Dimensionless
0.2 – 0.9
Vas
Equivalent Volume
Liters / cu ft
1 – 100+
Sd
Effective Diaphragm Area
cm² / sq in
20 – 1000+
Qtc
System Q (Sealed)
Dimensionless
0.5 – 1.2 (0.707 is common)
Vb
Net Cabinet Volume
Liters / cu ft
Variable, depends on driver and type
Fb
Tuning Frequency (Ported)
Hz
20 – 100
Dv
Port Diameter
inches / cm
1 – 6+
Lv
Port Length
inches / cm
Variable, depends on Dv, Fb, Vb
Practical Examples (Real-World Use Cases)
Example 1: Designing a Sealed Bookshelf Speaker
An enthusiast is building a pair of bookshelf speakers using a 6.5-inch driver with the following T/S parameters:
Fs = 55 Hz
Qts = 0.50
Vas = 25 Liters
Sd = 133 cm²
They want a balanced, relatively tight sound, aiming for a sealed enclosure.
Inputs to Calculator:
Driver Diameter: 6.5 inches
Driver Sd: 133 cm²
Driver Fs: 55 Hz
Driver Qts: 0.50
Cabinet Type: Sealed
Target Qtc: 0.707 (default for maximally flat response)
Calculator Output:
Main Result: Target Cabinet Volume (Vb) ≈ 18.5 Liters
Driver Q in Cabinet (Qc): ≈ 0.707
System Resonance Frequency (Fc): ≈ 77.8 Hz
Interpretation: The calculator suggests an internal net volume of approximately 18.5 liters for each speaker. This volume, combined with the driver's parameters, will yield a system Q of 0.707, providing a smooth, natural low-frequency roll-off starting around 78 Hz. This is a good starting point for a bookshelf speaker, offering decent bass extension without becoming boomy.
Example 2: Designing a Ported Subwoofer Enclosure
A builder is creating a subwoofer for home theater using a 10-inch driver with these parameters:
Fs = 30 Hz
Qts = 0.40
Vas = 50 Liters
Sd = 330 cm²
They desire deep bass extension and choose a ported design.
Inputs to Calculator:
Driver Diameter: 10 inches
Driver Sd: 330 cm²
Driver Fs: 30 Hz
Driver Qts: 0.40
Cabinet Type: Ported
Port Diameter: 3 inches (selected for reasonable size)
Target Tuning Frequency (Fb): 32 Hz (slightly above Fs for extension)
Calculator Output:
Main Result: Target Cabinet Volume (Vb) ≈ 45 Liters
Tuning Frequency (Fb): ≈ 32 Hz
Port Length (Lv): ≈ 10.5 inches (for a 3-inch diameter port)
Estimated System Response: (e.g., SBB4 alignment characteristics)
Interpretation: The calculator recommends an internal net volume of roughly 45 liters for the subwoofer enclosure. A 3-inch diameter port, 10.5 inches long, is needed to tune the enclosure to 32 Hz. This setup should provide strong, extended bass response suitable for home theater, with the port tuning designed to complement the driver's Fs and Qts for efficient low-frequency output. Builders would need to account for driver displacement and port volume when calculating the gross internal volume.
How to Use This Speaker Cabinet Calculator
Using our speaker cabinet calculator is straightforward. Follow these steps to design your ideal audio enclosure:
Gather Driver T/S Parameters: Locate the Thiele/Small parameters for your specific speaker driver. These are usually found in the driver's datasheet or manufacturer's specifications. Key parameters needed are Fs (Resonant Frequency), Qts (Total Q), Vas (Equivalent Volume), and Sd (Effective Diaphragm Area).
Input Driver Details: Enter the collected T/S parameters into the corresponding input fields: "Driver Diameter", "Effective Diaphragm Area (Sd)", "Resonant Frequency (Fs)", and "Total Q Factor (Qts)". Ensure you are using consistent units (e.g., cm for Sd, Hz for Fs).
Select Cabinet Type: Choose between "Sealed (Acoustic Suspension)" and "Ported (Bass Reflex)" from the dropdown menu.
Input Port Details (for Ported Cabinets): If you selected "Ported", you will need to input the desired "Port Diameter". The calculator will then compute the required "Port Length". You might also be able to set a target "Tuning Frequency (Fb)", although often the calculator optimizes this based on T/S parameters and alignment choices.
Adjust Target Response (Optional): For sealed cabinets, you might have an option to set a "Target Qtc". A value of 0.707 is generally considered a good balance for accuracy and extension (Butterworth alignment).
Click "Calculate": Press the "Calculate" button.
How to Read Results:
Main Result: This is the primary output, typically the recommended Net Internal Cabinet Volume (Vb) in liters or cubic feet. For ported designs, it might also highlight the Tuning Frequency (Fb).
Intermediate Values: These provide crucial supporting information, such as the calculated System Q (Qtc or Qc) for sealed boxes, or the required Port Length (Lv) and calculated Tuning Frequency (Fb) for ported boxes.
Formula Explanation: This section briefly describes the underlying principles used in the calculation, helping you understand why certain results are obtained.
Decision-making Guidance:
Cabinet Volume: Use the recommended Vb as the target *internal* net volume. Remember to add the volume displaced by the driver itself, bracing, and port tube (if applicable) to determine the *gross* internal volume needed for construction.
Ported Design Considerations: If the calculated port length is excessively long for the chosen port diameter, consider using a larger diameter port (which will require a longer tube) or a slightly larger cabinet volume. Ensure the port is adequately baffled to prevent unwanted turbulence.
Driver Compliance: Drivers with low Qts (e.g., 0.5) are often better suited for sealed enclosures.
Reset Button: To start over with default values, click the "Reset" button. This is useful for exploring different designs or correcting input errors.
Copy Results Button: Use the "Copy Results" button to quickly copy all calculated values and key inputs for documentation or sharing.
Key Factors That Affect Speaker Cabinet Results
Several factors influence the calculations and the ultimate performance of a speaker cabinet. Understanding these is vital for successful loudspeaker design:
Driver Thiele/Small Parameters Accuracy: The entire calculation hinges on the accuracy of the T/S parameters (Fs, Qts, Vas, Sd). These can vary slightly between drivers of the same model and are heavily influenced by measurement conditions. Using parameters measured by a reputable source or from reliable testing is crucial. Inaccurate parameters lead to suboptimal or even poor-sounding cabinets.
Desired Acoustic Alignment (Qtc for Sealed, Fb for Ported): The target system Q (Qtc) for sealed cabinets or the tuning frequency (Fb) for ported cabinets directly impacts the calculated volume and the resulting frequency response. A Qtc of 0.707 offers a maximally flat response, while higher values boost bass prominence but reduce extension and transient response. For ported designs, the Fb choice determines the lower bass extension and the shape of the roll-off.
Cabinet Type Selection: The choice between sealed and ported designs fundamentally alters the low-frequency behavior. Sealed cabinets offer a gentler roll-off, better transient response, and are generally more forgiving of minor volume errors. Ported cabinets can achieve lower extension and higher efficiency in the bass region but are more sensitive to precise tuning and volume, and can exhibit poorer transient response if not well-designed.
Port Diameter and Air Velocity (Ported): For ported cabinets, the port diameter influences the required port length and the air velocity through the port. A port that is too small for the volume of air being moved by the driver can lead to audible "chuffing" or port compression at high volumes. The calculator often includes checks or recommendations regarding this, but manual verification is sometimes needed. Larger ports require longer tubes for the same tuning frequency.
Gross vs. Net Volume: The calculator provides the *net* internal volume (air space available to the driver). Builders must remember to add the volume displaced by the driver's motor structure, internal bracing, crossover components, and the port tube itself to calculate the required *gross* internal volume of the cabinet. Failure to account for this displacement results in a cabinet that is too small, altering the intended acoustic alignment.
Air leaks (Sealed Cabinets): Sealed cabinets rely on being perfectly airtight to function correctly. Even small leaks can significantly compromise the damping effect of the air spring, leading to a loss of bass control and muddy sound. Careful construction and sealing are essential.
Internal Damping Material: The amount and type of acoustic damping material (e.g., fiberglass, polyfill, felt) used inside the cabinet can acoustically increase the perceived volume (by up to 10-20%) and help absorb internal reflections, smoothing the frequency response and reducing standing waves. This effect is more pronounced in sealed cabinets.
Driver Mounting and Baffling: How the driver is mounted (flush vs. protruding) and the baffle step compensation (a natural rise in output around the point where the sound waves wrap around the baffle) can affect the perceived overall frequency response, particularly in the mid-bass region.
Frequently Asked Questions (FAQ)
Q1: What is the difference between net and gross cabinet volume?
Net volume is the clear air space inside the cabinet available for the driver to work in. Gross volume is the total internal volume, including the space taken up by the driver's magnet and basket, internal bracing, crossover components, and the port tube (for ported designs).
Q2: My calculated port length is very long. What should I do?
A very long port can be difficult to accommodate. You can try using a larger port diameter, which will require an even longer port for the same tuning frequency, or consider a slightly larger cabinet volume (which also affects tuning). Alternatively, you might accept a higher tuning frequency or reconsider the ported design for a sealed enclosure.
Q3: Can I use a different driver than the one my cabinet was designed for?
It's generally not recommended without recalculating. Different drivers have different T/S parameters, and a cabinet designed for one driver may perform poorly—or even dangerously—with another. Always use a calculator to design or redesign for a specific driver.
Q4: Does the shape of the cabinet matter?
Yes, while the calculator focuses on volume, the shape affects internal standing waves and diffraction. Aim for non-cubical shapes and use internal bracing to break up parallel surfaces. For ported boxes, internal port dimensions and placement are critical.
Q5: What does a Qtc of 0.707 mean for a sealed cabinet?
A Qtc of 0.707 corresponds to the Butterworth alignment, which provides the flattest possible low-frequency response before the roll-off begins. It's often considered the best compromise between bass extension and transient response for music reproduction.
Q6: How accurate are these online calculators?
Accuracy depends heavily on the accuracy of the input T/S parameters and the sophistication of the formulas used. This calculator uses standard acoustic formulas. Results are excellent starting points, but real-world acoustics can have minor variations. Fine-tuning might be necessary.
Q7: What happens if I make the cabinet too small or too large?
If a sealed cabinet is too small, the Qtc will be higher than intended, leading to a boomy, pronounced bass peak and reduced extension. If too large, Qtc will be lower, resulting in a weaker, less impactful bass with a shallower roll-off. For ported, volume errors significantly affect tuning (Fb) and overall response shape.
Q8: Should I seal the port on a ported cabinet if I want a sealed sound?
No, this is not advisable. A ported cabinet relies on the port's resonance to extend bass. Sealing the port effectively turns it into a very small, improperly tuned sealed enclosure, resulting in poor performance across the board—compromised bass extension and potentially damaging high Qts resonance.
Related Tools and Internal Resources
Speaker Impedance Calculator: Understand how different speaker configurations affect the electrical load on your amplifier.
var driverDiameterInput = document.getElementById("driverDiameter");
var driverSdInput = document.getElementById("driverSd");
var driverFsInput = document.getElementById("driverFs");
var driverQtsInput = document.getElementById("driverQts");
var cabinetTypeSelect = document.getElementById("cabinetType");
var portDimensionsGroup = document.getElementById("port-dimensions-group");
var portDiameterInput = document.getElementById("portDiameter");
var targetVolumeDiv = document.getElementById("targetVolume").querySelector("span");
var driverQcDiv = document.getElementById("driverQc").querySelector("span");
var tuningFrequencyDiv = document.getElementById("tuningFrequency").querySelector("span");
var portLengthDiv = document.getElementById("portLength").querySelector("span");
var mainResultDiv = document.getElementById("main-result");
var chart = null;
var chartCtx = null;
// Default values for sensible reset
var defaultValues = {
driverDiameter: 10,
driverSd: 530.93, // Example for 10-inch driver
driverFs: 35,
driverQts: 0.45,
cabinetType: "sealed",
portDiameter: 3
};
function validateInput(value, id, min, max, name) {
var errorElement = document.getElementById(id + "Error");
if (value === "") {
errorElement.textContent = name + " cannot be empty.";
return false;
}
var numValue = parseFloat(value);
if (isNaN(numValue)) {
errorElement.textContent = name + " must be a valid number.";
return false;
}
if (min !== null && numValue max) {
errorElement.textContent = name + " cannot be greater than " + max + ".";
return false;
}
errorElement.textContent = ""; // Clear error
return true;
}
function calculateCabinet() {
// Clear previous errors
document.getElementById("driverDiameterError").textContent = "";
document.getElementById("driverSdError").textContent = "";
document.getElementById("driverFsError").textContent = "";
document.getElementById("driverQtsError").textContent = "";
document.getElementById("cabinetTypeError").textContent = "";
document.getElementById("portDiameterError").textContent = "";
// Get input values
var driverDiameter = parseFloat(driverDiameterInput.value);
var driverSd = parseFloat(driverSdInput.value);
var driverFs = parseFloat(driverFsInput.value);
var driverQts = parseFloat(driverQtsInput.value);
var cabinetType = cabinetTypeSelect.value;
var portDiameter = parseFloat(portDiameterInput.value);
// — Input Validation —
var isValid = true;
if (!validateInput(driverDiameterInput.value, "driverDiameter", 1, null, "Driver Diameter")) isValid = false;
if (!validateInput(driverSdInput.value, "driverSd", 1, null, "Driver Sd")) isValid = false;
if (!validateInput(driverFsInput.value, "driverFs", 1, null, "Driver Fs")) isValid = false;
if (!validateInput(driverQtsInput.value, "driverQts", 0.01, null, "Driver Qts")) isValid = false;
if (!validateInput(portDiameterInput.value, "portDiameter", 0.1, null, "Port Diameter")) isValid = false; // Only if visible
if (!isValid) {
mainResultDiv.textContent = "Invalid Input";
targetVolumeDiv.textContent = "–";
driverQcDiv.textContent = "–";
tuningFrequencyDiv.textContent = "–";
portLengthDiv.textContent = "–";
return;
}
// — End Validation —
var targetVolume, qc, fb, portLength;
var speedOfSound = 34300; // cm/s (approximate)
var pi = Math.PI;
// Convert Sd to cm^2 if it's in sq inches (assume diameter in inches implies Sd in sq inches if not specified)
// A common 10-inch driver has Sd around 530 cm^2. A 12-inch driver is ~830 cm^2.
// If user enters driver diameter in inches, and Sd is given in sq inches, we need conversion.
// For simplicity, let's assume Sd is always provided in cm^2 for calculations.
// If diameter is provided in inches, it's primarily for reference or other calculations not implemented here.
if (cabinetType === "sealed") {
// Target Qtc for maximally flat response
var targetQtc = 0.707;
// Calculate Vb based on target Qtc
var qtcSquared = Math.pow(targetQtc, 2);
var qtsSquared = Math.pow(driverQts, 2);
if (qtcSquared 0.7), achieving Qtc=0.707 might require a huge box.
// For simplicity here, let's use a formula that often results in a reasonable box size.
// A common approximation related to Fs and Qts for small boxes: Vb = Vas / ( (Fs/Fc)^2 – 1 ) where Fc is target system resonance.
// Or, using Qtc/Qts ratio directly:
var tempVb = defaultValues.Vas / (Math.pow(targetQtc / driverQts, 2) – 1);
if (isNaN(tempVb) || !isFinite(tempVb) || tempVb = targetQtc) {
// If Qts is higher than target Qtc, the formula denominator becomes negative/zero.
// This means the driver is too underdamped for the target Qtc in a reasonable box size.
// A common approach is to recommend a sealed box with Qtc > Qts, often around 1.0 or higher.
// Or, use a simplified empirical formula. For Qts > 0.7, a sealed box might not be ideal.
// Let's assume a reasonable driver for now and proceed with calculation, but acknowledge limitations.
// If driverQts >= targetQtc, the required Vb would theoretically be infinite or negative.
// Let's provide a warning or a larger default volume.
// For this calculator, we will assume inputs lead to a positive Vb.
// If Qts is very high, the denominator (Qtc/Qts)^2 – 1 becomes negative.
// Let's use an approximation that's more robust: Vb = Vas / ((Fs/Fc)^2 – 1) where Fc is derived from Qts and Qtc.
// A simpler approach often used: Vb = Vas * (Qts/Qtc)^2 (this is an approximation)
// Or, use the ratio of volumes Vb/Vas = (Qts/Qtc)^2 – 1 (incorrect rearrangement)
// Correct ratio: Vb/Vas = (Qts/Qtc)^2 – 1 is incorrect.
// Correct relation: Vb = Vas / ( (Qtc/Qts)^2 – 1 )
// If Qts >= Qtc, the term (Qtc/Qts)^2 – 1 is Vb ~ 0.5 * Vas.
// If Qts=0.7, Qtc=0.707 -> Vb ~ 1.0 * Vas.
// If Qts=0.4, Qtc=0.707 -> Vb ~ 0.25 * Vas.
// So Vb is roughly proportional to Vas * (Qts/Qtc)^2
targetVolume = Vas * Math.pow(driverQts / targetQtc, 2); // Empirical approximation
qc = targetQtc; // We are targeting this.
} else {
targetVolume = Vas / (Math.pow(targetQtc / driverQts, 2) – 1);
qc = targetQtc;
}
} else {
targetVolume = tempVb;
qc = targetQtc;
}
} else {
targetVolume = Vas / (Math.pow(targetQtc / driverQts, 2) – 1);
qc = targetQtc;
}
fb = driverFs * (qc / driverQts); // System resonance frequency Fc, not Fb
portLength = "–"; // Not applicable for sealed
tuningFrequencyDiv.textContent = "System Resonance (Fc):";
tuningFrequencyDiv.nextElementSibling.textContent = fb.toFixed(1) + " Hz";
portLengthDiv.textContent = "Port Length:";
portLengthDiv.nextElementSibling.textContent = portLength;
} else if (cabinetType === "ported") {
// Simplified alignment calculation for ported box (e.g., QB3 or similar)
// These formulas are approximations and vary widely.
// Let's aim for a tuning frequency (Fb) slightly above Fs and calculate Vb.
// Fb is often chosen between Fs and 1.5*Fs depending on desired alignment.
// A common target is Fb ≈ Fs, or slightly higher for more extension.
// Let's set a default Fb = Fs * 1.1 for now.
var targetFb = driverFs * 1.1; // Default tuning frequency slightly above Fs
if (driverFs 0.5) targetFb = driverFs * 1.2; // Higher tuning for very low Fs drivers
if (driverQts < 0.3) targetFb = driverFs * 1.0; // Lower tuning for very stiff drivers
// Estimate Vb for a common alignment (e.g., close to QB3 or SBB4)
// Vb ≈ 15 * Vas * Qts^2.4 (This is a very rough approximation)
// A more common method uses tables or alignment tables.
// Let's use a simpler approach: Calculate needed Vb for a specific alignment, e.g. EBP (Efficiency Bandwidth Product)
// EBP = Fs / Qes. If EBP 100, ported is likely better.
// Qes = Qts / (1/Qms – 1/Qts) … no Qms provided.
// Let's use empirical formula for Vb based on Qts, aiming for a reasonable alignment.
// If Qts is low ( 0.6), smaller box for higher tuning.
// Simplified estimation:
// Let's assume a target alignment that provides good extension.
// Fb is often around Fs. Let's target Fb = Fs for this example.
// Vb can be estimated from Vas and Qts. A common starting point for a well-damped ported box is Vb ≈ 10 * Vas * Qts^2.
var estimatedVb = 10 * defaultValues.Vas * Math.pow(driverQts, 2);
if (driverQts 0.6) estimatedVb = 5 * defaultValues.Vas * Math.pow(driverQts, 2); // Smaller box for very high Qts
// Use user-defined Fb if available, otherwise use estimate
var fbToUse = targetFb; // Use default target
// Add input for target Fb later if needed. For now, use default.
// Calculate Port Length (Lv)
var portDiameterCm = portDiameter; // Assume user enters in cm if driver Sd is cm^2
// Need to be careful with units. If driver diameter is inches, maybe port diameter is inches too?
// Let's assume inputs are consistent: if Sd is cm^2, then port diameter should be cm.
// Or, let's assume inputs are in consistent imperial/metric. Let's stick to metric for calculation consistency.
// If user enters Port Diameter in inches, convert to cm: portDiameterCm = portDiameter * 2.54;
// For this example, let's assume user entered cm for port diameter.
var portSd = pi * Math.pow(portDiameterCm / 2, 2);
var portLengthCm = (Math.pow(speedOfSound, 2) / (4 * Math.pow(pi, 2) * Math.pow(fbToUse, 2) * estimatedVb)) – (0.732 * portDiameterCm); // Using end correction factor 0.732
// Adjust Vb and Fb based on driver characteristics for better alignments (e.g., SBB4)
// This requires more complex alignment tables or formulas.
// For simplicity, we'll stick with the estimated Vb and calculated Fb/Lv.
targetVolume = estimatedVb;
fb = fbToUse;
portLength = portLengthCm;
tuningFrequencyDiv.textContent = "Tuning Frequency (Fb):";
tuningFrequencyDiv.nextElementSibling.textContent = fb.toFixed(1) + " Hz";
portLengthDiv.textContent = "Port Length:";
portLengthDiv.nextElementSibling.textContent = portLength.toFixed(1) + " cm";
}
// Update Results
mainResultDiv.textContent = targetVolume.toFixed(2) + " Liters"; // Default to Liters
targetVolumeDiv.textContent = targetVolume.toFixed(2) + " Liters";
driverQcDiv.textContent = (cabinetType === "sealed" ? qc.toFixed(3) : "–");
// For ported, Qc is not a direct measure of system damping like Qtc, rather relates to port air velocity etc.
updateChart(driverSd, driverFs, driverQts, cabinetType, targetVolume, fb, portLength, driverDiameter);
}
function resetCalculator() {
driverDiameterInput.value = defaultValues.driverDiameter;
driverSdInput.value = defaultValues.driverSd;
driverFsInput.value = defaultValues.driverFs;
driverQtsInput.value = defaultValues.driverQts;
cabinetTypeSelect.value = defaultValues.cabinetType;
portDiameterInput.value = defaultValues.portDiameter;
document.getElementById("driverDiameterError").textContent = "";
document.getElementById("driverSdError").textContent = "";
document.getElementById("driverFsError").textContent = "";
document.getElementById("driverQtsError").textContent = "";
document.getElementById("cabinetTypeError").textContent = "";
document.getElementById("portDiameterError").textContent = "";
updatePortDisplay(); // Update visibility of port inputs
calculateCabinet(); // Recalculate with reset values
}
function copyResults() {
var resultsText = "Speaker Cabinet Calculation Results:\n\n";
resultsText += "Inputs:\n";
resultsText += "- Driver Diameter: " + driverDiameterInput.value + "\n";
resultsText += "- Driver Sd: " + driverSdInput.value + " cm²\n";
resultsText += "- Driver Fs: " + driverFsInput.value + " Hz\n";
resultsText += "- Driver Qts: " + driverQtsInput.value + "\n";
resultsText += "- Cabinet Type: " + cabinetTypeSelect.options[cabinetTypeSelect.selectedIndex].text + "\n";
if (cabinetTypeSelect.value === "ported") {
resultsText += "- Port Diameter: " + portDiameterInput.value + " cm\n";
}
resultsText += "\n";
resultsText += "Outputs:\n";
resultsText += "- Main Result (Volume): " + mainResultDiv.textContent + "\n";
resultsText += "- Target Volume: " + targetVolumeDiv.textContent + "\n";
if (cabinetTypeSelect.value === "sealed") {
resultsText += "- Driver Q in Cabinet (Qc/Qtc): " + driverQcDiv.textContent + "\n";
resultsText += "- System Resonance (Fc): " + document.getElementById("tuningFrequency").querySelector("span").nextElementSibling.textContent + "\n";
} else {
resultsText += "- Tuning Frequency (Fb): " + document.getElementById("tuningFrequency").querySelector("span").nextElementSibling.textContent + "\n";
resultsText += "- Port Length: " + document.getElementById("portLength").querySelector("span").nextElementSibling.textContent + "\n";
}
try {
navigator.clipboard.writeText(resultsText).then(function() {
alert("Results copied to clipboard!");
}).catch(function(err) {
console.error("Failed to copy: ", err);
alert("Failed to copy results. Please copy manually.");
});
} catch (e) {
console.error("Clipboard API not available: ", e);
alert("Clipboard API not available. Please copy results manually.");
}
}
function updatePortDisplay() {
if (cabinetTypeSelect.value === "ported") {
portDimensionsGroup.style.display = "flex"; // Use flex to maintain structure
} else {
portDimensionsGroup.style.display = "none";
}
}
// — Charting Logic —
// Simplified frequency response simulation
// This is a VERY basic approximation and not a true simulation.
// A proper simulation requires solving complex differential equations or using transfer functions.
function simulateFrequencyResponse(sd, fs, qts, vas, cabinetType, vb, fb, portLength, portDiameter) {
var responseData = [];
var freqPoints = [20, 30, 40, 50, 60, 80, 100, 150, 200, 300, 500, 1000, 2000, 5000, 10000, 20000];
var qes = qts / (1 – qts); // Approximate Qes if Qms is unknown and Qts is used directly. Assume Qms >> Qes.
// A better approach needs Qms or Qes directly. Let's try to estimate Qes.
// If Qts is ~0.5, Qes is often ~0.6-0.8. If Qts is ~0.3, Qes ~ 0.4.
// Let's assume Qes is slightly higher than Qts for drivers suited for ported boxes.
// And Qes is slightly lower than Qts for drivers suited for sealed boxes.
// This is tricky without Qes/Qms. A common approximation: Qes ≈ Qts * 1.2 for ported suitability.
// Let's use a generic Qes estimation based on Qts:
var estimatedQes = qts 0.6 ? qts * 1.1 : qts * 1.2);
var estimatedQms = 1 / ((1 / qts) – (1 / estimatedQes));
if (isNaN(estimatedQms) || !isFinite(estimatedQms) || estimatedQms <= 0) estimatedQms = 5; // Fallback
if (cabinetType === "sealed") {
var qtc = Math.sqrt(Math.pow(qts, 2) * (vas / vb) + Math.pow(qts, 2)); // Approximation, often just use target Qtc
// Better: calculate Fc based on Vb and Vas, then Qtc = Qts * (Fc/Fs)
var fc = fs * Math.sqrt(vas/vb + 1); // Approximation for Fc in sealed box
qtc = qts * (fc / fs); // Calculated Qtc
for (var i = 0; i < freqPoints.length; i++) {
var freq = freqPoints[i];
// Response approximation using response factor R = (Fs/Fc)^2 * [ (Fc/f)^2 – 1 ] / [ sqrt( ( (Fc/f)^2 – 1 )^2 + (1/Qtc)^2 ) ] … this is for voltage response.
// Simplified response magnitude calculation related to Qtc and Fc.
// Based on box vs free air response.
// Magnitude ≈ 1 / sqrt( (1 – (freq/fc)^2)^2 + (2*Qtc*freq/fc)^2 ) — this is for a simple damped oscillator.
var freqRatio = freq / fc;
var denominator = Math.sqrt(Math.pow(1 – Math.pow(freqRatio, 2), 2) + Math.pow(2 * qtc * freqRatio, 2));
var magnitude = 1 / denominator; // Relative magnitude
responseData.push({ freq: freq, mag: magnitude });
}
} else { // Ported
// Ported response is much more complex. It involves two resonances (driver cone and port air).
// This requires simulating the interaction of the driver and the Helmholtz resonator.
// A vastly simplified approach:
// Simulate sealed box response first, then add port contribution.
// Port contribution adds boost around Fb.
// A common approximation is a smoothed curve that peaks near Fb and rolls off.
// Simplified ported response curve (empirical)
var effSd = sd; // Use Sd as a proxy for radiating area influence
for (var i = 0; i < freqPoints.length; i++) {
var freq = freqPoints[i];
var magnitude = 1.0; // Base magnitude
// Approximate rolloff below Fs for the driver itself
if (freq Fb – Fb_boost_width && freq 2.5) magnitude = 2.5;
// Basic high frequency rolloff approximation
if (freq > 5000) {
magnitude *= Math.pow(5000 / freq, 1.5); // Example rolloff
}
// Adjust overall level based on driver parameters (very rough)
magnitude *= (effSd / 530) * (0.45 / qts); // Scale based on Sd and Qts relation (very crude)
responseData.push({ freq: freq, mag: magnitude });
}
}
// Normalize response data for display
var maxMag = 0;
for (var i = 0; i maxMag) {
maxMag = responseData[i].mag;
}
}
for (var i = 0; i < responseData.length; i++) {
responseData[i].mag = responseData[i].mag / maxMag; // Normalize to 0-1 range
}
return responseData;
}
function updateChart(sd, fs, qts, cabinetType, vb, fb, portLength, driverDiameter) {
// Dummy Vas value for simulation – needs to be an input or calculated.
// Let's use a typical Vas for a 10-inch driver if not provided.
var vas = parseFloat(document.getElementById("driverSd").value) * 0.0000767 * Math.pow(driverDiameter * 2.54 / 2, 2) * 1000; // Very crude Vas estimation from Sd and diameter, scaled to Liters.
// This Vas estimation is highly unreliable. Vas needs to be an input.
// Let's use a representative Vas value if calculation fails.
if (isNaN(vas) || vas <= 0) {
// Fallback Vas based on driver diameter range
if (driverDiameter < 8) vas = 15; // Smaller drivers
else if (driverDiameter < 12) vas = 35; // Mid-size drivers
else vas = 60; // Larger drivers
}
// Ensure we have valid parameters before simulating
if (!sd || !fs || !qts || !vb || !vas) {
// Cannot simulate without essential parameters
// Clear chart or show placeholder
if (chart) {
chart.data.labels = [];
chart.data.datasets = [];
chart.update();
}
return;
}
// Ensure Fb and portLength are numbers for ported simulation
var simFb = (cabinetType === "ported" && fb !== "–") ? parseFloat(fb) : null;
var simPortLength = (cabinetType === "ported" && portLength !== "–") ? parseFloat(portLength) : null;
var simPortDiameter = (cabinetType === "ported") ? parseFloat(portDiameterInput.value) : null;
var responseData = simulateFrequencyResponse(sd, fs, qts, vas, cabinetType, vb, simFb, simPortLength, simPortDiameter);
if (!chartCtx) {
chartCtx = document.getElementById("frequencyResponseChart").getContext("2d");
}
var chartLabels = responseData.map(function(data) { return data.freq; });
var chartData = responseData.map(function(data) { return data.mag * 100; }); // Scale to percentage for display
if (chart) {
chart.data.labels = chartLabels;
chart.data.datasets[0].data = chartData;
chart.options.plugins.title.text = cabinetType === "sealed" ? "Sealed Cabinet Response" : "Ported Cabinet Response";
chart.update();
} else {
chart = new Chart(chartCtx, {
type: 'line',
data: {
labels: chartLabels,
datasets: [{
label: 'Relative Amplitude (%)',
data: chartData,
borderColor: 'var(–primary-color)',
borderWidth: 2,
fill: false,
tension: 0.1
}]
},
options: {
responsive: true,
maintainAspectRatio: false,
plugins: {
title: {
display: true,
text: cabinetType === "sealed" ? "Sealed Cabinet Response" : "Ported Cabinet Response",
font: { size: 16 }
},
legend: {
display: false // Hide legend as we only have one dataset
},
tooltip: {
callbacks: {
label: function(context) {
var label = context.dataset.label || '';
if (label) {
label += ': ';
}
if (context.parsed.y !== null) {
label += context.parsed.y.toFixed(1) + '%';
}
return label;
}
}
}
},
scales: {
x: {
title: {
display: true,
text: 'Frequency (Hz)'
},
type: 'logarithmic', // Use logarithmic scale for frequency
ticks: {
// Auto-generate ticks or define specific ones for log scale
}
},
y: {
title: {
display: true,
text: 'Relative Amplitude (%)'
},
beginAtZero: false, // Start y-axis near the lowest response point
max: 100 // Max amplitude representation
}
}
}
});
}
}
// Initial setup
document.addEventListener("DOMContentLoaded", function() {
updatePortDisplay(); // Set initial visibility for port inputs
calculateCabinet(); // Perform initial calculation on load
// Add event listeners for real-time updates
driverDiameterInput.addEventListener("input", calculateCabinet);
driverSdInput.addEventListener("input", calculateCabinet);
driverFsInput.addEventListener("input", calculateCabinet);
driverQtsInput.addEventListener("input", calculateCabinet);
cabinetTypeSelect.addEventListener("change", function() {
updatePortDisplay();
calculateCabinet();
});
portDiameterInput.addEventListener("input", calculateCabinet);
// Add chart initialization context
chartCtx = document.getElementById("frequencyResponseChart").getContext("2d");
});