How To Order A Custom Subwoofer Box Design

Ordering a custom subwoofer box design from EZ DB's Designs is easy once you know three things: how deep you want your bass to hit, how much space you have to work with, and which box style fits your goals. This guide walks you through it step by step.

Step 1: Find Your Target Low Frequency

Every song has bass notes, and those notes live at different frequencies. A low frequency (measured in Hertz, or Hz) is how deep the bass plays. Lower numbers = deeper, chest-thumping bass. Higher numbers = punchier, more musical bass.

Pick a song you actually listen to that has the deepest bass you care about — then upload it into the analyzer below. It will tell you the lowest frequency that song is really hitting.

Frequency tool

EZ DB's Bass Frequency Analyzer

Upload a song or rebassed track to see where the strongest bass content lives. This helps point you toward the enclosure style that may best fit your goals.

Upload audio file

Supported: MP3, WAV, M4A, AAC. Files up to 25 MB. Analysis uses a high-resolution FFT for 10–80 Hz.

Waiting for file.

How to use it

Upload a track that represents the lowest bass frequencies you typically listen to.
Look at where the strongest bass peaks land between 10 Hz and 80 Hz.
Use that result to help decide which enclosure type you should choose.

Quick enclosure guide

Sealed: 20 Hz+ — simplest and most compact; favors mid-to-high Qts and low-to-mid EBP drivers.
Ported: 20 Hz+ — larger than sealed with more output; favors low-to-mid Qts and mid-to-high EBP drivers.
4th Order: 22 Hz+ — larger than ported with similar output; favors mid-to-high Qts and low-to-mid EBP drivers.
6th Order: 15 Hz+ — largest of the group with the deepest extension; favors low-to-mid Qts and mid-to-high EBP drivers.
Transmission Line: 20 Hz+ — best for high-Qts, low-Fs subs; delivers flat response and efficient low-end.

Write down the number the analyzer gives you. You'll use it in the next step.

Step 2: Know What You're Trading Off

Every subwoofer box is a trade-off. You can't have everything at once. Here's what that means in plain English:

Deeper bass = bigger box. Playing lower notes takes more air space inside the enclosure.
Louder bass = usually less deep. Boxes designed to be loud often give up some of the deepest notes.
Deeper bass = usually less loud at higher notes. The reverse of the above.
Some box styles depend on the sub you pick. Bandpass and T-Line boxes only work well with certain subwoofers. If you're not sure yours will work, ask before ordering.

Pick what matters most to you: deep low-end, maximum loudness, or a balance of both.

Before Step 3: Understand These Two Sub Specs

Every box style below references two numbers off your sub's spec sheet. Learn them once and the rest of the guide makes sense.

Qts — Total Q of the subwoofer. Single number on the manufacturer's spec sheet under "Thiele-Small" or "T/S Parameters." Also on the spec card that came in the sub box.
EBP — Efficiency Bandwidth Product. Calculated as Fs ÷ Qes (both come from the same T/S sheet). Some brands list EBP directly; if not, punch Fs into a calculator and divide by Qes.

How to use them:

Qts low-to-mid + EBP 50 or higher → Ported and 6th Order Bandpass / Blow-Thru
Qts mid-to-high + EBP 50 or lower → Sealed and 4th Order Bandpass / Blow-Thru
High Qts with low Fs → T-Line

Rough Qts scale: low ≈ under 0.4, mid ≈ 0.4–0.6, high ≈ 0.7 and up.

Step 3: Pick Your Box Style

Use the dropdown below to pick the box style you think fits your goals. Once you pick one, this page will show you the full details for that style, plus Steps 4, 5, and 6 for how to measure and order — and a walkthrough of every field on the product page.

Choose your box style

Not sure which style is right for you? That's okay — a lot of people aren't. Contact EZ DB's Designs before you order and we'll help you figure it out.

Sealed Box

Best for: Systems that need to play about 20 Hz and up.
How it sounds: Tight, accurate, musical. Great for songs where you can hear individual bass notes clearly.
Space needed: Smallest of all the box styles.
Watch out for: Won't hit as hard on the deepest notes as a ported or bandpass box.

Subwoofer Fitness — Does Your Sub Belong In This Box?

Every subwoofer has two numbers on its spec sheet that tell you which box style it belongs in:

Qts — total Q of the sub. One number listed on the manufacturer's spec sheet under "Thiele-Small" or "T/S Parameters" (also on the spec card in the sub's box).
EBP — Efficiency Bandwidth Product. Calculated as Fs ÷ Qes (both come from the same T/S spec sheet). Some brands list EBP directly; if not, divide Fs by Qes on a calculator.

For this style specifically: Sealed likes Qts mid-to-high (roughly 0.4 and up) and EBP 50 or lower. If your sub's EBP is under 50 and its Qts sits in that range, sealed is a natural fit.

Rough Qts scale, if you're new to this: low ≈ under 0.4, mid ≈ 0.4–0.6, high ≈ 0.7 and up.

Not sure if your sub fits? Message us the brand and model before ordering and we'll tell you.

Step 4: Pick Your Layout

The layout is how the box sits in your vehicle and which direction the sub and port face.

Direction words (used when ordering):

Back = toward the rear of the vehicle
Forward = toward the front of the vehicle
Up = toward the roof
Side = toward the driver or passenger side

Common layouts: trunk box, SUV cargo-area box, wall behind the back seat (B-pillar or C-pillar wall), under-seat truck box, behind-seat truck box, center-console truck box.

If you already know the layout you want, tell us in the order. If not, just give us your measurements and your goals and we'll figure the layout out for you.

Step 5: Measure Your Space

Measure the biggest possible empty space where the box will sit. Not the space you want to use — the absolute maximum you have. Bigger measurements mean we can design a better box for you.

You'll need to account for:

Width, height, and depth of the space
How far your seats move back and recline
Anywhere the wheel wells, center console, amps, factory storage, or trim panels stick into the space

Follow the full measurement walkthrough here: How To Pull Your Own Measurements and pick the section that matches your build.

Step 6: Place Your Order

Before you check out, make sure you have all of this ready:

Your vehicle: year, make, and model
Your subwoofer brand, model, and how many you're running
Your measurements (from Step 5)
Your layout preference (from Step 4)
Any extra notes: things in the way, custom fitment concerns, sound-quality vs loudness goals, anything unusual about your car

Product-Page Walkthrough — Every Form Field Explained

Below is every field you'll see on the Sealed Box product page, in order, with what to enter and why.

Subwoofer Brand/Model/VersionRequired

Type the exact brand and model of your sub, plus the version if the model has multiple (like a v.2 or D2 vs D4). Example: Sundown Audio SA-12 v.2 D2. This is how we look up your sub's specs.

Subwoofer SizeRequired

Pick the physical size of your sub in inches (6.5", 8", 10", 12", 13", 15", 16", 18", 19", 21", 24", or 32", up to 32" depending on the product).

How Many Subwoofers?Required

How many of that sub you're running in this box (up to 24 depending on the product). Quantities over 4 have a small add-on ($10 for 5–8, $15 for 9+) — that's shown in the dropdown.

Vehicle Year/Make/ModelRequired

Type your vehicle exactly, like 2020 Toyota Camry SE or 2015 Chevy Silverado 1500 Crew Cab. Trim/cab-style matters — a Crew Cab and an Extended Cab have very different spaces.

Your Wood Sheet ThicknessRequired

Pick the thickness of the wood you're going to build with. Options: 23/32", 3/4", 1", 1-1/4", or 18mm/19mm/22mm metric. If you pick a metric size, your blueprint will come in metric measurements. Standard 3/4" MDF is the default choice if you're not sure.

Are Your Measurements Rectangular or Complex Shaped?Required

Pick Rectangular if the space is a simple box (four flat walls, flat floor, flat ceiling). Pick Complex if any wall or floor is angled, curved, or has stuff sticking into it (wheel wells, humps, trim). Complex adds a small design fee ($10–$25 depending on the product) because it takes more work.

Max Height (Top to Bottom)Required

In inches. The tallest the box can be from bottom to top. Use decimals if needed (like 14.5").

Max Width (Left to Right)Required

In inches. The widest the box can be side to side.

Max Depth (Front to Back)Required

In inches. The deepest the box can go from front to back.

Complex Measurements Shape File UploadRequired

Upload a photo or drawing (up to 5 images) of the space if you picked Complex above. A phone snapshot with numbers written on it works fine — we don't need CAD. Only required if you picked Complex.

Box Type/LocationRequired

Pick the layout that matches where the box will live. Options include: Trunk Box (Sub Back), No-Wall SUV Box, C-Pillar Walled Box, B-Pillar Walled Box, Under-seat Truck Box (Sub Forward/Up/Down), Ext-Cab Behind-seat Truck Box (Sub Up/Down/Forward), and Center Console Box (Sub Up/Down/Back). Direction words describe which way the sub cone faces.

Custom RequestsOptional

Anything you want us to know: preferred port location, inverted vs normal-mount subs, flush mount, plexi windows, tweaks to sub orientation, cutouts you want to avoid, etc. If you left the Box Type dropdown on "Other," describe your sub/port layout here.

I understand I'm buying only enclosure design blueprints (not a physical enclosure), with specifications optimized for my application, and I've read the product description's turnaround time.Required

You have to check this box to place the order. It confirms you know you're getting a blueprint (a set of cut sheets and specs), not a built wooden box shipped to your door.

I understand that if my request isn't physically possible (too much in too little space), my order may be refunded (minus transaction fees) if no workable adjustments can be made.Required

Also required. If the physics don't work — say you want 4x 15"s in a Prius trunk with 20 Hz tuning — we'll reach out, try to find a workable adjustment, and refund if we can't.

I agree that all required design constraints are included in this order form (whether previously discussed or not). Orders missing key constraints are not eligible for free revisions.Required

Also required. If you know something matters — a hump, a bracket, a specific port location — put it on the form. Anything left off is not free to fix later.

Ported Box

Best for: Systems that need to play about 20 Hz and up. Most common choice for daily-driven cars.
How it sounds: Louder than sealed with more deep-bass punch. Good all-around.
Space needed: More than sealed, less than bandpass.
Watch out for: Needs the port (the opening on the box) to breathe properly. If it's blocked or too close to a panel, it won't perform right.

Subwoofer Fitness — Does Your Sub Belong In This Box?

Every subwoofer has two numbers on its spec sheet that tell you which box style it belongs in:

Qts — total Q of the sub. One number listed on the manufacturer's spec sheet under "Thiele-Small" or "T/S Parameters" (also on the spec card in the sub's box).
EBP — Efficiency Bandwidth Product. Calculated as Fs ÷ Qes (both come from the same T/S spec sheet). Some brands list EBP directly; if not, divide Fs by Qes on a calculator.

For this style specifically: Ported likes Qts low-to-mid (roughly 0.6 and under) and EBP 50 or higher. Most subs marketed as "SPL" or "daily driver" fall in this range.

Rough Qts scale, if you're new to this: low ≈ under 0.4, mid ≈ 0.4–0.6, high ≈ 0.7 and up.

Not sure if your sub fits? Message us the brand and model before ordering and we'll tell you.

Step 4: Pick Your Layout

The layout is how the box sits in your vehicle and which direction the sub and port face.

Direction words (used when ordering):

Back = toward the rear of the vehicle
Forward = toward the front of the vehicle
Up = toward the roof
Side = toward the driver or passenger side

Common layouts: trunk box, SUV cargo-area box, wall behind the back seat (B-pillar or C-pillar wall), under-seat truck box, behind-seat truck box, center-console truck box.

If you already know the layout you want, tell us in the order. If not, just give us your measurements and your goals and we'll figure the layout out for you.

Step 5: Measure Your Space

Measure the biggest possible empty space where the box will sit. Not the space you want to use — the absolute maximum you have. Bigger measurements mean we can design a better box for you.

You'll need to account for:

Width, height, and depth of the space
How far your seats move back and recline
Anywhere the wheel wells, center console, amps, factory storage, or trim panels stick into the space

Follow the full measurement walkthrough here: How To Pull Your Own Measurements and pick the section that matches your build.

Step 6: Place Your Order

Before you check out, make sure you have all of this ready:

Your vehicle: year, make, and model
Your subwoofer brand, model, and how many you're running
Your measurements (from Step 5)
Your layout preference (from Step 4)
Any extra notes: things in the way, custom fitment concerns, sound-quality vs loudness goals, anything unusual about your car

Product-Page Walkthrough — Every Form Field Explained

Below is every field you'll see on the Ported Box product page, in order, with what to enter and why.

Subwoofer Brand/Model/VersionRequired

Type the exact brand and model of your sub, plus the version if the model has multiple (like a v.2 or D2 vs D4). Example: Sundown Audio SA-12 v.2 D2. This is how we look up your sub's specs.

Subwoofer SizeRequired

Pick the physical size of your sub in inches (6.5", 8", 10", 12", 13", 15", 16", 18", 19", 21", 24", or 32", up to 32" depending on the product).

How Many Subwoofers?Required

How many of that sub you're running in this box (up to 24 depending on the product). Quantities over 4 have a small add-on ($10 for 5–8, $15 for 9+) — that's shown in the dropdown.

Vehicle Year/Make/ModelRequired

Type your vehicle exactly, like 2020 Toyota Camry SE or 2015 Chevy Silverado 1500 Crew Cab. Trim/cab-style matters — a Crew Cab and an Extended Cab have very different spaces.

Your Wood Sheet ThicknessRequired

Are Your Measurements Rectangular or Complex Shaped?Required

Max Height (Top to Bottom)Required

In inches. The tallest the box can be from bottom to top. Use decimals if needed (like 14.5").

Max Width (Left to Right)Required

In inches. The widest the box can be side to side.

Max Depth (Front to Back)Required

In inches. The deepest the box can go from front to back.

Complex Measurements Shape File UploadRequired

Upload a photo or drawing (up to 5 images) of the space if you picked Complex above. A phone snapshot with numbers written on it works fine — we don't need CAD. Only required if you picked Complex.

Measurement Type (Are you measuring inside a pre-existing shell, or an empty space?)Required

Pick External if there's no shell yet — you're measuring open-air space. Pick Internal (No front or back) if the shell exists but neither front nor back panel is on. Pick Internal (Back Installed, No Front) if the back panel is in but the front is open. This tells us whether your measurements already include the walls or not.

Lowest Frequency You Want This To Play Down ToRequired

This is not your tuning frequency — this is the deepest note you actually want to hear. Range for this box style is 20 Hz to 30 Hz (Default 25 Hz; the lowest is 20 Hz). If Step 1's bass analyzer gave you a number, use it. If your target is below the floor for this style, you're in the wrong box style — go back and pick a deeper one, or contact us.

Box Type/LocationRequired

Pick the layout — 20 options covering trunk, walled trunk, no-wall SUV, B-pillar wall, C-pillar wall, under-seat truck, behind-seat truck, center console, and "Other." Each option specifies both where the sub faces and where the port faces (e.g. Trunk Box (Sub Back, Port Back)). If none of the presets match, pick "Other" and describe your layout in the Custom Requests field.

Custom RequestsOptional

I understand I'm buying only enclosure design blueprints (not a physical enclosure), with specifications optimized for my application, and I've read the product description's turnaround time.Required

You have to check this box to place the order. It confirms you know you're getting a blueprint (a set of cut sheets and specs), not a built wooden box shipped to your door.

I understand that if my request isn't physically possible (too much in too little space), my order may be refunded (minus transaction fees) if no workable adjustments can be made.Required

Also required. If the physics don't work — say you want 4x 15"s in a Prius trunk with 20 Hz tuning — we'll reach out, try to find a workable adjustment, and refund if we can't.

I agree that all required design constraints are included in this order form (whether previously discussed or not). Orders missing key constraints are not eligible for free revisions.Required

Also required. If you know something matters — a hump, a bracket, a specific port location — put it on the form. Anything left off is not free to fix later.

4th Order Bandpass

Best for: Systems that play about 22 Hz and up.
How it sounds: Loud in a narrow bass range. Not as deep as a 6th order, but takes less space.
Space needed: Less than a 6th order bandpass, more than a ported box.
Watch out for: The sub is typically flipped upside down (inverted) so it can cool itself. Make sure your sub can be mounted that way.

Subwoofer Fitness — Does Your Sub Belong In This Box?

Every subwoofer has two numbers on its spec sheet that tell you which box style it belongs in:

Qts — total Q of the sub. One number listed on the manufacturer's spec sheet under "Thiele-Small" or "T/S Parameters" (also on the spec card in the sub's box).
EBP — Efficiency Bandwidth Product. Calculated as Fs ÷ Qes (both come from the same T/S spec sheet). Some brands list EBP directly; if not, divide Fs by Qes on a calculator.

For this style specifically: 4th Order Bandpass likes Qts mid-to-high (roughly 0.4 and up) and EBP 50 or lower. Sealed-friendly subs (that Qts + EBP combo) belong here.

Rough Qts scale, if you're new to this: low ≈ under 0.4, mid ≈ 0.4–0.6, high ≈ 0.7 and up.

Not sure if your sub fits? Message us the brand and model before ordering and we'll tell you.

Step 4: Pick Your Layout

The layout is how the box sits in your vehicle and which direction the sub and port face.

Direction words (used when ordering):

Back = toward the rear of the vehicle
Forward = toward the front of the vehicle
Up = toward the roof
Side = toward the driver or passenger side

Common layouts: trunk box, SUV cargo-area box, wall behind the back seat (B-pillar or C-pillar wall), under-seat truck box, behind-seat truck box, center-console truck box.

If you already know the layout you want, tell us in the order. If not, just give us your measurements and your goals and we'll figure the layout out for you.

Step 5: Measure Your Space

Measure the biggest possible empty space where the box will sit. Not the space you want to use — the absolute maximum you have. Bigger measurements mean we can design a better box for you.

You'll need to account for:

Width, height, and depth of the space
How far your seats move back and recline
Anywhere the wheel wells, center console, amps, factory storage, or trim panels stick into the space

Follow the full measurement walkthrough here: How To Pull Your Own Measurements and pick the section that matches your build.

Step 6: Place Your Order

Before you check out, make sure you have all of this ready:

Your vehicle: year, make, and model
Your subwoofer brand, model, and how many you're running
Your measurements (from Step 5)
Your layout preference (from Step 4)
Any extra notes: things in the way, custom fitment concerns, sound-quality vs loudness goals, anything unusual about your car

Product-Page Walkthrough — Every Form Field Explained

Below is every field you'll see on the 4th Order Bandpass product page, in order, with what to enter and why.

Subwoofer Brand/Model/VersionRequired

Type the exact brand and model of your sub, plus the version if the model has multiple (like a v.2 or D2 vs D4). Example: Sundown Audio SA-12 v.2 D2. This is how we look up your sub's specs.

Subwoofer SizeRequired

Pick the physical size of your sub in inches (6.5", 8", 10", 12", 13", 15", 16", 18", 19", 21", 24", or 32", up to 32" depending on the product).

How Many Subwoofers?Required

How many of that sub you're running in this box (up to 24 depending on the product). Quantities over 4 have a small add-on ($10 for 5–8, $15 for 9+) — that's shown in the dropdown.

Vehicle Year/Make/ModelRequired

Type your vehicle exactly, like 2020 Toyota Camry SE or 2015 Chevy Silverado 1500 Crew Cab. Trim/cab-style matters — a Crew Cab and an Extended Cab have very different spaces.

Your Wood Sheet ThicknessRequired

Are Your Measurements Rectangular or Complex Shaped?Required

Max Height (Top to Bottom)Required

In inches. The tallest the box can be from bottom to top. Use decimals if needed (like 14.5").

Max Width (Left to Right)Required

In inches. The widest the box can be side to side.

Max Depth (Front to Back)Required

In inches. The deepest the box can go from front to back.

Complex Measurements Shape File UploadRequired

Upload a photo or drawing (up to 5 images) of the space if you picked Complex above. A phone snapshot with numbers written on it works fine — we don't need CAD. Only required if you picked Complex.

Measurement Type (Are you measuring inside a pre-existing shell, or an empty space?)Required

Lowest Frequency You Want This To Play Down ToRequired

This is not your tuning frequency — this is the deepest note you actually want to hear. Range for this box style is 22 Hz to 30 Hz (Default 25 Hz; the lowest is 22 Hz). If Step 1's bass analyzer gave you a number, use it. If your target is below the floor for this style, you're in the wrong box style — go back and pick a deeper one, or contact us.

Box Type/LocationRequired

Pick your layout — options cover trunk (port back or forward), no-wall SUV, B-pillar wall, C-pillar wall, under-seat truck, ext-cab behind-seat truck, center console, and "Other." Each option specifies the port direction (e.g. Trunk Box (Port Back)). If none match, pick "Other" and describe in Custom Requests.

Custom RequestsOptional

I understand I'm buying only enclosure design blueprints (not a physical enclosure), with specifications optimized for my application, and I've read the product description's turnaround time.Required

You have to check this box to place the order. It confirms you know you're getting a blueprint (a set of cut sheets and specs), not a built wooden box shipped to your door.

I understand that if my request isn't physically possible (too much in too little space), my order may be refunded (minus transaction fees) if no workable adjustments can be made.Required

Also required. If the physics don't work — say you want 4x 15"s in a Prius trunk with 20 Hz tuning — we'll reach out, try to find a workable adjustment, and refund if we can't.

I agree that all required design constraints are included in this order form (whether previously discussed or not). Orders missing key constraints are not eligible for free revisions.Required

Also required. If you know something matters — a hump, a bracket, a specific port location — put it on the form. Anything left off is not free to fix later.

6th Order Bandpass

Best for: Systems that play about 15 Hz and up — the deepest low-end you can get.
How it sounds: Very loud, very deep, but sensitive to how the car is set up.
Space needed: The most of any box style listed here.
Watch out for: Often needs a specific "cabin loading" setup to sound its best — usually rolling down one window and keeping the opposite one up.

Subwoofer Fitness — Does Your Sub Belong In This Box?

Every subwoofer has two numbers on its spec sheet that tell you which box style it belongs in:

Qts — total Q of the sub. One number listed on the manufacturer's spec sheet under "Thiele-Small" or "T/S Parameters" (also on the spec card in the sub's box).
EBP — Efficiency Bandwidth Product. Calculated as Fs ÷ Qes (both come from the same T/S spec sheet). Some brands list EBP directly; if not, divide Fs by Qes on a calculator.

For this style specifically: 6th Order Bandpass likes Qts low-to-mid (roughly 0.6 and under) and EBP 50 or higher. If your sub's Qts and EBP fit that combo, it belongs here.

Rough Qts scale, if you're new to this: low ≈ under 0.4, mid ≈ 0.4–0.6, high ≈ 0.7 and up.

Not sure if your sub fits? Message us the brand and model before ordering and we'll tell you.

Step 4: Pick Your Layout

The layout is how the box sits in your vehicle and which direction the sub and port face.

Direction words (used when ordering):

Back = toward the rear of the vehicle
Forward = toward the front of the vehicle
Up = toward the roof
Side = toward the driver or passenger side

Common layouts: trunk box, SUV cargo-area box, wall behind the back seat (B-pillar or C-pillar wall), under-seat truck box, behind-seat truck box, center-console truck box.

If you already know the layout you want, tell us in the order. If not, just give us your measurements and your goals and we'll figure the layout out for you.

Step 5: Measure Your Space

Measure the biggest possible empty space where the box will sit. Not the space you want to use — the absolute maximum you have. Bigger measurements mean we can design a better box for you.

You'll need to account for:

Width, height, and depth of the space
How far your seats move back and recline
Anywhere the wheel wells, center console, amps, factory storage, or trim panels stick into the space

Follow the full measurement walkthrough here: How To Pull Your Own Measurements and pick the section that matches your build.

Step 6: Place Your Order

Before you check out, make sure you have all of this ready:

Your vehicle: year, make, and model
Your subwoofer brand, model, and how many you're running
Your measurements (from Step 5)
Your layout preference (from Step 4)
Any extra notes: things in the way, custom fitment concerns, sound-quality vs loudness goals, anything unusual about your car

Product-Page Walkthrough — Every Form Field Explained

Below is every field you'll see on the 6th Order Bandpass product page, in order, with what to enter and why.

Subwoofer Brand/Model/VersionRequired

Type the exact brand and model of your sub, plus the version if the model has multiple (like a v.2 or D2 vs D4). Example: Sundown Audio SA-12 v.2 D2. This is how we look up your sub's specs.

Subwoofer SizeRequired

Pick the physical size of your sub in inches (6.5", 8", 10", 12", 13", 15", 16", 18", 19", 21", 24", or 32", up to 32" depending on the product).

How Many Subwoofers?Required

How many of that sub you're running in this box (up to 24 depending on the product). Quantities over 4 have a small add-on ($10 for 5–8, $15 for 9+) — that's shown in the dropdown.

Vehicle Year/Make/ModelRequired

Type your vehicle exactly, like 2020 Toyota Camry SE or 2015 Chevy Silverado 1500 Crew Cab. Trim/cab-style matters — a Crew Cab and an Extended Cab have very different spaces.

Your Wood Sheet ThicknessRequired

Are Your Measurements Rectangular or Complex Shaped?Required

Max Height (Top to Bottom)Required

In inches. The tallest the box can be from bottom to top. Use decimals if needed (like 14.5").

Max Width (Left to Right)Required

In inches. The widest the box can be side to side.

Max Depth (Front to Back)Required

In inches. The deepest the box can go from front to back.

Complex Measurements Shape File UploadRequired

Upload a photo or drawing (up to 5 images) of the space if you picked Complex above. A phone snapshot with numbers written on it works fine — we don't need CAD. Only required if you picked Complex.

Measurement Type (Are you measuring inside a pre-existing shell, or an empty space?)Required

Lowest Frequency You Want This To Play Down ToRequired

This is not your tuning frequency — this is the deepest note you actually want to hear. Range for this box style is 15 Hz to 30 Hz (Default 25 Hz; the lowest is 15 Hz). If Step 1's bass analyzer gave you a number, use it. If your target is below the floor for this style, you're in the wrong box style — go back and pick a deeper one, or contact us.

Box Type/LocationRequired

Pick your layout — options cover trunk (port back or forward, walled), no-wall SUV, B-pillar wall (three port positions), C-pillar wall, under-seat truck, ext-cab behind-seat truck, center console, and "Other." Each option specifies the port direction. If none match, pick "Other" and describe in Custom Requests.

Custom RequestsOptional

I understand I'm buying only enclosure design blueprints (not a physical enclosure), with specifications optimized for my application, and I've read the product description's turnaround time.Required

You have to check this box to place the order. It confirms you know you're getting a blueprint (a set of cut sheets and specs), not a built wooden box shipped to your door.

I understand that if my request isn't physically possible (too much in too little space), my order may be refunded (minus transaction fees) if no workable adjustments can be made.Required

Also required. If the physics don't work — say you want 4x 15"s in a Prius trunk with 20 Hz tuning — we'll reach out, try to find a workable adjustment, and refund if we can't.

I agree that all required design constraints are included in this order form (whether previously discussed or not). Orders missing key constraints are not eligible for free revisions.Required

Also required. If you know something matters — a hump, a bracket, a specific port location — put it on the form. Anything left off is not free to fix later.

4th Order Blow-Thru

Best for: Pickup trucks where the box sits in the bed and the port fires forward through a cutout in the back wall of the cab.
How it sounds: Same character as a 4th Order Bandpass — loud in a narrow bass range, works from about 22 Hz and up.
Space needed: Uses your bed floor. Cab space is untouched.
Watch out for: You have to cut the cab bulkhead. Measure the cutout carefully and make sure the port stick-out length matches the distance from your box to the cab wall. Sub is typically inverted for cooling — confirm yours can mount that way.

Subwoofer Fitness — Does Your Sub Belong In This Box?

Every subwoofer has two numbers on its spec sheet that tell you which box style it belongs in:

Qts — total Q of the sub. One number listed on the manufacturer's spec sheet under "Thiele-Small" or "T/S Parameters" (also on the spec card in the sub's box).
EBP — Efficiency Bandwidth Product. Calculated as Fs ÷ Qes (both come from the same T/S spec sheet). Some brands list EBP directly; if not, divide Fs by Qes on a calculator.

For this style specifically: Same as 4th Order Bandpass: Qts mid-to-high (roughly 0.4 and up) and EBP 50 or lower.

Rough Qts scale, if you're new to this: low ≈ under 0.4, mid ≈ 0.4–0.6, high ≈ 0.7 and up.

Not sure if your sub fits? Message us the brand and model before ordering and we'll tell you.

Step 4: Pick Your Port Layout

A blow-thru sits in the pickup bed and fires forward through the back wall of the cab. There is no "cabin layout" choice — the box is always in the bed. What you do pick is how far the port needs to stick past the front of the box so it lines up with the back of the cab, and how tall/wide the port opening can be relative to your bed floor.

Direction words (used when ordering):

Forward = toward the cab
Back = toward the tailgate

Step 5: Measure Your Space

Blow-thrus live in the pickup bed and fire forward through a hole in the back wall of the cab. Measure the biggest usable footprint you have in the bed and give us the exact port geometry so we can align it with the cab wall.

You'll need to account for:

Max width, height, and depth of the box footprint in the bed
How far the port needs to stick past the front of the box to sit flush with the back wall of the cab
Minimum height from the bed floor to the bottom of the port opening (the smallest gap you're willing to leave)
Maximum height from the bed floor to the top of the port opening (the tallest the opening can be without hitting the cab window or bed rails)
Max port width (left to right)

Full measurement walkthrough: How To Pull Your Own Measurements — go to the blow-thru section.

Step 6: Place Your Order

Before you check out, make sure you have all of this ready:

Your vehicle: year, make, and model
Your subwoofer brand, model, and how many you're running
Your measurements (from Step 5)
Your layout preference (from Step 4)
Any extra notes: things in the way, custom fitment concerns, sound-quality vs loudness goals, anything unusual about your car

Product-Page Walkthrough — Every Form Field Explained

Below is every field you'll see on the 4th Order Blow-Thru product page, in order, with what to enter and why.

Subwoofer Brand/Model/VersionRequired

Type the exact brand and model of your sub, plus the version if the model has multiple (like a v.2 or D2 vs D4). Example: Sundown Audio SA-12 v.2 D2. This is how we look up your sub's specs.

Subwoofer SizeRequired

Pick the physical size of your sub in inches (6.5", 8", 10", 12", 13", 15", 16", 18", 19", 21", 24", or 32", up to 32" depending on the product).

How Many Subwoofers?Required

How many of that sub you're running in this box (up to 24 depending on the product). Quantities over 4 have a small add-on ($10 for 5–8, $15 for 9+) — that's shown in the dropdown.

Vehicle Year/Make/ModelRequired

Type your vehicle exactly, like 2020 Toyota Camry SE or 2015 Chevy Silverado 1500 Crew Cab. Trim/cab-style matters — a Crew Cab and an Extended Cab have very different spaces.

Your Wood Sheet ThicknessRequired

Are Your Measurements Rectangular or Complex Shaped?Required

Max Height (Top to Bottom)Required

In inches. The tallest the box can be from bottom to top. Use decimals if needed (like 14.5").

Max Width (Left to Right)Required

In inches. The widest the box can be side to side.

Max Depth (Front to Back)Required

In inches. The deepest the box can go from front to back.

Complex Measurements Shape File UploadRequired

Upload a photo or drawing (up to 5 images) of the space if you picked Complex above. A phone snapshot with numbers written on it works fine — we don't need CAD. Only required if you picked Complex.

Lowest Frequency You Want This To Play Down ToRequired

How Far Should The Port Stick Out From The Front Of The Box To Be Flush With The Back Wall Of The Cabin?Required

In inches (1"–10"). Measure from the front of your box footprint (in the bed) to the outside of the cab's back wall. That's how far the port neck has to extend. Get this wrong and the port won't line up with the hole in the cab wall.

Minimum Height From Bed To Bottom Of PortRequired

In inches. The smallest gap you're OK with between the bed floor and the bottom of the port opening. If you want the port opening flush with the floor, put a small number (like 0.5" or 1"). If you need clearance for a toolbox or truck-bed tie-down, put more.

Max Height From Bed To Top Of PortRequired

In inches. The tallest the port opening can be from the bed floor without hitting the cab window, headliner, or bed rails.

Max Port Width (Left To Right)Required

In inches. The widest the port opening can be — usually limited by the width of the cutout in the back wall of the cab.

Custom RequestsOptional

I understand I'm buying only enclosure design blueprints (not a physical enclosure), with specifications optimized for my application, and I've read the product description's turnaround time.Required

You have to check this box to place the order. It confirms you know you're getting a blueprint (a set of cut sheets and specs), not a built wooden box shipped to your door.

I understand that if my request isn't physically possible (too much in too little space), my order may be refunded (minus transaction fees) if no workable adjustments can be made.Required

Also required. If the physics don't work — say you want 4x 15"s in a Prius trunk with 20 Hz tuning — we'll reach out, try to find a workable adjustment, and refund if we can't.

I agree that all required design constraints are included in this order form (whether previously discussed or not). Orders missing key constraints are not eligible for free revisions.Required

Also required. If you know something matters — a hump, a bracket, a specific port location — put it on the form. Anything left off is not free to fix later.

6th Order Blow-Thru

Best for: Pickup trucks that want the deepest, loudest blow-thru bass — 6th order pressure with the box in the bed firing into the cab.
How it sounds: Same character as a 6th Order Bandpass — very loud, very deep, sensitive to cab tuning.
Space needed: Uses your bed floor. Cab space is untouched, but this style needs the most footprint in the bed of any blow-thru.
Watch out for: Same cutout math as the 4th order blow-thru. Sub choice matters just as much as with a regular 6th order — stick to the Qts and EBP rule below.

Subwoofer Fitness — Does Your Sub Belong In This Box?

Every subwoofer has two numbers on its spec sheet that tell you which box style it belongs in:

Qts — total Q of the sub. One number listed on the manufacturer's spec sheet under "Thiele-Small" or "T/S Parameters" (also on the spec card in the sub's box).
EBP — Efficiency Bandwidth Product. Calculated as Fs ÷ Qes (both come from the same T/S spec sheet). Some brands list EBP directly; if not, divide Fs by Qes on a calculator.

For this style specifically: Same as 6th Order Bandpass: Qts low-to-mid (roughly 0.6 and under) and EBP 50 or higher.

Rough Qts scale, if you're new to this: low ≈ under 0.4, mid ≈ 0.4–0.6, high ≈ 0.7 and up.

Not sure if your sub fits? Message us the brand and model before ordering and we'll tell you.

Step 4: Pick Your Port Layout

Direction words (used when ordering):

Forward = toward the cab
Back = toward the tailgate

Step 5: Measure Your Space

You'll need to account for:

Max width, height, and depth of the box footprint in the bed
How far the port needs to stick past the front of the box to sit flush with the back wall of the cab
Minimum height from the bed floor to the bottom of the port opening (the smallest gap you're willing to leave)
Maximum height from the bed floor to the top of the port opening (the tallest the opening can be without hitting the cab window or bed rails)
Max port width (left to right)

Full measurement walkthrough: How To Pull Your Own Measurements — go to the blow-thru section.

Step 6: Place Your Order

Before you check out, make sure you have all of this ready:

Your vehicle: year, make, and model
Your subwoofer brand, model, and how many you're running
Your measurements (from Step 5)
Your layout preference (from Step 4)
Any extra notes: things in the way, custom fitment concerns, sound-quality vs loudness goals, anything unusual about your car

Product-Page Walkthrough — Every Form Field Explained

Below is every field you'll see on the 6th Order Blow-Thru product page, in order, with what to enter and why.

Subwoofer Brand/Model/VersionRequired

Type the exact brand and model of your sub, plus the version if the model has multiple (like a v.2 or D2 vs D4). Example: Sundown Audio SA-12 v.2 D2. This is how we look up your sub's specs.

Subwoofer SizeRequired

Pick the physical size of your sub in inches (6.5", 8", 10", 12", 13", 15", 16", 18", 19", 21", 24", or 32", up to 32" depending on the product).

How Many Subwoofers?Required

How many of that sub you're running in this box (up to 24 depending on the product). Quantities over 4 have a small add-on ($10 for 5–8, $15 for 9+) — that's shown in the dropdown.

Vehicle Year/Make/ModelRequired

Type your vehicle exactly, like 2020 Toyota Camry SE or 2015 Chevy Silverado 1500 Crew Cab. Trim/cab-style matters — a Crew Cab and an Extended Cab have very different spaces.

Your Wood Sheet ThicknessRequired

Are Your Measurements Rectangular or Complex Shaped?Required

Max Height (Top to Bottom)Required

In inches. The tallest the box can be from bottom to top. Use decimals if needed (like 14.5").

Max Width (Left to Right)Required

In inches. The widest the box can be side to side.

Max Depth (Front to Back)Required

In inches. The deepest the box can go from front to back.

Complex Measurements Shape File UploadRequired

Upload a photo or drawing (up to 5 images) of the space if you picked Complex above. A phone snapshot with numbers written on it works fine — we don't need CAD. Only required if you picked Complex.

Lowest Frequency You Want This To Play Down ToRequired

How Far Should The Port Stick Out From The Front Of The Box To Be Flush With The Back Wall Of The Cabin?Required

Minimum Height From Bed To Bottom Of PortRequired

Max Height From Bed To Top Of PortRequired

In inches. The tallest the port opening can be from the bed floor without hitting the cab window, headliner, or bed rails.

Max Port Width (Left To Right)Required

In inches. The widest the port opening can be — usually limited by the width of the cutout in the back wall of the cab.

Custom RequestsOptional

I understand I'm buying only enclosure design blueprints (not a physical enclosure), with specifications optimized for my application, and I've read the product description's turnaround time.Required

You have to check this box to place the order. It confirms you know you're getting a blueprint (a set of cut sheets and specs), not a built wooden box shipped to your door.

I understand that if my request isn't physically possible (too much in too little space), my order may be refunded (minus transaction fees) if no workable adjustments can be made.Required

Also required. If the physics don't work — say you want 4x 15"s in a Prius trunk with 20 Hz tuning — we'll reach out, try to find a workable adjustment, and refund if we can't.

I agree that all required design constraints are included in this order form (whether previously discussed or not). Orders missing key constraints are not eligible for free revisions.Required

Also required. If you know something matters — a hump, a bracket, a specific port location — put it on the form. Anything left off is not free to fix later.

Under-Seat Truck Box (Ported)

Best for: Pickup trucks where you want a real ported build under the back seat — no cargo-space penalty.
How it sounds: Ported character — louder than sealed with punchy deep bass. Limited by physical size (subs cap at 12", four max), so this isn't a wall-of-bass build. It's a strong daily-driver setup.
Space needed: Uses the empty space under a single truck seat. Cab and bed both stay clear.
Watch out for: Under-seat floors slope, so front height and back height are almost always different — measure both. Any hump, bracket, or seatbelt anchor sticking up will limit sub choice.

Ported only. This product is a ported enclosure exclusively — no sealed or bandpass under-seat option is available. All tuning and sub-fitness guidance below is for a ported alignment.

Subwoofer Fitness — Does Your Sub Belong In This Box?

Every subwoofer has two numbers on its spec sheet that tell you which box style it belongs in:

Qts — total Q of the sub. One number listed on the manufacturer's spec sheet under "Thiele-Small" or "T/S Parameters" (also on the spec card in the sub's box).
EBP — Efficiency Bandwidth Product. Calculated as Fs ÷ Qes (both come from the same T/S spec sheet). Some brands list EBP directly; if not, divide Fs by Qes on a calculator.

For this style specifically: Same as regular ported: Qts low-to-mid (roughly 0.6 and under) and EBP 50 or higher. Because you're capped at 12" subs here, sticking tightly to that Qts + EBP combo matters even more — the box is small and the sub has to be well-matched to work.

Rough Qts scale, if you're new to this: low ≈ under 0.4, mid ≈ 0.4–0.6, high ≈ 0.7 and up.

Not sure if your sub fits? Message us the brand and model before ordering and we'll tell you.

Step 4: Pick Your Sub & Port Direction

Under-seat builds have two direction choices instead of a full box-type dropdown:

Sub Location: Forward (toward the pedals), Downfire (cone at the floor), or Upfire (cone at the seat bottom).
Port Location: Forward, Both Sides, Driver Side, or Passenger Side.

If you're not sure which combo works best for your truck, tell us your goals and we'll pick.

Step 5: Measure Your Space

Under-seat truck boxes are unique because the floor almost always slopes — the front of the space is a different height than the back. We need both.

You'll need to account for:

Max front height (top to bottom at the front edge, closest to the firewall/pedals)
Max back height (top to bottom at the back edge, closest to the seat back)
Max width (left to right, side to side under the seat)
Max depth (front to back under the seat)
Any floor humps, seatbelt anchors, mounting brackets, wiring harnesses, or factory bins that stick up into the space — snap photos and upload them on the drawing field

Full measurement walkthrough: How To Pull Your Own Measurements — go to the under-seat truck section.

Step 6: Place Your Order

Before you check out, make sure you have all of this ready:

Your vehicle: year, make, and model
Your subwoofer brand, model, and how many you're running
Your measurements (from Step 5)
Your layout preference (from Step 4)
Any extra notes: things in the way, custom fitment concerns, sound-quality vs loudness goals, anything unusual about your car

Product-Page Walkthrough — Every Form Field Explained

Below is every field you'll see on the Under-Seat Truck Box (Ported) product page, in order, with what to enter and why.

Subwoofer Brand/Model/VersionRequired

Type the exact brand and model of your sub, plus the version if the model has multiple (like a v.2 or D2 vs D4). Example: Sundown Audio SA-12 v.2 D2. This is how we look up your sub's specs.

Subwoofer SizeRequired

Pick your sub size in inches. Under-seat truck builds are limited to 6.5", 8", 10", or 12" — anything bigger physically will not fit under a truck seat.

How Many Subwoofers?Required

Under-seat builds are capped at 1 to 4 subs. There's no add-on price at this quantity range.

Vehicle Year/Make/ModelRequired

Type your vehicle exactly, like 2020 Toyota Camry SE or 2015 Chevy Silverado 1500 Crew Cab. Trim/cab-style matters — a Crew Cab and an Extended Cab have very different spaces.

Your Wood Sheet ThicknessRequired

Sub LocationRequired

Pick which way the sub cone faces: Forward (toward the pedals/firewall), Downfire (cone pointing at the floor), or Upfire (cone pointing at the seat bottom).

Port LocationRequired

Pick where the port opens: Forward (toward the pedals), Both Sides (a port on driver and passenger side), Driver Side, or Passenger Side. Side-firing ports are common when the floor slopes and forward space is tight.

Max Front Height (Top To Bottom)Required

In inches. Measure from the floor to the bottom of the seat at the front edge of the space (closest to the pedals). Because truck under-seat floors almost always slope, front and back heights are different — we need both.

Max Back Height (Top To Bottom)Required

In inches. Same as above, but at the back edge of the space (closest to the seat back). The back is usually shorter than the front on most trucks.

Max Width (Left to Right)Required

In inches. The widest the box can be side to side. If you pick a side-firing port option (Both Sides, Driver Side, or Passenger Side), make sure this width leaves room for the port to breathe on the side(s) you chose — a port pinned against a firewall or door sill won't work.

Max Depth (Front to Back)Required

In inches. The deepest the box can go from front to back.

Complex Measurements Drawing Photo(s) UploadOptional

Optional. Snap phone photos of anything sticking up into the under-seat space — floor humps, seatbelt anchors, mounting brackets, wiring bundles, factory bins. Up to 5 images. Write measurements on the photo if you want.

Lowest Frequency You Want This To Play Down ToRequired

I understand I'm buying only enclosure design blueprints (not a physical enclosure), with specifications optimized for my application, and I've read the product description's turnaround time.Required

You have to check this box to place the order. It confirms you know you're getting a blueprint (a set of cut sheets and specs), not a built wooden box shipped to your door.

I understand that if my request isn't physically possible (too much in too little space), my order may be refunded (minus transaction fees) if no workable adjustments can be made.Required

Also required. If the physics don't work — say you want 4x 15"s in a Prius trunk with 20 Hz tuning — we'll reach out, try to find a workable adjustment, and refund if we can't.

I agree that all required design constraints are included in this order form (whether previously discussed or not). Orders missing key constraints are not eligible for free revisions.Required

Also required. If you know something matters — a hump, a bracket, a specific port location — put it on the form. Anything left off is not free to fix later.

T-Line (Transmission Line)

Best for: Musical, even bass response across a wider range of notes.
How it sounds: Very flat and even — no big peaks or dips.
Space needed: Similar footprint to a 6th Order Bandpass — T-Lines are the largest of the box styles.
Watch out for: If your sub is very deep front-to-back, it may need to be mounted upside down (inverted).

Subwoofer Fitness — Does Your Sub Belong In This Box?

Every subwoofer has two numbers on its spec sheet that tell you which box style it belongs in:

Qts — total Q of the sub. One number listed on the manufacturer's spec sheet under "Thiele-Small" or "T/S Parameters" (also on the spec card in the sub's box).
EBP — Efficiency Bandwidth Product. Calculated as Fs ÷ Qes (both come from the same T/S spec sheet). Some brands list EBP directly; if not, divide Fs by Qes on a calculator.

For this style specifically: T-Line requires a high Qts (0.7 and up) paired with a low Fs. Most subs designed for warm/musical sealed use fall in this range. If your Qts is below 0.7, T-Line is not the right style.

Rough Qts scale, if you're new to this: low ≈ under 0.4, mid ≈ 0.4–0.6, high ≈ 0.7 and up.

Not sure if your sub fits? Message us the brand and model before ordering and we'll tell you.

Step 4: Pick Your Layout

The layout is how the box sits in your vehicle and which direction the sub and port face.

Direction words (used when ordering):

Back = toward the rear of the vehicle
Forward = toward the front of the vehicle
Up = toward the roof
Side = toward the driver or passenger side

Common layouts: trunk box, SUV cargo-area box, wall behind the back seat (B-pillar or C-pillar wall), center-console truck box. T-Line footprints are usually too long for under-seat or behind-seat truck builds.

If you already know the layout you want, tell us in the order. If not, just give us your measurements and your goals and we'll figure the layout out for you.

Step 5: Measure Your Space

Measure the biggest possible empty space where the box will sit. Not the space you want to use — the absolute maximum you have. Bigger measurements mean we can design a better box for you.

You'll need to account for:

Width, height, and depth of the space
How far your seats move back and recline
Anywhere the wheel wells, center console, amps, factory storage, or trim panels stick into the space

Follow the full measurement walkthrough here: How To Pull Your Own Measurements and pick the section that matches your build.

Step 6: Place Your Order

Before you check out, make sure you have all of this ready:

Your vehicle: year, make, and model
Your subwoofer brand, model, and how many you're running
Your measurements (from Step 5)
Your layout preference (from Step 4)
Any extra notes: things in the way, custom fitment concerns, sound-quality vs loudness goals, anything unusual about your car

Product-Page Walkthrough

The T-Line product page is currently being rebuilt with the full form-based ordering system you see on the other styles. In the meantime, contact us directly to place a T-Line order and we'll walk you through the required specs by phone or email.

Ready to Get Your Custom Blueprint?

Place your order today and receive a precision-engineered subwoofer enclosure design built specifically for your vehicle and subs.

Browse Custom Designs How To Order

Country/region

How To Order A Custom Subwoofer Box Design

Step 1: Find Your Target Low Frequency

EZ DB's Bass Frequency Analyzer

Step 2: Know What You're Trading Off

Before Step 3: Understand These Two Sub Specs

Step 3: Pick Your Box Style

Sealed Box

Subwoofer Fitness — Does Your Sub Belong In This Box?

Step 4: Pick Your Layout

Step 5: Measure Your Space

Step 6: Place Your Order

Product-Page Walkthrough — Every Form Field Explained

Ported Box

Subwoofer Fitness — Does Your Sub Belong In This Box?

Step 4: Pick Your Layout

Step 5: Measure Your Space

Step 6: Place Your Order

Product-Page Walkthrough — Every Form Field Explained

4th Order Bandpass

Subwoofer Fitness — Does Your Sub Belong In This Box?

Step 4: Pick Your Layout

Step 5: Measure Your Space

Step 6: Place Your Order

Product-Page Walkthrough — Every Form Field Explained

6th Order Bandpass

Subwoofer Fitness — Does Your Sub Belong In This Box?

Step 4: Pick Your Layout

Step 5: Measure Your Space

Step 6: Place Your Order

Product-Page Walkthrough — Every Form Field Explained

4th Order Blow-Thru

Subwoofer Fitness — Does Your Sub Belong In This Box?

Step 4: Pick Your Port Layout

Step 5: Measure Your Space

Step 6: Place Your Order

Product-Page Walkthrough — Every Form Field Explained

6th Order Blow-Thru

Subwoofer Fitness — Does Your Sub Belong In This Box?

Step 4: Pick Your Port Layout

Step 5: Measure Your Space

Step 6: Place Your Order

Product-Page Walkthrough — Every Form Field Explained

Under-Seat Truck Box (Ported)

Subwoofer Fitness — Does Your Sub Belong In This Box?

Step 4: Pick Your Sub & Port Direction

Step 5: Measure Your Space

Step 6: Place Your Order

Product-Page Walkthrough — Every Form Field Explained

T-Line (Transmission Line)

Subwoofer Fitness — Does Your Sub Belong In This Box?

Step 4: Pick Your Layout

Step 5: Measure Your Space

Step 6: Place Your Order

Product-Page Walkthrough

Ready to Get Your Custom Blueprint?