How to Measure a Speaker Size for Replacement

Eric Chan

Are you upgrading your car's stereo system? First, it's important to have precise information about the installed speaker size and models. If you are going to replace the existing speaker set, you will also need to have the right replacements for your car. Therefore, before doing your car speaker replacements, let's learn how to measure a speaker size.

To make work easier, most car speakers come with dimension details. However, factory-fitted (stock) speakers hardly come with these details. Subsequently, we have put together a detailed and easy-to-follow guide on the different speaker dimensions and how to measure a speaker's size.

Important Dimensions For Car Speakers

Visually you might notice there is a variance between different car speakers. That notwithstanding, you will still be prone to getting the wrong fit for your car. To help you know the different size designations, here are the different speaker dimensions to look out for:

  • Mounting Depth: This dimension relates to the allowance required at the back of a speaker. This room ensures the speaker's magnet functions properly without static interferences caused by the car door panel. Inadequate mounting depth might cause problems with door locks and windows.
  • Mounting Height: This height determines the distance between a speaker's front and the door panel. Mounting height is important, especially for systems with tweeters higher than the mounting surroundings.
  • Cutout Diameter: This measurement relates to the width across a speaker's face. Subsequently, this dimension determines the positioning of a speaker within a mounting hole. We recommend having a smaller diameter than the mounting hole diameter for a comfortable fit. If the fit is too tight, it might cause problems during installation, such as damaging speakers or distorting a speaker's basket.
  • Mounting Screws Diameter: This diameter ensures a speaker is stably installed in a mounting hole. In theory, all speakers are said to have a similar mounting screw diameter, but this might differ in practice.

Process of Measuring a Speaker's Dimensions

Step 1: Remove the Housing

A speaker's housing is the compartment that holds a speaker in place like you have a subwoofer box for a loudspeaker. Unfortunately, some factory speaker models come fitted without access to the front grille. In such cases, you'll have to dismantle the entire door panel, risking interferences to other door parts. Focusing on the housing, here are steps to follow:

  • First, ensure the speaker or speakers are disconnected from power.
  • Be sure to spot the back panel slots.
  • Use two flat heads to apply pressure simultaneously on opposite sides.
  • If the housing is glued, you can chisel them apart carefully as you probe the surroundings. Noteworthy, care is paramount to preserve the original state of the speaker cabinet and components like a car amplifier.
  • Ensure you maintain the foam seal in the original form since it helps in preventing vibrations and providing a tight fit.
  • Additionally, ensure you know the dismantled wires and screws for precise refit after replacement.

Step 2: Measure the Speaker’s Diameter

Next, measure your target speaker's diameter by measuring the entire length of the speaker frame. Ideally, we recommend measuring across the speaker's center for accurate dimensions. There are different ways to identify a speaker's center, including checking where lines intersect. Other methods are as follows:

  • Using holes that are opposite to each other
  • For oval-shaped speakers, ensure you obtain the narrow and wide lengths
  • Similarly, ensure you obtain the length across all dimensions for uneven shapes to ensure you have the accurate speaker size.
  • For evenly-shaped speakers, sampling a few oppositely placed screws is adequate for accuracy.
  • Moreover, record the measurements and their subsequent units for accuracy.

Image Credit: wikihow.com

Step 3: Measure the Cutout Diameter

Notably, the cutout diameter should match the housing hole's diameter. That said, this step will help you avoid speaker protrusion and interference with other car components. Therefore, here is the procedure to obtain the cutout diameter of the damaged and replacement speaker:

  • First, flip your speaker upside-down position such that the magnet faces up.
  • Measure the shutout diameter at the widest point of the attached cone. A ruler will help, but a large vernier will be more accurate.
  • Remember, if the speaker has an uneven shape, measure all dimensions as you use the widest point in every direction.
  • Ideally, the mounting hole should be slightly larger than the cutout diameter.

Step 4: Measuring the Mounting Height and Depth

You'll be measuring the distance between the base and top for the mounting height. Considering that different speakers vary in design and shape, the standard approach is to use the highest point for this step. Accordingly, here are steps to follow:

  • Ensure the widest part of the speaker faces up
  • Proceed to measure the distance between the bottom and top points. As earlier highlighted, adequate mounting depth helps prevent static noise.
  • At best, the speaker height should be slightly shorter than the frame height.
  • Also, the speaker should leave some space in its height to avoid interference with the grills and panels. Adequate height also ensures quality sound output and provides protection of the speaker from the housing and other surrounding bumps.

On the same note, remember to measure the mounting depth. Here is the procedure for this process:

  • Flip your speaker again on a flat surface as the cone faces up.
  • As the speaker stands on its magnet, measure the distance between the flat top surface and the bottom of the speaker.
  • For replacement speakers, ensure they aren't higher than the original ones.

Step 5: Measure the Speaker Screw Pattern

When measuring the mounting holes, you'll focus on the diameter and depth. Once again, measure across the widest section (s) for even and uneven shapes. We recommend having a mounting hole as wide as the speaker's mounting frame for a steady fit. In line with the mounting dimensions, also note the pattern of the screws.

As you measure the car speaker's screw patterns, you can use a ruler or tape measure to obtain accurate distances and patterns. Fortunately, the screw pattern isn't a big issue across the different designs and shapes. Nonetheless, for uneven shapes, you can confirm the pattern for the right new speaker.

Frequently Asked Questions on Measuring the Speaker Size

1. Does speaker size make a difference?

Bigger speakers have better audio quality than smaller ones. Also, big speakers produce more bass and volume. Nonetheless, getting a big speaker for better audio quality won't make sense if it doesn't fit in your car.

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