There are two main reasons why you’ve ended up here. Either your car speakers are damaged, and you need to replace them, or you’re looking to get more juice out of your car stereo and want to upgrade your speakers. Either way, it’s essential to know how to measure car speakers size so that you don’t end up in a jam down the line.
Good thing measuring car speakers isn’t too tricky. And, with some simple tools, you can get it done quickly. Then you’ll be able to compare your mounting holes to available speakers to see which will fit. That’s it.
Parts of a Car Speaker
Car speakers generally have the same parts. So, it’s going to be a good idea to know what those are if we’re going to speak the same language about measuring them up. But don’t worry about the complicated mechanisms inside.
The five main parts of a car speaker you need to know are the grille, speaker cone, gasket, basket, and magnet. Let’s look at each in more detail.
This is the part you see on the outside of the speaker. It’s normally made of plastic or metal and is perforated by thousands of tiny holes to let the sound out. At the same time, the grille protects the speaker cone from being damaged by rips and tears.
This is the part most of us are talking about when we talk about speakers. It vibrates and produces the sound in most speakers. It can be made of a stiffer material like plastic, ceramic, or fiber-reinforced cloth. But, most often, they’re made of paper.
Now, it’s very likely that you’ll find coaxial speakers in your car. This means that they’ll also have a second little tweeter cone in the middle of the bigger woofer cone.
The speaker cone is held onto the basket from the front by the gasket. This is the top part of the frame holding the speaker together and can be either metal or plastic.
So-called because it looks like a basket. It is the bottom part of the frame supporting the speaker. Baskets are almost always made out of metals like steel or aluminum because they need to be strong to give the speaker a framework and protect the insides from the outside world.
The butt-end of the speaker. This magnet may or may not be inside a cover, but for our measuring purposes, it doesn’t matter.
Great, now that we’re speaking the same language, we can talk about the best way to measure car speakers.
Factory Speaker Sizes
Generally, factory speakers are standardized to set sizes. Yes, the whole automobile industry is in on it! That is, at least, they do talk and try to standardize some components to help contracting companies produce them. This is great because the standard sizes are interchangeable, right?
If only that were true…
Speakers are generally sized by their diameters if they’re round and their length by width if they’re oval. But that doesn’t mean that they’re always the size they say. They can be a touch smaller or bigger than their category.
In other words, a 4” speaker might actually measure 3.69” or 4.05”, or anywhere in between.
General Types and Size Categories of Factory Car Speakers
Since we are learning how to measure car speakers size, it’s good to know what to expect. To help with that, here are common factory car speaker sizes and types.
- 3.5” speakers – normally coaxial; 3.25” mounting hole; two screw mount tabs; found in dashboards.
- 4” speakers – coaxial or component; 3.69” mounting hole; three to four screw mount tabs; found in dashboards and doors.
- 5.25” speakers – coaxial or component; 4.69” mounting hole; three to four screw mount tabs; found in the rear deck or rear doors.
- 6” speakers – coaxial or component; 4.88” mounting hole; four screw mount tabs; found in the rear deck or rear panels.
- 4×6” speakers – coaxial or plate; 3.75” x 6” mounting hole; four screw mount tabs; found in doors.
- 5×7” speakers – normally coaxial; 4.56” x 6.69” mounting hole; four screw mount tabs; found in doors and rear panels (rare).
- 6×9” speakers – normally coaxial; 6” x 8.82” mounting hole; four screw mount tabs; found in the rear deck or rear panels.
Removing Your Old Speakers
To replace the factory speakers in your car, whether they’re damaged, or you just want to upgrade, the process is the same. Here’s what to do:
- Remove the grilles, which normally have a small slot in the bottoms. You can insert a pen knife or a small screwdriver in the slot to pry the grille off. If it doesn’t pop right off, check for tiny screws. Alternatively, the grille might be glued on. If it is, use a blade to carefully score all the way around the grille.
- Unscrew the mounting screws. KEEP THEM! The best screws to attach new speakers are the same old ones you just unscrewed.
- Pull the speaker out of its mounting hole and, being sure that the car’s electrical system is turned off, disconnect the wiring.
Now that the speaker is disconnected, you’ve got it in your hands and an empty mounting hole – measure both.
How to Measure Car Speakers Size
The first measurement that you should take is the diameter of the speaker. All these measurements are done the same way. The best way to do this is to use a clear plastic ruler if you have one. A tape measure can also work, but I like being able to see through the ruler.
Place the speaker cone-side up on a table, then line up the zero on your ruler to one edge of the speaker gasket. Next, try to find the diameter by aiming the ruler through the middle of the speaker and across to the far edge.
You can rotate the ruler back and forth (keeping the one edge on zero), and the largest number it hits will be the diameter. This should tell you the size category you’re in, even if it’s not exactly that size to the inch.
If you’re measuring an oval speaker…
You’ll have to do this twice. You’ll need to find the longest and widest points of your speaker. Right, now, you know your speaker’s diameter or length and width. Are you done?
Not quite. The diameter isn’t the only thing you need to measure. It’s the most important car speaker size measurement, but there are other numbers to know for when you buy replacements.
Mounting Hole and Cutout Diameter
Let’s be clear right off the bat that these two measurements are NOT the same thing. One is the size of the hole in your car’s panel. The other is the minimum size of a hole a speaker needs to be installed properly.
If the numbers do match up, it will be next to impossible to install that speaker in that hole since you won’t have any wiggle room. This can lead to you scratching or damaging the speaker basket upon installation.
To measure the mounting hole for the car speaker…
Use the same technique as you used to measure the speaker diameter or length and width. These numbers DEFINITELY WON’T be the same.
The gasket is mounted on the outside of the hole. Therefore, its diameter has to be bigger than the hole diameter. So, measure up to find the mounting hole diameter or, in the case of an oval speaker, length and width.
Some mounting holes are even rectangular in shape, and these are even easier to measure. They normally let you install oval speakers using rectangular mounting plates to cover the holes. This gives you a lot of versatility in the sizes you can put in.
How do you measure cutout diameter?
Luckily, you don’t have to. Instead, this is the number you need to look out for when buying new speakers. You want to find a cutout diameter that’s a little bit smaller than the size of your mounting hole.
This can be smaller up to about ¼”, but any less than that, and you’ll risk the speaker being too small. If the cutout diameter on a speaker you want is bigger than your mounting hole, the only way you can install it is to cut that hole bigger.
Unless you’re a body shop pro, I don’t recommend that one bit.
This is another measurement that you’ll want to look for when you shop for speakers. It’s almost always given by the manufacturer, so you know where this speaker can go. The mounting depth is the safe installation depth needed to install a speaker.
Now, you have a speaker you just removed sitting on your table. Measure the depth of it from the magnet up to the bottom edge of the gasket. This will tell you how deep the speaker is that you took out.
But you also have a mounting hole that you can measure as well…
Stick your ruler or tape measure into the hole until you hit the inside wall. That’s the maximum possible depth you have to work with.
Remember that the magnet may stick out quite a lot, and there needs to be room for wires as well. So, the depth you just measured has to be bigger than the mounting depth on your new speaker.
Speaker Mounting Height
If you’re going to use the grilles that come with your new speakers, the speaker mounting height is not going to be an issue. These grilles are designed to fit!
But, if you’re going to replace speakers behind your car’s factory grilles and want to keep using those same grilles, you need to be sure the mounting height gives you clearance.
The mounting height of a speaker is how far the speaker sticks up from the mounting hole. You can find this measurement stated on new speakers.
How much mounting height will your grilles accommodate?
You need to know the height to the inside edge of the grille. What I do is lay the grille on a flat surface like a table and then put a hard book on top. Then I measure up from the table to the book. After that, I will subtract the thickness of the grille, and that will get me the mounting height.
Mounting Screws and Screw Distance
Mounting screws can present a real trick for installation. This is because even though speakers might be the same size, they could have their mounting screw holes in different places. Or have a completely different number of holes.
Check out these two 4 ½” speakers as an example…
If you pick up the 4FR-8 speakers from GRS, you’ll find that they have four holes for the mounting screws. However, these same-sized speakers, the 802s from Bose, have only three screw holes. So, if you tried to mount these in a mounting hole that had four holes, you might be up the creek.
Not only can the number of holes be different, but they can also be differently spaced. To figure out the spacing, measure the distance between mounting crew holes on the panel you’re installing the speaker into.
Then you can check this distance with the new speaker. If it’s not the same, or at least not close, you may have to drill a new hole or two. Once again, that’s not something I’d recommend – better to install something that matches up properly.
There is another handy solution, though…
Some brands make “universal mounting” speakers that use clips instead of screw holes to hold the speakers in place.
If your holes weren’t going to line up with either of those 4½” speakers, you could try these PL412BK 2-way speakers from Pyle. They clip on to most any hole and don’t need to line up at all.
Want To Improve Your Car’s Audio?
We can help with that. Check out our in-depth reviews of the Best 6.5 Speakers, the Best 6×8 Speakers, the Best Car Amplifiers, the Best Car Subwoofers, and the Best Subwoofers for Single Cab Truck you can buy in 2023.
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How to Measure Car Speakers Size – Final Thoughts
When you have speakers that have given up the ghost, they need replacing. When you want to increase the boom boom in your vroom vroom, you can swap your factory speakers for some after-market speakers with more power.
In either case, it’s important to measure first before you buy your new speakers. The speaker diameter is, of course, going to limit your choice. But that’s not all you have to worry about.
It’s a good idea to check the depth, mounting hole size, mounting height, and even the mounting screw setup. If everything lines up with the new speakers, you’re good to go. If it doesn’t, you just might have to look elsewhere.
Until next time, good luck and happy listening.