The Best (and Worst) Subwoofer Enclosure on Amazon.

 

This website* is primarily dedicated to teaching you how to build your own subwoofer.  If you want to get into box building check out this blog post, and this podcast where some top DIYers talk about how to get started:

  

But, not everybody can do that.  You need tools, time, and skill.  There is no shame in ordering a pre-fabricated (a.k.a pre-fab) subwoofer enclosure from Amazon and installing your own speakers.  Here is some examples of good and bad enclosures along with a breakdown of what makes a good enclosure.  We will cover unloaded (no subwoofer included) enclosures in this post and save pre-loaded (subwoofer included) enclosures for another day.

Unloaded:  BYOS (Buy Your Own Subwoofer)

Before we get into reviewing boxes keep in mind that if you go with an unloaded enclosure you will need to order a subwoofer to go with it.  Your goal is to match the subwoofer to the enclosure.  Typically this is just a matter of looking up the manufacturer specifications and looking for a prefab box that will work.  But, before you do that you need to know what makes a "good" box good and what maxes a "bad" box bad.

A Bad Box (click on the image to view on Amazon)

So, what's so bad about this box?  Everything, this box is why pre-fab boxes have such a terrible reputation in car audio.

It is made out of 5/8" MDF.  That's bad.  MDF is a great material, but it needs to be thick.  The walls on this enclosure is just a tad thicker than 1/2".  The standard size is 3/4"  PLUS a double baffle (1.5").  The walls on this box are going to flex.  In medium to high power applications your subwoofers will tear this box apart.  If you plan on running cheap subwoofers and a small amp it might work.  This box could be fixed with some simple braces and reinforcement.  But that will take up air space in the box, which brings us to the second problem with this enclosure.

The net internal airspace is unknown.   The net external dimensions are listed, and the entire enclosure is just a hair over 4 cubic feet.  Some quick tells me that this enclosure has no more than 1.7 cubic feet per side BEFORE you back out the port displacement.  The actual number is probably closer to 1.4.  This is a problem because that is not enough space for a 12" subwoofer in a ported enclsoure.  Speaking of the port, what about the port?

Based on the external dimensions, the material thickness, and the internal pictures showing the port it looks to be about 10" long.  It cannot psychically be any longer than 12.  My best estimate of the port tuning frequency is going to be between 40 and 45 HZ.  This is tuned absurdly to high.  Check out this video for more information on port tuning:

How is that going to sound?  It is going to loud, but it is not going to be low.  In fact, you will probably rip your subwoofers apart if you try to play low frequencies without an infrasonic filter, here is a video explaining how this works:

It is important to remember that there is a market for gear at all price points.  So some of you will still want to buy this box.  There is no shame in owning entry-level gear, and there is nothing wrong with trying to stay in a reasonable budget.  If you are trying to bass on a budget go ahead and grab this box.  Just match it with an appropriate subwoofer, like the GRS 12:

I am a huge fan of this driver and I recommend it for anybody that is on a budget.  Check out this video of this sub in action:

A Better Box (click on the image to view on Amazon)

This box is the BBox from Atrend, they have been in the game quite a while and they make decent pre-fabs, a lot of brick and mortar stores stock these enclosures.  I use one of their under seat boxes in my truck.  Currently, this enclosure is only about $30 more than the previous box and it is $30 well spent.  What makes this box better?

Thicker MDF.  Some Atrend boxes still use 5/8" MDF, but this one steps up to 3/4" plus a 1" baffle.  Thicker material flexes less, and will sound better.

Better airspace (but not quite enough), the specs on Amazon are a little confusing.  One of the images claims 1.32 cubic feet per side.  But the specs indicate 1.8 cubic feet per side.  You need a big box to make big bass, so any increase in box size is an improvement.  For a pair of 12 inch subwoofers I would rather see 2 or 2.5 cubic feet per side.  But that makes for a HUGE box, and it is going to scare away some customers.

Better construction.  Mitered joints, and dado grooves, probably all CNC cut.  This makes for stronger joints, which makes a stronger box and a better sound.  

Lower tuning, means better bass.  This enclosure is tuned to 36 Hz which is typical for car audio designs.  Judging from the images we can see that the port wraps around the interior of the enclosure, giving adequate length to reach that tuning frequency.

The Best Box (click on the image to view on Amazon)

This box is manufactured by SKAR Audio.  I mention  them in my post on 10 subwoofer brands that you have never heard off.  This company has developed a reputation for delivering quality bass at reasonable prices.  Even though this is one of the more expensive enclosures on Amazon it is still a great bargain.  

Finally a box with a reasonable amount of air space!  This enclosure claims to have 2 cubic feet per side.  

Finally a box with a reasonable port tuning!  A nice low 32 HZ.  This is spot on for most cars.  

Although not specifically stated in the specs on Amazon it appears to use 3/4" MDF along with internal bracing.  Plus it has some extra touches that make it worth the extra money:

1. Quality speaker terminals
2. Pre-wired internally
3. Acoustic stuffing attached to the inside of the enclosure.
4. A kerf-cut flared port that will help reduce port noise.  
   

 Conclusion

There are a lot of other enclosures on Amazon, with varying degrees of quality at many different price points.  One key thing to remember is that you don't always get what you pay for, read the details and don't pay $90 for a junk box when a decent box can be purchased for the same price.  Hopefully this article has helped you not only pick out a quality enclosure, but it has also shown you what makes for a quality enclosure.

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How to Design a Dual Subwoofer Enclosure

There seems to be a lot of confusion about how to design and build a subwoofer enclosure with multiple subwoofers in the same airspace.  This blog post is going to clear it up.

A Single Subwoofer in one enclosure

Let's start off with something simple, a single subwoofer in a 2 cubic foot enclosure tuned to 28 hertz.  In this example the port has been drawn outside of the enclosure for easier comparison.  The port is 1"X12" and is 17 3/4" in length.  Before you go out an build this enclosure keep in mind that a 1"X12" port is probably not large enough to prevent port noise.  This size was chosen just as an illustration.  

 

 

 

 

If you wish to add a second subwoofer then you will need to increase the size of the enclosure.  If you increase the size of the enclosure you will need to make a shorter port.  This is because you tune the port to the airspace in the box, not the number of subwoofers in the enclosure.  So here is a 4 cubic foot enclosure with a cut out for a single driver.  We can see that the port is a lot shorter.

Two Subwoofers in a Single Enclosure

 Now Let's add a second woofer cut out and we see that the port is exactly the same.

However, now we have created a new problem.  Now we have two subwoofers, so we are moving twice the air.  That means the port needs to do twice the work.  So the port cross section needs to be larger or else the air speed velocity in the port will create turbulence in the port.  This will lead to audible port noise, also known as "chuffing."  We need to make the port opening larger.  As described in this blog post, when the port opening becomes larger the port needs to be longer.  So let's double the port area. This image shows the same enclosure with a 2"X12" slot port, and now the port is longer.

This final design is perfectly acceptable, it may be a good idea to make the port area a bit larger or  flare the port to minimize chuffing, beyond that all that is needed is to fold the port into the enclosure and adjust the enclosure size in order to account for the volume that the port takes up.

 

Dual Ports

 

Some people might prefer the look of an enclosure with two ports instead of one.  How do we design that?  Nothing like you might expect.  When you add a second port each port will tune half of the enclosure.  In this example, where we have doubled the enclosure volume, and double the number of subwoofers, an enclosure with two ports will look exactly like two enclosures with just one subwoofer.  You could divide this enclose into two equal sized chambers and get the same frequency response (but 6 db louder since you will have double the cone area and double the power).

In fact that is how most pre-fab subwoofer enclosures are designed.  After browsing Amazon for some examples I found it difficult to locate an enclosure that had one chamber with two drivers, and even more difficult to find one that had one chamber with two ports.   The typical dual subwoofer enclosure available on Amazon has two chambers with a single port down the middle such as this one (click on the pic for details):

Dual Chamber enclosure with a single port.

For this type of enclosure the port is typically half-sized on each chamber and then merges into a single, larger chamber.  I imagine this is done so that the ports serve as a brace. 

If you are looking for a good subwoofer then you should check out my list of 10 little-known but totally awesome subwoofers.  To learn more about port tuning here is a great video over on the DIY Audio Guy YouTube Channel:

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Subwoofer Ports

Subwoofer ports (a.k.a vents) are interesting things.  In a previous post I provided some background into how ports worked, in this post I am going to dig a little deeper into port design, a.k.a. port tuning.

Flared Ports with Wooden Connector Rings

The Port Formula

There is a formula that you can use to design a port, since formulas tend to scare people away and there plenty of tools available to do the calculations for you this blog post will focus on understanding the four main parameters that you need to think about when designing a port. 

• Tuning Frequency
• Enclosure Volume
• Port Cross Section
• Port Length

We can manipulate any three of these four items and the formula dictates the forth parameter.  For this post we are going to examine how the tuning frequency, enclosure volume, and port cross section influence the length of the port.  It is very important to understand the impact of these four parameters as they will determine the size, shape and sound of our subwoofer.  We need to get the sound we want, while keeping a reasonably sized box, a reasonably sized port, and a reasonably simple port.  We also need to design the system so we don't have any port noise (a.k.a. "chuffing").

  

Tuning Frequency

This is the resonate frequency, expressed in hertz (HZ) of the subwoofer enclosure.  Sometimes we call this Fb, or the box frequency.  We could have an entire blog post dedicated to understanding this concept.  But for now all you need to know is that if you want your subwoofer to play lower then you need to to tune the box lower.  For a given enclosure volume and port cross section you can adjust the tuning frequency by adjusting the length of the port.  As the port gets longer the tuning frequency gets lower, As the port gets shorter the tuning frequency gets higher.  This can be clearly seen in in this plot, which is based on a 4" diameter port in a 2 cubic ft box.

Port Length VS. Tuning Frequency, 2 CU FT Enclosure, 4" Diameter Port

For those that have a hard time visualizing a plot consider these images, each shows an identical sized enclosure (2 Cu FT), each with a 1 x 12 slot port.  The first image shows a 25 3/16" long port, which corresponds to a 24 HZ tuning frequency.  The second image shows a 17 3/4" long port, this enclosure is tuned to 28 HZ.  The third image shows a 12 59/64" long port, and a 32 HZ tuning frequency.  The key take away here is that a lower tuning frequency requires a longer port, holding everything else constant.  The ports are shown outside of the enclosure so that the relative size of the ports are easier to visualize. 

24 HZ Fb, 2 CU FT, 1X12 Slot Port

28 HZ Fb, 2 CU FT, 1X12 Slot Port

 

32 HZ Fb, 2 CU FT, 1X12 Slot Port

 

The ports in the above three images are relatively small and can be quite easily folded into their respective enclosures (obviously the enclosures will need a slight redesign in order to maintain the same airspace).  But, port design is not quite that simple.  There are several other factors that must be considered.  

Enclosure Volume

Now consider a slightly different scenario, let's hold the tuning frequency constant, along with the port cross section and look at what happens when we adjust the box volume.  As the enclosure volume gets larger the port gets smaller, and vice versa.  This plot shows the relationship for a 4" diameter port tuned to 40 Hz.

Port Length Vs. Box Volume, 4" Diameter, 40 HZ Fb

 

 

Again, for those that find it difficult to visualize this consider these two images which both show two absurd enclosures.  Neither of these is very good design, they were just selected for.  The first is a 1 CU FT enclosure tuned 28 HZ with a 1X12 slot port, and the second is a 4 CU ft enclosure tuned to 28 HZ with a 1X12 slot port.

1 CU FT, 28 HZ Fb, 1X12 Slot Port

4 CU FT, 28 HZ Fb, 1X12 Slot Port

The 1 CU FT enclosure has two main problems.  First the port is comically long.  It would be very difficult to build that port (it is over 3' long) into the enclosure.  This is the result of using an undersized box.  As the box gets smaller, holding everything else constant, the port must get longer.  Second, the small size of the box will have adverse effects on low frequency response.  The 4 CU FT box, on the other hand is not a reasonable solution.  For starters it is a comically oversized enclosure.  With a box this large the port length becomes trivial.   

Port Cross Section

The port cross section, which rather the cross sectional area is another important factor.  The port needs to be large enough to prevent port noise, also called chuffing.  This happens when the air in the port moves fast enough to create turbulence.  As a general rule of thumb the air speed velocity needs to be less than 5% of the speed of sound.  There are two solutions to this problem, the first is to flare one or both ends of the port.  The second is a larger port opening.  But, that presents a problem.  As the cross sectional area of the port increases, holding everything else constant, the port length increases.  Here is yet another chart showing the relationship.  This example uses a 2 CU FT enclosure tuned to 30 HZ.

Port Length vs Port Cross Sectional Area, 2 CU FT, 30 HZ Fb

Here is a example of a comically long port.  This was designed to show the absurd result you wold get if you were to take things to the extreme in order to get rid of port noise.  This design uses a 2 CU FT enclosure, tuned to 28 HZ with a 3X12 slot port.  The end result is a port that is almost 5'.

3X12 Slot Port, 2 CU FT, 28 HZ Fb

So there you go, now you know how box tuning, port area, and enclosure size impacts the length of you port. Hopefully you found this post interesting and informative.  I am planning a few more posts that dig deeper into the port tuning formula, so make sure you check back in frequently.  If you want to learn more you can also check out this video on the DIY Audio Guy YouTube channel:

 

 

10 great subwoofer brands that you have never heard of!

There are a lot of great subwoofers brands on the market right now.  Most people are familiar with mainstream brands like Alpine, Sony, Polk, Kenwood, Klipsch, Yamaha, Kicker and JL Audio*.  But there are a ton of others that you may not know about, but you SHOULD!  Since this is a DIY page we are going to focus on raw drivers that will work well in both the home and the car.  These are the subwoofers that the insiders and the experts know and love.  So if you know these subs then you are either an insider or an expert. 

#1 Dayton Audio 

Dayton Audio 10" Ultimax

Let's kick off the list with a brand that we have LOT of personal experience with.  Dayton Audio is the house brand for Parts Express, Parts Express specializes in DIY audio and they supply parts to OEM speaker manufactures.  We have personally built several projects using these drivers. 

 

They offer the “classic” line of value priced entry-level subwoofers, these are great subwoofers for an entry level home theater build.  

Dayton Audio Classic 12"

 

The Dayton Audio Reference Series are aluminum cone drivers available in both High Fidelity and High Output versions.  The Ultimax is an awesome home theater or car audio subwoofer.

 

 

 

#2 NVX

Speaking of house brands our next subwoofer is NVX, this is the house brand for Sonic Electronix, an online car audio retailer.  They offer a wide variety of subwoofers, and it is not uncommon to see these drivers at car audio competitions.  The VCW line is an absolute beast.  Check out this massive 1,000 watt 15” sub with a three-inch voice coil that you can pick up on Amazon:

NVX VCW152 1000W 15" VC-Series Dual 2-ohm Car Subwoofer

    #3 Savard

Speaking of Amazon, Savard is another great brand that you can get on amazon.  Back in the 1990's this small company out of Baton Rouge had a cult following, and made fantastic speaker system for the car and the home.  Bill Savard's son, Will, as resurrected the brand.  It is back and better than ever.  The 6.5”HI-Q subwoofers is an absolute beast!  This is a 300 watt 6.5 with a 2" inch voice coil. 

SAVARD Speakers HiQ Series 6.5" inch Dual 2 Ohm Subwoofer

They also have the less expensive RAP series, but don't be fooled by the entry level price.  Just give this this 1,000 watt RAP 12 with 16 mm of XMAX a look.  AT $150 shipped you going to have a hard time finding a better bass for your buck.

Rap Series 12" D2v2 Subwoofer

#4 GRS

Next up is GRS, the budget champion.  GRS stands for great replacement speakers.  If you want to breath some life into old speakers these are affordable drop-in replacements.  The subwoofers work well in a wide variety of ported and sealed enclosures. When I say affordable, I am not kidding.  The 12” model is less than $25.  If you are looking for a budget subwoofer this is the hands down winner. You would pay twice that for a similar subwoofer from a mainstream car audio company.  The DIY Audio guy used one of these in the budget bass box:

#5 Image Dynamics

IDMAX12 V.4 D4

Not every subwoofer on this list is a budget subwoofer.  Image Dynamics has a great reputation and they have been around for a long time, so you have probably heard of them.  The IDMAX line of subwoofers are handmade in the US!  They are are known for their amazing sound quality, and look fantastic with an understated, elegant logo across the front!

It is common to find these in infinite baffle trunk builds.  If you want something that can get nasty low, make some serious bass, and sound good doing it you can't go wrong with Image Dynamics.  On top of all that Image Dynamics can be re-coned in a matter of minutes with their re-cone kits!

#6 Wavecor

Here is another amazing sound quality subwoofer, Wavecor.  They have a wide variety of shapes and sizes, like this funky looking shallow mount.  Check out this big 12 with the aluminum cone:

Wavecor SW312WA03 12-1/4" Aluminum Cone Subwoofer

You may look at this and think that the power handling just ain’t what it should be on a sub at this price point. But check out the sensitivity.  This thing does not need a lot of power to get loud. You can pick these up at parts express.

#7 Rockville 

Now it is time to stir up controversy with a sub from audiosavings.com, the Rockville K9!

Rockville W12K9D2 12" 4000w Car Audio Subwoofer

What do I mean by controversy?  Rockville very famously LIES about their power ratings.  This driver can only handle 500 watts RMS.  There was even a class action lawsuit filed against audiosavings.com. So, why are we recommending this sub?  Because it is a great subwoofer offered at a bargain price.  We are not the only ones that think so.  The YouTuber HiFi Vega thinks it is the best 12" for under $150.  Here is his video:

   

#8 Tang Band

 

Tang Band W8

Tang Band is very popular among the DIY audio crowd.  "The Uglies" by Toid's DIY Audio makes use of a pair of the W8's in each tower.

The DIY Audio Guy used a 6.5" version the W6 in this compact subwoofer build:

If you want to make a compact subwoofer these drivers are hard to beat, but if they are to big for your needs Tang Band also offers a 5.25" version, the W5:

Tang Band W5

#9 Eminence

How about another made in the USA brand?  Eminence, made in the small town of Eminence, Kentucky.  This brand is best known for making guitar amp speakers.  But, they produce drivers for many different companies and applications. Just click on this pic and look at the stats on the 12C!  This is a nice subwoofer: 

Eminence Lab 12C

#10 SKAR

SKAR is known for making powerful subwoofers at bargin prices.  They provide excellent bass for the buck and have gotten very popular over the last few years.  As best we can tell SKAR is copying the look you would find on a Sundown and DC Audio, but doing it much, much cheaper.  They also have a line of affordable amplifiers.   Check out this 15" subwoofer it is an ABSOLUTE MONSTER!

 

SKAR ZVX 15"

Is this the end of the list?

Of course not!  There are TONS of awesome subwoofer brands that most people have never heard of.  Which ones did we miss?  Leave a comment and tell us about them!

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