Menu
Forum
What's new
New posts
Live Activity
Search forums
Members
Registered members
Classifieds Member Feedback
Car Audio Discussion
General Car Audio
Car Audio Build Logs
Car Audio Equipment
Subwoofers
Speakers
Amplifiers
Head Units
Car Audio Help
Wiring, Electrical and Installation
Enclosure Design & Construction
Car Audio Classifieds
Car Audio Classifieds
Car Audio Wanted
Classifieds Member Feedback
Gallery
New media
New comments
Search media
SHOP
Shop Head Units
Shop Amplifiers
Shop Speakers
Shop Subwoofers
Shop eBay Car Audio
Test
Forum
Search
Search titles only
Search titles only
Log in / Join
Search
Search titles only
Search titles only
What's new
New posts
Live Activity
Search forums
Members
Registered members
Classifieds Member Feedback
Menu
Reply to thread
Forum
Car Audio Help
Enclosure Design & Construction
PV Audio's guide to enclosure types!
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Message
<blockquote data-quote="PV Audio" data-source="post: 6506539" data-attributes="member: 554493"><p>Ported Enclosures</p><p></p><p>Ahh yes, the bread and butter of the car audio world for reasons most do not understand. Believe it or not, throwing any speaker into a ported enclosure will NOT necessarily make it perform better. To determine what speaker is suited for a ported enclosure, you'll need to be looking at the Qts again. This time, we're going for OVERDAMPED speakers, or speakers with Qts values below .5. Why? Well, these speakers don't tend to oscillate freely and potentially out of control like under damped speakers do, so by placing them in a sealed enclosure, you're essentially doing the woofer's job for it. That is horribly inefficient and a waste of time. Instead, people use ported enclosures to gain some extra output since the speaker can handle it without hurting itself. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif</p><p></p><p>The main precaution surrounding ported enclosures is the fact that you need to design the enclosure around the driver, NOT the other way around. Going out and getting a pre fabricated enclosure is one of the worst things that you can do to a subwoofer. It won't necessarily sound poor, but there is no way it's suited for that specific speaker. How do you know what is suited for your speaker? Good question! You're going to need those tables I talked about earlier, except this time, instead of looking for a Qtc value that you like, you're going to look for a Ql value, or a loss Quality. Ported boxes have losses that you need to take into account. The average loss value is 7, and while this isn't very practical for most people it's the best method: construct the enclosure with QL of 7 in mind, then tune it to the frequency that you calculate (later). Afterwards, try to measure the box for losses and if you're pretty close to neutral, then you're good to go! If not, then here's the rule of thumb: if you have LESS LOSS or a HIGHER Ql, then decrease the Vb. If you have MORE LOSS or a LOWER Ql, then increase the size of the box. Think about it like this: you build a container to hold a cup of water. The higher the quality of the container, the less water that will be draining out. The lower the quality, the more water you'll need to put in and thus you'll need a larger container. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif</p><p></p><p>Now, I know most of you guys are like pffft, I'm not wasting time on that, I'm just going to plug some numbers into a computer and get what I want. Not so fast, slick. You need to understand why your computer is giving you the given values. Your Vb is equal to the Vas/alpha. Alpha in this case CAN be derived, but that formula is going to take too long to derive, so just assume that it's a constant between around .1 and 4 for a normal Ql = 7 enclosure. Your tuning frequency is equal to the driver's Fs * H, where H is the tuning ratio for your given alignment. Now assuming that you have all of this, you can calculate your theoretical port length which is easier to see via a website:</p><p></p><p><a href="http://www.diysubwoofers.org/misc/portcal.htm" target="_blank">http://www.diysubwoofers.org/misc/portcal.htm</a></p><p></p><p>I realized about halfway through this that it's quite difficult to have a short theoretical basis on ported enclosures because the science is pretty hairy and you need at least a moderate understanding of physics to fully grasp the concepts. Seeing as most people just want a good enclosure, the quick and dirty steps are to use the tuning and minimum diameter formulas to find those respective parameters, then find the volume that you want by the Vas/alpha formula by looking up alpha in a design table, or calling the manufacturer and asking them. They'll know exactly what it should be and can help you if you need anything else. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif</p><p></p><p>I know this post wasn't very helpful, which is why I added the last part. It's very difficult to go into the theory without you seeing the design tables, and it's even MORE difficult to understand if you want the formulae behind the design tables because they are far too long to write out in one-line text //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif</p><p></p><p>I'll make the next post a bit better //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif</p></blockquote><p></p>
[QUOTE="PV Audio, post: 6506539, member: 554493"] Ported Enclosures Ahh yes, the bread and butter of the car audio world for reasons most do not understand. Believe it or not, throwing any speaker into a ported enclosure will NOT necessarily make it perform better. To determine what speaker is suited for a ported enclosure, you'll need to be looking at the Qts again. This time, we're going for OVERDAMPED speakers, or speakers with Qts values below .5. Why? Well, these speakers don't tend to oscillate freely and potentially out of control like under damped speakers do, so by placing them in a sealed enclosure, you're essentially doing the woofer's job for it. That is horribly inefficient and a waste of time. Instead, people use ported enclosures to gain some extra output since the speaker can handle it without hurting itself. [IMG]//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif[/IMG] The main precaution surrounding ported enclosures is the fact that you need to design the enclosure around the driver, NOT the other way around. Going out and getting a pre fabricated enclosure is one of the worst things that you can do to a subwoofer. It won't necessarily sound poor, but there is no way it's suited for that specific speaker. How do you know what is suited for your speaker? Good question! You're going to need those tables I talked about earlier, except this time, instead of looking for a Qtc value that you like, you're going to look for a Ql value, or a loss Quality. Ported boxes have losses that you need to take into account. The average loss value is 7, and while this isn't very practical for most people it's the best method: construct the enclosure with QL of 7 in mind, then tune it to the frequency that you calculate (later). Afterwards, try to measure the box for losses and if you're pretty close to neutral, then you're good to go! If not, then here's the rule of thumb: if you have LESS LOSS or a HIGHER Ql, then decrease the Vb. If you have MORE LOSS or a LOWER Ql, then increase the size of the box. Think about it like this: you build a container to hold a cup of water. The higher the quality of the container, the less water that will be draining out. The lower the quality, the more water you'll need to put in and thus you'll need a larger container. [IMG]//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif[/IMG] Now, I know most of you guys are like pffft, I'm not wasting time on that, I'm just going to plug some numbers into a computer and get what I want. Not so fast, slick. You need to understand why your computer is giving you the given values. Your Vb is equal to the Vas/alpha. Alpha in this case CAN be derived, but that formula is going to take too long to derive, so just assume that it's a constant between around .1 and 4 for a normal Ql = 7 enclosure. Your tuning frequency is equal to the driver's Fs * H, where H is the tuning ratio for your given alignment. Now assuming that you have all of this, you can calculate your theoretical port length which is easier to see via a website: [URL="http://www.diysubwoofers.org/misc/portcal.htm"]http://www.diysubwoofers.org/misc/portcal.htm[/URL] I realized about halfway through this that it's quite difficult to have a short theoretical basis on ported enclosures because the science is pretty hairy and you need at least a moderate understanding of physics to fully grasp the concepts. Seeing as most people just want a good enclosure, the quick and dirty steps are to use the tuning and minimum diameter formulas to find those respective parameters, then find the volume that you want by the Vas/alpha formula by looking up alpha in a design table, or calling the manufacturer and asking them. They'll know exactly what it should be and can help you if you need anything else. [IMG]//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif[/IMG] I know this post wasn't very helpful, which is why I added the last part. It's very difficult to go into the theory without you seeing the design tables, and it's even MORE difficult to understand if you want the formulae behind the design tables because they are far too long to write out in one-line text [IMG]//content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif[/IMG] I'll make the next post a bit better [IMG]//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif[/IMG] [/QUOTE]
Insert quotes…
Verification
Post reply
Forum
Car Audio Help
Enclosure Design & Construction
PV Audio's guide to enclosure types!
Top
Menu
Home
Refresh