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Subwoofers
10 big bass secrets
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<blockquote data-quote="dragon.breath" data-source="post: 8103433" data-attributes="member: 582656"><p><a href="http:////forums/usertag.php?do=list&amp;action=hash&amp;hash=4" target="_blank">#4</a> . ENCLOSURE EFFICIENCY</p><p></p><p>How do those competition cars hit such high numbers</p><p></p><p>with only one woofer?</p><p></p><p>Most of the answer lies in the box design. You CAN add</p><p></p><p>over 10 decibels of output with these methods.</p><p></p><p>Subwoofer box efficiency comes from a few things.</p><p></p><p>Secret:</p><p></p><p>Tuning frequency</p><p></p><p>Finding the best tuning frequency for your</p><p></p><p>competition enclosure takes a lot of work. First you</p><p></p><p>have to plot your cabin gain. How much gain does the</p><p></p><p>interior of your add to low frequencies? How much</p><p></p><p>gain does your subwoofer enclosure give you? Sum the</p><p></p><p>gain from the car and the box looking for the</p><p></p><p>frequency with the biggest numbers and you have it.</p><p></p><p>Port size</p><p></p><p>Subwoofers love to load with their environment and</p><p></p><p>their ports, which in turn load with the environment.</p><p></p><p>The best way for a woofer too see its port is by making</p><p></p><p>it big. Sounds like common sense right. When you</p><p></p><p>increase the surface area of your port, you increase the</p><p></p><p>efficiency of your enclosure. Having a small port is like</p><p></p><p>asking a small woofer to cycle at many inches of</p><p></p><p>excursion. This makes for unhappy woofers as well as</p><p></p><p>unhappy ports. This is why there are big woofers. They</p><p></p><p>are more efficient and need to throw a fraction of the</p><p></p><p>distance. When you make a port as big as you can, you</p><p></p><p>are increasing its capacity to move air. more air means</p><p></p><p>more pressure. Keep in mind, larger ports can get</p><p></p><p>really long.</p><p></p><p>Similar to porting and polishing an intake for a car,</p><p></p><p>make sure your port walls are smooth.</p><p></p><p>And here's two more efficiency secrets. Port bends</p><p></p><p>decrease enclosure efficiency. If you must bend, make</p><p></p><p>them smooth. Also, port width to height ratio should</p><p></p><p>be close. this means a 6 inches wide and six inches tall</p><p></p><p>(square) opening is ideal compared to a 3 x 12. Same</p><p></p><p>surface area but much more port wall surface area</p><p></p><p>decreases efficiency. The most efficient port will be</p><p></p><p>round, as big as you can make it,</p><p></p><p>Enclosure size</p><p></p><p>Why do club speakers kick so hard? Why does my</p><p></p><p>woofers manual say to put it in a small 1 cubic foot</p><p></p><p>enclosure?</p><p></p><p>Secret:</p><p></p><p>Big enclosure, Big output.</p><p></p><p>As previously mentioned, early car subwoofers were</p><p></p><p>pro-sound drivers. Enclosures were huge, and so was</p><p></p><p>efficiency. Your car woofer might only need 1 cubic</p><p></p><p>foot to perform says the manufacturer, because they</p><p></p><p>figure space is at a premium. A car is significantly</p><p></p><p>smaller than a club where enclosure size is rarely a</p><p></p><p>consideration.</p><p></p><p>At a certain box volume, a subwoofer enclosure will</p><p></p><p>begin to exhibit a high q. This means that its output</p><p></p><p>will begin to raise in a narrow band of frequencies at its</p><p></p><p>box resonance, as box volume raises. Let's say your</p><p></p><p>subwoofer system response is flat in 3 feet ported. If</p><p></p><p>you jump to 4 feet and keep the same subwoofer and</p><p></p><p>tuning, you will begin adding gain, like I said, in a</p><p></p><p>narrow band at the box resonance. This is called</p><p></p><p>�€ï¿½boomy�€ï¿½ by some, and is undesirable for sq, but</p><p></p><p>perfect for spl. Up to a point, increasing enclosure</p><p></p><p>volume will increase but narrow this band of</p><p></p><p>frequencies until it matches box tuning frequency. You</p><p></p><p>can dial in as little or as much gain as you want up to a</p><p></p><p>point. I have seen designs with over 15 decibels of</p><p></p><p>gain!!! Playing with enclosure modeling software, you</p><p></p><p>can find the perfect enclosure volume / gain ratio.</p><p></p><p>.</p><p></p><p><a href="http:////forums/usertag.php?do=list&amp;action=hash&amp;hash=3" target="_blank">#3</a> . ENCLOSURE CONSTRUCTION</p><p></p><p>What should I build it out of? Does shape matter?</p><p></p><p>The construction of your enclosure is as important as</p><p></p><p>subwoofer selection, amplifier selection and</p><p></p><p>everything else.</p><p></p><p>Secret:</p><p></p><p>Port placement (previously discussed and elaborated)</p><p></p><p>Can I place my ports anywhere?</p><p></p><p>Lets explore this one plane idea further. I suggested</p><p></p><p>that your woofers and ports all be there. Why? Because</p><p></p><p>of phase. Because a port is an addition to the radiating</p><p></p><p>surface of your woofers. Porting an enclosure is like</p><p></p><p>adding another small woofer. You want all your bass</p><p></p><p>notes to reach your ears at the same time right? It</p><p></p><p>doesn't matter if it comes from ports or actual woofers,</p><p></p><p>this sound pressure needs to be in timing/phase or it</p><p></p><p>will not provide proper impact. As it turns out, you can</p><p></p><p>only achieve proper port function if it is on the same</p><p></p><p>plane as the woofer because they work together.</p><p></p><p>Placing the port and woofer on different planes</p><p></p><p>reduces their coupling, always reducing output and or</p><p></p><p>accuracy. Never run ports through your rear deck or</p><p></p><p>rear seats unless you have a single-reflex bandpass.</p><p></p><p>Ports should be at least its diameter from the rear wall</p><p></p><p>and sides of box, no bends, very smooth and with</p><p></p><p>flared ends. This section is as good as gold. USE THIS</p><p></p><p>INFO!!!</p><p></p><p>Enclosure seal</p><p></p><p>A subwoofer system can create plenty of pressure, and</p><p></p><p>if it is lost through a leaky enclosure, your output will</p><p></p><p>suffer. Your woofers output needs to radiate from two</p><p></p><p>places, the woofers cone, and the tuned port. A tuned</p><p></p><p>port will increase output within a given range of</p><p></p><p>frequencies, but a hole in the enclosure acts like a high</p><p></p><p>pass filter, at a very high frequency, eliminating your</p><p></p><p>bass!</p><p></p><p>Enclosure rigidity</p><p></p><p>A subwoofer can be a powerful device. In an enclosure,</p><p></p><p>it pressurizes and rarifies air. This can be compromised</p><p></p><p>by a flimsy enclosure. A subwoofer system needs to be</p><p></p><p>rigid so that the sound pressure it creates is not</p><p></p><p>undermined by changing enclosure volumes.</p><p></p><p>Build your enclosure out of the thickest wood you can.</p><p></p><p>3/4 inch MDF is usually a good starting point.</p><p></p><p>MDF will be a little stronger and damped but will be</p><p></p><p>prone to water damage. 1 inch wood is expensive but</p><p></p><p>could be your best choice for a real competition</p><p></p><p>system. In either case, here are some construction</p><p></p><p>secrets.</p><p></p><p>Never make any length more than double any other</p><p></p><p>length. Woofers don't like this</p><p></p><p>Never make your enclosure perfectly square.</p><p></p><p>Subwoofers don't like this either. It can cause</p><p></p><p>undesirable variations in your frequency response.</p><p></p><p>Brace your walls. Add a 2x4or a slice of your sheet</p><p></p><p>across the two largest panels. We don't want these</p><p></p><p>large panels to flex.</p><p></p><p>Pre-drill holes and countersink.</p><p></p><p>If you pre-drill your screw holes, there will be a</p><p></p><p>minimal chance of splitting the wood. Particleboard is</p><p></p><p>susceptible to this but MDF even moreso. Countersink</p><p></p><p>your screw heads to make a nice clean finish that will</p><p></p><p>accept upholstering much nicer.</p><p></p><p>Screws should be spaced about 10 inches apart for</p><p></p><p>good strength.</p><p></p><p>Adhesives.</p><p></p><p>I like to use a good construction adhesive for my</p><p></p><p>enclosures. The great thing about these ugly brown</p><p></p><p>tubes is that they add strength, even stronger than the</p><p></p><p>wood itself, plus they seal the box as they glue. Spread</p><p></p><p>a bead across all joints after you have drilled holes and</p><p></p><p>countersinks. Don't miss a spot or your box will leak air.</p><p></p><p>Alternatively, You can use wood glue and this is</p><p></p><p>common but you will need to run a bead of pure</p><p></p><p>silicone inside the box on all seams. This method</p><p></p><p>requires a little more work and will not be as strong.</p><p></p><p>The difference between construction adhesive and</p><p></p><p>wood glue is how hard it dries. Wood glue dries so hard</p><p></p><p>it will snap under pressure. Construction adhesive will</p><p></p><p>not.</p><p></p><p>Sealant.</p><p></p><p>I'm not talking about silicone this time. I'm talking</p><p></p><p>about making your Enclosure waterproof. This will</p><p></p><p>extend the life of your enclosure exponentially.</p><p></p><p>Particleboard and especially MDF don't like water. MDF</p><p></p><p>is actually a paper product. Both of these will swell and</p><p></p><p>disintegrate if exposed.</p><p></p><p>I always paint mine. Ask your local home store paint</p><p></p><p>department what they have that's waterproof. Buy</p><p></p><p>whats in your budget. You will probably be covering</p><p></p><p>your enclosure with carpet or vinyl anyway, so color is</p><p></p><p>of no importance. You can use a clear water seal, or</p><p></p><p>even a paint or primer.</p><p></p><p>A premium method of sealing your enclosure that will</p><p></p><p>be cosmetic at the same time is bed-liner. You can pick</p><p></p><p>some up at the auto parts store or you can have it</p><p></p><p>professionally done. The results from the pro's will be</p><p></p><p>much nicer looking but both do a great job of sealing</p><p></p><p>and protecting your enclosure.</p><p></p><p>Screws</p><p></p><p>I use 1.5 inch black coarse thread drywall screws for</p><p></p><p>my enclosures when I use 3/4 inch wood. This assures</p><p></p><p>the perfect grab on both pieces. The finish on the black</p><p></p><p>screws assures they won't come loose. They are strong,</p><p></p><p>economical, and easy to find.</p><p></p><p>Your subwoofer might require something more</p><p></p><p>serious. I will usually make the face of my enclosure</p><p></p><p>double thick and use extra long and thick screws. Don't</p><p></p><p>forget to pre-drill holes for your screws that are just</p><p></p><p>smaller than the diameter of your screws minus the</p><p></p><p>threads. This will hold a heavy subwoofer. If you can,</p><p></p><p>find some bolts and spiked T-nuts. This is a serious</p><p></p><p>approach for the most demanding applications.</p></blockquote><p></p>
[QUOTE="dragon.breath, post: 8103433, member: 582656"] [URL="http:////forums/usertag.php?do=list&action=hash&hash=4"]#4[/URL] . ENCLOSURE EFFICIENCY How do those competition cars hit such high numbers with only one woofer? Most of the answer lies in the box design. You CAN add over 10 decibels of output with these methods. Subwoofer box efficiency comes from a few things. Secret: Tuning frequency Finding the best tuning frequency for your competition enclosure takes a lot of work. First you have to plot your cabin gain. How much gain does the interior of your add to low frequencies? How much gain does your subwoofer enclosure give you? Sum the gain from the car and the box looking for the frequency with the biggest numbers and you have it. Port size Subwoofers love to load with their environment and their ports, which in turn load with the environment. The best way for a woofer too see its port is by making it big. Sounds like common sense right. When you increase the surface area of your port, you increase the efficiency of your enclosure. Having a small port is like asking a small woofer to cycle at many inches of excursion. This makes for unhappy woofers as well as unhappy ports. This is why there are big woofers. They are more efficient and need to throw a fraction of the distance. When you make a port as big as you can, you are increasing its capacity to move air. more air means more pressure. Keep in mind, larger ports can get really long. Similar to porting and polishing an intake for a car, make sure your port walls are smooth. And here's two more efficiency secrets. Port bends decrease enclosure efficiency. If you must bend, make them smooth. Also, port width to height ratio should be close. this means a 6 inches wide and six inches tall (square) opening is ideal compared to a 3 x 12. Same surface area but much more port wall surface area decreases efficiency. The most efficient port will be round, as big as you can make it, Enclosure size Why do club speakers kick so hard? Why does my woofers manual say to put it in a small 1 cubic foot enclosure? Secret: Big enclosure, Big output. As previously mentioned, early car subwoofers were pro-sound drivers. Enclosures were huge, and so was efficiency. Your car woofer might only need 1 cubic foot to perform says the manufacturer, because they figure space is at a premium. A car is significantly smaller than a club where enclosure size is rarely a consideration. At a certain box volume, a subwoofer enclosure will begin to exhibit a high q. This means that its output will begin to raise in a narrow band of frequencies at its box resonance, as box volume raises. Let's say your subwoofer system response is flat in 3 feet ported. If you jump to 4 feet and keep the same subwoofer and tuning, you will begin adding gain, like I said, in a narrow band at the box resonance. This is called �€ï¿½boomy�€ï¿½ by some, and is undesirable for sq, but perfect for spl. Up to a point, increasing enclosure volume will increase but narrow this band of frequencies until it matches box tuning frequency. You can dial in as little or as much gain as you want up to a point. I have seen designs with over 15 decibels of gain!!! Playing with enclosure modeling software, you can find the perfect enclosure volume / gain ratio. . [URL="http:////forums/usertag.php?do=list&action=hash&hash=3"]#3[/URL] . ENCLOSURE CONSTRUCTION What should I build it out of? Does shape matter? The construction of your enclosure is as important as subwoofer selection, amplifier selection and everything else. Secret: Port placement (previously discussed and elaborated) Can I place my ports anywhere? Lets explore this one plane idea further. I suggested that your woofers and ports all be there. Why? Because of phase. Because a port is an addition to the radiating surface of your woofers. Porting an enclosure is like adding another small woofer. You want all your bass notes to reach your ears at the same time right? It doesn't matter if it comes from ports or actual woofers, this sound pressure needs to be in timing/phase or it will not provide proper impact. As it turns out, you can only achieve proper port function if it is on the same plane as the woofer because they work together. Placing the port and woofer on different planes reduces their coupling, always reducing output and or accuracy. Never run ports through your rear deck or rear seats unless you have a single-reflex bandpass. Ports should be at least its diameter from the rear wall and sides of box, no bends, very smooth and with flared ends. This section is as good as gold. USE THIS INFO!!! Enclosure seal A subwoofer system can create plenty of pressure, and if it is lost through a leaky enclosure, your output will suffer. Your woofers output needs to radiate from two places, the woofers cone, and the tuned port. A tuned port will increase output within a given range of frequencies, but a hole in the enclosure acts like a high pass filter, at a very high frequency, eliminating your bass! Enclosure rigidity A subwoofer can be a powerful device. In an enclosure, it pressurizes and rarifies air. This can be compromised by a flimsy enclosure. A subwoofer system needs to be rigid so that the sound pressure it creates is not undermined by changing enclosure volumes. Build your enclosure out of the thickest wood you can. 3/4 inch MDF is usually a good starting point. MDF will be a little stronger and damped but will be prone to water damage. 1 inch wood is expensive but could be your best choice for a real competition system. In either case, here are some construction secrets. Never make any length more than double any other length. Woofers don't like this Never make your enclosure perfectly square. Subwoofers don't like this either. It can cause undesirable variations in your frequency response. Brace your walls. Add a 2x4or a slice of your sheet across the two largest panels. We don't want these large panels to flex. Pre-drill holes and countersink. If you pre-drill your screw holes, there will be a minimal chance of splitting the wood. Particleboard is susceptible to this but MDF even moreso. Countersink your screw heads to make a nice clean finish that will accept upholstering much nicer. Screws should be spaced about 10 inches apart for good strength. Adhesives. I like to use a good construction adhesive for my enclosures. The great thing about these ugly brown tubes is that they add strength, even stronger than the wood itself, plus they seal the box as they glue. Spread a bead across all joints after you have drilled holes and countersinks. Don't miss a spot or your box will leak air. Alternatively, You can use wood glue and this is common but you will need to run a bead of pure silicone inside the box on all seams. This method requires a little more work and will not be as strong. The difference between construction adhesive and wood glue is how hard it dries. Wood glue dries so hard it will snap under pressure. Construction adhesive will not. Sealant. I'm not talking about silicone this time. I'm talking about making your Enclosure waterproof. This will extend the life of your enclosure exponentially. Particleboard and especially MDF don't like water. MDF is actually a paper product. Both of these will swell and disintegrate if exposed. I always paint mine. Ask your local home store paint department what they have that's waterproof. Buy whats in your budget. You will probably be covering your enclosure with carpet or vinyl anyway, so color is of no importance. You can use a clear water seal, or even a paint or primer. A premium method of sealing your enclosure that will be cosmetic at the same time is bed-liner. You can pick some up at the auto parts store or you can have it professionally done. The results from the pro's will be much nicer looking but both do a great job of sealing and protecting your enclosure. Screws I use 1.5 inch black coarse thread drywall screws for my enclosures when I use 3/4 inch wood. This assures the perfect grab on both pieces. The finish on the black screws assures they won't come loose. They are strong, economical, and easy to find. Your subwoofer might require something more serious. I will usually make the face of my enclosure double thick and use extra long and thick screws. Don't forget to pre-drill holes for your screws that are just smaller than the diameter of your screws minus the threads. This will hold a heavy subwoofer. If you can, find some bolts and spiked T-nuts. This is a serious approach for the most demanding applications. [/QUOTE]
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