Hoffman's Iron Law states that a woofer's efficiency is proportional to the volume of the enclosure it is mounted in and the cube of its low frequency cutoff. In other words, if you want a loudspeaker with very low frequency extension AND high efficiency, you need an enormous enclosure. Or you could build The Homewrecker.

This Instructable will show you how to build a loudspeaker that can mount in most standard interior doorways, using the room as the enclosure. The system is easily removable, though quite heavy. The system shown here is not a high-fidelity system, but it is very efficient (i.e. LOUD) and can reproduce very low frequencies. Based on the parameters of the woofer, this system should easily reach below 30Hz (-3dB) without including the natural boost obtained from room reflections. With this boost included, the system should reach 20Hz - the lower limit of human hearing. All of this bass extension comes at a very respectable 96dB with a 2.83V input (4 ohms).

It consists of (8) 12' woofers, (8) 5' midranges, (4) 2' x 5' tweeters, a simple crossover and (4) easy to use mounting brackets. The size and number of speakers can be just about anything you want, but this combination utilizes the available space in a doorway quite well.

Step 1: Get Stuff

The following is a list of the components I used for this system, but these exact parts may be difficult to obtain and can be replaced as described below.

- 12" woofers qty 8
- 5" midranges qty 8
- 2"x5" tweeter qty 4
- input terminal qty 2
- 10W resistors qty 2
- 3.3uF non-polarized capacitors qty 2
- 16uF non-polarized capacitors qty 2
- 0.7mH inductors qty 2
- 0.4mH inductors qty 2
- 18 or 16 awg wire qty 50 ft
- 4' x 8' plywood qty 1
- 2 x 4 studs 96" qty 5
- L-brackets qty 4
- 1.25" weather strip qty 17 ft
- 3/8" carriage bolts qty 4
- 3/8" nuts qty 4
- 3/8" wing nuts qty 4
- 3/8" fender washers qty 4
- 3/8" T-nuts qty 4

The midrange and tweeter units were chosen based solely on price. These can be replaced with any midrange and tweeter of your choosing as long as they are wired properly and the sensitivities are matched to each other and the woofers. This can be done in the crossover and will be partially explained later.

The woofer was chosen based on price and a parameter called Qts. This parameter should be available from the speaker retailer and should be between 0.65 and 0.95 for best results. The woofers I'm using have a published Qts of 1.17 which is a little high, but as I said, this particular system is not designed for high-fidelity. The picture below is from the Parts Express website and it has the same specs as the woofers I'm using.

All of these drivers were purchased from the PartsExpress factory buyout section of their website (www.partsexpress.com) for less than $120 total. Better divers would make for a better system, but things get really expensive when you have to buy 8 of each component.

EDIT - 11/23/2010  This (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=292-422) is an excellent woofer to use in the Homewrecker as well.  They are only $13.76 each if you buy 4 or more.  They are less efficient than the original woofers used and you will have to account for this in the mid and tweeter level, but they are 8 ohms which will be easier on your amp.  Plus, I think they look better without the ribs on the cone.
What!??, never mind. <br>Bet it works Great, Thanks.
Nice job but how much does it cost ?&iquest;? <br>&trade;&reg;&copy; <br>  <br>nice <br> 
I was just wondering where you live so I can make sure I never move in next door! <br>;') <br>I'm sure this has made you real popular with the neighbours. <br> <br>That said, I give you full credit for thinking outside the (speaker) box.
One comment here; As shown in the 1st and 3rd photos, I have tried to incorporate a small, childs bike into the build. I believe I am doing it wrong as1) the assembly is totally unbalanced now and 2) the bike can no longer be riden. May have to re-think this step when making the other three assemblies.
Wrong instructable?
1st and 3rd pics show a small kids bike. This being on the 3rd page of this instructible. After thinking about it for a while and drinking some more red table wine, I may have used the wrong type of bicycle. Will try using a tricycle for my second homewrcker. Mabe a mountain bike for the third.......
You are my favorite.<br>
Just a couple of reflections (thoughs)... If Efficiency is a primordial objective, then the use of a Passive Crossover network is not the best selection. The simple first-order (6 dB/octave) crossover used, theoretically produces a 3 dB loss. They call it &quot;Insertion Loss&quot;.-&lt;br/&gt;&lt;br/&gt;For many good reasons, the absolutely best way to go is to go with an ACTIVE crossover and arrive to a BIAMPED system. In such system the woofers are connected directly to the bass amplifier, which avoids the loss caused by the unavoidable resistance of the coil. An additional benefit is that the amp is now able to better control the heavy woofer cone (specially when the magnet size is somewhat small, like the ones in inexpensive drivers like those selected for this project).&lt;br/&gt;As the efficiency using an active crossover rises, the headroom becomes more ample, and the need to use a sufficiently large power amplifier is greatly reduced (a 3dB increase in efficiency means that instead of a (say)100 watt amp, we now need a 50 watt amp. Since today small car audio stereo amps are good sounding enough and relatively inexpensive, by using a, say 50 W amplifier for the low frecuency channel plus a 20 W amp for the mid+high is more than enough (I AM refering to REAL, so called RMS watts). The differences of efficiency and sound level between the low and midrange drivers are easily corrected with the input level controls at each amp.&lt;br/&gt;&lt;br/&gt;2.- The Piezo tweeters can be connected directly to the mid+high amplifier WITHOUT any crossover components, since the capacitive nature of the transducer works exactly like a capacitor, then you don't need the high frecuency capacitor network and the load resistor; it is shown in the schematic only because this crossover network was designed for a Dynamic cone or dome tweeter, which has a typical impedance around 8 to 10 ohms at the typical crossover frecuency.&lt;br/&gt;&lt;br/&gt;The false impression that a Biamped or Tri-amped or Multiamped systems have to be costly, or complex or only for professional use is nonsense! Even a low budget system benefits a lot from at least biamping...&lt;br/&gt;The passive crossover is surely going to produce a widely varying impedance curve that only has the nominal 4 ohm value at two or three frecuency points, varying hugely across the full frecuency range, Phase response will certainly vary tremendously also, because the driver's impedance does vary inmensely (between lower than 4 ohm to higher than 80 ohm or more at the resonance point, and 20 or so ohms at crossover frecuencies because of driver interactions, remember, passive crossovers require resistive terminations of equal impedance to be able to produce a smooth impedance curve. Some amplifiers DO NOT like such impedance excursions.&lt;br/&gt;3.-Why mount all drivers in the same panel??? Stereo image and coverage is destroyed when the speakers pair is not properly arranged to create a Stereo image, usually left and right speakers should form an equilateral triangle between them and the listener... May I humbly suggest that ONLY the woofers are mounted to the panel, creating an effective Sub-Woofer taking advantage of the nice and clever concept of putting those in a panel like you did, but installing the midranges and tweeters in much smaller panels/enclosures mounted in small pedestal bases that rise them to ear level and permit to locate them for a proper Stereo image and be very portable and lightweight. That is called a &quot;subwoofer-satellite system&quot; and is capable of very good results without the need for enormous tower speakers for a nice and balanced system. But for a good result, the crossover frecuency must be below 150 Hz, preferably 100 Hz, since lower frecuencies are not directionally perceived, which allows us to place the subwoofer almost anywhere in the room, and to place the left and right satellite speakers where acoustics, Stereo image and room decoration best fit together. Since now the midrange speaker will have to work from 100 Hz up, a 6&quot; to 8&quot; unit will be required per side (or a pair of good 5&quot; per side) , with its necessary enclosure, which won't need to be large since only below 100 Hz a huge volume is needed (which is already solved by your woofers mounted in the large panel at the room door).&lt;br/&gt;Finally, where do we get a good Active crossover? May I suggest to go to &quot;Elliott Sound Products&quot; website and look for an excellent fourth order (24 dB/octave!) crossover network PCB (printed circuit board) which is a good way to obtain a tryed and tested solution! The owner, Mr. Rod Elliott from Australia sells these PCB's bare and ready to be populated with some really inexpensive IC's, small capacitors and resistors. ANY self respected Instructables reader should be fully capable of assembling and setting an excellent two way, stereo Linkwitz-Riley electronic (active) crossover with an outstanding frecuency and phase response, which combined with a couple of nice sounding inexpensive Alpine (or similar) brand car audio small power amps (a 2X50W RMS unit costs only 50 bucks new, the woofers 2X100 W RMS unit another 70 USD or so), The Active Crossover circuit board is 24 USD plus around 10 dls in IC's and small parts, plus a small aluminum extrusion box for a chassis. If you already have a good small stereo amp, then you can replace one of the car audio amps to save some bucks...&lt;br/&gt;You will also need a 12V DC power supply to feed the car amp(s), but Instructables has a few computer power supplies articles that use old PC's power supplies being rescued at no-cost, and capable of giving more than enough current Amperes to run the amps to full power!&lt;br/&gt;Make no mistake, the system I am describing is not a mediocre sounding pile of pieces, the results of using a Biamped system is so &quot;sound&quot; (no intended pun!) that it rivals ANYTHING costing several times as much. Mine has put to shame some extremely expensive (read over a couple of thousands) big amplifier plus passive large size speakers. (the reason, obviously, is that it is plainly stupid to put A LOT of cash in a large very expensive amplifier that will waste half its power just in teh passive crossover, and that a lot of famous speakers present an horrible load to the amplifier. I cannot make an Instructable of my system or design approach at the moment, because I don't have a decent digital camera and I'm in the middle of moving from an apartment to an old house and my wife is waiting our first baby... maybe next year (I hope..)&lt;br/&gt;Good Luck, I may suggest fully reading Rod Elliott's excellent articles (parts one and two) on Active vs Passive Crossovers, and also on the almost unsurmountable difficulties of making a properly behaving passive crossover (yes, it can be done, with a lot of effort, electronic lab equipment and some years of available time to test, retest, and test again a miriad components and crossover parts values... believe me, been there done that. The Active crossover IS the WAY to GO. A webpage reporting on the relative quality of popular car audio amps is at: &lt;a rel=&quot;nofollow&quot; href=&quot;http://slumz.boxden.com/f359/worst-best-car-audio-brands-419293/&quot;&gt;http://slumz.boxden.com/f359/worst-best-car-audio-brands-419293/&lt;/a&gt;&lt;br/&gt;Good Luck&lt;br/&gt;Alfredo Marquez Claussen, Mexico City. amarquez (aT) i m p dot m x&lt;br/&gt;<br/>
Insertion loss is dependent on the DC resistance of the inductors used in the crossover, which can be very low if you use a ferrite core inductor and will result in a loss much less than 3dB. Also, a piezo tweeter can be used with no crossover if you want to utilize its full low end response as is. If you want to attenuate its bottom end further, a capacitor can be used (chosen by ear in this case). I like your idea of eliminating the high frequency components altogether and using this strictly as a subwoofer system, which could be the only way that this idea could be integrated into any kind of high-end setup (better drivers necessary of course). But then to take advantage, your "satellites" would have to be able to keep up in the output department and your house would have to be set up appropriately to accommodate the placement. The point of this Instructable was to showcase the idea of the temporary infinite baffle to take advantage of the physics of loudspeakers. The drivers and crossover were chosen so that your average Instructables fan could actually try it out for a couple hundred bucks. The design is "stereo" because most people have a receiver with R + L speaker outputs. The core objective of this specific design was best summed up by BBBS: "One day I'm going to make this and declare a seriously loud party." Well said BBBS. You can lug the monstrosity out for a party, blow everyone's faces off and then put it away when you're done. This also has the advantage of completely restricting access to a bedroom, which can be very valuable depending on the crowd.
First of all: my comments were not intended as a critique of your nice instructable, and tried to be constructive. I believe there is a tremendous potencial in using a room as an enclosure in a way similar to an Infinite Baffle, specially as a Subwoofer one. I was just trying to imagine how to get from there to a very good-but still inexpensive system by Bi-amping it. Using Satellites instead of not-large-enough floor standing speaker boxes has been a great success for me. As I wrote, I do not like passive crossovers, because I've seen many speakers fail miserably just because of their interactions, During the years, I've built maybe two or three dozen crossover prototypes trying to succeed, but my efforts were above 90% failed ones, even using lab equipment at my work and the best books available at the time. No anymore! For me, to go ACTIVE is the way! (and I was just trying to save some fellows the same time wasting approach).I was also trying to highlight the fact that a large very expensive &quot;esoteric&quot; power amplifier connected to large and complex passive crossovers is the only way to go (because it has been the usual way for too many years). With Multiamping, small inexpensive amplifiers are more than enough. Now, on pasive crossovers; To properly work, impedance values must match at the crossover frecuency, which is not often the case. I have seen (and measured) too many systems assembled by various people that sounded horrible and presented a very funny impedance curve to the amplifier because the crossover used was a &quot;generic&quot; design where no real data for the drivers was used at all (or using the &quot;ideal&quot; 8-ohm (or 4 ohm nominal values) that are not presented by the drivers at the intended crossover points. With some luck, a passive crossover it will be acceptable and first order designs can be somewhat adjusted by ear, but most of the time, it won't. The impedances of the low, mid and high frec drivers should be equal for the theoretical crossover to properly work, (it is like a pipe network in a house, where if it has three bathrooms, and one of them is located ina lower floor, it is going to have more pressure (and more water flow) when its shower valve opens than the other bathrooms. A passive crossover relies on proper termination at all the outputs to behave correctly, and this is difficult at best. In the case of your design, using a Piezo tweeter solves some of the problems because it has a very high impedance at the crossover point, thus the tweeter resistor can emulate a correct impedance value. But I don't see how to match the 4 ohm woofer set to the 8 ohm midranges. Being 6 dB/octave surely helps, and using a not too low crossover frecuency also helps, but a beginner could interprete that any generic brand crossover that can be found in some store is going to work properly regardless fo the drivers impedance curves. This is where an ACTIVE crossover plays its magic! It is very easy to properly load the output branches of an active crossover since it is loaded in an almost resistively manner. No longer we depend on chance or interminable hours in the lab trying to &quot;match&quot; drivers impedances and relative efficiencies. With now available car amplifiers putting honest 25 watts RMS per channel at 4 ohms, we can drive midranges beautifully, and woofers can have a 100 watt per channel amp easily. By Biamping the system with a Do-It-Yourself Active Crossover, specially the very good one mentioned in my post, excellent results can be obtained easily and for shure. The Fouth Order 24 dB/oct Linkwitz-Rilley alignement gives flat frec response and phase response also, and really produces a sharp separation between drivers. I also don't like to use any cored inductor, because I've seen (and heard) them distort badly when compared to air cored ones, which necessarily become large and need large gauge wire to keep DC resistance acceptably low (but nevertheless significant). Damping factor is also going to be lowered by the DC resistance, and because the woofer is not damped by the large volume of air in the room, a better behaviour can be obtained with a direct connection to the amp (no inductor in series with the voice coil).<br/>Lastly, I had an idea somewhat similar to your Instructable some years ago, but never tried it: the house I'm living in now, has a functional Fireplace (we call it &quot;a chimmey&quot;) that is built of concrete and heavy bricks. I am wondering how to use that Fireplace and its long (about 19 feet) vertical duct to house a kind of Labyrinth or &quot;Transmission Line&quot; enclosure, that reportedly has an excellent low frecuency response. Even a low frecuency horn loaded woofer could be housed... Your Instructable gives me a very strong motivation to investigate and build something in that direction! And Congratulations on your prize winning Homewrecker. I thought of participating in the contest, but my idea was to write a kind of design summary for a Sound System, to try to show others what I have learned tru some years of making all kind of baffles and enclosures, and to try to Share my experiences, after many attempts, some terrible, many mediocre and a few barely acceptable, now my multi-amplified system really satisfies me and most of my friends (some are musicians, some are professional sound engineers, which is certainly reassuring). Sharing is essential because it sums the efforts of many people working towards a common end. Thats why I enjoy Instructables!<br/>I am happy that some people found the idea stimulating towards using a closet as a Subwoofer enclosure (a good idea indeed), and that mikee69 even found the website of Mr. Rod Elliott (http://sound.westhost.com/projects-3.htm) even calling it &quot;a goldmine of electronics info&quot; which I fully and absolutely agree! And I invite you and all the gang to visit to read about the Passive vs Active crossover matters. I'm making a pair of Headphone amplifiers based on their circuit cards, a portable and a home, hi quality one.<br/>
O.0 big words. lol
Ya. I feel ashamed by only knowing the word pneumonoultramicroscopicsisicovolcanoconiosis
But do you know what <span style="font-weight: bold;">d</span>ichloro<b>d</b>iphenyl<b>t</b>richloroethane is?<br />
Pardon my ignorance...<br /> What is the connection of the DDT to the Homewrecker???
Enough DDT will also wreck your home/marriage etc :)
do you know what pneumonoultramicroscopicsilicavolvanoconiosis is?
It's spelled Pneumonoultramicroscopicsilicovolcanoconiosis. Just FYI
It is a lung disease caused by exposure to the dust particles from a volcano, it is also the longest word in the English language.
nice, spot on. extra credit for the tidbit about being the longest word
it is an&nbsp; insecticide used to control mosquito-borne malaria.<br />
yeah... tl;dr<br />
Just a little advice: Aerate.<br>That comment is very, very, painfull to read.<br>Hitting the &quot;enter&quot; key every once and a while never hurt anyone. I am sure that there is some very good information in there, but because of the presentation, nobody will read it. i didnt get past the third line.<br><br>So, Aerate. Good advice when typing up anything, and especially a comment.
Let me reiterate, i think im now the only person to have read it all.<br>You do have some very good stuff written, but it is painfull to read (i put it into http://www.spreeder.com/app.php?intro=1<br>Which makes it quite lesible. Also, makes me not waste 2 hours reading it :)
Holy S**t BIG WORDS!!!! Pneumonoultramicroscopicsilicavolvanoconiosis
Hear, hear! Well, maybe unless you go deaf listening to that monster.
now do you have to make one this huge or could you just like half everything so you have 4 woofers 4 midis and 2 tweeters and like make a box for it??
P.S. YOU LOST ME At JUST!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
P.P.S.<br><br>I LOST THE GAME!
I hate you now, you made me lose the game too:)
you made me lose :(
for those who don't know http://en.wikipedia.org/wiki/The_Game_%28mind_game%29
Just a couple thoughts?
The Elliott Sound site is a good source for phase compensated active crossover circuit boards.<br><br>If you want real efficiency, then dispense with the crossover (or need for one) altogether: http://www.commonsenseaudio.com/nirvana.html Some of these designs exceed the theoretical efficiency of this design, though no match for SPL (given enough power).<br><br>One thing I don't see listed as a benefit of active crossovers is the decided decrease in intermodulation distortion.<br><br>I have serious doubts that a rescued ATX PSU could begin to supply enough current to run a conventional car audio amp of any substantial size. You might want to check Parts Express (same place DiscoJones got his speakers) for some &quot;T Amps&quot;. They are wicked efficient.<br><br>Finally, as cogent and detailed as your arguments are, I feel they are beside the point. This isn't about fidelity. It's not even stereo. It's more like the old Cerwin Vega ads: Loud. Speaker.
&quot;This Instructable will show you how to build a loudspeaker that can mount in most standard interior doorways, using the room as the enclosure. &quot;<br><br>WOW. Never thought of that. What a wonderful, partially working, way to baffle. It'd be nice if you could line the sides and make a seal with standard doors.
holy... whats it like standing near it?
hei m a total noob, and i have no idea how to attach many speaker as one sound system. I assue there are different watt speakers but i have no idea what/how it affects my sound system if i attach 3-4 different speakers. please help
How could I mount these in the bed of my truck for campground parties? I own my own large plot of property...so no nasty neighbors, and this wouold be so much better than the boombox I currently use. Besides, they would look amazing in my F-150!
my sound ystem (above) doesn't need to be portable i can just turn it up so we can hear it.
WILL work: build it as a bed cover. Hell - build TWO of them for stereo. You might experiment with replacing the tailgate with some sort of ports, but you wouldn't have to.
you might get a used bed cover and route it out to hold the set up.
Won't work, but <a rel="nofollow" href="http://www.realmofexcursion.com/">http://www.realmofexcursion.com/</a> is a place to look.<br/><br/>Mike<br/>
If you want something really nice looking (yea it costs more but it will look more professional) you could take a plastic bag and line you truck bed with it, then fill it up with expandable foam (or just make an outline of your bed with tin foil, foam is just the lazy way) then cut holes in the foam for speakers, fiberglass the top. I don't remember what to use to dissolve the foam, its either rubbing alcohol, paint thinner or lighter fluid, but in any case you free up your mold (if its tin foil it should just peel off. then cut any loose ends and make it look neat, then sand prime and paint. and... bam a removable lightweight speaker box that fits perfectly in you truck. Just make some small holes on the edges and find some fasteners like on truck shells
Just build yourself a jig. Draw out some plans that would hold it in place in your truck. You would probably want to have an external power source other than your truck's battery if you want to run this for an extended period of time. That is, if you want to leave the party. ;)
20 speakers wow. <br>31 even mor wow the amp is not powerful enough so the power led dims and rearly the sound cuts out but is still is really cool. <br>your sound system is cool like mine
police got called 4 times and i broke 3 or 4 windows this thing is loud<br>
if you did that with some rocksford fostgates itd make you cry :D btw this is an amazing idea!!!
hey if for some very strange reason there are no vents you could open the window, except you neighbors might not be so appreciative of your diy work as you are...
...but standing next to a window after a shower would easily dry your hair plus give you a new haircut :)
Amarquez raises some excellent points. Yes it's a little deep, but even if you took away nothing more than active crossover, your system would have effective power DOUBLE that of passive crossovers. Think of how many burgers you'd have to flip to make that much money.<br><br>A room has plenty of cubic feet of air for an infinite baffle.<br><br>3vil g3nius, it's been my experience that 18&quot; speakers are not nearly as good as 15&quot; speakers, even in high efficiency enclosures such as Carlsons. 18's are inefficient, and have TERRIBLE damping factors. Their only reason for existence is for those who believe that size matters. 10&quot; speakers are even better, and even much smaller speakers are better, providing you use enough of them. You'll rarely (if ever) find 18&quot;s in professional bass guitar setups. The king of bass amps, the Ampeg SVT, uses 8x 10&quot; speakers.<br><br>For my &quot;earthquake&quot; rig, I use a 15&quot; rear ported bass reflex cab, face down on my equipment dolly, as a floor firing subwoofer. I can knock glasses off the bar.<br><br>I recall a resonant column speaker that used sewer pipe, and a time when audiophiles built coffin sized resonant columns subs in their basements, and made special efforts to find recordings with enough deep bass to make 'em sound off. And I even know one guy who designed his living room to accept two full length (30 feet) straight horns, fed by a pair of Macintosh (not Apple) 5 watt tube power amps. It was *LOUD*!!!<br><br><br>-Mike Curtis<br>

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