The Homewrecker

Step 10: Notes and Disclaimers

Notes:

This system is very heavy and will probably require two people to move it. I will probably mount handles on the front to make it easier to handle and create some kind of removable cover to protect the drivers while in transit or storage.

The room does not actually act as an enclosure for the woofers as much as it just keeps the front wave separated from the back wave, which is known as an infinite baffle arrangement. If there is some way for the rear wave to reach the front wave (e.g. mounting in the doorway of a room with multiple entrances), this system will not be very effective. The two waves will be 180 degrees out of phase and at least partially cancel each other.

This is effectively a 4 ohm system. Make sure the amplifier used is compatible with this impedance.


Disclaimers:

I have not yet fully tested the capabilities (or potential dangers) of this system. The heating and cold air return ducts in most rooms in a house should be enough to relieve the pressure induced by large woofer excursions. However, if there are no ducts in a room for some reason and there are windows, be aware of the effect of the pressure on the window(s).

Very low frequencies travel well and are not easily absorbed, so if you are using this system at full or nearly full capacity and have immediate neighbors, they will hear it and probably call the police. Use good judgement .

Comments

[amclaussen]

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 "Insertion Loss".-<br/><br/>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).<br/>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.<br/><br/>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.<br/><br/>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...<br/>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.<br/>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 "subwoofer-satellite system" 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" to 8" unit will be required per side (or a pair of good 5" 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).<br/>Finally, where do we get a good Active crossover? May I suggest to go to "Elliott Sound Products" 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...<br/>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!<br/>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 "sound" (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..)<br/>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: <a rel="nofollow" href="http://slumz.boxden.com/f359/worst-best-car-audio-brands-419293/">http://slumz.boxden.com/f359/worst-best-car-audio-brands-419293/</a><br/>Good Luck<br/>Alfredo Marquez Claussen, Mexico City. amarquez (aT) i m p dot m x<br/>

[Evan2010]

Just a couple thoughts?

[lloydrmc]

The Elliott Sound site is a good source for phase compensated active crossover circuit boards.

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).

One thing I don't see listed as a benefit of active crossovers is the decided decrease in intermodulation distortion.

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 "T Amps". They are wicked efficient.

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.

[howler2892]

WTF!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[ryandean98]

P.S. YOU LOST ME At JUST!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[darthpotato1]

P.P.S.

I LOST THE GAME!

[T_T_]

for those who don't know http://en.wikipedia.org/wiki/The_Game_%28mind_game%29

[T_T_]

I hate you now, you made me lose the game too:)

[schumi23]

you made me lose :(

[ryandean98]

These Are Supposed To Be Comments, Not F**king Novels!!!

[sparktech]

hahahaha too long didnt read

[ryandean98]

I Know What The Hell Do These People That Write These Do For a Living?

[DiscoJones]

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.

[lloydrmc]

Hear, hear! Well, maybe unless you go deaf listening to that monster.

[sparktech]

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??

[amarquez]

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 "esoteric" 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 "generic" design where no real data for the drivers was used at all (or using the "ideal" 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 "match" 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).
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 "a chimmey") 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 "Transmission Line" 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!
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 "a goldmine of electronics info" 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.

[schumi23]

Just a little advice: Aerate.
That comment is very, very, painfull to read.
Hitting the "enter" 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.

So, Aerate. Good advice when typing up anything, and especially a comment.

[schumi23]

Let me reiterate, i think im now the only person to have read it all.
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
Which makes it quite lesible. Also, makes me not waste 2 hours reading it :)

[ryandean98]

Holy S**t BIG WORDS!!!! Pneumonoultramicroscopicsilicavolvanoconiosis

[bloke2022]

O.0 big words. lol

[flio191]

yeah... tl;dr

[X Files]

Ya. I feel ashamed by only knowing the word pneumonoultramicroscopicsisicovolcanoconiosis

[Millawi Legend]

But do you know what dichlorodiphenyltrichloroethane is?

[toogers]

do you know what pneumonoultramicroscopicsilicavolvanoconiosis is?

[softairdude]

It's spelled Pneumonoultramicroscopicsilicovolcanoconiosis. Just FYI

[rhendric]

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.

[toogers]

nice, spot on. extra credit for the tidbit about being the longest word

[bloke2022]

it is an  insecticide used to control mosquito-borne malaria.

[amclaussen]

Pardon my ignorance...
What is the connection of the DDT to the Homewrecker???

[mpep]

Enough DDT will also wreck your home/marriage etc :)

[amclaussen]

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 "Insertion Loss".-

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).
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.

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.

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...
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.
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 "subwoofer-satellite system" 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" to 8" unit will be required per side (or a pair of good 5" 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).
Finally, where do we get a good Active crossover? May I suggest to go to "Elliott Sound Products" 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...
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!
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 "sound" (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..)
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: http://slumz.boxden.com/f359/worst-best-car-audio-brands-419293/
Good Luck
Alfredo Marquez Claussen, Mexico City. amarquez (aT) i m p dot m x

[lpoiy]

how do you power the subs if its a "homewrecker"?

[codongolev]

put them facing inward in a multi-entrance room and bam, you have a torture chamber.

[Gonazar]

Haha, very clever, turning a room into an enclosure (sorta). What effects would there be if you put multiple homewreckers in a multiple-entrance room, given that the other rooms are closed off?

[DiscoJones]

It would work like gangbusters, just make sure to watch the impedance and polarity.