4 Subwoofer Home Theater Setup
|
New member Username: CounterbondPost Number: 9 Registered: May-06 | SO i been thinkin about seting up some more subs with my home theater, cuz i'm tired of the little 6 ohm sub always clipping, and from my experience i have always heard a sound difference between 1 sub and 2 subs or maybe 1 sub and 4 subs. SO do you think this would work off my home theater setup, if i get 3 more of the same sub that i have and set it up like this? |
|
Bronze Member Username: SerniterPiscataway, New Jersey USA Post Number: 72 Registered: Mar-06 | Seems to me you'll maintain the resistance, but also require four times as much current. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9217 Registered: May-04 | . If you intend to connect each channel to two six Ohm systems in parallel, you will not maintain the impedance. You will drop to three Ohms nominal - on each channel. That doesn't allow for any of the inevitable dips in the actual system impedance. I doubt your amplifier will be very happy with this arrangement. . |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9218 Registered: May-04 | . What exactly are you intending to do? It's not clear from your diagram. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9219 Registered: May-04 | . Are you using powered subs or passive boxes? If passive, why not just buy one (or two) powered subs to handle the low frequencies? |
|
New member Username: CounterbondPost Number: 10 Registered: May-06 | That diagram up there contains, two 6 ohm subs in parallel which with my math will equal a 3 ohm impedence. If you have two of those setups in series, it will still maintain a perfect 6 ohm impedence, which is the impedence of the single sub that is hooked up to my surround sound. And i dont think that it will require 4 times as much current, i think it will just drop the original current down to four subs. 1/4 of the current per sub. equals... Less clipping, less distortion, because it is divided amongst four subs, AND I can place 1 in my right corner, 1 in my left corner, and 1 on each side of the tv. What do you guys think? Again, I have a Sub output on my hometheater that is rated to one single 6 ohm sub, in a passive box. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9222 Registered: May-04 | . I don't think you understand "clipping". There will be no more power produced (which is what determines where the amplifier clips) but what is there will be divided between the four drivers. So each driver is going to get approximately 1/4 the wattage of a single driver while the amplifier still clips at the same point. You might gain some by way of acoustic output, but not change the point where the amp will clip. This seems like an expensive way to get better or more bass response and is certainly an inefficient way to stop the amp from clipping. You will want the subs to be balanced with the main speakers, so I don't see that you are going to gain anything in terms of real value. . |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9223 Registered: May-04 | . I would scrap the idea and buy a powered sub. Run this off the main speaker outputs and you will probably have better performance. What kind of amplifier is this? |
|
Gold Member Username: NuckPost Number: 4344 Registered: Dec-04 | I think you should re-think parallel resistance. Parallel resistane is one over/oneover R1+R2+R3 etc. Parallel resistance does not preclude inductance, the logarythms I cannot fit here. Yes, I have been boning up on math. |
|
Gold Member Username: Touche6784USA Post Number: 1125 Registered: Nov-04 | uh i think brandon has it right. i dont know what you guys have been smoking. but jan is correct on that brandon has no idea what clipping is. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9226 Registered: May-04 | . http://www.bcae1.com/spkrmlti.htm I'm going to guess Brandon also has little knowledge of "damping factor". It will get screwed to hell with the connection he suggests, not to mention the problem of low impedance dips that I mentioned above. Yo! Brandon! Drivers do not stay at one impedance. They rise and dip and you are at the limits for most amplifiers when you suggest the type of connection you want to make. You are treading very close to imploding your amp. With the lack of proper damping to each driver, you will more than likely have four drivers flopping in the air rather than better bass response. You better have lots of amperage in this amplifier otherwise the drivers will begin "driving" your amplifier's output stages. As Nuck suggests, the combined inductance of all these voice coils isn't going to make your amplifier very happy, particularly if you're looking at playing at high volume levels. Brandon also might want to draw the connection properly before making the connection, if he insists on making a series/parallel system. Looking at the diagram, I still have no idea what he intends to do - but it doesn't look good for any amplifier that has to deal with that connection. What are the marks that appear to be resistors? Where are the + and - connections on each driver? The diagram shows a connection that would solve Brabdon's problem. A dead short! He wouldn't have to worry about only having one sub output. The new stereo he buys to replace this one would have the proper connections. Something tells me this is a HTIB. Something else tells me Brandon is coming from car stereo to home audio. . |
|
Bronze Member Username: CounterbondPost Number: 11 Registered: May-06 | HAHA...yea well i'm more of an all around audiophile. But i'm actually half way to getting my electronics degree. I didnt mean to confuse you guys as far as my diagram. It's a schematic drawing i drew up, and i guess maybe i should have drawn coils instead of resistors. I just see speakers as a resistance cuz of it having an ohm rating. And yea, i'm learning that the impedence changes with different frequencies and stuff. But I dunno, I'm still unsure as what would exactly happen. I dont think it would do anything to my amplifer at all, because as far as the amplifier is concerned, it still sees a 6 ohm impedence across that sub output. I'm definately going to ask my teachers this week about it, and see what they have to say. If anyone else has any ideas on what would happen, post it, otherwise i'll post what my teacher says. btw you guys crack me up. Yes it is a htib, and a piece at that, i just thought it would be effin sweet to have 4 subs. I use to have 2 kenwood tornados in my room, with a 50 watt car amp hooked up to em, runnin off like 4 12V Computer PSU's. And then i realized i can just build my own damn psu, with a bigger transformer, instead of combining a ton of powersupplies, for VERY uneffecient power. ALSO... Jan....What are you talking about a dead short for? there is definately no dead short anywhere in that diagram? Brandon |
|
Bronze Member Username: CounterbondPost Number: 12 Registered: May-06 | P.S. Resistance gets added like this Parallel resistance = 1/(1/R1) + (1/R2) + (1/R3) AND Whenever you have any 2 of the same resistance in parallel, its always gonna be half of the original resistor. AKA 2-2 ohm resistors in parallel = 1 ohm 2-4 ohm resistors in parallel = 2 ohm so on and so forth. As much as i hate going to school, i learned a little somethin.... ITS GETTIN tough though... BV |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9228 Registered: May-04 | . Brandon, keep on going to school. Speakers are not a resistive load, they are a reactive load. Impedance and resistance just happen to share a common name out of convenience. Your biggest mistake is thinking of drivers as a purely resistive load and the amplifier as a source of "watts". One thing that should be clear to anyone coming from car stereo to home audio is that things don't work the same in both fields. Cheap class D isn't going to operate the same components as better built class AB. And you don't have a 60+ amp battery to use as a current sink. If your HTIB is a chip amp, you might swing the subwoofer connection for a short while. Eventually the current draw will be high enough to fry the chip. The amplifier is limited in voltage swing and you are going to have something that a car audio guy might admire, but I doubt you will have good sound. You are still going to "clip" the amp. Instead of thinking of drivers as resistors, try thinking of them as inductors. Look at an inductor and then look at the voice coil of a driver. Notice any similarities? Without any + or _ marks, you have shorted out the connection. I suspect you know what you intended, but anything else is not clear to me. Read the link I provided concerning parallel/series connections. It will explain how your set up will work in terms of resistance. The article, however, still talks about speakers as nothing more than resistive loads. This will get you in trouble with a cheap amplifier. . |
|
Gold Member Username: PetergalbraithRimouski, Quebec Canada Post Number: 1943 Registered: Feb-04 | I'm with Chris here. Brandon's diagram has no short and is correct. The remark keep on going to school is very condescending, but worse considering that the simple diagram is correct. The "+' and "-" connections are there at the bottom of the diagram, perefctly showing how to connect four speakers together to appear as a single speaker. If the four 'speakers' are identical, then the fact that impredence varies with frequency doesn't matter and the same load will be apparent to the amplifier. It won't give the amplifier any more power, but if by "clipping" the OP meant to say "bottoming out" then his post makes sense. |
|
Bronze Member Username: CounterbondPost Number: 13 Registered: May-06 | The clipping will still occur, but the total amperage output will get distributed amongst the four subs evenly. 1/4 of the total amperage per sub. I'll let you guys know how much of a difference this makes. As long as the amp still sees a 6 ohm load, it could careless how many subs there are. Whether or not i notice a huge difference with having 1/4 of the amperage dispersed amongst four subs i dont know yet, hopefully i will though. Brandon |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9232 Registered: May-04 | . The + and - at the bottom of the page only indicate the outputs of the amplifier. You might understand what he intends to do, but I would hand that diagram back to anyone who told me to make "that" conenction. You are both still looking at the situation as a purely resistive load. And that is where you will get into trouble with a HTIB amp driving this system. Since no one has any idea what drivers Brandon will use - are they all going to be identical? - there is no way to safely state that the conenction will be OK. If all the drivers dip down to three Ohms, do you think that having multiple drivers dip down to three Ohms will be safe? If you don't care to look at the voice coils as inductors try envisioning them as motors, since that's what they are. At least think of them as reactive loads and not just as resistors. And I don't think telling anyone to keep going to school is condescending. I never doubted that Brandon would make this connection no matter what we suggested. Since he is bound and determined to try this, let me make this suggestion. Raise the impedance by connecting two of each driver in series and then make the connection between the two sets in parallel. This should bring the overall impedance up a bit, while maintaining what on paper would appear to be six Ohms, and not stress the amplifier as much. Or better yet, make three series connections and one parallel at the end. This would raise the impedance enough that no matter what the impedance dips were, there would never be a situation where the amp was (probaby)in danger of drawing too much current. Neither of these connections take into account the problems of constantly hanging more drivers off one amplifier. Please read the "warning" section of the page I referenced. . |
|
Gold Member Username: Touche6784USA Post Number: 1126 Registered: Nov-04 | jan, you disappoint me. he clearly states he will be using 3 more of the same driver. i dont know how he is going to get 3 more but that is his proposition. regardless of what kind of load the amp will have all 4 subs will have the same if not very similar reaction. if all 4 subs drop to 4 ohms, the overall load will still be 4 ohms with the specified wiring. i am starting to doubt if your brain is all there still. |
|
Gold Member Username: PetergalbraithRimouski, Quebec Canada Post Number: 1944 Registered: Feb-04 | The + and - at the bottom of the page only indicate the outputs of the amplifier. They represent the + and - connection of the combined "speaker". You connect them to the + and - of the amplifier. You might understand what he intends to do, but I would hand that diagram back to anyone who told me to make "that" conenction. Ok... You might not understand it, but that doesn't mean that it's not correct. You are both still looking at the situation as a purely resistive load. You are making it more complicated than it needs to be. And I don't think telling anyone to keep going to school is condescending. No, I guess you wouldn't. The OP might suggest that you go back to school to understand his diagram then. Since he is bound and determined to try this, let me make this suggestion. Raise the impedance by connecting two of each driver in series and then make the connection between the two sets in parallel. His diagram connects two sets in series, each made up of two speakers in parallel. This is electrically identical to two sets in parallel, made up of two speakers in series. This should bring the overall impedance up a bit, while maintaining what on paper would appear to be six Ohms, and not stress the amplifier as much. Huh? |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9233 Registered: May-04 | . I know where you connect speaker cables, Peter. Dont be condescending. Do you see any + or - indications other than at the amplifier outputs? Brandon did not explain his intentions until he was asked to do so. There is no way from that diagram to understand how the speaker are to be connected. Series connection is always the sum of the two loads. A parallel connection does not always result in half the two loads. The differences might be slight, but any amp is going to be more stable with a series connection than a parallel connection, particularly if this is a bridged amplifier driving the low frequency ouptut. Which it probably is. Electrically, when in use, the two connections are not "identical" when the speakers fight back. All of this still only amounts to the on paper numbers that look at the system as a purely resistive load. What about this difference between resistive and reactive load are you not understanding? You are asking the same amount of voltage and current to do four times the work. What would you expect would happen if you connected four electric motors to the same limited voltage/current supply? Did you read the "warning" segment? The word "warning" is there for a reason. You are going to place a reactive strain on the amplifier's power supply that will eventually cause it to crash since Brandon has stated he wants volume. This is a HTIB for God's sake. How much of a power supply do you think it has? He is not solving any clipping issues. He is daydreaming about something that will sound like the purple Mitsubishi Eclipse that cruises my neighborhood. This is not the way to good sound. Why not encourage good solutions rather than bickering about who is right here? I don't know how he will get three more of the same driver either. That is my point. For the expense of three more drivers, I still suggest scrapping this entire idea and buying powered subwoofers that will not represent a strain to the HTIB amplifier. That makes more sense than arguing about this system. Brandon is determined to make the connection. I have voiced my concern. I don't believe there is anything else to add until he either manages the connection and cranks the volume or his instructor gives a better answer. . |
|
Bronze Member Username: SerniterPiscataway, New Jersey USA Post Number: 73 Registered: Mar-06 | The diagram is clear though not labeled. However, using Brandon's logic, I could get even more volume by adding eight passive drivers instead of four. How about some elementary calculations to determine current through each driver? |
|
Gold Member Username: Touche6784USA Post Number: 1127 Registered: Nov-04 | now you are just being obtuse jan |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9234 Registered: May-04 | . In what way? |
|
Bronze Member Username: CounterbondPost Number: 14 Registered: May-06 | I think i changed my mind about trying to find 3 more drivers. I'm just going to switch out the driver that came with the home theater, and maybe do two 12 ohm subs in parallel. Any Ideas? Now that i've started a world war 3 on how resistances are added, and how schematics are drawn. lol Brandon 12 ohm SUBS... 2 in parallel for a six ohm impedence... |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9235 Registered: May-04 | . You cannot get more volume by adding more drivers when the amount of "power" to do the work is fixed. You cannot continue to hang more speakers on an amplifier's outputs just because the resistive numbers on paper show the same value. Four motors will get approximately one fourth the current and voltage that would be delivered to one driver, although the power is not going to be distributed evenly across all four motors. The amplifier will have to work harder to get the same amount of power to each driver. If the voltage and current are limited, you will eventually run out of "power". . |
|
Bronze Member Username: CounterbondPost Number: 15 Registered: May-06 | Thats why i've changed my mind to distrubte the power of the amplifier evenly amongst 2 12 ohm subs instead, that way i'm not gonna have to worry about volume loss. PLUS they will both be in each of the front corners of my room. I think this should work pretty damn good if i can find some 12 ohm subs. |
|
Gold Member Username: NuckPost Number: 4353 Registered: Dec-04 | While series and parallel resistance formulae are nothing earth shattering, I think Jan was guiding the OP away from a futile experiment. Slagging Jan for taking this away from a simple electrical 101 and into application seems useless. Reading anything more into the OP's napkin science than 101 is useless, unless it is extracted into a real world scenario, in which case, a smoldering little amplifier is the result, in short order. |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9236 Registered: May-04 | . Brandon - I have stated repeatedly I am not an engineer nor an electronics technician. My background is in consumer and pro audio. My disagreement in how you've drawn your schematic is based on being the person who is responsible for making the system work. While the shorthand version of your idea might work fine to sketch the layout of a resistor network, when dealing with speakers, if you handed that sketch to me and said, "Go hook this up", I would hand it back for further claification. As I've stated here, speakers cannot be viewed simply as resistors. Speakers must be seen as AC motors (at least) where positive and negative flow of energy is important. Clearly marking how the system is to be wired would first add clarity to the drawing, secondly assure the desired impedance of the parallel/series network is achieved and finally make certain all the motors were operating in the same electrical phase. In the real world this would eliminate, or at least mitigate, more finger pointing and bickering over who is "right" than has gone on in this thread. Should something not work properly, whether it meant a simple rewiring job or the replacement of a blown amplifier, a correct shematic would be of great assistance in resolving the issues that would arise. I point this out because too many E.E.'s and architects have no idea what it is like to actually hook up the equipment they specify and the schematics they draw. Clarity should always be your goal when laying out a schematic. As to your twelve Ohm driver, I've not seen many in my experience. The problem is further compounded by requiring a twelve Ohm driver that suits the frequency range you need and can fit in a reasonably sized enclosure and still be an improvement over your current driver. If this is what you must have to satisfy your desires, however, you could make up such a unit by using two dual voice coil drivers. There are quite a few D.V.C. designs available in both four and eight Ohm versions. Connecting one each of the four and eight Ohm coils in series would give you your desired impedance. This should work fine assuming the output of your amplifier is a true mono output. (?) This should increase the number of available drivers by a significant amount over the single twelve Ohm design. Running the cables from a single output and then across the room would become a rat's nest of wires and would make the system difficult to troubleshoot, but you would have your desired impedance load. The simpler approach, and more sensible in my estimation, to a passive driver network is to merely increase the impedance of the system to eight Ohms. This would make more than enough drivers available for your needs and make the amplifier more stable in the process. (A more stable amplifier should alsways be the first consideration and preference when modifying a system.) The slight decrease in output from the amplifier into the slightly higher impedance could easily be offset by buying a slightly higher efficiency driver over your current unit. Assuming, that is, you know the sensitivity of your current driver. Which I assume you don't. And that, in my opinion, is the major failing of your planning. You are trying to modify a system you know virtually nothing about. That typically puts you at a severe disadvantage when trying to get better results. It's hard to go forward when you don't know at what point you are starting. I would still opt for the powered subwoofer over any of these passive designs. It elimiantes the initial "problem" of amplifier clipping and allows you the provision to increase output levels rather than being tied down to a passive system. It should also be a unit that can grow with the system as you improve the quality of your audio gear. With the jerry-rigged passive system, you will probably discard the system once you upgrade your system. All this, of course, is subject to your decision making process. . |
|
Bronze Member Username: CounterbondPost Number: 16 Registered: May-06 | One of my work buddies at work who has worked on speakers for almost 30 years or so, (also he is a electronics technician) says that it will in no way draw more current from the amplifier as long as the impediance is matched. I also had an instructor say that the current will get divided amongst the woofers. For fear that i will lose volume, i want to do just a 2 sub setup instead. two 12 ohms in parallel to the output of the amp for a 6 ohm load. OTHERWISE how the hell do you take a line out to a speaker and turn it back into a low level signal that can be recognized by a powered subwoofer? |
|
Gold Member Username: Jan_b_vigneDallas, TX Post Number: 9239 Registered: May-04 | . By buying a powered subwoofer with speaker out/in provisions to step up the impedance and step down the voltage of the speaker output to match a line level input to the built in amplifier. Almost any well designed powered subwoofer allows for this type of hookup. If your system has any line out provisions that track the volume control, you can use that as a line output to the powered sub. I don't think anyone ever suggested the parallel/series system would draw more current as long as the resistance remained the same. That, however, is not the problem you face when you begin adding more drivers to the outputs of an amplifier. The drivers are reactive (read the definition of impedance) and each adds to the load the amplifier sees, each voice coil acts as an inductor and screws with the phase angle of the load making it increasingly difficult to drive each speaker which will require more current (that the amplifier dcan't produce) as the phase angle increases and particularly so when you ask the system to work at high volumes where the v.c. will heat up and further change the inductance of the system. This phase alteration will be what draws more current and this is the difference between seeing the speakers as a resistive or reactive load. Each voice coil acts as a motor and you are speading the available and limited amount of current and voltage your amplifier's power supply can produce among four motors. To get each motor to do the same work, the amplifier will have to work harder. (Read the "warnings" section of my link.) Each motor has the ability to put current back into the amplifier as negative feedback. When you add more curent coming into the amplfier, you lower the damping factor, see my earlier post. By lowering the damping factor, you can eventually get to the point where the drivers are "driving" the amplfier through the NFB circuit. Additionally, the drivers in an enclosure will not be a solid six Ohms, they will have dips and peaks and the changes in the actual impedance of the system will be what makes the system more difficult to drive even though the on paper numbers all remain the same. If you were dealing with a massive power supply in a conservatively rated power amp, this would not be that much of a problem with just four drivers at six Ohms nominal. But with the pea sized p.s. of a HTIB, I don't think it's worth the effort to find out you haven't increased anything other than the expense of the extra woofers. And, I don't think a HTIB p.s. will survive the experiment. I could easily be wrong about all of this. Give it a try and find out. But with the lowered damping factor and the p.s. stretched to its limits as the volume goes up, I just don't think this is the route to good sound. Ask your work friend why distribution amplifiers don't just continue to hang speakers off the outputs of the amplifier. It works for a certain number of speakers and then the problems arise. That's why distribution transformers are used. . |
|
Silver Member Username: EramseySouth carolina United States Post Number: 497 Registered: Feb-05 | Been waiting to respond to this thread,but been busy as of late. Although your wiring diagram is correct Brandon, it is improperly labled with missing info. Jan is on the money here. First let's clear up some misconceptions. First and foremost as Jan said a speaker DOES NOT EXHIBIT A FIXED IMPEDENCE as this will vary(widely in some cases) with frequency. A speaker output signal is AC so you cannot use the reciprocal sum formula 1/1/x,accurately to find the impedence of an AC circuit as this formula is for DC circuits. To calculate impedence in an AC circuit, (Z), you must find the square root of R squared + Xl(inductive reactance squared. This is assuming you know the L in Henrys(H) of each drivers voice coil. An inductor, like Jan suggested has reactance but this is not true R as would be in a purely resistive circuit. Your instructor will confirm this. Speakers for the most part are assigned an equalivalent (DCR) value by the manufacturer which is only an approximation after inductive reactance(Xl) and capactive reactance (Xc) values for the speakers crossover and motor structure is considered. The next time you are at school take your MM or an Ohm meter and measure the resistance across a coil such as that in a motor starter, the reading in Ohms should be nearly zero. While your friend is correct in that the drivers cannot consume more current than is available for delivery,the problem arises when each individual driver wants all the available current for itself and doesn't want to share. Yes a volt is a volt be it AC or DC,but in terms of current AC and DC are radically different in nature. With a device such as a speaker selector, impedence can be maintained safely due to multiple resistor networks within the device. With the connection you pursue you will not have this safety margin. I've seen the insides of a few HTIB systems and the dimunitive power supplies are often no larger than that of a VCR! You describe an overall impedence of 3 Ohms but in all likelyhood this could dip as low as 1-1.5 Ohms! Just about any flagship HT receiver(massive PS) will balk at such a low impedence and many high wattage multichannel amplifiers will as well when faced with such a load. Although we have had our dissagreements,some heated but never really nasty,I'll side with Jan on this one as his suggestion to by a powered sub is the most practical route. By buying a powered sub with a decent sized driver at least 10" or larger with a high wattage capability amplifier with an RMS of at least 100W and a peak of several hundred Watts, this should give you a noticable headroom extension while keeping the amp in your HTIB safe and happy. BTW I am an electronics technician myself, my specialty is in industrial automation and robotics. I assume you have just started your program as you listed formulas for DC circuits, which you have to learn the basics first. Wait till you get into 3P AC and Semiconductor devices,then things become really challenging. Good luck! |
|
Bronze Member Username: Mortal_oneCanada Post Number: 49 Registered: Nov-04 | LET HIM BLOW UP HIS HTIB!!!!!!!!!!!!!! He will be happier afterwards anyways, and he might learn something along the way. If you want some cheap drivers to start with that are of good quality check out Apex Jr. http://www.apexjr.com/ these will last past your abuse of the HTIB and you can use them when you decide to start with some bigger projects. This way you can have some fun with it. Just my 2 bits. |
Main Forums
Today's Posts- Home Audio Forum
- A/V Receivers Forum
- Amps Forum
- Cassette Forum
- CD Players Forum
- CD Recorders Forum
- DAC & Transports Forum
- DVD-Audio & SACD Forum
- Equalizers Forum
- Integrated Amps Forum
- iPod Docks Forum
- MiniDisc Forum
- Mini Systems Forum
- Digital Music Systems Forum
- Phono Forum
- Preamps Forum
- Speakers Forum
- Subwoofers Forum
- Tuners Forum
- Home Video Forum
- Home Theater Forum
- Car Audio Forum
- Accessories Forum
- All Forum Topics