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Discussion Starter · #1 ·
I have purchases 8 Aura Pro Bass Shakers (4 oms / 50 watts each max.) and will be running them off a 250 watt AP sub amp. i have a couple questions that I would appreciate your help with so I don't start anything on fire.


Will this amp be powerful enough to run all 8 shakers or should I go with less? I could probably get by with 6 in my theater. please advise.


Also, I understand how to wire two shakers in series or two in parallel but get confused when you combine the two, series and parallel, which is common when wiring shakers to a one output amp like a subwoofer amp. If I want to wire 8 shakers that are 4 ohms each into one sub amp output, and keeping it all at 4 ohms, what would it look like (if possible)? What would it look like if it were 6 shakers (if possible)? What causes the damage to the equipment, speaker ohms greater than what the amp is rated for? If you know how to do this, I would really appreciate your help. if you could email me a diagram or (fax it to me if that would be easier). I don't think I will be able to follow it if you just describe it. This is holding up my project and the wife is getting suspicious that I am doing something that she won't like so I need to get it done and everything cleaned up before she starts asking "how much". Thank you, thank you thank you for your help!
 

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Hi troy, You could search "google" under "speaker wiring, or speakers" I think 2, 4 ohm wired in series is doubled "8 ohms" and 2, 4ohm wired in parallel is half "2 ohms" I think. I could be wrong ? frankie d
 

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I will start with a worded description, which I think will explain more than you expect. Real speakers vary resistance with frequency, but if we assume identical loads, it doesn't change the basics. Let's start with a single resistance of 4 ohms, which could be a speaker, shaker, or plain resistor.


A given voltage (from, say, an amp that is not being overloaded or over-driven) will push a given current through a given resistance. This is the simple explanation of Ohm's Law: 1 volt will push 1 ampere through 1 ohm. If you either increase the voltage or decrease the resistance, the current increases, and vice versa.


Now, if we parallel two 4-ohm loads, the results would be 2 ohms; in series, the same two 4-ohm loads would present an 8-ohm load. If we take two separate parallel 4-ohm loads (2 ohms each pair), and connect the two pairs in series, we end up with a total of (2 ohms + 2 ohms) 4 ohms, the original single value. This is called parallel-series.


Even though we have 4 ohms again, the difference is that we have 4 times the driving force and the ability to handle (or need to provide, depending on your point of view) 4 times the power. If you have a single mono amplifier, this is the way to wire it; if stereo, use two groups of 4 loads.


Now, if you connect two 4-ohm loads in parallel, and then connect the two pairs in series, you also end up with 4-ohms; this is called series-parallel. The difference between this and the first grouping is the missing one wire connecting the mid-points between each pair; the advantage is that effects of slight differences in the drivers are minimized.


Specifically with your equipment: with 8 loads, no matter how you combine them, you will end up with either a total of 2 ohms or 8 ohms, because you'll have two sets of the above parallel-series (or series-parallel) groups. Just like two individual 4-ohm loads, you can either parallel or series the two groups of four.


If you had nine drivers, you could combine them in three series-connected sets of three in parallel, and end up with a 4-ohm total. Barring that, if you must have exactly a 4-ohm load, you will have to go to four shakers, but you should have some leeway here; lets look at the amplifier.


What does it specify for rated loads? Most amplifiers will specify a certain power into a certain impedance (basically AC resistance), such as 200w into 8 ohms @ X% distortion. Your's is rated @ 250 watt, but into what load? Does it have a 4-ohm rating, or even a 2-ohm rating? If so, just connect 4 shakers in parallel (1 ohm total), then connect a second group of four (again, 1 ohm), and then the two groups in series, which would be a total of 2 ohms.


If 2 ohms, is too low, how about about another option: three 4-ohm loads in parallel is 1.3 ohms, so two of those groups in series would equal 2.6 ohms. Still too low? That's the best we can do below 4 ohms, but you can do this: make three sets of two in parallel, then connect the three pairs in series, which will total 6 ohms (2 + 2 + 2).


Whew! I'm all typed out. Let us knowwhat the amplifier's specs are, and if we can be of any more help. I'll make drawings if needed, but you should be able to draw out what I described if you do it as you re-read what I said above. Good luck.
 

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Can the amp handle a 2 ohm load? If not, then you will probably need a second amp to wire them all up and have two 4 ohm loads. Wiring them all up to a mono amp will either give you a 2 ohm load or an 8 ohm load.
 

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Discussion Starter · #6 ·
This is the info from the amp.


Specifications: Measured power output: 150 watts RMS into 8 ohms @ .1% THD, 250 watts into 4 ohms @ 0.2% THD. Signal to noise ratio: 101dB (A-weighted). Bass boost (EQ): none. Amplifier Dimensions: 10-3/8" W x 10-7/16" H x 3-1/4" D. Enclosure cutout: 9" W x 9-1/4" H. Control Panel Dimensions: 5-1/2"W x 3-1/2" H x 3-3/4" D. Control Panel cutout: 4-1/2" W x 2-1/2" H. Voltage: Selectable, 115/230V, 50-60 Hz, 450W. Net weight: 12 lbs.


I kind of follow it and I really appreciate you taking the time to go into so much detail. I guess I would wire all 8 and they will be at 8 ohms rather than 4 ohms but will be at 150 watts instead of 250 watts. With this in mind could you detail how to wire the 8 shakers so I will end up at 8 ohms. I guess I see them wired in series in sets of two, then each group of four would be wired in parallel so I would have two groups of 4 shakers. Finally the negative coming off one group would run into the next group as the positive if that makes sense. It may be easier for me to follow if you drew me a picture so I know I am doing this right. You could fax it to me at (614) 876-2885 if that is acceptable to you. No cover needed. Thanks again for your patience.
 

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NOTE: I'm not an expert! I'm just another newbie who was able to figure out SOME basic wiring calculation for MY setup...


Assuming this is a MONO amp and ASSUMMING it can safely run BETWEEN 4 and 8 ohms. I MAY have a solution for you which totals 4.67 ohms using 8 speakers on a mono amp.


(Time permitting sketch may follow).


Wire 3 shakers in Series to get [4*4*4]/[4+4+4] = 5.33

Wire 3 MORE shakers in Series to get [4*4*4]/[4+4+4] = 5.33


Wire 1 single shaker to set of 3 in parallel. 4+5.33=9.33

Wire other single shaker to other set of 3 in parallel. 4+5.33=9.33


Wire those two sets of 4 in series. [9.33*9.33]/[9.33+9.33]=4.67 Ohms total for a Mono Amp that can handle 4 or 8 ohms.

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IS THIS SAFE to use this way?

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I'll try to post an image later

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Someone correct me if I'm wrong here!!!!!!! Or if this is not safe for the amp.
 

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Heres an 8 shaker wiring setup that is 4.67 Ohms (mono).
 

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Well, if the only goal is to present the amplifier with a specific impedance, then yes. However, in his diagram, each of the two shakers that are in series with the groups of three will receive just about all of the power; very little voltage will be dropped across the paralleled trios, and almost all across the single units.


Second, his calculations in his previous post: three 4-ohm loads in series gives you 12 ohms, not 5.3. Perhaps he should have said "Wire 3 shakers in Parallel to get (omitted) 1.33", place one in series with those three, and then he would have (1.33 + 4) 5.33 ohms. (For equal resistors, the formula is Ohms / No. of units.)


In my opinion, you should have equal power to each shaker, even if it neans six instead of eight. Otherwise, you'll end up with less power overall, instead of more. Either 6 or 8 ohms is still your best bet. In any case, parallel pairs, and connect each 2-ohm pair in series, + to -- . Three pairs = 6 ohms; 4 pairs = 8 ohms.


(Are you sure you can't get one more?)
 

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Quote:
Originally posted by Troy
Thanks for the drawing bob-vdi. Can anyone verify if bob-vdi is truly a genius with wiring shakers or not?
DON'T even think about wiring them that way!!!! One of the speakers is disapating 9 times the power of each of the other three.


Is this a one channel or two channel amp?
 

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Okay, looking at the specs, and the distortion doubling at 4 ohms, You're better off running more than 4 ohms; it'll run cooler and cleaner. I'd recommend using the method I last described:


Parallel pairs (+ to + and - to -), and then connect the pairs in series (+ to -), and you have to decide how many to use, six (6 ohms) or eight (8 ohms). I believe that the 8-ohm configuration will suffice; even though each gets only 1/8 of 150 (6.25) watts, that's a lot of shakers.


Again, the only other option is to use fewer shakers; you're asking a lot of a single amplifier.


If the amp were more powerful, or better at low impedances, I might suggest three in parallel (1.33 ohms), and then series the two trios (2.66 ohms). A ninth driver, in a third trio, placed in series with the other two, would bring you back to 4 ohms. Or, get a second amp, and use each to power four drivers (4 ohms each).
 

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Discussion Starter · #15 ·
Thanks Larry,


I will try all 8 on one amp and if that doesn't work I will try a second amp I guess. I hate to put too much money into this but I want to make sure it works too.


I looked up your web site and e-mailed you a copy of the diagram of what I think it should look like. I would scan and add it here but I don't know how to do it. Please let me know if it looks ok.
 

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Larry is right, you do want equal power to each shaker.


Just a simple correction on Larry's math. The 8 ohm configuration gives 1/8 of the 150 watt power which is 18.75 watts. This is about one third of there capacity but should still be a lot since the total for the room is still 150 watts.


Here is one more possibility. Instead of buying a 9th shaker (best solution) you could also buy a 50 watt 4 ohm resistor. These are commonly available as speaker dummy loads. Then wire as Larry described to get 4 ohms. Basically 3 shakers in series with one of the sets having the dummy load in place of the third shaker. Then put all 3 series sets in parallel. The power to each shaker is then 1/9 of 250 watts or about 27 watts. This gives you a bit more headroom and you won't hit the .2% distortion unless you are driving the amp all the way. In all honesty, I think it would be hard to detect even 1% distortion in a shaker.

..Doyle
 

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My bad; I was tired. 1/8 of 150 is 18.75 now, not what it was last night. I would avoid using a resistor in place of a 9th shaker, as it wastes power. If a particular seating position requires a little more wiggle-power that others, use two there, in parallel, and place that pair in series with two groups of three in parallel.


Meanwhile, I made a couple of drwaings by hand. Trying to draw them with a program was a real pain! The first shows a couple of simple hookups and their names, and that the two ways of wiring parallel-series are electrically identical, and merely drawn differently.
http://fineelectricco.com/Shakers1.jpg http://fineelectricco.com/Shakers2.jpg

My suggestion for eight instead of shakers without the resistor would be to use the middle drawing in the second row, and simply omit one shaker; and I left out the "8 ohms" for the last drawing, which would be my pref for using all eight.


Again, while it would be possible to wire any number in series-parallel, I prefer parallel-series instead, because slight differences between shakers are minimized.
 

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Discussion Starter · #18 ·
Thank you for all your time. It really helps to see it drawn out. Earlier today I wired them as shown in this attachment but have not hooked up the amp yet. Will this work and give me 8 ohms at the amp?
 

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Yes, it will give you 8 ohms. What you drew could be called "series/parallel/series. You have pairs in series (8 ohms), which are then paralleled (4 ohms), and then those in series (8 ohms).


The only difference between that and my last drawing is that you omitted the upper-middle and lower-middle horizontal connecting wires, but the overall impedance is the same. You done good. :)
 

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Discussion Starter · #20 ·
I am gonna try it this weekend. I received the amp today. My only fear is the amp, 150 watts at 8 ohms, isn't gonna be enough juice for 8 but I guess I could always get a second amp and do 4 and 4. Hope all this trouble is worth it. I am obviously in over my head on wiring multiple speakers/shakers but it sure is fun to have something different. I had 4 of the shakers wired, 2 per channel in series, on a cheap 5.1 receiver I am returning because I couldn't get all five channels to work at the same time with my inputted signal (not sure why-would have made it a lot easier to wire 8 shakers to 4 outputs and done the shakers in series of two per channel). My family loved it, mostly for game playing on the xbox. I gotta admit it was awesome. We had a lot of teenagers through here that week and the shakers made it worth the extra cost and work for that reason alone. thanks for reviewing my plan and all your advice. I will let you know how it goes.
 
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