Is doubling speakers +3dB or +6dB? What's parallel and series wiring? 

This is the kind of audio content we need on RU-vid. Very informative.

Eskimos have been hooking their woofers up in series parallel configurations for hundreds of years.

Great video was taught this on a Rockford Fosgate amplifier and system design course 30yrs ago, first time seen such good explination of it :)

Very good video! Reiterating old knowledge and this was perfect, thank you.

Easily one of the best video’s regarding this subject I’ce ever seen, keep the good stuff coming 👌🏼

Nice explanation of parallel vs series wiring with visual examples! I think anyone studying electronics or amateur radio should check out this video. Nicely done!

The Best info I've taken in since trying to understand thanks

Incredible clear explanation, thanks buddy !

What determines whether two signals of equal amplitude combine to produce a 6dB gain or a 3dB gain in signal level (voltage or SPL, but not power), is the “correlation” of the signals at the point of combining. FULL CORRELATION CASE: If the correlation is 100% between the two source signals at the location where the combined signal is being measured (the two source signals are received with identical amplitude and with identical phase) then a 6dB gain in level (SPL or voltage, but not power) is achieved. Example 1: Two side by side subwoofers which are both fed the same signal (with the same amplitude and same phase) and which are both equal distant from the measuring device. In this case, the measurement device will measure a “combined” signal which is 6dB higher in SPL than that measure by either subwoofer alone. For a sine wave signal source, the two source signals would always have their sine wave peaks “synchronized” and always providing a doubling of peak level. And we know that a doubling of level (voltage or SPL) results in a level gain of 6dB. However, it is important to note that the “power” delivered to the room is only 3 dB higher than that delivered by either subwoofer alone (a doubling of power results in a gain of 3 dB). NO CORRELATION CASE: If there is no correlation between two non-identical, but equal amplitude, signals at the location where the combined signal is being measure, then a 3dB gain in level (SPL or voltage) is achieved. Example 2: Two side by side subwoofers are fed pink noise signals generated from two different noise generators (the pink noise signals are not correlated). In this case, the measurement device will measure a “combined” signal which is 3dB higher in SPL than that measure by either subwoofer alone. The two signal’s peaks and valleys will only be in alignment part of the time. And over time, the signal alignment of the peaks will vary between in phase (0 degrees) and out of phase (180 degrees). And the average increase in SPL or Voltage signal level achieved will be 3db higher than that delivered by either subwoofer alone. MAINTAINING 100% CORRELATION ISNT ALWAYS EASY Even in example 1 above, if the SPL meter where to move around the room, the path length from each subwoofer to the measurement device would change differently for each subwoofer, and the correlation between the two signals being combined would not stay at 100%. The axis of the room where the measurement device is equidistant from the two subwoofer will always receive the 6db gain in SPL. But there will be some locations in the room where the path length from each subwoofer would result in a 180 degree phase shift at the measurement device, and the signal would be cancelled. But most people, who are not equidistant from both subwoofers would experience a 3 dB gain in SPL. Another interesting example is the case where two signals of varying phase are combined. Example 3: Two side by side subwoofers are fed sine wave signals from two different signal generators (one at 60 Hz and one at 61 Hz). In this case, the measurement device will measure a “combined” signal which varies in SPL reading over each one second period. For one instant in each one second period, the measurement device will measure a “combined” signal which is 6dB higher in SPL than that measure by either subwoofer alone. But AVERAGED over the full second period, the measurement device will measure a “combined” signal which is 3dB higher in SPL than that measure by either subwoofer alone. In summary, achieving a 6DB gain in SPL with two subwoofers only occurs where the resulting phase difference between the two identical subwoofer signals at the measurement position is near zero degrees.

Thank you. I was curious about this.

So far, the best video I've watched in the 36hrs I've been trying to understand about speakers. I have these 5.1 speakers I found in our basement with it's player already disposed of that I want to use as a pc speaker, and I'm trying to learn how I can install them when there's just one front and one rear 3.5mm headphone/speaker jack, though it's got a sound card that supports up to 7.1, for the life of me, I have never been interested in electrical wirings until now. I don't how I can wire them all into one jack, or do I need to install another sound card with more ports, or buy some whatnot to connect them to. If they get more expensive than buying a pc speaker, they're going back to where they came from, useless. I'm going to follow you from now on and learn.

Sehr gute Erklärung. Danke!

Nice! This, along with many of your other lessons and demonstrations, should be mandatory study requirements for all "Audio People", especially live performance types!!! Most of them are clueless and believe myths of their predecessors, urban legends, hearsay and of course: "that's the way it is, everybody knows that!"

Awesome explanation.

Great video!

Actionable intelligence, I love it!

Nice Honda Clarity. Love mine

Depends if they're acoustically coupled (coherent). If so, pressure adds and you get 6dB. If not, power adds and you get 3dB.

Great video.

Extremely educational just came across your channel. Exactly what I was looking for all this type of information

very helpful, thank you very very much!

When you raise the amplifier by 6dB it makes output voltage doubled (20V to 40 V) , and current flow also doubled as manner (1A to 2A).calculating the (P) power it show 4 times increment as this: 20V x 1A =20W and 40V x2A= 80W. Clearly 80W means 4times like 20W. But when you attached additional speaker it only cost more current, but no voltage increases, resulting power = 20V x 2A = 40W. My question is, why the measurement mic showing 6dB same increment at both testings above, while the amplifier produce completely different power output as, 40w vs 80W.

Thank you for impedance response from nexo bandpass

It should also be noted there are some practical considerations that need to be taken into account when doing things like this. When you let an amp drive a one or two ohm load, you're beating the crap out of it. Playing music through a system isn't the same as taking measurements on a test bench. Also, you have to consider distortion. The harder an amp works, the more it distorts. Its unavoidable, and the amount of distortion an amp produces is directly related to how well its made. 2 power amps may be rated for the same amount of output in watts/ohms, but one may have half the distortion, and in the real world, that would make it a much more powerful amplifier. I see in a lot of the comments, people seem to think they will be "loosing power" if they don't lower a speakers resistance so the amp puts out its rated full power at one or two ohms. Lowering resistance forces the amp into a situation where it has to work harder to deliver the same amount of performance than a speaker that is less demanding to drive, like one that drops no further than 5 or 6 ohms. The practical solution in a situation like this is to turn the volume up. That's why its better to present the amp with a speaker that's easy to drive in the first place. It leaves you with the freedom turn the volume up without fear that you will damage your amp or speakers. Just to be clear, from what I could tell, everything covered in the video appears to be accurate. Nothing is wrong with the content. My concern is things were left out. Most likely there will be a future video covering the issues I raised above. So my advice would be to wait for future videos covering the rest of the topic before making any purchase decisions.

Great video as always! I like that you don't just do the calculations, you measure things. In physics measurements are king. If your theory disagrees with measurements the theory is wrong. But I have an issue with this. What if you put 10 speakers in series? Your amplifier would output tenth of the power but you'd still get the same audio power. How? Let's complicate things even more. Now you connect 10 sets of these to the same amplifier in parallel. Your amplifier outputs the same amount of power as it did when driving just one subwoofer. Same voltage and the same current. Same power. But the audio power just went up by 20 dB. Let's have another thought experiment. You have 100 speakers. You connect all of them in series. Your amplifier outputs 1% of the power it was outputting with just one speaker but the audio power remans the same. You just increased the efficiency of the whole system by 100 times.. What if you had a 1000 speakers? Would your efficiency be 1000 times better? At what point your system's efficiency would be more than 100%? At what point would the system be outputting more energy than it's getting?

Thanks for sharing BUT NOW what if you got 4 12inch speakers in one guitar cabinet and the are factory wired in Series/ Parallel...how does that read on amp output? Thanks again.

Thank you, sir Information. and Details.

At the 3:45 mark, I take exception to the idea that the second speaker adds 3db to the sould level. In a parellel arrangement, adding a second speaker doesn't change the voltage, current, or power going to the first speaker. Adding a second speaker doubles the amount of audio power produced (+3db). The load on the amplifier has doubled requiring twice as much current. Not only does this follow ohm's law, but also obeys the conservation of energy. To get a 6db gain, you'd have to also double the power consumed and produced by each speaker. But that didn't happen! The voltage and current are the same and therefore so is the power per speaker. The overall gain is only 3db. So, why did the test microphone measure a 6db gain?

very nice video ! thx

On a side note: that hum coming from sub has an interesting effect of "robotizing" voice when speeding up or slowing down video's playback speed.

Nice... Good job. 😮😮!

the important question is dB relative to what and measured where?

Great video. Do these rules apply to powered subs? I have the Yamaha DXS 18XLF powered subs. When I couple them together do I get +3 or +6 db gain?

What is going to hapen if we plug two pairs of 8ohm woofers but one pair is paraller and the other one in seriers to the first one? Will the resistance be the same as if we have just one woofer? And the output still be doubled? Or the output will cancel itself as well?

Is the sound at the end taken by microphone? My subs got much quieter with increased impedance in the test during the last minute of this video, but the commentary then said that the volume was consistent during the sweep

I am looking to run 6 Bass. Is using 3 amps in mono, and connecting the othe 3 to the speakers better than running 2 per amp?. Try to make it powerful and cost effective. 6 Bass amps would be to expensive at this point. I appreciate your channel. Thank you.

Good effort and thanks a lot for the Video. I would like to experiment like you did, but hardly find opportunities with gears. To whatever I have learnt: Doubling the Voltage or current should result in 6 dB not 3 dB. Correct the video @3:24. Doubling Power results in 3dB change. Please correct me if I am wrong.

Thats why we tune port to free air fs of a woofer to compoansate for the high resistance on the impedance curve to even it out?

So if i were to use 4x 8ohm 15" Woofers in Parallel, what would the Ohmage then be? And by adding any other speakers (8ohm) (but not woofers), does this have any (negative) impact

If you use powered subs to simplify the whole process, a lot more people will understand it. Basically doubling your speakers gives you +3db . If one sub max SPL is 135db, adding an extra sub would make it 138 db SPL Max, and to increase it another 3 DB you have to add two more subs, the four subs would produce 141db Max SPL and if you want to add another 3 db, you have to have eight subs to increase it to 144db SPL Max. Basically, you have to double the speakers for every 3 db increase you want in SPL.

It's quite interesting to see how using more speakers saves energy. Although I'd expect this to gradually taper off as you add more and more speakers, so maybe you'd only get 5 dB from 2 more subwoofers.

So if you use 2 8ohm drivers in you dubbel 18'' sub woofer. and you wanna use 2 cabinets on one side on the amplifier. then you need to wire the speakers in serie?

Is that a bandpass type enclosure? I notice 2 nulls in the impedance curve.

Don't forget with multiple drivers in a cabinet you can wire series/parallel meaning if all drivers are the same impedance then total impedance at socket is as one driver. All 8 ohms then total 8 ohms .my vintage Bose 802s are all in series with a 0.9 impedance per driver do you get anything from 7to 8 ohms

Solid state amplifiers are rated at different speaker impedances. So my bass amp puts out 500 watts at 4 ohms, but only 350 watts at 8 ohms. I can use two 8 ohm speakers in parallel to achieve 4 ohms, or if there was 2 ohm speakers, two of those in series. It’s not the series or parallel connection that matters, it’s the total speaker load on the amp.

How do you have the meter leads on? I tried using a normal meter to test for voltage coming out of my car subwoofer amp, which obviously takes in 12-14v and i get weird numbers

If i have 2 speaker 800w to 4 ohms if in series connection what is the watts of the speaker thank you

So what you were saying ( in a very roundabout sort of way ....) was by hooking up two 16ohm drivers in series makes no difference.... only half the output power gets delivered but I assume the decrease in radiation resistance makes up for this .... am I right ?

I've seen all the internet about this issue and this is the best explanation of all. I'm really impressed! But 3:44 you say that one more sub gives you +6db. Are you sure? I thought it would give you another 3db, not 6, so together they would make +6db and not +9db. Do I get it right?

What it is two separated active sub ? +3db ? I dont understand when you say +3dB acoustic power. Because the power produced by the added membrane, is the exact additional power transmitted by the amp. So why do you count it twice ? (+6dB)

But what if amp would work in lower than 2 ohms. Why I can't connect 10 subs in parralel, because amp will rip ?

Devin, any idea why Nexo uses 16 Ohms drivers in their S-118 subs?

If they’re wired in parallel it will go up 3db. If they were in the same cabinet, and the cabinet was the proper size it would go up 6db. If those speakers are wired in series you’ll drop 3db. Ohms is a measurement of amperage, while volts is a measurement of Electromotive Force. But who cares?without getting crazy you can think of these two measurements this way. If you have a garden hose with water flowing through it, the volume if water coming out is its Amperage. The pressure of the water coming out is akin to voltage.

@devinlsheets_alphasound - I'm super curious about running things in series. Theoretically, if I had multiple four 4-ohm subs with a 1000w rms rating and a 135dB half-space spl, and wanted to run two of them in series per channel so I could get away with fewer/cheaper amplifiers, how would I calculate the wattage rating to properly drive them? Can I double the recommended wattage like with a parallel configuration to see a +3dB increase in SPL over one cabinet for a pair in series? Is it a lost cause because of the inherent electrical and mechanical cancellations? If i do get amplification in a series deployment, would I see +6dB if I doubled that same configuration? Are there phase/output issues or other substantive issues that I'm failing to consider?

You have to consider the Amplifier's impedance output as well. Let me use 8 Ohm speakers because many amps have 2, 4, 8, or 16 Ohm outputs. All Voltage, Current and Watts are RMS in my discusssion. 4 Ohm Output: Two 8 Ohm speakers in parallel = 4 Ohms (impedance match), at 40 Watts: In this case the Amplifier will supply 40 Watts. 12.649 Volts out with each speaker drawing 1.582 Amps each = 20 Watts from each speaker for 40 Watts total. 4 Ohm Output: Two 8 Ohm speakers in series = 16 Ohms (impedance mismatch), at 40 Watts: In this case the Amplifier COULD supply 40 Watts but it can't. 12.649 Volts out but only 6.325 Volts get to each speaker drawing 0.791 Amps each = 5 Watts from each speaker for 10 Watts total. Since -3dB is roughly a 50% Power Loss, 40 Watts to 20 Watts is -3dB, and 20 Watts to 10 Watts is another -3dB for a total of -6dB (1/4 the Power). So even if the Amplifier COULD try to put out 40 Watts with two 8 Ohms speakers in series on a 4 Ohm output, it can't do that due to the impedance missmatch. This is why Amplifers usually have several impedance outputs. Since two 8 Ohms speakers in series is 16 Ohms, you should switch to the 16 Ohms Output (if the Amplifier has one): 16 Ohm Output: Two 8 Ohm speakers in series = 16 Ohms (impedance match), at 40 Watts: In this case the Amplifer will supply 40 Watts but now using a different voltage. 24.298 Volts out but only 12.649 Volts get to each speaker drawing 1.582 Amps each = 20 Watts from each speaker for 40 Watts total. So If you change the Speaker arrangement and not select the proper amp Output Impedance, you will get less power out of the Amplifier or you may overload the Amplifier and cause damage. So ALWAYS match the Amplifier's Output Impedance to the Overall Speaker Cabinet Impdeance. Examples: One 12 Inch Speaker at 100W at 8 Ohms = Cabinet 8 Ohms 100 Watts RMS (commonly used) Two 12 Inch Speakers at 100W at 8 Ohms in Series = Cabinet 16 Ohms 200 Watts RMS (less commonly used) Two 12 Inch Speakers at 100W at 8 Ohms in parallel = Cabinet 4 Ohms 200 Watts RMS (commonly used) Four 12 Inch Speakers at 100W at 8 Ohms in Series = Cabinet 32 Ohms 400 Watts RMS (Outputs for 32 Ohms are rare, not commonly used) Four 12 Inch Speakers at 100W at 8 Ohms in parallel = Cabinet 2 Ohms 400 Watts RMS (less commonly used) Four 12 Inch Speakers at 100W at 8 Ohms in Series/parallel = Cabinet 8 Ohms 400 Watts RMS (commonly used) Series/Parallel Arrangement of four 8 Ohm Speakers 100 Watts each arranged for 8 Ohms 400 Watts total: | ------- | | 8 Ohm 8 Ohm | | ------- | | 8 Ohm 8 Ohm | | ------- | So why are there 2, 4, 8, or 16 Ohm speakers? The lower the Impedance (ohms) of the speaker, a lower Voltage is required to drive it BUT LESS AMPS (current) is needed as well. Since current (Amps) is key is power distribution (think of High Voltage power lines), a 2 Ohm Speaker (or Cabinet) requires less current though the wires to get the power from the Amplifer to the Speakers. At home or small venues, 8 Ohms is fine, but in a large arena where the Speakers are up high and many feet away from the Amplifiers, 2 Ohm Speakers and Cabinets are better. Series/Parallel Arrangement of four 2 Ohm Speakers 100 Watts each arranged for 2 Ohms 400 Watts total: This Speaker Cabinet requres less current to drive the speakers and thus less current/resistance (IR) losses though the cables. Also, lower current cables can be of a thinner gauge which saves weight and cost. | ------- | | 2 Ohm 2 Ohm | | ------- | | 2 Ohm 2 Ohm | | ------- |

I am about to go from 1 18" Resilient Sounds platinum to 2 18" in my truck. I will also be going from one Down4Sound JP23v2 to 2, or one per sub wired at 1 ohms for a total of 5600 watts I hope to get 6 dbs or slightly more, because of acoustic coupling because the 2 subs will be right next to each other, literally 1 inch apart.

missing the parallel and serial connection mixed

Now do a comparison between listed max SPL output compared to real world output.

What about car audio where DVC subs come into play?

so, parallel divided curent, series divided voltage. parallel increase SPL uses more power, series do not increase SPL but saves power 🤔 once again. great content, 👏👏👏👏 you guys should have 1M of views not like others that all they do is play their favorite songs but have 1Ms of views... people are so pathetic. 🤦‍♂️

Watching here sir

I still don't get it. Doubling the power on one subwoofer results in a 3dB gain. But the same power split on two speakers suddenly should gain an additional 3dB so 6dB total? How can 3dB magically appear out of nowhere? Where is this "acoustic energy" supposed to come from?

People are confused when they start to calculate because they use a single(!) driver as a starting point, and so cannot understand from where +6dB go. When we take a connection in series, and compare to a connection in parallel, then everything will match

I suddenly Have a problem connecting front door speakers 2 a second channel makes really bad audio( IV had the sound system in the car for 4 years I was told it was either a bad rca cable or the input of the RCA was damaged, I used another amplifier and changed the RCA cable but I still have the bad audio I ended up connecting all four speakers to one channel parallel and now the audio is ok out of all 4 speakers in total the 4 speakers add up to 24 ohm speakers watts add up to just under 1900 watts and the amplifier is 3000 watts I'm wondering if this is safe until I can finally get the problem fixed by a professional the gain on the amplifier is not max it's around half maybe less not sure since it's just a cross that I twist left or right

Parallel cost more speaker wire than series connection, basically parallel is way better than series is that right Sir?

Here's something I always wanted to know:- You build two subwoofer boxes with two 18 inch 8 ohm speakers each. You wire both speakers in both boxes in series. That would mean both boxes would be playing at 16 ohms. If you were to then 'daisy chain' both boxes together at the speakon connectors, would they then both be playing at 8 ohms or at 16 ohms?

In the video 1 amp drives 1 speaker 1A 20v 16 ohm, so 20 watts. Does that mean when connecting 8 speakers in series with acoustic coupling the amp only draws 2.5 watts while having similar acoustical output as 1 speaker? 😮 Because 1 speaker: 20V 1A 16ohm = 20 watts. 2 speakers: 20V 0.5A 32 ohm= 10 watts, 4 speakers: 20V 0.25A 64ohm = 5 watts, 8 speakers: 20V 0.125A 128ohm = 2.5 watts. I know 128ohm could be high for an amp, but this is about understanding the theory. Using 4 ohm drivers would result in 32 ohm load in the same 8 speaker set up. Or to get deeper into it: 2 speakers in parallel would result increase +6db. Meaning having a big array of 32 speakers in parallel would increase the acoustical output by a massive +30db! I am thinking of building a compact line array system with a 3 inch driver delivering 104dB > so max SPL of a 32 speaker line-array system would deliver 134dB am I right?

Is it true that if you have 2 speakers and one speaker can handle more power than the other, the that speaker will take the extra power? So if you had a 10 watt speaker and a hundred watt speaker and a 100 watt amplifier you wouldnt blow the 10 watt speaker cause the 100 watt speaker would take the extra power.

If you run a series parallel circiit you could hook up 100 speakers to the same amp and have the same ohm load as just one of the speakers.

does lower impedance produce lower frequency sounds?

ohhhhhh 6 db+ so is this why they say is better to double the speakers instead of the power first??? more cone area vs more power?

Error is on 5:36.The power when connected in series is 10 watts

There is no such thing as "3 dB more from the speaker". The amount of available power is what voltage*current shows - period. What you are demonstrating with "3 dB more from the speaker", is actually a coherent speaker array. Try moving your meas mic up and down and you see that the +6 dB isn't consistent. Also if you switch the polarity of the second speaker, when in parallel configuration, you see that the measurement from the front drops dramatically, as the phase fronts from two speakers are cancelling each other.

shouldnt the series connection be 20v at 0,5amp = 10watts? so 5watts for speaker (10v at 0,5amps)? you said 20watts, 10w each speaker

But with the same impedance in the amplifier both series and parallel has the same +3dB effect. Example__ Think an amplifier that is capable of delivering 64W at 4ohms. So that we drive 2 speakers with 2 ohm each by series way, so that each speaker will get 32W. We have two such speakers, therefore we get +3dB as doubling the power adds 3dB to the loudness. And by that same amplifier, we are running two 8ohm speaker in parallel mode. Then the impedance will be the same 4ohm. Each speaker will get 32W. In this situation also we are getting +3dB due to the previous mentioned rule. Note: only lowering the impedance and getting doubled power by the amplifier only increases 6dB.

I see there is diminishing returns for every subwoofer after the the second (amp/sub). The SPL calculator has +6.0, +3.5, +2.5, 2.0 db and so on. I'm almost finished building two vented boxes each with a 24" subwoofer tuned for 23 hz (internal volume 11 excluding ports, bracing, driver). This is for an outdoor audio/concert setup. Reinforces the fact on how important the sensitivity and frequency response of a subwoofer or driver is. It can get incredibly expensive or consume a ton of electricity.

I don't get it. With a single speaker you get 20W of power. In the parallel case, you get 2 speakers outputting 20W each, giving a total of 40W. That's a 2x, or 3dB increase in power. I still don't understand where the extra 3dB comes from.

My driver impedance 2 ohm each in serialized by 3.5 swg

😍😍

Sorry but I have doubts : Series 16+16=32ohms : the amp produces same voltage and half the current, hence -3dB. Each speaker gets half the voltage (-3dB) and half the current (-3dB), therefore each speaker -6dB. Since there are 2 of them, the total acoustic output is -3dB (half the power). Parallel 16&16=8ohms : The amp produces same voltage but twice the current (+3dB). Each speaker gets same voltage (0dB) and same current as only one (0dB). Since there are 2 of them, the total acoustic output is +3dB (twice the power). Putting an infinite number of speakers in series will finally translate into 0 power, since the voltage at each speaker and the current will both tend to zero, or am I really really wrong ?

I just learn a new symbol, U = voltage. Goodbuy V.

Only coils in dvc subs should ever be wired in series. I would never, ever wire separate subs in series. Just asking for trouble.

Excellent video, thank you very much. I just think there is a mistake at ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Om_1IYsqPWg.html, since P=U*I, so 20 V * 0.5 A = 10 W, not 20 W.

Hard to beat series-parallel

I know I'm dumb on this issue, but please sum it up. Is it safe and better on the amp and speakers in each arrangement? Which would produce better sound? Does the phase change in series?

Soo parallel is louder than in series and that's why most car subs that can go down to lower Hz will with proper power amp, like a 1 ohm amp that will run to 1ohm sounds better or louder (proper box made to go lower hz) than one in series? OK I got it. Thanks... Hope this is right?

it is a long time i did theoretics but dbu dbv is not the same and that is without speaking about impedance

it looks like your power amplifier is not strong enough. the output is that small. maybe the result will be different if it is made 4 ohm maybe the output will increase again

This is another advantage to having amplified subwoofers. You can keep adding parallel service without worrying about resistance or output loss

I have a question, that answer I cannot find anywhere. I have a pair of 4 Ohm speakers and a pair of 8 ohm speakers. My integrated amp had a typical 8 jacks for connecting 4 speakers. The A is 4ohm-8ohm, and the B speaker slot is 8-16 and the A+B asks for all 8 ohms. Since I dont have 2 pairs of 8 ohm speakers, so can I somehow connect the 4 Ohm speakers at the same time with 8 ohm without damaging the 4 ohm speakers, as I understood that in case of connecting all 4 speakers they should be all 8 ohm?

It's really surprising how little people in the business actually know about loudspeakers, which is what the basically make a living off of. 43% getting the 6db answer correct is astonishingly low.

No sense at the end what is good Parallel or Series ??????????????????????

more confused coming out than going in... thank goodness my home AV unit has 2 'sub outs'.. I will just buy 2 of the same subs and have 1 wire for each sub going into the AV unit.

I had to press my headphones to hear -36hz

I'm not into SPL. Just good tone with best coverage for speaker, whether one or two or amount of ears listening. If a venue has capacity of 10,000 sets of ears and 10000 minds or 10000 bodies, how much power is needed in subpower for 1/2 of 10000 bodies in avenue that is designed for 10000 bodies. That seems more reasonable for life of any subwoofer. Using math to figure out impedance load is cool but in real world, a knowledgeable sound engineer needs to understand this in order to do a solid sounding show.

Without reading the comments. I say 2.5 db by doubling drivers. And 5db doubling the drivers and power.

I don't get with your +3dB amp and +3dB acoustic power adding together resulting in a 3dB gain. The added electrical power powers the added transducer, and the added transducer produces sound. The 3dB gain is converted into 3dB acoustic power. The acoustic energy is just the electrical energy being transformed into acoustic energy using the transducer. You've said that the transducer doubles the acoustic energy, and I don't agree, it just transforms it. The +6dB comes from the definition. If I have a sub firing, let's assume it produces a monopolar radiation, then this simple model spits out the pressure : P = μ0*Σ*ω^2*X_eff /4π with X_eff being the efficient displacement of the membrane, Σ the surface of the loudspeaker and μ0 the magnetic constant. Then by adding another sub it's the same formula, but replacing Σ by 2 * Σ. thus adding 20 * log(2) from the definition of SPL : SPL = 10 * log(acoustic power/ref_acoustic_power) = 20 * log(P/P_reference). And 20 * log(2) = 6.021 something. The discrepency between the +3dB POWER and the +6dB PRESSURE is that acoustic pressure is related to acoustic power by a square law. Please challenge me if I'm wrong, this has made me crazy over the last few days, I can't sleep lol.

I'm going to put this In laymen terms, let's say we have 3 4ohm subs ( I'm not going into parallel and series, u should know that) we take two subs and bring them up to 8ohm, now we have 8ohm and 4ohm load, we do 8×4=32 8+4=12 now we divide 12 into 32, which is 2 with a remainder 8, henceforth 2.8ohm load( jl says my triple stack is 2.7, but everyone does math different 😀) that's it ohms law in it's simplest form. Please next time, explain it to me like I'm 6 years old, I don't comprehend very well☺

Our ears are not linear. A tenfold increase in power is perceived as a doubling in loudness. Gotta define "twice as loud" before you ask a question like this.

You can do all the math you want. When it comes down to it, what sounds better to you. Just smashed 2 12s and he did all the math and everything perfect on paper. Im only running 1 12. Grant it, it is an Orion. Bottum line is there is a lot more to it then just math. Now lets get into boes, ports and where the box is placed and where it it facing. Then we can argue about what is better, Ford or Chevy.