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Discussion Starter · #1 ·
2 subs, twice the power?


I know this has been discussed im sure but...


Does it really?


Im not asking if 2 (any brand) subs vs another bigger one sub and which one would be better.


id simply like to know do two of the same sub equal twice the power/sound/etc.?


when i was thinking about it i really didnt see how it could since the sound waves are bouncing off eachother disturbing themselves .


am i completely off on another planet??
(dont answer that last question)
 

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Quote:
Originally Posted by saltysteven /forum/post/21274844


2 subs, twice the power?


I know this has been discussed im sure but...


Does it really?


Im not asking if 2 (any brand) subs vs another bigger one sub and which one would be better.


id simply like to know do two of the same sub equal twice the power/sound/etc.?


when i was thinking about it i really didnt see how it could since the sound waves are bouncing off eachother disturbing themselves .


am i completely off on another planet??
(dont answer that last question)

If you have two subs, with each having 100watts, then yes, your total subwoofer system would have 200watts. This doesn't mean it will be twice as loud though. It will be more powerfull, maybe +3dB, which may or may not be noticeable. But, it will create a better sound in your area.


Two subs compared to one usually eliminate any dead spots you may have in your room. The bass should be smoother and more balanced, while being slightly louder and easier to feel.
 

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The benefits gained for theoretical co-location aren't an all or nothing proposition. The manner in which these spl gains occur doesn't begin at zero (given the 3db gain inherent to a second, like powered source), and jump to 6db at full co-location. It's a gradual process whereby the two distinct sources operate entirely separate from one another, and slowly sum to the total +6db due to constructive superimposition at the LP.


When two sources, sub-woofers in this case, are positioned relatively close to one another, whereby their acoustical centers are approximately within 1/4 wavelength, mutual coupling is the consequence. This mutual coupling sums their acoustic outputs over the frequency range involved (within 1/4 wavelength) and will couple combine and propagate as one unified waveform. The incremental nature of the constructive superimposition is due to the sources being increasingly in phase at the LP, then the two drivers essentially act as one larger, more capable driver.


Outdoors, we know two sources producing the same signal, regardless of spacing relative to one another, will mutually couple on axis and will result in a 6 dB increase in level. However, as the LP begins to move off axis, the coupling decreases as the distances from each sub to the listener increasingly change. Now the higher the frequencies involved, these changes occur much quicker.


Clearly, we see that the degree of the mutual coupling at any point off-axis is dependent on the sub spacing, and the frequency the sub is producing.


Good luck
 

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Discussion Starter · #5 ·
damn! I didnt expect such knowledgeable answers, thanks! I was just reading the myths and truths about subs. Alot more to it than i thought and I knew that going into it but really - now I understand why we have million dollar systems out there. This really is rocket science math to produce perfection.


Interesting idea about stacking the subs. And like i figured, sadly disappointing that the power doesnt exactly double.


thanks for the info- ill wait to see what one sub sounds like before i jump and order another
 

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Quote:
Originally Posted by saltysteven /forum/post/21275270


damn! I didnt expect such knowledgeable answers, thanks! I was just reading the myths and truths about subs. Alot more to it than i thought and I knew that going into it but really - now I understand why we have million dollar systems out there. This really is rocket science math to produce perfection.


Interesting idea about stacking the subs. And like i figured, sadly disappointing that the power doesnt exactly double.


thanks for the info- ill wait to see what one sub sounds like before i jump and order another

You might also be interested in the fact that to achieve twice the loudness, takes 10 db, the increase in loudness with a full 6 db increase which you might achieve with stacked subs, is 1.52X, and the loudness increase with 3 db increase, such as dual subs placed for the most even response, is 1.23X.
 

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Exactly, our hearing isn't linear with respect to level.


The Equal Loudness
Curves illustrate our hearing's non-linear behavior, relative to level.


The EL curves impact audio, starting with mix levels in the studio, all the way to the ultimate "free lunch" in audio, Pressure Vessel Gain, or PVG. As professionals, and enthusiasts, as we make our way through the technical side of audio, it certainly helps to be mindful of the impact of the Equal Loudness Curves.



Thanks
 

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Quote:
Originally Posted by spyboy /forum/post/21275332


You might also be interested in the fact that to achieve twice the loudness, takes 10 db, the increase in loudness with a full 6 db increase which you might achieve with stacked subs, is 1.52X, and the loudness increase with 3 db increase, such as dual subs placed for the most even response, is 1.23X.


Twice the loudness depends on frequency.


10 dB is 2X ELC rated at 1000 Hz.


6 dB is 2X ELC rated at around 40 Hz.



 

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Discussion Starter · #12 ·

Quote:
Originally Posted by KidHorn /forum/post/21279177


The short answer is twice the power as far as your power company is concerned, but not twice the volume.

Haha, true and funny!

Appreciated the replies ! I really have some reading to do to fully understand this math. Apparently its very complex
 

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Try this analogy; 1 horse and buggy with 500lb load going up a hill at a set speed vs 2 horses and buggy same load same speed.

2 would be much easier and if needed could go faster/harder with less effort. Subs-loud explosions & earthquakes with1 would run out of power/clip distort/compression, 2 would be less likely to.
 

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You could also relate the soundwaves to flowing water. With one water hose pumping water into the corner of a room, it will slowly fill the room, obviously filling the side it's on faster. Add a second hose to the opposite side of the room, at the same flow rate, and you now have a pretty even distribution of water flowing and filling up your room. Now, put two hoses (stacked perhaps) on the same side of a room, and you will now have about twice the flow of water.


The main benefit, like jackbuzz suggests, would be the added headroom from having two subs. Each sub wouldn't have to work as hard, and would provide plenty of bass to even out any dead spots you have in your room, while at times doubling to give the sense of stronger bass.
 

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Quote:
Originally Posted by J_Palmer_Cass /forum/post/21279246


Twice the loudness depends on frequency.


10 dB is 2X ELC rated at 1000 Hz.


6 dB is 2X ELC rated at around 40 Hz.



Fletcher-Munson adds another dimension to the mix. I based my statement on the following:

http://www.sengpielaudio.com/calculator-levelchange.htm


Buried in all of that is what seems to me to be the notion that changes in SPL are not the same as changes in loudness, and that while 6 db is twice the SPL, 10 db is twice the loudness. Perhaps the article I cited completely ignores Fletcher-Munson.


Thinking about it now, it makes sense that stacking 2 identical subs would give you twice the loudness at the typical ~6 db SPL increase.


My Google search seems to have missed integrating Fletcher-Munson.
 

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Discussion Starter · #16 ·
Thank you for the examples, im seeing a more clear picture.

Now what I don't get is if u put one horse on top of the other horse, what do you get besides a disturbing image, you perverts!!

Lol, no okay seriously. is there an analogy for that??
 

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I really like the analogies from some of the more experienced members as I'm new to learn about sub-woofers. Just got a new Martin Logan Dynamo 700 and my A/V receiver (Marantz SR7005) has inputs for 2 subs. Learning the end results of adding another sub via the analogies makes sense. Enjoying reading this thread. I'll see how my new sub sounds after watching some movies (blu-ray) and then decide if my overall experience would be "enhanced" by adding a second Dynamo 700.
 

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No question, due to the modal behavior in rooms, adding a second sub (or more) significantly smooth the frequency response. This is the primary benefit to adding a second sub in my opinion. The added realism afforded the listener by the extra output is merely a bonus



Thanks
 

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Quote:
Originally Posted by FOH /forum/post/21281689


No question, due to the modal behavior in rooms, adding a second sub (or more) significantly smooth the frequency response. This is the primary benefit to adding a second sub in my opinion. The added realism afforded the listener by the extra output is merely a bonus



Thanks

Thanks FOH! I look forward to it. I'll post my reviews once I order my Blu-ray Disc movies from Amazon and play them as is on my 3.1 setup. Then I'm SURE I'll upgrade to a 5.2 and then compare.
 
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