sorry guys, i'm a mechanical engineer... so probably a silly question.
Are 2 subs in parallel going to be the same sound volume as 1 sub? (assuming i don't touch the volume knob, obviously).
I have 1 mono amp (old HSU 500 watt thingy) and 2 identical sealed subwoofers (parts express 15 inch (RSS390HF-4). I plug 1 sub into the amp and all is well. I plug the second sub into the amp and the sound output seems to be identical. I would expect it to double... but again, mechanical engineer...
Are 2 subs in parallel going to be the same sound volume as 1 sub? (assuming i don't touch the volume knob, obviously).
I have 1 mono amp (old HSU 500 watt thingy) and 2 identical sealed subwoofers (parts express 15 inch (RSS390HF-4). I plug 1 sub into the amp and all is well. I plug the second sub into the amp and the sound output seems to be identical. I would expect it to double... but again, mechanical engineer...
Rules of thumb:
dB laws, etc.
Some possible reasons for why it doesn't seem like double:
- your hearing isn't very sensitive at sub frequencies
- the 1st sub is in a corner (which makes it louder), and the additional sub is not
- problem with the amp and/or driver
- the first sub's response has a huge peak at one frequency, and this peak overwhelms anything else you do. e.g. see the 45Hz peak in graph 2 on this page:
Data-Bass
dB laws, etc.
Some possible reasons for why it doesn't seem like double:
- your hearing isn't very sensitive at sub frequencies
- the 1st sub is in a corner (which makes it louder), and the additional sub is not
- problem with the amp and/or driver
- the first sub's response has a huge peak at one frequency, and this peak overwhelms anything else you do. e.g. see the 45Hz peak in graph 2 on this page:
Data-Bass
thanks - i'll fiddle with stuff and check your suggestions
However, in theory... ideal world... would 2 subs plugged in to 1 mono amp be 2x as loud as 1 sub into that amp?
However, in theory... ideal world... would 2 subs plugged in to 1 mono amp be 2x as loud as 1 sub into that amp?
So you are perfectly qualified 🙂 , just need some focusing, Acoustics can be considered a subset of Mechanical Engineering.
To be more precise, a particular case of Pneumatics.
Speakers are nothing but pistons, mounted in a case wall, pushing a mechanical load: air.
Makes more sense now? 🙂
In fact, Classic Acoustics books explain everything that way, no need for speakers or Electronics, just air, pistons, resonant tubes and cavities, walls, etc.
Even sirens, about the loudest sound producing instruments created by Humans are purely Mechanical in nature.
Same as all Classic Musical instruments, from a jungle drum to a shepherd horn or flute to a Piano to a Pipe Organ, all mechanical.
ONE piston reproducing some kind of electrical wave will create a more or less accurate copy in the mechanical/acousting realm, displacing air which at any given point will exhibit a mix of speed and pressure variations, which we perceive as Sound.
Thus TWO pistons, if close enough and moving in the same direction ("in phase") and each as much as one moved before, will sum efforts , move more air at higher pressure and sound louder.
2 problems:
1) how much (measurably) louder?
there are different models to explain it, some say "twice as much" (3 dB) , others "4 times as much" (6 dB) ... personally I made many experiments and measured results lie between those two thoretical values.
There are experiments backing one or the other ... problem being that such experiments are different, and consider different premises. Oh well.
2) *our* measurement instrument is human ear, tremendously non linear, in fact close to Logarithmic response, which is good because thus we have huge range, from a mosquito quite far away to bomb explosions and jet engines, and bad, because "twice as loud" (measured) does NOT sound "twice as loud" (perceived by hunman ears).
Plus a host other nonlinearities and "lack of memory" which often make audible comparisons difficult.
So in a nutshell and back to your problem:
a) yes, two will sound louder than one
b) no, they will not be *perceived* as twice as loud.
c) couple that to lack of acoustical memory, organ tiredness or adaptation, etc, best way to run that experiment is to have one speaker continuously running, playing Music or noise, and switch the other in/out many times, best is using a relay so you don´t move , just push a little button to activate it.
I have such a setup to compare guitar speakers, go figure.
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There is another problem here.
If the 2 subwofers are connected in parallel, we lower the total impedance that the amplifier sees and we increase the power delivered by it ... And if they are connected in series, we increase the impedance and lower the power.
So I would be very aware if the amplifier can support the lower impedance, that is 2 ohms, which is risky for normal operation.
Are there amplifier specifications ?
If the 2 subwofers are connected in parallel, we lower the total impedance that the amplifier sees and we increase the power delivered by it ... And if they are connected in series, we increase the impedance and lower the power.
So I would be very aware if the amplifier can support the lower impedance, that is 2 ohms, which is risky for normal operation.
Are there amplifier specifications ?
Seems that some of those HSU amps can handle 2 ohms, so you might be good there for parallel operation. Also check the phase on the subs? Are they the same or out of phase? Depending on placement and bandwidth of sub, either option could be correct. Biggest effect would be to put them close to each other in a corner and wire them in parallel.
Also to add to JMFahey’s comments: an actual perceived doubling of loudness needs about 10 dB of extra sound pressure, so a second woofer will optimally only give you 6 dB.
Also to add to JMFahey’s comments: an actual perceived doubling of loudness needs about 10 dB of extra sound pressure, so a second woofer will optimally only give you 6 dB.
Nice, JM !
Regarding the dB boost, my understanding is deifferent from some others here. It's a very hard factor to find clear info on, oddly, but what I believe is true is this:
Adding a second speaker onto THE SAME AMP adds only 3 dB. You get 6 dB if you add a second POWERED sub. (Or a second amp.)
3 dB will never sound twice as loud.
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But there's another factor that has been overlooked: In your photo, you have a sub directly under the top speaker. Therefore, I assume the other sub is under the other speaker, i.e. spaced 6-10 feet apart in a smallish room. (You see where this is going....)
It's incredibly likely that you are now dealing with somewhat severe room nodes / comb filtering. So perhaps the bass frequencies that matter most to you (70 - 80 Hz, most likely) are getting nulled to some extent, thus negating the gain derived from the second sub in the first place.
Try grouping the subs in the middle, or wherever you can do it aesthetically, then move that groups around a little until you find a sweet spot. You might be very surprised at the result.
(You also will no longer be vibrating your HF driver, which is a very good thing.)
Regarding the dB boost, my understanding is deifferent from some others here. It's a very hard factor to find clear info on, oddly, but what I believe is true is this:
Adding a second speaker onto THE SAME AMP adds only 3 dB. You get 6 dB if you add a second POWERED sub. (Or a second amp.)
3 dB will never sound twice as loud.
---------------
But there's another factor that has been overlooked: In your photo, you have a sub directly under the top speaker. Therefore, I assume the other sub is under the other speaker, i.e. spaced 6-10 feet apart in a smallish room. (You see where this is going....)
It's incredibly likely that you are now dealing with somewhat severe room nodes / comb filtering. So perhaps the bass frequencies that matter most to you (70 - 80 Hz, most likely) are getting nulled to some extent, thus negating the gain derived from the second sub in the first place.
Try grouping the subs in the middle, or wherever you can do it aesthetically, then move that groups around a little until you find a sweet spot. You might be very surprised at the result.
(You also will no longer be vibrating your HF driver, which is a very good thing.)
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I'm sorry, but this is incorrect. If you use the same amp, and add a second woofer to the first; you either gain/lose nothing by wiring in series, or wire in parallel and gain 3dB in voltage sensitivity from halving the impedance, and doubling the cone area yields +3dB as well to yield +6dB in voltage sensitivity. If you are basing your answer on wattage, then you gain 3dB in power efficiency.
These are very different aspects of design, but since drivers are voltage drive based, then voltage sensitivity should be the norm, and yield +6dB in parallel; barring any cancellation or room nodes.
Later,
Wolf
These are very different aspects of design, but since drivers are voltage drive based, then voltage sensitivity should be the norm, and yield +6dB in parallel; barring any cancellation or room nodes.
Later,
Wolf
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