Hey guys.
So, I have had many people testify that multiple smaller subs will never have the same "sound" as a larger sub. I have also read where people will make this claim about midbass too.
However, I have never had anybody place any data behind the claim to back it up. There are are sorts of proclamations about greater visceral impact, weight of the sound, ect that are attributed larger woofers.
But what is the science behind this? It doesn't seem to make sense to me when all other factors are equal (cone area, displacement, ect). How can one subwoofer have more of the above attributes when compared to closely spaced multiple subs?
I am working on a PPSL design using multiple 8" (for car audio, but ignore that for the sake of the argument). But I am constantly reminded that they will not sound like a big 18" or a pair of 15"s
Does anybody have an explanation, or has this never been thoroughly explored?
Thanks.
So, I have had many people testify that multiple smaller subs will never have the same "sound" as a larger sub. I have also read where people will make this claim about midbass too.
However, I have never had anybody place any data behind the claim to back it up. There are are sorts of proclamations about greater visceral impact, weight of the sound, ect that are attributed larger woofers.
But what is the science behind this? It doesn't seem to make sense to me when all other factors are equal (cone area, displacement, ect). How can one subwoofer have more of the above attributes when compared to closely spaced multiple subs?
I am working on a PPSL design using multiple 8" (for car audio, but ignore that for the sake of the argument). But I am constantly reminded that they will not sound like a big 18" or a pair of 15"s
Does anybody have an explanation, or has this never been thoroughly explored?
Thanks.
My Dad made a sub with 20 6-1/2" drivers in it. He normally runs 15s. It sounded different but only because the frequency response was. If you did a blind test and you heard two subs that were the same frequency response at the same SPL, with the same amps and signal chain, you would most likely not be able to tell the difference. Even if it was 100- 3" subs Vs. 1- 96" sub.
They'd sound different, of course. Actually it's all physics, but please don't over simplify it. Several small ones is not equal to a big one. The only thing they're in common is cone area. And that doesn't mean everything.
The cone itself has its own optimized parameters per applications. Size, shape, mass, rigidity... etc. The motor, too.
For LF (under 200 Hz or so), cone breakup is usually not a problem. So, ideally it'd be the best when the size reaches the biggest at the given mass and rigidity.
And of course, all parameters have their individual trends, and there must be a point which is the best compromise of all factors for a certain target. (let's skip the cost, for now)
I'm not sure which size would be the best compromise for subwoofer in nowadays material technology, but from experiences, I'm pretty sure it won't be under 15".
That's for driver only. Room acoustic is another (complex) story.
The cone itself has its own optimized parameters per applications. Size, shape, mass, rigidity... etc. The motor, too.
For LF (under 200 Hz or so), cone breakup is usually not a problem. So, ideally it'd be the best when the size reaches the biggest at the given mass and rigidity.
And of course, all parameters have their individual trends, and there must be a point which is the best compromise of all factors for a certain target. (let's skip the cost, for now)
I'm not sure which size would be the best compromise for subwoofer in nowadays material technology, but from experiences, I'm pretty sure it won't be under 15".
That's for driver only. Room acoustic is another (complex) story.
I'm not oversimplifying anything. My point is that if you measure the response of two different subs and they measure close to each other, they will sound very close to each other too. Hearing is what matters. Most of what you perceive is frequency response.
I don't want to get into room acoustics, or cost or anything like that.
The job of the woofer is to displace air. The question is why some people believe that a large woofer displaces air differently than several small woofers.
To say that they will sound different, is not the same as saying that they can't sound the same. Again, the testimony is that there is some quality that is different with a large woofer over several small woofers. Some people even claim that using several small woofers will get loud, but will still only sound like several small woofers; there is something missing when compared to a single large woofer.
The job of the woofer is to displace air. The question is why some people believe that a large woofer displaces air differently than several small woofers.
To say that they will sound different, is not the same as saying that they can't sound the same. Again, the testimony is that there is some quality that is different with a large woofer over several small woofers. Some people even claim that using several small woofers will get loud, but will still only sound like several small woofers; there is something missing when compared to a single large woofer.
Generally speaking:
-Larger woofer's f3 is lower in frequency than smaller ones.
To me, this is the main thing that will affect what you hear as different. -When you add multiples of drivers, each one adds 3dB in SPL so if you use 4 or 5 smaller drivers, you don't have to push them as hard as just 1 so distortion from the cone not moving perfectly linear will be reduced.
Generally though people don't try to EQ their subs to get a flatter response so the smaller ones are reproducing 65-100Hz louder than other frequencies and they rolloff drastically below those frequencies. This is often described as mid-bass slam like in eighties movies explosions. The larger driver will have a peak that is lower, hit harder in the 35-65Hz area and often roll off up higher where the smaller driver is doing the best. So it will be described as deeper or tighter, pant flapping, whatever.
So.... from here you can either try to EQ one or the other to get the best of both worlds or...
Hook both up and mix the two into your system.
If you take things way too far, then do both AND EQ it to reproduce as many frequencies in the low end without peaks as possible. Hope this helps.
-Larger woofer's f3 is lower in frequency than smaller ones.
To me, this is the main thing that will affect what you hear as different. -When you add multiples of drivers, each one adds 3dB in SPL so if you use 4 or 5 smaller drivers, you don't have to push them as hard as just 1 so distortion from the cone not moving perfectly linear will be reduced.
Generally though people don't try to EQ their subs to get a flatter response so the smaller ones are reproducing 65-100Hz louder than other frequencies and they rolloff drastically below those frequencies. This is often described as mid-bass slam like in eighties movies explosions. The larger driver will have a peak that is lower, hit harder in the 35-65Hz area and often roll off up higher where the smaller driver is doing the best. So it will be described as deeper or tighter, pant flapping, whatever.
So.... from here you can either try to EQ one or the other to get the best of both worlds or...
Hook both up and mix the two into your system.
If you take things way too far, then do both AND EQ it to reproduce as many frequencies in the low end without peaks as possible. Hope this helps.
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All depends....
I had a space in a previous house that was previously (before major house renovations) the house doorway in a solid masonry wall (as is the nature of house front doors)and just behind my mids (which were crossover down to about 130 Hz).
I mounted 9 (or so, don't remember exactly) smallish excellent woofer drivers series-parallel and about half facing each way. The resulting total magnetic motor force was monumental. Likewise, the mechanical goodness as pistons (being small cones) was wonderful. And the total radiating surface, once again, was wonderfully large. So all those are great reasons for making a wall of small (but good) woofers working together (and assuming, I as I have for the last 50 years, that a mixed low-bass is a good idea).
The real problem is the free air resonance of small drivers, assuming you really don't want ridiculously heavy cones. At the time, I used motional feedback to power that doorway-of-subs right down through their resonance. There is no reason you can't shake a driver as forcefully as you want below it's resonance. You just can't do it with any kind of control without feedback.
(The alternative extreme, a single very large driver of maybe 18 inches, is hard to construct to the mechanical standards necessary.)
Ben
I had a space in a previous house that was previously (before major house renovations) the house doorway in a solid masonry wall (as is the nature of house front doors)and just behind my mids (which were crossover down to about 130 Hz).
I mounted 9 (or so, don't remember exactly) smallish excellent woofer drivers series-parallel and about half facing each way. The resulting total magnetic motor force was monumental. Likewise, the mechanical goodness as pistons (being small cones) was wonderful. And the total radiating surface, once again, was wonderfully large. So all those are great reasons for making a wall of small (but good) woofers working together (and assuming, I as I have for the last 50 years, that a mixed low-bass is a good idea).
The real problem is the free air resonance of small drivers, assuming you really don't want ridiculously heavy cones. At the time, I used motional feedback to power that doorway-of-subs right down through their resonance. There is no reason you can't shake a driver as forcefully as you want below it's resonance. You just can't do it with any kind of control without feedback.
(The alternative extreme, a single very large driver of maybe 18 inches, is hard to construct to the mechanical standards necessary.)
Ben
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How would you describe the sound of this feedback? Or is it something that shows up in a particular measurement?
Most often (but not always) the "FS" (free air resonance) of the smaller drivers will be higher so getting them to reproduce the lower frequencies can be challenging UNLESS you use something like TL (QWP) loading or tapped-pipe/tapped-horn sorts of alignments where the "FB" (cabinet's fundamental) can be much lower than the driver's FS ... In a tapped pipe for example the FS can be 1.5 to 1.6 x FB (or even a little more), its easy to remember by thinking that it is roughly the "golden ratio" 😉
Danley talked about this feature of tapped horns in his papers ...
I have used 8x 5" drivers in a folded tapped-pipe cabinet before and i was happy with the bass output .... Significant combined motor strength with lots of combined cone area without having too much moving mass made for some decent efficiency 🙂
Danley talked about this feature of tapped horns in his papers ...
I have used 8x 5" drivers in a folded tapped-pipe cabinet before and i was happy with the bass output .... Significant combined motor strength with lots of combined cone area without having too much moving mass made for some decent efficiency 🙂
Often forgotten facts when comparing two equal emitting areas, one provided by a large single driver, the other by a bunch of small ones :
- the linear excursion of small drivers is much smaller.
- the emitting area of the surrounds, which may considered as parasitic, is greater with the group of small drivers.
- the linear excursion of small drivers is much smaller.
- the emitting area of the surrounds, which may considered as parasitic, is greater with the group of small drivers.
"Motional feedback" or servo operation is a perennially hot topic. Very beneficial but tricky to implement. Discussed in various threads at DIYaudio.
Some small drivers have substantial excursion. But if you are requiring playing anywhere near the edge of excursion limit, you are doing something wrong.
Ben
Forr,
Thats true , smaller drivers will often (but not always) have less XMAX ....
Multiply the combined SD of all drivers (in your multiple driver option) by their XMAX figure in order to compare to another driver's SD * XMAX to get an idea of how much air can be displaced by each of your options that you are trying to decide upon ....
Thats true , smaller drivers will often (but not always) have less XMAX ....
Multiply the combined SD of all drivers (in your multiple driver option) by their XMAX figure in order to compare to another driver's SD * XMAX to get an idea of how much air can be displaced by each of your options that you are trying to decide upon ....
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Another factor to take into account is thermal loss/compression ... Driving a single woofer with a lot of power can heat up the voicecoil and make it lossy (4 to 6 or more DBs lost) .... You just end up with a fancy space heater that makes some noise 😛
Depending on the scenario multiple voicecoils may be better than one because of reduced thermal power compression losses.
Depending on the scenario multiple voicecoils may be better than one because of reduced thermal power compression losses.
true.
I figure 100 watts = +20db.
200 watts isn't usually +23db.
and 400 watts isn't +26db (probably less than +23db).
I don't expect much more from a driver.
If you need more output, add more drivers.
I figure 100 watts = +20db.
200 watts isn't usually +23db.
and 400 watts isn't +26db (probably less than +23db).
I don't expect much more from a driver.
If you need more output, add more drivers.
Oh, I gotchya, I misunderstood. That sounds really interesting for sure, did you get a chance to a/b your setup, with and without the Motional Feedback or was it built into the drivers? I guess the advantage to that vs EQ to extend the low end range would be a decrease in distortion but I wonder how much?
Smaller woofers seem to sound better to me. The issues as I see them are
1.) several small woofers that have equal cone surface area to the large woofer, won't have the same Xmax, which could be a problem. and
2.) a vertical array of smaller woofers (four 6 inch for example) might work significantly better with listening room acoustics as compared with a single 12 inch woofer, because of the waveguide effect they would have on the vertical axis. There would be less interaction with the floor and ceiling. At lower mid and bass frequencies the room acoustics play a huge part in what gets delivered to the listeners ears. I'm really enjoying the performance of the 6.5 inch Peerless Nomex cone woofers. Clean tight and lovely.
Some large woofer cones may have more distortion due to how they flex (conducted resonance) as well.
1.) several small woofers that have equal cone surface area to the large woofer, won't have the same Xmax, which could be a problem. and
2.) a vertical array of smaller woofers (four 6 inch for example) might work significantly better with listening room acoustics as compared with a single 12 inch woofer, because of the waveguide effect they would have on the vertical axis. There would be less interaction with the floor and ceiling. At lower mid and bass frequencies the room acoustics play a huge part in what gets delivered to the listeners ears. I'm really enjoying the performance of the 6.5 inch Peerless Nomex cone woofers. Clean tight and lovely.
Some large woofer cones may have more distortion due to how they flex (conducted resonance) as well.
I once heard a vented array of 25 2" drivers, 6mm xmax. That in itself is a lot for a 2" driver as said driver was made for LF reproduction in a small space. If you look at the math, this is the same cone area as 1 10" sub. There is not a single vented 10" sub out there that I would not take over this array.
People make this mistake a lot because cone area is never the end of the game. Even Vd is not the end of the game for a multitude of reasons. The most obvious of which is even when you add more and more and more cone area, you are not necessarily increasing the efficiency and/or sensitivity of the system in the region you're interested in.
Since we're talking about sub bass, this is especially true. Using multiples does not extend the bass response, the driver output sums according to basic acoustics laws. If your 2" driver subwoofer rolls off at 55Hz, and is 20dB down at 25Hz, then your 25x2" driver subwoofer will also roll off at 55Hz, just at a significantly higher SPL. The relative magnitude of 25Hz, however, will be exactly the same as before. Adding cone area does not act like an EQ to prop up the bottom end.
This is, of course, assuming the smaller drivers have the same Fs as the larger drivers which in almost all cases would call for a suspension as stiff as wet toilet paper. Even then, it's still not the same.
The amount of SPL is also still not dependent only on cone area and xmax. Pressure is force/area. The force is the B*l*i (having been applied to the mass, stiffness and resistive losses of the driver), where Bl is familiar to most people and i is the input current. The area is Sd. All we're talking about right now is Sd. A larger driver's motor supplies significantly higher Bli to the moving assembly. Ever wonder why two drivers, same size, same xmax, but one produces significantly higher SPL than another at a given frequency even though their excursion is the same? One is not imparting the same amount of force to the air, and this is directly related to how quickly the air is accelerated by the cone, not just oscillated.
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Assumptions have to be made for this discussion to focus on the OP's Q.
In the immortal words of the late Tom Nousaine: "Bass is Bass."
Data usually trumps opinions, so having a quick jaunt over to Data Bass and nicking a bit of Josh Ricci's excellent body of work, I took the CEA2010 Max Burst data for a 12 " driver and an 18" driver, each in a 1X sealed alignment and both driven by an amplifier that had lots of headroom.
Since what we hear is frequency response and in the cited case comparison both subs have virtually identical native FR and non-linearities are below the industry standards maximums for both subs, using 4 of the 12" drivers and level matching the 2 subs (a 1X18 vs a 4x12), there will be no discernible difference in playback of recorded program.
The 4 x 12" system is capable of higher output in dBSPL with equal measured non-linearity.
The 4x12" system can be configured in a dual-dual-opposed-driver system whereas the 1X18 cannot.
The 4x12 system can be separately built and placed to most likely result in a more accurate FR at the listening position (according to Toole, Geddes, et al) and the 1x18 cannot.
The 4 VCs in the 12s will heat up less than the single VC in the 18 = less power compression for equal output.
The 4x12 will require less excursion than the 18 for equal output = lower THD and affords one the option to further reduce THD by use of push-pull.
The facts are what they are. The majority of people draw their own conclusions based on what they think they are hearing. Actual data will always trump those unqualified opinions.
In the end, "Bass is Bass". If there is an audible difference, there is a measurable difference. When using world class drivers (an assumption that must be made or the discussion goes off into a good driver vs multiple bad driver discussion) in an actual room (or vehicle cabin) with boundaries, it is always gross differences in FR because one (also) assumes that the listener is not pushing either system beyond its designed capability in the comparison.
In the immortal words of the late Tom Nousaine: "Bass is Bass."
Data usually trumps opinions, so having a quick jaunt over to Data Bass and nicking a bit of Josh Ricci's excellent body of work, I took the CEA2010 Max Burst data for a 12 " driver and an 18" driver, each in a 1X sealed alignment and both driven by an amplifier that had lots of headroom.
Since what we hear is frequency response and in the cited case comparison both subs have virtually identical native FR and non-linearities are below the industry standards maximums for both subs, using 4 of the 12" drivers and level matching the 2 subs (a 1X18 vs a 4x12), there will be no discernible difference in playback of recorded program.
The 4 x 12" system is capable of higher output in dBSPL with equal measured non-linearity.
The 4x12" system can be configured in a dual-dual-opposed-driver system whereas the 1X18 cannot.
The 4x12 system can be separately built and placed to most likely result in a more accurate FR at the listening position (according to Toole, Geddes, et al) and the 1x18 cannot.
The 4 VCs in the 12s will heat up less than the single VC in the 18 = less power compression for equal output.
The 4x12 will require less excursion than the 18 for equal output = lower THD and affords one the option to further reduce THD by use of push-pull.
The facts are what they are. The majority of people draw their own conclusions based on what they think they are hearing. Actual data will always trump those unqualified opinions.
In the end, "Bass is Bass". If there is an audible difference, there is a measurable difference. When using world class drivers (an assumption that must be made or the discussion goes off into a good driver vs multiple bad driver discussion) in an actual room (or vehicle cabin) with boundaries, it is always gross differences in FR because one (also) assumes that the listener is not pushing either system beyond its designed capability in the comparison.
The amount and type of assumptions you made are incredibly unrealistic. You just so happened to find drivers who differ only in magnitude response, not frequency response. I will even ignore all of the "advantages" of a multiple subwoofer array which are strawmen at best, and distractions at worst.Assumptions have to be made for this discussion to focus on the OP's Q.
In the immortal words of the late Tom Nousaine: "Bass is Bass."
Data usually trumps opinions, so having a quick jaunt over to Data Bass and nicking a bit of Josh Ricci's excellent body of work, I took the CEA2010 Max Burst data for a 12 " driver and an 18" driver, each in a 1X sealed alignment and both driven by an amplifier that had lots of headroom.
Since what we hear is frequency response and in the cited case comparison both subs have virtually identical native FR and non-linearities are below the industry standards maximums for both subs, using 4 of the 12" drivers and level matching the 2 subs (a 1X18 vs a 4x12), there will be no discernible difference in playback of recorded program.
The 4 x 12" system is capable of higher output in dBSPL with equal measured non-linearity.
The 4x12" system can be configured in a dual-dual-opposed-driver system whereas the 1X18 cannot.
The 4x12 system can be separately built and placed to most likely result in a more accurate FR at the listening position (according to Toole, Geddes, et al) and the 1x18 cannot.
The 4 VCs in the 12s will heat up less than the single VC in the 18 = less power compression for equal output.
The 4x12 will require less excursion than the 18 for equal output = lower THD and affords one the option to further reduce THD by use of push-pull.
The facts are what they are. The majority of people draw their own conclusions based on what they think they are hearing. Actual data will always trump those unqualified opinions.
In the end, "Bass is Bass". If there is an audible difference, there is a measurable difference. When using world class drivers (an assumption that must be made or the discussion goes off into a good driver vs multiple bad driver discussion) in an actual room (or vehicle cabin) with boundaries, it is always gross differences in FR because one (also) assumes that the listener is not pushing either system beyond its designed capability in the comparison.
This is all besides the fact that you've missed the entire point of this argument, that cone area = cone area. Your 18" Sd is 254.34 in2. Your 4x12" Sd is 452.16 in2. Of course a system with a 78% increase in Sd will have greater sound power and lower distortion at a given SPL. Pray tell me, how exactly is this a comparison?
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