With the proliferation of large bass drivers (18" and greater), is there a point where sound quality is second to displacement? (I am talking about bass rather than subwoofers although they are of interest too). Are drivers just getting bigger for the sake of it? Is 12" the optimal bass driver size? (I am talking about sealed or ported boxes). Are there limitations with the conventional materials used to make cones that create a maximum driver size?
I would be interested to know the science behind optimal/largest bass driver size. If there are special circumstances where larger drivers are achieving better sound quality then I am interested. I am aware that not everyone wants a 2 foot wide baffle but that can be ignored for now.
I would be interested to know the science behind optimal/largest bass driver size. If there are special circumstances where larger drivers are achieving better sound quality then I am interested. I am aware that not everyone wants a 2 foot wide baffle but that can be ignored for now.
I use larger than average drivers for an unusual reason, and yes, I do believe that bigger is better from this standpoint. Basically a bigger driver is more directional at higher frequencies and I use this to significant advantage. But if bass is all you are interested, then the answer would basically be, no the size isn't significant, its the \linear volume displacement thta matters. So in a sub its not significant, but in a main system it can be.
According to this book: Amazon.com: Loudspeakers: For music recording and reproduction (9780240520148): PHILIP NEWELL, Keith Holland: Books ,
the cones with larger then 18" would be too heavy to maintain the strength. Thus the ratio of Sd/Mmd has no longer any advantage.
I myself feel 15" is a very good compromise in home use. It's already very big for most people, though. Pro drivers in this size can have good combinations of sensitivity and fs - a good foundation to build something onto.
I've been using 18", which is less agile or jumpy then 15". However it goes lower, and OB helps a lot.
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edit: Ah, sorry I missed that <the science behind optimal/largest bass driver size>....
I think, besides the directivity character mentioned above, it's just a compromise under limitations of materials available, and the trial/error all these years (or we may say "experiences").
I saw a trend in the pro divers which they tend to have the cones heavier than before. Maybe that's good for ultra-high power live sound application, but a doubt for home use. To tune a 'proper' fs with heavier cone, the suspensions need to be stiffer. I think it's a double waste...
the cones with larger then 18" would be too heavy to maintain the strength. Thus the ratio of Sd/Mmd has no longer any advantage.
I myself feel 15" is a very good compromise in home use. It's already very big for most people, though. Pro drivers in this size can have good combinations of sensitivity and fs - a good foundation to build something onto.
I've been using 18", which is less agile or jumpy then 15". However it goes lower, and OB helps a lot.
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edit: Ah, sorry I missed that <the science behind optimal/largest bass driver size>....
I think, besides the directivity character mentioned above, it's just a compromise under limitations of materials available, and the trial/error all these years (or we may say "experiences").
I saw a trend in the pro divers which they tend to have the cones heavier than before. Maybe that's good for ultra-high power live sound application, but a doubt for home use. To tune a 'proper' fs with heavier cone, the suspensions need to be stiffer. I think it's a double waste...
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http://www.klippel.de/download/Nonlin/klippel, Loudspeaker nonlinearities - causes and symptoms.pdf
Note that compliance and force-induced errors resulting from increased excursion effect non-linear distortion. The larger the radiating surface area, generally the lower the excursion for a given freq.. (..of course different types of driver loading will also effect this.)
What is or isn't "optimal" is largely a matter of opinion, and relates heavily to the intended use and the overall design.
Large drivers rarely deform to any significant degree that would effect lower freq. reproduction (..but at higher freq.s - yes, possible).
Note that compliance and force-induced errors resulting from increased excursion effect non-linear distortion. The larger the radiating surface area, generally the lower the excursion for a given freq.. (..of course different types of driver loading will also effect this.)
What is or isn't "optimal" is largely a matter of opinion, and relates heavily to the intended use and the overall design.
Large drivers rarely deform to any significant degree that would effect lower freq. reproduction (..but at higher freq.s - yes, possible).
There's two issues here: the first is low frequency response. That's not a problem, provided the motor is strong enough to control the cone - see the 21" version of the Exodus Maelstrom-X, for instance.
The second issue is high frequency response - which is a whole different game, and in general, bigger cones don't do it very well. They also tend to come with bigger motors which tend to be more inductive, limiting HF response anyway (see the attached IB response of the aforementioned Maelstrom-X).
So, in short: large drivers make good subs, but not particularly great woofers for 2 or 3 way speakers.
The second issue is high frequency response - which is a whole different game, and in general, bigger cones don't do it very well. They also tend to come with bigger motors which tend to be more inductive, limiting HF response anyway (see the attached IB response of the aforementioned Maelstrom-X).
So, in short: large drivers make good subs, but not particularly great woofers for 2 or 3 way speakers.
Attachments
Larger drivers = greater cone depth and hence greater acoustic offset and diffraction for the other drivers.
It also means a larger baffle cutout and hence greater difficulty in keeping the baffle rigid.
I believe 12" is the best overall compromise in a conventional enclosure and that is probably why it's the most popular size.
It also means a larger baffle cutout and hence greater difficulty in keeping the baffle rigid.
I believe 12" is the best overall compromise in a conventional enclosure and that is probably why it's the most popular size.
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Of course it is more difficult to make a larger driver work well at higher frequencies, but it can be done. It takes a knowledgeable manufacturer to make it happen however. I use a 15" driver to about 800 Hz and a 12" to about 1 kHz -reasonable, but not typical.
Big drivers (>12") seem to me better in low bass < 40Hz but in the high bass (40-150Hz), i prefer a lot smaller driver (10" maximum) because they seem fast enough to give the good tempo to my ears. Why ? I don't know, it's highly subjective. It could explain why some manufacturers propose 10" drivers as maximum size, an other reason is WAF.
My 2 cents
My 2 cents
I remember reading somewhere that 12" drivers are the optimal size - something about lower moving mass etc, meaning they can stop and start easily.
Here we go....
The Subwoofer Conundrum
Chris
Here we go....
The Subwoofer Conundrum
Chris
I think you should compare for example 2 x 8" to 1 x 12"? Can 12" achieve some benefit? 2 x 8" gives acoustic benefit, taller radiation source.
Low Fs is achieved by adding mass or loosening spiders. So if you don't really need 20 Hz, it is no sense in using heavy cones. One larger cone might less rigid or linear than couple of smaller ones.
If using in main bass area, I would always look for driver which can handle 600 Hz without trouble. No XO in area where bass instruments are.
Low Fs is achieved by adding mass or loosening spiders. So if you don't really need 20 Hz, it is no sense in using heavy cones. One larger cone might less rigid or linear than couple of smaller ones.
If using in main bass area, I would always look for driver which can handle 600 Hz without trouble. No XO in area where bass instruments are.
Thats a benefit? How so? A lot of us want a narrower radiation source, especially vertically.
Sorry, I misread your post - yes two drivers stacked does narrow the polar pattern vertically, but if they are smaller drivers then it widens it horizontally.
Soft and natural bass needs bigger pistonic area
otherwise smaller cone needs to bigger(and speedy) Xmax to eliminate that disadvantages
so, this action results in shock bass
Everything is a trade off. Larger drivers do better at lower bass, but it becomes harder and harder to get acceptable transient response at the upper end of the driver's frequency range. The reason is that mass of the cone is one of the elements used to drive the Fs down and to create cone rigidity.
Baffle size is another issue. Strength is a concern and the baffle step response may be another issue. A 15" driver with a baffle width of 20" puts the baffle step at about 200 Hz, which is not a good point in the spectrum for a step response nor a crossover point.
Many others have listed valuable attributes of large drivers as well as their their ills. The long and short of it is that the process for selecting a driver is a complex one and the design of a system even more so. You have to look at the plusses and minuses and pick and choose the attributes that appeal to you the most, then weave those together to build the best system you can.
There simply is no perfect speaker. If there was it would be a single point source with no crossovers, resonances, or beaming/lobing. Nothing like that exists, except maybe in the world of Star Trek.
Pro audio 12" 15" woofers (B&C, AESpeakers, Eminence, JBL) work very well up past 100Hz. As well as the smaller woofers and they larger drivers have advantages we can use.
Augerpro did some great measurements last year with many larger woofers
Driver Measurements (drivervault)
Here is the distortion measurements for the TD12M (12" woofer from AESpeakers)
Very usuable up past 1K Hz.
Driver Measurements (drivervault)
Here is the distortion measurements for the TD12M (12" woofer from AESpeakers)
An externally hosted image should be here but it was not working when we last tested it.
Very usuable up past 1K Hz.
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