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Optimal bass driver size for sound quality - is bigger really better?
Optimal bass driver size for sound quality - is bigger really better?
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Old 8th March 2010, 02:27 AM   #1
Antripodean is offline Antripodean  Australia
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Question Optimal bass driver size for sound quality - is bigger really better?

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.
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Old 8th March 2010, 02:53 AM   #2
gedlee is offline gedlee  United States
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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.
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Old 8th March 2010, 03:17 AM   #3
CLS is offline CLS  Taiwan
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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.

-----------------

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...

Last edited by CLS; 8th March 2010 at 03:34 AM.
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Old 8th March 2010, 03:48 AM   #4
ScottG is offline ScottG  United States
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http://www.klippel.de/download/Nonli...20symptoms.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).
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Old 8th March 2010, 03:52 AM   #5
TheSeekerr is offline TheSeekerr  Australia
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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.
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Old 8th March 2010, 04:33 AM   #6
David Gatti is offline David Gatti  Australia
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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.

Last edited by David Gatti; 8th March 2010 at 04:37 AM.
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Old 8th March 2010, 04:50 AM   #7
gedlee is offline gedlee  United States
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Quote:
Originally Posted by TheSeekerr View Post
So, in short: large drivers make good subs, but not particularly great woofers for 2 or 3 way speakers.
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.
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Old 8th March 2010, 06:18 AM   #8
jerome69 is offline jerome69  France
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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
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Old 8th March 2010, 06:24 AM   #9
chris661 is offline chris661  United Kingdom
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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
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Old 8th March 2010, 06:44 AM   #10
alspe is offline alspe  Finland
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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.
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