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Small drivers vs big drivers

Hi,
I have a question that is always in my mind recently. I see some speakers with small  drivers (5-9 inches) that is reviewed to be able to throw out big sound stage and go down to 18hz-20hz. Some other speakers with big drivers (10-15 inches) though are commented to have 'big sound stage' but can only go as low as 30-35hz. 

To make the situation more complicated, some speakers have small drivers but there are many of them. Can many small drivers be compensate for the size limitation?

I don't know which specs determine a wide sound stage and the ability to reach low frequencies.  What is the pros and cons of each design?

Thank you!

Huy.
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shadorne's avatar
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shadorne
7,333 posts
 
Large drivers with large diameter voice coils will push much more air and stay cooler and consequently remain incredibly dynamic and effortless at concert volume levels. Minimal distortion.

A small woofer with a small diameter voice coil pushes very little air and heats up very fast - they always sound dull and strained at realistic volumes. Lots of distortion.

Small Diameter = 6” with 1” voice coil
Large Diameter = 15” with 3”+ voice coil
bdp24's avatar
bdp24
4,908 posts
 

@shadorne raises an important point. During heavy excursions of its cone, a woofers voice coil heats up, changing the drivers electrical characteristics, and therefore its sound. One of the functions of the Servo-Feedback circuit in Rythmik subs is electronic compensation for the change in the woofers electrical characteristics due to voice coil temperature. No non-feedback woofer or sub is capable of that feat, one of the reasons for the uniquely clean (low distortion) sound of Rythmik subs. Sound like a sales pitch? Too bad ;-) .

The Servo-Feedback circuit also minimizes differences between the 12", 15", and 18" Rythmik woofers. Their sound characteristics are identical, the difference between them being in their maximum SPL capability. Rythmik also offers subs with 8" woofers, for those clinging to the idea that smaller woofers are "faster" than larger ones.

gregm
3,021 posts
 
@quanghuy147
To make the situation more complicated, some speakers have small drivers but there are many of them. Can many small drivers compensate for the size limitation
Yes, they can, but it's a whole different design ball-game! Generally, smaller diaphragmes are lightweitgh & therefore move faster but, being smaller, they reproduce lower frewuencies at an imperceptibly low amplitude (volume).
I don't know which specs determine a wide sound stage
The wide s-s is usually the result of efficient driving (i.e. small speakers) and a small baffle (small-sized speakers).
Numerous other design parametres are also invlovled, but let's not complicate the issue!

For difficulties in reproducing low frequencies through smaller drivers, see Shadorne above.

mzkmxcv
558 posts
 
There is not a 9” on the planet that can go down to 18Hz, so don’t know where you got that.

Besides just driver and cabinet size, driver xmax is important, that’s literally how much movement the driver can do, the more it can move back and forth, the deeper it can go.  
  
Soundstage is the off-axis of the speaker. If Speaker A has more output than Speaker B at 90° (perpendicular), than the soundstage will be wider. In terms of the quality of the soundstage (aka imaging), that’s how the off-axis performs, it should be very close to the on-axis.  
 
This speaker will have a wider soundstage and better imaging than this speaker.
twoleftears's avatar
twoleftears
1,457 posts
 
Despite multiples of 7" or 8" drivers having the same radiating surface when calculated mathematically, there's something about a 12" or larger that just sounds better.  Designers went to smaller drivers to make speakers narrow, for ergonomic and stylistic reasons; there's something really special though about a wide baffle speaker that can accommodate a big woofer on the front.
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