What are the advantages of a subwoofer with 3 speakers compared to a single speaker subwoofer?


#1

I have my eyes set on a certain 5.1 home cinema speaker set
I’ve listened to it in the store and it sounded amazing.

I do have a question about its subwoofer:

  • It’s an active subwoofer with a class D amplifier, 50x50x25 (cm) (length/width/height)
  • It contains 3 separate 130mm woofers

What are the (dis)advantages of this compared to a subwoofer with a singe ~25cm woofer.

I’ve seen the video from Paul talking about multiple driver speaker cabinets, but I’m uncertain about how this applies to a subwoofer.

Any info would be greatly appreciated, thanks.

Leon


#2

Multiple drivers, don’t have to work as hard as one, but there are lots of reasons.
Is it ported, or sealed? Are the drivers all active, or are one or two that are passive?
Do some research, look at reviews, and specs. Subs for music are more difficult to get right, than a thumper for home theater.


#3

One school of thought is that multiple smaller drivers can move the same amount of air as a single larger one, but since each has less moving mass due to their smaller cone size they can respond more quickly. They can also be positioned and/or wired with respect to their phase so that their motion as applied to the cabinet can effectively cancel their vibrations. Like with most things in audio there are always tradeoffs, and usually no single design approach is best in all respects and are compromised in one way or another.


#4

Three 130 mm (5 inch) woofers would be equivalent to one 23 cm (9 inch) woofer (the ability to displace air being the first criteria for producing bass). Bass wavelengths from typical subwoofers range from 17 m (57 ft, 20 Hz) to 170 cm (68 inches, 200 Hz), so other than total driver(s) area, driver design, and cabinet design/construction, multiple smaller drivers versus one large driver would have no effect on performance. On the surface seems like an inexpensive system meant for a small room that is being sold based on superficial specifications.

OTOH three subwoofers, placed randomly in the room is beneficial compared to a single subwoofer as the distributed bass sources would help even out bass response in the room. Note that bass travels in waves and being the size they are relative to a residential room they behave like a waves in a shallow bathtub where you slowly move your hand along the length of the tub. The waves travel to the end then bounce back where they impact the next waves traveling in the opposite direction. That impact will cause “interference” between the waves, either causing a cancellation or additive effect. For subwoofers the result can be +/- 20 dB frequency response depending on listener location and the given frequency. Multiple randomly placed subs will mitigate that interference. This is what I have at home.

Three drivers from the same cabinet will not produce that same mitigation effect, being too close together to make a difference relative to the size of the waves and room involved.

When doing in-store auditioning be aware of instant/short-term impressions. Best to trying listening in a similar room to what you’d use at home with recordings you’ve brought and take your time. I recommend taking notes to force you to concentrate on differences and avoid fleeting aural memory issues. Immediate impressiveness usually translates into exaggerations and listener fatigue.