Subwoofers with dual opposed drivers are increasingly popular, witness B&W, Kef and now also SVS. I have two subwoofers, one a B&W PV1d with dual opposed 8 inch drivers and the other a more recently prurchased and much cheaper KEF Kube8b with one 8 inch driver. Not surprisingly the PV1d goes quite a bit deeper, but its output is also rather better defined/cleaner etc. Admittedly, the price difference was large, but I wondered if there are also sonic benefits from the dual opposed driver design that could be responsible for this.
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subwoofers with dual opposed drivers
- Thread starter Willem
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with a single driver you have vibrations / resonances in the cabinet that are typically dampened by adding more mass to the cabinet (bracing .etc).
dual opposed drivers eliminate cabinet vibrations / resonances, which depending on how much of a problem that is in a particular design it could make a decent improvement.
Other than that, 'meh'.
dual opposed drivers eliminate cabinet vibrations / resonances, which depending on how much of a problem that is in a particular design it could make a decent improvement.
Other than that, 'meh'.
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They typically won't impact "overall distortion" but will show up as harmonic distortion at the resonant frequencies of the cabinet / whatever is vibrating.
a well designed subwoofer should manage the resonances well, either by elimination with dual opposed or with dampening.
the only innovate use of dual opposed i found was in life style product where you want a lot of bass but you can't add mass to dampen resonances.
I never judge a sub with my ears in a room but with measurements: spl, distortion and csd
To me this sounds like a good reason to pursue the dual opposing technology
Count Arthur
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I'm very happy with my Dynaudio 18s: https://www.dynaudio.com/professional-audio/subwoofers/18s
It's in a completely different class to my previous REL, with a single down-firing 8" driver, and out-performs in it every way, but dispite having 2 bigger 9" drivers it transmits noticeably less "rumble" through the floor.
It's in a completely different class to my previous REL, with a single down-firing 8" driver, and out-performs in it every way, but dispite having 2 bigger 9" drivers it transmits noticeably less "rumble" through the floor.
Our single driver designs are very well damped and with rigid cabinets. So no, I wouldn't say that the impact of the dual opposing design is big. You can definitely feel by placing your hand on the cabinet that it vibrates less, but I would be hard pressed to claim that it is an audible difference. If you play so loud that the difference is audible, then, well, it probably still won't be audible since now your music is so loud.
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It's certainly good to minimize vibration. But the main path to achieve that should be a rigid cabinet design. Then a dual opposing design could be the frosting on the cake for sure. Our main reason for having such a subwoofer is to achieve higher SPL / capacity in a small form factor.
You can use mass on a dynamic absorber to change a mode shape like on a crankshaft "damper" but it isn't actually a damper, it changes the mode shape at resonance. Just adding mass lowers natural frequency but doesn't do any damping at all.
This is a common misapprehension.
Dual opposing drivers double the power handling (obviously) and double the driver area. They will excite the cabinet less it they are directly connected to each other (I assume most will be) but maybe not if mounted conventionally.
Yes, in fact without electronics equalisation to compensate for the inherent roll off due to the cabinet being small it would still be a bad idea but super powerful class D amps make it feasible nowadays.
My old sub is 27" high, 27" wide and 20" deep so far from unobtrusive.
HooStat
Addicted to Fun and Learning
Is a dual opposed sub equivalent to two single driver subs of similar size? Maybe "equivalent" is too strong -- but similar?
Prana Ferox
Addicted to Fun and Learning
If you want the 'same' frequency response but a few decibels more, then yes, the DO box needs to be roughly double the size of a single sub with the same driver / tuning. In a ported case, the port can be the same length but twice the cross-section.
If you make the box smaller, it will affect the tune, just as making a single sub smaller would do. Also, in the same way, any port size requirements go up to maintain tune and port velocity.
DO boxes also may be harder to place because now you have more sides you need to maintain clearance on, and you don't get the null-cancelling flexibility you would get with two actual boxes. OTOH buying commercially, the fact that it's one box and one amp can save money.
This isn't new, it seems mostly popular with car-audio style drivers with smaller diameter, big motors and extra-long xmax throws, leading to a lot of driver momentum to deal with. See for instance here. Generally, generally, if your priorities don't already dictate a small box and really long throw drivers, you're better off with a single larger driver.
If you make the box smaller, it will affect the tune, just as making a single sub smaller would do. Also, in the same way, any port size requirements go up to maintain tune and port velocity.
DO boxes also may be harder to place because now you have more sides you need to maintain clearance on, and you don't get the null-cancelling flexibility you would get with two actual boxes. OTOH buying commercially, the fact that it's one box and one amp can save money.
This isn't new, it seems mostly popular with car-audio style drivers with smaller diameter, big motors and extra-long xmax throws, leading to a lot of driver momentum to deal with. See for instance here. Generally, generally, if your priorities don't already dictate a small box and really long throw drivers, you're better off with a single larger driver.
Why would anyone reasonably view this as an "either-or?"
digitalfrost
Major Contributor
I made several DIY designs. The thing is, subwoofers move around if not dual-opposed, and the only thing helping that is weight. Especially on a wooden floor, the noise from a subwoofer moving about the floor can be huge.
I really like dual opposed designs because it's so simple, and makes so much sense. No matter the excursion or the weight, the thing should be steady and quiet. Modern floorstanders that have woofers in the back I also like, no matter if they try to do cardiod radiation pattern or not.
Ultrasonic
Addicted to Fun and Learning
Those subs are all likely principally using the dual-opposed design to try to get better performance from such small drivers (in subwoofer terms). There are larger and more capable subs that use the same approach though, from for example Power Sound Audio and Arendal. I once asked Tom Vodhanel of PSA (and formally the 'V' of SVS) to what extent there was an audible sound quality benefit from the dual-opposed approach and for what it's worth he basically said there wasn't one worth worrying about. And this was me enquiring as a potential customer where a dual-opposed product would have been more expensive.
