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Dual driver subwoofers...what say you ??

mcad64

Well-Known Member
I would like a dumbed down answer as to how they work and whether they are better/worse than a single driver sub. How does one place a dual driver subwoofer. Can it be placed like a single driver sub whereby the rear facing sub would essentially be firing at a wall less than 3 feet away? As you may be able to tell I have my eye on a new/ out of box dual driver subwoofer.
Thanks for any and all info!!
Mike
 
D

Deleted member 133

Guest
Mike,

I don't imagine that they'd be inherently better, or worse, than a single-driver sub. All else being equal I think they'd... perform the same.

Same with placement. Treat as you would any other sub. Find the spot that works best (which should be no different than for a single-driver sub) and place it there. Assuming it has one, reading the owner's manual might prove useful if there's something truly unique about it. But a driver firing at a wall "from 3 feet away" (or even 2 or 1) should not matter - any more than for a single-driver sub.

Jeff
 

Flint

Dog Faced Pony Soldier
Superstar
For the same money, dual driver subs are no better than single driver subs.

You could say the exact same thing about woofer size. For the same money, 18" subwoofers are no better than 12" subwoofers.

For example, if you pay $1000 for a dual 12" subwoofer, the performance is likely to be no better than a single 12" subwoofer which also costs $1000. In fact, I would be inclined to believe the dual 12" subwoofer is slightly lower performing because, in general, using dual drivers in a subwoofer is more of a gimmick than a sign of being better performing. Afterall, if a single higher quality woofer can perform equally as good, why bother with a dual woofer at all?

There are only two reasons going to a dual woofer arrangement makes sense:
1) The woofers are already state of the art to start with and the manufacturer wants to best the top of the line single woofer sub they already sell.
2) There is a need to address some physical limitation or goal for the consumer who wants to place a tall skinny (or short and flat) sub where a single large woofer would never fit.
 

Flint

Dog Faced Pony Soldier
Superstar
As for placement against a wall, the math is pretty easy. Take the cone area of the woofer(s) and compare it to the area between the woofer and the wall.

When the woofer is facing towards the wall:
If you have a single 12" woofer, the area of the cone is no more than approximately 113 in^2. The circumference of the woofer is about 38". So, the woofer needs to be at least 3" from the wall. This will prevent the acoustical pressure compression due to the propagation space being restrictive in relation to the woofer.

If you have two 12" woofers the distance is approximately the same since the woofers are spaced apart from one another. If the woofers are extremely close together, you may want to add an inch or two to the distance from the wall.

For other woofer sizes, the safe distance from the nearby wall is:

18" woofer = 4.5" from wall
15" woofer = 3.8" from wall
12" woofer = 3" from wall
 

Towen7

Well-Known Member
Staff member
Moderator
The distance between the woofer and the wall as discussed above is the distance from the wall to the woofer's cone... right?

If the sub 18" fires away from the wall and is in an enclosure that exceeds 10" deep, than the enclosure can be placed very close to the wall... right?
 

mcad64

Well-Known Member
Ok, so saying for a minute let's say that a dual 12" design is no better or no worse than a single. Some of the next things that pop in my head are amp size and pure heft. I can"t speak for cones and magnets and such as I don't know beyond that the cones are fiberglass what the rest of the components are made of.
I do know that the amp is a continuous 500W BASH (yea Canada!!) Class H amp and that the amp weighs in at a hefty 110 lbs. I know weight is not everything but I see these SVS's and HSU's that weigh a goodly amount so I assume that most play some small part. Same with the amp (more being better of course), though I am guessing Flint will say "All depends on the quality of the amp!".
My point is, when you aren't hearing a particular sound like you do with any given speaker, how does one evaluate a good sub? How often do people go out to an AV place to audition subs? Really???
Thanks,
Mike
 

Flint

Dog Faced Pony Soldier
Superstar
mcad64 said:
Ok, so saying for a minute let's say that a dual 12" design is no better or no worse than a single. Some of the next things that pop in my head are amp size and pure heft. I can"t speak for cones and magnets and such as I don't know beyond that the cones are fiberglass what the rest of the components are made of.
I do know that the amp is a continuous 500W BASH (yea Canada!!) Class H amp and that the amp weighs in at a hefty 110 lbs. I know weight is not everything but I see these SVS's and HSU's that weigh a goodly amount so I assume that most play some small part. Same with the amp (more being better of course), though I am guessing Flint will say "All depends on the quality of the amp!".
My point is, when you aren't hearing a particular sound like you do with any given speaker, how does one evaluate a good sub? How often do people go out to an AV place to audition subs? Really???
Thanks,
Mike

The performance of a subwoofer is a combination of the Woofer Driver, the Enclosure, and the Amplifier. The amp plays a part, but it isn't alone all that important considering that most sub amps are very, very good for the job and relatively affordable. The woofer driver and enclosure are what provide the most variation between subwooders.

You can take a dozen 15" subwoofer drivers and based on their design performance parameters calculate the given acoustic power output at the resonant frequency and power input assuming the enclosure is absolutely ideal. When you run those calculations you'll discover there is a HUGE difference between drivers, even at an identical given price point. Some woofers can operate to a much lower frequency for a given peak SPL, some can play much louder at higher frequencies for a given input power, and others can generate more output because they handle more power.

What I look for in a subwoofer is a very decent peak output to at least 25Hz (preferably lower), low THD at standard operating levels, fast & accurate transient response, and a rapid decay plot. These are often measured and tested on some DIY & enthusiast sites.

How can the average listener tell by going into a store and listening? He can't. Stores generally cannot setup a listening session with accurate settings and reasonable performance. They generally cannot provide a side by side comparison of a three or four subs - all setup perfectly. They cannot reproduce how the sub might perform in your room (acoustics play a massive role in how a sub performs in any given room). They cannot predict how loud the sub will have to play in your room, paired with your speakers, and so on.

What to listen for? Well, I've spent years writing guides, FAQs, providing test tracks, training people how to listen to those test tracks, tuning articles, testing articles, and so on and would hope that those are sufficient to help one learn how to judge a subwoofer's performance. The real problem with subs, in my opinion, is that until you have a very experienced trained ear and exposure to dozens of good subwoofers in ideal scenarios, then it should take several weeks to really know what you've got in your room.

As such, advice, esperience of others, test reports (comparing various subs using the same test procedures) and so on are your only reliable guides to picking subs.
 

Flint

Dog Faced Pony Soldier
Superstar
Towen7 said:
The distance between the woofer and the wall as discussed above is the distance from the wall to the woofer's cone... right?

If the sub 18" fires away from the wall and is in an enclosure that exceeds 10" deep, than the enclosure can be placed very close to the wall... right?

If the woofer fires away from the wall, none of this talk matter - unless the port fires into the wall.

Basically, you don't want to compress the acoustic load at all.
 

Randy

Well-Known Member
Famous
Great, now Flint tells me that my dual woofer SVS PB12+2 is no better than a single version. Gheez, if that thing didn't way a ton I would get rid of it.





BTW, I am completely joking^^^
 
D

Deleted member 133

Guest
Yeah it's a useless pile of garbage. Get rid of it. I can provide you with a shipping address. I'm happy to help you dispose of it.

ps. While I hear what Flint's saying, and intuitively what he says sounds (and is) right, there's room for exceptions. For example is it the case that a given manufacturer will offer single-driver sub "A" for X dollars and dual-driver "B" for X dollars as well? My guess is that it would not. They would instead charge more for "B" - which one presumes would represent the additional cost. They'd probably use two of the same driver that they'd use in A rather than two cheaper drivers. Drawing comparisons between manufacturers and their models would be difficult as well. For example I see no reason why a given manufacturer can't produce and sell a B for the same price as an A, and have B be the "better" sub - given the mix of fixed and variable costs that go into each. It would likely be the exception (for the reasons that Flint listed) in a small crowd, but possible nevertheless.

ps. But you still need to get rid of the SVS. Send it to me and don't worry about it any more.
 

Haywood

Well-Known Member
Famous
At the time I bought my dual-driver SVS PB12-Plus/2, it outperformed their best single-driver subwoofer. Then they came out with the PB-Ultra13 and that was no longer true. I would imagine that it would just kind of depend on the subwoofer and what's available at the time.
 

Randy

Well-Known Member
Famous
Jeff,
Thank you for trying to help me out. But alas that oversized paper weight of a sub that I have is too heavy for me to get back upstairs. So, it must stay.
 
D

Deleted member 133

Guest
Haywood said:
At the time I bought my dual-driver SVS PB12-Plus/2, it outperformed their best single-driver subwoofer. Then they came out with the PB-Ultra13 and that was no longer true. I would imagine that it would just kind of depend on the subwoofer and what's available at the time.
Since Randy doesn't know a good deal when it hits him between the eyes, I'll make you the same offer Haywood: ship that junk to me! :)
 

Razz

Well-Known Member
JeffMackwood said:
Haywood said:
At the time I bought my dual-driver SVS PB12-Plus/2, it outperformed their best single-driver subwoofer. Then they came out with the PB-Ultra13 and that was no longer true. I would imagine that it would just kind of depend on the subwoofer and what's available at the time.
Since Randy doesn't know a good deal when it hits him between the eyes, I'll make you the same offer Haywood: ship that junk to me! :)

Jeff
Three problems here...

1. You don't have the room for another sub!
2. Your wife will disown you!
3. We already have a Matt B here on the forum with too much bass in his system! (sorry Matt)
 

Yesfan70

I'm famous now bitches! vvvvv
Famous
Flint said:
.........

18" woofer = 4.5" from wall
15" woofer = 3.8" from wall
12" woofer = 3" from wall

.........


I can't believe no one has asked this, but I'm guessing this would also apply to down firing subs too, right? If so, then how close are some of SVS' woofers to the base on their tube subs? Also, do you have to take into account the woofer's p2p excursion?
 

Rope

Well-Known Member
Famous
SVS down firing 12" driver is 1 1/4" from the base, but I've placed the three ports (top) 4" from all walls.

Rope
 

Yesfan70

I'm famous now bitches! vvvvv
Famous
Rope said:
SVS down firing 12" driver is 1 1/4" from the base, but I've placed the three ports (top) 4" from all walls.

Rope


If the measurements Flint posted are observable rules for sub placement, then why did SVS choose to make the bottom base so close to the face of the subwoofer?
 

Flint

Dog Faced Pony Soldier
Superstar
My calculations are extremely safe assumptions of actual woofer cone size. If we get extremely detailed in calculating the cone area and circumference, the numbers would be smaller.

If you take the famous Dayton Titanic 12" subwoofer driver, the effective cone area is 197.9 in^2 and the effective circumference is 34.4". That means any baffle it is installed onto should be about 2.8" from the wall.

Peak to Peak excursion has nothing to do with the need to have a sufficient gap between a woofer cone and a wall (or floor).
 

Yesfan70

I'm famous now bitches! vvvvv
Famous
Flint said:
My calculations are extremely safe assumptions of actual woofer cone size. If we get extremely detailed in calculating the cone area and circumference, the numbers would be smaller.

If you take the famous Dayton Titanic 12" subwoofer driver, the effective cone area is 197.9 in^2 and the effective circumference is 34.4". That means any baffle it is installed onto should be about 2.8" from the wall.

Peak to Peak excursion has nothing to do with the need to have a sufficient gap between a woofer cone and a wall (or floor).


That's fine, but Rope's measurement still seems to come up short compared to your calculation for a 12" sub. I'm not saying your measurement is an absolute or SVS' is in error, but just thought maybe SVS or any audio speaker company would probably take the safer measurements when it comes to a sufficient gap.

This also doesn't mean I look at them, or any other company in a negative light. More than anything, this is just an observation I've noticed.
 
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