[emailtim]

Has anyone made any OB/Dipole W-Frames Subs with multiple drivers? 

• Using a even number of drivers would cancel out cabinet resonances (2 or 4).
• Using an odd number of drivers would yield same number of openings on the front and back, but would re-introduce cabinet resonances
• Running the drivers out of phase would reduce the even order distortions.
• The weight of all drivers would be evenly distributed around the entire bezel (assuming horizontally mounted drivers in a vertical column).
• All drivers (and weight) would be centered in the middle of the cabinet.
• Driver install/replacement would be more difficult.
• Overall height should be shorter.  Is this better or worse in a line source?

I am considering this cabinet designe as an alternative to H-Frames. 

I would like to get feedback on the pros and cons from those that have tried this configuration.

TIA

[bdp24]

Danny's original frame for two of his SW-12-16FR drivers was in what he called a W-frame (others call the same an M-frame). When he developed what ended up being the Super-V speaker, he went with an H-frame rather than a W for two reasons, he stated: First, mounting the co-ax driver atop an H-frame placed the co-ax at the height he wanted. A W-frame would have placed it too low. And second, the H-frame has a higher cavity resonant frequency than the W.

[Danny Richie]

Using a even number of drivers would cancel out cabinet resonances (2 or 4).
Using an odd number of drivers would yield same number of openings on the front and back, but would re-introduce cabinet resonances

Actually neither of those are true. Cabinet resonances are excited by the pressure the woofer puts on them. How many drivers you use doesn't change that. Cabinet wall flexing below resonance is actually a bigger problem.

Running the drivers out of phase would reduce the even order distortions.

If you are talking about running the driver facing opposite directions but acoustically in phase then theoretically there is some effect in this regard. If they are acoustically out of phase then they have no output.

The W frame allows the cabinet to be shorter. That is it's only advantage.

The H frame divides the cabinet up more evenly and is more solidly braced. The W frame allows for a larger un-braced panel area. Since cabinet wall flexing is a big deal with these I recommend the H frame and heavy side walls. If it has to be more compact the W frame works well too, but use really beefy side walls.

A W-frame would have placed it too low. And second, the H-frame has a higher cavity resonant frequency than the W.

Actually the cavity resonance issue has to due with box depth verses how high the woofers are allowed to play. So both H and W frames are the same in that regard.

[bdp24]

Right Danny, but for a given frame depth (say, 6.5"), the H-frame's cavity resonance is at a higher frequency than the W-frame's. The advantage for the H-frame is that for a given x/o frequency (say, 300Hz), it's cavity resonant frequency is further above the x/o frequency, allowing for a lower-order x/o rate, correct? And with the H having a higher CRF, it can be made deeper for more output than the W.

[Danny Richie]

Right Danny, but for a given frame depth (say, 6.5"), the H-frame's cavity resonance is at a higher frequency than the W-frame's. The advantage for the H-frame is that for a given x/o frequency (say, 300Hz), it's cavity resonant frequency is further above the x/o frequency, allowing for a lower-order x/o rate, correct? And with the H having a higher CRF, it can be made deeper for more output than the W.

Oh yeah, and the W frame is different on both sides. In both cases though it is above 400Hz for that depth. So for both styles you are in pretty good shape.

[Hank]

I want to build one or two dipoles to go with my recently acquired Acoustat Model 3's.  Here's a good article on the various "frame" types: http://www.hifizine.com/2012/12/subwoofer-origami/  The ripole looks interesting.

[Danny Richie]

I want to build one or two dipoles to go with my recently acquired Acoustat Model 3's.  Here's a good article on the various "frame" types: http://www.hifizine.com/2012/12/subwoofer-origami/  The ripole looks interesting.

The problem with the ripole is that it leaves a large panel area on each side of the box that is un-braced. And with the pressures these woofers create it becomes a buzz box. 

[Hank]

Well then, I'll creatively brace 'em.  My concern about the design is this:  would the SPL be enough for my dynamic music?

[Danny Richie]

Well then, I'll creatively brace 'em.  My concern about the design is this:  would the SPL be enough for my dynamic music?

This design also adds additional loading to the drivers. This is great for typical drivers with a lower Q in the .35 to .4 range. It is not going to help a driver designed for open baffle operation with a high Q design to begin with. It will also add some additional pressure to the cone causing an increase in distortion due to cone flexing that otherwise wouldn't be present.

The most ideal application I can think of for this design would be in car audio. Or any other application where pressure or SPL is valued over resolution and detail. It is almost like loading the drivers in a band-pass box. It just becomes an air pump.

[Hank]

Distortion?  DISTORTION??!!  You know I HATE distortion!    Well, I haven't read of any builders' experiences - just one guy who built a pair and he hinted that they may not have the SPL's for some:  http://jazzman-esl-page.blogspot.com/2011/01/ripole-subs-are-underway.html

Guess I'll consider the other OB configurations like M or W or Z.

[bdp24]

Distortion?  DISTORTION??!!  You know I HATE distortion!    Well, I haven't read of any builders' experiences - just one guy who built a pair and he hinted that they may not have the SPL's for some:  http://jazzman-esl-page.blogspot.com/2011/01/ripole-subs-are-underway.html

Guess I'll consider the other OB configurations like M or W or Z.

You can make a pair of W- or H- frame OB subs using two or three of the GR Research SW-12-16FR drivers per frame. They will keep up in SPL with any ELS you can name. There is one GR owner (THROWBACK) who posted pictures of his huge Sound Lab ESL's with a pair of 3-driver H-frames on the GR Research AudioCircle forum recently.