[Danny Richie]

Well, when I referred to a "W"-frame configuration I meant completely parallel baffle plates.  So, a "W" that looks like this "|_|-|_|".  Sorry about that.  That configuration does have complete force cancellation.

I think this is what most people refer to as a W frame:



But what you are talking about (like in the latest Orion) will have complete force cancellation.

You can skip the free-air measurements, I believe you.  Your driver may indeed play easily to 20Hz, but it's because of equalization, not the servo configuration.

The servo system uses an extension filter much like a transform circuit. It monitors the driver and makes corrections that will maintain a linear response. 

A sealed box woofer will indeed play louder than an OB configuration......all other things being equal.  It will take you four OB subs to equal the SPL capability of one sealed-box woofer.....all other things being equal.

Check again what I said. And one pair of our OB servo subs in a H frame has about the same output as our sealed box servo sub (one woofer) It is pretty close though.

[Davey]

A pair of "H"-frame subwoofers (four drivers total) will have the same potential SPL capability as a single (one driver only) in a sealed box.  (The same drivers being used.)  That's what you meant?  That, I agree with.

The latest Orion woofer scheme is not the first to utilize the force cancelling configuration.  That dates to about twenty years ago (for Linkwitz designs) and I've seen drivers in that configuration from other folks way back when I was a young pup.  About 35 years ago. 

Your angled baffle OB system looks great.  That configuration trades off force cancellation for reduced height and larger cavities.  Depending upon the users floor construction (how vibration insensitive it is) that tradeoff might (or might not) work well.

I think you're missing my point regards equalization and servo configuration.  No problem.

Cheers,

Dave.

[Danny Richie]

A pair of "H"-frame subwoofers (four drivers total) will have the same potential SPL capability as a single (one driver only) in a sealed box.  (The same drivers being used.)  That's what you meant?  That, I agree with.

No, my in room response measurements show that two of our SW-12-16FR's (not 4) hit about the same SPL as a single SW-12-04 in a sealed box.

The latest Orion woofer scheme is not the first to utilize the force cancelling configuration.  That dates to about twenty years ago (for Linkwitz designs) and I've seen drivers in that configuration from other folks way back when I was a young pup.  About 35 years ago. 

Yes, I was just using the Orion as an example of one that might have been seen.

Your angled baffle OB system looks great.  That configuration trades off force cancellation for reduced height and larger cavities.  Depending upon the users floor construction (how vibration insensitive it is) that tradeoff might (or might not) work well.

It was originally built for height reasons, and it was just a test box used with various upper drivers.

The problem with it was that the woofers placed a LOT of pressure on the side panels. I eventually added a small brace in the front and lined it with No Rez. That was just so that it could be used in testing. What a design like this really needs is side panels that are at least 1.5" thick and lined with No Rez.

The H frame fared much better as the panels front and back were smaller and had a divider between the two woofers. So it was much more solid and sounded cleaner. I still recommend 1.5" thick walls and the No Rez. It definitely improves the sound.

In the Super-V's there is a rear box for each woofer that is partially overlapped by the side panels that are 1.25" thick. And it too really needs the No Rez.