[dayneger]

I'm considering making a dual opposed sealed servo subwoofer, probably using a 14" sonotube / concrete form that I may leave exposed, or possibly hide in something else.  The intent is for these to be crossed over at around 60 Hz to the main speakers.

I like the dual opposed idea for the significant vibration reduction, and the sonotube for the weight and ease of construction.  The amp (A370PEQ shown) might also be behind it or embedded into the wall or... not sure yet. 

-  In the images below, I'm using a 48" long tube, provided I can find one.  This makes it easy to have 3 cu ft between the drivers and gives a little play to possibly put grills over the ends.  I've been reading about distributed subs and wondered whether 48" is actually enough distance for the 2 drivers to load the room more evenly--at least partially distributed?

-  Which combination of drivers and amps would be optimal?  I just noticed that the 4 and 8 ohm versions are quite different in the specs, and for cost/volume reasons I'd love to have just one amp.  Would the HX310 paired with the 8 ohm drivers wired in parallel work, or do I need the HX580-12S with 2 of the 4 ohm drivers?  Or something else?
















 

[Hobbsmeerkat]

The 8 and 16 ohm "FR" subwoofers cannot be used in such a configuration.
They are designed only to be used in open-baffle configurations, and they would require approximately 12 Cubic feet of airspace, per woofer.
The only woofers suitable for this design will be the 4ohm woofers, but you would also need to swap to the HX800 as it has 2x 400W channels, otherwise you would need two HX310 or A370 amplifiers to power them.

[WGH]

The amp (A370PEQ shown) might also be behind it or embedded into the wall or... not sure yet.

Danny Richie wrote:
"We recommend only using the length of wire that is on each amp. That gives you about an 18" umbilical that will allow you to move the amp around behind the woofers quite a bit."
https://www.audiocircle.com/index.php?topic=164028.msg1744272#msg1744272

Even if you put the amps in the base centered 24" from each end, the 18" wires will still be too short.

[dayneger]

The 8 and 16 ohm "FR" subwoofers cannot be used in such a configuration.
They are designed only to be used in open-baffle configurations, and they would require approximately 12 Cubic feet of airspace, per woofer.
The only woofers suitable for this design will be the 4ohm woofers, but you would also need to swap to the HX800 as it has 2x 400W channels, otherwise you would need two HX310 or A370 amplifiers to power them.

Thanks for confirming that, Hobbs.  Happy New Year!

Danny Richie wrote:
"We recommend only using the length of wire that is on each amp. That gives you about an 18" umbilical that will allow you to move the amp around behind the woofers quite a bit."
https://www.audiocircle.com/index.php?topic=164028.msg1744272#msg1744272

Even if you put the amps in the base centered 24" from each end, the 18" wires will still be too short.

I appreciate your chiming in on that.  That good news is that a while back Brian at Rythmik said longer leads would be fine, within reason, and other GR builders have successfully had them a few feet away.  As currently modeled, the actual speaker terminals are about 19 inches from the middle of the tube, so a few extra inches should be ok (or at least, a risk I'd be willing to take).

[dayneger]

Any idea whether the 4' of separation would be useful for the room distribution/loading, or should I consider going to a larger diameter and making these much shorter?

[Danny Richie]

Any idea whether the 4' of separation would be useful for the room distribution/loading, or should I consider going to a larger diameter and making these much shorter?

I would recommend the standard H frame design for the best results.

[WGH]

Any idea whether the 4' of separation would be useful for the room distribution/loading...

The perfect location for one end will probably not be the perfect location for the other end. Setting the sub diagonally 3' out from a room corner would load each end equally.

Another option is to make the tube longer and install it vertically. Many high end subs use a vertical stacked array to control room nodes and even out the sound. Be creative and have fun with this.

[Early B.]

I would recommend the standard H frame design for the best results.

I'm glad he said it 'cause I was thinking it. There's not much to be gained with a sonosub. Compared to an H-frame, a sonosub won't sound better and it won't fit in your room better. OK, it might be less expensive than a flat pack, but it's gonna be unsightly no matter what kind of lipstick you put on it.   

[Tyson]

I had an SVS sonotube sub back in the day.  It was not great.  I'd recommend avoiding that type of box.

[dayneger]

The perfect location for one end will probably not be the perfect location for the other end. Setting the sub diagonally 3' out from a room corner would load each end equally.

Another option is to make the tube longer and install it vertically. Many high end subs use a vertical stacked array to control room nodes and even out the sound. Be creative and have fun with this.

Going vertical is definitely an interesting notion--I've read very little about the impact of raising the drivers vertically into a room, but what little I've come across has been very positive.

I also like the rocket theme!   I was just at a friend's house and witnessed a barely 2-year old who absolutely Loves watching rocket launch videos... he tries to copy the sounds of the countdown and then squeals "blass off" while jumping in the air.

Maybe I could make a removable ring with hooks to turn it into a coat rack for guests.      I don't see why a cylinder should be any harder to make attractive in a space (at least my own space) than box-based subs, but to be fair I haven't tried yet.

The primary purpose of this sub will be to pressurize the room with deep bass for dance parties and that kind of thing, which is why I'd thought the monopole approach would be better than the H-frames.  Not correct?

The secondary purpose will be filling in the main speakers below 40-60 Hz for music.  My current mains are bass reflex, but I'm eyeballing OB/dipole builds for the future as well.  I'm a bit of a bass head in general.

I had an SVS sonotube sub back in the day.  It was not great.  I'd recommend avoiding that type of box.

I don't know how that SVS sub was done, but 2 dual opposed GR drivers pushed by a Rythmik servo amp in a sealed tube of appropriate volume with almost no baffle seems like it should be a pretty solid concept from the engineering perspective.  Am I missing something?

[corndog71]

I would recommend starting with the single sealed version in the flat pack cabinet.  I built mine as a tube and it works fine but I’ve had issues with placement.  Depending on your room a single will shake the walls.  2 singles are supposed to be ideal to help break up standing waves.

[Tyson]

I don't know how that SVS sub was done, but 2 dual opposed GR drivers pushed by a Rythmik servo amp in a sealed tube of appropriate volume with almost no baffle seems like it should be a pretty solid concept from the engineering perspective.  Am I missing something?

I was comparing the single driver sonosub to a single driver box sub and the sonosub always sounded muffled and muddy compared to the box sub, with similar quality drivers. 

[Danny Richie]

I don't know how that SVS sub was done, but 2 dual opposed GR drivers pushed by a Rythmik servo amp in a sealed tube of appropriate volume with almost no baffle seems like it should be a pretty solid concept from the engineering perspective.  Am I missing something?

Our 8 ohm and 16 ohm woofers are designed for free air applications. So putting them in a box requires a huge air space.

Also, once you go open baffle, you won't go back. They will dig deep and hard hard, but won't pressurize the room in the same way. They have far less room boom.