[e_biz80]

I've read a few posts about augmenting the OB subs upfront with some sealed subs in the back.  I know that they should be run out of phase from the front, but what about crossover settings?  should they be set at the same crossover point and level as the front subs?  thanks for you help everyone.

[Vince in TX]

I actually don't use the crossover setting for the OB subs.   I just have them connected to the high-level speaker input.   For the rear sub, it's at 80 Hz and is connected to the LFE channel out of phase with the front.

[mlundy57]

Subs located in different parts of the room usually require different settings. My front subs have different settings to get the same response at the listening position

[e_biz80]

Subs located in different parts of the room usually require different settings. My front subs have different settings to get the same response at the listening position

I hear you.  my front OB subs have different settings.  Guess I'll pull out the measurement mic and REW.  I read on here that Danny used subs in the rear of the room at shows running out of phase and at a lower volume, but can't find that post.

[DannyBadorine]

Adding more subs means more potential phase problems, especially when the subs start to have different settings.  It complicates things because you add so many timing issues with them.  You can potentially get a flatter frequency response but you might lose punch.  Make sure that you are measuring in many different places in the room and be sure to try different placements if that's possible.  If the subs are facing the opposite direction of each other (I.e; rear subs) then it is likely that the polarity on them should be flipped.  But if the rear subs are further from the listening position than the front subs then you can get a lot of phase issues unless you have DSP or a cooperative room.

[rich121]

Adding more subs means more potential phase problems, especially when the subs start to have different settings.  It complicates things because you add so many timing issues with them.  You can potentially get a flatter frequency response but you might lose punch.  Make sure that you are measuring in many different places in the room and be sure to try different placements if that's possible.  If the subs are facing the opposite direction of each other (I.e; rear subs) then it is likely that the polarity on them should be flipped.  But if the rear subs are further from the listening position than the front subs then you can get a lot of phase issues unless you have DSP or a cooperative room.

Adding subs to the opposite side of the room is a good way to fix room loading issues.
Using the JL Audio CR-1 makes sub integration perfection.

https://www.jlaudio.com/products/cr-1-home-audio-subwoofer-crossovers-96020

[DannyBadorine]

Adding subs to the opposite side of the room is a good way to fix room loading issues.
Using the JL Audio CR-1 makes sub integration perfection.

https://www.jlaudio.com/products/cr-1-home-audio-subwoofer-crossovers-96020

I'm not saying that it doesn't work.  It certainly does when it is implemented correctly.  I'm aware of the science.  But it can cause more problems than it solves.  And even when the frequency response is better, the phase can be worse and cause a lack of punch in the subs.

[HAL]

My understanding of the phase control on the A370's is that it is a linear phase style filter.  That is a constant time delay style control that can be adjusted to take into account positioning of the subs.  Convert the distance from the listening position to time delay (Td=D/(1130ft/sec)), where Td is delay time and D is distance from sub to the listening position. 

That should be a good place to start since all the A370 controls and sub locations will then be timed to the listening position.

[DannyBadorine]

My understanding of the phase control on the A370's is that it is a linear phase style filter.  That is a constant time delay style control that can be adjusted to take into account positioning of the subs.  Convert the distance from the listening position to time delay (Td=D/(1130ft/sec)), where Td is delay time and D is distance from sub to the listening position. 

That should be a good place to start since all the A370 controls and sub locations will then be timed to the listening position.

While this is true, it's important to remember that the low end from all of the subs us bouncing off of all of the walls and then returning to all other places (up, down, left, right, etc.) so with more subs you have more bouncing of different frequencies around the room.  Delaying them to one spot in the room can work, but it might put another spot out of phase, especially if the room is oddly shaped or the subs are different lengths away from walls.  Again, this can work, but it's complicated and it might only work at a specific listening position more than (for example) a few feet away from the center listening position.  And even if you delay your subs to each other, you have to get them to be in phase with the main speakers since those usually go as low as the subs.  Otherwise, you might just be adding energy, but not volume and punch with more subs. It's often the case that the mains need to be delayed to the subs, but we use the delay on the subs which can put them one cycle (or more) behind the mains.  This will cause low end smearing and a drastic loss of clarity (but might sound like it's correct since you haven't heard what it's supposed to sound like). I have used several different types of sub configurations (mostly in large scale venues) and even frequency coverage often sacrifices punch and power.  It's a game of compromise.
     Though I've never used open back subs, I would think that they would do better with multiple positions in the room since they should be activating the room more evenly, but I've never experimented with it.

[HAL]

Delaying the mains, if the subs are physically behind them is a very good thing to do.  I do it with my DSP XO system for my servo subs since they are physically behind the main speakers.

[DannyBadorine]

Delaying the mains, if the subs are physically behind them is a very good thing to do.  I do it with my DSP XO system for my servo subs since they are physically behind the main speakers.

Absolutely.  But if you have subs behind you and behind your mains, then the delay between the mains and subs will be different for each set.  So, you would have to delay the front subs to meet the back subs (out of polarity) to the listening position then delay the mains to that, which is still only delayed to one spot in the room and could create many problems, which is why I caution people against adding more subs in the room unless they really understand this and how to achieve it.