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Dual Subs..
Old 15th October 2013
  #1
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Dual Subs..

I am using an Anthony Gallo mps-150 sub for my 2 channel set up. Speakers are Usher BE-718. A new piece of the same sub has come up for sale, so I was wondering if running 2 identically similar subs would benefit.
With my present set-up, I have wired the existing sub via pre-outputs on the preamp. If I add another, do I use a simple Y splitter from each channel & hook up simultaneously?


Sent from my GT-N7100
Old 15th October 2013
  #2
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I've found multiple subs to be noticeably better than a single. For my Magnepans I always ran a pair next to them with much better results than just using a single and trying to find the optimal location for it in the room. With my full range speakers that already have the ability to reproduce the lowest octaves I move the subs to the rear wall (about four feet behind me spread six feet apart) and run them at a slightly lower volume than the mains. The end result is a smoother, flatter LF response. I'm not really a bookshelf speaker guy, but I recently picked up a pair of the Adam Jones designed Pioneer -22's just to see what all the fuss was about (they are pretty damn impressive) and found the subs kept at the rear wall sounded fantastic with them with seamless integration. You can certainly go with more than two subs to accomplish additional smoothing of the LF response and this is referred to as "distributed bass" and is a good tool for overcoming a room's acoustic issues if you can't accommodate a lot of room treatments.

- Michael
Old 15th October 2013
  #3
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What result are you getting with one sub?

In running two subs, what are you hoping to make better?

1) bass smoothness?
2) bass extension?
3) bass decay?
Old 15th October 2013
  #4
Old 15th October 2013
  #5
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Quote:
Originally Posted by jim1961 View Post
What result are you getting with one sub?

In running two subs, what are you hoping to make better?

1) bass smoothness?
2) bass extension?
3) bass decay?
To make the bass more evenly distrubuted in the room. I also have around 28 broadband panels in the room & will be adding a few pressure based traps soon.
Since im using bookshelf speakers, I most certainly need a sub (which I do). Its time & again been mentioned that two subs make the response much more better than optimizing just one sub with placement..

Sent from my GT-N7100
Old 15th October 2013
  #6
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I should add I have a decent amount of bass trapping and broadband absorption in my room....so the results I'm getting likely wouldn't have been as favorable had the room been untreated. Just wanting to clarify here that I'm NOT implying multi-sub/distributed bass is a suitable replacement for a well-implemented acoustic treatment scenario. However, if you can't acoustically treat "to the nines" a multi-sub/distributed bass set-up used in conjunction with some well-executed LF absorption can pay off handsomely.
Old 15th October 2013
  #7
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Quote:
Originally Posted by SörenHjalmarsson View Post
Nice read

SAC once told me that dealing with room responses can be compared to a balloon. You push in at one side and it often times pushes out in another (these are not his exact words, but captures the meaning).
Old 15th October 2013
  #8
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Quote:
Originally Posted by jim1961 View Post
Nice read

SAC once told me that dealing with room responses can be compared to a balloon. You push in at one side and it often times pushes out in another (these are not his exact words, but captures the meaning).
So u dont really suggest adding another sub? I want to place both the subs & the mains on the arc of the circle, the center of which is the listening chair, such that all are equidistant. I guess u have done the same, though u preferred to place the sub behind ur LP, but maintaining the same distance from urself to the mains as well..

Sent from my GT-N7100
Old 15th October 2013
  #9
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Quote:
Originally Posted by Jolida View Post
So u dont really suggest adding another sub? I want to place both the subs & the mains on the arc of the circle, the center of which is the listening chair, such that all are equidistant. I guess u have done the same, though u preferred to place the sub behind ur LP, but maintaining the same distance from urself to the mains as well..

Sent from my GT-N7100
I am neither for or against it. It all depends where you are starting from and what your goals are. And while you have stated a goal, I am pretty sure your not willing to compromise the sound at the LP to achieve it.

On another note, putting a sub the same distance as the main speakers from the LP (regardless of direction) doesn't guarantee a flat response from it. In the bass region where a sub typically operates, its the SBIR (reflections) characteristics that will determine how flat the overall response is and this will vary greatly upon specific placement. With two subs, this becomes even more complex.

You may very well get what your after by adding an additional sub. I am not saying otherwise. But its not an automatic proposition.
Old 15th October 2013
  #10
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Quote:
Originally Posted by Jolida View Post
I am using an Anthony Gallo mps-150 sub for my 2 channel set up. Speakers are Usher BE-718. A new piece of the same sub has come up for sale, so I was wondering if running 2 identically similar subs would benefit.
With my present set-up, I have wired the existing sub via pre-outputs on the preamp. If I add another, do I use a simple Y splitter from each channel & hook up simultaneously?


Sent from my GT-N7100
Nothing wrong with adding another sub. Are the subs going to be in stereo or in mono?

The question is if x-over is going to be applyed or not and not to forget the time delay between the mains and the subs. Otherwise there will be phase issues.
Old 15th October 2013
  #11
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As explained the reason for adding a subwoofer is to extend the bandwidth of the system, not to remediate resonant or non-resonant room problems, the same is true with a dual sub set-up....

The reason you'd want to use a 2.2 over a 2.1 set-up is:

1. It provides more headroom.
2. It provides a more convincing and accurate sound stage and stereo image.
3. It avoids some inherent acoustic problems with the 2.1 set-up.
4. Two subs looks cooler than one.

Although full range speakers are more easily integrated from the get go, having subwoofer(s) can enable more control over SBIR related issues.


--Sören
Old 15th October 2013
  #12
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Having 2 subs will NOT help to make the soundfield more evenly distributed. In fact it will narrow it to exactly between the subs. More bass traps is what you want, with one sub, for better fidelity at arbitrary location. Two subs can work as one if they are next to each other, but not spread out 60º
Old 15th October 2013
  #13
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Quote:
Originally Posted by OpusOfTrolls View Post
Having 2 subs will NOT help to make the soundfield more evenly distributed. In fact it will narrow it to exactly between the subs. More bass traps is what you want, with one sub, for better fidelity at arbitrary location. Two subs can work as one if they are next to each other, but not spread out 60º
Do you feel this to be the case for full range speakers, as well? Because, in essence, in that example there would be two subs, or one LF driver/cabinet (and not next to one another). Are you suggesting a pair of full range speakers will have a narrower "soundfield" than a pair of bookshelf speakers/monitors with one subwoofer...simply because there are two LF drivers rather than one? I don't disagree with the need for bass trapping, but my experience is not consistent with your first comment regarding two subs creating a more narrow "soundfield" than one.....be it a pair of LF drivers in a full range loudspeaker design or a pair of dedicated subs located away from one another.
Old 16th October 2013
  #14
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Well, it's hard to explain, but it has to do with interference from one sub into the other sub's radiation. If you have two subwoofers spaced 8 feet apart, 70hz radiation to the side (of the subwoofers, offaxis) will be diminished because it is the half wavelength of the distance between them. On the center axis, equal distance from listener to both subs, there is no interference (except the room). As soon as equal distance from both subs is broken, the soundfield experiences interference.

But two subs CAN improve fidelity onaxis, just not everywhere in the room.
Old 16th October 2013
  #15
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Quote:
Originally Posted by SörenHjalmarsson View Post

The reason you'd want to use a 2.2 over a 2.1 set-up is:

1. It provides more headroom.

Yes, but only twice as much

2. It provides a more convincing and accurate sound stage and stereo image.

Not so sure about this, do you know any recordings that have stereo information below 100hz?

3. It avoids some inherent acoustic problems with the 2.1 set-up.

Such as an offaxis subwoofer?

4. Two subs looks cooler than one.


Old 17th October 2013
  #16
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Quote:
Originally Posted by OpusOfTrolls View Post
Well, it's hard to explain, but it has to do with interference from one sub into the other sub's radiation. If you have two subwoofers spaced 8 feet apart, 70hz radiation to the side (of the subwoofers, offaxis) will be diminished because it is the half wavelength of the distance between them. On the center axis, equal distance from listener to both subs, there is no interference (except the room). As soon as equal distance from both subs is broken, the soundfield experiences interference.

But two subs CAN improve fidelity onaxis, just not everywhere in the room.
Opus, please explain this in detail ;-) phase canceling to me is if the phase is inverted for example caused by reflection of a massive wall or the phase modification knob on the subwoofer/ amp itself. You can hear phase problems in stereo environments very easy if mono is out of center. The same case with bass. Also stereo full range systems do not have those problems if they are setup right. If you ever try 2.2 yourself it will convince you. Sören nailed the points. Locating frequencys under 50hz is not possible?! But which subwoofer produces such a clean tune in real life? So improving the stereo image is most often to get airflow noise in the center. Also if the room itself has several room mode problems 2.2 and also up to 4 subwoofers can help in most situations. This is no theory. This is also my experience. At the end and also the last point with the optical aspect: symmetry and reflection counts too... If you have only one big sub by one side this will change the reflections on only one side too :-) Off course in most situations one sub is better than no sub and even works fine but two to the mains perfect matching subs are simply one step above.
Old 17th October 2013
  #17
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Quote:
Originally Posted by dmsmastering View Post
please explain this in detail
I don't really know how, but when two soundwaves coincide out of phase (ala half wavelength), maximum destructive interference occurs and minimum pressure generated.
Old 20th October 2013
  #19
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