Dual Subs

[FierceTIMbo17]

Im a kid so i dont have the best set up just the Klipsch F-3's C-3 S-3 Sub 12 but i am wondering when i got this set up for my birthday my dad for some reason also purchased an extra sub-12 that has just been sitting around still in the box for a good 10 months now but my question is will i benefit from two subs?
this set up is in my room which is not very big 16x14 and pretty cramped (speaker set-up 42"dlp computer dressers and stuff and queen bed) so i was just wondering if it would do anything just to give it some use thanks

 

[zildjian]

try it

First of all, if you're a kid and you already have a 42"DLP TV,
Count yourself lucky!
I'd try both subs and see how you like it, especially if it's not being used at all. Two subs helps with standing wave problems, helps even out the bass in the room. Just turn down the level of the first sub a little and put the other sub in the mix too. If possible, position the 2nd sub in a different location than the first, otherwise it will get pretty much the same response from the room as the first sub.
Brad

 

[mulester7]

First of all, if you're a kid and you already have a 42"DLP TV,
Count yourself lucky!
I'd try both subs and see how you like it, especially if it's not being used at all. Two subs helps with standing wave problems, helps even out the bass in the room. Just turn down the level of the first sub a little and put the other sub in the mix too. If possible, position the 2nd sub in a different location than the first, otherwise it will get pretty much the same response from the room as the first sub.
Brad

.....VERY good advice, Zildjian....

....FierceTIMbo17, I suggest trying the two subs in the front soundstage equally split apart from the middle, ending up in the front corners is fine....unless one sub is a beach ball, and the other is a marble, you should get decent results with this setup....best wishes, and I embrace your thinking.....

 

[zildjian]

unless one sub is a beach ball, and the other is a marble, you should get decent results with this setup....

think both subs are the same, so it should be fine.
Thanks Mule.
Brad

 

[mulester7]

think both subs are the same, so it should be fine.
Thanks Mule.
Brad

.....oh, yes, if the subs are the same, he's home......

 

[Sheep]

Try opposing corners of the room (IE, front left, rear right). This article has many measurements of the room response of 2 subs in different locations.

If you've got a long enough sub cord, giver a shot!

SheepStar

 

[vierling]

Dual Subs ?

Because the wavelenght of the low freq´s is so big ( 40 Hz is 8.6 meter each wave ) the walls, ceiling and floor becomes the diffuser for that freq´s.
( You would need a 10 meter horn to control 40 Hz )
So, these waves will be reflected in the room, and in some points the reflected sound gets alligned with the direct sound from the speaker, and depending the phase of each wave, it will be cancelled.
So, I would recommend that first of all, You check what´s the size of the listening area in the room, because that will tell You where tu put Your sub´s.
Because of the size of the room, Do NOT put them away from a wall, try to use the corners, or center.
If You find the right spot, You could probably gain +6dB, so do not be affraid to experiment a little.
Remember that if the sub´s are as close as possible, they will work as one, and You will only get more power, but in the same omnidirectional pattern.
And if You put them away, You will start to control some directivity to the front, but more energy into the walls.

I have some info about this, and the acoustical color mapping of the sound waves in a room about that size. If You are interested I can mail them.

 

[mazersteven]

First of all, if you're a kid and you already have a 42"DLP TV,
Count yourself lucky!
I'd try both subs and see how you like it, especially if it's not being used at all. Two subs helps with standing wave problems, helps even out the bass in the room. Just turn down the level of the first sub a little and put the other sub in the mix too. If possible, position the 2nd sub in a different location than the first, otherwise it will get pretty much the same response from the room as the first sub.
Brad

Isn't is harder to calibrate two subs in different locations of the room? If he puts the subs together, he doesn't have to play with phase controls? Not saying it can't be done, but if he doesn't have much experience it's not the easiest to set up.

 

[vierling]

Here are some graphics that I made based on the size of Your room.
The sub´s are the white boxe´s, then You have a Lintening Position, and a Tv set.
Hope this helps.

 

[mtrycrafts]

Isn't is harder to calibrate two subs in different locations of the room? If he puts the subs together, he doesn't have to play with phase controls? Not saying it can't be done, but if he doesn't have much experience it's not the easiest to set up.

Well, it is. At some frequencies they will add together some, at some they will counter act each other, at some they both will cut deeply, and yet at some, no difference.
You may try one on top of the other?
Or, just forget it in that room.

 

[FierceTIMbo17]

Because the wavelenght of the low freq´s is so big ( 40 Hz is 8.6 meter each wave ) the walls, ceiling and floor becomes the diffuser for that freq´s.
( You would need a 10 meter horn to control 40 Hz )
So, these waves will be reflected in the room, and in some points the reflected sound gets alligned with the direct sound from the speaker, and depending the phase of each wave, it will be cancelled.
So, I would recommend that first of all, You check what´s the size of the listening area in the room, because that will tell You where tu put Your sub´s.
Because of the size of the room, Do NOT put them away from a wall, try to use the corners, or center.
If You find the right spot, You could probably gain +6dB, so do not be affraid to experiment a little.
Remember that if the sub´s are as close as possible, they will work as one, and You will only get more power, but in the same omnidirectional pattern.
And if You put them away, You will start to control some directivity to the front, but more energy into the walls.

I have some info about this, and the acoustical color mapping of the sound waves in a room about that size. If You are interested I can mail them.

yea i am actually confused about the whole sub set up i would be interested in the picutures and if it not too much trouble to explain them a little like i said my dad got my hooked, i dont know much but very egar to learn thanks for all the input

 

[vierling]

DUAL SUB´S FIELD RESPONSE # 1 of 3

In these acoustic predictions, We have a 100´ X 130´sound-field,
The reason for this is that I want You to understand how low-freq´s can expand.
This is a plan view projected with two subwoofers working together @ 40Hz, with the same specs, amps, and x-over filters.
Each one has 2 X 18" speakers, with a freq response of 28 Hz - 150Hz @ +-3dB, with a 600W amp.
All the sub´s have the same coverage (omni) so We can expect almost the same behavior in big or small speakers.

At the front ( X to the right ) is a microphone which can give us the freq response in that field, at 68º F and 20% relative humidity.

You can see that they expand to 360º when they are mounted one against the other.

In number 2 and 3 of these predictions You will see what happens if You separate the sub´s from each other.
Energy collapses to the center and starts to have deep cancellations in some areas, and sums energy in others,

Imagine that the reflected sound acts as a "virtual" speaker that is working in a different phase and time, against the original source.

Note: I am NOT calculating the reflections ( wall´s, floor or ceiling ) in this case, but if anyone would like to see another prediction, maybe with other dimensions, or freq´s, Just let me know !

 

[vierling]

DUAL SUB´S FIELD RESPONSE # 2 of 3 - (10´ separation)

In these acoustic predictions, We have a 100´ X 130´sound-field,
The reason for this is that I want You to understand how low-freq´s can expand.
This is a plan view projected with two subwoofers working together @ 40Hz, with the same specs, amps, and x-over filters.
Each one has 2 X 18" speakers, with a freq response of 28 Hz - 150Hz @ +-3dB, with a 600W amp.
All the sub´s have the same coverage (omni) so We can expect almost the same behavior in big or small speakers.

At the front ( X to the right ) is a microphone which can give us the freq response in that field, at 68º F and 20% relative humidity.

You can see that they expand to 360º when they are mounted one against the other.

In number 2 and 3 of these predictions You will see what happens if You separate the sub´s from each other.
Energy collapses to the center and starts to have deep cancellations in some areas, and sums energy in others,

In the Prediction #2 the sub´s are 10´ away from each other.

Imagine that the reflected sound acts as a "virtual" speaker that is working in a different phase and time, against the original source.

Note: I am NOT calculating the reflections ( wall´s, floor or ceiling ) in this case, but if anyone would like to see another prediction, maybe with other dimensions, or freq´s, Just let me know !

 

[vierling]

DUAL SUB´S FIELD RESPONSE # 3 of 3 - (20´ separation)

In these acoustic predictions, We have a 100´ X 130´sound-field,
The reason for this is that I want You to understand how low-freq´s can expand.
This is a plan view projected with two subwoofers working together @ 40Hz, with the same specs, amps, and x-over filters.
Each one has 2 X 18" speakers, with a freq response of 28 Hz - 150Hz @ +-3dB, with a 600W amp.
All the sub´s have the same coverage (omni) so We can expect almost the same behavior in big or small speakers.

At the front ( X to the right ) is a microphone which can give us the freq response in that field, at 68º F and 20% relative humidity.

You can see that they expand to 360º when they are mounted one against the other.

In number 2 and 3 of these predictions You will see what happens if You separate the sub´s from each other.
Energy collapses to the center and starts to have deep cancellations in some areas, and sums energy in others,

In the Prediction #3 the sub´s are 20´ away from each other.

Imagine that the reflected sound acts as a "virtual" speaker that is working in a different phase and time, against the original source.

Note: I am NOT calculating the reflections ( wall´s, floor or ceiling ) in this case, but if anyone would like to see another prediction, maybe with other dimensions, or freq´s, Just let me know !

 

[westcott]

Sheep is on the right track. The subs should oppose one another to get a wider sweet spot and to excite the fewest room modes. Corner placement may provide the best dB reinforcement but may do so at the cost of clarity. You will have to decide that for yourself. Try the opposing corners of the room, the center of the front and back wall, or the center of the two side walls.

Dr. Toole has written several white papers on this and if you are truly interested in learning more, I can dig them up for you.

 

[mulester7]

.....if you attempt to balance things out to where you're sitting inside the orchestras and whatever, as you listen to your audio system, I guess you might as well try the subs all over, but don't you honor the front soundstage?....the surrounds widen it, and the rears bring it closer, but don't you want to be right up next to the orchestra rather than out in it?....interesting subject....without a doubt for me, the subs are in the front corners with sealed-box drivers on the floor in the middle....oscillations you can SEE per concussion, below reference levels....I tried the 10's I have on the floor in the middle of the front soundstage, and anticipate the 15's....may not need 12's....we'll see....not enough hours in a day....where's Craigsub?....he probably DOES have an elevator in his house....ya'll didn't believe that, did ya'?, haha.........

 

[mike c]

get yourself the roomEQwizard and a measurement microphone(SPL meter will do)

that way, you can see realtime what your adjustments have changed in the frequency response.
colocating them would negate one of the major advantages of having 2 subs ... which is a flatter response. but you wouldnt know if it improved or got worse without measuring.

 

[westcott]

get yourself the roomEQwizard and a measurement microphone(SPL meter will do).

Not really. You need a much higher sample rate 1\10 octave or better for reliable results.

colocating them would negate one of the major advantages of having 2 subs ... which is a flatter response. but you wouldnt know if it improved or got worse without measuring.

Colocation may or may not produce a flatter frequency response. Most of the test results I have read contradict this statement and opposing placement is the recommended scenario.

Proper multi subwoofer placement

 

[vierling]

In that room size, i would go with the sub´s in the center, that way You´ll have an extra 4 dB, and flatter freq response, and You could even use some bass trap´s in the corners.

For analizing, I wouldn´t use an slp meter. I use Siaa Smaart Pro with an B&K Mic.

 

[westcott]

In that room size, i would go with the sub´s in the center, that way You´ll have an extra 4 dB, and flatter freq response, and You could even use some bass trap´s in the corners.

For analizing, I wouldn´t use an slp meter. I use Siaa Smaart Pro with an B&K Mic.

WOW! Usually when I try to explain to people that corner placement is not always the ideal sub placement, I get screaming and knashing of teeth from the box seats all the way up to the nose bleed section.

Long standing beliefs are hard to change and I am glad to see that at least one other person besides me has seen the light.