How loud is 2 x130db?

[WWDJ]

Let's say I have 2 subs capable of producing 130db each ... How loud is that in total?

[TonyB]

Approx 130db. Adding sound sources together is calculated on a logarithmic scale and doesn't cause a great increase in volume when two identical sources are used.

If the subs are placed a distance apart, there will be cancellation and the end result will be much the same as using one sub i.e. 130db. Place them right next to each other and there will be acoustic coupling which will produce about a 3db increase.

[Kernow]

133.01 decibels according to
http://www.sengpielaudio.com/calculator-spl.htm

[CRAZY K]

Approx 130db. Adding sound sources together is calculated on a logarithmic scale and doesn't cause a great increase in volume when two identical sources are used.

If the subs are placed a distance apart, there will be cancellation and the end result will be much the same as using one sub i.e. 130db. Place them right next to each other and there will be acoustic coupling which will produce about a 3db increase.

That would explain why I could work with one Sub and top last night in a small Marquee;)

[WWDJ]

Ok, so is there any point in using two subs, unless I can place them together?
The traditional sub-pole-top layout doesn't add any benefit apart from being aesthetically pleasing by the sounds of it?

[CRAZY K]

Ok, so is there any point in using two subs, unless I can place them together?
The traditional sub-pole-top layout doesn't add any benefit apart from being aesthetically pleasing by the sounds of it?

It does if you happen to be one side of a very wide the room near the speakers in question, I get this in big Barns;)

The alternative in a narrowish room is to place one sub and top slightly to the centre of the DJ booth/set up area which doesnt look right unless your excuse is ( like me last night) you cant get all the kit in the ......... Marquee.

Also its better to drive four speakers rather than two in terms of long life of the speakers, which has worked for me, or two rather than one in the case of tops.

[WWDJ]

It does if you happen to be one side of a very wide the room near the speakers in question, I get this in big Barns;)

The alternative in a narrowish room is to place one sub and top slightly to the centre of the DJ booth/set up area which doesnt look right unless your excuse is ( like me last night) you cant get all the kit in the ......... Marquee.

Also its better to drive four speakers rather than two in terms of long life of the speakers, which has worked for me, or two rather than one in the case of tops.

Or a sub under your booth and spread the tops, which would be my plan for a 3 box setup.

Currently plan is to buy a better sub and still save on buying 2 subs. I can then put that money towards a booth.

[TonyB]

Ok, so is there any point in using two subs, unless I can place them together?
The traditional sub-pole-top layout doesn't add any benefit apart from being aesthetically pleasing by the sounds of it?

Technically you are correct. I had a channel fail on the bass amp at an 18th party in a marquee. I didn't notice hardly any difference!

The advantages are:

Looks neater with a bass bin either side with a pole for the tops

Redundancy - if one fails you can carry on with the other with very little difference in sound

Bit of an iffy one but stereo separation - some tracks do have different left and right in the lower frequencies but in a disco situation its probably not that noticeable.

[paulg]

Take a look here:

http://www.astralsound.com/bass_pattern.htm

Two carefully placed subs will of course produce more sound than one - it's the same for all pa - that's why you see bass stacks and arrays of the same speakers.

Be careful with the bass coupling argument - putting them together can give about 3db more output than if the subs are placed apart, but that is not to say that the two subs have not already given about a 3db output increase when compared to one. You can get similar effects putting subs against walls. To put this into perspective, the average human ear will perceive around 6db increases as a doubling of sound.

All of this can be taken with a pinch of salt - It's theoretical and can seldom be achieved.

Bass cancellation can and does occur but it's fairly rare. I just wouldn't get hung up on it.

Putting stereo signals to stereo subs adds a further dimension - putting both left and right signals into a 'stereo' capable sub means that the unit will be slightly louder than splitting the signal across 2 subs. This is possibly what people are experiencing when they say one sub is louder than two. If you use a mono signal, this wouldn't be the case.

When I got my subs, I used a local club room for a night and just experimented. In the main, one 18" sub is more or less enough with two decent 12" tops. Two subs and two tops properly placed gives a better bass although it can be patchy depending where you stand. Two subs side by side is seemingly a little louder directly in front of them although there is not much difference further back in a room. The trouble with this set up (2 subs centre stage with no sub poles) is that people use your kit as drinks table!

The symmetrical argument is plain wrong.

[Digital Jack]

Bass cancellation can and does occur but it's fairly rare. I just wouldn't get hung up on it.



Now some folk may have an idea what the phase selection switch on their sub is for...

[yourdj]

Or a sub under your booth and spread the tops, which would be my plan for a 3 box setup.

Currently plan is to buy a better sub and still save on buying 2 subs. I can then put that money towards a booth.

I do this and it works a treat especially on my big flightcase which I am sure makes it louder. A central sub right next to the dancefloor (3 if needed) work good too.

You can see my big one and small one here under the black cloth hidden (on top of large flightcase)
Normally the speakers will be either side of the sub crossing each other at 3-5m ish range.

http://4.bp.blogspot.com/-8NtXBXta5ZY/TdhpHR3drPI/AAAAAAAADNc/pICz6_6wBx0/s320/IMG_1608.jpg

[katman]

Approx 130db. Adding sound sources together is calculated on a logarithmic scale and doesn't cause a great increase in volume when two identical sources are used.

I concur. you are doubling the power so a 3db increase.

4 cabinets would be a quadrupling of power so 6db increase.

3db is noticable but not significantly. As other people have said, loss of 1 channel will give a drop of 3db.

To double the volume you need a 10db increase.