DaVibe

iTrader: (9)

So this thread is branched from another thread, talking about 1 sub vs. 2 ...
These two posts came up:

So, with this in mind, I'm wondering if anyone has ever put a statistic together or formula for determining this.
If everything remains the same (same vehicle, same power, etc) HOW MUCH of an advtange is there?

Example:
If 2 12" 400 RMS subs run against 1 15" 1000 RMS sub, will 800 RMS (24") sound louder?

Are the advantages that significant? Loss of space, strain on the amplifier and your system (vs. running 1 sub) ...

Lets take a step forward ...
Would you say 2 12" 300 RMS subs can be comparible to a single 12" or 15" 1000 RMS sub?

I'm talking about well built boxes in the same vehicle ... not a crappy box for a 1000rms vs. a tuned box for 600rms ... I'm talking two tuned boxes.
What are your OPINIONS?

Father Yuli

iTrader: (17)

Rob are we keeping the power same or no? At first you say let's keep the same power but in your examples you are comparing subs with different RMS. That's an apples to potatoes comparison.

with same power there would also be no increased strain on the amplifier.

with SAME power, more cone will be louder. the formula goes something like this,

same power + double the cone = 1.5 db louder.

when the power is NOT the same (like in the examples above), not even Jesus would know the answer to this question. Only maybe Peter MTA would.

It all comes down to effective and efficient use of the coil/speaker with the power you have. In the tests I've done myself, I have seen positive results when cone area is increased and power is decreased at the same time. By positive results I mean more cone would still get louder, even with less power. Not only less power in total but also less power PER coil/woofer.

Efficiency/effectiveness is a spectrum, it is all about finding that balance when it comes to your coil(s)/speaker(s) and the power you have. I know this is getting too far into the hardcore spl aspect of it, sorry if I got carried away.

fresh1

iTrader: (2)

And here I was coming to be the jerk and say the best formula to show that more cone area means louder is 2+0=2 < 2+2=4.

Father Yuli

iTrader: (17)

lol Myles. The actually physics formula for this is derived from (or using) a LOG function, but you were close.

DaVibe

iTrader: (9)

Alright fair enough ...

So what you're saying is that 2 10" Subs at 600rms (= 1200rms) will be louder than a single, 12" 1200rms sub, purely because there's more cone ...

And from what I gather from everything you just said ... there's something to say about 4 subs that can only handle 300rms, vs a single sub that can handle 1200rms ...
Sub quality ...

At least that's my thinking ...

Sasha

iTrader: (10)

Rob, you also need to realize something else. You seem to be under impression that 15" is 15" and two 12"'s are 24". That is not the correct calculation of cone area. You have to look at the speaker T/S's and check SD spec, which is measured in square cms. True cone area is on average 310 cm2 for a 10" sub, 480 cm2 for a 12", and 810 cm2 for a 15"

So according to your calculations three 10's will be the same as two 15's with combined cone area of 30", however, three 10's measure in at 930 cm2, and two 15's measure in at 1620 cm2, so in reality two 15's will have almost twice the cone area. Two 12's come in at 960 cm2, which beats out the three 10's marginally.

Also, there are many many variables to consider. Doubling the cone area on same power will give you 3dbs, doubling the Xmax will give you 6dbs, but potentializing on full Xmax will most likely require double the power, and higher Xmax subs are usually made less efficient by design, so they will need more power to get to that sweet point you want, but they will also keep going further, where the less efficient subs start to break up. Also, less efficient subs reproduce extreme lows(20hz - 40hz) with more authority, again by design. So it is all dependant on your goals.

Then there is power compression, where current heats up the voice coils in turn making them more resistant and less efficient, so that you start to waste/lose power. Two subs will share the load, and be more efficient that way. Acoustic coupling effect is another one, where you stack speakers in close proximity to each other, and everytime you double the cone area you gain anywhere from 3-6dbs(e.g. from one to two, from two to four subs).

Let's take JL audio subs for example, so that Yuli stays motivated on this long post and talk about SQ. Many people will allege that one superior sub will always render better results then two inferior ones. Again, depends on your goals, cause it is hard to be a jack of all traits, as where you need more sq you will lose spl and vice versa. Most people always look for a happy medium. A more or less fair comparison would be two 10" W6's and one 13.5" W7 in terms of cone area. Two different beasts to begin with and both have different goals in mind. One of the problems with making a sub that can handle more power is that inductance goes up due to more current, and as it goes up the end result is less usable frequency length, and the woofer loses "speed", so it becomes harder for the bigger woofer to reproduce transients etc. There are other factors as well, but this is such a huge discussion, I really dont want to get into it. I only want to have you realize that it is much more complex of a subject. So sq wise as in more correct reproduction of freqs, W6's will demolish W7, but the bigger woofer will demolish the smaller one as in how far you can push it. W6's have an advantage of being doubled up as they are sharing the power load, otherwise W7 will just eat one W6 for breakfast in terms of one to one output comparison. The smaller subs here will ger louder faster cause they are more efficient, but when you start pushing them beyong their mechanical limitations they start to break up. In this case, the W7 will go further without break up, as it is a sturdier design and will not show signs of fatigue that quickly, but more power will be required, but that is the exact point of a beefier sub. The advantage here is higher power handling without issues, but stronger or more spiders are required among other design changes, but with that comes higher moving mass etc, which sacrifices the efficiency...

I think this is enough for one post, but this could go on forever, as to give you better understanding, you need to know a lot more, and with a lot more info, more factors to consider will creep up, which need to be addressed as well, and this becomes a neverending domino effect. I hope this clears up a few things for you.

People with good knowledge of this type of stuff, this is not my intent to start a long debate, as I have not gotten into it deep enough for you, and just kept it very simple, so dont jump on me arguing cause I may have not explained everything in detail, and/or you may have misunderstood something. My intent was to keep it brief more or less to pass on the basic info. You all know that there are too many variables and this is just the tip of the iceberg. Cheers!

Father Yuli

iTrader: (17)

wow Sasha doing it eastern european style with the centimeters.

what Sasha says is right, not all subs are made equal. So quality and design of a driver matters.

But with equal subs, more cone = louder.

When I went with more cone and less power at the same time I used same subs in both applications. 2 12's vs. 3 10's. TFOne's ofcourse.

2 12's with 7,500 RMS vs. 3 10's with 6,200 RMS - the 3 10's were louder.

Just Sasha said in his post - it is all about driver efficiency vs. power handling. It is a spectrum and you have to know where on that spectrum you need (SQ vs SPL) or want (SQ or SPL or Daily Pound) to be.

Father Yuli

iTrader: (17)

I should mention, just like for any physics or mathematical theories to work, some conditions must be met.

We have already established one - same power at all times.

Another one is that all and each of the comparable drivers must be getting their rated RMS power or more.

If subs we are talking about arent getting their RMS wattage then this theory might not hold and more cone won't neccessarily be louder, even if power is the same.

Sasha

iTrader: (10)

Yuli is always a fountain of spl knowledge

I agree with the "conditions factor". One being power delivery and power production and it is a very important factor.

Yuli says he got more output out of three 10"s on less power. Actually, three 10's measure at 930 cm2, and two 12's are at 960 cms, so two 12's have more cone area. However, what may be happening is a perfect example of power compression and coupling effect. Three subs sharing the load vs two, so three will be more efficient in power compression factor. And three subs over two will have an approximate 1.5db gain in terms of coupling effect. So these may explain the output gains. Enclosure size is another factor, cause perhaps the 10's were "happier" in their designated boxes than the 12's in theirs. Like I said the list of conditions /factors/variables can go on all day. Also, I am refering mostly to "groundpounder" and SQ subs, SPL subs are completely different in design in terms of goals and application, but laws of physics still remain unchanged.

godzilla1978

We also should establish if the o.p. is talking about measureably louder or something you can hear. 1.5 Db is enough to measure on a mic but is not loud enough for most people's ear. You would need about 3Db to hear the differance.