# Volume Question

Discussion in 'Amps and Cabs [BG]' started by Gabu, Feb 28, 2002.

1. ### Gabu

Jan 2, 2001
Lake Elsinore, CA
For those of you who know that math...

How much louder would

2 15" speakers + 2 12" speakers at 700 watts

be than

2 15" speakers at 1000 watts.

Assuming sensetivity was the same (say 100db).

Thanks!!

2. ### Gabu

Jan 2, 2001
Lake Elsinore, CA
Oops... Correction!

Make that 600 watts for the 2 12s + 2 15s

and 1000 watts still for the 2 15s alone.

Thanks!!

3. ### Aaron

Jun 2, 2001
Bellingham, WA
same resistance?

4. ### Gabu

Jan 2, 2001
Lake Elsinore, CA
All the speakers are 8 ohms.

The 2 15" speakers would be wired in parallel for a total of 4 ohms, and 4 ohms bridged on this amp would produce 1000 watts.

The 2 15s + 2 12s would be wired in parallel pairs (one 15 and one 12 each) for a total load of 4 ohms each side, 300 watts per side. Although this choice is technically stereo, both sides would be reproducing the exact same stuff.

5. ### camoe

Sep 7, 2001
Lafayette, CO
Need more info. Is that 1000 watts rms or peak?Also 1000 watts for one amp may not produce the same volume as another because of the current demands. Watts=voltage*current. Some amps produce a greater amount of current, some voltage. All speakers have an impedance curve (a resistance to the current) that varies according to the frequency (very diverse at low freq) and these curves can be radically different. With the changes in impedance, thereby changes in current draw, the 1000W amp may choke up at various points compared to another 1000W amp dependent upon the design. To make a long explanation even longer, we could easily apply mathematic formulas to guesstimate loudness vs. efficiency of speaker vs. current draw...etc. but it would really be a vauge guess as the variables of speakers and amp designs make it impossible (without know the exact specifications) to calculate. Whoa..now I'm confused...what was your question... The other factor to consider is that one choice may be louder up to a certain point, but may puke out quicker than the other (akin to the torque vs. horsepower). The final thing to consider is just because one is louder at let's say 5 watts, does not mean the tone is better either. In my previous life, I reviewed many subwoofers (audiophile grade) and found little corelation between speaker efficiency and watts, just too many variables. My advice is just listen yourself and let your ears be the judge.

Peace

6. ### Gabu

Jan 2, 2001
Lake Elsinore, CA

In my example we are talking about 1000 real watts going into a system of speakers. This is a question of math, not a question of actual gear.

We are talking about one amp, this same amp produces 1000 watts bridged at 4 ohms or 300 wats per side at 4 ohms. Since it is the same amp in each comparison, there are no issues about how honest the company's ratings are, or any of the other various issues.

This is exactly what I am asking for.

I have included enough information for a exact answer. All I need is someone who knows the math formulae to plug in the variables. This is not a question including what the termperature is and at this elevation, with a piece of scotch tape inhibiting one of the 12s... etc etc... It's just a math problem.

Thanks for your answer. I understand what you are saying.... But I don't think you understood what I am saying.

In a nutshell compare the volume of:

two 15" speakers at 100db sensetivity played at 1000 watts.

or

two sets of one 15" speaker paired with one 12" speaker at 100db sensetivity played at 300 watts for each pair.

That's all, no specific gear, no real ears, no hump in the 200 hz range.... just what you see.

7. ### geshel

Oct 2, 2001
Seattle
With a 100dB sensitivity, the 2x15 @ 1000w would produce 130dB (100 + 10log(1000)). Not that you could (or would want to) do that for long. That'd be a lot of headroom.

With the 2x15 and the 2x12, hmm. . .this is a bit of a grey area but combined the total sensitivity would be a bit higher, maybe 2dB (added driver area / coupling, whatever you call it, that's about what it turns out to be). So the max volume would "only" be about 129dB (102 + 10log(600)) - not really any different.

A hunch tells me the 4-speaker setup would "sound" louder. No math to back that up though.

8. ### Gabu

Jan 2, 2001
Lake Elsinore, CA
Thanks for your information. Using your formula, the difference between 600 watts and 1000 watts into the just the 15" speakers is roughly 130 vs 128. Tacking on the other two speakers adds only 1db.

So is there a relationship between speaker area and apparent volume, if sensetivity remains constant?

9. ### nil

Apr 6, 2000
Auckland, New Zealand
DAMN STRAIGHT! Replace a 4x10 with an 8x10 and the volume difference is very apparent.

10. ### HeavyDutySupporting CurmudgeonStaff MemberGold Supporting Member

Jun 26, 2000
Suburban Chicago, IL
11. ### fast slapper

Dec 11, 2001
Fresno, CA
Easy,2x12+2x15.More speaker,more volume.(most of the time) But there are many different variables that could make my statement false. 600 and 1,000 watts isn't to much of a difference.

12. ### Gabu

Jan 2, 2001
Lake Elsinore, CA
Thanks everyone.

You are all awesome.

13. ### geshel

Oct 2, 2001
Seattle
Yep, 600 watts adds 27.8dB to the 1w output, 1000w adds 30dB.

Actually, adding two 12s to two 15s will probably add more like 2dB than just 1. Either way, not much but about the same as the difference in power anyway. (wracks brain. . .actually I seem to remember being almost convinced that doubling the speaker area, at the same power, adds between 3 and 6dB.

Some handy rules of thumb for dB:

2x power -> add 3dB (3.01)
3x -> 5dB (4.77)
4x -> 6dB (6.02)
5x -> 7dB (6.99)
10x -> 10dB (exactly)

Glad to be of service, hope that helps.