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[W. Mark Hellinger]

Admittedly:

1)  +3dB is twice the power, and:
2)  +10dB is perceived as twice as loud, but:

Twice as much PA is generally perceived as "bigger" (even if the delivered SPL is about the same).

Oftentimes, a winning strategy is to strive for performances to come across as "bigger than life".  Sound, lights, props, stage presence all contribute to this.  PA gear can be some of the cheapest and most readily accessible props.  It all depends on the motif you're trying to achieve.  Rarely is gross amounts of SPL a major selling point in a show, but a lot of cone drivers tickled sounds "bigger" than fewer cone drivers straining their guts out.  And impressive rack & stacks generally look like a serious show.

[dave stojan]

Mario Salazar wrote on Thu, 01 March 2007 22:22

Quoted fromthe Yamaha Sound Reinforcement Handbook "It turns out that a sound which is 3 dB higher than another is barely perceived to be louder;"   Accordingly, I don't think I will be paying much more to provide power that will only be perceived as very slightly louder.

If you search the LAB archives you'll find the Yamaha Handbook has been pointed out incorrect on this particular subject. Think about it - if 3db is barely noticeable how would 10db sound twice as loud? Got a mixer? Move the fader 3db & listen to the difference. Oh, and that extra power your saving money on just might be the difference in clipping & blowing your speakers or not. Yeah, the diminishing returns kick in early and get worse on the way up, but things take what they take and like thermodynamics, you never get away cheap. And don't believe everything you read.  

[drewgandy]

Mario Salazar wrote on Thu, 01 March 2007 16:22

OK, Accordingly, I don't think I will be paying much more to provide power that will only be perceived as very slightly louder. Thanks for the responses guys! It was, as always, greatly appreciated. Best Regards, Mario

A good look at the equal loudness contours might be in order.  If you look at the lines in the bass you'll find that they are quite close together.  I interpret this to mean that in the lower freqs it doesn't take as big a difference to appear to be much louder.  This seems to correlate with my experience with subs.  Often the difference between one sub and 2 is only really 6db but the change in perceived impact is really significant.  I wonder if the non-hearing physical sensations are more linear in perception.  

[Bruce Gering]

While 3dB may not be very noticeble in terms of overall loudness to the average listener, 3db more headroom in a system will certainly be noticed for it's improved clarity. I'll take the added headroom.

[Mario Salazar]

That was something I was considering, the headroom.  So maybe it is worth it. I don't know. I know that I will never hit the reds on the amps because my limiter is set up to stop this.  I know my gain structure well and know how far to go on the main fader.  The limiter just catches transients that may cause fast cliping. I have checked out the difference with my mixer and the yammy book seems correct.  While I can notice a difference at 1 db, there is only a slight difference at 3 db.  At 6 db I notice a significant change and at 10 db it does sound twice as loud.  Maybe I will save and search for a plx1802 here and there and buy them when I can.  I know I can use the 3402 for another two monitor mixes for my sm122s.  I am just scared that the power consumption might be a problem in smaller sound venues where their power supply is questionable.  I am still trying to learn the basics of power distros.  If I could figure this out and get one I would have less worries.
Thanks!

[Miguel Castro Rios]

The 3 db question. . .  


You got to think, '' 3 db, at what frequency?''

While you may think this is not very important, try moving the eq at 4k by +/-3 db.- Now try it at 250 hz.

The reason why a bigger PA sounds BIGGER, it's because the drivers are not being pushed as hard as a smaller PA, making the sound cleaner. So If you only gain 3db with twice the speakers, you got to think, you are not ONLY gaining 3 db, BUT 3 NICE db's..- if that makes any sense.

Now what to some people may seem as 10 db twice as LOUD, to some one else may be only 6db. Yes it's psychological, and depends how much hearing loss you've had over the years. Majority rules, if 10 db is it, then let it be!

[Elliot Thompson]

The easiest way I've narrowed it down, is using amplifier power.

All measured @ 1 Khz, 0.1 % THD


250 Watts @ 8 ohms

500 Watts @ 8 ohms

800 Watts @ 8 ohms

1000 Watts @ 8 ohms

Going from 250 to 500 will yield a 3 dB gain

Going from 250 to 1000 will yield a 6 db gain

Going from 500 to 800 will yield a 2 dB gain

Going from 500 to 1000 will yield a 3 dB gain


I generally go no lower than 3 dBs when upgrading amplifiers. While 2 dB is noticable, it's generally not worth the money invested in the upgrade. I think many don't understand you really need to focus on the difference under 3 dB which, may not be the object behind upgrading from a 500 watt amplifer to a 800 watt amplifier.

Pretty much like comparing a QSC PLX 3002 versus a PLX 3402.
Bridging both amplifiers @ 4 ohms yields a 0.5 dB gain in favor of the 3402. You won't hear a difference, at 0.5 dB gain.

Best Regards,

[Brad Weber]

dave stojan wrote on Thu, 01 March 2007 20:57

If you search the LAB archives you'll find the Yamaha Handbook has been pointed out incorrect on this particular subject. Think about it - if 3db is barely noticeable how would 10db sound twice as loud?

Then just about every other respected audio and acoustics text and reference must also be wrong.

You have to keep in mind that what is being addressed is perceived changes in loudness due to changes in sound levels, not signal levels.  Human hearing is not linear in frequency or level nor in the perception of several other factors, thus perceived loudness becomes very complex where absolute level, frequency content, tonal components and duration among other factors can affect the perceived loudness.  So assessing changes in loudness is quite different than addressing absolute voltage or power level changes.  I think that trying to consider a big picture that can encompass voltage levels, electrical and sound power levels, sound pressure levels and loudness levels quite understandably confuses many people.

For one thing dB numbers, such as dB Sound Pressure Levels or dBV and dBu, are ratios derived by referencing one number to another reference number, the term "dB" by itself is actually meaningless without some reference value.  Conversely, loudness is actually measured in absolute units of phons and sones rather than in dB units.  But more importantly, what is actually being related to the effect on loudness is not a change in the voltage or electrical signal level but rather a change in acoustical Sound Pressure Levels (SPL).  Trying to relate a specific change in a fader level directly to a change in perceived loudness is not really a valid relationship as there are numerous factors that can keep this from being a direct, much less linear, relationship.

What is generally stated is that all else being the same, a change in Sound Pressure Level of 3dBSPL is perceived as a readily noticeable change in loudness, while a 10dBSPL change in level is perceived as a halving or doubling in loudness.  I think that this generalization is usually applied in the context of trying to create the same signal, only louder or softer, and in that sense it is valid.  If there are differences in the frequency content, duration, etc. fo the acoustical signal then this generalization certainly may not be true, but I think that is somewhat beyond the issue at hand.

[dave stojan]

Brad Weber wrote on Fri, 02 March 2007 19:19

What is generally stated is that all else being the same, a change in Sound Pressure Level of 3dBSPL is perceived as a readily noticeable change in loudness, while a 10dBSPL change in level is perceived as a halving or doubling in loudness.  I think that this generalization is usually applied in the context of trying to create the same signal, only louder or softer, and in that sense it is valid.  If there are differences in the frequency content, duration, etc. fo the acoustical signal then this generalization certainly may not be true, but I think that is somewhat beyond the issue at hand.

Thank you for agreeing with me  

[John Roberts {JR}]

I believe this may have already been mentioned but the Bel was a very specific power measurement unrelated to anything subjective or perceived. The decibel (1/10 Bel) came into popular use because it was considered a convenient incremental value.

Correlation between 1 or several dB and perceived loudness changes are somewhat listener or program specific. These approximate relationships are useful when sizing systems but not very precise.

I have a great deal of difficulty visualizing or hypothesizing loudness as something I can assign proportionate values to. "Um does that sound 20% louder or 25%?" But that may just be a personal problem as many apparently form such opinions without much difficulty. Perhaps it's easier if you use a large quantum (i.e. twice as loud). But if you can't quantify smaller ratios, how precise can you be about the larger?  Whatever.

JR

PS: Perhaps for use with modern electronic instrumentation a centi-Bel might be useful.