3 db - 10 db increase [ explained ]

[Oliver]

I'll probably be reprimanded for wasting space, I still feel this is a very "basic" thing that is not understood by some

excerpt]

100W
200W = +3dB
400W = +6dB
800W = +9db
1000W = +10db (10 times the original power of 100 watts)

Link with chart on scale for decibels

http://www.metrokc.gov/ddes/lusd/gb/...3/3-7Noise.pdf

[Electrodynamic]

Good post. I think the kids over on ca.com, caf.com, etc could use this.

[89grand]

No offense, but I thought most of us already knew that. Maybe not.

[6APPEAL]

Follows the guideline I was told years ago (can't remember who told me ). To gain 3db you would have to double cone area or power. And only doubling one over and over would give diminishing returns with each double.
John

[buchaja]

This is why I don't understand those who want to push 200 watts to their tweeters. Using OP's chart and modifying it for use with say a tweeter of 93db efficiency:

1W = +0db = 93db
2W = +3db = 96db
4W = +6db = 99 db
8W = +9db = 102db
10W = +10db = 105 db

Now tell me, isn't 105db loud?

[Abmolech]

Babies scream clocked 127 dB, so 105 dB isn't that loud.

Point 127 dB won't damage your hearing, although it might damage your sleep.

[HondAudio]

Originally Posted by Abmolech

Babies scream clocked 127 dB, so 105 dB isn't that loud.

Point 127 dB won't damage your hearing, although it might damage your sleep.

127 dB WILL damage your hearing, especially at the high frequencies a tweeter is capable of reproducing. Without getting too technical, compare 127 dB at 8 khz vs. 80 Hz. Your eardrum would be subject to the same force but at a way higher frequency.

[Abmolech]

So what pitch do you imagine a baby to scream at?

[Tommythecat]

If evolution had its way - a babies scream could be most at about 3k, where our ears are most sensitive.

[FoxPro5]

Don't know about you guys, but 3k in my car is blasting right into the side of my leg!!!!!! So 2000 watts on my tweeters sounds just about right!

Tell'm 'bout baffles, abmolech.

[Abmolech]

Anecdotal factoid.

All sirens are based on a babies scream.
It is a sound we find difficult to ignore.

Home stereo against a crying baby... which one will win?

The smart money is on the baby.

[HIS4]

Easiest way to explain it is in mathematical terms.

Amplitude of the sound wave = 10 * log (base 10) x.

So as you increase x, the amplitude increases by a logarithmic value expressed in dB. Assuming x=1 for simplicity, in order for the amplitude to increase by 3, x has to double. In order for amplitude to increase by 10, x has to multiply by 10.

[thylantyr]

Originally Posted by buchaja

This is why I don't understand those who want to push 200 watts to their tweeters. Using OP's chart and modifying it for use with say a tweeter of 93db efficiency:

1W = +0db = 93db
2W = +3db = 96db
4W = +6db = 99 db
8W = +9db = 102db
10W = +10db = 105 db

Now tell me, isn't 105db loud?

Edit.

Keep going......

16W = 105dB
32W = 108dB
64W = 111dB
128W = 114dB
256W = 117dB
512W = 120dB
1024W = 123dB

Lets stop here and think. Questions need to be asked.

1. What is the tweeters maximum SPL ? Can it really
do 123dB clean assuming it can handle 1kw?

2. What is the power handing of the tweeter?

3. What is the listening distance? Those sensitivity
ratings are 1 meter. SPL will drop off 6dB per doubling
of distance.

4. What is loud? 100dB, 105dB, 110dB ? hehehe

Lets say that 93dB rated tweeter is 64w rms and
you do indeed get 111dB of SPL at 1 meter. What if
you listen to the audio system at 3 meters? You have
to factor distance and recalculate the SPL. At 2 meters,
you may be at 111dB - 6dB, at 3 meters, -6dB, you
are now back to a meager 99dB SPL.

Next question, why connect a tweeter to a high powered
amplifier? Even of the tweeter only needed 64W, there is
a very good chance that you have weak headroom for
transients. See chart, Crest Factor.

http://www.audioheritage.org/html/pe...s/1-intro.html

People don't factor this in, they only look at watt ratings.
They assume amplifiers have unlimited headroom when
in reality they are very limited as opposed to a real
music instrument like a drum strike.

[thylantyr]

Originally Posted by 6APPEAL

Follows the guideline I was told years ago (can't remember who told me ). To gain 3db you would have to double cone area or power. And only doubling one over and over would give diminishing returns with each double.
John

The simple math is;

10log(number of drivers) = mutual coupling gain

10log(single driver impedance/total impedance) = electrical gain.

Two woofers;

10log(2) = 3dB gain because you added a second woofer.

If you wired the second woofer in parallel and assuming
each woofer is 4 ohms.

10(4/2) = 3dB gain.

There is potential to have 6dB gain when you add a second
woofer. But there is some fine print to understand before
this works.

a. The second woofer needs the same power level as the first to realize the gain. If the first woofer is driven by 100w, the second woofer needs 100w too. if not, less or no gain here.

b. The drivers need to follow the 'line array' rules for
good coupling. In other words, the second woofer
if placed 1 mile away from the first woofer, don't expect
any reward.

This is how rockford fosgate 'amazed the natives' at CES a while back
when they introduced the T15KW amplifier. They had 60 woofers playing.
Think about it.

[Abmolech]

Come on thylandyr, your not suggesting we require array's, waveguide's or horn's in a car, with power amplifiers that can produce the necessary wattage?

We have been "testing" car audio in driveways/parking lots for years, how could they be so wrong?

Could it be that with 70 -80 dB noise floor (highway driving) that these systems are not adequate to the task?

[~thematt~]

Some people are making some HUGE assumptions.

Sensitivity numbers are made free air. Who mounts their speakers free air? Therefore, are the numbers you're delivering actually realistic?

Also, in the world of reflections, we're dealing with more then one source. Keep in mind a reflection produces the same response as another speaker located on the other side of the reflective surface. Wave interaction. Nulls and peaks.

One speaker at a point = 105dB.
That same speaker at that same point with a reflective surface placed there so that the point is a peak = 108dB
Two reflective surfaces at that point, in the peak = 111dB.
etc. etc.

Not to mention the whole waveguide/steradian issue.....

[Abmolech]

True, however sensitivity is rated at 2 PI steradians.

IE not 4 PI Steradians (free air)

[Oliver]

Thank you gentlemen , one and all !

I could single each and everyone out for their contributions, perhaps as a group is the best way to enjoy this , though IMHO

Thanx ! for an awe inspiring read

[buchaja]

OK, let's keep this going a little longer. I'm trying to learn all I can about this hobby.

I just purchased a pair of BG Neo3 tweeters from a fellow member. While I await their arrival, I'm looking over the pdf another member provided me with. (Thanks to Mark and Andres -- this is a great group here!)

So back on topic; the Neo3 has a sensitivity (efficiency?) of 96db/watt. So the output list looks 3db higher for this tweeter:

1 watt = 96db
2 watts = 99db
4 watts = 102db
8 watts = 105db
16 watts = 108db
32 watts = 111db

I'll stop here and add that the nominal power recommended from BG is 10 watts rms, 20 music (program) and 50 watts peak.

So the question remains, do you really need anything bigger than a 50 watt power supply for an average tweeter? In a car?

[Abmolech]

Depends on sensitivity, steradians loading and distance to the listener.

In the vast majority of cases 50 watts at the drivers nominal impedance rating should be sufficient.

[sqshoestring]

I really hate distortion in tweeters, and the tweeters hate it too. So I like to have a buffer of power there to stay away from it. Also amps seem to work differently in cars....though maybe none of you run mid/low priced amps. Some amps will play clean and even smaller ones can go really loud on the high side with no bass, while others usually not as good will distort no matter what and do it slowly....I hate that. It is not excessive input or lack of power supply. I like a good 75wrms/ch, but have a 40/ch that performs really nicely too.

Oh yeah, I was on another site and a guy was saying a 400w amp made 200w at half volume...

[Oliver]