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Topic:
speaker sensitivity???
This thread has 66 replies. Displaying posts 1 through 15.
Post 1 made on Monday April 10, 2000 at 04:30
adi soffer
Historic Forum Post
can anyone explain the relations between the "speaker sensitivity" (for example 90db...) and the amp used to drive it?
please dont answer in general (the lower the value the higher the efficiancy...) but rather get technical.


OP | Post 2 made on Monday April 10, 2000 at 19:20
Danny Owens
Historic Forum Post
Adi,

Most speakers are rated in db per watt per meter. In other words if a speaker is delevered 1 watt or power it will generate sound pressure that is (in your example) 90 db at 1 meter. Some speakers are rated at db=watts/2.83volts. If you do the math for 8 ohms, power = voltage squared divided by impedence. (2.83^2)/8 = 1. So you see that the watts per meter rating is the same as the watts per 2.83 volts at 8 ohms. Of course the higher the sensitivity, the more effecient the speaker.
Danny
OP | Post 3 made on Monday April 10, 2000 at 19:31
Danny OWens
Historic Forum Post
Adi,
I sent the previous message without fully reading your request. So continuing on, what the rating basicly means is that the higher the db per meter rating, the less power you will need to achive the same sound pressure at the same distance. However, power curves are nonlinear. For every 3 db increase in sound pressure you need twice the amp power to drive it. Using an example of comparison of 2 different pairs of speakers. One rated at 87 db and one rated at 90 db. To generate a sound pressure level 90db, you need only half of the power that you would need for the 87 db speakers to achive the same sound pressure level ie 90db.
Clear as mud?? Let me know if you need further clarification.
OP | Post 4 made on Monday April 10, 2000 at 19:52
Jeff
Historic Forum Post
Hi adi. Speaker sensitivity is a standardized measurement used to describe how much sound pressure will be generated by a speaker under specific circumstances. The standard requires that the speaker be driven by 1 watt of power with a calibrated microphone placed 1 meter in front of the system, both of which are placed in an anechoic chamber to eliminate the effect of "room gain". A speaker's sensitivity, then, is a function of its efficiency; how much do you get out for how much you put in. Most speakers are highly inefficient, on the order of 1% or so. To illustrate, an experiment was done a number of years ago. The acoustic wattage (figured in dynes per square centimeter) of a concert tympani was measured at 28 aw. With the average speakers efficiency, it would require 2800 watts of amp power (and enough speakers to handle it all) to duplicate the original power of the tympani. You can see, then, how important a speaker's sensitivity rating becomes if you are considering an amp purchase. The more efficient the speaker is, the more sound pressure you'll get for a given wattage input. However, don't get hung up on sensitivity. Most speaker will range from 86db to 91db; not a big difference. (It is generally accepted that the smallest perceivable change in volume in the average ear is equal to about 1db, with 3db being what happens when someone says "Turn it up a little bit") I think you would be happier with a speaker that sounds better to you with a lower sensitivity rating than one that was more efficient but less pleasing to your ear. Also, consider this often overlooked fact: doubling the volume (a 10db increase) does not require twice the power... it requires 10 times the power! So, if you are listening at an average of 2 watts and double the volume, it requires 20 watts; an 18 watt increase. Double it again, and it requires 200 watts; a 180 watt increase. You can do the math from there and easily see why a 100 watt amp is one of the most useless products ever created. So, yes, sensitvity is important, but not all-encompassing. Use your ears; the salesman is not going to be listening to your speakers, you will. Hope this helps. Luck...Jeff
OP | Post 5 made on Monday April 10, 2000 at 20:08
jeff
Historic Forum Post
Hi, adi, its me again. I need to correct something I said in the previous missive. I said a doubling of the volume is equivalent to 10db. This is incorrect; Danny used the correct figure of 3db. It still applies that 3db is what occurs when someone turns it up a little; because our hearing is logarithmic, larger and larger changes in volume are required for us to perceive a difference. Strange but true, a sound measuring 120db is 12,000,000,000,000 times louder than one you can barely hear, so if your ever tempted to tell a friend that your system plays a million times louder than his, you probably on safe ground! Luck...Jeff
OP | Post 6 made on Monday April 10, 2000 at 20:28
Danny Owens
Historic Forum Post
Adi;
I think Jeff must be some kind of amplifier salesman or something. According to his calculations, an auditorium sized venue would require more power than the entire east coast grid would supply. In the pro-audio business (which I have been an engineer for more than 2 decades), it is a common fact that a 3db increase in sound pressure requires twice the power. If you can get 100 db with 50 watts, it takes 100 watts to get 103 db. It's a basic law of logs. As far as speaker effiency not being an issue, that is an incredibly ridiculous statement. I've included a link that should clarify the relationship between speaker effiency and power requirements.
Danny

[Link: smr-home-theatre.org]
OP | Post 7 made on Wednesday April 12, 2000 at 18:01
Jeff
Historic Forum Post
Hi, adi. Let this be the moral of the story: never answer e-mail on Monday! I must again correct something I told you. My original statement that a doubling of volume is represented by a 10db increase was correct. I got a little confused after reading Danny's reply and went off the trail...
At any rate, Danny has sent a valuable link. If you read the section entitled "How much power do I need", you will find verification of the claims I made; specifically that a doubling of volume requires ten times the power. You may also want to visit Cinepro.com. I also hope that I did not give the impression that I don't think sensitivity is important; after re-reading my reply, I didn't really see anything that suggested that. I just don't see it as a litmus test. Luck...Jeff
OP | Post 8 made on Wednesday April 12, 2000 at 23:59
Gerald Koth
Historic Forum Post
Just a little bit of info. A 100 watt amplifier will give you 20 db more than the sensitivity of the speaker. So if you start out with say 80 at 1 watt you will get 100 db at 100 watts at 1 meter. They used to rate amplifiers with those figures in the 80's. A live rock concert is from 110 to 120 db. I could achieve those kinds of sound pressure levels with my Altec lansing voice of the theaters (106 db at 1 wat 1 meter) and my 90 watt SAE amplifier (19 db) 106 plus 19 = 125. LOUD. Most speaker amplifier pairs today will not play LOUD.
Post 9 made on Monday May 8, 2006 at 04:49
Audio God
Lurking Member
Joined:
Posts:
May 2006
8
A mixture of fact with fable. Danny Owens has the most facts:

"For every 3 db increase in sound pressure you need twice the amp power to drive it."

"It is a common fact that a 3db increase in sound pressure requires twice the power. If you can get 100 db with 50 watts, it takes 100 watts to get 103 db."

Sensitivity is how efficent the speaker is at turning the amplifiers power into sound. A speaker rated at +3 db more than another will require only half the power to produce the same output.

paraphrased from www.pioneerelectronics.com

90 db at 1 watt at 1 meter
93 db at 2 watt at 1 meter
96 db at 4 watt at 1 meter
99 db at 8 watt at 1 meter
102 db at 16 watt at 1 meter
105 db at 32 watt at 1 meter
108 db at 64 watt at 1 meter
111 db at 128 watt at 1 meter
114 db at 256 watt at 1 meter
117 db at 512 watt at 1 meter
120 db at 1024 watt at 1 meter

now compair

99 db at 1 watt at 1 meter
102 db at 2 watt at 1 meter
105 db at 4 watt at 1 meter
108 db at 8 watt at 1 meter
111 db at 16 watt at 1 meter
114 db at 32 watt at 1 meter
117 db at 64 watt at 1 meter
120 db at 128 watt at 1 meter
123 db at 256 watt at 1 meter
126 db at 512 watt at 1 meter
129 db at 1024 watt at 1 meter

A speaker with a db rating of 90 db at 1 watt at 1 meter will put out 120db of volume at 1 meter at the cost of 1024 watts.

A speaker with a db rating of 99 db at 1 watt at 1 meter will put out 120db of volume at 1 meter at the cost of 128 watts.

However some of the loudest speakers have what is concidered low sensitivity
for example the Pioneer Premier TS-W5000SPL 12 inch sub that shattered records and won a Deathmatch championship at the 2004 dB Drag Racing World Finals. (car audio) the sub can exceed 170+ dB. and yet the Sensitivity is 88dB.

Danny please correct me if I am wrong.

and no i'm not a Pioneer rep I'm just an audiophile.

Last edited by Audio God on May 9, 2006 11:06.
Post 10 made on Monday May 8, 2006 at 07:05
RICHNWB
Long Time Member
Joined:
Posts:
December 2004
384
Good info..Only 6 years late...
Never eat on a empty stomach!
Post 11 made on Sunday May 28, 2006 at 21:25
Ernie Bornn-Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
30,104
Audio God,
I will try to be nice about this.

If a thread has not had any posts for six years, the issue has probably been solved to the satisfaction of all.

Resurrecting such an old thread makes those of us who post here quite often see an interesting "new" title, where we think we can learn something new or add something to the discussion. Then we see that the issue must have been resolved or there would have been at least a good five years more back-and-forth, and we think you are an idiot for wasting our time.

If you would like to sample some of the vitriol heaped upon different members who have done this in the past, look up most of the posts by G50AE, from whom we have not heard for at least two years, and Mr. Stanley, who did this for a short while before turning into a quite interesting and helpful member of the present, instead of mining the past for irrelevancies.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 12 made on Monday May 29, 2006 at 01:52
Tom Ciaramitaro
Loyal Member
Joined:
Posts:
May 2002
7,958
Ernie, you are really on tonight. Don't go to sleep without slapping down a few more classic retorts.
There is no truth anymore. Only assertions. The internet world has no interest in truth, only vindication for preconceived assumptions.
Post 13 made on Wednesday May 31, 2006 at 16:19
Trunk-Slammer -Supreme
Loyal Member
Joined:
Posts:
November 2003
7,454
I had some VERY sensitve speakers a few years back.

But I had to get rid of them as they kept breaking down every time the wife watched As The World Turns......

Puddles of slightly saline water all around them....Just ruint the dang floor......
Post 14 made on Thursday June 1, 2006 at 12:43
Audio God
Lurking Member
Joined:
Posts:
May 2006
8
As you can see I am a new member and simply did not notice the date of the original post. However this is not an apology for “wasting your time” nor do I feel like an idiot for teaching you something. The previous posts concerning speaker sensitivity were very poorly explained. As I read them I felt bad about anyone coming to this site seeking answers to valid questions and leaving confused with their questions unanswered.

As for this from a founding member: “Ernie, you are really on tonight. Don't go to sleep without slapping down a few more classic retorts.”

The sad thing is that at this site apparently Super Members and Founding Members such as Ernie Bornn-Gilman and Tom Ciaramitaro did not add something to the discussion and did not answer this question any better than the other previous attempts.

Instead they sat around and talked shit about other posts instead of helping people and let posts with crappy answers linger on their site confusing possibly thousands of people over the past 73 months. Maybe someone should look back into old posts and give closure to the other questions that also had poor explanations.

As for Advanced Member Trunk-Slammer –Supreme, maybe you should read the post instead of simply commenting on the title. This practice would improve your maturity and your intellect. You would learn something and hopefully take speaker sensitivity into consideration when you upgrade your system. Otherwise your system will look like a bitch when I pull up next to you.

Instead of crying about how I wasted your time you should be grateful that I enlightened you and graced your site with my presence.
Post 15 made on Thursday June 1, 2006 at 13:18
floyd_1977
Long Time Member
Joined:
Posts:
October 2004
75
"Otherwise your system will look like a bitch when I pull up next to you."

Note: this is a *home* theater forum.
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