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mixsit
12-05-2005, 12:31 AM
I'm trying to get a few basics straight, and this seems like a good place to ask.

I have read that at some SP level, the air in a horn throat can distort. Does this happen (even if only on transients on un-compressed signals) at or near the 'loud end' of studio monitoring? (Let's say just to get in the ballpark loud is 100db spl on the average scale and peaks are +8 or 10 above.)

Second-..

Does driver efficiency have an effect on the relative dynamics of the output sound pressure level? This would assume that the systems, a high efficiency and a lower in comparison are both operating within their linear range (not being drive into 'power compression', if that is the applicable term).
I think the answer is no, but would like to be sure, and comes from hearing people say some system might sound 'more dynamic' than others.
And last, it has been said that a cone design may have an edge (potentially?) in the accuracy department over horns.
(It's new studio monitor time.:D
Thanks in advance.
Wayne Smith

Robh3606
12-05-2005, 04:40 AM
For one you need to look in the JBL tech library.

http://www.jblpro.com/pub/technote/tn_v1n21.pdf

Might help.

On the second I think the High Efficiency system has the edge all the time. Doesn't matter if they are both in their linear ranges.

On Three After reading the first reference that may not be true with more modern designs.

Rob:)

whizzer
12-06-2005, 09:56 AM
Efficiency and dynamic range are inextricably intertwined. "Dynamic range" is the term used to describe the difference between the softest audible sound and the loudest. Many types of live music exhibit an actual dynamic range of 20+ decibels, a range of approximately 128:1, while many so-called "audiophile" loudspeaker systems are so inefficient that their rated SPL is in the 85-86 decibel range, measured on axis at meter with a one-watt input of pink noise. A 3 decibel increase in perceived output requires an increase of 10X amplifier power, so raising the inefficient system's output 3 dB to 88 dB requires 10 watts, and raising it to 91 dB requires 100 watts, and to 94, 1000 watts. Unfortunately, although many speakers can "take" that kind of input, they simply convert the electricity to heat. The actual dynamic range of such systems is, if we're feeling generous, 9 dB. In order to reproduce the actual dynamic range of real music, a speaker system must be very efficient indeed, and many horn systems have efficiency ratings approaching 75% as compared to the 3% or so characteristic of most "high end" audiophile systems. Compression distortion is a measure of quality rarely mentioned in "audiophile" equipment reviews, and for good reason, as many highly-touted systems have compresiion distortions of over 50%. Horn systems may present many practical problems, but high distortion is not a necessary part of what horns do.

As for the other part of your question, very narrow throats do not actually "distort" the air itself, which retains its molecular integrity, but the high velocities produced by large compression drivers pushed by excessive input signals may cause turbulence in constricted throats that serves the same purpose--physical distortion of the reproduced signal.

yggdrasil
12-06-2005, 01:15 PM
A 3 decibel increase in perceived output requires an increase of 10X amplifier power, so raising the inefficient system's output 3 dB to 88 dB requires 10 watts, and raising it to 91 dB requires 100 watts, and to 94, 1000 watts.
No.

A 3 dB increase requires 2x amplifier power. A 10 dB increase requires 10x amplifier power.

Raising output from 85dB to 95dB when the speaker has a sensitivity of 85dB requires 10 watts.

johnaec
12-06-2005, 01:59 PM
A 3 dB increase requires 2x amplifier power. A 10 dB increase requires 10x amplifier power.

Raising output from 85dB to 95dB when the speaker has a sensitivity of 85dB requires 10 watts.That's my understanding also. And in an open environment, every doubling of distance from the loudspeaker results in -6 dB, correct?

John

whizzer
12-06-2005, 02:04 PM
Let me clarify this. Insofar as pure electrical power levels are concerned, a 3 dB increase in power is a ratio of 2:1, however, for the hopefully undamaged human ear, a 3 dB increase in applied amplifier power is hardly audible. For a given sound to be perceived as "twice as loud," an acoustic increase of 3 dB (remember, dB are not absolute, but relative measures of power; an acoustic watt is a very large unit as compared to an electrical watt), a bare minimum of 10 times the amplifier power must be applied. The problem with inefficient speakers is that they soak up too much amplifier power just to attain a reasonable average level, leaving little amplifier headroom for cleanly reproducing the transients that give the music its characteristic "flavor." The more efficient the system, the wider its dynamic range. Psycho-acoustics deal with the complex interplay of human perception and the far more quantifiable realm of "physical" physics. The problem in the bass region is even more acute, which is why loudspeaker systems that measure harmonically flat across the range of human hearing produce an output that strikes most listeners as overly "bright," perhaps even "harsh," and that hardly ever bears a favorable comparison to the far more visceral experience of actual live music. Inefficient loudspeakers are simply physically incapable of faithfully reproducing the actual dynamic range of many types of live music, particularly rock and pop, but also including Baroque organ fugues and the like. Measure a system that produces 85-87 dB @ 1 watt @ 1 meter at a realistic listening distance in an auditorium-sized listening environment at its full rated input power and compare the experience of listening to it in that environment to a horn-loaded system rated at over 100 dB @ 1 watt @ 1 meter running along on only a few watts so as to allow plenty of clean amplifier power for transients 15-20 dB above the average level, and the differences will very soon become very apparent.

johnaec
12-06-2005, 02:13 PM
For a given sound to be perceived as "twice as loud," an acoustic increase of 3 dB (remember, dB are not absolute, but relative measures of power; an acoustic watt is a very large unit as compared to an electrical watt), a bare minimum of 10 times the amplifier power must be applied..I was always under the impression that for a sound to be perceived twice as loud it took an increase of 10 dB. I was also under the impression that same 10 dB requires 10 times the power. I fail to see how 10 times the power is required for a 3 dB increase in acoustic output.

John

Oldmics
12-06-2005, 02:13 PM
johnaec asks

"That's my understanding also. And in an open environment, every doubling of distance from the loudspeaker results in -6 dB, correct?"

Correct for SPHERICAL radiating enclosures.That would be the inverse square law.

Line array systems only lose 3db for the doubling of the distance generally speaking.

Oldmics

johnaec
12-06-2005, 02:16 PM
johnaec asks

"That's my understanding also. And in an open environment, every doubling of distance from the loudspeaker results in -6 dB, correct?"

Correct for SPHERICAL radiating enclosures.That would be the inverse square law.

Line array systems only lose 3db for the doubling of the distance generally speaking.

OldmicsThanks for clearing that up - that's good to know.

John

Tom Loizeaux
12-06-2005, 07:36 PM
I don't understand why you say speakers are limited in their ability to produce dynamic range. Any speaker/driver has a maximum output level...(before destruction), but they can play very softly before they reach the threshold of "not making any sound". That is dynamic range. I think speakers/drivers have a greater dynamic range then voice and most musical instruments!
Maybe I'm missing something, but I just don't get the limited dynamic rage mentioned in the thread.

Tom

B&KMan
12-06-2005, 08:13 PM
power amp rule...

3 db higer require= double real power amp. but subjectively 10 dB is require for you feel double power sound...


so :

if 86 dB at 1 m for 1 watts (ex)

89 @ 2 W
92 @ 4 W
95 @ 8 W
98 @ 16 W
101 @ 32 W
104 @ 64 W
107 @ 128 W
110 @ 256 W
113 @ 512 W
116 @ 1024W

note rms is a average... no peak to peak so add easely 6 db for correct peak to peak. the real formula result is the rms = 0.717 of 1.0 (peak)

unfortunaletly, by the nature of transient, the handle power amplifier run at max 1/3 of power requirement of the rule below for full impulse response.

so add 6 db for peak and multiplie by 3 for full dynamic range evaluation with no compression, no distortion...

my 2 cents commentary...

:cheers:


and in same in others reply;


the power sound the rule is calculate arround concept of intensity, and the power is drop 6 dB by double distance...


so finaly , re-calculate your power requirement in regard of this distance...


:cheers: :D

Ian Mackenzie
12-07-2005, 12:42 AM
I'm trying to get a few basics straight, and this seems like a good place to ask.

I have read that at some SP level, the air in a horn throat can distort. Does this happen (even if only on transients on un-compressed signals) at or near the 'loud end' of studio monitoring? (Let's say just to get in the ballpark loud is 100db spl on the average scale and peaks are +8 or 10 above.)

Second-..

Does driver efficiency have an effect on the relative dynamics of the output sound pressure level? This would assume that the systems, a high efficiency and a lower in comparison are both operating within their linear range (not being drive into 'power compression', if that is the applicable term).
I think the answer is no, but would like to be sure, and comes from hearing people say some system might sound 'more dynamic' than others.
And last, it has been said that a cone design may have an edge (potentially?) in the accuracy department over horns.
(It's new studio monitor time.:D
Thanks in advance.
Wayne Smith


Wayne,

Part one depends on a lot of variables inc the horn contour/flare rate.

Part two. In my opinion it does as more sensitive (this is the correct term for expressing driver output versus input voltage) systems tend to suffer less from power compression (when designed correctly) simple because less power is absorbed as heat in the voice coil.

The best way to improve on linear efficiency is horn loading or use of mutiple drivers or both. This is done in pro applications for precisely that reason.

However, correctly designed cone direct radiators can also be relatively sensitive (98- 100 db) with hi power handling and when used in arrays can become even more so.

Research by Passlabs suggests hi sensitivity cone drivers offer improve dynamics, particularly when used in a bi amplified or tri/quad amplifed system.
http://www.passlabs.com/downloads/rushmore_lit.pdf

whizzer
12-07-2005, 06:00 AM
This is true. As mentioned before, decibels are measures of relative power levels, so doubling the input power from 1 watt to 2 watts is a 3 dB increase, and so is the difference between 250 and 500 watts. However, doubling the input power does not double the acoustic energy produced by the loudspeaker. Adding a second identical system also receiving the same level of input signal would produce an actual doubling of energy--more in cases of acoustic coupling, as when assymetric folded horn mouths are arranged in mirror-imaged pairs. Simply applying a 3 dB increase in input power will not produce this magnitude of effect.
Nor are decibels absolute measures of sound level. John L. Murphy, of the True Audio Loudspeaker Design Center, states that if a loudspeaker were 100% efficient, an electrical input of 1 watt would produce an output of 1 acoustic watt, which, measured at 1 meter, would be 112.1 dB SPL (radiating into half space). The question ought to be, "112.1 dB above what?" The baseline level cannot be silence, for any multiple of no sound is still no sound. If we use the measurement of one loudspeaker's output that is produced by a 1 watt electrical input and, for instance, call it 85 dB, then how many times can we double the acoustic energy produced by that loudspeaker before it becomes burned out junk? If, on the other hand, if we measure the output of a system the same way, using the same equipment, and find a reading of 95 dB, we may double that acoustic energy perhaps the same number of times before destroying the transducer, but the ultimate output will be much greater. Now, obviously, either system will play softly enough to produce sounds that are barely audible, but the more efficient one will play far more loudly, thus its dynamic range is wider. Finally, listening to music at the same average level, the more efficient system with the wider dynamic range will, by allowing the amplifier greater reserves for reproducing transient peaks, simply sound "more dynamic."

Mr. Widget
12-07-2005, 10:12 AM
Finally, listening to music at the same average level, the more efficient system with the wider dynamic range will, by allowing the amplifier greater reserves for reproducing transient peaks, simply sound "more dynamic."I won't dispute this statement, but I am wondering if what we determine as "sounding more dynamic" isn't more correctly a freedom from power compression? Perhaps also in conjunction with a better transient response.

Typically high efficiency systems have low moving masses and have better transient response and since they aren't being driven as hard in a domestic environment, they typically don't heat up very much and therefore are inherently less prone to dynamic compression. Lately drivers being designed by JBL and others have been tackling dynamic compression head on and modern drivers have much less dynamic compression than previous models. The fact that an older design that was originally intended for theater use is barely being driven in a domestic situation makes it's susceptibility to dynamic compression much less apparent and therefore it's performance is seemingly more effortless.


Widget

whizzer
12-07-2005, 01:26 PM
[QUOTE=Mr. Widget] I am wondering if what we determine as "sounding more dynamic" isn't more correctly a freedom from power compression?


It certainly is. A mechanical and/or electrically-induced restriction of dynamic range is exactly what "power compression" is. While efficiency of a high order will allow a wider dynamic range by allowing for sufficient amplifier headroom, it by no means ensures it. The driver's motor assembly must be capable of controlling diaphragm movement in such a way as to cleanly and accurately respond to the signal and reproduce those transient responses. One knock against very efficient speakers has been that they don't sound so good at low levels, principally because they draw so little power, for it is at low output levels that transistorized amplifiers are at their worst. Old-style theater speakers truly sound better with low-power tube amps for this very reason. The effort made by JBL to preserve the old high-efficiency approach while using modern materials and design techniques for greater compatibility with modern amplifier technology has, indeed, resulted in lower levels of power compression than seen in many other modern drivers--many examples from Eminence spring readily to mind--but at the cost of some small decrease in ultimate dynamic range compared to earlier designs.

toddalin
12-07-2005, 03:02 PM
This is true. As mentioned before, decibels are measures of relative power levels, so doubling the input power from 1 watt to 2 watts is a 3 dB increase, and so is the difference between 250 and 500 watts. However, doubling the input power does not double the acoustic energy produced by the loudspeaker. Adding a second identical system also receiving the same level of input signal would produce an actual doubling of energy--more in cases of acoustic coupling, as when assymetric folded horn mouths are arranged in mirror-imaged pairs. Simply applying a 3 dB increase in input power will not produce this magnitude of effect.
Nor are decibels absolute measures of sound level. John L. Murphy, of the True Audio Loudspeaker Design Center, states that if a loudspeaker were 100% efficient, an electrical input of 1 watt would produce an output of 1 acoustic watt, which, measured at 1 meter, would be 112.1 dB SPL (radiating into half space). The question ought to be, "112.1 dB above what?" The baseline level cannot be silence, for any multiple of no sound is still no sound. If we use the measurement of one loudspeaker's output that is produced by a 1 watt electrical input and, for instance, call it 85 dB, then how many times can we double the acoustic energy produced by that loudspeaker before it becomes burned out junk? If, on the other hand, if we measure the output of a system the same way, using the same equipment, and find a reading of 95 dB, we may double that acoustic energy perhaps the same number of times before destroying the transducer, but the ultimate output will be much greater. Now, obviously, either system will play softly enough to produce sounds that are barely audible, but the more efficient one will play far more loudly, thus its dynamic range is wider. Finally, listening to music at the same average level, the more efficient system with the wider dynamic range will, by allowing the amplifier greater reserves for reproducing transient peaks, simply sound "more dynamic."

Have to disagree with you on a few levels. Whizzer

First off, as long as the speaker is operating within is linear excursion and electrical parameters, doubling the power will in fact double the cone excursion thereby moving twice the air mass raising the sound by 3 dB increase. Bringing in a second sound system may result in further increase if various room nodes are able to interact further increasing the wave amplitude. On the other hand, you could get cancellation reducing the amplitude.

Second, YES DECIBELS ARE AN ABSOLUTE MEASURE OF SOUND LEVEL. The dB scale does have a zero dB reference point of a pressure level of 20 micropascals per square meter. Therefore, 3 dB = 40 micropascals per square meter and 6 dB = 80 micropascals per square meter, etc.

"The question ought to be, "112.1 dB above what?"
BTW, 112.1 dB = 3.2436E12 micropascals per square meter. The equation is

10^(desired level in dB/10) x 20 micropascals/m^2

And, to answer your anticipated question, yes, thre can be values less than ZERO dB. For example 10 micropascals per square meter = -3 dB.

Mr. Widget
12-07-2005, 04:40 PM
First off, as long as the speaker is operating within is linear excursion and electrical parameters, doubling the power will in fact double the cone excursion thereby moving twice the air mass raising the sound by 3 dB increase.This is true at low power levels, but as the voice coil heats up the coil inductance and other parameters change so it isn't linear... I think this is what whizzer was getting at.


[QUOTE=Mr. Widget] A mechanical and/or electrically-induced restriction of dynamic range is exactly what "power compression" is.Sure... I guess what I was trying to say was that your earlier post seemed to imply that a sensitive speaker helped the amp loaf and therefore increased the system's dynamics... my point was that while true, I feel the loudspeaker's characteristics are more important. For example, a pair of AR3as being driven with a pair of kilowatt Mac mono blocks... That system still won't sound dynamic even though there is no shortage of amplifier headroom.

Widget

Akira
12-07-2005, 04:40 PM
Unless physics have changed since I was in engineering school...

double power = an increase of 3db
double power plus double speaker = an increase of 6db
preceived acoustical doubling is stated at 10db.

the definition of 1db is the smallest increase in SPL that the human ear can detect 50% of the time.
0db is the threshold of hearing that the human ear can detect 50% of the time

the speed of sound is xxxxx at sea level @ 70degrees :blah: CAN'T REMEMBER...I FLUNKED THAT PART OF THE COURSE!!!!

all quotes from Modern Recording Techniques, Robert E. Runstein (Recording Institute of America)

Mr. Widget
12-07-2005, 04:43 PM
Unless physics have changed since I was in engineering school...Still the same, but I think you'd agree that school is an idealized environment.:D

Widget

Akira
12-07-2005, 04:50 PM
Still the same, but I think you'd agree that school is an idealized environment.:D

Widget

Damn right. My education started when I left school and the 'industry' quickly showed me that I new nothing of the real world.
BUT I USED TO KNOW WHAT THE SPEED OF SOUND WAS!!!! :blink:

Earl K
12-07-2005, 05:00 PM
BUT I USED TO KNOW WHAT THE SPEED OF SOUND WAS!!!!

FWIW : I usually use 1130 ft per second . This figure works well enough in other equations . :D

:p

toddalin
12-07-2005, 06:07 PM
Damn right. My education started when I left school and the 'industry' quickly showed me that I new nothing of the real world.
BUT I USED TO KNOW WHAT THE SPEED OF SOUND WAS!!!! :blink:

1,116 feet per second at sea level.

BTW, 1,130 feet per second would put Toronto about 3,250 feet BELOW sea level.

whizzer
12-08-2005, 06:03 AM
First off, thanks to Mr. Widget for clarifying what I was trying to say. Sometimes teaching English just gets in the way. While it's true, at least in theory, that doubling the input power will result in moving twice the air mass, that's rarely actually true in the real world--not that it can't be, mind you--it's just rare that physical conditions are so ideal as to produce results that are identical with theory. I guess the real point is that a 3 dB increase in electrical input power is a far cry from a doubling of acoustic energy in that one watt of acoustic energy is measured as an output of 112.1 dB @ 1 meter on axis, which, in the real world, would, with most loudspeakers, require far more than a one watt input. That is, the energy measures are not 1-1 linear. Apparent "twice as loud" is not a simple 3 dB increase in input watts, but is a true doubling of output in terms of acoustic energy-- not in terms of theory, but in terms of human hearing. The purpose of the whole SPL-efficiency rating thing is to differentiate between the output of various drivers with a standard input. If System A produces a measurement of 85 dB with this input while System B produces 95 dB, then we know that system B does more with one watt than does System A, thus, it would seem to me that we have no reason to assume that System A will respond just as vigorously to a doubling of the input as System B, as it has already been shown to be less efficient at converting electrical energy to sound. If, for instance, in actuality, the rate of increase in the output falls as the input level increases, as in "power compression," then a simple formula of x dB in = x dB out becomes increasingly out of touch with physical reality.

On a related note, regardless of the dynamic capabilities of the driver itself, if there is not a sufficient reserve of amplifier power capable of reproducing transients 15-20 dB above the average content, then clipping and dynamic compression will be the result.

pangea
12-09-2005, 11:54 AM
First I wanted to tell you that today I was listening to one of Mike Oldfields CD's "Amarok" and although I must admit that I have set my Behringer Ultracurve to add a few dB of expander on the midbass section, I noticed the dynamic range on the CD spanned from 40dBC to 97dBC!!! Isn't that amazing?:D

Talk about dynamics!!! How many speakers other than JBL's do you think are up to the task???

One other thing I would like to ask, is why those yellow kevlar type of cones have become so popular.

I read this article from Passlab on the project Rushmore, where it said that many speaker driver manufacturer who really succeeded and excelled, were those who used their ears when choosing materials and designs and the best sounding cones were those made of paper, the article said.
So, why are there so many kevlar cones out there?

Is this also the main reason for JBL staying with paper cones?

EDIT: Follow up question if that IS the case. Why do paper cones sound better?

Anyone know?

BR
Roland

toddalin
12-09-2005, 12:09 PM
First I wanted to tell you that today I was listening to one of Mike Oldfields CD's "Amarok" and although I must admit that I have set my Behringer Ultracurve to add a few dB of expander on the midbass section, I noticed the dynamic range on the CD spanned from 40dBC to 97dBC!!! Isn't that amazing?:D

Talk about dynamics!!! How many speakers other than JBL's do you think are up to the task???

One other thing I would like to ask, is why those yellow kevlar type of cones have become so popular.

I read this article from Passlab on the project Rushmore, where it said that many speaker driver manufacturer who really succeeded and excelled, were those who used their ears when choosing materials and designs and the best sounding cones were those made of paper, the article said.
So, why are there so many kevlar cones out there?

Is this also the main reason for JBL staying with paper cones?

EDIT: Follow up question if that IS the case. Why do paper cones sound better?

Anyone know?

BR
Roland

What makes you think that JBL doesn't use kevlar in the paper cones???

W15GTI
15" Differential Drive® Design Subwoofer
If you are in search of the ultimate woofer, this is it! JBL has leveraged all engineering resources to develop quite simply the best subwoofer money can buy. Symmetrical Field Geometry ensures linear cone travel and low distortion at virtually any level by creating a uniform magnetic field around the coil. Die-Cast basket
• Suggested Retail Price: $699.00

• Differential Drive® Design (DDD) motor

• Die-cast vented basket

• Kevlar®-impregnated paper woofer cone

• Nitrile-butylene surround

• Power handling RMS: 800 watts

• Power handling Peak: 5,000 watts

• Mounting depth: 10-1/4"

• Cut-out diameter: 13-7/8"

• Dual 6-ohm voice coils

• Sensitivity: 92dB

pangea
12-09-2005, 12:20 PM
What makes you think that JBL doesn't use kevlar in the paper cones???

W15GTI
15" Differential Drive® Design Subwoofer
If you are in search of the ultimate woofer, this is it! JBL has leveraged all engineering resources to develop quite simply the best subwoofer money can buy. Symmetrical Field Geometry ensures linear cone travel and low distortion at virtually any level by creating a uniform magnetic field around the coil. Die-Cast basket
• Suggested Retail Price: $699.00

• Differential Drive® Design (DDD) motor

• Die-cast vented basket

• Kevlar®-impregnated paper woofer cone

• Nitrile-butylene surround

• Power handling RMS: 800 watts

• Power handling Peak: 5,000 watts

• Mounting depth: 10-1/4"

• Cut-out diameter: 13-7/8"

• Dual 6-ohm voice coils

• Sensitivity: 92dB



Yeah yeah, but those should hardly be counted, since they're mainly intended for car use, where they have to endure various weather conditions, am I right?

I was talking about sonic excellence here, or do they qualify in this respect too?

Besides, isn't the sensitivity a bit low?

Hmmm, dual voice coils, does that mean, you can parallel them if the amp can handle a 3 Ohm load, or that they can be coupled with a stereo signal to each coil?

BR
Roland

toddalin
12-09-2005, 12:48 PM
Yeah yeah, but those should hardly be counted, since they're mainly intended for car use, where they have to endure various weather conditions, am I right?

I was talking about sonic excellence here, or do they qualify in this respect too?

Besides, isn't the sensitivity a bit low?

Hmmm, dual voice coils, does that mean, you can parallel them if the amp can handle a 3 Ohm load, or that they can be coupled with a stereo signal to each coil?

BR
Roland

It would appear from other posts on this forum, that the W15GTI is similar to the new sub for pro use.

Hey, they're JBL! One would not expect anything less than sonic excellance regardless of the venue!

At 92 dB their are only 1 dB less efficient than the 2235, and way more efficient than an LE15.

To make the speaker work as designed, the coils MUST be wired in parallel or series and were not designed to be used coupled for stereo.

Mr. Widget
12-09-2005, 12:58 PM
At 92 dB their are only 1 dB less efficient than the 2235, and way more efficient than an LE15.The LE15 is a few dB more sensitive than the 2235....

Paper or plastic?
While plastic, kevlar, carbon fiber, etc. allow certain benefits, I have preferred the sonic quality of paper myself. Typically the doped, aquaplas coated, carbon or kevlar impregnated paper cones are also great, but there is just something about paper...


Widget

Alex Lancaster
12-09-2005, 01:10 PM
:) How about the hemp ones?

toddalin
12-09-2005, 02:21 PM
The LE15 is a few dB more sensitive than the 2235....

Paper or plastic?
While plastic, kevlar, carbon fiber, etc. allow certain benefits, I have preferred the sonic quality of paper myself. Typically the doped, aquaplas coated, carbon or kevlar impregnated paper cones are also great, but there is just something about paper...


Widget

Almost right. My catalog says LE15 does 45 dB SPL at 1 mW at 9.1 meters and when I do the calcs, it comes out to 94 dB at 1 meter. Like the 2235, the 136A comes in at 93 dB at 1 meter. But a 124A only comes in at 89 dB at a meter, so at 92 dB at 1 meter the W15GTI is still not bad!

I guess efficiency is the price you pay (at least in part) for that massive surround.

Mr. Widget
12-09-2005, 03:39 PM
Almost right. My catalog says LE15 does 45 dB SPL at 1 mW at 9.1 meters and when I do the calcs, it comes out to 94 dB at 1 meter. Like the 2235, the 136A comes in at 93 dB at 1 meter. But a 124A only comes in at 89 dB at a meter, so at 92 dB at 1 meter the W15GTI is still not bad!It's all pretty academic since variations from unit to unit along with your box tuning and frequency of interest will have a significant effect on the outcome of such a comparison. This is from a recent discussion:

http://www.audioheritage.org/vbulletin/showpost.php?p=78931&postcount=10

Widget

mixsit
12-19-2005, 11:55 PM
Forgive me for dragging this up again after such a lapse. I read through the responses, and more than a few times came back.. remaining confused. But (if it's not too late.. ) perhaps I have found a way through, or at least a more specific way to frame the question.


This is true. As mentioned before, decibels are measures of relative power levels, so doubling the input power from 1 watt to 2 watts is a 3 dB increase, and so is the difference between 250 and 500 watts.

If this statement, if I recall correctly, works for inefficient and efficient drivers, then it would seem to make a case for relative sound pressure being independent of efficiency.

And so in a effort to strip away (if possible) the other issues that were brought into discussion ('which will play the loudest, 'which might sound more dynamic due to better transient, or less compression for example), what if; Our same two systems, sine waves for each at one watt input, then again at 2 watts.

(To pull some made-up driver numbers) does one go from 88 to 91 dB, another from 100 to 103?

Or maybe it would be just as fun to talk about the new monitors I'm going to be trying out. :D
Either way, wishing a merry Christmass everyone.:)
Wayne Smith

Mr. Widget
12-20-2005, 12:04 AM
And so in a effort to strip away (if possible) the other issues that were brought into discussion ('which will play the loudest, 'which might sound more dynamic due to better transient, or less compression for example), what if; Our same two systems, sine waves for each at one watt input, then again at 2 watts.

(To pull some made-up driver numbers) does one go from 88 to 91 dB, another from 100 to 103?Yes.

However you will more likely listen to both at about the same SPL so in system A you would go from 1 watt to 2 watts and in system B you would go from 63mW to 125mW. It is very likely that system B will sound more dynamic since it will heat up significantly less at 125mW than system A will with 2 watts.

...and Merry Christmas to you to!

Widget

mixsit
12-20-2005, 12:26 AM
But (assuming that all to impossible 'all other things being egual:) ) don't both coils see that heat of double the power?
Or unless the more efficient one spends a smaller percentage as heat...
Wayne

Mr. Widget
12-20-2005, 12:58 AM
But (assuming that all to impossible 'all other things being egual:) ) don't both coils see that heat of double the power?This is where the physics of reality gets more complicated than the simplified ideal as used in a school lab to explain different scenarios.



Or unless the more efficient one spends a smaller percentage as heat...This would explain part of it, but basically most lower sensitivity drivers heat up and loose dynamics. There are some that vent the heat well and can absorb great amounts of power and remain dynamic... these are rare.


Widget

jkc
12-20-2005, 05:12 AM
It is interesting this dB stuff and is perhaps worth a little more explanation.



Once upon a time someone sat down and said how do you measure noise.

They figured out that that the ear is non linear and perceives sound in a logarithmic manner.

1 dB is considered as the smallest change you can hear on a solid state tone

3 dB is considered the smallest change you can hear on music

10 dB is considered as twice as loud.



Now it is a mathematical anomaly that for a speaker to sound twice as loud it needs 10 x the power.

So to make that 100 watt stereo sound twice as loud you need1 Kilowatt.

But this is only part of the story.

Music consists of a whole lot of peaks but the average power can be very low with a whole lot of peaks that need lots of power.

So if we assume a bass transient is driving the amplifier output +ve at the same time as a cymbal crash (HF) is also going +ve our peak requirement can become very high

Lets say we are using 1/10 of watt and need a 40 dB peak that’s 1Kw. (Actually its not but we need the voltage and instant current capacity that only a 1 Kw amp has)

Now the worst thing you can do is let a solid state amp clip, horrible things happen.

The real world is not quite like this as this signal has been “processed” before it’s recorded, one of the things that’s happened is it’s been compressed and all the peaks chopped of so they don’t overload every thing.

We just have to hope the recording engineer used a nice sounding compressor.

But the idea of a big amp to cope with peaks is a valid one that makes a difference.



Now it gets a bit more interesting, speakers are not very efficient things and most of the energy you pump into them gets converted into heat.

When was the last time you removed a working light bulb? Hot wasn’t it.

Same thing happens in a speaker voice coil.



Now when you heat up a voice coil lots of nasty things happen this referred to as power compression.



Now a 3 dB of power compression means that when you double your amp power nothing happens the speaker won’t get louder it just gets hotter.



Does power compression matter? Yes I believe it does.

Recently I was playing with some 2220’s, quite a nice speaker; I was using an H version which has a big ferrite magnet. When you turned it up it just went flat and lifeless.

It so happened that I changed to an A version which has a smaller Alnico magnet.

It went flat and lifeless sooner, less heat sinking more power compression.

I replaced them with a pair of 2227’s which is what 2220,s evolved into.

The result you turn it up and it just gets louder, why? Because these are JBL’s super vented gap transducers capable of dissipating heaps of heat.

Here are the power compression figures for 2227”s



60 watts 0.5 dB

300watts 1.7 dB

600 watts 3.2 dB (rated Power)

Exceptionally good numbers.

And they are 100 dB at watt at 1 meter much the same as a 2220



So what happens when I drive an inefficient speaker, say 80 dB at 1 watt/1meter

That’s 20 dB more grunt I need, instead of 1 watt I need a 100 watts and that’s a lot of heat.

And that means power compression and is a good an explanation as any as to why an inefficient speaker sounds dull flat and lifeless because when you turn it up it stops getting louder and just gets hotter, and it happens a lot faster than you think.
And you need another 20dB out of that amp.

By nature a low efficiency speaker will have a large magnetic gap and the voice coil just can’t radiate away the heat.

This is one of the reasons that high efficiency systems sound better, you can turn them up more before lots of nasty things start happening.



http://www.jblpro.com/pub/technote/tn_v1n18.pd






Quote from http://sound.westhost.com/lr-passive.htm#3.3

“3.3 Temperature
In case you were wondering, the voice coil temperature used in the examples below (150°C) is not as outrageous as it may seem. Since loudspeakers have an efficiency of typically 1% or less, this means that 99% of all the power going to the speaker must be dissipated as heat. Although there is some air movement through the voice coil gap, it cannot keep the temperature down low enough to ensure that the effects described will not disturb the behaviour of the crossover network. An efficiency of 1% indicates just over 92dB/m/W, which is quite a respectable figure in the world of loudspeakers!

Copper has a thermal coefficient of resistance such that its resistance increases by 0.395% per °C (variously listed as anything from 0.39% to 0.43% on different websites). We can safely assume that the impedance is based on "room temperature", which will generally be in the order of 20°C. When power (in the form of music or test signals) is applied to a speaker, the voice coil temperature must rise. Given a typical 6.6 ohm (DC) voice coil for an 8 ohm nominal speaker, at 150°C, the resistive component alone will rise to 10 ohms - and naturally the impedance must be somewhat greater than this figure.”

yggdrasil
12-20-2005, 08:40 AM
Given a typical 6.6 ohm (DC) voice coil for an 8 ohm nominal speaker, at 150°C, the resistive component alone will rise to 10 ohms - and naturally the impedance must be somewhat greater than this figure.”
And this does lots of bad things to a passive crossover...

Zilch
12-20-2005, 10:14 AM
Let's not immediately presume this is of any major consequence at typical home listening levels.

The voice coil temperature is at equilibrium with the average power and the thermal dissipation capabilities of the motor.

When a transient comes through, the temperature rise is not instantaneous, as the voice coil, unlike the above cited light bulb filament, has thermal mass, apart from the dissipation path. Additional power compression does not come into play significantly on transients.

How hot does my woofer's voice coil actually get when I'm listening at 90 dB average from 4 M away, which is pretty damn loud?

Well, hotter, of course, when playing an inefficient driver, but enough so to compress the dynamics of the program.

Mr. Widget
12-20-2005, 10:22 AM
Let's not immediately presume this is of any major consequence at typical home listening levels.Let's do! I believe it is one of the reasons that many of us like horns even though they are typically not as neutral as conventional speakers.

The subtleties the ear can discern are really amazing. I believe the lack of even very small amounts of dynamic compression adds to our sense of transient response and a sense the music is alive.


Widget

toddalin
12-20-2005, 11:10 AM
Let's not immediately presume this is of any major consequence at typical home listening levels.

The voice coil temperature is at equilibrium with the average power and the thermal dissipation capabilities of the motor.

When a transient comes through, the temperature rise is not instantaneous, as the voice coil, unlike the above cited light bulb filament, has thermal mass, apart from the dissipation path. Additional power compression does not come into play significantly on transients.

How hot does my woofer's voice coil actually get when I'm listening at 90 dB average from 4 M away, which is pretty damn loud?

Well, hotter, of course, when playing an inefficient driver, but enough so to compress the dynamics of the program.

The instructions that come with the W15GTI address power compression as a result of temperature in reference to voice coil impedience as well as volume level for use in sound level competition.

pangea
12-20-2005, 11:14 AM
Let's do! I believe it is one of the reasons that many of us like horns even though they are typically not as neutral as conventional speakers.

The subtleties the ear can discern are really amazing. I believe the lack of even very small amounts of dynamic compression adds to our sense of transient response and a sense the music is alive.


Widget

It simply has to do something with transients, when taking one quite hefty Yamaha amp (260W + 260W) for my 2235's and then adding a new dimension to the listening experience, when bridging two of them, so that each bass driver is controlled by 800W, while still listening at normal SPL's.

BR
Roland

Zilch
12-20-2005, 11:18 AM
It simply has to do something with transients, when taking one quite hefty Yamaha amp (260W + 260W) for my 2235's and then adding a new dimension to the listening experience, when bridging two of them, so that each bass driver is controlled by 800W, while still listening at normal SPL's.Well, yes, you still have to be able to deliver them, as required by the program....


The instructions that come with the W15GTI address power compression as a result of temperature in reference to voice coil impedience as well as volume level for use in sound level competition.Yup, equilibrium occurs at a higher SPL with VGC and other thermal dissipation measures. There's more "buffer" to transients, as well, but my point is that's not of consequence at normal home listening levels. It matters to SR guys, too, of course, who are working closer to the operating limits of the drivers.


Let's do! I believe it is one of the reasons that many of us like horns even though they are typically not as neutral as conventional speakers.I believe we can agree that has more to do with diaphragm mass than dynamic power compression, however.

Mr. Widget
12-20-2005, 11:35 AM
I believe we can agree that has more to do with diaphragm mass than dynamic power compression, however.Not sure we can... check this out.

http://www.adireaudio.com/Files/TechPapers/WooferSpeed.pdf

Widget

pangea
12-20-2005, 11:37 AM
Well, yes, you still have to be able to deliver them, as required by the program....



Do you by program, mean the music that's on the record or CD?

I've got several CD's, where the dynamic range varies from just above 40dBC to over 100dBC, with all the transients I could ever dream of present, so, I don't think the speakers will fall short, in that respect.

BR
Roland

Mr. Widget
12-20-2005, 11:41 AM
Roland,

It's just that Zilch has been listening to pink noise too long.:rotfl:


Widget

pangea
12-20-2005, 12:02 PM
Roland,

It's just that Zilch has been listening to pink noise too long.:rotfl:


Widget

OK, I think I've got it.

Many thanks BTW for that paper on woofer speed. VERY interesting!!! I'll try to remember that and save the file.

BR
Roland

speakerdave
12-20-2005, 12:43 PM
Not sure we can... check this out.

http://www.adireaudio.com/Files/TechPapers/WooferSpeed.pdf

Widget

A couple of questions from the techNOT about this paper.

One: In inductors current lags voltage, so increased inductance will discharge more slowly. But the question about woofer speed does not regard comparisons of inductances. Also, I think adding inductance outside the magnetic gap may have a different effect from adding it in the gap. I would need to think more about exactly what the difference might be.

Two: The way the math is managed the argument is foreclosed. He calls m a constant, but it is different sizes of this factor that he should be comparing. Given the same strength in the motor and the same current from the amp, if m is increased a must be less. Heavier cones will be slower unless the motor strength is increased. The difference between the JBL D131 and 124 is a good example of this truism.

Three: His charts contradict his argument. The peaks in the red and blue lines occur at the same time, but the red peaks (increased mass) are lower, meaning that the cone has travelled a shorter distance in the same time; reason: it is slower.

David

Edit: Oops. No, I got my colors mixed up. Hang on.

Edit 2: On the first half cycle the raw and mass-added curves are the same. On the second the mass-added curve goes FURTHER, suggesting the suspension is struggling to control the momentum. On the "ringing" cycles the mass-added curve does begin to lag the the raw curve.

If the effect of adding mass does not change the initial response (according to the test data), and the BL and current are the same, it can only mean one thing, and that is that the change in mass is trivial for the given BL product and suspension effects, and the test setup is not sensitive enough to pick up the effects of the added mass on the first half-cycle.

Additional hedging: The comparison of the D131 and 124 assumes that they both have the same voice coil depth. Of course, they may not.

Edit 3: If the additional inductance were to be added within the magnetic gap, i.e.. by increasing the voice coil depth, then that would increase the BL product, tending to increase acceleration, not decrease. The effects of the additional BL and the added inductance, would tend to offset. Whether it would be direct and complete I don't know.

Then there's the added back emf which would result from the increased coil windings. The effects of that I can't picture.

Zilch
12-20-2005, 12:53 PM
***Zilch slaps Mr. Widget with a red herring....***


:p

Mr. Widget
12-20-2005, 12:58 PM
A couple of questions from the techNOT about this paper.I have to admit I only glanced at it.... I did a quick google about BL vs. transient response and this popped up. I do agree with their premise, but can't vouch for their argument.;)



***Zilch slaps Mr. Widget with a red herring....***You keep that kinky stuff at home.:blink:

Widget

B&KMan
12-20-2005, 04:52 PM
You keep that kinky stuff at home.:blink:
Widget


oh oh oh jingle bell ROck...


hi transient spanking with a full power velocity movement heres...

your engine play bang!! dang !! pang!! or tang ??? :p

:band:

B&KMan
12-20-2005, 05:25 PM
A couple of questions from the techNOT about this paper..

My 2 cents here is :

the electrical impedance is critical factor for fast transient and clear fundamental response.


Krell have 12 of damping factor in amp and few crown have over 5000 damping factor. few amp (specific for live session) have over 10 000 damping factor. for complete depredation control (if you "spanking" the mic, the monitor survival)...

my experience is the damping affect impedance => and consequenly the transient:

less damping play more harmonical responses but you drop smash transient.

inverse situation... too heavy damping: the driver is "over" tight smash but you lost the harmonics...

equilibrium is one of part of signature sound: the match of

amp- cable- driver affect direcly the balance of acoustics transient and harmonics response ...



in general really high factor electrical and pneumatic factor affect transient. load with event port, etc, etc,


in theorical the lightnest and rigid surface as possible with the small motion as possible garantee the fastest response and re-position for next impulse without external control...


:cheers:

Oldmics
12-20-2005, 05:36 PM
B+KMan quote

"Krell have 12 of damping factor in amp and crowm over 5000 damping factor. few amp specific for live session is over 10 000 damping factor."

At what frequencys was the damping factor specified?

Something to consider in woofer applications.

Oldmics

B&KMan
12-20-2005, 05:54 PM
B+KMan quote

"Krell have 12 of damping factor in amp and crowm over 5000 damping factor. few amp specific for live session is over 10 000 damping factor."

At what frequencys was the damping factor specified?

Something to consider in woofer applications.

Oldmics



mmmmmmmm this is a another story....


many cie' print spec. in non accordance conformity to IEC , EIA, ISO, ANSI, standart...


but in general the load impedance (8 ohms ex) and frequency is specified at serious cie'.

normally 8 ohms and arround 50 Hz is good range...


:cheers:

Oldmics
12-20-2005, 06:07 PM
Quote from B+KMan

"normally 8 ohms and arround 50 Hz is good range..."

Agreed,however find me anyplace Crown lists its damping with this spec in mind.

Oldmics

B&KMan
12-20-2005, 08:34 PM
Agreed,however find me anyplace Crown lists its damping with this spec in mind.
Oldmics

As you wish...

:D

B&KMan
12-20-2005, 08:46 PM
B+KMan quote

"Krell have 12 of damping factor in amp and crowm over 5000 damping factor. few amp specific for live session is over 10 000 damping factor."

At what frequencys was the damping factor specified?

Something to consider in woofer applications.

Oldmics


the rule is more damping more stiff but less harmonics. is you go in real sub below 40 or 30 HZ the higher damping the better smashing... because the harmonics is poor at this area, keep higher reasonnably...

the non official rule is over 500 damping is consider very higner snap and image is terreffic and is for application mixing with more accurate space position sound in image sound on record session.

over 1000 is for live for control displacement of diaghram for not convert it to rocket when the guy is drop the mic of over pressure displacement on diaghram mic...


:cheers:

Oldmics
12-20-2005, 09:21 PM
Pull up the same page on your goggle search.You will see a pro sound website discussion regarding damping.

http://web1.prosoundweb.com/community/read.php?board=2&id=143800

The gentlemen who wrote the article is one of QSC designs engineers.While I don"t always agree with his beliefs,Bob Lee is a respected and well versed professional in the field.

Basically he is saying that damping factor is marketing hype.

He gives an example regarding a hypothetical damping factor of 124 (basically 20 feet of 12 gauge copper wire and a vaporware amplifier with an impossible to achieve damping factor spec of infinity)

So how hard is it to achieve a damping factor of 400 @ 10hz? (Which is a shit spec factor!)

Answer-Not very difficult.

Damping factors are bullshit salesman dialogue.:bs: :bs:

Although you did find the specs together-I did get a good laugh out of that! :applaud:

If your gonna critique amps,I would look at the storage capacity in the power supplys and see if they are overspec (as they should be-Crowns are not!) and if so by how much in comparision to rated wattage output.

Oldmics-Where the hells that PSS guy when you need a laugh?

B&KMan
12-20-2005, 09:59 PM
many cie' print spec. in non accordance conformity to IEC , EIA, ISO, ANSI, standart...
:cheers:

if guys is not refer at a standart, maybe is print anything as wish.

I agree this factor and many other factor is a real real propaganda....


but this fact is not cancel the reality of the bucle of conter-reaction control resistance on amp circuit... and the effect on the sound result...

the damping factor is the trick for balance equilibrium on one side fundamental transient and propagation of the harmonics.... and each cie expose theories and who have a best point of view...

anyway,

thanks for link.... I check because I have a good experience of the phenomenon but not strong scientific comprehension of the phenomenon.

:cheers:

frank23
12-21-2005, 01:26 PM
If your gonna critique amps,I would look at the storage capacity in the power supplys and see if they are overspec (as they should be-Crowns are not!) and if so by how much in comparision to rated wattage output.

Yes, that is one of the reasons why I think my class-A amps sound so good. They are full class A, so they dissipate 4 times the rated output at any time they are on. Even when there is no signal at all.

My 2*12Watt MF David class-A amp takes up about 100Watt's all the time its on, so the power supply is designed for that load, while in practise it only has to deliver a few Watts.

Don't even get started with thinking about this ratio for single-ended-mosfet-amps though!

frank

B&KMan
12-21-2005, 02:03 PM
Yes, that is one of the reasons why I think my class-A amps sound so good. They are full class A, so they dissipate 4 times the rated output at any time they are on. Even when there is no signal at all.

My 2*12Watt MF David class-A amp takes up about 100Watt's all the time its on, so the power supply is designed for that load, while in practise it only has to deliver a few Watts.

Don't even get started with thinking about this ratio for single-ended-mosfet-amps though!

frank

well because the full class A built a full reserve power all the time so is convert just for replenish the level... the great advantage is time delay cancel and better phase.

any style of amp the perfect admisibility of full transient impulse
is possible only is rms is fixed at 1/3 of the full power rated...

i have listen superbe pure class A accuphase A-50 (monster bigger than Krell) I listen mark levinson, Krell, and few other pure class a and if you respect the rule of max 1/3 power rms handling all is never shrink sound.


but the damping factor change considerably the presentation of response and equilibrium of fundamental and harmonics proportion.

shure many cie is print full or partial bullshit but the reality of control damping factor is here. many flavor amp is demernining by this aspect.... in regard of the interaction of the rest of the link with speaker....


my 2 cents experience.

DualTriode
10-24-2018, 09:16 AM
Hello,

I just searched the WWW looking for information on horn distortion and came across this thread. I am surprised with the misunderstanding of dB’s.

Even if this is from years ago here goes.

dB=20*Log10()

If the power input to the speaker is X 1:
dB=20*Log10(1) = 0dB change

If the power input to the speaker X 2:
dB=20*Log10(2) = 6.02dB change

If the power input to the speaker is X 4:
dB=20*Log10(4) = 12.04dB change

If the power input to the speaker is X 8:
dB=20*Log10(8) = 18.06dB change

If the power input to the speaker is X 16:
dB=20*Log10(16) = 24.08dB change

For each doubling of the power input there is a 6dB increase in the output. I do not remember where this 3dB delta misconception came from.

grumpy
10-24-2018, 09:30 AM
So, 20log(Vout/Vin) works, but it’s 10log(Pout/Pin).

...has to do with power being a function of V squared.


http://www.arrl.org/files/file/Instructor%20resources/A%20Tutorial%20on%20the%20Dec-N0AX.pdf (http://www.arrl.org/files/file/Instructor%20resources/A%20Tutorial%20on%20the%20Dec-N0AX.pdf)

Robh3606
10-24-2018, 10:06 AM
There is no misconception we are talking power not volts. Take a look at table in the reference Grump posted. With speakers not worried about voltages more about power into the load/speaker

Rob:)