Speaker efficiency vs sensitivity - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

Old 06-15-10, 01:09 PM Thread Starter
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Ice10

Join Date: Apr 2007
Posts: 335
Re: Speaker efficiency vs sensitivity

Quote:
When two quantities are related by single-valued mathematical relationships, they can be used interchangably.
So then in the real world these relationships have zero merit ? Is that what you are suggesting ? Also, based on what the EE said, is that correct ? Because if not, I want to kick his .

Speakers aren't perfectly linear devices with perfect impedance curves. So if one says that efficiency and sensitivity correlates in mathematical terms based on a set variable then that doesn't mean it correlates in the real world with multiple changing variables does it ? If you increase sensitivity that is no guarantee of increasing efficiency. That's what I'm trying to get across. It's like using room mode calculators using code designed to work in rectangular rooms but leaves out all other room shapes.

So what I'm saying is that one can't use the terms efficiency and sensitivity interchangeably in real world terms because there are variables at play. If you play around with 1 variable then you could probably make a case for the terms having a connection in mathematics, but in reality, impedance changes, on and off-axis dispersions I believe also have a role to play etc..etc. Efficiency is just a maths equation that leaves out a bunch of other variables. So if that is true, then it's really useless to us in the real world ?

Last edited by Doctor X; 06-15-10 at 01:22 PM.
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Old 06-15-10, 01:37 PM
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Anthony

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Re: Speaker efficiency vs sensitivity

I think the real problem is that there is no "standard" in the industry.

Case and point is my Magnepan speakers. They are listed as 86dB@2.83V/1m So you are thinking, oh, they only need twice the power of my 89dB speakers I'm replacing for the same volume. Wrong! You need 4x the power, because those 89dB speakers were 8Ω and the Maggies were 4Ω. Just a case of marketing, b/c 83dB@1W/1m doesn't look too good

And I wouldn't say they are useless. You just need to make sure you know what stat you are reading and if they just say "90dB efficient" you know they aren't giving you all the stats.
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Old 06-15-10, 02:15 PM Thread Starter
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Ice10

Join Date: Apr 2007
Posts: 335
Re: Speaker efficiency vs sensitivity

Just to bring in more info since I've recently been talking to an individual that actually designs transducers, he said that only time sensitivity and efficiency can be used interchangeably is when the driver acts as a point source which you can never have in a system that uses physically separated drivers to produce different frequency ranges.
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Old 06-18-10, 01:06 PM
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fbov

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Re: Speaker efficiency vs sensitivity

Quote:
Vaughan100 wrote: View Post
So then in the real world these relationships have zero merit ? ... Efficiency is just a maths equation that leaves out a bunch of other variables. So if that is true, then it's really useless to us in the real world ?
If "efficiency" is the ratio of the input (electrical) power to the output (acoustic) power, how does it differ from something expressed as dB/watt? (Remember, dB are measure of acoustic power and watts, electrical power). They are the same concept. I don't have a problem with that. Those who are technically competent in the field will use the metric that suits their needs.

One reason no one talks in terms of speaker efficiency is that the efficiency is so incredibly low. My MTMs are 93.3dB@2.83V@1m sensitivity, but only 0.56% efficient (no the decimal point is not misplaced). It's also hard to translate acoustic watts to hearing sensation, while dB has that built in. Anything that's expressed in terms of "dB/power@distance" can be expressed in efficiency. You may be confused because efficiency is usually expressed as a total, but the function that's integrated contains all the stuff you claim is missing.

I'm also going to make the wilda\$\$ guess that you're not an engineer... my money's on law, if only by the way you argue.

Have fun,
Frank

PS Actually, there is one thing that's not in efficiency - distance. Efficiency looks at the power transfer, only. Sound perception varies by the distance initially, then the distance squared. Efficiency integrates over the full 4pi space, so distance doesn't matter. Different metric for different applications

PPS all drivers are point sources at wavelengths that are long compared with the size of the radiating surface. Look at any on-axis vs off-axis FR curves and you can tell where the drivers cross by the points where the on-and off-axis curves coincide.
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Old 06-22-10, 06:59 AM Thread Starter
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Ice10

Join Date: Apr 2007
Posts: 335
Re: Speaker efficiency vs sensitivity

Quote:
fbov wrote:
I'm also going to make the wild guess that you're not an engineer... my money's on law, if only by the way you argue.
Have you been keeping tabs on me ? Interesting that you would assume I am a officer of the law as I don't believe I've flexed my argumentation muscles at all here and certainly haven't provided sufficient evidence in support of that allegation. : ) Unless you are referring to other forums, like AVSforum.

No, not all all, I'm no engineer but I find these subjects fascinating. I work within the AV industry. I have learned something new from a transducer engineer though. Sensitivity concerns itself with axial sensitivity (on-axis) and efficiency concerns itself with power out, at all angles.

I still think it's misleading to call a more sensitive speaker efficient, or vice-versa, as the efficiency metric could be influenced by a number of things. Just as sensitivity could be influenced by dispersion, power compression, frequency response etc. He told me that in the perfect world, with a perfect speaker, efficiency and sensitivity would scale perfectly, but obviously speakers aren't linear devices. Well, linear, up to a point anyway.

So, I'm curious where you read my posts from. Do tell...

PS I just noticed you covered the 4pi and on-axis/off-axis comments. Thanks.

Last edited by Doctor X; 06-22-10 at 07:08 AM.
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Old 06-22-10, 09:59 AM
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fbov

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Re: Speaker efficiency vs sensitivity

My comments were mainly due to a tendency to reduce to complex issues to black and white, and a reliance on information from others rather than your own understanding. To my knowledge, this is the only thread where we've interacted. And I do appreicate your kind reply.

I'm also one to try to find the commonality in things, the basic principles that govern matter. In that sense, sensitivity and efficiency are the same concept. At the same time, I know that specialized metric are very valuable, and thus see why speaker designers talk in terms of sensitivity.

When trying to understand a complex system, I find it useful to think like the smallest unit available, in this case electrons. They flow in a coil, creating a magnetic field. That field interacts with the motor magnet causing the coil to move (electrons interact with the motor magnet, too). The coil transmits the force to the cone which moves air. Now, start speeding things up from the initial DC thought process to one where the coil's oscillating, faster and faster as frequency increases through coil resonance and to the point where things are happening so fast that "extras" start to appear, reflections and resonances in the mechanical system... and that's just what's happening on the driver, much less the air around it.

Mental models aren't easy, but they gave us Quantum Mechanics, so they have their applications. To be honest, this is how I try to think about all physical systems...

Frank
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Old 06-22-10, 01:12 PM Thread Starter
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Ice10

Join Date: Apr 2007
Posts: 335
Re: Speaker efficiency vs sensitivity

Quote:
fbov wrote:
My comments were mainly due to a tendency to reduce to complex issues to black and white, and a reliance on information from others rather than your own understanding. To my knowledge, this is the only thread where we've interacted. And I do appreicate your kind reply.
No problem. I'm usually very passive in these kinds of discussions because on one hand I believe my understanding isn't too far off but I'm bouncing ideas on top of everyone else, so I try not to be overly assertive. Sometimes I just need reassurance that I'm on the right track.

Speaking of the right track, the transducer engineer who gave me a helping hand posts on Audioholics and due to his field is probably the most qualified when speaking on this subject. One of my problems is that I tend to over-analyze very quickly which leads me to asking the same questions over and over again.
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Old 06-23-10, 03:41 PM
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lsiberian

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Re: Speaker efficiency vs sensitivity

Quote:
Vaughan100 wrote: View Post
No problem. I'm usually very passive in these kinds of discussions because on one hand I believe my understanding isn't too far off but I'm bouncing ideas on top of everyone else, so I try not to be overly assertive. Sometimes I just need reassurance that I'm on the right track.

Speaking of the right track, the transducer engineer who gave me a helping hand posts on Audioholics and due to his field is probably the most qualified when speaking on this subject. One of my problems is that I tend to over-analyze very quickly which leads me to asking the same questions over and over again.
I don't know of this transducer engineer he must be keeping his identity secret. Nonetheless I think that the driver efficiency when accurately listed is a helpful parameter to any loudspeaker engineer needing a more efficient speaker. There may not always be a one to one correspondence between transducer efficiency and loudspeaker sensitivity, but it is reasonable to conclude that a more efficient transducer will lead to a more sensitive speaker. Of course a model will give you a better comparison, but modeling costs time which is the greatest cost in engineering.
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Old 06-25-10, 04:00 AM
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yad

Join Date: Oct 2009
Posts: 169
Re: Speaker efficiency vs sensitivity

offtopic: Hi everybody. A was not here very long))) I was in business. Now i'm here too.
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