speaker sensitivity, spl

[MomurdA]

Sorry if this question has been asked before, but i couldnt find it while searching. If a speaker has a sensitivity of 95db@1w@1m, that means that from one meter away with only one watt going to it it is 95db? And that an increase in ten decibels requires twice as much power to that speaker? The reason im asking is because of my magnepans. They are about 86db@1w@1m. Instead of hooking them up directly to my marantz receiver, i am using a separate amp which is 100 watts per channel @ 4 ohms rms. Is this enuf power to make my maggies sound like they should?

[Pat D]

Sorry if this question has been asked before, but i couldnt find it while searching. If a speaker has a sensitivity of 95db@1w@1m, that means that from one meter away with only one watt going to it it is 95db? And that an increase in ten decibels requires twice as much power to that speaker? The reason im asking is because of my magnepans. They are about 86db@1w@1m. Instead of hooking them up directly to my marantz receiver, i am using a separate amp which is 100 watts per channel @ 4 ohms rms. Is this enuf power to make my maggies sound like they should?

An increase of 10 dB requires 10 times the power, and generally makes the music sound subjectively about twice as loud. An increase of 3 dB is slightly louder and requires twice the power.

The impedance of most speakers varies considerably with frequency it is impractical to try to figure out how much power they are using. Voltage sensitivity is measured with an input of 2.83 volts (which is 1 watt into an 8 ohm load) as it is more difficult--and not very useful--to actually figure out the efficiency of a speaker . Anyway, here is a link to a description of the type of measurements Soundstage does at the NRC:

http://www.soundstagemagazine.com/me...udspeakers.htm

Whether your amp is adequate to drive Maggies depends on how loud you play them.

[markw]

If a speaker has a sensitivity of 95db@1w@1m, that means that from one meter away with only one watt going to it it is 95db?

In theory, yes. That's pretty much the "standard" method mfgrs use to measure this.

And that an increase in ten decibels requires twice as much power to that speaker??

No. Applying twice as much power to the speaker would yield a 3 db increase in loudness, and 3 db is not much of a change at all.. To effectively double the loudness would require ten times the power.Here's where it gets interesting.

So, the spl a speaker produces is relative to it's sensitivity and the power drivng it.

Your speakers are 86 db and, in theory, it produces this with one watt. To geta 3 db increase would require we double this to two watts and so on and so on. Let's put this in a table to see it a little better.

86 db with 1 watt
89 db with 2 watts
92 db with 4 watts
95 db with 8 watts
--- somewhere around here the sound would seem about twice as loud.
98 db with 16 watts
101 db with 32 watts
104 db with 64 watts
--- somewhere around here the sound would seem about twice again as loud.
107 db with 128 watts
etc, etc...

As far as to if that's enough for your MMG's well, that depends what type of music you like and how loud you like it. What I can say is that my MMG's, with a powered sub cutting in around 60 hz, did quite well with a NAD 214, which was rated at 80 wpc @ 8 ohms. ...forgot what it was at 4 ohms, but it was somewhat more.

[MomurdA]

Thank you both for your prompt and informative answers. I thought that i might be wrong about the power to db ratio, its been a few years since i took an electronics course and had forgotten some things.

[RGA]

You also have to remember that most people listen at distances further than 1 meter...at two meters you need more power as sound dissapates into the room -- and different speakers do this differently.

Ideally, you want a speaker that does not have an total impedence swing of more than 12ohm from minimum to maximum and ideally you don't want a very low minimum impedence because that requires big amplifiers whihc are generally more expensive and can be noisier and of course eliminates a lot of fine lower power amps. If a 4 ohm speaker doesn;t dip below 3 ohms and does not go above say 15 ohm then a lower powered amp rated for 4ohms including SETs should work fine.

If a speaker rated at 8ohm dips to 3 and goes beyond say 25 ohms in the audible range then it's probably an incompetantly designed speaker as this is a design in which the engineers have not covered their bases.

Planars are different --- usually when you sacrifice efficieny in a BOXED speaker you are making this choice for added bandwidth (more deep bass response) AND OR you are going to a smaller cabinet -- Totem tries to get a lot of bass from very small boxes as such they sacrifice sensitivity as well as efficiency and also how LOUD they can play will be lower than big beasts.

[E-Stat]

You also have to remember that most people listen at distances further than 1 meter...at two meters you need more power as sound dissapates into the room -- and different speakers do this differently.

You have brought up an important point when comparing speakers. Indeed I know few folks who listen at a distance of one meter.

Conventional speakers (including your ANs) drop output by the inverse square law. Double the distance and get one-fourth the output. Planars, like the Magnepan and other line source speakers, however, drop output in a linear fashion.

Using Markw's chart, let's compare a conventional speaker "A" to a line source, "B" having the same efficiency driven by 64 watts:

--------------Speaker A-------------------------------------Speaker B

1 meter -----104 db-------------------------------------------104 db
2 meter------- 98 db-------------------------------------------101 db
3 meter--------92 db---------------------------------------------98 db

3 meters is about my listening distance. In this case, the conventional speaker would require four times the power (256 watts) to play at an equivalent output as the line source to make up for the 6 db loss. Or conversely, they would need to be 6 db more efficient.

Is 100 watts enough power? Like Pat says, it depends. If you listen mainly to popular music which has relatively little dynamic range, then it probably is enough. If, however, you enjoy classical music that typically has wider dynamic range swings, then you may need more. If only for the occasional peaks that require far more power. While the peak requirements of classical are higher, the average power levels, on the other hand, are lower.

rw

[RGA]

E-Stat

This is why we need t look at a multitude of issues with speaker amp relationships and of course listen. If you know Audio Note at all you'll notice they are a little higher in the power department compared to a lot of SET makers because as sensitive as they are they are still under 100db of the big horns...and An isn;t designed for extremely large rooms other than the e which can do it --- there are limits to how loud they can play...but really because watts need to double for every 3db increase the added watts are often claimed to be useful really only for as you note dynamic range.

It's a dilemma for me though because if high watts are helpful for dynamic range then one should expect the B&W or Paradigm speakers at 90db+ in room response to sound as if they retain superior dynamics at low and higher volume levels than something like my amp and speaker combo when the amp is pumping just 10 watts and a speaker that is really only 90db away from corners. So the impedence issue is the first thing i think of here because it is far smoother on AN than it is in on any B&W Paradigm or any siimilar design to these I've seen. This is where the superiority of stats have always held court at low levels they are superb and you have no desire or need to turn the volume UP to make things out - there is not a single B&W I have ever heard that I can say that about.

but there must be something more to the game than impedence as well -- I'm not an engineer so what I am doing is observing the sound by listening and then trying to back fill information in simpler terms fior myself to sorta "get" what it is Audio Note a Boxed speaker is doing to retain the low level resolution and low level full range dynamics of the electrostats with the ability of some of the big horns to not "lose it" under complex orchestral work at loud levels with such relatively few watts. I am not suprirsed that so many stat owners I've spoken to have liked AN (no it doesn;t totally sound like a stat but it's a lot closer than any B&W like speaker which seem sorta slow and veiled and incredibly boxy sounding in comparison).

I know Peter discussed their speaker design which involves a technical approach related to pressure (which isn't the same as SPL) in their design and if you hear them against typical boxed speakers you will see or hear perhaps what they mean -- For instance if you do a listening panel session and you level match the products the AN will present a full range presentation and seem louder even if put 3-4db lower than other boxed speakers -- now that is cool. None of this is talking about sound quality which I admit is subjective but if a speaker needs to be turned UP to make things out --- it's a bad speaker IMO. Because if it is missing information at low level why would one think it's going to be there when the volume goes up?

it all goes to that 1st watt theory get it right because 10,000 bad ones just makes bad louder. It is no wonder he takes a beating from people who have never heard an entire set-up in action...it is possible that he is in fact correct in his views - the majority buys Bose and Caveliers --- but that doesn't mean their better than Quad, AN, and Ferrari.

I assume you own a stat --- when I heard my first stat --- well I understand why many would not want to go to boxed speakers.

[markw]

Indeed I know few folks who listen at a distance of one meter.

Conventional speakers (including your ANs) drop output by the inverse square law. Double the distance and get one-fourth the output. Planars, like the Magnepan and other line source speakers, however, drop output in a linear fashion.

Using Markw's chart, let's compare a conventional speaker "A" to a line source, "B" having the same efficiency driven by 64 watts:

--------------Speaker A-------------------------------------Speaker B

1 meter -----104 db-------------------------------------------104 db
2 meter------- 98 db-------------------------------------------101 db
3 meter--------92 db---------------------------------------------98 db

3 meters is about my listening distance. In this case, the conventional speaker would require four times the power (256 watts) to play at an equivalent output as the line source to make up for the 6 db loss. Or conversely, they would need to be 6 db more efficient.
rw

You've never seen our little library . It doesn't really allow much more than 2 meters from those particular speakers (not the maggies).

The 1 meter reading is more of a method of standardizing a measurement procedure and, true, does not take into account the real world situation. I will incorporate this addendum into the next time I give this spiel.

Any thoughts to making something like this into a FAQ since it's a question that's, well, asked quite frequently??

[poneal]

QUOTE from RGA -- If a speaker rated at 8ohm dips to 3 and goes beyond say 25 ohms in the audible range then it's probably an incompetantly designed speaker as this is a design in which the engineers have not covered their bases.


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While the ideal would be to have a perfectly flat response, perfect phase tracking, and linear impedance, generally you can only get two of these close at the expense of the third. Since solid state amps have such low source impedance, fluctuations in impedance will have negligible audible effect on the resultant response. So saying that this would be an incompetent design is a false statement.
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[Pat D]

QUOTE from RGA -- If a speaker rated at 8ohm dips to 3 and goes beyond say 25 ohms in the audible range then it's probably an incompetantly designed speaker as this is a design in which the engineers have not covered their bases.


************************************************** ******************************************
While the ideal would be to have a perfectly flat response, perfect phase tracking, and linear impedance, generally you can only get two of these close at the expense of the third. Since solid state amps have such low source impedance, fluctuations in impedance will have negligible audible effect on the resultant response. So saying that this would be an incompetent design is a false statement.
************************************************** ******************************************

I have no idea why one would worry about whether the impedance of a speaker got up fairly high. Many speakers do this. My old Kef 104 speakers got up to 40-70 ohms depending on the setting of the midrange control and only got slightly below 7 ohms as a minimum. They had an excellent impulse response, BTW. An amp has no difficulty at all in driving a highish impedance.