SPL, watts, speaker efficiency and distance Excel calculator

[garyrc]

All these claims on "high efficient" "high sensitivty" ... should there not be information on the test-signal that is applied ? (sine, pink-noise etc)

 

Good point.  I think that they use pink noise band-limited to 500 to 2K Hz, but I could be wrong.  Or maybe it is the average SPL of a sine wave sweep over the specified range of the speaker, with 1 wt. input?  

 

Will somebody who knows let us know? 

[mustang guy]

 

All these claims on "high efficient" "high sensitivty" ... should there not be information on the test-signal that is applied ? (sine, pink-noise etc)

 

Good point.  I think that they use pink noise band-limited to 500 to 2K Hz, but I could be wrong.  Or maybe it is the average SPL of a sine wave sweep over the specified range of the speaker, with 1 wt. input?  

 

Will somebody who knows let us know? 

 

 

This is a confusing topic. As it turns out, there aren't any standards on this. I have read where it is typical to use 1kHz, but I'd say the manufacturer will measure it in a way that gives the highest number. I don't doubt that for one second. If they don't say what frequencies, then you can only guess they might be using a dubious frequency. Perhaps one a human cannot even hear.  Now that would be funny...

 

One thing is that they should feed a voltage 2.83 instead of 1 watt to an 8 ohm speaker, since that's the amount of voltage needed to dissipate 1 watt in an 8 ohm resistor. If they don't do that, the differing resistances of the speaker through the bandwidth will have differing efficiencies. Some speakers have impedances that swing wildly. Think of it as a frequency of a certain speaker which has 1.2 ohm resistance. If you are simply sending 1 watt for an 8 ohm speaker, then that 1.2ohm frequency will be drawing more current and will then be louder.

 

I like to simplify complicated topics so that I can grasp them. I understand there are differences in electrical efficiency and db watts efficiency. And those things are different than sensitivity. That clouds my understanding of the fundamentals. 

[WMcD]

 

 

Okay, I need an opinion to confirm one of mine.  It is that some of our listening is when the amp is putting out a micro-watt.

 

When you look at this

 

http://en.wikipedia.org/wiki/Sound_pressure#Sound_pressure_level

 

A normal conversation level is at 40 to 60 dB.  For easy math, let me claim 45 dB and also claim that some classical music passages are like the level of conversation in our living room.

 

 Assume  a K-Horn, LS, and Belle are putting out 105 dB at one meter.  So, 45 dB acoustic output is 60 dB down from that 1 watt level.

 

By my calculations, the amplifier is putting out a micro-watt.

 

Agreed?

 

WMcD

 

 

 

 

 

So, let us say that some musical passages for classical music reproduction are at conversational levels.

Yes, one microwatt at 1 meter. If you are sitting 20' away and the SPL is 45db, then it's more like 4 micriwatts. 3.98107E-05 to be precise.

 

I have updated the spreadsheet above to show more precision.

 

 

Thank you for the calculations.

 

My next calculations are to figure just how must voltage must be applied to the speaker terminals, which is amplifier output, to achieve these levels of power input. Assuming a nominal 8 ohm load.

 

I get 0.0057 volts for 4 microwatts, and 0.00282 volts for 1 microwatt.

 

I'm not posting the figures to sing praises of the speaker.  Rather, we should consider whether the amp can produce undistorted output at those levels. 

 

Not even Nelson Pass publishes distortion down at those levels, perhaps because measurement equipment will not measure down that low.  Yet he does indicate that Class A amplifier tend to have distortion decreasing with level. 

 

Maybe we should investigate an issue about 16 bit recordings.  Let us assume max 16 bits are eventually translating to 90 dB or 100 dB output.  How many bits are sounding at 30 or 40 dB?

 

WMcD

 

 

[Travis In Austin]

...

Now if someone can explain the difference to me between speaker sensitivity versus efficiency, in terms I can understand I would be most appreciative.

...

I always thought of them as the same thing.

My LaScalas are efficient speakers because they are 104db at 1 meter with 1 watt

My LaScalas are sensitive to 1 watt of power in that they provide 104db from 1 meter away.

I did to until Chief Bonehead caught himself using the terms interchangeably and he started to explain they were very different concepts, yet were interrelated thus causing the confusion.

Here is an excellent site that discusses the concepts, complete with calculators and methodology on testing. I still cannot wrap my head around the difference even though the author's premise starts out that they are "not the same."

http://www.sengpielaudio.com/calculator-efficiency.htm

Edited May 17, 2015 by dwilawyer

[Travis In Austin]

According to the site

Sensitivity in dB = 112 + 10 log (efficiency)

Efficiency = 10(Sensitivity in dB – 112)/10

The 112 comes from the 0db reference point for sound as follows:

"Where does the 112 dB come from? The 0 dB reference level for sound is 10−12 watts.

1 acoustical watt means 120 dBSPL.

The standard measurement for loudspeakers is done with an infinite baffle sounding in a half room with a distance of r = 1 m.

The resultant factor 2π × r2 (area of a half sphere) equals −8 dB. Therefore we get for an efficiency of 1 = 100 % a sensitivity of 120 − 8 = 112 dB.

This calculation works correct if the loudspeaker radiates in a hemisphere 2π. Otherwise you must add the factor Q because of directionality.

Solid sphere Q = 1, hemisphere Q = 2, quarter sphere Q = 4, and eighth sphere Q = 8."

[Travis In Austin]

Here is a site that discusses standards for testing sensitivity, including IEC references.

http://www.prosoundweb.com/article/loudspeaker_sensitivity_whats_a_watt_anyway/

Travis

[mustang guy]

 

 

 

Okay, I need an opinion to confirm one of mine.  It is that some of our listening is when the amp is putting out a micro-watt.

 

When you look at this

 

http://en.wikipedia.org/wiki/Sound_pressure#Sound_pressure_level

 

A normal conversation level is at 40 to 60 dB.  For easy math, let me claim 45 dB and also claim that some classical music passages are like the level of conversation in our living room.

 

 Assume  a K-Horn, LS, and Belle are putting out 105 dB at one meter.  So, 45 dB acoustic output is 60 dB down from that 1 watt level.

 

By my calculations, the amplifier is putting out a micro-watt.

 

Agreed?

 

WMcD

 

 

 

 

 

So, let us say that some musical passages for classical music reproduction are at conversational levels.

Yes, one microwatt at 1 meter. If you are sitting 20' away and the SPL is 45db, then it's more like 4 micriwatts. 3.98107E-05 to be precise.

 

I have updated the spreadsheet above to show more precision.

 

 

Thank you for the calculations.

 

My next calculations are to figure just how must voltage must be applied to the speaker terminals, which is amplifier output, to achieve these levels of power input. Assuming a nominal 8 ohm load.

 

I get 0.0057 volts for 4 microwatts, and 0.00282 volts for 1 microwatt.

 

I'm not posting the figures to sing praises of the speaker.  Rather, we should consider whether the amp can produce undistorted output at those levels. 

 

Not even Nelson Pass publishes distortion down at those levels, perhaps because measurement equipment will not measure down that low.  Yet he does indicate that Class A amplifier tend to have distortion decreasing with level. 

 

Maybe we should investigate an issue about 16 bit recordings.  Let us assume max 16 bits are eventually translating to 90 dB or 100 dB output.  How many bits are sounding at 30 or 40 dB?

 

WMcD

 

 

 

I wonder how many watts come out of a preamp. Have you tried driving your speakers directly from a preamp? That would be a cool experiment!

[mustang guy]

Travis, I read an article published by stereophile about efficiency and sensitivity, and I didn't like it, so I invented my own definitions.  

[djk]

The difference between efficiency and sensitivity are mainly of concern if you have a tube amp and have to use a lower impedance tap, or a solid-state amp that can't drive the low impedance.

[djk]

"What about a good old fashioned slide rule?  "

 

Used one for many years, a plastic Post, a bamboo Post, a bamboo K&E (the Cadillac of slide-rules).

[Quiet_Hollow]

How many bits are sounding at 30 or 40 dB?

Except that it doesn't work like that.

 

To summarize where PCM sound files are concerned, bit depth (8,16,24) establishes the dynamic range.

 

Any such value is a fraction of what is deemed full-scale (ie. a discrete increment of loudness) expressed as a binary number. There is no single bit that turns on or off to render sound.

[mustang guy]

This question got buried in a post, so I'll ask again.

 

Has anybody powered speakers directly from a preamp?  If microwatts make you happy, you should be able to achieve that directly from the preamp. I don't have my sliderule, but I do have google, so I found that somebody did a calculation of around 20 microwatts directly from a preamp. 

[mikebse2a3]

This question got buried in a post, so I'll ask again.

Has anybody powered speakers directly from a preamp? If microwatts make you happy, you should be able to achieve that directly from the preamp. I don't have my sliderule, but I do have google, so I found that somebody did a calculation of around 20 microwatts directly from a preamp.

While you might get a little sound most pre-amps output stage impedance and current capability would not be able to drive a loudspeaker with any fidelity.

I should add putting a 4 ohm or 8 ohm load on a pre-amp could damage them since they are normally designed for a much higher load.

Miketn

Edited May 19, 2015 by mikebse2a3

[mustang guy]

 

This question got buried in a post, so I'll ask again.

Has anybody powered speakers directly from a preamp? If microwatts make you happy, you should be able to achieve that directly from the preamp. I don't have my sliderule, but I do have google, so I found that somebody did a calculation of around 20 microwatts directly from a preamp.

While you might get a little sound most pre-amps output stage impedance and current capability would not be able to drive a loudspeaker with any fidelity.

I should add putting a 4 ohm or 8 ohm load on a pre-amp could damage them since they are normally designed for a much higher load.

Miketn

 

It's a good thing you responded! I would have tried it myself if nobody did, and I would hate to cause damage to any of my preamps.

 

Let this be a warning to everybody. Don't try powering your speakers from a preamp.  !!

[WMcD]

How many bits are sounding at 30 or 40 dB?

Except that it doesn't work like that.

 

To summarize where PCM sound files are concerned, bit depth (8,16,24) establishes the dynamic range.

 

Any such value is a fraction of what is deemed full-scale (ie. a discrete increment of loudness) expressed as a binary number. There is no single bit that turns on or off to render sound.

I think I've been misunderstood.

My thinking is as follows regarding one microwatt, or actually 60 dB down from maximum level.

If 16 bits are on we get the greatest voltage output of the playback unit.

1111111111111111 = 65536

so

-60 = 20 log (x/65536)

Solving for x we get 65.536

The value of 65 in binary is 0100001

Therefore a sine wave at -60 dB is using only 6 bits, and for the most part 5 bits. So it seems to me that the signal is going to sound like it has a bit depth of 6 or 5 bits, and most 5 bits. That seems pretty low. That is what I meant by sounding.

Am I doing something wrong here?

WMcD

Edited May 20, 2015 by William F. Gil McDermott

[WMcD]

The calculation seems pretty good.

Suppose we look at -90 dB.

-90 = 20 log (x/65536)

Solving for x we get 2.07, and 2 in binary is 010. Therefore a sine wave is using just the 2 least significant bits. Therefore a 16 bit device should have a dynamic range of just over 90 dB. Which is what I understand the fact to be.

WMcD

[Zen Traveler]

I've been following this thread because I wanted to see how many folks who have larger Heritage speakers feel the need to add external amps to AVRs to drive them. From what I understand is that they are actual 8 ohm rated speakers and don't have a jagged Frequency Response that dip much below 6 Ohms....

 

If that's true, what benefit does adding an external SS amp bring?

Edited May 20, 2015 by tkdamerica

[ClaudeJ1]

I've been following this thread because I wanted to see how many folks who have larger Heritage speakers feel the need to add external amps to AVRs to drive them. From what I understand is that they are actual 8 ohm rated speakers and don't have a jagged Frequency Response that dip much below 6 Ohms....

 

If that's true, what benefit does adding an external SS amp bring?

It adds noise and keeps the cable companies in business.

 

I have been running Onkyo AV receivers through all my horns for over 10 years. You can't get shorter connections with proper grounding than with integrated. Since most Klipsch stuff never uses a watt, unless you get "stupid loud," it's a big waste.

 

Also, the difference between the ads for "watts" from 80-90-100-135 etc. is about 2 db Watts at the most. Mostly balderdash for marketing purposes unto the terminally stupid Best Buy crowd.

Edited May 20, 2015 by ClaudeJ1

[ClaudeJ1]

The calculation seems pretty good.

Suppose we look at -90 dB.

-90 = 20 log (x/65536)

Solving for x we get 2.07, and 2 in binary is 010. Therefore a sine wave is using just the 2 least significant bits. Therefore a 16 bit device should have a dynamic range of just over 90 dB. Which is what I understand the fact to be.

WMcD

Yes sir. 90 db dynamic range is 30 db better than any LP, which I experienced from Master tapes using DBX companders in the late 70's. Once I joined the AES, per PWK's suggestion, I anticipated the arrival of CD's in 1983 and bought a SONY. I immediately switched, even when there were only about 20 titles at $20 apiece to HAVE that extra dynamic range free of ticks and pops.

 

Now we have 135 db dynamics on Blue Ray and very few are recording with it, except for Mark Waldrep at AIX. Shame.

Edited May 20, 2015 by ClaudeJ1

[ClaudeJ1]

I wonder how many watts come out of a preamp. Have you tried driving your speakers directly from a preamp? That would be a cool experiment!

 

Pre-amps don't produce "Watts" because they have a high source impedance, usually less than 1,000 ohms. they only produce VOLTAGE up to maybe 1-10 volts and are made to drive the front end of a Power Amp, which have input impedances ranging from 10,000 to 100,000 ohms. The current ouput is in the milli to micro amps.

 

In order to driver a speaker, you need a source impedance equal to or less than the speaker impedance.

 

Tube Power amps have high source impedance also, but they run at over 300 Volts and get transformed down to low impedance. You gotta have the IRON to get down there, as the old saying goes.

 

I like modern solid state because the source impedance is very low and they produce as much current as required to drive woofers out of their frames if need be (25 amps is not uncommon these days). They are also good for spot welding in a pinch. LOL.

 

For a while, I was driving my Peavey FH-1 bass horns with a 6 watt chip amp. You gotta love horns because you can use any amp with them and power hungry they are NOT.

Edited May 21, 2015 by ClaudeJ1