How Many Watts am I using?

[Verdinut]

1 watt is 2.83V at 8 ohm....

That is what I thought, but at least one manufacturer was quoting a different sensitivity. For instance, Tymphany is indicating 87.06 for 2.83v against 86.2 with 1 watt for their P830991 5 inch mid-bass driver. I am not dreaming, I saw in the past a difference of at least 3 dB in some manufacturer's specs.

Here is the link for the Peerless driver mentioned above:
http://www.tymphany.com/peerless/driver-search-results/driver-detail/?id=799

BTW, this is the transducer which I am using in pairs in my three front speakers, as mid-range drivers with very good results.

Cheers!

 

[mtrycrafts]

LOL I have a slide rule still myself, don't think I've used it in 40 years or so, though

...

Be sure to lube it before use for accuracy.

 

[mtrycrafts]

1 watt is 2.83V at 8 ohm....

Yes, indeed but then the dB is measured in an anechoic chamber as a standard practice or in a normal listening room without room gain of 4 dB.

 

[lovinthehd]

Yes, indeed but then the dB is measured in an anechoic chamber as a standard practice or in a normal listening room without room gain of 4 dB.

Yes, getting the detail as to how things were measured isn't always available and some manufacturers tweak the stat to their purposes....

Not sure I even remember how to use the slide rule let alone the lube (it's just a decoration in the shop these days)...we got calculators soon after being introduced to the slide rule and well, I didn't like using an abacus much either

 

[lovinthehd]

That is what I thought, but at least one manufacturer was quoting a different sensitivity. For instance, Tymphany is indicating 87.06 for 2.83v against 86.2 with 1 watt for their P830991 5 inch mid-bass driver. I am not dreaming, I saw in the past a difference of at least 3 dB in some manufacturer's specs.

Here is the link for the Peerless driver mentioned above:
http://www.tymphany.com/peerless/driver-search-results/driver-detail/?id=799

BTW, this is the transducer which I am using in pairs in my three front speakers, as mid-range drivers with very good results.

Cheers!

You might like this article http://www.audioholics.com/loudspeaker-design/loudspeaker-sensitivity

 

[highfigh]

Yes, getting the detail as to how things were measured isn't always available and some manufacturers tweak the stat to their purposes....

Not sure I even remember how to use the slide rule let alone the lube (it's just a decoration in the shop these days)...we got calculators soon after being introduced to the slide rule and well, I didn't like using an abacus much either

In that case, you might like this- no need for lube, no parts to replace and they don't need batteries-

 

[highfigh]

That is what I thought, but at least one manufacturer was quoting a different sensitivity. For instance, Tymphany is indicating 87.06 for 2.83v against 86.2 with 1 watt for their P830991 5 inch mid-bass driver. I am not dreaming, I saw in the past a difference of at least 3 dB in some manufacturer's specs.

Here is the link for the Peerless driver mentioned above:
http://www.tymphany.com/peerless/driver-search-results/driver-detail/?id=799

BTW, this is the transducer which I am using in pairs in my three front speakers, as mid-range drivers with very good results.

Cheers!

If you ever need a reasonably-priced 6.5", look at their HDS-P830874- I'm using them in 2-1/2 way towers and they work extremely well.

 

[Verdinut]

You might like this article http://www.audioholics.com/loudspeaker-design/loudspeaker-sensitivity

I've just perused Gene's article. He says that speaker sensitivity should always be specified with the impedance load, but manufacturers seldom mention for which impedance the tests were made.

Thanks for the link.

 

[Verdinut]

If you ever need a reasonably-priced 6.5", look at their HDS-P830874- I'm using them in 2-1/2 way towers and they work extremely well.

Yes, those Peerless transducers are amazing and also at an affordable price.

 

[highfigh]

I've just perused Gene's article. He says that speaker sensitivity should always be specified with the impedance load, but manufacturers seldom mention for which impedance the tests were made.

Thanks for the link.

The standard sensitivity test is done with 2.83VAC(1W)/8 Ohms/1meter unless it's car audio, in which case, they specify 4 Ohms because car audio uses 4 Ohm speakers unless it's completely custom or the woofers are wired series or parallel.

 

[TLS Guy]

This is a long standing question that drives a ton of "should I buy a new amp?" type of questions. I think a lot of people have no real idea (me included) what their current rig is outputting for power and whether or not more power would make any audible difference. So here goes for the amplifier gurus:

QUESTION: How can I measure the wattage my AVR is putting out right now as I play music? What's the technique? Is there a way to guesstimate it?

Observation: Before you tell me to go to Gene's article on how he measures amplifier power (FOUND HERE), I went there and couldn't make heads or tails of it. I need SIMPLE. Not necessarily technically accurate, but SIMPLE.

Here's what I have done so far:
I took my trusty Simpson Voltmeter (yeah, its analog), set it to VAC on the lowest scale
Hooked it up across my speaker input leads (high impedance meter, should not affect the load)
Measured the VAC at two listening volumes : 80db and 90db at my listening position
At 80db the meter barely registered : maybe .25 VAC (one quarter volt ac)
At 90db the meter was dancing with the music at 1.3 to 1.5vac
My listening position is 60 inches on the nose from the speaker
Speakers are Klipsch RB25's and they are rated at 8 ohms

How can I turn that simple measure in to a guesstimate about output power on my amp?
The only formula I have seen gives me too small a number. Rather than die a painful arithmetic death, I know someone on AH knows how to do this in their sleep. And no, I don't have an oscilloscope these days. I sold it years ago.

I think this is a hard thing to get a handle on. Measuring the output with music is pretty futile. Music contains a massive array of frequencies, and loudspeaker impedance is all over the map with frequency.

So the beat approach is to get to it with spl. That opens up another can of worms. My RS meter has a meter. There is no meter movement that has the ballistics to read close to peak spl. So what is really required is a meter plus LED peak metering. What I can tell you from my recording days, is that a mechanical meter will under read peak by at least 10 db. That means it under estimates power demands by a factor of 10. As in all audio it is the peaks you must cover for lifelike reproduction.

If I'm listening to compressed FM radio at below concert level, then the spl is 60 to 80 db and mainly around 70 db.

On the other hand a big blockbuster work digitally recorded has an enormous dynamic range. Played at concert level the peaks cluster around 90 db on the RS meter, going to 94 now and again. Because of the ballistics of the meter I know full well the transient peaks are over 100 db.

Now that spl calculator looks very nice. One caveat though spl. is in 1 watt I meter. Now with a true 8 ohm speaker the spl figure at 1 watt 1 meter and 2.83 volts are the same. However for a four ohm speaker it will register as 3db more sensitive if quoted at 2.83 volts rather than 1 watt 1 meter. So if your speakers are 4 ohm, and specified at 2.83 volts, then you need to subtract 3db when entering the sensitivity number in the calculator.

It still can get complicated. The short lines in my mains are 89 db 2.83 volts 1 meter. So that is 86db 1 watt 1 meter. Now the long lines have speakers connected directly to their amps. The drivers are 8 ohm so 87 db sensitivity in either spec. Now the upper driver handles the BSC for the mids, and does duty below 60 Hz, the lower driver only performs below 60 Hz. The total power available to each speaker is 550 watts. The amps deliver 250 watts to 4 ohms and 150 watts to 8 ohms. Now in music the chance of all the amps being able to deliver their full power before one of the three amps clips is remote. So a fudge factor is required. So I would say that 400 watts would likely be the absolute maximum that would be delivered to one speaker delivering program and it might well be less. So that is 800 watts for the two fronts

If we run the calculator, and take my preferred listening distance of 16 ft, then the max likely spl is 104 d at the listening position So that is just about enough. 80 watts would produce 94 db and 8.4 watts 84 db.

Now lets calculate the whole theater. The center has 300 watts available, but one amp only handles BSC. So I would say we have at most 200 watts available for music.

The surrounds are 4 ohm 86 db sensitivity for the calculator. 500 watts available for the two speakers. The rear backs are biamped and the top end 8 ohm the lower 4 ohm. So 400 watts is available to each speaker. But the top end would run out of power before the bottom end. So I would say the max power would be 300 watts per speaker, 600 for the two. However the sensitivity of these speakers is 84 db, so we need to reduce the 600 watts to 300 watts. So realistically we have at most 1800 watts available to the whole studio.

So what does the calculator say. That gives us 119 db for the 7.1 system. So 180 watts would give 99 db and 18 watts 89 db.

So actually for the type of program I listen to the power available is about right. Even though a lot of the time only 2 watts is required! It's all about that logarithmic curve.

What I do know is that music peaks have never sounded so effortless since I have had truly adequate powering.

 

[PENG]

Now that spl calculator looks very nice. One caveat though spl. is in 1 watt I meter. Now with a true 8 ohm speaker the spl figure at 1 watt 1 meter and 2.83 volts are the same. However for a four ohm speaker it will register as 3db more sensitive if quoted at 2.83 volts rather than 1 watt 1 meter. So if your speakers are 4 ohm, and specified at 2.83 volts, then you need to subtract 3db when entering the sensitivity number in the calculator.

That's one reason why I made my own spreadsheet, but that calculator gets one in the ball park as long as one knows to deduct 3 dB for 4 ohm speakers. If the impedance is in between 2 and 8 ohms then not everyone would know how, but could still get close by approximating it to 2,4,8 ohms.

 

[PENG]

I've just perused Gene's article. He says that speaker sensitivity should always be specified with the impedance load, but manufacturers seldom mention for which impedance the tests were made.

Thanks for the link.

You are right, they don't usually specify the impedance load used for the measured sensitivity, but they do provide the so called nominal impedance. Even if they try, it gets complicated because impedance varies with frequency, that' why nominal impedance sort of make some sense but manufacturers don't stick to the same definition for "nominal" either.

In order to have some safety margin, it is not a bad idea to subtract 3 dB from the specified sensitivity, but be sure to do it after also subtracting 3 dB from the 2.83V/1 meter format if the load impedance is 4 ohms, or 1.25dB if the load impedance is 6 ohms. Obvious that step is unnecessary if the specified sensitivity is already in the 1W/1 meter format.

Examples:

Consider the OP's Klipsch RB-25 - sensitivity: 94dB @ 2.83V/1 meter, nominal impedance: 8 ohm
Since the impedance load is 8 ohm, the sensitivity spec can be re-stated as the same 94dB @ 1W/1m.
So I would consider it as 91dB @2.83V/1 meter, or 91 dB @1W/1 meter.

Revel F36 - sensitivity: 91dB @ 2.83V/1 meter, nominal impedance: 6 ohms
To convert it to 1W/1 meter, because the nominal impedance is 6 ohms, deduct 1.25 dB so it becomes
91-1.25=89.75 dB and the sensitivity converted to 1W will be: 89.75dB @ 1W/1 meter.
So I would consider it as 86.75dB @1W/1 meter.

I really don't like converting the @2.83V/1m to @1W/1m step but unfortunately, people have been using the term amplifier power output in watts forever when trying to figure out how much power is needed for their speakers.

Technically speaking, people should have simply used voltage "V" and amperes "A" and forget about the W, but that's another controversial topic for another day.

 

[PENG]

That is what I thought, but at least one manufacturer was quoting a different sensitivity. For instance, Tymphany is indicating 87.06 for 2.83v against 86.2 with 1 watt for their P830991 5 inch mid-bass driver. I am not dreaming, I saw in the past a difference of at least 3 dB in some manufacturer's specs.

Cheers!

Again, the sensitivity for 1W and 2.83V will not be the same unless the load impedance is 8 ohms.

 

[Bucknekked]

I have located a nice digital Fluke Meter. It may take me a week or so to swing by and borrow it. I will then try this again with a 1Khz tone, a suitable db listening level, and a digital meter. I will see if we can't refine the number just a bit , or at least come up with a process that the brain trust thinks is worthy of the effort. I think the 1khz tone is doable and helps, and the digital meter will help a bit too.

I will leave the slide rules in my display case. I try never to use lube unless I'm really, really serious about getting the wood to move.....................

 

[Bucknekked]

Again, the sensitivity for 1W and 2.83V will not be the same unless the load impedance is 8 ohms.

my speakers are supposed to be 8 ohms. I don't know anything different.
My new Salks are going to come in between 4 and 6 ohms and I will cross that bridge when they arrive.

 

[yepimonfire]

The easiest way is to assume your avr is only going to put out 70% of its claimed 2ch power ACD. Figure up your speakers sensitivity rating for each set, then figure out how loud you listen. Assuming you've properly calibrated your speakers to all play at 75dB at the listening position, if you've got a receiver with a relative volume control (measured in minus dB), subtract that from 105dB, so say you watch movies at -20dB, that'd be 95dB. If you don't have a relative volume control, just turn it to what you normally listen at, and use rew to generate pink noise at -3dBfs, then measure that using a C weighted spl meter at the main listening position. That's your maximum peak spl requirement. Once you've figured that out, head over here and plug the numbers in http://www.crownaudio.com/en-US/tools/calculators#amp_power_required

You'll need to do that for each speaker set if they're different sensitivity ratings and distances.

You'll either find out you need a whole lot less power than you thought or a whole lot more. This is one reason I suggest using pro audio amps if your receiver isn't up to snuff. Adding a 150w amplifier in place of the internal 100w amp is going to give you a lousy 1.5dB gain. Some people rationalize that adding an amplifier to the fronts takes a load of the receiver to handle the center and surrounds, and while this is true, you're still limited to that maximum 2ch driven. You're not gonna get more than that, even if the power supply is up to snuff, the voltage rails can't supply more than the maximum value their built for without clipping.

If you're running 3-6dB below what you need, you should probably invest in a 200-400w amp. If you're at the higher end of that range, it might be time for some bigger more sensitive speakers. A set of bookshelves may be rated at 85dB, while their floor standing counterparts might be 89db, or even 91dB, in addition, they can handle the extra power for peaks without frying.

A huge misconception is that you only need to focus on the front two channels since they supposedly carry the weight, that's completely false. I've pulled the audio tracks off of blu rays for several movies and opened them up in Reaper to see how much content is in each channel and at what volume. Even in dramas and comedies, the surrounds are doing just as much work as the front left and right for at least 80% of the time, if not for effects, for music, the center channel is doing about 60% of the entire soundtrack, including full range effects, not just dialogue. If you can find the space and have the budget, I strongly suggest making sure your surrounds are just as competent and large as your fronts, obviously using a tower speaker as a center channel isn't practical in most cases, so just get the biggest one you can find to match the power of your fronts.

The hard truth is unless you're using a budget receiver rated at 50wpc, upgrading your 100wpc receiver for a 120wpc receiver isn't going to help if you're really hurting for power.





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[yepimonfire]

I've got 94dB with the klipsch I'm using at 1w1m in an untreated room using pink noise. Although this is their new reference series.

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[lovinthehd]

The easiest way is to assume your avr is only going to put out 70% of its claimed 2ch power ACD. Figure up your speakers sensitivity rating for each set, then figure out how loud you listen. Assuming you've properly calibrated your speakers to all play at 75dB at the listening position, if you've got a receiver with a relative volume control (measured in minus dB), subtract that from 105dB, so say you watch movies at -20dB, that'd be 95dB. If you don't have a relative volume control, just turn it to what you normally listen at, and use rew to generate pink noise at -3dBfs, then measure that using a C weighted spl meter at the main listening position. That's your maximum peak spl requirement. Once you've figured that out, head over here and plug the numbers in http://www.crownaudio.com/en-US/tools/calculators#amp_power_required

You'll need to do that for each speaker set if they're different sensitivity ratings and distances.

You'll either find out you need a whole lot less power than you thought or a whole lot more. This is one reason I suggest using pro audio amps if your receiver isn't up to snuff. Adding a 150w amplifier in place of the internal 100w amp is going to give you a lousy 1.5dB gain. Some people rationalize that adding an amplifier to the fronts takes a load of the receiver to handle the center and surrounds, and while this is true, you're still limited to that maximum 2ch driven. You're not gonna get more than that, even if the power supply is up to snuff, the voltage rails can't supply more than the maximum value their built for without clipping.

If you're running 3-6dB below what you need, you should probably invest in a 200-400w amp. If you're at the higher end of that range, it might be time for some bigger more sensitive speakers. A set of bookshelves may be rated at 85dB, while their floor standing counterparts might be 89db, or even 91dB, in addition, they can handle the extra power for peaks without frying.

A huge misconception is that you only need to focus on the front two channels since they supposedly carry the weight, that's completely false. I've pulled the audio tracks off of blu rays for several movies and opened them up in Reaper to see how much content is in each channel and at what volume. Even in dramas and comedies, the surrounds are doing just as much work as the front left and right for at least 80% of the time, if not for effects, for music, the center channel is doing about 60% of the entire soundtrack, including full range effects, not just dialogue. If you can find the space and have the budget, I strongly suggest making sure your surrounds are just as competent and large as your fronts, obviously using a tower speaker as a center channel isn't practical in most cases, so just get the biggest one you can find to match the power of your fronts.

The hard truth is unless you're using a budget receiver rated at 50wpc, upgrading your 100wpc receiver for a 120wpc receiver isn't going to help if you're really hurting for power.

A -20dB reading on the volume would be 65 dB average level, 85 dB peaks. (10dB more for the LFE channel). That Crown calculator is more suited to venue use than home....

 

[yepimonfire]

Use REWs min/max feature, it will give you the Lz peak, which is limited only by your sampling rate.

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