Is there any way to know how many watts you are using on your receiver?

[PENG]

I agree with TLS that 1/4 watt is enough for R1 and R2 but it doesn't hurt to go a little higher.

 

[MidnightSensi]

The best way is to use a wattmeter. That's what I do. I have a commercial recording wattmeter that I picked up at an electronics repair shop that was going out of business. In my room with the home theater adjusted for normal listening levels (dialogue at the level I would hear if the actors were in the room with me) I get about 700 milliwatts continuous during musical segments and upwards of 20 watts on peaks (explosions etc.) into my main speakers. I do have a powered sub and that relieves the main speakers of some of the load, of course.

What's the sample rate of your wattmeter?

 

[fmw]

DC to 1 KHz: ± 5 counts
1 KHz to 5 KHz: ± 10 counts
5 KHz to 10 KHz: ± 15 counts

Those are counts per second.

 

[MidnightSensi]

DC to 1 KHz: ± 5 counts
1 KHz to 5 KHz: ± 10 counts
5 KHz to 10 KHz: ± 15 counts

Those are counts per second.

So you have software to map it?

I guess the reason I'm asking is I've looked at wattmeters but couldn't find one within my budget that could map musical peaks. I have a regular wattmeter that is okay for finding peak averages but not peaks.

 

[fmw]

So you have software to map it?

I guess the reason I'm asking is I've looked at wattmeters but couldn't find one within my budget that could map musical peaks. I have a regular wattmeter that is okay for finding peak averages but not peaks.

Yes. I bought mine at an auction of an electronics lab that was going out of business. I paid $250 for it. I think they go for around $3500 new. They aren't the kind of think you view as a casual purchase.

I don't think the recording feature is that big a deal, truthfully. Instantaneous peaks aren't audible anyway. An explosion lasts long enough to read the meter without any problem at all. What you have is probably fine. What sorts of results do you get with yours?

 

[MidnightSensi]

Yes. I bought mine at an auction of an electronics lab that was going out of business. I paid $250 for it. I think they go for around $3500 new. They aren't the kind of think you view as a casual purchase.

I don't think the recording feature is that big a deal, truthfully. Instantaneous peaks aren't audible anyway. An explosion lasts long enough to read the meter without any problem at all. What you have is probably fine. What sorts of results do you get with yours?

At home I can't turn it up enough to get a good reading because I live in an apartment. I have a Crown XLS powering a pair of M&K S-150s, and it never goes above 50 watts but again I don't really crank it. I could use whatever amp if the speakers weren't 4-ohm.

I did bring it along to a set once and connected it to one of my monitors and read 101watts hold, the booth is supposed to be 98dB (with two booth monitors and ambient noise from the floor) at reference on the mixer. I reached over and connected it to a mid-box that hangs over the booth and read 350-watts. The floor is supposed to be 110dB-120dB (depending on where you are standing), but that is spread over numerous speakers. They had to make a map of this because of worker safety/NIOSH. Those levels are AVERAGE values, not peak, as I found out. So, I'm now wearing earplugs. I tried connecting it to a subwoofer one night but it wouldn't stay on there (when I brought it I put it on, do my set and then pick it up on the way out to see the peak hold). I have to be a bit sneaky about it because it looks a little weird leaning behind a sub to connect a meter.

 

[fmw]

At home I can't turn it up enough to get a good reading because I live in an apartment. I have a Crown XLS powering a pair of M&K S-150s, and it never goes above 50 watts but again I don't really crank it. I could use whatever amp if the speakers weren't 4-ohm.

It's a little hard to determine what a "normal listening level" is but my guess is that you use yours about like I use mine. Our speakers are probably a handful of db different in efficiency.

I did bring it along to a set once and connected it to one of my monitors and read 101watts hold, the booth is supposed to be 98dB (with two booth monitors and ambient noise from the floor) at reference on the mixer. I reached over and connected it to a mid-box that hangs over the booth and read 350-watts. The floor is supposed to be 110dB-120dB (depending on where you are standing), but that is spread over numerous speakers. They had to make a map of this because of worker safety/NIOSH. Those levels are AVERAGE values, not peak, as I found out. So, I'm now wearing earplugs. I tried connecting it to a subwoofer one night but it wouldn't stay on there (when I brought it I put it on, do my set and then pick it up on the way out to see the peak hold). I have to be a bit sneaky about it because it looks a little weird leaning behind a sub to connect a meter.

I took mine once to a performance and connected it to one of my PA speakers. The venue was a hotel meeting room that seats about 500 people. It was full and very dead sounding. I recorded 210 watts per channel at the peaks. My amp delivers 350 watts per channel so I came close to using it up. The speakers are Electro Voice Horns and they are very efficient - about 100 db or so. That room really sucked up the sound.

 

[MidnightSensi]

It's a little hard to determine what a "normal listening level" is but my guess is that you use yours about like I use mine. Our speakers are probably a handful of db different in efficiency.



I took mine once to a performance and connected it to one of my PA speakers. The venue was a hotel meeting room that seats about 500 people. It was full and very dead sounding. I recorded 210 watts per channel at the peaks. My amp delivers 350 watts per channel so I came close to using it up. The speakers are Electro Voice Horns and they are very efficient - about 100 db or so. That room really sucked up the sound.

Yeah, the big rooms seem to suck up a lot more power than say my living room. Part of it is those rooms are just so much bigger and I think the other part of it is the louder you want you keep having to feed it double what you did to get to where you at at....and exponents add up really quick ya know? I think the bass bins in there are 100dB efficient (deep bass), the horn subwoofers (reg bass) are like 110dB, but the mids and horn loaded tops are less efficient but still much more than my home speakers. For a laugh /turn your speakers down due to distortion/ and then listen/laugh to my attempt to record a bit of my set on a camera turn down speakers first, wait for bass to drop at 0:26 haha. Never gets old.

 

[blued888]

Wow didn't know that kind of thing exists. I might just do the DIY circuit below just in case.

http://freecircuitdiagram.com/2008/09/13/audio-power-meter-show-audio-amplifier-actual-output-power/

Anybody handy with electronics know what wattage resistors I would need and what voltage capacitors?

Thanks markw!

I've noticed that the LEDs do not have current limiting resistors, are these not necessary? I've looked at the data sheet of the IC and the original supply voltage to the LEDs are only 3V whereas it shows 12V to 20V in the URL above.

EDIT: Also what should R1 be if speaker impedance would be 6-ohms? Thanks!

 

[TLS Guy]

I've noticed that the LEDs do not have current limiting resistors, are these not necessary? I've looked at the data sheet of the IC and the original supply voltage to the LEDs are only 3V whereas it shows 12V to 20V in the URL above.

EDIT: Also what should R1 be if speaker impedance would be 6-ohms? Thanks!

You would have to look at the specs of the chip. The dropper resistors are probably in the chip, so you need to find an equivalent circuit for the chip. Chips contain, transistors, diodes, resistors and caps.

No speakers is resistive, and this is an area were this device will only give you an approximation. A loudspeaker impedance curve is all over the place. If you are fussy though , make R1 about 14K for six ohms.

 

[annunaki]

10 watts average would be very loud. However you forget the db scale is log, therefore to stay clean playing a symphony at concert level really does require an amp of significant power, driving speakers of average sensitivity. If the average power was one watt, and that would actually be pretty loud, the amp needs a minimum of 100 watts at the ready, when the orchestra digs into the strings, the brass blazes, the tymps are pounded and the cymbals crash, but just for a brief period of time. I hate amps that clip right then!

Boo to lack of headroom!

 

[blued888]

You would have to look at the specs of the chip. The dropper resistors are probably in the chip, so you need to find an equivalent circuit for the chip. Chips contain, transistors, diodes, resistors and caps.

http://www.jaycar.com.au/images_uploaded/LM3915.PDF

The LEDs are connected to the output of the comparator, I studied electronics before but honestly did not get the hang of it. Thanks for the help!

No speakers is resistive, and this is an area were this device will only give you an approximation. A loudspeaker impedance curve is all over the place. If you are fussy though , make R1 about 14K for six ohms.

... and thanks again!

 

[blued888]

Tried the circuit out and it indeed works. Cool!

 

[TLS Guy]

Tried the circuit out and it indeed works. Cool!

Well done! Nice project.