dB meters

[squarewave]

Hi, I'm looking for advice on which dB meter to buy.

 

At the moment I have a £40 Maplins special (Type 2). Accurate to ±1.5dB. A/C weighting. 30 - 130dB range.

 

I have a job next year, for which I will need something more professional.

 

I need to measure and compare six different systems at an outdoor event.

The measurements need to be as accurate as possible and I will need to record the measurements accurately.

 

Having looked on google I have found the Pulsar Model 33. This looks like the bit of kit I'm after. It is very expensive.

Does anyone have any experience with Pulsar meters?

 

I have also looked at a Phonic PAA3 it is much cheaper but doesn't have the recording features. (Not sure if it's type 1 or 2)

 

Any other suggestions or advice?

 

Thanks

[Mr.Si]

Hi Squarewave,

 

What is your budget?

 

I've heard good comments from people on here about the Phonic PAA3 in past topics to do with SLMs. (You may wish to do a search or two)

 

At the company I work for, we use a variety of SLMs for our jobs such as some old skool Castle GA120 and GA123 meters (they're kinda breaking), some Rion NL18 and NA27 meters (Also quite old) and some Norsonic 118 and 140 meters. We also have a Notebook Computer based one which was made by AcSoft.

 

Do you need to measure 1/3 octave or 1/1 octave band frequencies or are you just interested in a single figure reading such as A weighted values?

 

I've never heard of Pulsar, I shall go look on :google: ...

 

...Ok, had a look and that seems quite well specified, it's class 1 (so type 1 and type 0), it logs, it does both 1/1 and 1/3 octave bands, it stores quite a lot of data, it'll do percentiles (L90 for background measurements, for instance), it'll do SELs (sound exposure levels (aka LAE)). I can't see Leq mentioned, but I'm presuming that's what LXt means... How much is it?

[Simon Lewis]

Squarewave,

 

The PAA3 isn't even a type 2, and isn't an integrating meter. The type 1 Pulsar you mentioned has pretty much all the features of a good quality, modern SLM. It also has an associated price tag of £4100 + VAT. In fact, a good Norsonic might be cheaper!

 

I would suggest that you contact Campbell Associates or Gracey Associates and hire the meter. Furthermore, if your only experience is with the Maplin unit, might I suggest you spend some time with a good book or training package that explains what are the various indices that you can measure, and how the meter should be calibrated and operated.

 

Might I ask what do you have to measure? If it is sound level measurements for environmental impact purposes, then this is the type of kit you need. If you are comparing the sound systems themselves, forget the SLM and buy Smaart or EASERA.

 

Simon

[squarewave]

Hi Squarewave,

 

What is your budget?

 

I've heard good comments from people on here about the Phonic PAA3 in past topics to do with SLMs. (You may wish to do a search or two)

 

At the company I work for, we use a variety of SLMs for our jobs such as some old skool Castle GA120 and GA123 meters (they're kinda breaking), some Rion NL18 and NA27 meters (Also quite old) and some Norsonic 118 and 140 meters. We also have a Notebook Computer based one which was made by AcSoft.

 

Do you need to measure 1/3 octave or 1/1 octave band frequencies or are you just interested in a single figure reading such as A weighted values?

 

I've never heard of Pulsar, I shall go look on :google: ...

 

...Ok, had a look and that seems quite well specified, it's class 1 (so type 1 and type 0), it logs, it does both 1/1 and 1/3 octave bands, it stores quite a lot of data, it'll do percentiles (L90 for background measurements, for instance), it'll do SELs (sound exposure levels (aka LAE)). I can't see Leq mentioned, but I'm presuming that's what LXt means... How much is it?

Hi Mr Si, thanks for your reply.

 

I don't know how much the Pulsar Model 33 is. I found a price for another Pulsar that didn't have the spectrum analyzer, that was £2,500 including the calibrator.

 

After I posted this topic last night I did search the forum (should have done this first) The previous topics were very helpful.

 

My budget is not very big. I want to spend £200 - £300 so the Phonic would probably be the one but it doesn't have internal memory.

The internal memory would be very useful so I don't have to write down the measurements but I can write them down if I have to.

I don't need it to be a spectrum analyzer but it would be very useful.

 

I'm not sure exactly which features I really need this is why I have asked for advice. I think I need Leq but I don't know what all the other measurements are.

 

Maybe it would help if I say exactly what the job is.

 

I'm comparing the efficiency of six different PA systems. The smallest will be about 5kw rms and the largest will be about 30kw rms.

I will be comparing the input power to output power ratio of the speaker cabs. I will be measuring the input in kw rms and the output in dB SPL.

 

I will be using the printed 'sales' specs to choose the systems to begin with but I feel that the only way to be sure which one is the most efficient is to measure the spl output of the systems

 

With my budget I probably won't be able to get one that is accurate enough, so I have decided it's probably best to hire a type 1 with internal memory.

 

Thanks,

 

Squarewave Dave

 

A concurrent post has been automatically merged from this point on.

 

Squarewave,

 

The PAA3 isn't even a type 2, and isn't an integrating meter. The type 1 Pulsar you mentioned has pretty much all the features of a good quality, modern SLM. It also has an associated price tag of £4100 + VAT. In fact, a good Norsonic might be cheaper!

 

I would suggest that you contact Campbell Associates or Gracey Associates and hire the meter. Furthermore, if your only experience is with the Maplin unit, might I suggest you spend some time with a good book or training package that explains what are the various indices that you can measure, and how the meter should be calibrated and operated.

 

Might I ask what do you have to measure? If it is sound level measurements for environmental impact purposes, then this is the type of kit you need. If you are comparing the sound systems themselves, forget the SLM and buy Smaart or EASERA.

 

Simon

 

Hi Simon, thanks for your reply.

 

£4,100 is way out of my price range. I will look at a Norsonic but I think you are right about hiring one.

 

I will take your advice about the good book or training package, can you suggest a good book or training package or point me in the right direction?

 

I am comparing the efficiency of the speaker cabs themselves so I will look into Smaart or EASERA.

 

Thanks again,

 

Dave

[Simon Lewis]

Dave,

 

The Phonic does have (limited) memory and does come with a USB lead and software. I can't remember whether it allows you to save to PC in real time.

 

Bruel & Kjaar have some online seminars that you can sign up to.

 

With regards to your test requirements, class 1 isn't too necessary. In fact, it will be pretty hard to make any really meaningful measurement unless you are outdoors or have a very big anechoic chamber!

 

You will have a phenomenal range of parameters to set up and optimise in order to make any meaningful comparison. Might I suggest you get a copy of McCarthy's "Sound Systems: Design and Optimisation"? There's lots of good stuff there on how systems fit together, and why it's hard to directly compare a few 90x40 degree boxes on sticks with a few coupled 90 x 15 degree line array elements.

 

Lastly, I appreciate that specs alone are not always enough, but the manufacturer should provide data which is truthful, and you should be able to look at EASE data online.

 

Simon

[Stan Hope-Streeter]

<<I'm comparing the efficiency of six different PA systems. The smallest will be about 5kw rms and the largest will be about 30kw rms.

I will be comparing the input power to output power ratio of the speaker cabs. I will be measuring the input in kw rms and the output in dB SPL.

 

I will be using the printed 'sales' specs to choose the systems to begin with but I feel that the only way to be sure which one is the most efficient is to measure the spl output of the systems

 

With my budget I probably won't be able to get one that is accurate enough, so I have decided it's probably best to hire a type 1 with internal memory.>>

 

 

 

I'm sorry to say you may be barking up the wrong tree here.

 

- Trying to measure the input of a multi-amplified loudspeaker system in "kW RMS" would be a major, specialized scientific project.

 

- Such systems are not rated in kilowatts RMS anyway, except by wanna-bees and inexperienced dj types.

 

- Loudspeaker efficiency (as it appears on the spec sheet) is actually measured in terms of a voltage input relative to a measured spl at a known distance. Even that figure is never truly accurate in power terms because it is based on a "nominal" impedance figure for the speaker, rather than a real power input measurement.

 

- Sound level meters of the types you describe are the wrong tools for this job. They are designed for environmental noise measurement.

 

- Any figures you measure will depend on the directional characteristics of the speakers, including the interference patterns created by noncoincident sources, relative to the location of your measuring devices.

 

- A simple dB SPL measurement will not indicate the output power of the speaker.

 

- To measure the actual acoustic output of a complete speaker system you will need a reverberation chamber rather than a space outdoors. And an appropriate, non-destructive, test stimulus.

 

- What type of input signal are you proposing to use for these measurements?

[Simon Lewis]

- To measure the actual acoustic output of a complete speaker system you will need a reverberation chamber rather than a space outdoors. And an appropriate, non-destructive, test stimulus.

 

I was thinking of "Determination of sound power levels of noise sources using sound pressure - Survey method using an enveloping measurement surface over a reflecting plane" in the absence of a reverb chamber!

[squarewave]

You will have a phenomenal range of parameters to set up and optimise in order to make any meaningful comparison. Might I suggest you get a copy of McCarthy's "Sound Systems: Design and Optimisation"? There's lots of good stuff there on how systems fit together, and why it's hard to directly compare a few 90x40 degree boxes on sticks with a few coupled 90 x 15 degree line array elements.

 

Ok, so it might not be as straight forward as I was thinking. I will read the book on design and optimization, thanks.

 

I know it's hard to compare box's on sticks to coupled line array box's.

 

Two of the systems I want to compare are, 8 stacks of Turbosound Aspect with a Martin Audio W8LC system of similar size (4 box's per side).

 

The specs say that the Aspect system will produce 146dB peak from one cabinet. The Martin system will produce 135dB peak from one cab.

I want to know how they will perform when they are coupling together. I will be comparing the sound quality, the coverage and SPL.

 

Both of these systems will be running from the same brand of amplifiers. My plan was to measure the input power to the amps with a watt meter on the power distro. This will give me the total input power to the amps, then I will measure the output of both systems at the same distance.

 

My main concern is comparing these two systems and one other system. The other three smaller systems are not so important but I will compare them if I can.

 

Thanks,

 

Dave

 

A concurrent post has been automatically merged from this point on.

 

- Trying to measure the input of a multi-amplified loudspeaker system in "kW RMS" would be a major, specialized scientific project.

 

- Such systems are not rated in kilowatts RMS anyway, except by wanna-bees and inexperienced dj types.

 

- Loudspeaker efficiency (as it appears on the spec sheet) is actually measured in terms of a voltage input relative to a measured spl at a known distance. Even that figure is never truly accurate in power terms because it is based on a "nominal" impedance figure for the speaker, rather than a real power input measurement.

 

- Sound level meters of the types you describe are the wrong tools for this job. They are designed for environmental noise measurement.

 

- Any figures you measure will depend on the directional characteristics of the speakers, including the interference patterns created by noncoincident sources, relative to the location of your measuring devices.

 

- A simple dB SPL measurement will not indicate the output power of the speaker.

 

- To measure the actual acoustic output of a complete speaker system you will need a reverberation chamber rather than a space outdoors. And an appropriate, non-destructive, test stimulus.

 

- What type of input signal are you proposing to use for these measurements?

 

I will be measuring the input power in watts RMS using a watt meter that is on the power distro. This will tell me exactly how much power the amps are using.

 

I am not a wannabe, or an inexperienced dj type but I do rate systems in kw rms. How should I be rating systems? Peak power? Voltage?

 

What about measuring both systems outside from 5 meters away from the stack, will this give me an accurate comparison?

 

Is there a better way to do this and what are the right tools for the job?

 

I will be testing the systems with the same program material. I will test them with music and then with some tones generated by a tone generator.

 

Dave

[Simon Lewis]

Dave,

 

it may be a little pedantic, but Wrms is technically a misnomer. For resistive systems, the average power is equal to rms voltage x rms current. Because the efficiency and sensitivity of loudspeaker systems can differ so much, many systems are categorised by their maximum acoustic output, rather than the maximum average power that can be put through them before they overheat.

 

I suspect that the type of wattmeter used on most distros won't be accurate enough to properly measure the current, especially on a changing load such as music. Furthermore, it probably won't measure reactive power.

 

If you are wanting to measure efficiency, then that is the percentage conversion of electrical power into acoustic power. Therefore, you would have to determine the total power output of the speaker system, which means measuring inside a reverberation chamber, or using the survey method where you measure sound pressure level at multiple points over the surface of a (large) hemisphere and obtain a SWL figure from that.

 

Measuring outdoors can introduce a number of other problems (surface reflection, background noise etc.), and a variation in sound pressure may equate to different dispersion charatectistics, rather than an intrinsic difference in efficiency.

 

Perhaps comparing specs, looking at plots on the online EASE viewer and carrying out listening tests would be a better route to take?

 

Simon

[squarewave]

Dave,

 

it may be a little pedantic, but Wrms is technically a misnomer. For resistive systems, the average power is equal to rms voltage x rms current. Because the efficiency and sensitivity of loudspeaker systems can differ so much, many systems are categorised by their maximum acoustic output, rather than the maximum average power that can be put through them before they overheat.

 

I suspect that the type of wattmeter used on most distros won't be accurate enough to properly measure the current, especially on a changing load such as music. Furthermore, it probably won't measure reactive power.

 

If you are wanting to measure efficiency, then that is the percentage conversion of electrical power into acoustic power. Therefore, you would have to determine the total power output of the speaker system, which means measuring inside a reverberation chamber, or using the survey method where you measure sound pressure level at multiple points over the surface of a (large) hemisphere and obtain a SWL figure from that.

 

Measuring outdoors can introduce a number of other problems (surface reflection, background noise etc.), and a variation in sound pressure may equate to different dispersion charatectistics, rather than an intrinsic difference in efficiency.

 

Perhaps comparing specs, looking at plots on the online EASE viewer and carrying out listening tests would be a better route to take?

 

Simon

 

Thank Simon, your very helpful.

 

I'm not inexperienced but I do have a lot to learn. That's why I'm on this forum talking to you guys.

 

The reason I referred to a system as '30kw rms' is because that is the output rating on the amps that will be powering the system. I understand that means very little but when I'm going to measure all the other perametres I don't know how else to catagorize a system.

 

I don't know much about the watt meter on the power distro. There is an electrician that will be measuring the power supply. The input power is his side of the job and the output is my side.

 

The percentage conversion of the electrical input power to acoustic output power is exactly what we are measuring.

 

Having talked to you guys a little I now see that it is a much more complicated job than I first thought it would be.

I can see why a dB meter is not the tool for the job and having looked at Easera software that would be a much better tool.

 

I need to measure SPL output and coverage and I will compare the sound quality of the systems.

 

I understand what you are saying about measuring the systems in a chamber rather than outside.

If I measure the systems at the event then the results will only be relevent to that event, which is perfect for the job we are doing.

 

The performance of the systems at the event will also depend on the skill of the sound engineers that have set up each system. This is all relevent to the job I'm doing.

 

I have to measure the systems at the event because it is the event that is commissioning me to do the work.

I will give them a written and graphical report of my results. Which will be made much easier by Easera.

 

You are right about using the EASE data and specs but I still need to measure the systems at the event as well.

 

I have always planned to use manufacturers specs in my report but the specs will not tell me exactly how the systems will perform at this particular event.

 

I need to produce as much information as I can.

 

Thanks again, you have been very helpful.

 

Dave

[DJ Teknovibe]

Squarewave Wrote :

The specs say that the Aspect system will produce 146dB peak from one cabinet. The Martin system will produce 135dB peak from one cab

 

You've got to remember to take 6db off the peak figure and that gives you the rms output figure, so it would be 140db maximum with the rms amount of power put into that speaker. You never listen to peak ratings because thats a rating which is for about 1ms and only allows for peak transiens and doesn't show you the output you'd be getting when you put the rms rating into the speaker. Then, to give you a rough idea of how much extra volume you'll be getting from coupling, you add 3db everytime you double th amount of speakers. It not an exact figure but gives you a pretty good idea. So with a single Aspect speaker you'll get 140db output (according to the specs), then if you add another you'll get a 3db increase which will take the total output to 143db, then add anoher 2 speakers (doubling the amount of speakers you have coupled) you get another 3 db,then from 2 having speakers when you double the amount of speakers to 4 speakers, you add another 3. Like I say this is a rough guide but gives you SOME idea of how much spl you'll probably get from a speaker system.Plus if you've the speakers against a back wall you can add another 3db because then you'll be using the speakers in half space. And if you have the speakers in a corner, then you add another 3db because then it would be quarter space. This 3db boost when the speakers are in half space only really applies to the lower end of the frequency range, below about 250hz.

[squarewave]

Thanks Tekno.

 

I know the difference between rms and peak power.

 

I can calculate the specs but that doesn't tell me exactly how the speakers will perform when they couple up with each other. I expect the Martin system to couple better because it's a Line array but the Aspect system has Polyhorns so it might couple up better than a traditional point source cab.

It also doesn't tell me how they will perform in the environment that they will be in at the event.

 

to give you a rough idea of how much extra volume you'll be getting from coupling, you add 3db everytime you double th amount of speakers.

 

When you double the power you get a 3dB increase and when the drivers couple together you get another 3dB increase. That makes +6dB for drivers that are coupled.

 

I don't want a rough idea, I want an exact measurement.

 

Thanks

[Simon Lewis]

- Peak ratings are useful, we may well want to know the short term power capability of the system. We tend to listen to material with a high peak to mean ratio, not sine waves...

- as stated before rms power is a misnomer

- Coupling is useful, but the larger the array, the more likely that interference will oocur.

- LF speakers on a floor already radiate into half space...

- by the time you are considering maximum output power ratings, you can say goodbye to small signal conditions and hello to amplifier and loudspeaker distortion

[Simon Lewis]

One other thing - pertinent to both the OP and others who made comments about maximum output -

 

The current drawn when the system is reproducing speech and music at high levels can be as little as 1/10th of the theoretical maximum current draw. Conversely, testing speakers at full amplifier output power using sine waves (or even pink noise) can cause amplifier protection circuits to trigger or loudspeaker damage. Some amps we've played with won't sustain a sine wave signal at maximum sensitivity for more than a few seconds before going into protect.

[javier53]

Hi, I'm looking for advice on which dB meter to buy.

 

At the moment I have a £40 Maplins special (Type 2). Accurate to ±1.5dB. A/C weighting. 30 - 130dB range.

 

I have a job next year, for which I will need something more professional.

 

I need to measure and compare six different systems at an outdoor event.

The measurements need to be as accurate as possible and I will need to record the measurements accurately.

 

Having looked on google I have found the Pulsar Model 33. This looks like the bit of kit I'm after. It is very expensive.

Does anyone have any experience with Pulsar meters?

 

I have also looked at a Phonic PAA3 it is much cheaper but doesn't have the recording features. (Not sure if it's type 1 or 2)

 

Any other suggestions or advice?

 

Thanks

 

http://www.industrial-needs.com/measuring-instruments/images/Noise-meters-view.jpg

Hello I have seen this web: http://www.industrial-needs.com/measuring-...oise-meters.htm

 

This device (class II) price nearly to 100 €

 

http://www.pce-group-europe.com/espanol/images/imagen-ficha-tecnica/medidor-sonido-pce-322a.jpg

• RS-232 cable to transmit data
  
• Software compatible with Windows 95, 98, 2000 and XP
  
• Internal memory for 32,000 values
  
• Minimum and maximum functions
  
• Resolution of 0.1dB
  
• 35mm LCD display with graphic divisions of 2dB (unto 100dB)
  
• Frequency weighting: A and C
  
• Frequency range of 31.5 Hz to 8 kHz
  
• Temporary value for pulses, fast and slow
  
• Real-time clock with calendar
  
• ABS enclosure
  

• 1/2" Electret condenser microphone