Speaker Stories

Choosing New Speakers: What Information Is Helpful? Part One

Issue 147

Impedance. Signal to noise ratio. Driver size. Flatness of frequency response (or deviation from it). Sensitivity rating in dB. Cabinet size. Off-axis response. Power-handling capability. There are many considerations in speaker design and performance. Understanding more about all of these factors can assist us in making the best decisions regarding what speakers to buy when parting with our cash. And let’s not forget that minor little chestnut of an idea: ultimately, how good does it sound?

In this series, we’ll consider some of these factors and how they relate to real-world speaker evaluation. Seasoned audiophiles may be familiar with some or all of what we’ll be talking about, while other readers may find this information novel and enlightening.

Sound pressure level, or SPL, is literally the pressure level of a sound, which corresponds to volume, and is expressed in decibels, or dB. However, a more useful speaker specification is sensitivity, an indicator of how loudly a speaker will play at a given input of power. It’s expressed in dB and the higher the number, the louder a speaker will be when fed the same amount of power.

Typically, sensitivity is measured by driving one watt of power into an 8-ohm speaker at 2.83 volts, with the dB level measured from a distance of one meter. However, the rating by itself is only a rough indicator. Speakers are rated with an impedance spec, familiar to most of us, which is an indicator of how difficult the speaker is to drive. However, speakers don’t have the same impedance at every frequency – their stated specs are for a nominal impedance, but this can go higher or lower depending on the frequency the speaker has to reproduce.

That said, the industry standard of one watt into 8 ohms at 2.83 volts is a beneficial constant because it enables us to compare graphs of how the impedance of different speakers vary with frequency, and how their frequency response can be related. Because the impedance curves of various speakers can be so different, sometimes even within a given pair of drivers of the same model from the same manufacturer, having the consistent industry-standard “control” parameter of measuring sensitivity, gives you a baseline, and the ability to compare different speakers’ impedance and frequency response curves.

Also, some power amplifiers can handle lower impedances better than others. If an 8-ohm-nominal speaker dips to 4 ohms or lower impedance at some frequencies, your power amp or receiver may or may not be able to handle it (because it’s trying to deliver more current than it’s designed for), especially at higher volumes. Check your component’s power output specs to make sure.

That brings us to another consideration: an amplifier or receiver’s given power rating may not be particularly enlightening. The way manufacturers state their power ratings may not be consistent. You’ll see ratings like RMS power, peak (or instantaneous) power, average continuous power and others, and typically, the measurements will be taken when feeding the amp, a 1 kHz test signal, not music (with its full frequency range). However, none of these may equate to the optimal listening output you will enjoy at that power. It may not even fully reveal the actual headroom in power that the speaker system as a whole will be good for.

Historically, some manufacturers will provide the peak power rating of the speaker as its nominal power-handling rating, but won’t tell you that this is in fact just for a peak at one or a few frequencies. So, you have no clue as to the speaker’s real-world power-handling capability, or the range of volume levels and frequencies where the speaker performs at its best. I have personally experienced this with car power amp ratings being significantly exaggerated, both at peak music power output ratings and with RMS ratings. In other words, if you were provided with a wider set of information about the breadth of the bandwidth that a speaker operates at comfortably in terms of its impedance at different frequencies, and its true peak power handling capability, you’ll get a clearer idea of how well the speaker will reproduce the dynamics and pulses of your music. Many speaker manufacturers will provide an impedance-vs-frequency curve, and be forthright about their speakers’ power handling.

 

A loudspeaker impedance vs. frequency graph. From the Aperion Audio website.

A loudspeaker impedance vs. frequency graph. From the Aperion Audio website.

 

Power ratings will obviously also vary according to the physical size of the speaker driver. If you are running a ten-inch driver it will require a different amount of power for its range of excursion. Generally speaking, more power will be required to move its greater physical mass back and forth compared to a 5.25-inch driver. Also, a smaller speaker will require more power to be as perceivably loud as a larger one. As the driver’s power requirements are different, so too, the maximum ability of the mechanical pistonic action of the driver will have a great influence on its maximum power handling and its peak output.

Other factors to consider are the speaker’s size, and your listening distance. Measuring a large speaker’s output at 1 meter will not give as meaningful a specification as measuring a smaller speaker at the same distance. That’s because I’ll bet you never listen to larger speakers that close up – but you might very well listen to smaller speakers at a distance of 1 meter, or closer. And of course, the farther away you are from your speakers, the louder they’ll have to play to deliver the same perceived volume as if you were closer. Some companies will take a measurement of a larger speaker at a greater distance than one meter, and then re-calculate what the sensitivity would be at one meter at 2.83 volts for the standardized and expected specification listing.

For those of us who own receivers with built-in room correction, we often just settle for having its processor accommodate for our set up of each speaker’s distance (and possibly frequency response) from our listening chair, and don’t have to think about any of this. But, wouldn’t it be nice to know as much as possible about how a speaker performs when looking at what to buy?

Some speaker manufacturers provide a range of optimum listening distances for a particular model, and this is very insightful piece of information, particularly for those with either significantly more or less cubic volume of listening space than average. Forgive me for sounding like Captain Obvious here, but when considering your potential speaker purchase, you likely have in mind the room that you will install them in, but the manufacturer, especially for something like a portable low-cost Bluetooth speaker, may have had considerations other than room size in mind. I wonder how many of even the most hard-core audiophiles have consulted the speaker manufacturers’ information on optimal room size compatibility, even when having a bespoke music room built. Although, to be fair, some manufacturers do offer appropriate product selection tools, such as REL’s recommended subwoofer selector, which allows you to enter a speaker model and room size and then comes up with a recommended subwoofer model.

How loudly do you want to listen to your speakers? You may find that typical listening volumes of 75 to 85 dB will suit you perfectly for most occasions, with occasional forays to 88 dB, for example. So, when you audition different speakers, it may be a good idea to measure them at the volume (and distance) you will actually be listening to them for the majority of the time, while using a dB meter or even a spectrum analyzer app.

One example is a very basic but effective Google Play app called Sound Meter. It provides a dB meter readout, and a list of familiar sounds and their typical dB levels, from quiet rustling leaves at 20 dB to a normal conversation at 3 feet (60 dB) right up to rock music or a screaming child at 100dB, and beyond (a Saturn V rocket launch registered 204 dB!). The app gives you some basic bearings to steer by as you measure your room at your seating position. It provides a graph mode and also a simple but functional dial display. Although it’s not the most accurate tool in the world, it will probably suffice for the testing purposes described above. In my own experience I have found it quite consistent. There are many other Android and iPhone apps available.

 

The Sound Meter Level app from SOFDX.

The Sound Level Meter app from SOFDX.

 

This can also provide you with some consistency in your comparisons when auditioning speakers, as you of course also listen for the musicality of the stereo speakers you’re evaluating. You may surprise yourself at just how quietly you enjoy listening to a well-set-up system.

We will consider the effects of the listening room more in Part Two, as it relates to sensitivity ratings and power output.

Header image courtesy of Pixabay.com/Tomislav Jakupec.

9 comments on “Choosing New Speakers: What Information Is Helpful? Part One”

  1. Good morning Mr. Welton!
    Perhaps maybe, you can shed a little light on this for me.
    For years, I have been readingg reviews about speakers in both Sound And Vission, and Stereophile magazines.
    The one thing that they don’t tell you about both passave and active speakers, is the power handling capabilities.
    And active speakers, the information that’s usually left out, is how much power the built in amps are supplying to the drivers inside of the speaker cabnets.
    The only ones that you get the power specs on, are usually powered subs.
    My question is, how come reviews leave that information out.
    If people like me that subscribe to these magazines, shouldn’t reviewers include that information right along with the speakers that they’re reviewing so that people can make informed cecitions about the products that they’re thinking aboutt buying?
    Thanks!

  2. John, There are several reasons max power handling of speakers is left out, the major one is that power is rated as well as delivered very differently from different amplifiers. Amp A may be rated at 40 watts per channel with 1/10 of a % or less of distortion full bandwidth , while Amp B may be rated at 100 watts at 1% distortion at 1K . So from a starting point its pretty tough to compare. Amp A likely also makes 100watts rated with 1% distortion, but since the company that makes amp A realizes 1% distortion is a lot, they would never to rate their power that way.
    The speaker company would need to know exactly how the power is delivered and at what level of distortion it has to rate its power handling. Then there is the possibility your source, and media can induce some level of distortion. There are just too may variables. I assume your asking because you would like the ability to play the speakers loud from time to time? I was in the business for over 40 years and my best advice would be to forget about power handling, and trust your ears. If the music sounds clean and clear play it loud! There will be a point at which you hear the distortion from either your amp or the speakers, at that point back off!
    You just discovered your speakers max with your amp…
    Moral of the story is, if you want to play your music loud, buy sensitive speakers 95DB or higher.
    If loudness is not a thing, then max power handling becomes moot.

    1. Good afternoon [email protected]!
      Ok, I understand that.
      I have mostly vacuum tube audio gear in my home.
      Most of it, is vintage.
      But what I understand about tube amps, one tube watt, can equal to three transistor watts.
      Meaning, a 40 watt tube amp, is cranking out 120 transistor watts.
      So, ya, I get that.
      And a class A amp won’t deliver power to a speaker, the same way that a class AB amp will.
      Just like a class AB amp, won’t deliver power to a speaker, the same way a class D amp will.

  3. Dear Mr Price,

    Thank you for reading the article and providing a great question!

    It’s true to say that manufacturers generally don’t produce power rating information largely because it depends where in the signal path the measurement should or could be taken for best marketing value.

    The greater issue to a large extent is the fact that there has not been industry-wide comprehensive adherence to a singular strict benchmark or standard. Another factor is how long may a given speaker or subwoofer produce that rated power for; if it is for a short term burst at a given frequency, or for a more prolonged period of time.

    An example may be that someone may read a given rating for their speakers maximum power output and then play a full bandwidth signal through their system at maximum power and blow up their speakers. This highlights the limitation or effectiveness of peak power information.

    Even though there are some industry standards in place, nominal values often will not represent the optimal room size that they may be played in in a domestic product compared to perhaps industrial applications.

    It’s safe to say that you are better off having more power and sensitive enough speakers that may play in a given cubic area as opposed to pushing an amp into clipping and causiong unwanted distrotion or damage to your equipment.

    There are however, pioneering new standards which serve to both represent effective power as an expression of deviation from maximum output. This can be calculated at relatively low volumes and be indicative of how loud a speaker may actually go.

    Please keep listening for a coming article in this series where I go on to discuss this in more detail, and how it is possible to test your personal speakers for this information.

    Thanks again for reading and within this series I will help identify more about how to identify just what a your speakers are capable of, without running the risk of damaging your gear. Like many of us, the last thing we want is a burst in output from our source material causing distortion at any volume level, let alone if it is above 75dB.

    Kind regards,

    Russ

    1. Good afternoon Mr. Welton!
      I ordered a quod of Avantone Pro CLA-10 Studio Reference Monitors last year.
      I also picked up a Avantone Pro CLA-100 Studio Reference power amp.
      The monitors according to the Avantone Pro website, are rated at 60 watts RMS, and 120 watts max in to an 8 ohm load.
      But Avantone Pro, for their active monitors witch they call, their CLA-10A, they put 200 watt plate amps in those.
      But if the passive monitors can only handle a max input of 120 watts, what is the reason for using an amp that’s 80 watts over that?
      Thanks!

  4. Good afternoon Mr Price!

    Thank you for your question.

    Part of the reason for high power amplification is that a lot of source material may produce a dynamic range in dB greater than the typical range of a domestic speaker when factoring in bursts or peak output.

    This is ever more critical for sonic integrity with monitor speakers so that the audio signal is both as clean as possible and something that will not push the amplifier to clipping or distorting the waveform.

    A higher powered amplifier will usually cope far better with sustained bursts than something that only matches speaker nominal peak output. This extra headroom is very desirable for better signal clarity not just for casual listening but is required for studio quality work.

    I hope this is helpful John, and that you enjoy my coming articles on the matter.

    Best regards,

    Russ

    1. Good morning Mr. Welton!
      This is something I’m currently thinking about doing.
      But sense you’ve been doing this probley before I was born, perhaps you can tell me if rather I’m moving in the right direction or not.
      I own two different amps.
      One is a 100 watt class AB transistor amp.
      The other one, is a 150 watt per channel class AB all tube amp.
      Occasionally, I have to use the stereo system in my living room, for remastering perpuses.
      But only, my current speakers don’t allow me to hear everything I need to hear, to make sure I’m getting the mixes right the first time around.
      My Avantone Pro/JBL setup in my bed room, does a way better job then my speakers in my living room does.
      And so, I’m thinking about replacing them, with a pare of JBL SRX-835 passive PA speakers.
      They go down as low, as 35HZ.
      But they go up as high as 35KHZ.
      The power requirements, are 1600 watts RMS, 3200 watts max, all in to a 4ohm load.
      The SPL, is 128DB.
      Would I need a 1600 to 3200 watt per channel amp to drive these speakers?
      Or, would my existing amps do the job for me.
      I don’t really need a whole lot of volume, I just need my speakers to allow me to hear what’s going on in my mixes.
      Thanks in advance!

  5. Russ,
    You touched on something that continually irritates me and that’s amp ratings. In addition to not giving you a number for output across the audible spectrum many manufacturers will give you a number that only represents one channel at a time and then deliver an amp that’s incapable of delivering their rated power across both channels at the same time. I think this little bit of subterfuge came about when home theater receivers with many channels became popular but too many “audiophile” manufacturers now use the same method of rating amps. The end result is often an amp that doesn’t perform to expectations.

    One thing you didn’t go into well was distortion figures for amplifiers. Run any amp close to it’s rated power and it will have more distortion (often a lot more) than if it’s running at half it’s rated power. If you want to listen with your amp providing 100 watts of power buy one capable of producing 200 watts and run it at half it’s rated power. You’ll get a lot less distortion that way. Call it headroom or whatever but it’s the best argument for buying a high power amp I know of.

    Great article, I’m looking forward to the next installment.

    Have a great day!
    OHT

  6. With solid state equipment (almost 100% of the time), dynamic transducers that are damaged/blown are from Over Driving the amps capabilities, causing severe distortion that quickly overheats their voice coils! Rarely are damaged drivers due to “too much clean power”! Tube amps actually are much more forgiving when over driven, as distortion characteristics are less severe, both in sound and damaged driver potential!

    If you go by the rule that music has 10db peaks over the “continuous sound level outputs” (many today say 20db or even 30db peaks), then at any given power amp continuous music output, you need 10X that power output to Safely Cover the 10db musical peaks without distorting the amps capabilities. Ex: for a 100W amp, the Maximum Continuous wattage output playing music is 10 Watts! This allows the 10db musical peaks to pull the 100 watts that the amp can safely deliver without severe clipping distortion. If you go by the 20 to 30db peaks rule (covers very dynamic acoustical music), then that power amp can only deliver 5 to 3 watts of clean continuous power to SAFELY cover the musical peaks!

    How do you prevent transducer damage…lower the volume, use more efficient speakers, setup into a much smaller listening room or get much higher output amps. But remember, going from 100 watts per channel to 300 watts per channel translates to Only 3db more clean overall output without distortion!! 😉

    Ted

Leave a Reply

Also From This Issue

This Year’s Model

Stream of Consciousness: Better Sound From My Computer Audio, Part One

As something of a musical magpie, I have always been…

Pretenders: The Real Thing

On September 7, 2021, Chrissie Hynde turned 70 years old.…

Octave Records Releases its First Vinyl LPs

PS Audio’s Octave Records is proud to announce its first…
Subscribe to Copper Magazine and never miss an issue.
Stop by for a tour:
Mon-Fri, 8:30am-5pm MST

4865 Sterling Dr.
Boulder, CO 80301
1-800-PSAUDIO

Join the hi-fi family

Stop by for a tour:
4865 Sterling Dr.
Boulder, CO 80301

Join the hi-fi family

linkedin facebook pinterest youtube rss twitter instagram facebook-blank rss-blank linkedin-blank pinterest youtube twitter instagram