Understanding Speaker Frequency Response – TheTopDailyNews

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Observe: Paul Dicomo was a wonderful pal to eCoustics and many individuals over the earlier 2 a few years. Sadly, Paul misplaced a courageous battle with most cancers in 2021 and the commerce misplaced a wonderful man who taught a period of audio/video journalists the easiest way to understand the merchandise that we cowl.

Paul contributed loads of fantastic articles over time and we hope {that a} new period of readers finds good value in his writing.

By Paul Dicomo

The Secret Behind The Enterprise’s Most-Cited Spec.

Proper right here’s a quick quiz: which of these two audio system sounds greater: Speaker A with a frequency response fluctuate of 45Hz to 18kHz or, Speaker B with a variety of 20Hz to 25kHz? The truth is there’s merely not enough information in these numbers to know one thing of value. Taken out of context and with out completely different information, a straightforward set of numbers don’t let you understand so much about precise world sound top quality. Nevertheless people make audio searching for selections based mostly totally on printed specs, such as a result of the frequency response spec, frequently. I’d want to demystify the tactic for you; let you in on just a little bit commerce secret about “The Frequency Response Spec.”

My Frequency Response

The Frequency Response specification makes an try to clarify the fluctuate of frequencies or musical tones a speaker can reproduce, measured in Hertz (recognized to old-timers as “Cycles per Second”). The fluctuate of human listening to is often regarded as being from 20Hz, very low bass tones, by way of 20kHz (20,000Hz), the very highest treble. Presumably a speaker which may reproduce that change would sound lifelike. Alas, it’s no guarantee. An necessary determinant of a speaker’s frequency effectivity shouldn’t be its width or fluctuate, nevertheless whether or not or not it’s in a position to reproducing all the audible frequencies on the same amount at which that they had been recorded.

You don’t want the speaker to fluctuate the “mix” of tones; which may harm the timbre of voices and gadgets, making them sound unnatural. Ideally, you want the sounds which is likely to be on the recording to be reproduced as that they had been recorded, with out the speaker altering the sound. To say it one different method: do you have to made a recording of all the audible tones on the same amount and carried out that recording by way of a speaker, you’d want all the audible tones to return again out on the same amount. The reality is, that’s a technique of measuring audio system. An indication that’s comprised of all frequencies at equal amount is fed proper right into a speaker that sits in a room with no reflective surfaces. A calibrated microphone is positioned in entrance of the speaker and feeds the speaker’s output proper right into a machine that plots the frequency vs. amplitude as confirmed in Decide A.

frequency vs. amplitude
Decide A

Now take a look at the graph in Decide B. That’s the frequency response of the Erehwon Model 10, with drivers and tweeters manufactured from pure Unobtainium (“Half the carbs, all the sound!”). The flat line on the graph signifies that the speaker is “flat”; it reproduces all the musically associated tones on the same amount. That doesn’t indicate {that a} “flat” speaker will play all recorded sounds on the same amount — bear with me proper right here — it signifies that it’ll cope with all sounds equally; it acquired’t impose its will on the music nevertheless will allow you to listen to the music as a result of it was recorded. Flat is sweet. Flat response implies that the speaker reproduces sound exactly.

Erehwon Model 10
Decide B

Too harmful that the Erehwon Model 10 doesn’t really exist, and neither does Unobtainium. At the moment’s utilized sciences allow speaker designers to get nearer to the “flat” supreme than ever sooner than, nevertheless they nonetheless fall far wanting “perfection.” So if a frequency fluctuate spec shouldn’t be sufficient, what’s?

Frequency Response In Context

A large enchancment is usually a frequency response amount that moreover accommodates the amplitude tolerance, expressed as “XHz-YkHz +/- 3dB.” This tells you that the amplitude of the speaker’s response relative to frequency doesn’t deviate higher than 3 Decibels from the center line. The “plus or minus 3dB” spec is regarded as an unusual of sorts. The thought is that 3dB variations are “merely perceptible,” so a speaker whose response curve lies inside that tolerance window is a reasonably right speaker. Let’s see if that idea holds water.

speaker frequency response
Decide C

Take a look at Decide C. This speaker has response that could be specified as 20Hz-20kHz +/- 3dB. Take a look at Decide D; it, too, can have the exact same specification as Speaker C! Do you suppose they’ll sound associated? NOT! They acquired’t sound even remotely like one another. Speaker C could have “one discover” bass and might make voices and completely different gadgets sound unnatural, nevertheless Speaker D will sound straightforward and further pure.

speaker response curves
Decide D

If I needed to determine on strictly by the response curves, I’d choose speaker D on account of its amplitude variations are smoother and gentler. In distinction, speaker C’s amplitude variations are additional extreme and “spikey.” Experience has confirmed speaker designers that these quick changes in response produce a sound that’s additional fatiguing, a lot much less pleasing and subjectively a lot much less right.

Industrial. Scroll to proceed learning.

smooth frequency response
Decide E

Now take a look on the response of the speaker in Decide E. This speaker reveals a straightforward response curve with low amplitude variations so that you just’d depend on a fairly pure sound; however, the bandwidth of these errors may very well be very broad, and experience has confirmed us that even low amount variations are audible within the occasion that they cowl a broad fluctuate of frequencies. On this case, Speaker E would have rich bass, excellent treble and be significantly recessed or “laid once more” inside the midrange. Audiophiles title this “The Smile Curve.” It’s not the fascinating trait it seems like but it surely certainly’s a very “sellable” trait to naive customers.

My Response To Frequency

Now that you just understand the importance (and limitations) of amplitude variations in frequency response graphs, you might ask: “does the frequency fluctuate inform us one thing the least bit?” Certain, it does. As long as you understand the amplitude tolerance (+/- 3dB), the frequency response fluctuate or width tells you methods extreme or low the speaker goes. A speaker rated as 20Hz – 25kHz +/- 3dB will play lower bass and higher treble sounds than a speaker that measures 40Hz – 20kHz +/- 3dB. I wouldn’t guess money that will probably be the upper, additional pleasing speaker, nevertheless on the very least I’d know one factor of value.

And now that you just know how to interpret these numbers, you’re in a position to run correct out and buy a speaker just by wanting on the response curve, correct? I wouldn’t counsel it. No matter many advances in experience over the earlier 20 years, frequency response measurement is an imperfect science. The equivalent speaker measured by two fully completely different labs may yield fully completely different response graphs. And some firms merely plain cheat after they publish response curves. If it appears hand drawn, it most probably was. (Certain, the graphs had been hand drawn for illustration capabilities.)

The Third Dimension
Up to now we’ve talked about frequency (the X axis of the graph) and amplitude (Y axis) nevertheless we ignored a necessary third dimension: time. When a speaker responds to an impulse, as an illustration a rim shot — “THWACK!” — it ought to start instantly and stop the second the instrument stops making sound. If the speaker retains vibrating or resonating and making sound after the availability sound stops it’s altering, or “coloring,” the sound of the distinctive recording. And that’s harmful.

Decide FDecide G
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Decide F reveals a bandwidth restricted impulse signal. You might even see that it begins and stops abruptly. Decide G reveals that exact same impulse coming out of a speaker. You might even see that the sound persists after the impulse enter has stopped — it resonates or “rings.” The speaker is altering the timbre or character of the distinctive recording. With a goal to see to what extent and at which frequencies the “ringing” is happening, we use an aesthetic computer algorithm referred to as MLLSA (affectionately referred to as “Melissa” by engineers who don’t date so much) to measure the response of a speaker in frequency, amplitude and time. Decide H is a MLLSA spectral decay graph of a prototype speaker. The third axis of this graph is time, so graph traces closest to you’re measurements taken later than these inside the once more. Contemplate it as a set of slices with each slice being a frequency response graph taken at a novel time restrict.

If we had been to measure the precise speaker the MLLSA graph would look like a straight line in once more with no traces in entrance. Precise audio system fall far wanting this supreme and proceed to resonate after an impulse has stopped, harking back to in Decide H. Decide I is a Polk LSi9, and we’re in a position to see that the speaker stops responding sooner inside the midrange than the speaker pictured in Decide H, indicating that the LSi9 is a higher sounding speaker.

Decide HDecide I
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Whereas no measurement methodology can completely describe the subjective sound of a loudspeaker, MLLSA and completely different frequency response measurements are of good help to Polk engineers in rising greater sounding audio system. Solely a fool would design a speaker based mostly totally on measurements alone and solely an entire fool would design a speaker primarily based solely on subjective listening. A speaker which can sound good on a selected recording may really be flawed – it might need what’s often referred to as a “euphonic coloration.” It may very well be pleasing to the ear beneath positive circumstances, but it surely certainly optimistic ain’t correct.

We use every measurements and subjective listening to design and think about audio system. The measurements save us time and are a wonderful help in pointing us within the acceptable design course, avoiding errors which can come once more to chew us later. The measurements give us a manner of selecting which experimental designs are worth listening to.

Nevertheless we have now now to be glad with the whole subjective experience sooner than a model new design turns right into a Polk Audio speaker. We spend quite a few hours listening to music and flicks. Quite a few expert listeners should be all ears to a proposed design and log off on the sound sooner than a model could even go into manufacturing. The Mission Supervisor, Strategies Engineer, VP of Engineering, Product Line Supervisor, and significantly Matthew Polk, all should agree that the prototype delivers the type of rewarding listening experience that you just simply depend on from Polk Audio.

What’s Your Frequency?

You now know the important thing: a frequency response specification is a very weak predictor of the actual effectivity of a loudspeaker. A frequency response chart will probably be additional helpful, but it surely certainly’s missing the important time measurement. You now know to seek for common curve smoothness and to steer clear of quick swings in amplitude. Some magazines and evaluation web sites publish MLSSA graphs of reviewed audio system, and now you’ll understand the easiest way to interpret them. Further power to you!

No matter how adept you is probably at deciphering frequency response information, it must solely be one information stage amongst many in choosing a speaker. There could also be so much additional to a speaker’s effectivity than merely its response – like its dispersion and imaging, dynamic fluctuate and component resolution along with dimension, cosmetics and worth. Looking at good frequency response information could allow you to eradicate audio system with obvious and obnoxious errors. Whenever you’ve eradicated the rise & tizz pseudo-fi audio system, chances are you’ll settle all the best way right down to cautious listening and making a additional educated different.

How Polk Specifies Frequency Response

Polk Audio publishes two frequency response specs: “Normal” and “-3dB.” “Normal” describes the frequency fluctuate limits of the speaker inside an amplitude drop off of 9dB. Any frequency reproduced higher than 9dB down from the rest of the frequencies will contribute little to the sound. The “-3dB” spec describes the frequency fluctuate limits of the speaker inside an amplitude drop off of 3dB.

Industrial. Scroll to proceed learning.

I merely wrote this huge article making the case that these kinds of numbers won’t be terribly useful in making searching for selections. So why does Polk use them? For greater or for worse, these numbers are the norm inside the audio commerce.

To not publish them would go away an impression that our merchandise weren’t aggressive. A higher question could be: why don’t we publish frequency response and MLSSA graphs together with the simple numbers? We actually really feel that these graphs wouldn’t be vital to the overwhelming majority of consumers.

It takes years of working with measurements and loudspeakers sooner than you get an excellent sense of how the graphs correlate to subjective sound top quality. Incorrect interpretation of graphs can merely lead to misinformation and harmful picks. Lastly, the variation in measurement methods may make evaluating graphs from two fully completely different labs or producers unreliable and misleading.

Paul Dicomo

By Paul Dicomo, Polk Audio – Promoting and advertising and marketing Supervisor

Initially Revealed: September 28, 2005

Further Articles by Paul Dicomo:

All You Should Know About Bass Administration

Residence Theater in a Discipline vs. Parts. Which is Best For You?

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