Calibrated Full-Range Studio Monitor Systems

[Surfwhammy]

[NOTE: I am using "you" in the general sense, and I fully realize that the information I am providing can be very annoying; but (a) it is accurate and (b) it is based on the rules of acoustic physics, hence (c) it is not my personal opinion or belief system. Explained another way, put a calibrated meter on it, and let the meter indicate the facts, which is the best way to do it, since meters have no personal opinions or beliefs. So long as a meter is properly calibrated and in good working order, it provides factual information, and this is the way science works . . . ]

The key bit of information is that it is very important to have a calibrated full-range studio monitor system, where as I define it, a "calibrated full-range" studio monitor system has a flat equal loudness curve running from 10-Hz to 20,000-Hz at 85 dB SPL, where the requirements I add are (a) that it goes subsonic to 10-Hz and (b) that it does this over the entire range (10-Hz to 20,000-Hz) at 85 dB SPL, where the reason for 85 dB SPL is explained later in this post, although some of the explanation is implied and requires studying the equal loudness curves (see below) and knowing that 85 dB SPL is at the practical upper limit of what normal human hearing can tolerate at least for a few hours each day without causing hearing problems or damage, which explained another way is the sound pressure level (SPL) that the conductor of an orchestra and the folks sitting on the front row typically enjoy, at least during the louder parts of songs . . .

[NOTE: The following drawing shows another way to represent a flat equal loudness curve, but instead of being literally "flat", it is curvy to emphasize the differences in volume levels required to attain equal loudness perception. There is another way to draw it where the curve literally is a flat horizontal line, and this is where the term "flat" originates in this context, which among other things is an excellent reason for musicians to stay awake in mathematics classes. This drawing shows the reason for what I call the "big and heavy" rule of acoustic physics, which specifically refers to reproducing subsonic and deep bass at equal perceived loudness to midrange notes at the "dip", which runs from approximately 2,000-Hz to 5,000-Hz, where the facts of the matter are (a) that reproducing subsonic and deep bass requires moving a lot of air and (b) moving a lot of air requires large woofers and powerful amplifiers, both of which are "big and heavy" physical and electromagnetic devices (magnets, transformers, cases and enclosures, woofer cones, metal frames, and so forth) . . . ]



The problem is that for all practical purposes there are no currently available commercial-off-the-shelf (COTS) calibrated full-range home studio monitor systems available anywhere on this planet, although with a bit of help from either (a) a Behringer DEQ2496 UltraCurve Pro Mastering Process and companion calibrated condenser microphone or (b) the ARC System 2 and its calibrated condenser microphone, it is possible to do the required calibrations for the approximately $7,500 top-of-the-line JBL home studio monitor system . . .

DEQ2496 UltraCurve Pro Mastering Processor (Behringer)

ARC System 2 (IK Multimedia)

[NOTE: Recently, JBL has regained its focus and has released a commercial-off-the-shelf (COTS) calibrated full-range professional studio monitor system with an essentially flat equal loudness curve running from 20-Hz to 40,000-Hz, which certainly meets my criteria, although the high-frequency aspects probably only can be appreciated by bats, cats, and dogs; and for a few of the modern popular music genres will need to be augmented with custom deep bass subwoofers. Coming in at an attractive discount price of $20,000 (US) for the loudspeakers and power amplifiers, I think this might be the foundation for a nice system for those fortunate folks who can afford it. In particular, note (a) that it is not a "bookshelf" system; (b) that it requires two external CROWN power amplifiers; (c) that it does not appear to go subsonic, although I think it certainly can go subsonic; and (d) that it meets the "big and heavy" criteria imposed by the combination of GOD, Sir Isaac Newton, and the rules of the universe as we know it, which includes having "big and heavy" 15" woofers, with each two-way loudspeaker unit weighing 58.5 pounds and each required Crown i-Tech HD 5000 power amplifier weighing 28 pounds, which is a stellar bit of reality that provides the clue to one of the reasons there are no "big and heavy" COTS studio monitor systems for all practical purposes, since (a) it costs significantly more to manufacture "big and heavy" stuff and (b) it costs significantly more to ship "big and heavy" stuff, where the revealing bit of information is that while Sweetwater Musical Instruments and Pro Sound sells the JBL M2 Series studio monitor system at a discount for $20,000 (US), which includes the JBL M2 Series 15" two-way loudspeaker units and a pair of Crown I-Tech 5000 HD power amplifiers, this prices does not include free shipping, noting that I like Sweetwater and am a happy customer . . . ]

M2 Series Master Reference Monitor System (JBL)

I-Tech HD Series Power Amplifiers (Crown Audio)

[NOTE: This is the calibration system for JBL studio monitors, but it also works on other studio monitors . . . ]

MSC1 Monitor System Controller (JBL)

[NOTE: This is the high-end but lower cost LSR6300 Series, which with the MSC1 Monitor System Controller has a typical discount price of $7,500 (US), since to be full-range it requires a pair of the matching deep bass subwoofers. I think this has the potential to be a full-range system, but it requires additional hardware to push its deep bass lower . . . ]

LSR6300 Series Studio Monitors (JBL)

Another possibility is the PreSonus Sceptre S8, since its stated frequency at -10 dB is "38 Hz - 23 kHz", which suggests that it might be capable of being pushed lower into the deep bass with the aforementioned Behringer unit or the ARC System 2, although (a) I cannot verify this and (b) it has 8" diameter woofers, which is not so encouraging with respect to the "big and heavy" rule of acoustic physics . . .

[NOTE: If the PreSonus Sceptre S8 loudspeakers cannot be pushed into the subsonic range, adding a pair of Kustom PA112S powered deep bass subwoofers will accomplish this worthy goal, hence the primary aspect is that a pair of Kustom KPC15P and PA112S powered loudspeakers and deep bass subwoofers costs the same as one PreSonus Sceptre S8 loudspeaker, hence it is a budget issue more than anything else. And for reference, I mention the PreSonus Sceptre S8 loudspeakers, because they are the only somewhat affordable COTS studio monitors that go downward by design at least to 38-Hz, which puts them in what I consider to be the "Honest" category (as contrasted to the "Sneaky Weasel" category); and I state this because at standard tuning ("Concert A" = 440-Hz) the low-pitch "E" string of an electric bass or string bass is 41.203-Hz, and in my view any studio monitor system that cannot reproduce the note of the open low-pitch "E" string of an electric bass or string bass at standard tuning at equal loudness to all the other notes is a piece of junk, although if this deficiency can be corrected by adding deep bass subwoofers to the system, then it is fine with me, since upper bass, midrange, and high frequencies are easy to reproduce . . . ]

Scepter S8 (PreSonus)

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[Surfwhammy]

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[NOTE: I did a bit of research and discovered that PreSonus has a self-powered deep bass subwoofer, which when paired with the PreSonus "bookshelf" studio monitors maps to full-range (20-Hz to 20,000-Hz) or whatever the high-end frequency happens to be (Eris or Sceptre families), and I am fine with the Trembler 10 having a 10" subwoofer, since the unit weighs approximately 40 pounds, which provides a clue to the way it satisfies the "big and heavy" rule of acoustic physics; and the Tremblor T10 has a Class AB power amplifier, which is very nice. The Kustom KPC15P units have Class AB power amplifiers, but as best as I can determine the Kustom PA112S have Class D power amplifiers, which is fine for the specific range, although Class AB is nicer. I have a pair of Fender Custom Shop Rumble Bass rigs, and they have 4x10 loudspeaker cabinets, which is similar to the classic Acoustic B810mkII 8x10 Bass Speaker Cabinet. I think it is enlightening to observe that getting a full-range studio monitor system from JBL costs approximately $20,000 (US) with discounts (which is the street price for the JBL M2 Series studio monitor system from Sweetwater, but does not include the calibrating hardware and software or shipping), so it is significant that a pair of Sceptre S8 studio monitors and Trembler T10 deep bass subwoofers is full-range but costs approximately $2,300 (US) with typical online discounts. The Kustom system I use here in the sound isolation studio costs approximately $800 (US) at Musician's Friend, and it is nice for a studio up to 20 feet by 20 feet by 10 feet, which maps to the volume knobs on the Kustom units being at approximately 3 on a scale of 0 to 10, noting that the volume knobs should be glued with silicone glue once the system is set to have a maximum output in the range of 85 dB SPL to 100 db SPL, since all these studio monitor systems are overpowered for smaller studios like the one I have (approximately 6 feet wide by 7 feet tall and 12 feet long), hence can be dangerous if not correctly setup using a calibrated sound pressure level (SPL) meter. All these systems require calibrating hardware and software, including various meters, for the calibration steps. For reference, the JBL M2 Series and the PreSonus Sceptre S8 with Tremblor T10 pairs go down to 20-Hz without doing anything, but the Kustom PA112S needs to be pushed downward with a Behringer DEQ2496 UltraCurve Mastering Processor, which is fine with me, since the Behringer unit is one of the devices I use for calibrating the studio monitor system here in the sound isolation studio, which I augment with a Behringer DCX2496 UltraDrive Pro Loudspeaker Management System to get intimate control over the individual unit volume levels; crossover types; and crossover points . . . ]

Trembler T10 Powered Deep Bass Subwoofer (PreSonus) ~ Technical Specifications

Because subwoofers are generally limited to a bandwidth of no higher than 150 Hz, the switching speed for the amplifier does not have to be as high as for a full range amplifier, allowing simpler designs. Class-D amplifiers for driving subwoofers are relatively inexpensive in comparison to class-AB amplifiers.

Power Amplifier Classes (wikipedia)

Scientific Pitch Notation: Table of Note Frequencies (wikipedia)

The problem is the subsonic, deep bass, and low bass frequencies but, for example, so long as COTS "bookshelf" studio monitors can handle the upper bass, midrange, and high frequencies (150-Hz to 20,000-Hz), then adding a pair of Kustom PA112S powered deep bass subwoofers can be a solution, at least for smaller studios; and since the Kustom PA112S units have a pass-through connector, this type of setup is possible, where you run each respective channel first to a Kustom PA112S unit and then from there the full signal goes via another audio cable (line level) to the respective COTS "bookshelf" unit. Based on current discount prices, this costs approximately $400 (US) for the pair of Kustom PA112S units and a bit extra for the required audio cables. As long as the complete system provides calibrated full-range, accurately reproduced sound at 85 dB SPL, then it satisfies the criteria . . .

[NOTE: The Kustom KPC15P powered 15" two-way loudspeaker unit also has a pass-through port, but it has one XLR and one 1/4" TRS for "Input" and one 1/4" TRS for "Line Out", while the PA112S simply has two 1/4" TRS connectors. On the PA112S, the full line-level output signal (one channel) from the computer or external digital audio and MIDI device goes to the "In" port, which has a low-pass filter with a 150-Hz upper value, but the "Out" port is not filtered, so it is the full line-level output signal (one channel). No matter how it is done, you need an equalizer (EQ) and real-time analyzer (RTA) to do the calibration, which is the case no matter what type of studio monitors you decide to use, even if you have a sonically neutral studio or listening room. One of the more curious aspects of the Kustom KPC15P and PA112S units is that you can do a reasonably accurate calibration "by ear" with help from a sound pressure level (SPL) meter, which provides some time to save for an EQ/RTA unit and calibrated condenser microphone to do a precise calibration based on the acoustic behaviors of your studio or listening room . . . ]





Virtually any self-powered DJ or PA loudspeaker system that has matching deep bass subwoofers will work nicely for the full-range loudspeakers of a calibrated full-range studio monitor system, and for this specific purpose I recommend KUSTOM units (KPC15P and PA112S), since (a) I have verified that they work; (b) I use them here in the sound isolation studio; (c) they are the least expensive units that satisfy the "big and heavy" rule of acoustic physics; and for a while you can do a "by ear" calibration with a bit of help from a digital sound pressure level meter like the NADY DSM-1 Digital SPL Meter . . .

[NOTE: This discount price for a pair of Kustom KPC15P and PA112S powered loudspeakers and deep bass subwoofesr is approximately $800 (US), although occasionally there are sales and the cost is a bit lower; and if you have good hearing and augment it with an SPL Meter, you can set them reasonably accurately "by ear", where with the volume levels for the PA112S units OFF, you set the volume levels for the KPC15P units at 85 dB SPL using the dBA weighting and then slowing bring up the volume levels for the PA112S units until the SPL Meter set to dBC weighting shows 90 to 100 dB SPL, which is one way to do it in a room that is not "boomy" (where "boomy" in this context maps to having deep bass or low bass standing waves) . . . ]

Regardless, it is vastly important to check the sound pressure level (SPL) with a SPL Meter, because all these units have the real potential to be dangerously loud in small rooms, which curiously is the reason that all or nearly all of them satisfy the "big and heavy" rule of acoustic physics, where they key is to set the maximum SPL at 85 dB SPL, although with a dBC weighting I increase this to 90 dB SPL to 100 dB SPL, since I like a bit more deep bass, but when measured with a dBA weighting, the maximum SPL should be 85 dB SPL and no higher, regardless of the size of the room, since 85 dB SPL is the same no matter how big or small the room or headphones might be, noting that headphones and ear buds are just tiny studio monitors that are located directly next to your ears or inside the ear canals and certainly can produce audio at 85 dB SPL or higher . . .

THOUGHTS

As best as I can determine, most folks use COTS "bookshelf" size studio monitor systems, none of which is full-range, and such folks are deluded in their thinking and hearing . . .

If you cannot hear deep bass at least in the range of 20-Hz to 50-Hz, then what happens is that you compensate for this inability by attempting to create the Missing Fundamental auditory illusion, and when you do this what happens is that it skews the midrange and high frequencies, since the Missing Fundamental auditory illusion is created specifically by skewing the midrange and high frequencies, which according to the rules of acoustic physics maps to what you hear through your studio monitor system being very different from what is recorded and played by your audio software and computer hardware . . .

Missing Fundamental Auditory Illusion (wikipedia)

Explained another way, it is not a matter of accurate deep bass being required to reproduce the sounds made by violas and violins, because the notes for these stringed instruments are higher (upper bass, midrange, and high frequencies), although one might suppose that a viola can generate some upper bass frequencies, hence there might be some undertones, if there are such things as undertones, which according to wikipedia there are . . .

[NOTE: This makes the subsonic and deep bass all the more important! ]

Undertone Series (wikipedia)

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[Surfwhammy]

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Instead, it is a matter of what happens when a studio monitor system does not reproduce subsonic and deep bass accurately, since what happens is that this forces folks to attempt to compensate for the missing subsonic and deep bass by resorting to using the Missing Fundamental auditory illusion, which in turn requires arbitrarily skewing the midrange and high frequencies, where the consequence is that what otherwise are good sounding midrange and high frequencies arbitrarily are made to sound bad by attempting to adjust the response of the studio monitor system to create the illusion that there is subsonic and deep bass when the realities are (a) that there is no subsonic and deep bass and (b) that the skewed midrange and high frequencies sound by definition sound bad, since although the good sounds are present in the sampled sounds and raw recorded audio, they are not reproduced accurately, hence they do not sound as they should . . .

[NOTE: Upper bass and lower midrange (which I define to be from 100-Hz to 500-Hz or thereabout) also is skewed as part of compensating via the Missing Fundamental auditory illusion, and this is especially problematic, because most of the important stuff happens in this range, which in terms of root tones or pure sine waves runs approximately from the low-pitch "A" string of an electric guitar (A3 = 110-Hz) to High C (C5 = 523.25-Hz), which is the note at the 8th fret on the high-pitch "e" string of an electric guitar. These are the notes on either side of Middle C on a grand piano, whcih itself should be enough of a clue to the importance of this particular range . . . ]

This is a video of the VSL Dimension Strings video from the Vienna Symphonic Library (VSL) website showing the MOTU CueMix FX Fast Fourier Transform (FFT) Analysis of the audio, where the red circle is centered at 33-Hz, which is approximately the low-pitch "C" string of a string bass with the C Extension, since at standard tuning ("Concert A" = 440-Hz), C1 is 32.703-Hz . . .

[NOTE: The numbers on the horizontal axis are 10-Hz, 100-Hz, and 10,000-Hz, and it is a logarithmic scale where the left third runs from 10-Hz to 100-Hz and represents subsonic to deep-bass to low-bass. This was recorded using Screenflow (Telestream) at maximum volume on the Mac Pro and MOTU 828mk3 Hybrid, which is the reason I know that the final mixing and mastering was done at least for a while at 85 dB SPL, even if only for a final check to ensure that it would not "blast" anyone's studio monitor system, headphones, or whatever. Screenflow affects the audio quality, as does the audio conversions done by YouTube, but the important thing is the CueMix FX FFT Analyzer, which in this instance is the meter, although I checked the level with a NADY DSM-1 Digital SPL Meter, which is calibrated. The average level at dBA weighting is approximately 70 to 85 dB SPL, with 85 dB SPL occurring at the maximum peaks. With dBC weighting the level range increases by approximately 10 dB SPL, since dBC weighting includes the deep bass . . . ]

VSL Dimension Strings (Vienna Symphonic Library) ~ YouTube video

Here in the sound isolation studio, (a) I hear it and (b) with the CueMix FX FFT Analyzer, I see it, hence it exists and is real, which is the way science works . . .

Among other things, this is strong evidence (a) that the studio where this video was produced, mixed, and mastered has a calibrated full-range studio monitor system and (b) that the folks who did the work actually understand and follow the rules of acoustic physics . . .

You need to be able to hear the music accurately to produce, mix, and master, and this requires a calibrated full-range studio monitor system where at least the final work is done at 85 dB SPL, which should be the loudest volume for your studio at dBA weighting and needs to map to the loudest volume for your computer and external digital audio and MIDI interface, as well as the calibrated studio monitor system itself, because among other things this maps to the song being within limits when played on other systems . . .

Headphone and ear buds will not work, although they are handy for intermediate activities, recording, and verifying that everything sounds good when you listen with headphones and ear buds, with the primary reason being that each ear hears something completely independent, which is a problem when one is producing, mixing, and mastering . . .

The only "mysteries" to this--which for reference eluded me for about seven years in the digital music production universe, primarily because although I knew it, I had forgotten the first parts and did not realize that COTS studio monitor manufacturers virtually across the entire industry are sneaky weasels to such an extent that in the US the Federal Trade Commission (FTC) had to issue regulations and guidelines to stop the rampant and egregious sneaky weaseling--are (a) that the full range of normal human hearing is 20-Hz to 20,000-Hz; (b) that accurately reproducing audio spanning the full range of human hearing requires following the "big and heavy" rule of acoustic physics; and (c) that for all practical purposes there are no COTS studio monitors available anywhere on this planet at minimally affordable prices, which in turn makes every calibrated full-range studio monitor system for all practical purposes a custom designed, installed, and verified studio monitor system, which can be done with COTS equipment and software, really . . .

[NOTE: This is a link to the announcement by the FTC in 2000 of its at the time update to the 1974 "Amplifier Rule", which has been updated since 2000, which is a clue that this industry sneaky weaseling started in the early-1970s and continues to something that requires diligent enforcement. And for reference, most of the manufacturers have devised ways to "game" the system, which in some respects is the primary reason that the only way to know for certain what your studio monitor system actually is doing is to put a meter on it and measure its behaviors yourself, which is the way it works when one is doing science rather than tricking people with marketing gimmicks. The "Amplifier Rule" was updated again in 2010 by the FTC . . . ]

FTC Approves Amendments to Amplifier Rule (Federal Trade Commission, December 2000)

Trade Regulation Rule Relating to Power Output Claims for Amplifiers Utilized in Home Entertainment Products - 16 CFR Part 432 (Federal Trade Commission, January 2010) ~ PDF (3 pages)

The fact of the matter is that professional recording studios had calibrated full-range studio monitor systems until at least 1970, but this started changing in the early-1970s, which is is the reason that I missed it when I switched from the analog universe to the digital universe three decades later, mostly because it simply did not occur to me that studio monitor companies would engage so vigorously in sneaky weaseling . . .

[NOTE: Another fact is that professional recording studios continue to have calibrated full-range studio monitor systems, but most of them augment their calibrated full-range studio monitor system with COTS "bookshelf" studio monitors as an additional set of verifications, which in some respects is like adding the "Mastered for iTunes" feature to ensure that music sold at the iTunes Store is optimized sonically for iTunes listeners, which is fine with me, but there needs to be a calibrated full-range studio monitor system somewhere in the picture, and it needs to be used at least some of the time, since it establishes the foundation and reference point . . . ]

Mastered for iTunes (Apple) ~ Guidelines, Specifications, and Tools

What "Mastered for iTunes" Really Means (Jacob Ganz, NPR Music)

I should have known this, but (a) I missed it and (b) it took me nearly seven years to realize the problem and how to correct it, which in retrospect was not so bad, because I methodically examined every other possibility and learned a lot of stuff along the way until the only remaining thing to examine was the studio monitor system . . .

Explained another way, there is a reason that radio stations nearly always sound good when you listen to them with a radio. You might not like the particular type of music, but it will sound consistently and reasonably good; and the reason is that radio stations by law and regulations (via the Federal Communications Commission [FCC] in the US) are required to put meters on everything and to ensure that everything is within bounds and tolerances, which for all practical purposes eliminates all the mysteries, and this also is the case with television and motion pictures. And there are similar rules and regulations in Europe and other countries, all of which are based on the fundamental principles of acoustic physics . . .

Really!

P. S. This is explained in more detail in my ongoing topic in the IK Multimedia FORUM, which is fabulous . . .

The Fabulous Affordable Studio Monitor System Project (IK Multimedia FORUM)

Fabulous!