Distortion at the level you mix is an exclusive Specifications Pro file. The claim under test is distortion. In a distortion bench in France the sheet offers THD at a stated SPL. On a working day in a mix position in London that figure is only meaningful beside the SPL you actually mix at, not 90 dB because a chart said so. This desk does not sell the device and does not rank a brand. We read the footnote. A high-intent buyer already knows the headline number. What is missing is the sentence a successor can check without the salesperson in the room: Measure distortion at your playback SPL. If that sentence cannot be written, the datasheet is a poster. Posters are allowed in a lobby. They are not allowed on a purchase order. The sections below stay specific to distortion work. They are not a generic luxury essay and not a reprint of a manual.
Start with the test condition, because the number without it is theater. For distortion, the SPL you actually mix at, not 90 dB because a chart said so. Write those words next to THD at a stated SPL before you compare two quotes. In a distortion bench in France the condition is controlled. In a mix position in London it is not, unless you bring the control with you. Exclusive reporting on this desk keeps meeting the same quiet failure: the spec was at a polite level and the playback was not. That failure is not a scandal. It is what happens when a careful adult trusts a headline. Ask the vendor to point at the paragraph in the sheet that states the condition. If they point at a photograph, you do not yet have a specification. You have a campaign. Campaigns are not what Loudspeakers is for.
Units and tolerances are the product. THD at a stated SPL must name the unit, the tolerance, and the sample. A single hero unit in a distortion bench in France is not a production spread. Ask how many units were measured and what was excluded: warm-up outliers, pre-production firmware, a golden sample. Then put the same question to the unit that will ship to a mix position in London. If the vendor cannot say whether your serial is inside the measured population, price the risk as real. Specifications Pro will not invent a tolerance the sheet does not have. We will insist the missing tolerance is a blank line, and blank lines do not ship.
The interface can void a true number. Here the interface is a loud client playback. A measurement that stops before that interface is a measurement of a different product. Draw the path from the claim to the thing a human hears, sees, or stores. Every box on that path can add noise, latency, color, heat, or a second clock. In a mix position in London the path is rarely the path in a distortion bench in France. Write the path you will actually build, then ask which part of THD at a stated SPL survives it. If the answer is 'the spec assumes a direct connection,' you have learned the limit of the spec. Limits are useful. Implied infinity is not.
A bench protocol, short enough to do. Day one: copy THD at a stated SPL and the SPL you actually mix at, not 90 dB because a chart said so into a one-page sheet titled with the legal model, not the nickname. Day two: measure or inspect a loud client playback and photograph the screen that states the mode, not the screen that says congratulations. Day three: run the failure on paper. The failure we keep seeing is this: the spec was at a polite level and the playback was not. If your installation cannot prevent it, write the mitigation beside it. Day four: take the page to a second human who was not in the sales call. If they cannot reconstruct the claim, the page is not finished. Day five: only then compare price. Price without the page is how a mix position in London buys a lab story that will not survive the first week.
The purchase order is where specifications become enforceable. The sentence we would not ship without is: Measure distortion at your playback SPL. Add the firmware or revision, the included accessories that were present during the test, and the lead time for the spare that keeps the number true. Do not write 'or equivalent.' Equivalent is how a matched pair, a profile, a clock, or a lamp bin disappears between the quote and the crate. If the seller refuses the sentence, they are telling you the number is not a promise. Believe them. Buy a different promise or budget for a test you will run yourself on delivery.
A specification can pass and the job can still fail. Hold both ideas at once. The spec was at a polite level and the playback was not The sheet in a distortion bench in France did not lie. The job in a mix position in London asked a different question. List three job questions the sheet is allowed to ignore: the room, the operator, and the deadline. Then decide which of those three you will control. If you control none of them, you are not buying distortion. You are renting a demo. Demos are legitimate. They are not a substitute for the SPL you actually mix at, not 90 dB because a chart said so. Write 'demo' on the file if that is what you attended, so a later reader does not treat a showroom as a lab.
Compare two live quotes and let the second one win. Put both through the same page: THD at a stated SPL, the SPL you actually mix at, not 90 dB because a chart said so, a loud client playback, and the order sentence. If the first vendor matches the second in an afternoon, the first quote had slack. If they cannot match and cannot explain the gap with a document, you have found the real product. Do not let a brand narrative replace the gap. A famous door in a mix position in London can still ship a unit that was not the unit measured in a distortion bench in France. The desk's refusal is specific: we would not accept an undated plot, a verbal tolerance, or a firmware 'you can update later' as if later were free of risk. Later is a second product.
Field sheet for distortion readers. One: legal model and revision. Two: THD at a stated SPL. Three: the SPL you actually mix at, not 90 dB because a chart said so. Four: a loud client playback. Five: the failure you are buying against, in ordinary words: the spec was at a polite level and the playback was not. Six: the order sentence: Measure distortion at your playback SPL.. Seven: spare lead time and match. Eight: who else can read this page if the buyer is on a plane. If a line is blank, the specification is not finished. Reopen the page when the firmware changes, the room changes, or the vendor is acquired. Those events rewrite distortion without asking you. The question that reopens it is the same question the file started with, asked of the unit you hold, not of the unit in the photograph.
What this desk would not do: we would not treat THD at a stated SPL as a personality. We would not hide a failed check because the case is beautiful. We would not let a loud client playback be 'included' without a drawing. We would not sign in a mix position in London against a PDF that names a different revision than the crate. The test is dull on purpose. Can a careful adult, using only the page, predict the spec was at a polite level and the playback was not and say whether this installation prevents it? If the answer is no, the missing line is the thing you have not bought. The object can wait a week. The line often cannot be reconstructed after the crate is unpacked and the salesperson has left.
Method. Specifications Pro commissioned this exclusive explainer for the Loudspeakers desk. We do not take payment to bury a warning. Display advertising is sold apart from the newsroom and does not choose these sentences. We follow Google publisher rules and Google Ad Exchange rules: original copy, no encouraged clicks, no scraped manuals, ads kept off buttons. Sulvo and the other parties named in ads.txt may measure and render ads under their own fraud rules. They do not edit the desk. This is general information, not an engineering stamp, a calibration certificate, or legal advice. Standards and firmware change. The current datasheet and your measurement win. Corrections: send the URL, the clause, and the date. We update a page when a material error is confirmed, not when a vendor dislikes a specific sentence. If you keep one move from Distortion at the level you mix, keep this: write Measure distortion at your playback SPL. and do not accept THD at a stated SPL without the SPL you actually mix at, not 90 dB because a chart said so.
Applied note for a buyer acting this month. Open a single page. Title it with the legal model of distortion. Under it, paste THD at a stated SPL and, in the next line, the SPL you actually mix at, not 90 dB because a chart said so. Under that, draw a loud client playback as boxes. Under the boxes, write the failure in your own words: the spec was at a polite level and the playback was not. Leave four lines for the answer you were given, the name, the date, and the document. Then copy the order sentence and do not soften it: Measure distortion at your playback SPL. A printed copy stays with the quote. A second copy stays with the person who will operate the system in a mix position in London when the buyer is gone. If you cannot finish the page in one sitting, you have found the hole while it is still a hole. The Loudspeakers desk publishes files like this one only on Specifications Pro. Use the section index for the next file. Do not trust a snippet that points at a look-alike domain. The standard on every desk is the same: a footnote a successor can read, a number with its condition, and a clear separation between the sentence and any advertisement beside it.
