Since I'm often accused of always having to be right, following are a few things where I've been wrong, which I gladly admit. Many of these gaffs are more about my learning experiences with acoustics, but some are more general.

I had always thought that a standing wave occurs at the exact null center, 1/4 wavelength from a boundary which is where the velocity is maximum. But acoustician Eric Desart explained in a web forum that the wave is actually standing still at the peak, where the pressure is maximum. Note that this is equivalent to a sine wave electrically - the wave has maximum velocity at the zero crossing, but all of the work is done at the peak where the pressure (voltage) is maximum and the velocity is minimum.

I always thought that when there's a single rectangular pulse of a short duration, the duration dictates the lowest frequency contained. That is, if a pulse extends for 1 millisecond then there's no content below 1 KHz. My expert friend Bill Eppler explained this is wrong, that even a very short pulse has content down to DC. But Bill also acknowledged this is counterintuitive.

When RealTraps made the video Non-Modal Peaks and Nulls I used an incorrect formula to determine the logarithmic halfway point between two frequencies. After Eric Desart pointed that out I got the correct formula from Bill Eppler, which is now in my Audio Expert book under Frequencies in Audio Basics Chapter 1:

Center Frequency = SQR(Higher Frequency * Lower Frequency)

After reading the diffusion papers on the web site of acoustic company RPG, I understood company owner Dr. Peter D'Antonio to say that diffusion closer than 10 feet is not useful. Later I learned from acoustician Jeff Szymanski that the distance is a function of the diffusor's lower frequency limit, so diffusors that don't work to as low a frequency as RPG's can be closer with no ill effects. I've since determined by listening that you can be even closer than is officially recommended, and still make a big improvement over a bare reflecting wall.

I once posted that angling a control room window down a bit will deflect sound from getting into a microphone. Jeff Szymanski posted a drawing showing that this is wrong. The real reason to angle windows is to reduce reflected glare from lighting.

Years ago I thought that when absorption data is given in octave bands, the data was the average for the entire octave. Acoustician Andre Vare set me straight and explained that it's still third octave data, but only every third value is shown.

My failed Live Room Reverb project is a pretty good story.

I used to think that HD radio was a nonsense marketing term, and I mentioned that once in an audio forum. Someone set me straight and explained that HD Radio is in fact different from regular radio, and embeds the digital signals for one or more additional channels within the normal carrier frequency. However, my radio expert friend Dennis Jackson since explained to me that the fidelity of HD radio is actually much worse than is claimed.

I used to think that the inevitable ripple on a digitized square wave was low-pass filter ringing, but after watching Monty Montgomery's video Digital Show & Tell I now know that it's the Gibbs effect (explained 19:00 into video), and is just what happens when the bandwidth is limited.

I used to think that loudspeaker isolation was worthwhile, including this excerpt from my Vibes article in Electronic Musician magazine:

Decouple your speakers: Sound travels through solid materials faster than through air. So when loudspeakers are sitting on a desk, low frequencies can transmit from the speaker's enclosure through the desk and floor and arrive at your ears before the waves in the air. If the secondary path is strong enough, the phase shift caused by this time delay contributes to low frequency response errors. One solution is to buy speaker isolation pads sold for just this purpose. You can optionally make pads from rigid fiberglass or even kitchen sponges - the kind that become stiff when dry work best for this.

But after measuring isolation devices for this article I now know I was wrong, proof here.

I was also wrong about several aspects of loudspeaker design and operation. When I was writing my Audio Expert book in 2011, audio guru Floyd Toole graciously reviewed my Loudspeakers chapter and explained many things I didn't fully grasp, such as how cone size affects dispersion at high frequencies. He also pointed out several fundamental errors:

He chided me for repeating the nonsense that a speaker crossover shouldn't be around 800-1,000 Hz because that's in the middle of the human voice range.

He corrected my statement, "A lightweight diaphragm can move quickly due to its low mass" pointing out that unlike a microphone, you can simply add more amplifier power.

He corrected my belief that all ported speakers suffer from "overhang" at resonance; plus too many minor points to bother listing here.

When my RealTraps partner Doug Ferrara decided years ago to replace his mediocre early model KRK monitor speakers, I urged him to get a pair of the 15-inch JBL Eon PA speakers. He instead bought Mackie HR824s which, of course, was a MUCH better choice.

The Danbury Music Centre used to have only one piano, an older model that wasn't very good. When they raised $45,000 to buy a new piano, I was opposed because I thought the old one was good enough, and there were more important things for them to buy with $45,000. But when they got the new piano and I heard how it was vastly batter than the old piano, I realized I had been very wrong. They really did need a better piano in order to accommodate professional players for concerto recitals and rehearsals.

In an audio forum someone asked if he needed a special needle to play and archive old 78 RPM records. In my ignorance I told him whatever needle he has is probably fine. Then someone who actually knows said a special needle is in fact needed, and went on to give useful advice.

Ads for audio products often say "Our price is so low we're not allowed to list it." I've seen that in online stores too, where they make you log in and click a button to see the price. I used to think that was bullshit until I learned that some manufacturers really do have a Minimum Advertised Price (MAP) that dealers must honor.

I spent two years developing a fancy first version of my Null Tester device only to learn that a teensy amount of phase shift renders the entire concept worthless! Thankfully this stripped down version works well enough to compare wires.

I used to think that the density of rigid fiberglass determined its effectiveness at low frequencies, but I since learned that the correct metric is gas flow resistance.

When my friend Chuck Scott was buying a recording setup at Eastcoast Music Mall, I told him he should use the software mixer that came with his sound card rather than buy a small format hardware mixer. Both my musician friend Ed Dzubak and store owner Morgan Pettinato correctly disagreed, and Morgan sold Chuck a Mackie 1402-VLZ. Ed made the point that, if nothing else, it's valuable to have a physical volume control you can lunge for if something loud and unexpected suddenly comes out of the loudspeakers. I now realize there are other important benefits to a hardware mixer.

One of my biggest gaffs was when I designed a big mixing console in the 1970s. I used slide pot level controls for the input section, but not for the output mixing section where they're most common and more useful! That didn't affect the performance, but in hindsight this is pretty embarrassing.

Not audio:

When I was a teenager I believed that ESP was possible. Once my friend Mike Rodericks and I said the same thing at the same time, something not related to what we were just talking about. Now I realize that was just a coincidence. Mike and I had been friends for more than 30 years at the time, and I've spent hundreds of hours with him. If something like this never happened, that would be a surprise. Also, sometimes I could tell which song was about to play on Top 40 AM Radio, sort of how you can "hear" which song is coming up on an album you're familiar with. But now I realize that radio stations use play lists, and often play the same songs in the same order.

One spring day years ago I noticed that a spider had set up shop between the glass and outer screen in my kitchen window. I explained to the spider that he'll never catch dinner there because other bugs won't be able to get through the screen. Man was I wrong! I watched all summer as a steady stream of bug carcasses collected in the window well.

Ethan Winer has been an audio engineer and professional musician for more than 50 years, and is a principle at RealTraps where he designs acoustic treatment products for recording studios, home theaters, and istening rooms. Ethan's Cello Rondo music video has received nearly 2 Million views on YouTube and other web sites, and his book The Audio Expert published by Focal Press, now in its third edition, is available at amazon.com and his own web site.

Entire contents of this web site Copyright © 1997- by Ethan Winer. All rights reserved.