19-21 Aug 2020
International Convention Centre Sydney

Product specifications: Who needs to know?

Oct 30, 2019 Audio & Broadcast

The old saying ‘lies, damned lies and statistics’ could apply to AV equipment specifications, is it more important to sell the solution?

During Integrate 2019, a series of ‘round table’ discussions were held to gauge how stakeholders in education, retail, enterprise, etc, felt their markets were performing. After many hours of discussion, one universal truth emerged: there is a disconnect between what end users want, what integrators install and what suppliers promote and sell.

End-User involvement

It’s easy for AV technology professionals to be swept up in the excitement of new developments, no matter how minute, and that’s OK. In fact, excitement is what drives this industry forward.

However, it’s important to remember that sometimes (or most of the time) end users don’t care. To most of them, the f-stop of a projector’s lens is about as interesting as knowing what happened to Bruce Samazan*. There are far more important things in life.

Let’s take loudspeaker specifications as an example.

Speakers feature a range of detailed specifications – such as waterfall plots, step and pulse response, phase response and distortion characteristics – that are used extensively by speaker designers.

But they really can’t be interpreted by the general public, so do they really need to know?

A dive into the world of speaker specs

“Speaker specifications can vary greatly from one model to another. Typically, efficiency and frequency response are the first specifications people look for and are possibly the most relevant,” the late Colin Whatmough, a renowned Australian loudspeaker designer, once explained to Connected magazine.

The industry standard input for a speaker is 2.83V, which equates to 1W into an 8Ω speaker – regardless of the speaker’s impedance.

“Efficiency should be an average output across the speaker’s stated response or output, measured from a ‘white noise’ input.

“Some unscrupulous manufacturers measure the frequency response peaks and quote them as efficiency. This gives an inflated efficiency rating that is probably exaggerated even more, as such products are likely to have a wildly varying response.”

Efficiency is an important parameter, as it dictates how much amplifier power will be required. Achieving a satisfying volume with speakers of 90dB may require a 50W amplifier. If the speakers have an efficiency of only 80dB they will need 500W to achieve the same level, whereas 100dB efficiency speakers require only 5W.

Average speaker efficiency is about 87dB, measured at a distance of 1m. A speaker with an efficiency of 80dB is considered very low, and an efficiency of 100dB is considered high.

Frequency: How much does the range matter?

“In terms of frequency response, care should be taken when assessing the range quoted,” Colin said.

“A frequency response of 20Hz to 20,000Hz may sound impressive, but it is meaningless. Without dB limits, virtually any speaker will produce some sound at any frequency from 20Hz up to 20,000Hz and so claim such a response.”

A meaningful frequency response should be qualified with dB limits. The frequency response of a quality speaker may be 40Hz to 20,000Hz +/- 3dB. If this speaker’s efficiency is about 87dB, the output level would not exceed 90dB, or drop below 84dB, across its stated frequency range.

“Generally, the wider the frequency range the better, but other parameters may have more effect on the overall naturalness of the sound,” he said.

“I have heard many mini-monitors outperform much larger speakers even though the former had restricted bass extension. Their lower distortion levels and a much smoother response is reflected in their more natural sound quality.

“However, frequency response within dB limits can still be misleading. Two speakers may have a quoted response of 40Hz to 20,000Hz +/- 3dB yet sound very different.

“Speaker A may be up by 3dB in the bass and 3dB down in the treble, resulting in a fat, dull sound. Speaker B, being 3dB down in the bass and 3dB up in the treble will sound more lively, but lean and aggressive.”

Power handling: Tricky to manoeuvre

The specification for the power handling capability of a speaker causes the most difficulties.

“It is natural to assume that a speaker rated at 100W couldn’t possibly be damaged by an amplifier capable of 90W, but it’s not that simple. Although a 90W amplifier may produce 90W at very low distortion, it may produce far more than this when driven into clipping, where distortion increases considerably.

“Music is by its very nature dynamic – that is, it has loud passages followed by quiet passages. During the loud passages, speaker voice coils heat up. When there is a quiet passage they cool down again.

“Some music, particularly electronic music, has a very low dynamic range (it’s always loud) and doesn’t give the speaker voice coils a chance to cool down.”

As a result, the voice coils get hotter and hotter and eventually start to burn. Speakers rated at 100W will probably sustain permanent damage if subjected to continual power of 80W, but they will be happy with short-duration transients of hundreds of watts.

The situation with amplifiers and disc players is even worse. Most quality amplifiers have excellent frequency response and low distortion, yet they can sound very different from one another.

Power outputs: Not so straightforward

Even power output is not as straightforward as some people imagine.

“Some amplifiers capable of quite high power still sound wimpy and gutless at any volume level. Other lower-powered amplifiers (usually with comparatively large power supplies) can sound much more powerful, or gutsy, until they are driven beyond their rated power and start distorting,” Colin said.

“Complex response, noise and distortion plots may help electronics engineers and designers, but they are of little relevance to the typical consumer. For that reason they are rarely included with specifications.

“Generally speaking, equipment with poor specifications will not perform well, but good specifications do not guarantee good performance. The way to judge equipment is by listening and comparing.

“With experience, your ears will be more sophisticated than any test equipment available.”

Where does that leave integrators?

Rather than selling products based on specifications, it is more important to develop solutions that meet (or better yet, exceed) your client’s requirements.

Forget numbers… sell emotion, solutions and the experience.

This article was contributed by Paul Skelton, Editor of Connected Magazine. If you would like to be the first to hear about industry news, subscribe to the Integrate newsletter Convergence.
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