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Product: TASi TA 8151 - digital sound level meter
Manufacturer: Suzhou TASi Electronics Co.,Ltd. - China
Approx. price: 15€
Reviewer: Lucio Cadeddu - TNT Italy
Reviewed: July, 2021

Foreword

Audiophiles should be familiar with the concept of sound pressure. After all, this is what their HiFi systems generate thanks to speakers and amplifiers. As it turns out, many audiophiles have no precise idea on how to measure sound level. Sound pressure level (SPL) is, roughly speaking, the pressure level of a sound, measured in decibels (dB). Why should we measure it? And how?

Well, a speaker's sensitivity is given in terms of dB/W/m. For example, a 90 dB loudspeaker generates, with just 1 (one) watt, a 90 dB sound pressure at 1 meter of distance. Now, 90 dB is a very, very loud sound. As a result, even 1 watt might be sufficient to generate a reasonable listening level. Many audiophiles shell out outrageous amounts of money to pay watts they will never use. For his reason it is of paramount importance to get an idea on our usual listening levels and, hence, how many REAL watts we need.

How to measure sound pressure level? It's easy, and nowadays it is easier than ever. Once, sound level meters were devices for professionals, costly components that were also hard to find. Nowadays a smartphone and a free app is the easiest way to get an idea of our listening habits. The useful suite JBL Tools, for example, contains also a fairly precise sound level meter. Of course, its accuracy depends on the quality of the microphone of your smartphone, which isn't exactly a precise device. Anyway, it is a smart way to start with.

You might need to get a more precise idea of what's happening in your listening room and that's why sound pressure level meters enter the game. There are two types of SPL meters: Class 1 and Class 2 products. Class 1 devices are meant for professionals and might be extremely expensive. Of course, they are far more accurate and analyze a wider frequency spectrum. Class 2 SPL meters can be extremely inexpensive, and reasonably accurate, like the one under review.

Another difference among SPL meters is the possibility to perform A-weighting and C-weighting measurements. An “A” sound level meter weighting makes its readings conform to the human hearing response. It is defined in various International standards such as the IEC 61672, as well as in various national standards such as ANSI S1.4. (USA). This is the most common measurement standard. It covers the full frequency range of 20Hz all the way up to high frequency 20 kHz. The human ear is most sensitive between 500 Hz and 6 kHz (with a peak at 4 kHz) whilst at lower and higher frequencies the human ear is not very sensitive (hence the loudness switch on some amplifiers!). The “A” weighting adjusts the sound pressure level readings to reflect the sensitivity of the human ear.

C-weighting is essentially flat or linear between 31.5Hz and 8kHz. It is commonly used to measure sound level peaks. Z-Weighting has a flat frequency response between 8Hz and 20kHz (±1.5dB), this is the actual noise that is made with no weighting at all for the human ear (Z stands for zero, indeed).

When loud is too loud?

Enter the TASi TA8151 digital sound level meter. TASi is a Chinese brand that specializes in measurement devices, sound level meters, multimeters and the like. The unit under review is a fairly inexpensive IEC 651 Class 2 device. It measures in A-weighting only, that is what we audiophiles mainly need. Its performance relies on the quality of the 1/2" electret condenser microphone, which is protected by a wind screen. It works within the frequency range 31.5Hz-8.5kHz, and 30-130dBA sound pressure level window. Its claimed accuracy is ±1.5dB (reference sound pressure accuracy, 94dB@1kHz). For more tech specs, have a look at the chart below. It has a very nice and readable digital display, with a useful backlight, if required. It can show MAX and MIN levels and has a HOLD function, to temporarily stop measurement. FAST and SLOW measurements are possible, as well. With no input from the user, the SPL meter shuts off after 15 minutes. You might need to extend this time and perform a continuos measurement (> 15 minutes): press F/S switch first, then ON/OFF, a signal COU will light.

This device is extremely easy to use and it can also be placed at a stable 45° angle for reliable measurements. Indeed, holding the SPL meter by hand isn't a good idea: sound might reach the mic at slightly different angles and small hand movements can affect the reliability of the measurement. It is extremely well made, and a quick comparison with my old RadioShack Class 2 SPL meter found no differences in values, but this TA8151 seems definitely faster (read: more reactive). Moreover, the sensitivity range of the Radioshack meter was narrower (50-126 dB) and this means it couldn't measure low listening levels.

This TA8151 is faster and more accurate than a smartphone app, too. After one year or so of use it might need recalibration, that should be performed by using a reference sound level source and appropriate software. Considering it is so inexpensive I believe it is better to purchase a new unit when measurement accuracy decays, instead of sending it to the seller for a recalibration, which is going to be more expensive than the unit itself.

It is a fairly simple device, so there's no data output port to connect it to a PC, for example. It can't record the data, just hold the MIN and MAX SPL levels. For a gross estimate of the real power we need from our amplification system this component is more than enough, though. Next time you think you need more power, just spend 15€ on a device like this. Almost certainly, you'll discover you do not need any extra power. Eventually, invest in a better sounding amplifier, instead!

Availability

It is easily available in standard stores, general online stores or on Aliexpress stores. Prices might vary from 15 to 20€ or so.

Conclusions

This TASi TA8151 is a better alternative than smartphone SPL apps, costs almost nothing and get the job done. In my opinion, a real must-have, since it is the better investment that can make you save money, preventing you from purchasing an expensive high power amplifier when this isn't really needed. You'll discover that, most of the time, you just use 10-20 watt per channel.

N.B.: all of the above is intended to be a brief introduction to the pleasures and learning experience you can gain from the use of a simple, cheap and informative sound level meter. You will pick up a good idea of the sensitivity of your speakers, the power of your amplifier and the sound field that is your listening room. Audiophiles may wish to spend much more time and money on such a project.

© Copyright 2021 Lucio Cadeddu - direttore@tnt-audio.com - www.tnt-audio.com

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