Sound, as a former teacher once put it, is part science and part black magic. One example of the latter is the phenomena known as “resonant frequencies” or – as physics textbooks put it – “a natural frequency of vibration determined by the physical parameters of the vibrating object”.

Simply put, every object has a natural frequency at which it vibrates. If you are able to stimulate this frequency, you can cause said object to vibrate. In certain cases, this vibration – mated with other external factors – can cause wine glasses to shatter or bridges to fall.



Yes, you read that right, a bridge. Specifically, a suspension bridge in Tacoma, Washington, which was brought down in 1940 by a combination of elementary forced residence, strong wind and aeroelastic flutter.

This bridge, the Tacoma Narrows Bridge (the world’s third-longest suspension bridge at the time), lasted only five months before spectacularly collapsing into Puget Sound, taking a hastily-abandoned car and a very frightened dog along with it.

While not as catastrophic as a bridge collapsing, resonant frequencies are also a bad thing in sound reproduction. Such vibrations can change the timbre (or characteristics) of the sound being reproduced. This, of course, is not a good thing if you are really into high quality sounds in your car.

So, how do you get around this conundrum?

A good way around it is what three gentlemen did recently. They got themselves a pair of PHASS NT28BML resonance control customised tweeters installed as part of their in-car entertainment (ICE) systems of their cars. More on this later.

Why is the PHASS NT28BML so essential when it comes to combating resonant frequencies?

According to Tehnichi Audio’s head guru, Simon Teh, having a good pair of tweeters has always been pivotal to improving the sounds being reproduced by a car’s audio system.

“Tweeters reproduce the upper frequencies in music and make the music sparkle and come alive. They are also important for sound staging and stereo separation,” he said.

According to Teh, resonance frequencies in tweeters are probably the most insidious type to challenge against.
“This is because the higher frequencies that tweeters reproduce are the ones where the human ear is most sensitive to in terms of tone colour. In short, these resonant frequencies will affect sound quality and disrupt your listening pleasure,” he added.

So, what makes the PHASS NT28BML do what it does? The design of a loudspeaker, in general, involves mounting a direct radiating cone that is given room to vibrate.

According to information from Georgia State University’s physics department, this mounting is elastic, hence, there is inherent resonance in such a set-up. As a result, this free cone frequency will distort sound by responding more closely to signals near its own natural vibration frequencies.

What the boffins at PHASS have done is to custom design and manufacture tweeters with resonance control in consideration.  The NT28BML is developed with a special customised frame technology to create a mechanical structure that helps to damp down on distortion.

On top of that, to enhance the reproduction of higher range frequencies, the NT28BML’s silk fabric and very thin diaphragm helps to increase the sensitivity and, thus, contributes to superb sound detail. Its 27.2mm neodymium magnet also ensures ultra efficient signal transfer.

So, on paper, we have tweeters that are capable of handling an insidious menace. How do they stack up in the real world? As it turns out, pretty well.

The first test car was Mr Khong’s Mercedes-Benz C-Class sedan.

In what was essentially the factory standard ICE system (no amp or subwoofer) with some Tehnichi Audio tweaks, the risk assessment manager’s love for 70s and 80s music, as well as new age and jazz – a lot of them MP3 tracks, were put through the paces.

It was an enjoyable 45 minutes of going down memory lane with songs that were very much part and parcel of this writer’s childhood.

Throughout it all, the PHASS NT28BML worked seamlessly with the system at hand to create a zone of calm and happiness.

If there was anything to criticise, you could say that Mr Khong’s ICE system lacked that little something in the bottom end to provide the necessary bombast.

He did acknowledge this fact and has been mulling over the best time to get an 8-inch subwoofer installed to provide the necessary lower frequency boost.

The success of this system whetted my interest on what a resonance-combating tweeter could do with a more complete set-up.

This was achieved with the arrival of the second test car, a Hyundai Elantra with amps, a subwoofer and other Tehnichi Audio tweaks, and Simonte Black Tunes and Legato Link.

Here, the music finally got the proper high, mid and low end that it sought. A variety of genres went into the testing process and all came up Top Trumps.

The beauty of the NT28BML helped create a seamless musical experience that showed what a resonance-unhampered system could sound like.



However, nothing quite prepared this writer for the third test car.

A Volkswagen Golf R that had its rear seats removed so that the pre- and power amps (yes, as in more than one) and subwoofers (again, more than one) could be mated to a full PHASS speaker set-up together with the best that Simonte and Tehnichi Audio could provide.

For the longest time, this writer has sought to find the experience of a live sound venue recreated in a car. On that day, in that car, I found it.

The entire set-up, with the NT28BML leading the way, the true power was unleashed.

It was a revelation. All these years, good systems that I have encountered have been so close yet not quite there.
It was the PHASS NT28BML that unveiled the true beauty of sound recreated without resonance frequencies colouring the performance.

However, it is unlikely that this writer will be ripping out his car seats anytime soon to experience such sonic nirvana.

I wonder whether the Volkswagen’s owner rents out his car?



 

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