By Lam Seng Fatt
There are many audiophiles who believe a super tweeter will improve sound quality. It is actually quite a controversial issue and I have been involved in debates over the effectiveness of using super tweeters at least twice – once in the hifi4sale forum and the second time with a group of Australian audiophiles.
My point is this – if you listen to only CDs and CD rips, it is not necessary to use a super tweeter. This is because even though the super tweeter can reach up to 35kHz or 50kHz, there is no musical signal above 20kHz when you play a CD simply because the CD player has a filter to remove anything above 20kHz. Also, there is no musical data above 22.05kHz on the CD itself because that is the Nyquist frequency. Red Book specs dictate that the maximum frequency contained in a CD is 22.05kHz which is half the sampling rate of 44.1kHz.
This can be scientifically proven. Here I will show you a frequency analysis a ripped CD track of Body and Soul featuring Amy Winehouse and Tony Bennett using Audacity.
So when you plug in a super tweeter and play a CD and the super tweeter crosses over at, say 15kHz, you are actually hearing the effect of a boost in loudness from 15kHz to 20kHz. This effect can result in more clarity, more air, more extended treble, larger sound stage and blacker background. That is possibly why many audiophiles say the super tweeter improves sound quality. But you can possibly get the same effect if your amplifier has a tone control and you boost the high frequencies.
However, if you play a hi-res file or an LP, you may argue that there are musical signals above 20kHz being reproduced by the super tweeter. That is because if you play a hi-res file, say, a 24 bit 96kHz track, there will be data captured up to 48kHz, the Nyquist frequency, which is half the sampling rate of 96kHz. If you play an LP, there is a chance some music above 20kHz can be reproduced. I once measured some vinyl rips and found the tracks to contain music up to 25kHz-30kHz.
Here’s a frequency analysis of a 24/96 file from HD Tracks of Diana Krall’s Boy from Ipanema from her Quiet Nights album.
If you play LPs and hi-res files, there may be a case for using a super tweeter. But after reviewing the Avantages Audio magnesium super tweeter, there are at least two points I want to make.
First of all, you have to be aware that boosting the high frequencies can change the sound quality in the lower frequencies. For e.g. you may notice a snappier bass, but the super tweeters can also change the voices of the singers. Secondly, you have to take into account the sensitivity of the speakers you use them with.
In my system, the ATC SCM50 floorstanders have sensitivity of 85dB while the Avantages Audio magnesium super tweeters are 90dB (into 6 Ohms). That’s already a mismatch and I could hear it in the form of a too prominent treble which did not merge seamlessly with the mid and bass. So you will have to use super tweeters with speakers of the same sensitivity.
The Avantages Audio magnesium super tweeter is an omni-directional design with the tweeter firing upwards to a wooden cone with curved sides. The super tweeter is compact, measuring 18 X 14 X 9 cm and weighs 500 gms. It has selectable input of 15kHz and 18kHz and it can play up to 35kHz.
I found the input of 18kHz to be less seamless and I kept getting distracted by the extra clarity and more extended treble. Using the 15kHz input proved to be more bearable. But bear in mind the 5dB difference in sensitivity between the ATC speakers and the super tweeters.
As for the phenomenon of a super tweeter being able to change the sound at lower registers, I played a CD rip of Jennifer Warne’s The Well and chose the track Invitation To The Blues. I used J River V24 on my laptop and the Wyred4Sound DAC2, the Lamm LL2 Deluxe preamp and Bryston 4B SST power amp. I noticed that there were changes to her voice with the super tweeter connected. The 18kHz input resulted in greater change.
I then played a HD Tracks 24/96 version of Diana Krall’s The Boy From Ipanema from her Quiet Nights album. With the 15kHz input, there was more clarity and I could hear her breathing in air before singing a line, but the mellowness and slight huskiness was missing. With the 18kHz input, there was even more clarity, but her voice became a bit thinner and much less mellow.
I had noticed this phenomenon before the recent Kuala Lumpur International AV Show and during the show, I made it a point to spend some time listening to the Avantages Audio Cesar omni-directional speakers in CMY Audio & Visual’s exhibition space. The Cesar incorporates the super tweeter as part of its design.
Where they rightfully belong on top of the Avantages Audio Cesar, the super tweeters merged very well with the enveloping sound of the omni-drirectional speakers. The sound was cohesive and seamless. The treble did not stick out distractingly and the music just flowed and flowed pleasantly even when I walked from one side of the room to the other – they’re omnidirectional, after all.
It goes to show that when using a super tweeter, matching is a must. I would recommend using super tweeters only if your system is very dull and dark sounding and you want some sparkle to the sound quality (and make sure the sensitivity matches). If you play only CDs or CD rips, I don’t think super tweeters are needed. If the original tweeters in your speaker are rated to go up to 30kHz-35Khz and beyond, don’t bother using super tweeters. And most important of all, try the super tweeters first to find out if the overall sound quality changes too much. If you are happy with the result, then CMY would be very happy to sell you a pair.
The Avantages Audio magnesium super tweeters are priced at RM4,200 a pair. They are available at CMY Audio & Visual.