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[Italian version here]

Product: Peerless DA25BG08, Seas 19TNF and Visaton DT-94 tweeters
Manufacturer: Peerless, Seas & Visaton
Price: around 20/30€/$/pair
Reviewer: Paul Hunting - TNT UK
Reviewed: January, 2022

QMS

Mechanical Q factor Qms (quality mechanical speaker) is a measurement of the mechanical Q factor of a driver. The higher this value the less energy loss of the driver and the better the instrument reproduction tone. Drivers with a high mechanical Q should sound: more open, more clean and more dynamic (See reference). Table 1 reports the QMS for two tweeters, the Visaton DT-94 and the Peerless DA25BG08-06. The Visaton DT-94 has the higher figure of 3.07 compared to the Peerless (1.89) and the DT-94 can be said to be the better mechanically damped tweeter because of this.

Inductance Le

Table 1 (third column) also gives the Le measure of inductance for the three tweeters. As I understand Lenz's law inductance is defined as the ratio of the induced voltage to the rate of change of current causing it.The higher the Le measure the more time the voice coil holds the current flowing through it. Which means the more time will lapse before the speaker responds to the amplifier's voltage change. This argues that high Le speakers will have a slower transient response (See reference). The Visaton DT-94 tweeter has the highest Le value (0.12), of the three tweeters, and argues that this tweeter will not sound as fast and will have less polished transients. The Peerless DA25BG08 has the fastest (0.02) transients and the Seas 19TNF figure (0.05) seems to indicate good transients. Both should sound fast and faster than the Visaton.

Voice Coil Size

The last two columns of Table 1 give estimates of voice coil size firstly as piston area but also as voice coil diameter. A large radiating area, according to Troels Gravesen, should mean reduced excursion for the same SPL and hence reduced distortion (See reference). The Peerless DA25BG08-06 has the largest piston area and voice coil diameter. This tweeter does sound detailed. Compared to the Visaton or the Seas the Peerless had more space between instruments in the upper octave and the sound had more air to it, both indicators of a detailed performer. It was revealing.

Discussion

I found that there was an alignment between measurements and performance. The Visaton tweeter, with its high QMS figure, did excel in instrument body and tone, especially solo instruments. CDs with Violins and upper cello are particularly notable as having more body with the DT-94 fitted. The Visaton just seems to add less colouration to the sound. The Visaton reproduced Castiglioni piano music (Nicolls playing) well. This CD features a lot of high frequency piano. Listening to the same tracks, but with the Seas tweeter fitted, there was a ringing to high frequency notes and the piano sounded flat and lacked tone. The Peerless, also, did not play the Castiglioni CD as well as the Visaton. Although high frequency piano notes were not exposed and instrument tone was acceptable there was a slight metallic sound to some notes and tone was not as good as with the Visaton.

A recording that only sounds good if the timing and transients are OK is Thomas Ades, Asyla, and the Visaton tweeter, with its high Le value, only sounded just passable with this CD, it is plodding and boring in places and the pace is spoiled and loses some authority because of this. The Visaton which has a high value of inductance (Le) does not seem to handle transients and timing so well. Both the Seas and Peerless tweeters had a low Le value and both had better pace than the Visaton. Listening to Steve Reich Music for 18 Musicians (Ensemble Modern playing), with the Seas, the piece is foot tapping and the pace is good. This was also true of the Peerless. Re-listening to Thomas Ades, Asyla, with the Peerless, the pace is spot on and the CD is an exciting and lively listen.

I preferred the Peerless because it had better pace and the tweeter did not do anything so bad to the sound. It also had more detail or more so called air and instruments were better separated. OK, violins and cello and some solo voice sounded noticeably tonally better with the Visaton. But the Peerless reproduced pace and detail so well that this was enough to compensate for some loss of instrument body. But if you value instrument tone more than pace you might prefer the Visaton or a high QMS tweeter. If you value pace go for a tweeter with a low Le value.

Conclusion

So do tweeter measures count. I believe they do. Mechanical QMS says something about tweeter damping and instrument tone reproduction, Le speaker inductance informs about the pace and timing and Troels's piston diameter seems to be a proxy measure for detail. There are likely to be other measures. Please write in with the tweeter measures that you use. There are a couple of problems with measurement comparisons. It assumes all manufacturers use the same assumptions when calculating metrics. This is unlikely; so differences should be expected. Further this was a small sample and so is of limited value. If you're in the market for buying a tweeter nothing beats listening to it before you buy but measurements might also be of interest.

© Copyright 2022 Paul Hunting - paul@tnt-audio.com - www.tnt-audio.com

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