Being bitten by the super-tweeter bug a few months ago I took the opportunity to try a pair of ELAC 4Pi Plus.2 super-tweeters at home. This is an omnidirectional ribbon tweeter that has been on the market for a very long time and has been incorporated into some of ELAC’s best loudspeakers in the past, it has now partly been replaced with the JET ribbon tweeter. The 4Pi Plus.2 however, remains available to enhance the performance of any loudspeaker.
The 4Pi Plus.2 is omnidirectional. The ribbon behind the mesh grille is only 0.006 mm thick and moves in a high power magnetic field produced by neodymium magnets above and below. Since this ribbon is round the sound projects to all sides through the mesh grille. It has a very low impedance, too low for any amplifier and therefor the 4Pi incorporates a transformer to give it a six Ohm nominal impedance that drops to three and a half Ohms at 10kHz. The 4Pi is not a small add-on, it measures 150mm wide and 250mm deep. Behind the tweeter’s ‘mushroom’ two rotary switches let you choose the efficiency and the crossover frequency. The 4Pi will match any speaker with an efficiency between 84 and 92dB with -4,-2, 0, +2 and +4dB settings. The crossover frequencies are 10, 12 and 15kHz and the claimed frequency range is 10 to 50kHz. The cabinet and knobs do shine: high gloss black, chrome and aluminium looks pretty impressive even on top of a pair of floor standing speakers like my PMC fact.12. Connections are made with WBT binding posts. Strangely my wife found them far more attractive than the small Townshend super-tweeters in normal use.
Since the 4Pi Plus.2 is heavy and big I didn’t place them on top of my Harbeth P3ESR monitors, but behind them on an audio rack. Leaving enough space to the side- and the back walls. This may not be the optimum position, nevertheless the effect was noticeable at once. Given the low efficiency of the P3ESR I started with the lowest possible volume setting and the crossover at 12kHz. It soon proved to be too much and I switched to the higher 15kHz setting. This was more or less correct, although still on the edge of being a bit too loud. The 4Pi gave me a more spacious sound, a larger stage and more space between instruments. Adding and removing the super-tweeter on any kind of music resulted in a ‘collapse’ of the stage and a less vivid sound. A similar result to the Townshend Maximum super-tweeter. This form of spacious sound is more enhanced with the ELAC than with a Townshend, but the Townshend makes the response of the speaker a little faster. This might have been due to the position, so I moved the 4Pi into my main room and put them on top of the PMCs.
Experimenting with the settings again resulted in the same outcome, -4dB level and 15kHz crossover. More level or a lower frequency seemed over the top. Setting the level to 0dB and 12kHz resulted in an unnatural sound with too much high frequency energy and a soundstage not unlike a bathroom. But adjust it correctly and you are presented with a bigger space that you don’t want to give up. Putting the ELACs on top did not alter the impression of space above speed improvement as mentioned before. The ribbon is very fast, no doubt about it, but it won’t transform your speakers into electrostatics. Playing Mozart violin concertos recorded with Anne-Sophie Mutter was very relaxing on the ear, very natural, and neither the loudspeaker itself nor the position of the super-tweeter could be determined by ear, only visually, which is of course what we aim for. My reference recording for super-tweeters is ‘Avratz’ on the album Converting Vegetarians by Infected Mushroom, here the effect was as with other super-tweeters, longer reverb, improved detail, more room and a larger stage, especially in terms of depth. There was never a reason to turn the 4Pi Plus.2 off regardless of music, on the contrary you miss it immediately if it’s disconnected.
Comparing the large omnidirectional ELAC 4Pi Plus.2 with the directional Townshend Maximum super-tweeter, the ELAC is the winner for spaciousness and the Townshend adds little more to the speed. Both make an improvement to both my systems given that they should only add a tiny but very important bit of information. Setting the level too high or the crossover frequency too low results in an unnatural sound or echo effect. Subtlety is key in both cases. Then you are rewarded with more detail, longer decay, tighter bass, plus a more natural musical flow. A preference for one super tweeter over the other is not hard to determine. Although the more expensive ELAC outperforms the Townshend, I will not truly compare both but stick to what the ELAC does for me, mainly because of the large price gap (£1,300). The number one advantage is better use of room acoustics with the omnidirectional tweeter. Set up is very easy and there is no need for roll-in measuring equipment, all you need is familiar music and a good pair of ears. Some help from a friend would help if you find it hard to remember short sound impressions. The other method is to listen over extended periods and plug-in or unplug the tweeters from time to time. The dimensions, the weight and the high price prevents this ELAC from being used on mid-priced loudspeakers or small monitors, I recommend using them with more expensive speakers that are big enough to carry them. Results with the PMC fact.12 are very, very good and it took a while to get used to my system again with only directional super-tweeters back in place.