The Second Rethm Loudspeaker hi-fi+ technical review

One may as well get the question of bass response out of the way as soon as possible and then we can concentrate on where the majority of the music really is. It is difficult to make a sweeping generalisation about the bass characteristics except that it is obviously room dependent. Listening to the double bass was readily believable. Whatever roll off there was, was gradual and gentle. Whilst you could not get earth shattering organ resonances, the organ in Water Lilly Acoustics Trumpet and Organ, Music of the Baroque was well articulated and the balance between the organ and the trumpet was beautifully presented. If you are seeking that 30hz and below response, to the exclusion of everything else, then you will need to look elsewhere. If however you feel that getting the relationship between the elements in the frequency spectrum is more important, then the Rethms will more than satisfy.
It is in the midband that these speakers come into their own, especially with small ensemble and vocal works. Here they are able to present a coherence devoid of those subtle and sometimes not so subtle discontinuities so soften found in multi driver box or hybrid speakers. With the ability to integrate that all important midrange into a seamless presentation it is easy for the listener to forgive and unconsciously forget the lack of bass or ultimate transparency.

If there is one word that sums up these speakers it has to be integrity. They have the ability to present the relationship between instruments and their timbral signatures with a remarkable truth. It did not matter whether one was listening to Kathleen Ferrier, Billy Holiday, or Ute Lemper, the presentation of vocal textures, phrasing and the subtleties of timing were all there to be enjoyed and appreciated. One of my favourite female vocalists is Felicity Wheathers singing Lieder. Apart from her technique, her voice has a liquid quality which through the Rethms came across with an immediacy and a lyric presentation I have never heard before. And it is here that I am not quite sure what I am hearing. There is no doubt that these speakers are able to deliver the energy inherent in the performance with a singular degree of accuracy and realism, however there is a seductive quality which they add to vocals, a timbral gloss which draws the listener into the performance. This is there in the same degree when listening to small jazz ensembles. The energy spectrum of the instruments is dramatically preserved, spatial positioning cues are exemplary, with depth and lateral positioning preserved across the frequency range. I am increasingly convinced that this is due to the single driver presenting a coherence and integration so often missing in multidriver systems. In small ensemble instrumental music the differences between the roles of the instruments is wonderfully clear, not only in terms of timbral accuracy but the energy profile, phrasing, timing and positioning. It is these differences that give the listener an opportunity to understand and appreciate the performance being presented to him or her.


The Second Rethm Loudspeakers by Peter Russell Issue 13 - September 2001 © Images and text copyright Absolute Multimedia UK Ltd 2001
		Mention the word Horn loudspeaker and you get a polarised response. On the one hand people throw their hands up in dismay and declaim; megaphone and huge, no bass and lots of honk. On the other hand they fall down and genuflect in passionate adoration of the past and minuscule powered tube amps. If you then add the dreaded mantra, Lowther, they may well roll their eyes up in despair at upper-mid shout, rolled off bass and treble and DIY cabinets. For some however the word Lowther conjures up the apogee of the single driver loudspeaker. Such passionate responses to Lowther based horn loudspeakers are not always borne out of first hand considered experience. For some the demonstration at some long forgotten Hi-Fi show or vicarious attendance at a dealers' showroom, or friends attempt at loudspeaker building translates into received wisdom. All horns shout and Lowthers honk! This of course is not helped by the myopic adherence of the converted who simply refuse to recognise any limitations or imperfections in their holy grail.
The appearance of yet another horn loudspeaker, and that with a single Lowther driver, has to be received with some trepidation and a touch of ennui. Oh no not again! The whole point about single driver technology is that it is supposed to be able to reproduce the whole audible frequency range; you know, from 20Hz to 20kHz. That is a tall order for an eight inch cone irrespective of advancements in cone technology. With the DX4 driver in the Rethm enclosure we are talking about a frequency range of approximately 50Hz (being generous, on a good day and with a following wind) through to 18kHz. However I am getting ahead of myself. We are talking here about a speaker which stands 1070mm high, 280mm wide and 900mm deep. Not too large for a horn speaker and with its narrow front profile, one that might even fit into a domestic living area. I say might because it really all depends on how the placement of the speakers pans out. They are one of the most temperamental speakers I have ever had to position. That aside, their other distinguishing characteristic is that they have two large differently sized holes cut out of their sides and which run through the width of the cabinet. If it wasn't for the fact that the Lowther drivers were so obviously visible the Rethms could be mistaken for a misplaced Barbara Hepworth sculpture in wood. This sculptural quality is no accident. Apart from the fact that the designer is by profession an architect, the colander and pipe approach to loudspeaker design serves a very real purpose. The holes allow the horn to discharge into the plane of the two loudspeakers. Traditionally the question of how to handle the `horn' in a Lowther based speaker has been to either discharge the horn at the front or the back of the speaker. Either way there is normally some flare in the profile. Usually along its height with the width remaining constant. With the Rethms we are talking about a very different approach. Here we have a pipe with a constant diameter which curves down and round and discharges through the centre of the speaker via two differently sized holes which are full width ports.
			The actual hornpipe/enclosure itself has previously been formed of moulded fibreglass but this has been replaced with cold formed ply which gives a more coherent and rounded sound. The whole enclosure is then braced by side panels that form a frame, which is in turn grounded to the floor by way of four spikes. A stainless steel track with two spikes, one at the front and one at the back secures the frame and stabilises the cabinet providing six points of ground contact in all. Given their weight and bulk they are not a speaker you would want to move around too often. However in the early stages you really have little choice if you want to get the positioning right.
I was fortunate in that Jacob George, the designer, flew over to England on his way to Zurich and was therefore available to assemble the speakers that had been crated from Cochin in India where they are made; the Lowther DX4 drivers had arrived separately. Assembly was straightforward and not too time consuming, with no crossovers or filters to worry about; once the cabinet and the stabilising frame had been assembled, all that remained was to install the drivers. This involved tapping the compression chamber, making the connections and centering the drivers in the pipe opening. Right? Wrong, we had to install a third cone. What on earth is going on here, what third cone? We know that the Lowther drivers are dual concentric but triple concentric; you can't be serious. One of the qualities of the Lowther drivers is the fact that they are made out of paper and are coupled to large magnets. This gives about 99db efficiency, which, in a horn configuration, will result in another 4/5db. The lossy cone and heavy magnet will give high levels of self damping and excellent resolution and detail but there will be a compromised frequency response as the stored mechanical energy will not be dissipated effectively. Complex musical passages may not have the inner detail and resolution that simpler music can portray. The famed 3kHz midrange honk of the Lowther is a narrow band distortion, and according to Jacob, is a result of the intermodulation between the whizzer and the cones in the driver. By interposing a third cone acting as a baffle, which does not touch the other two cones, you ameliorate the potential uplift so often heard with this driver. The cone is held in place by being fixed to a chrome ring, which is locked into an outer fixing ring on the face of the pipe housing the driver. The other factor influencing the upper mid/lower treble peak is the fact that the compression chamber is so designed as to not to allow any rear wave energy to be reflected back onto the driver.
Once assembled and with the auxiliary cones in place, we started with a rough positioning of three feet from the side walls, and four feet from the rear, angled in by 20 degrees. We were ready to play music. A word of caution, these speakers need at least 200 hours of music to break in, and preferably 300 hours. Initially they sound thin and shallow, lacking in body and depth. As the cones break in the presentation relaxes, instruments assume their rightful timbre, and pace and rhythm establish themselves to create a musical harmony. You really have to be patient and persevere.

	Gratification is deferred but all the better for it. So, are these speakers unmistakably Horn speakers? The answer has to an unequivocal yes. They have all the immediacy and presence of a horn but without some of the familiar characteristics mentioned previously. For those of us brought up on the conventional multi-driver box speaker the Rethms will come as rather a surprise; there is an immediacy and an up front projection which creates an initial impression of radiated energy. This is what the Rethms do so well. They project the music into the space not only between the speakers but also in front of their plane. I had to bring the speakers further into the room to achieve a reasonable bass response, which meant that I was listening in a near field position. After protracted listening, I preferred to compromise the bass and set the speakers nearer to the rear wall to move my seat back to row M and not row C. Because of their design, they can be positioned far apart and very close to the side walls. Two feet seemed to get the best bass response and angling in at half the angle between the listening position and the wall ensured the imaging and spatial cues were optimised, but I don't think that I have ever had to spend so much time playing around with the positioning of a speaker as I have with the Rethms.
One may as well get the question of bass response out of the way as soon as possible and then we can concentrate on where the majority of the music really is. It is difficult to make a sweeping generalisation about the bass characteristics except that it is obviously room dependent. Listening to the double bass was readily believable. Whatever roll off there was, was gradual and gentle. Whilst you could not get earth shattering organ resonances, the organ in Water Lilly Acoustics Trumpet and Organ, Music of the Baroque was well articulated and the balance between the organ and the trumpet was beautifully presented. If you are seeking that 30hz and below response, to the exclusion of everything else, then you will need to look elsewhere. If however you feel that getting the relationship between the elements in the frequency spectrum is more important, then the Rethms will more than satisfy. It is in the midband that these speakers come into their own, especially with small ensemble and vocal works. Here they are able to present a coherence devoid of those subtle and sometimes not so subtle discontinuities so soften found in multi driver box or hybrid speakers. With the ability to integrate that all important midrange into a seamless presentation it is easy for the listener to forgive and unconsciously forget the lack of bass or ultimate transparency. If there is one word that sums up these speakers it has to be integrity. They have the ability to present the relationship between instruments and their timbral signatures with a remarkable truth. It did not matter whether one was listening to Kathleen Ferrier, Billy Holiday, or Ute Lemper, the presentation of vocal textures, phrasing and the subtleties of timing were all there to be enjoyed and appreciated. One of my favourite female vocalists is Felicity Wheathers singing Lieder. Apart from her technique, her voice has a liquid quality which through the Rethms came across with an immediacy and a lyric presentation I have never heard before. And it is here that I am not quite sure what I am hearing. There is no doubt that these speakers are able to deliver the energy inherent in the performance with a singular degree of accuracy and realism, however there is a seductive quality which they add to vocals, a timbral gloss which draws the listener into the performance. This is there in the same degree when listening to small jazz ensembles. The energy spectrum of the instruments is dramatically preserved, spatial positioning cues are exemplary, with depth and lateral positioning preserved across the frequency range. I am increasingly convinced that this is due to the single driver presenting a coherence and integration so often missing in multidriver systems. In small ensemble instrumental music the differences between the roles of the instruments is wonderfully clear, not only in terms of timbral accuracy but the energy profile, phrasing, timing and positioning. It is these differences that give the listener an opportunity to understand and appreciate the performance being presented to him or her.
	Like most good things there have to be some limitations and with the Rethms we have already mentioned the restricted bass. At the other end of the spectrum there is a slight loss of shimmer in the highs in some violin recordings, hardly noticeable but there never the less. In the Delmoni recording of Bach's Partita No 2 in D-minor and Kreisler's Recitativo and Scherzo Op 6, the richness of the Cremona violin is captured with all its expressive energy and because the speakers do so much right in the mid range our brain forgives the slight loss at the upper frequency range. Because I had to position the Rethms five feet into the room to optimise the bass response it meant that I was listening closer than I would have ideally liked. This closeness contributed to occasional confusion in the presentation of large orchestral pieces. I'm talking here about the ability to present the layering of orchestral passages where the strings and woodwind have clearly differentiated roles, and in massed choral works where the counterpoint is taken up by the various choirs. The way in which the speakers were able to distinguish the musical complexity and define the role that each of the elements played in the overall performance was not always completely believable, however seductive. Shifting the Rethms so that I was in row m did not really solve the problem. If I had had more space behind me in a larger room then it may well have been different.
With high sensitivity speakers and `horns' in particular, most people's immediate choice of amplification would be low output tubes. This may not be the most appropriate choice if you really want to get the best out of these speakers. Search out good solid-state amplification of about 25 watts and you will be surprised at the speed and control as well as the quality of the lower registers that can be achieved. Using small tube amps with the Rethms might be attractively rich and warm, but you may not get a lot of musical sense, and the speakers' key strength, their musical integrity, may well be compromised. It's a bit like throwing the baby out with the bath water. All those lush second harmonics can swamp and slow the music's immediacy and drive, whereas a good, small solid-state design like my 47 Labs or the DNM PA3S would build on them. Because these speakers contain very little to get in the way of the audio signal, they are able to capture the energy and the structure of the music to the point at which you have no choice but to participate in the music. It is so easy to forget and forgive their shortcomings. However be prepared to feel frustrated if you have a weak link in the audio chain because it will be revealed with a clarity and precision bordering on the painful. The slightest change in the system; cables, cartridge VTA and loading, CD support etc. will become all too apparent. This system transparency belongs to the less is more school of design; how do you know if you have missed something if you have never heard it? The Rethms do not allow you to take things for granted, either about your equipment or your listening prejudices. Certainly you will have to re-evaluate the contribution each piece of equipment plays in producing the listening experience whilst at the same time your familiarity with the building blocks of music will be challenged. But once you have experienced their immediacy and impact and the way in which they engage you in the performance, it will be difficult to be satisfied with speakers that rely on hi-fi credentials in the search for high-end solutions.

	TECHNICAL SPECIFICATIONS The Second Rethm Loudspeakers Type: Single Driver Composite Horn Drive Unit: Lowther DX4 Efficiency: 102dB Impedance: 8 Ohms Bandwidth: 50Hz - 18kHz ±3dB Dimensions (W x H x D): 320x1056x900mm Weight: 40kg each Finish: As shown Price: US$6000 Manufacturer: Rethm 444 South Flower Street, Suite 1688 Los Angeles, CA 90071 Net. www.rethm.com Back to Last Page \| Top \| Forward to Next Page \| Technical Review index