Warning: The following pages contain an odd mixture of writings/photographs which haven't been kept uptodate as my project evolved. It was put together in the first half of 1996. Please read "What I now listen to" on Bill Alford's web site to correct various deficiences in this page. Bill Alford
Carver Drivers Mounting Details
The drivers were purchased by Bryan from Carver and mounted on open baffles in Canberra, Australia. There is not much DIY skills needed to mount the drivers on open baffles. Bill subsequently had the Carvers at his place for an extensive period of evaluation.
The speaker system is based on Doug Purl's Carver Kryptonite plans from the bass and DIY loudspeakers mailing list together with some alterations of our own. The decision was made to mount the ribbons and the woofers on separate baffles for the following reasons. We reasoned that the imaging of the system would be maximised due to the narrowed ribbon baffle. Employing a dedicated baffle for the ribbons will isolate it from vibrations caused by the many bass drivers employed in this system.
A close-up of the Carver ribbons/woofers at Bill's place
As mentioned in the Hi-Fi World articles referred to in the technical description of the Carvers, the bass panels have conflicting positioning requirements for flat in-room bass response to the positioning requirements of the ribbons to maximize imaging. The 60" (152.4cm) ribbons are secured by screws onto two pieces of solid ash hardwood, 185cm (72.8") high by 11cm (4.3") wide by 19mm (0.75") thickness. The total width of the ribbon baffle is 35.5cm (14"). The bass section consists of 5 12" (30.5cm) woofers per side which are mounted on a dedicated baffle board. The bass baffles are constructed from 18mm (0.7") particle board. This baffle closely approximates Doug Purl's Kryptonite model. They are 71cm (28") wide at the top increasing to 91cm (35.8") at the bottom, 194cm (76.4") high. The holes to mount the woofers in were readily cut out perfectly using a router. The nails at the top of the bass baffles were added to hold away from the woofers old curtains draped across the bass baffles to protect them from direct sunlight and dust when not in use.
A close-up of the back of the Carver ribbons/woofers at Bill's place
The panel materials used are due to economic considerations only and in no way demonstrate the drivers to their maximum potential. It is important that this point be emphasised because this is the only form in which we have had exposure to the Carver ribbons and we think that with proper mounting this would reap major sonic benefits.
Technical Details on Carver's Line Source Dipole
The way good dipoles work comes down to understanding what the ear/brain does with time delays due to reflections. Simplifying things, very short delays, such as 0-2msec, are used to assign the direction of the sound and this time interval is crucial in forming a stereo image (cabinet edge diffraction, etc falls into this range). Longer delays, up to 50msec, are grouped to form an ambient impression. Delays longer than 50msec become discrete echoes. Sound travels about 14 inches in 1msec.
Provided we don't overdo room reflections (like Bose does horribly) and control them, we can use these room reflections to enhance ambience and the depth of the stereo image, as a good properly placed dipole does. These room reflections can also cause destructive cancellations at some frequencies as in the case of floor and ceiling bounce and in the low bass. Floor bounce is typically in the 2 to 3msec range (a crucial time delay) and is one of the things which gives away the fact that we are listening to speakers. The ceiling bounce is more benign, since it arrives later, around 4-8msec (high ceilings help here). Ceiling bounce becomes important when we have suspended ceilings (which should be avoided). Good line source dipoles have a desirable dispersion pattern. The dispersion pattern is such that in plan all the energy goes to the front and back in a figure of eight pattern, with no side dispersion, which minimizes reflections from side walls. In the vertical plane all of the energy is confined to being a parallel projection out from the line source dipole, thus minimizing floor and ceiling bounce. The problems of low bass will be dealt with below. The setting up of a good dipole in the room is more complex than a monopole. The room has to be large and the dipole away from the back wall. However, the dipole has some good characteristics lacking in monopoles that can be used to great advantage.
The Carver line source dipole consists of a dipolar ribbon on an open baffle working from 200Hz up. Below 200Hz is covered by line source dipolar woofers on an open baffle. The ribbon is made from 0.00035" thick aluminium bonded to DuPont Kapton film 0.0005" thick by a subcontractor to Carver who specializes in adhesive technologies. Four quarter-inch aluminium foil strips with an extra space between each pair of aluminium foil strips are used (over the extra space is put a row of magnets). As the 4" wide aluminium foil bonded to Kapton film comes off 100 metre spools, it is run through a crinkling machine comprising special rollers that squeeze a leather texture into the material. The crinkling is done to suppress membrane vibration modes. Carver then uses a patented technique to uniformly tension the film on a particle board rectangular frame. The ribbon is then clamped and electrically bridged at both ends and suspended in a strong linear magnetic field over its entire length provided by thirty linear feet of 6" bar magnets glued into a metal frame. The 60" Carver ribbons consist of two half-inch ribbons with a folded "voice coil" of 20' long suspended between three double rows of magnets. The ribbon speaks through the two vertical half-inch ribbons, there being a row of magnets centrally located between them (which you may pick out on the photographs). The cavity in which the ribbon speaks from also leads to a geometrical cavity resonance which is taken care of by the crossover. The ribbons have a constant resistive impedance of 4.6ohms.
The aluminium foil bonded to Kapton film after crinkling.
The 200Hz crossover point for the ribbon is recommended because there is a membrane resonance slightly below 200Hz due to the tension in the film. There is also a larger geometrical resonance at 140Hz due to the 60" length of the ribbon and these resonances show up in a review of the Genesis II.5 speakers in Jan 1995 Stereophile which uses this same ribbon for good reason. An active Clearview crossover was used in this implementation to overcome the falling ribbon response near crossover due to quarter wave cancellation on the ribbon open baffle (there is more on this later), null the cavity resonance due to the width of the cavity the ribbons sit in and overcome the ribbons fall off in the extreme treble. A third order (18db/octave) crossover rate on both sides is used to the woofers at 200Hz. An active crossover gives flexibility at the expense of the need for two stereo amplifiers.
The following information is needed to understand what Carver has done with the bass panels which operate below the crossover frequency of 200Hz. Herewith follows a lesson by Dick Pierce from a posting of his on the newsgroup rec.audio.tech, 14 Nov 1995:
""Q" is one of those dimensionless numbers that causes no small amount of consternation amongst those who don't understand what it means, as well as among those that THINK they do! However, the principle behind Q, when used in the context of loudspeakers, is VERY simple. It is simply the ratio between energy storing and energy dissipative mechanisms at resonance. In electrical terms, it is the ratio of the reactance to the resistance.
A high Q indicates that for the amount of energy stored in a resonant system, the mechanisms that dissipate that energy are small. So a high-Q system will tend to have a resonance that decays slowly, because the amount of resistance available to dissipate the energy is small compared to the amount of energy stored. A low-Q system will tend to dampen the resonant motion quickly, because the energy is dissipated quickly and removed from the resonant system.
There are primarily 2 energy dissipating mechanisms available in a loudspeaker driver: mechanical and electrical (there is another, acoustical, but it is VERY small when compared to the other mechanisms). The mechanical dissipative mechanisms are primarily the frictional losses in the driver's suspension, and, to a lesser extent, acoustic absorption. There are, essentially, two electrical mechanisms for energy dissipation: the DC resistance to the voice coil and the output resistance of the amplifier. In almost all cases, the DC resistance of the voice coil completely dominates.
These two mechanisms, mechanical and electrical, determine, respectively, the mechanical Q (Qms) and the electrical Q (Qes) of the loudspeaker driver. Their parallel combination determines the total Q (Qts) of the loudspeaker driver." Amen.
When we mount a loudspeaker driver onto a baffle system we also have to take into account the Q of the baffle system to arrive at the total system Q. To work out the total Q of the driver and baffle system you simply multiply the baffle system Q with the total Q of the loudspeaker driver. Closed boxes store energy that interacts with the loudspeaker driver in complex ways, especially in vented enclosures. Boxes themselves also have resonances. Normally a high-Q closed box is combined with low-Q loudspeaker driver to give a desirable total system Q. But when we mount a loudspeaker driver on an open baffle this situation is reversed. An open baffle stores no energy and has a low-Q of 0.2 and Carver chose to use a high-Q woofer with a total Q of 3+ to arrive at a desirable total system Q.
Carver's high-Q woofer was also chosen for another good reason to do with mounting a woofer on an open baffle. As we decrease in frequency or increase in wavelength, the system initially behaves as an infinite baffle. When the wavelengths are long enough to be a quarter of the baffle dimensions, the waves begin to cancel each other around the edges of the dipole baffle. The wave travels out to the edge (1/4) and back to the opposite side of the vibrating speaker cone, where it is exactly out of phase and cancels out. Quarter wave cancellation on an open baffle is a first order phenomenon - the roll-off occurs at 6dB per octave. When we reach the free-air resonance point of the high-Q woofer we add to this the second-order sub-resonance fall-off of the high-Q woofer to end up with a third-order or 18db per octave fall-off below the free-air resonance point of the high-Q woofer (this makes a good rumble filter in the Carver case).
In loudspeaker literature we can look at the family of curves for the frequency response of a loudspeaker driver on an infinite baffle as we decrease the frequency. Starting with the rolled-off curve when Q=0.5 (critically damped), then the Butterworth graph with Q=0.71 (maximally flat), then a little ripple at Q=1, then clearly a bumped-up graph at Q=1.4. When the Q is higher than any you can usually find in loudspeaker driver catalogues you start to get boosting above the resonance point of the loudspeaker driver, and a sufficiently high-Q will result in a slope of about 6dB per octave above the free-air resonance point of the loudspeaker driver. This increase of 6dB per octave of the high-Q loudspeaker driver can be used to counteract the 6dB per octave quarter wave cancellation to give a flat frequency response right down to the free-air resonant frequency of the loudspeaker driver. This is a much more elegant solution to the problem of quarter wave cancellation on an open baffle to that used by Celestion, etc of using a conventional low-Q woofer with electronic equalization since it does not involve additional amplifier power and the necessity of electronic equalization equipment. High-Q woofers are relatively easy to design/make. Both ways of overcoming quarter wave cancellation on a baffle entail the use of long throw woofers for the safe operation of the woofer.
In the Carver case a large sloped open baffle is used with at least three 12" high-Q woofers mounted on it in a line source dipolar array. The sloping of the baffle spreads out the frequency at which quarter wave cancellation occurs on the baffle and makes it look not so big. The large open baffle has a low spouse acceptance factor and needs to be in a large room away from the back wall. The reason for using multiple woofers is that it takes four times or 6dB more amplitude on an open baffle at resonance than an equivalent sealed box to achieve the same level of sound output. With the Carver 12" (30.5cm) woofers Carver uses a special technique to roll the foam surrounds under pressure to get the proper low resistance in them. Small magnets with a light stiff paper cone and modified spiders and the most flexible annulus yet devised are used to raise the Q of the Carver woofer. The Carver woofers have a DC resistance of 16 ohms so that the overall resistance of them when multiple woofers are connected in parallel on one open baffle is still reasonable. The Carver woofers have a maximum linear excursion of 3cm (1.18") and maximum mechanical travel of 5cm (2"). The Carver woofers have a free-air resonant frequency (fs) of 22Hz and when mounted on the above open baffle are nominally flat down to the fs frequency of 22Hz with an f3 frequency of 17Hz. At the free-air resonant frequency of 22Hz the woofers will flap around, but I have yet to see this happen on any music that I have played on this system, low frequency pipe organ notes and all.
One major problem that was referred to earlier is room interactions with dipolar bass. The article in Nov 1991 Hi-Fi World and its follow up article in Dec 1995 have a lot to say on this. The following enigmatic sentence from the Nov 1991 Hi-Fi World article sums this up. "Whilst room alignment is difficult and we have no verified empirical rules for it, when a dipole has been room aligned successfully it will give more even sounding bass than a monopole." The flatter in-room response of bass dipoles is achieved by toeing them out suitably (rather than in) and thereby using cancellation effects to suppress room-resonance modes. However, the optimum bass configuration conflicts with the optimum imaging configuration, which requires toe-in. Thus, if Celestion is right, the only practical means of optimising in-room bass and imaging in planar speakers is by the use of separate baffles for woofers and the mid-range/tweeters. In any event, it would be helpful if Celestion's computer program or similar to aid in arriving at the optimum position for a dipolar bass panel in a room was more widely available, rather than being limited to empirical means for finding this.
Bill's Listening Setup
The room is on the western end of a solar house aligned along an east west axis and is essentially a 7.1m (23.3') square with one wall of complete curtained glass jutting out to the north in a isosceles triangular fashion to a length through the centre of 9.5m (31.2'). (Readers in the northern hemisphere will have to readjust). The room has a timber lined cathedral ceiling which is 2.4m (8') at its lowest height rising to 4.6m (15') at the centre. All the interior walls are brick. The listening room enters onto a kitchen which partly extends the width of the listening room by a further 2.7m (8.9'). The listening room also enters onto a corridor 17.5m (57.4') long, 1m (3.3') wide, which runs the length of the rest of the house on the southern side. The corridor is a low bass freak's nirvana as the total length of 24.6m (80.7') can in theory support a fundamental frequency of 6.7Hz and much air movement has been set up on low bass notes in this corridor.
The listening room has a very live acoustic which exacerbates brightness. Along the western wall of the room is a brick fireplace and the ribbons are placed in front of the raised hearth of the fireplace, 1.7m (5.5') from the back wall with no toe in. The bass panels are to the side of the hearth, 1.34m (4' 5") from the back wall and with a small amount of toe out as discussed in the Hi-Fi World articles referred to in the technical description of the Carvers.
A series of measurements was done with the bass panels beside and behind the ribbons to arrive at the best compromise in-room bass response which confirmed the statements that have just been referred to. The best compromise was with a small amount of toe out. This positioning of the bass panels also has the advantage of slightly less apparent frontage for them. The distance between the ribbon centres is 2.6m (8.5') and the woofer centres is 3.3m (12.5').
These speakers need a large room away from walls, children, animals and disapproving spouses/persons. Bill thought that he would never see the day when speakers would dominate in this room but the Carvers do. Large Duntech Black Knight speakers in this room didn't look imposing (they have about the same height as the bass panels but half their width) but it is going to be a good camouflaging job to hide these speakers in this room. Everybody that Bill has shown pictures to of these speakers so far has been impressed with their physical size and the number of drivers but one has to live with them too. People, when they first see these speakers, will invariably walk right around them in amazement.
The associated electronics for Bill's room are as follows: a Marantz CD50 CD player used as a transport which has had a Simply Physics Isodrive and Trichord Clock 2 CD modification fitted. This feeds into an Audio Alchemy multibit Digital Decoding Engine V3.0 DAC. The preamplifier is a solid state Metaxas Audio Systems (MAS) Marquis. Australian high end audio firm Metaxas Audio Systems makes distinctive electronics. The preamplifier output feeds a modified Clearview active crossover. The Clearview active crossover has the small valued blocking output capacitor on the bass output replaced by a 10mF polypropylene capacitor to give it far more bass extension and a 20Kohm potentiometer put across the ribbon output to allow adjusting the levels coming out of the ribbon and woofer panels to be the same. The power amplifier to the constant 4ohm load ribbon panels is a solid state MAS Solitaire rated at 120wrms into 8 ohms which never heats up. The bass woofers are driven by an ordinary Australian made solid state ME75 power amplifier rated at 190wrms into 8 ohms. The ME75 amplifier has ample power into the low impedance of 5 16ohm woofers connected in parallel per side which gives a nominal load of 16/5 = 3.2 ohms.
Bryan's Listening Comments
I always get the feeling that the Kryptonites (as outlined by Doug Purl on the bass and DIY loudspeakers mailing list) are constantly testing every other variable in the reproduction chain and they never seem to be at fault. Properly set up and with sympathetic ancillaries listening to these speakers is an event. I have never been entirely happy with any of the speakers that I have owned in the past: Apogees, Duntechs, original (but modified) Quad electrostatics, Acoustat 1+1s, Audio Definitions, Allisons (4 plus the 1), Tannoy 15" (38.1cm) dual concentrics, KEF transmission lines, Lowther Acousta horns and Magneplanar Tympanis. I have liked certain aspects of each of these speakers in the past: Apogees on voice, Duntechs for image height and solidity. Original Quads (sans grills/damping material behind panels and placed in a D'Appilito configuration on rigid stands) for almost everything except macro dynamics, lack of impact and bass quality and response. Acoustat 1+1s for image height and pinpoint image width, Audio Definitions for the bass, Allisons (model 1) for smoothness, the honeyed tweeter and the feeling of unburstability, Tannoys for macro dynamics and impact. The KEF transmission lines have good upper bass plus pretty good bass extension and the Lowthers for their micro dynamics and life. The Magneplanar Tympanis were fairly coherent and had a nice treble.
After living with each of these speakers over a period of time various perceived shortcomings become apparent. The Carvers so far have not. They do all of the hifi buzzword things incredibly well showing almost all of the strengths of the above mentioned speakers with none of their perceived weaknesses. The only gnawing doubts I have are that the bass although it goes much lower than any other speaker I have ever heard, with or without subwoofers, seems to lack the impact and punch that horns and some bass box enclosures can have. The bass through the ribbons/woofers is perhaps more natural; certainly incredibly detailed, coherent, uncoloured and effortless but sometimes I want more punch and slam that a few of the above mentioned designs exhibit.
However I do not mean to suggest that these speakers will be to everyones taste. Something like a Tannoy 15" (38.1cm) dual concentric in a large enclosure sounds like you are in a recording studio listening to a live feed over monitor speakers from the recording session in the next room. Altec 15s with large sectoral treble horns (as used in theatres to produce a sound which pins you to the seat) sounds like Pink Floyd (or whoever) is in your listening room with a stack of PA bins in front of you, warts and all. The Altecs have a live, hard hitting, very resolving and incredibly dynamic sound coupled with a visceral quality that I have not heard before. So it's horses for courses as they say.
These ribbons are very special. They are the only speakers that I have listened to that have such a formidable suite of strengths: dynamics, bass to midrange to treble blend and tonal accuracy (which is crucial in my list of listening priorities), delicacy, vocal clarity/articulation and massive soundstage. These are the only speakers that I have come across that when I put on a recording, if it is of sufficient quality, before the music begins you can sense the size of the acoustic space in which the recording took place. I suspect that this may be due to their dipolar nature and sensitivity which is higher than any other dipole that I have heard coupled with outstanding bandwidth. This experience is the same as when one enters a huge cavernous space such as a large auditorium, church or mine deep below the earth and you can sense the size of the acoustic space.
A valuable strength of these speakers is that they faithfully track the ebb and flow of the music, not changing their character as the music gets louder. Every other speaker I have heard changes its sound to some extent as the music changes volume. I think that this is a very important aspect of music reproduction where most speakers seem to have gross shortcomings. The frequency spectrum is handled in a very even handed way; the dynamics, power and transparency being consistent throughout the entire frequency band.
In Bill's listening room the Carvers have a huge sound stage and are magnificent on large scale orchestral or opera material, however, though still front rank, not as good on small scale works. The bass in Bill's listening room lacks power and impact. In Bill's listening room the sound is very detailed and free breathing with lots of air, and space around instruments with the rear wall, side walls, floor and ceiling reflections being reproduced if it is on the recording, but the sound for me is a little too hifi and artificial sounding and slightly brittle. Transients in Bill's listening room can be very sharp but the power range of the orchestra is too thin, weakening the timbre of some instruments. I think that this bright thin brittle quality is for the most part due to the very live room.
Bill's Listening Report
After what Bryan has written I'll just add my own extra thoughts as I concur with practically everything the Bryan has written. Bryan, having younger ears than mine, can hear above the highest frequencies that I can hear (which can also have its problems) and coming from a different background he listens for different things.
Many attributes of the sound from the Carvers show up the excellence of the Carvers: the lack of image height, the depth and width of the stereo image, the coherence of the system, the resolution and accuracy of the sound and the lack of room interactions other than the back wave. Stereo recordings cannot record image height and thus when played back shouldn't have any image height. More information on how to record/reproduce image height can be found on the ambisonics WWW page. The lack of image height of the Carvers is due to the lack of room interactions and lobeing. Multi-driver Duntech Black Knights in this same room could give plenty of image height because of these faults. The Chesky Test CD 1 (Chesky JD37) with the LEDR test for image height does appear to have some small image height with the Carvers but nowhere near as much as on all other speakers in this room. The Chesky LEDR test for image height appears to be bursts of signal covering the whole frequency spectrum with suitable notches in them between 8 and 12kHz to mimic the usual learned cues for image height. These notches mimic the typical cancellations due to reflections of sound in the outer ear when listening to something above and in front of you. You don't have the problem of the various frequencies coming from various "vertical" parts of the stereo image that multi-driver speakers have because with the Carvers everything is on the "one plane". This "one plane" also follows ones head height, moving up and down with ones head height unlike with box speakers where the tweeter is usually positioned to be at normal listening height and things change when you move out of that position.
The good depth of the stereo image is due to the dipolar nature of these speakers but the back wave from the reflective brick wall in Bill's place can also lead to brightness when the volume is turned up. Bill intends to try to cure this problem by adding absorptive material on the back wall. The large width of the stereo image is obvious in listening when you sit way back from the speakers. One note about the stereo width is that on the Chesky Test CD 1 where the speaker is way out on either side I can detect David Chesky way out on the left hand side due to what appears to be some room interactions on the left side but I can't detect him as being way out on the right hand side due to the lack of room interactions there where the wall juts out. My initial reactions to ribbons was coloured by my experience with Apogee ribbons where the sweet spot was but one head width wide and head height high. The Carvers don't have this problem due to their dispersion and you can sit quite a way off axis and still get a good stereo image, unlike with other speakers in this room like the Duntech Black Knights, but that is a long story.
One attribute of good speakers is that nothing should stand out as being unnatural and the Carvers excel here. It takes sometime to appreciate this fact with the Carvers because they don't initially grab your attention like other speakers but once appreciated I soon notice faults in other speakers by comparison. The ribbons are smooth, accurate and coherent and don't have problems like ringing metal dome tweeters. The accurate low bass performance of these speakers readily conveys information about the acoustics of the recording venue or the physical effects of low bass. I appear to have had more feedback about this from the Duntech Black Knights with two 12" (30.5cm) Dynaudio woofers per side mounted in a sealed box because they appear to have been bass heavy and could get down to house shaking low frequencies, room resonance modes and all, even if it was not too accurate. Some judicious boosting of the low bass in the active equalizer may give up even more information in this frequency range plus more punch to transients in Bill's room, not that the Carvers are too lacking here. Below the free-air resonance of the woofers at 22Hz the bass panels go off at the rate of 18db/octave and they become unloaded which can lead to large possibly harmful excursions of the woofers despite their long throw so one has to be careful in this low bass boosting. There are no problems with transients or impulses and this is where the coherence of the Carvers shows up. At Bryan's place with the panels further out in a longer room the bass was much better, being as much felt as heard and standing wave problems were setup. Doug Purl also reports that in his room the bass is also as much felt as heard. The woofers do run into problems with the claimed 5Hz and other infrasonics on Telarc's Great Fantasy Adventure CD (Telarc CD-80342), but I would not have expected otherwise of most speakers at this frequency. Telarc's Great Fantasy Adventure CD is a typical Telarc gimmick. I wonder how good conventional woofers in boxes like the NHT 1259 together with the Carver ribbons compare on low bass?
I listen by choice to only "classical" music. The Carvers do an excellent job in sounding exactly like the concert hall experience within the limitations of stereo recording. I am well acquainted with the concert hall experience. I have enjoyed immensely listening to many full orchestral recordings with the Carvers and can picture all the sections of the orchestra layed out in front of me on good recordings. These speakers readily show up the good and bad points in a recording or performance and be prepared for the bad aspects. Many recordings will be shown to have extraneous live noises in them due to the excellent resolution of the Carvers. The Carvers excel on the Chesky Ultimate Demonstration CD (Chesky UD95) and particularly on well recorded piano and similar transient rich recordings, the hallmark of an excellent speaker. I well remember hearing the Carvers for the first time on piano and remarking that the piano was in the room (the same thing occurred with some ludicrously expensive Genesis speakers with the same ribbons).
Some experimentation will have to be done to get the panels placed well. Putting them too close to the back wall will bring out problems with cancellation in the back wave. These speakers will always have some cancellation going on in the back wave and it is a matter of placing them as far out into the room for a good compromise with this, plus still using the room for listening and other things. The separation between the panels will also involve some compromises. If they are spread too far apart things may collapse in the centre of the sound stage but the stereo width will be large. Putting the panels closer together will decrease the stereo width and may be desirable for some small scale works (and addresses the problem that Bryan has noted and I too have noticed, a problem with dipoles) but not for other works. In spite of some initial contrary thoughts I haven't observed any problems with the relative positioning of the ribbon and woofer panels. There appears to be no problems around the crossover frequency of 200Hz between the ribbon and woofer panels after adjusting the active crossover. All usage of the ribbons so far has been done with them vertical and no attempt has been made to observe what happens when this is changed as suggested by Doug Purl. I note that in the Genesis usage of the ribbons they are also vertical. I plan to do some measurements of the Carvers when I have the necessary equipment but I expect them to confirm what my ears are telling me.
It is planned to mount the ribbons and woofers on better open baffles with more aesthetic appeal. After seeing a sample of Makassar ebony one could do better than Shun Mook Mpingo ebony discs and mount the ribbons in expensive ebony (and not the boot polish variety) and not have to piano lacquer anything. Perhaps wood winds and pianos and other things using ebony will then sound better. Expensive corian or polished marble or granite is another alternative. No, Australia has some beautiful decorative timbers like Tasmanian blackwood, oak and myrtle, Victorian mountain ash and satin box, Queensland walnut, quarter sawn silky oak, silver ash, maple, cedar and brush box, Western Australian jarrah, and she oak and all the richly circularly figured burls. 25mm (1") and thicker (32mm (1.26") or 36mm (1.42")) veneered MDF woofer panels are going to be heavy and sturdy. Bill plans to make the woofer panels in three sections with the two side panels mounted on piano hinges for folding back when they are not in use to decrease the woofer panels frontage. The sound when the woofer side panels are folded back could be interesting because we are in a different situation with regard to quarter wave cancellation on the baffle. Some experimentation will also be given to improved ancillaries and crossover and changing the crossover to judiciously boost the lower bass octaves.
It is hard to answer the question of where do these speakers rank compared to other speakers because comparative listening has not been carried out with the best speakers around and the possibility of this happening is small. I have listened to the large Wilson X-1/Grand SLAMMs and the Carvers overall were at least on a par with them despite the lesser bass punch of the Carvers currently and the Carvers are a great bargain when compared with the large purchase price of the Wilsons. It is interesting to note that the Wilson Grand SLAMMs, like Alons, are semi-dipolar. The knuckle test on the wondrous material that the Wilson Grand SLAMMs are made from, a proprietary phenolic material, sure shows how dead it is and it is to be hoped will make its way into other speakers, etc. It would be ideal for the Carver baffles. People listen for different things in speakers but it is Bill's opinion that the Carvers are the best compromise in speakers that he has listened to for his needs so far and things can only improve. A sure indicator of this is the fact that Bill hasn't felt the urge for better speakers after his experiences with other speakers.