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Tony Moore's Ribbons

The following was posted to the bass mailing list under the title "The Ribbons of Life (long)"

Attached to this posting are three gif files which were all measured using a friends IMP system. I apologize in advance to anybody who can't view these gif files immediately and suggest that they get the appropriate hardware/software to do this. I've purposely chosen to use gif files for compatibility reasons in world wide web browsers. When I get the time to make up my IMP system more measurements may follow and this posting is to be regarded as work in progress. I'm using past postings to the bass mailing list that I've archived away and I believe aren't currently publically available. Something should be done about this as there is much useful information in them. The current bass mailing list archive could also be improved. A lot of what I regard as unnecessary questions that are being asked on the bass mailing list have answers in the archives if only they were more readily accessible as for example like I recall the analogue addicts list being. The first attached gif file is the frequency response curve of my Clearview CXR-1 Active Crossover. Andre Yew confirmed this frequency response curve when he posted the following:

>From: andrey@ugcs.caltech.edu (Andre Yew)
>Date: Mon, 7 Nov 1994 22:25:08 -0800
>To: bass@lunch.engr.sgi.com
>Subject: Re: Carver Ribbon Descriptive Epithets
>	For those who are interested, the Clearview crossover has a general
>shelving up of bass frequencies from 200 Hz to 1 kHz by about 2dB, with
>a 3 dB peak at 200 Hz.  There is a 4 dB notch at 2 kHz that's about 1 kHz
>wide, and a 2 dB notch at 8 kHz that's about 5 kHz wide.  This is with the knob
>turned fully clockwise.
Doug Purl also confirmed most of this when he posted the following:
>Date: Fri, 16 Sep 1994 14:27:12 -0600 (MDT)
>From: Douglas Purl 
>Subject: Re: carver ribbons
>To: bass@lunch.asd.sgi.com
>On Fri, 16 Sep 1994, Don Perley wrote:
>> A couple of quick questions on setting up the ribbons:
>> 1) Do the 60 inch ribbons have minimum baffle requirements, or is it anything 
>>    sufficient to hold them up?
>Yes.  A minmum of 12" wide.
>> 2) Do any of the corrections in that electronic crossover involve assumptions
>>    about the baffle size? (wrt the ribbons... I am going the 1259 route for
>>    the woofers.)
>The notch filter and the high-frequency ramp do not.  I am told the notch 
>center is 6.5 kHz and not 6.1 as reported in Carver literature.  The 
>high-frequency ramp is 7 dB above reference above the notch filter.  The 
>low-frequency boost is 3 dB ca. 330 Hz rising to 5-6 dB at 250 Hz and 
>then following the 3rd-order 200 hz xover.
I had more to say about the recommended 12" wide open baffle in the following posting:
>Subject: Carver's baffle
>To: bass@lunch.engr.sgi.com
>Date: Fri, 25 Nov 1994 12:01:01 +1100 (EST)
>From: "Bill Alford" 
>I've read back through Doug Purl's past postings and he
>states that Carver states that the ribbons should be mounted on a 12"
>wide baffle. A 12" wide baffle will lead to 1/4 wave cancellation at
>284Hz, something that we don't want. Quarter wave cancellation at 200Hz
>will occur on a baffle 17" wide, and I would recommend trying a baffle
>17" wide and swept back in much the same manner as in an article in Speaker
>Builder, 5/1993. I've had another look at the Genesis 2.5's and they
>have a lot of sweeping back of the baffle. This suggestion will take sometime
>to realize physically and experiment with. The active crossover may
>already have some compensation built into it for a 12" wide baffle and I
>would like some more details about the active crossover.
The frequency response curve of the Clearview Active Crossover confirms that there is compensation built into it for the quarter wave cancellation of 6dB/octave on a 12" wide baffle below 284Hz.

As far as I know, there has been no discussion so far on this mailing list as to why there is a notch at around 2kHz in the frequency response of the Clearview Active Crossover. I suspect that it is there for similar reasons to the notch at 6.5kHz that Doug Purl wrote about above. I'm also wondering if the following posting has some small relevance to this:

>Date: Mon, 28 Nov 1994 12:42:29 -0700 (MST)
>From: Douglas Purl 
>To: bass@lunch.engr.sgi.com
>Subject: Re: more Carver ribbon mounting questions? 
>> 2.  Doug's specs on building the baffle call for insetting the ribbon
>> 1/2 inch into the baffle from the back.  If so, the ribbon will stick
>> out another half inch or so from the back.  Is this correct?
>I don't see that it is imperative to do it the way Carver did it.  One 
>problem is that construction method places ugly bolts and nuts on the 
>face of the ribbons, and Carver chose to hide them by insetting.  Genesis 
>flush mounts the same ribbons.  Shadow masking the front of the ribbons 
>places their motor plane closer to that of the four woofers in the 
>open-baffle configuration, though I don't think matching the relative 
>position of the drivers is a big deal at a nominal 200 Hz crossover point.
As an aside, I hid the "ugly bolts and nuts on the face of the ribbons" behind upholstery plastic black screw caps held on with blue-tak and Carver could have done something similar that would have been more aesthetically pleasing for Genesis and others.

The following posting addresses the notch at 6.5kHz (and 2kHZ?) in the frequency response of the Clearview Active Crossover:

>Date: Mon, 7 Nov 1994 17:28:56 -0700 (MST)
>From: Douglas Purl 
>To: bass@lunch.engr.sgi.com
>Subject: Carver Ribbon Resonance
>On Mon, 7 Nov 1994, Andre Yew remarked concerning the Carver ribbons:
>> > 	I find the drivers steely sounding on some recordings.  Recently,
>> > I've heard it said that you can never cancel a resonance, only surpress it.
>> > I'm guessing that the resonances in the ribbons are what's causing the
>> > steely sound.  I've measured the Clearview crossover, and it does appear to
>> > surpress the resonances, but is it enough?
>Don Perley responded:
>> I'm not sure what the nature of the resonance is, except that it's
>> up around 6 khz. (hmm.. wavelength is about equal to the width
>> of the slot through which the ribbon sees the world on the platinum)
>> Anyway.. resonance generally gives you some ringing.  That is, you keep
>> getting vibrations for a few cycles after the signal is removed.
>> The equalizer can flatten the response at resonance, but the ringing
>> (if there) will remain.
>This is not a ringing resonance.  There are no mechanical elements going 
>into undamped oscillation.  This is a narrow-band emphasis caused by the 
>cavity produced by the metal box in which the film diaphragm and ribbons 
>are housed.  The side-to-side cavity resonance does not cause an effect 
>because it is parallel with the membrane.  The front-to-back resonance is 
>notable, however, and must be dealt with by means of complementary 
Doug Purl has mentioned above a high-frequency ramp in the frequency response curve of the Clearview Active Crossover. Doug Purl privately e-mailed the following to me on this and I don't recall this information ever getting onto this mailing list before:
>Date: Fri, 7 Oct 1994 01:49:18 -0600 (MDT)
>From: Douglas Purl 
>Subject: Re: Carver ribbons
>To: Bill Alford 
>Another thing about the Genesis configurations is they cut off the Carver 
>film drivers prior to the cavity resonance and add the coherence-harming 
>additional passive filter and tweeter.  The Carver group decided there 
>was so much power handling capacity at high frequencies in the 48" and 
>60" ribbons that with a little ramp they compensate for what they believe 
>is hinging at high frequencies.  They think the film that carries the 
>ribbon conductor begins to move out of phase with the rest of the film 
>diaphragm and produce the upper octave.  Since the radiation area is cut 
>down, the response ramps down 6-7 dB.
I prophetically posted the following to the bass mailing list:
>Date: Mon, 7 Nov 1994 11:39:48 +1100 (EST)
>From: "Bill Alford" 
>Reply-To: bass@lunch.engr.sgi.com
>  What then do I see that can be improved in the Carver compromises?
>There are two main areas that I have been wondering about. The extreme
>treble of the Carver ribbons I suspect is one of its weaknesses and
>Genesis has used a solution which I suspect is the way to go inspite of
>Doug Purl's warnings in this area...
Doug Purl also added the following recently:
>Date: Sat, 10 May 1997 22:03:46 -0600 (MDT)
>Reply-To: dcp@selway.umt.edu
>Sender: owner-bass@mcfeeley.cc.utexas.edu
>From: Douglas Purl 
>To: bass@mcfeeley.cc.utexas.edu
>Subject: Re: monopolar BG ribbons 
>X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN
>On Sat, 10 May 1997, Danny Bekhor wrote:
>> I'm also anxious to find out whether the BG are rolled off at the top. 
>> I believe they need the same EQ on the low end, unless used in a very wide baffle like the 
>> Genesis or in a 7x14 box like Dzurko Acoustics.
>> I'm not sure it was mentioned before but it's worth to look at 
>> http://www.audioc.com/rib1.htm 
>> for more info about the VLS Model 1 PPMP by Dzurko Acoustics. 
>> It looks like BG is making the drivers for them. I'm not sure I understood why are they 
>> different, and what exactly is the difference between these and the RD75.
>You can expect all film drivers that alternate foil glued to the film with
>areas of clear film to have a high-frequency shelf.  It's the nature of
>the vibrating medium and the stiffness of the film.
>Doug Purl
The extreme treble of the Carver ribbons is indeed a major weakness. The second attached gif file of the measured combined response of the Clearview Active Crossover plus Carver 60" ribbon mounted on a 13 1/2" wide open baffle shows that it is way down even after ramping it up in the Clearview Active Crossover. In this measurement the midrange potentiometer of the Clearview Active Crossover was set to 0dB, i.e. in the centre of its range, and only the initial impulse output of the ribbon itself was used i.e. all backwave and other reflections were gated out in the computations. One day I may get an IMP measurement of the frequency response of Carver ribbon itself. Comparative listening confirms that the Carver ribbons fall away badly in the extreme treble. The Bohlender-Graebener ribbons don't appear to suffer from this as mentioned in the following recent posting and I'm curious to get more information about this:
>Date: Mon, 12 May 1997 09:06:16 -0500 (CDT)
>Reply-To: krogan@asic.sc.ti.com
>Sender: owner-bass@mcfeeley.cc.utexas.edu
>From: Kevin Rogan 
>To: bass@mcfeeley.cc.utexas.edu
>Cc: katz@mack.space.lockheed.com
>Subject: Re: BG RIBBON DEAL - Impressions
>X-Sun-Charset: US-ASCII
>X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN
>I think Doug Purl mentioned that there is always a rolloff, and if you look
>at their litature they mention a 18.5K upper limit to the +/- 3db bandwidth.
>I did not notice the rolloff, but then again, how good is your hearing at 
>those frequencies.... I had poured over the liturature prior to going to
>listen to the ribbons and was concerned about this so I was listening for 
>any possible loss of treble, but really could not detect it. Maybe I should
>ask myself, how good is my hearing these days...... Thats also why I went 
>with a "younger" friend to hear them. His impressions were very similiar to
>mine, now all he wants to do is listen to a few electrostatics just to be
>certain that he is making the right decision, ie. to get the ribbons. 
>Hope this helps, 
>        Kevin Rogan     NPT7   krogan@asic.sc.ti.com    972-480-4480
To be fair, Doug Purl privately e-mailed the following to me:
>Date: Mon, 12 Sep 1994 02:04:24 -0600 (MDT)
>From: Douglas Purl 
>Subject: Re: Genesis II's
>To: Bill Alford 
>I wonder what possesses Genesis to arrange these thus.  I 
>think adding the smaller ribbon tweeters is just marketing hype.  I don't 
>hear tv flyback transformers out in the room anymore, but my son does, 
>and he confirms that the Carver 60" ribbons are flat to the limit of his 
>hearing.  I will test him with the signal generator when I go home.
Doug Purl has also posted the following informative posting:
>Date: Fri, 28 Oct 1994 02:03:24 -0600 (MDT)
>From: Douglas Purl 
>Subject: More Planar Ribbons
>To: Bass Mailing List 
>There is an interesting ad on p. 60 of Speaker Builder (7/94), the latest
>issue.  "Acculine" planar line source transducers.  Represented is a 28" 
>long driver that is manifestly a spinoff from the Carver ribbons.  Nowhere
>is the driver described as a ribbon.  Acculine is described as a division
>of Bohlender-Graebener Corporation.  Dave Graebener is the co-developer of
>the Carver ribbons and of the now defunct "Auricle Series Planar
>Transducers" formerly offered by Speakerlab.  It is instructive to see the
>evolution of pricing for these models.  In 1992, at the point of
>discontinuance, Speakerlab sold two models, the RD50 and RD75.  The
>numerals designate the length of the film diaphragm.  Speakerlab, like
>Acculine, was careful not to describe these drivers as ribbons.  To me,
>and I think to others, a ribbon has always been a conductive metal
>membrane suspended between a magnet structure adjoining the sides of the
>membrane.  As I described in a posting last summer, when I had not
>inspected the Carver "ribbons" carefully and believed they were classic
>ribbons, ribbons are like a sheet suspended from top and bottom in a 
>doorway, the door posts serving as magnets. 
>Even so, the Carver drivers, even if not ribbons in the conventional sense
>of the term, are not inferior.  On the contrary, they seem to me superior
>to conventional ribbons.  The latter are immersed in a magnetic field that
>varies from core to fringe in intensity.  Long excursions can move the
>ribbon into a lower-gauss field.  Consequently, the BL product will alter
>dynamically with amplitude.  The push-pull magnetic field in this Kapton
>film/metallic conductor technology is complementary regardless of
>excursion, since each row of flanking magnets exercises the complement to
>the inverse square of magnetic force in the field. 
>Not inconsiderably, the Kapton film technology promises to be much more 
>robust and durable than conventional metal ribbons, which are many times 
>more susceptible to flex fatigue than Kapton.
Doug Purl has followed up that last paragraph with the following recent posting:
>Date: Tue, 6 May 1997 15:36:41 -0600 (MDT)
>Reply-To: dcp@selway.umt.edu
>Sender: owner-bass@mcfeeley.cc.utexas.edu
>From: Douglas Purl 
>To: bass@mcfeeley.cc.utexas.edu
>Subject: re: making ribbons
>X-Listprocessor-Version: 8.0 -- ListProcessor(tm) by CREN
>Many of the film candidates being suggested right now lack the requisite
>properties.  Not ideally, but minimally:
>1.  Must be thermally stable over broad range of temperatures.  No
>expansion and contraction under normal conditions.
>2.  Non-hygroscopic.  Related to above.  Prevention of sagging.
>3.  Resistant to shearing fatigue.
>BTW, ribbon crinkling is done after the marriage of film medium and foil
>coils.  The rugged film base protects the ribbon from damage during the
>crinkling process.  The film gets crinkled, and the foil conforms.  Raw
>aluminum foil ribbons pose a dilemma: too thick, and they lose sensitivity
>and frequency extension; too thin, and they are vulnerable to the slamming
>of a door, not to speak of the difficulty of working with them.  Mylar is
>inferior to Kapton in the criteria listed here.
>Doug Purl
Doug Purl has mentioned here the frequency extension possible with raw aluminium foil ribbons (which aren't clamped at their sides like the Carvers). I'm now listening to almost this with a set of ribbons retrofitted by Tony Moore (and the Carvers are stored away and up for sale soon). Tony Moore's usual ribbons are described at the url http://www.audiolit.com/ambience This url also points you to a review of "Anthony Moore Ambience Ribbon Hybrid Series" in which the they refer to "our reference planar-magnetics" which are none other than Carvers. I'm not surprised when this review states:
>The Ambience speakers have very high resolution of detail, significantly more than
>our reference planar-magnetics.
I've been observing exactly this and noticing things that I had never noticed before with the Carvers. I've been picking up the precise positioning of various things in the sound stage that I had never before been able to resolve with the Carvers. I can't agree with everything in this review though. I've listened to a set of Tony Moore's speakers and thought the bass was lacking, particularly compared to what I'm now using in this area.

My ribbons consist of four-leaved crimped aluminium foil held together by a high temperature tape and this is all the information that Tony Moore will release about this. My ribbons are also longer than Tony Moore's usual ribbons because they have been retrofitted into a former ribbon and I will be producing www pages on this in the future. The frequency response of my ribbons plus crossover are given in the third included gif file and more can be done about the small drop off in the extreme treble via the crossover. The crossover has a notch filter in it to cancel out a cavity "resonance" which is inherent in this technology. At 280Hz the ribbons cross over to a bass unit that I will be writing about. The ribbons as they are now are letting through all the information in the extreme treble that was lacking from the Carvers and more. This shows up on such things as audience clapping and noise, piano (one of the hardest things to realistically reproduce), harp, triangle, other high frequency percussion, harpsicord, guitar, banjo, sibilance and white noisey things like tape hiss and LP reproduction, particularly individual dust particles that I wasn't noticing with the Carvers and wondering why. One album which is particularly revealing of this is the Opus 3 "Test Record 1 - Depth of image" in either LP (Opus 3 79-00) or CD (Opus 3 CD 7900). This may have come from an analogue source but the material is particularly revealing of problems in the extreme treble amongst other things, particularly the track where large South American Pan pipes are being blown (a white noisey source) and the track of the difficult to record and reproduce soprano recorder.

Doug Purl above refers to the problems of aluminum foil ribbons. Tony Mooore's ribbons do flutter about if you breath on them and they can very visibly move about when reproducing a loud signal (something that I've never seen the Carvers do) but in return they breath back things the Carvers can't do. In the review referred to above of Tony Moore's ribbons it states:

>The crossover frequency is at 420Hz. This is higher than some other planar magnetic
>models, and the result, in our opinion, is that the ribbons will last longer (the
>ribbons tend to stretch out with use over the years, attenuating their accuracy).
Tony Moore has this to say about the long term durability of his ribbons: prove that there is a problem. He has had ribbons put through all sorts of continuous testing and use for the last several years and they are still as good as new. Only time will tell on this and I don't expect a re-ribboning will be too expensive if it is ever needed.

PS The subject line is a pun on the song "Rhythm of Life" (remember those very rhythmic words in the song from about 25 to 30 years ago "Rhythm of life is a powerful beat, puts a tingle in your fingers, a tingle in your feet, rhythm in your bedroom, rhythm in the street, yes the rhythm of life is a powerful beat..."). I've had the exhilerating experience of singing this and other great songs from this period in a massed choir in the Sydney Town Hall beneath huge towering 64ft organ pipes. I'll be writing about reproducing low frequency bass. I could be accused of doing a Steven R Rochlin on this from the sound practices mailing list etc but like he writes, enjoy the music.

Bass units to go with Tony Moore's ribbons

The following was posted to the bass mailing list under the title "Bass units to go with ribbons".

Attached to this posting are three theoretically computed speaker driver gif files. I apologize in advance to anybody who can't view these gif files immediately and suggest that they get the appropriate hardware/software to do this. I've purposely chosen to use gif files for compatibility reasons in world wide web browsers.

I used to have in my listening room a dipolar vertical array of 5 Carver high-Q woofers per side on large open baffles as the bass units for Carver ribbons. In theory these units should be doing great things but I could never get any low bass out of them like the house shaking bass I've had in the past in the same listening room. Between about 35-40Hz and their crossover point to the Carver ribbons of 200Hz I had no complaints about. But below about 35-40Hz the woofers would appear to be moving around as they should but with no audible or felt results unless I stood right beside the woofers themselves. What was going on in this situation is explained in the following Usenet posting:

>Article 72326 of rec.audio.opinion:
>From: "Arnold B. Krueger" 
>Newsgroups: rec.audio.opinion
>Subject: Re: Positioning of dipole subs
>Date: Sun, 2 Mar 97 22:29:48 GMT-10:00
>Organization: PCTA
>Lines: 19
>Message-ID: <01bc26fd$3022ce20$916dadce@crc3.concentric.net>
>References: <3319634E.2C30@netvision.net.il>
>NNTP-Posting-Host: 61006d0013dt.concentric.net
>X-Newsreader: Microsoft Internet News 4.70.1155
>Danny Bekhor  wrote in article
>> I'm experimenting with the placement of my dipole subs.
>Dipole subwoofers are arguably an oxymoron, particularly in the
>configurations shown. You can't get good low bass when the out-of-phase
>back wave is allowed to freely mix with the front wave. 
>The most effecitive applications of these kind of speakers I have seen
>(which were still pathetic compared to a good subwoofer design that
>addressed the issue I just raised) put each sub perpendicular to a side
>wall, essentially touching it, and a few feet away from the back wall. If
>you do this right, the back wave will bounce off the back wall at medium
>low frequencies and be sufficiently delayed to not cancel the front wave.
>Still not a pretty picture.
>Another approach I've seen is to place the subs blocking a door in the
>middle of a wall, and trap the entire back wave in an adjoining room.
Are there suitable monopolar candidates to go with line source dipolar ribbons? On this mailing list the NHT1259 appears to be the favoured candidate but I suggest that there are other candidates, like the Peerless 831857 in a 160 litre box with a port tuned to 18Hz, particularly at infrasonic frequencies. In the included theoretical computed gif files the yellow plot is the NHT1259 and the green plot is the Peerless 831857 in such a box. The first gif file is a comparison of their normalized amplitude response and down to about 11Hz they are essentially the same but thereafter they go off at their expected falloff rates. The second gif file is a comparison of their maximum acoustic power and this really shows up their true potential with the Peerless 831857 clearly much better than the NHT1259 below 40Hz. At 20Hz the Peerless 831857 is about 18dB better than the NHT1259, a fact that makes the Peerless 831857 look a much better candidate than the NHT1259. The hump in the maximum acoustic power of the Peerless 831857 at 18Hz, the frequency the port is tuned to, I'm not too concerned about as it is at a frequency below audibility and in this infrasonic frequency range will be "pleasingly" detected. I've always had a bias against vented boxes because of what they do below the Fs of the driver (24Hz in the case of the Peerless 831857). The third gif file is a comparison of their group delay and down to 30Hz shows that the group delay of two drivers is inaudible and allays any doubts that I have about using a vented box. The only disadvantage of using the Peerless 831857 that I know of is that the box that it is to go into is twice the size of the one suitable for the NHT1259 but when it comes to low bass big boxes are to be expected. I believe that the Peerless 831857 driver is also cheaper than the NHT1259 (or it used to be). In this process I also gain back all the back wall that was hidden behind the Carver woofer towers. And the surrounds on the Peerless 831857s are rubber, not potentially rotting foam on the Carver woofers in a sun filled solar house.

On paper then the Peerless 831857 in a 160 litre box with a port tuned to 18Hz looks a much better candidate than the NHT1259, particularly at infrasonic frequencies, to go with dipolar ribbons. I now have in my listening room a pair of Peerless 831857 drivers in very well braced 160 litre boxes with a port tuned to 18Hz flanking the retrofitted Tony Moore' ribbons that I described recently on this mailing list. The crossover frequency between the two units is 280Hz. Other crossover frequencies have been tried and this crossover frequency was chosen as a good compromise between the resulting sound and the possibility of loading the ribbons too much.

I now have clean bass which can again shake the house that I really can't complain about excepting that the tonal balance changes between sitting in my usual listening position and standing up from there. To solve this problem I suspect that another set of Peerless 831857s is needed sitting on top of the current pair to make the bass units be more line source like, like the ribbons. I hope to find time in the future to do this at the possible cost of another amplifier because I would like to do things differently in the crossover for this extra set of drivers to bring them in at a shallower rate to get them really only working at low bass frequencies. The whole house could really shake then! The tonal balance never changed when changing head height with the Carver ribbons/woofer towers. Unfortunately I can't put the bass boxes in the corners of the room to exploit the room gain that this room positioning gives. I have yet to put the Peerless 831857 drivers into any danger area in my attempts so far to exploit their low bass potential. I can't really fault the combination of the ribbons with the Peerless 831857 boxes excepting in the area of changing tonal balance when changing vertical head height and the limitations of stereo. I haven't had the opportunity to do a comparison with NHT1259s in this system to verify in reality what the theoretical calculations are saying, but I don't have any real doubts about them.

I have heard the very clean building shaking bipolar servo-controlled bass towers that are used in the recent Genesis 200 speakers which use Carver ribbons for the midrange but this is not a very affordable alternative to what I now have.

More on Tony Moore's ribbons

A followup posting was made to the bass mailing list on 10 Jul 1997 under the title "Re: Who makes true ribbons?":

At 04:07 PM 08/07/97 -0700, John Whittaker (jwhittak@csulb.edu) wrote on the bass mailing list:

>One of the most interesting aspects of the review of the Tony Moore
>'true ribbon' speaker is the complete failure of the reviewer to comment
>on the speaker's load impedance.  A true ribbon speaker can be expected
>to have a very low impedance.
>Even thought the reviewer states "The Anthony Moore is a true ribbon
>speaker.", he states at the end of the review "In summary, the Ambience
>hybrid planar-magnetic speakers are superb."  Which is it ribbon or
>I think we would all agree that any discussion of a true ribbon driver,
>i.e. one with a metal conductor suspended at top and bottom and free on
>the sides, MUST contain information about the impedance.  Do we not
>still discuss the original Apogee ribbon driver with it's approximate 1
>ohm impedance, and how it 'cooked' amplifiers of it's era?
The review that John Whittaker is refering to here had some good and bad points about it. This review did slip up at the end by using the term planar-magnetic for Tony Moore's true ribbon speakers. In the review its "reference speakers" (ie Carvers) were planar-magnetics. I do quibble with the definition of terms in this review. I wrote the following in my posting to the bass mailing list on 17 May 1997 under the title "The ribbons of life (long)":
>My ribbons consist of four-leaved crimped aluminium foil held together by a
>high temperature tape and this is all the information that Tony Moore will
>release about this. My ribbons are also longer than Tony Moore's usual
>ribbons because they have been retrofitted into a former ribbon and I will
>be producing www pages on this in the future.
The url for the beginning of these www pages is at the end of this posting. Let me further expand out what "four-leaved crimped aluminium foil held together by a high temperature tape" means. Four separate strands of crimped aluminium foil about 5mm wide have been joined together with a high temperature tape continuously along their length and then soldered at each end beyond where it is clamped to return wires to give a total resistive (only) impedance of 2.9ohms in my one-off case. Soldering the return wires to the separate strands of aluminium foil is more reliable than what Carver does. In your typical Tony Moore ribbon five separate strands of aluminium foil are used which gives a total resistive (only) impedance of just under 4ohms, a load most amplifiers have no troubles with. This is the reason why there was no comment about this in the review referred to above as there really was nothing to comment about and I'm sure they would have commented about this if there was any shortcomings in this area. In another review in Australian Which? Loudspeaker for 1997 they were running Tony Moore's ribbon hybrids with a "weedy Audiolink Sterling, a 50-watter from the UK" with no problems and refer to a 25 watt Leak valve amp having no problems in driving them also. I run my version of Tony Moore's ribbons with a Metaxas Audio Systems Solitaire power amplifier rated at 120wrms into 8 ohms and it runs a bit warmer than with the Carvers but it is not displaying any signs of problems. Carver (and BG etc?) use a similar method to make the resistance of their planar-magnetics similar to Tony Moore's ribbons. BTW, for comparison purposes, conventional speaker drivers can have resistances at parts of their frequency range fall to 2ohms. Also, the Raven true ribbon tweeter uses a transformer to overcome their intrinsic low impedance. The Raven true ribbon tweeter amply demonstrates the extreme treble extension that a true ribbon is capable of. Using the Raven true ribbon tweeter to overcome the deficiencies of planar-magnetics in the extreme treble will probably have dispersion problems in the vertical plane at least and will probably need an expensive solution like what Genesis has done. As I wrote in my posting to the bass mailing list on 4 July 1997 under the title "Re: Carver ribbon speaker design and other thoughts":
>... The
>far better solution of this problem is to use a ribbon material which
>doesn't have this problem. The difference having the extreme treble done
>properly makes is not subtle.
John Whittaker continued:
>Given the disappearance of the Moore speaker from the marketplace one
>must question it's reality as a viable design.  True ribbons are fragile
John Whittaker should check his facts before making statements like these. Tony Moore's ribbons have definitely not disappeared from the Australian marketplace at least. Checking with Tony Moore, he is not the only person to have had problems with Music Labs USA and Tony Moore is in the process of finding another USA distributor. Tony Moore currently is exporting to the UK and New Zealand. Tony Moore's ribbons are far from "fragile" inspite of them fluttering about if you breath on them. Inspite of what Tony Moore conservatively states, I would expect his ribbons to have similar power handling abilities to the Carvers without their problem in the extreme treble. My version of Tony Moore's ribbons have been run with 1.6kW peaks (yes one thousand six hundred watts peaks!) and run at continuous powers of several hundred watts with no problems. But don't run DC through them (such as when an amplifier badly clips or something is faulty) as like other drivers they will then fry and thermally destroy themselves. And I have checked up about reribboning Tony Moore's ribbons if this is ever needed (like physical damage from cat's claws and other things) and this is inexpensive, unlike the Carvers.
>John Whittaker
>Long Beach, CA, USA
>googong@interact.net.au wrote:
>> According to a review of Tony Moore's speakers which have a wonderful true
>> ribbon in them at the URL http://www.sdinfo.com/volume_3_2/v3n2g.html, the
>> USA distributor of them is Music Labs USA, Inc., P.O. Box 148, Denver, New
>> York 12421; Phone 607-326-7689; Fax 607-326-3436; E-Mail
>> Bill Alford     googong@interact.net.au

Bill Alford	googong@interact.net.au  http://users.interact.net.au/~pwaa
I am in no way affiliated with Tony Moore or his company. I own a pair of his ribbons and I am VERY satisfied with them.

View photographs of Tony Moore's ribbons and bass units

Bill Cowan's home page

Construction details, etc for the Peerless 831857 driver in a 160 litre box

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For more information, suggestions, comments, contact Bill Alford
Last modified 29 October 2001.