Visitor sent me a link to the 6moons announcement of Living Voice new loudspeaker

http://www.6moons.com/industryfeatures/industryfeatures.html

“Coming in August 2009: Living Voice horn. The Vox Olympian is Living Voice's new time-aligned statement hornspeaker sculpture and the company's Lynn will give us the straight poop on what to expect. Asked how many audiophiles it will take to move one of these, she punned "at least three large ones"... We'll assume she meant folks and not pints.”

To say honest I read the Sarah’s note 5 times but I did not understood what he meant to say. Anyhow, I found the Living Voice new loudspeaker has some interesting design point that would be worst to point out.

(image is courtesy to 6moons)

The “time-aligned statement” – that is good, if it is true. The bass channel looks like use a variation of Karlson box, which is different type of port, what is fine as well.  They did the same in their former model and it looks like they like it. If it is not a play around Karlson and in fact a play around a horn then how it might be time-aligned?

 



(the lower image is courtesy to Living Voice)

Anyhow, as you understand the element that made me horny in this loudspeaker is the cupper or bronze cannon that they have in front to it. This is where I would like to sharp my attention. The audio people for years straggle with the WAF (Wife Acceptance Factor) and here is where the Living Voice made a major breakthrough – most of women will like how this speaker looks like. To be more serious I think what Living Voice did with tweeter is very questionable.

I understand the Living Voice intention to have a compact speaker and do not let the tweeters in it’s time-aligned position do not pollute with HF reflections the top of the MF horn. So, Living Voice used the old WE technique of horns for tweeter:  a long full size exponential horn. The WE curve ended to be perpendicular to axis, which was very important for HF but Living Voice do not care even about that. However, regardless the horn is used THAT TYPE of solution is in my view is absolutely NOT useable for HF. I have no idea what kind driver they use and how it being loaded but in such a deep horn sound will have very aggressive low pass effect. The HF will be attenuated and transients will be very muddy. In addition this type of horn will beam like hell – the Living Voice has a nice wide spreading MF and ultra narrow HF - why is it necessary? The Living Voice added apt another channel the looks to me like inverted cone. I do not know what it does – it might be what they call a super-tweeter or it might be another MF channel, I do not know. I do know that the channel with this pipe sticking in front of it shall not be there as what’ve is doe it will underperform.

There is a remote possibility that Living Voice picked my idea of Injection channel, found an interesting driver and tries to do something along those lines. I do not think so as the bandwidth of injection in this horn will be VERY narrow.  In my past I experimented with idea that I call a “distributed diffuser”.  The idea was to keep very aggressive tweeter in time- aligned position “behind” the MF but to make the tweeter fit to a surface near the MF mouth the will be a large diffuser. In this case, I though, the diffuser will be good wide diagram transducers but it still source the timing reference from a  time- aligned tweeter diaphragms. I was not successful with it and found that it messed up HF too much. If the Living Voice had a diffuser in the end of the pipe then I might think that they did something similar.

However it looks like they use a pipe instead of a HF horn. I wish them good luck with this approach.

What I found captivating in the story of the Living Voice speaker is the he motivation of the Living Voice people to go from their former model to this new one.  This itself. is a very interesting to me subject.

If you look at the image of the former commercial version of the Living Voice then you can see a tweeter that is more or less anechoic positioned.  The speaker reportedly use Vitavox S2 driver for MF and they looks like complimented it with a tweeter in time-aliened position. I think it looked very good and it was a sensible solution for that speaker. However, it looks like Living Voice was not pleased with S2 + tweeter configuration and they build up some complicated addition to S2.

This begs a question: what in S2+ right tweeter was not good enough that made Living Voice to go for something that looks like 2 tweeters and one of them in “retarded” tweeter. If Living Voice knows what they do then I see two possible explanations:

1)   Living Voice still has no good tweeter and they keep experimenting. In think case what they do now, I am sure is juts intimidate phase that will be replaced within a proper tweeter later on when Living Voice found it.

2)   Living Voice found a very specific configuration where this “retard tweeter” somehow talks acoustically with output of the S2 driver and make some differences in its very upper knew. In thin case it might be interesting to see what Living Voice was trying to accomplish and what they accomplished.

On a hunch, I would propose that the option #2 is less likely as it would be too advanced for a commercial loudspeaker. It is not that commercial loudspeaker might not be build with those aims but how many people out there would appreciate all of those satellites? 

Sure, there is an option #3 – they created some kind of crap just in order to let the Morons from 6moons to make distinctively deferent pictures. This would be like some manufacturers put sexy glowing tubes on chasses that are necessary or even not connected to the circuit. However, it makes the amps more photogenic and allow the cretins-revelers to write long articles how the change those decorative tubes with only filaments connected to some kind of Amperex “Bugle Boy” SE/LP/UQ/HS (Special Edition, Limited Production, Unusual Quality, Higher Specification) would dramatically improve the presents of Patricia Barber on the listener laps.

There is also a ridicules option #4 – the Living Voice might use a digital filtration with room correction option driven by a microphone.  In such case the cannon sticking in front of the speaker is not a transducer but a “listener sniffer” that reads the reflections from a listener. I know it is absurd but mo more absurd from my point of view then put a tweeter inside a pipe…

So, what knows what they do but I would be curios to learn what motivated them to do it, particularly if they use my Vitavox S2 driver.

Not this year they won't be, that show is in September.

Romy, Kevin at Living Voice has been using 'your' S2 since 1992. I understand these speakers have the first of the new Mike Harvey S2's fitted.

I'm not sure what the thinking is behind the configuration he's arrived at but I do know that he's made his decisions based entirely on what works for him. I don't think he's particularly trying to please anyone else.

guy sergeant wrote:

Not this year they won't be, that show is in September. Romy, Kevin at Living Voice has been using 'your' S2 since 1992. I understand these speakers have the first of the new Mike Harvey S2's fitted. I'm not sure what the thinking is behind the configuration he's arrived at but I do know that he's made his decisions based entirely on what works for him. I don't think he's particularly trying to please anyone else.

guy sergeant wrote:

An earlier iteration I heard with this two tweeter arrangement sounded seamless & enjoyable.

guy sergeant wrote:

I will ask.  As anyone could by sending an him an email or calling him.  Ultimately though it'll be because that's what he felt worked best.

Well, it is a bit more complex then what you wrapped up in your last two sentences. Manufacturers rarely, if ever, can open and without complexes to discuss cons and pros of their design decisions and own sonic actions, partially with such a “free thinkers” as I am. I perfectly understand it. For manufacturers Sound, or to say more accurately the “public perception of sound”, is a service that is responsible for mortgage payments, kids’ colleges, parent’s hospitals, wife’s new dress and the dally food on their tables. So, I do not feel that any critical or meaningful conversation with manufacturers might be useful or even comfortable to be engaged with. I much more prefer to have a “disengaged status”, which also to be more predisposed for honesty, sincerity and objectivism. 

Based upon my familiarity with S2 driver I do not see I there two tweeters.  Even the Living Voice uses a larger and slower opening horn then I use and therefore the Living Voice’s upper knee of S2 shall be more attenuated then mine, I still do not see in there 2 tweeter.  The second tweeter I think comes from the fact that one of the tweeters very ineffective. What Living Voice created is most likely is an illustration to Carlo Collodi’s adventures where the Pinocchio’s nose grows proportionally to the “deviation from truth”.  I think the Living Voice went for second tweeter because they did not found a “right” single tweeter. I do not I insist that I know what the Kevin’s definition of “right” single tweeter is but it looks like that he did not found it yet.

That all might sound for “simple people” as some kind “criticism” of Living Voice new speaker but in reality it is not. I take it more as an advancement of knowledge about the ways of use the S2 driver. Anyhow, when you will be listening the new Living Voice try to disconnect both of tweeters and listen it the speaker with no tweeter - this is very imperative. You do not need to disconnect but you might just cover them up with some kind of blanket.  Then you can uncover one by one tweeter and listen what sonic effect it will do, including off the axis.  It is possible that tweeters are made to work together but you shall be able to figure out a message if the message exists. Yes, this is important, when you will be experimenting with it and if Living Voice will employ an additional external LF section (as it should) then disconcert this external LF section.

I kind of feel not comfortable to be overlay demanding about Living Voice speaker. The guy uses my Vitavox S2 driver – I shall celebrate it, not to be critical. In addition I feel that Living Voice have already invested into marketing of their new speaker.  Since they made the Srajan’s 6moons then everyone known’s what it means. The Srajan Ebaen was invited for a free ride in UK; his travels, hotels, food, entertainment, “gifts” were paid by Living Voice, the Srajan’s dick was Ffguratively sucked in order to make him to drop a few positive BS adjectives about the new speaker.  This is the new form of jouwhorernalism that the audio sleazeballs are invented and where those poor manufactures are just hostages in the industry con. There is no room in this con for Sound, not to mention that the participants of the Srajan’s level are depraved in their sensibility to the “fruitful sound”.  So, I did not expect that any clarity will come from upcoming 6moons write up but the fact that Living Voice’s Kevin  invested into the 6moons’ advertising indicate that Kevin considers his design as complete.

cv wrote:

It looks to me from that he might be using an S2 from around 500Hz or 600Hz up

Well, I thought about this configuration and it would be hardly possible in the light of what Kevin does. Let pretend that MF is low-passed at 6K and then it has a tweeter all the way up. Lately it have been became a fashionable to add a ultra tweeter that covers over 20K and go all the what to 100K or 5MHz as someone claim. Some people use them and report “improvement”. I call those channels the microwave resonators and there is panty of researches describing what those channels do – they resonate and shake brain cells and increase the brain cells temperature. That would be a legitimate explanation of the presence of 2 tweeters. Unfortunately it would not fly in the Living Voice’s case. The microwave tweeters work well only with the systems that very extended to the bottom – the new Living Voice does not look it is deep LF-able. Also, which tweeter among those that Living Voice uses might be the microwave tweeters?  If it is the Pinocchio tweeters then it wrong as in this type of horn acts as a very strong low-pass filter. If it is the upper tweeters then it is wrong as well become the Pinocchio will not be able to care 6K crossover point, not to mention that whatever it will be able to care will be with a laser-narrow detraction around the axis.  Most likely I think Kevin’s upper tweeter acts as a normal wide-dissipation tweeter and the Pinocchio tweeter just adds some very slight touch of color into the sound a sort of the pink socks in the Albert Goldman “straight” dress from The Birdcage film. Oh, god! Did I just discover a hidden gem a new industry vocabulary – the Gay Tweeter !?

Alternatively Living Voice might use a new becoming fashionable crossover topology that calls ICC. It stands from Internal Combustion Crossover and in there the filtration happen by passing signal across specific chemicals. It is known that ICC has by-products gas that needs to be dispersed and in this case the Pinocchio tweeter is not a tweeter at all but a sexy-looking muffler.

cv wrote:

PS I really can't imagine Definitive Audio supplying Srajan with umpteen hookers and a bowl full of coke *and* throwing in a tarted up hummer to host the whole shebang. I don't think the "jourwhorenalism" approach is new - vis KK with Transparent/Wilson/Absolute etc ... or indeed any other industry involving PR and the press...

No, the Definitive Audio is not in Srajan’s alley.  The Srajanodactyl  type specializes on small play, where the pray is defenseless and weak. Then Srajan can sell to manufactures his Messianic contribution at full bloom and dement better coke and hookers with longer legs. People who read my site regularly are accustom for my hyperbolic metaphors but from the reports I got from different manufactures the hyperbolism of my position is only appears to be a hyperbolism.   Ironically I do not blame manufacturers for playing those games. I do not even blame for propelling those games. It is in a way win-win situation for both of them, way not. The problem is that the lever at which the game is played fucks up Truth and does not serve interest of better sound. The Srajan "jourwhorenalism" is not about quality of listening and not about magnitude of sonic accomplishments but about quantity of extortion.  Srajan is like a Bee-Moron who as soon a flower blooms descent to the flower, collect the nectar, and instead or passing it to a fertile recipient he dumps it to a toilet and flashes the water…

The 6moon has posted an article about the Living Voice:

http://www.6moons.com/industryfeatures/livingvoice2/olympian.html

http://www.6moons.com/industryfeatures/livingvoice2/olympian_2.html

http://www.6moons.com/industryfeatures/livingvoice2/olympian_3.html

I did not read it; I will what I have time and will comment upon it. In fact I am very much looking forward to see what Kevin was trying to do in there.

Romy the Cat wrote:

The 6moon has posted an article about the Living Voice: http://www.6moons.com/industryfeatures/livingvoice2/olympian.html http://www.6moons.com/industryfeatures/livingvoice2/olympian_2.html http://www.6moons.com/industryfeatures/livingvoice2/olympian_3.html I did not read it; I will what I have time and will comment upon it. In fact I am very much looking forward to see what Kevin was trying to do in there.

It is good that Srajan used so many quotes by Kevin Scott as I would prefer to hear more form him them from the 6moon’s clown. Interesting that the language difference between the Kevin’s subject and the Srajan is very definite - Kevin talks more or less about tangible specifics vs. Srajan talk about generic BS. I said that Kevin talks “more or less“ about specifics as he was also not very clear and intentionally-fogy. Let me to address the specifics that I found worthy and then to pass some general observation.

The trip in the memory lane to some Vitavox History and the Living Voice former moder was OK . I do not feel that it was interesting or accurate but I guess it is a part of the Srajan’s “coming out” .

Srajan wrote:

The Vox Olympian bass driver is the massively constructed Vitavox AK151. Designed specifically for horn loading, it uses a powerful AlNiCo magnet assembly, a light straight-sided paper diaphragm and an 8-ohm coil wound on a 57mm diameter former. It employs a custom suspension developed specifically for the Olympian. This unit is loaded by a modified exponential compound horn that is hand-fabricated from custom laminated and precision calibrated 30mm solid beech.

Let leave all cap about the “hand-fabricated” and “custom laminated” aside and to look at what is important. The use of the Vitavox AK151 driver is very good.  They went for 8-ohm coil. Well, this is interesting. Srajan promoted in his article Kevin and SET devote and then Kevin drops the AK151 impedance from 16 to 8 ohm. The only explanation that that I have would be that Kevin was trying to gain some dB-output from AK151 but he might loops in damping. With SET that use feedback it might be not a big deal but in “straight SETs” I would prefer to stay with high impedance bass drivers. Well, in my DSET world it is not a subject but I guess driving the Olympian from one amp Kevin needed to mitigate the output of the channels. The “custom suspension” that Srajan mentioned is sound “strange”. Again, those idiots always use word “custom” as sight id exclusivity but I said many times before and I say again - if you refer to well known design and insist that you use a custom solution then you need to highlight ether what you did, or what you intent to do or what you did not like in the default design/result. Otherwise what you say is just a pile of crap. I have seen MANY manufactures that made many claims about the “custom” modifications of drivers and in very many cased it was just a BS.  Since the comment about the “custom suspension developed specifically for the Olympian” come not from Kevin but from Srajan I would discard it as Srajan’s typical mouth running.  What however, is more important than anything is to learn if the Living Voice uses the vintage AK151 of the new production. If it is a new production then it is very much NOT NECESSARY that the AK151 share any sonic characteristics of the AK151 from 50s as they use very different vintage of papers and different of the cones.

Srajan wrote:

The midrange driver is the famous Vitavox S2 AlNiCo compression driver. It uses a three-inch diaphragm and a custom suspension made specifically for the Vox Olympian.

Again, there were a lot of conversations in the UK forum about the Kevin Scott customized or not customized the S2 driver. This all juts mouth running. Kevin said nothing about Kevin customization. Srajan runs his mouth about the “custom suspension made”. Kevin is in cooperation with Mike with Octave Audio who does for year his white suspended S2’s cones. Would it be recognized as “custom suspension”?  I do not think so. Kevin very diplomatically keeps his mouth shut about the “custom suspension” and about the “specifics” of the upper knee of S2 driver. Did you wonder why? Because everything was said about it and there is absolutely nothing to talk. He let the Srajan to run his lips, I was surprised that Srajan did not tell the story that S2’s magnet was charged with radioactive isotopes and the S2’s cone was “charged” made by the Tibet monks….

Srajan wrote:

Continuing upwards on the driver array, the remaining two horn-loaded units are of Japanese providence, TAD to be precise. Their 1-inch throat model TAD2002 combines a Beryllium dome with an Alnico 3 motor. This driver has a useable bandwidth of 1kHz to 27kHz, an extraordinary specification. Living Voice however uses this unit only for HF duties by loading it with a modified exponential horn fabricated from seven pieces of cast LG2 bronze. The final unit at the top is a modified TAD Exclusive ET703, a slot dispersive compression driver again with a Beryllium diaphragm. This unit has a useable frequency range of 5kHz to 45kHz but Living Voice only runs it above 15kHz as a super HF driver.

OK, it is the TAD2002, loaded into this long bronze pipe, probably at 10kHz -12kHz and ET703 at 15kHz.  I like how Kevin angled the slot of the ET703 driver – I hope he made the ET703 and the slot rotatable - I would.

Kevin wrote:

All I was interested in was achieving the best possible result in musical terms. I am interested in music and in particular capturing human expression in musical performances. All design decisions were subject to this principal consideration. For example, we know that a drive unit’s behavior in its stop band (where it is progressively rolling off) is just as important as its behavior in its pass band. It is therefore preferable to operate the drive units comfortably within the most linear part of their bandwidth. I experimented with a lot of HF drivers and found that those which worked to my liking at 5kHz were attenuated or untidy by 20kHz. On the other hand the HF drivers that I was happy with at 20 or 30kHz sounded weak and fragile at frequencies below 10kHz even with third order filters. A two drive-unit HF solution was the best way to resolve this problem and achieve the results I found musically satisfying. We therefore operate the very high frequency unit or super tweeter only in its uppermost bandwidth, thus allowing it to behave tidily below its pass band. Similarly the main HF unit is used well above its low-frequency limit. This driver is loaded with a long bronze horn which has two functions. On the one hand it provides a strong and assured coupling of the driver to the room, something I find musically important.  On the other hand it provides a low-pass acoustic filter which helps us achieve a seamless integration with the super tweeter above it. This is an elegant solution that I find musically insightful, persuasive and engaging. I've worked on this project for 6 years and tried a great many reasonable and unreasonable permutations and this HF arrangement was very much to my liking. In the empirical development process, you discover odd little things that have great significance, are impossible to quantify but need to be understood and replicated. Similarly things of great theoretical importance can be quite benign.

This quote is important and I read it a few times. You see, in this quote Kevin is trying to defend his decision of use the double-tweeter in the way HOW he did it. Interesting that I do not question he double-tweeter as a concept but I only question the shape of the lower tweeter horn.  I understand that Kevin found the sonic character of the LG2 bronze very valuable and that he is trying to use it almost as I use my Injection Channel. I love the radial texture that he did inside of his bronze pipe (Thanks to Srajan for high-res pictures). However, the 120 degree horn with S2 works right along with extremely narrow –shooting bronze pipe. It dies does not make sense.  I do not say that it is “wrong” I just do not see WAY it would be necessary. What would be different if the TAD2002 be sitting not bend the bronze pipe but behind a convectional bronze horn? Kevin did not want to use low-pass filter on TAD2002 driver and deans to roll it with VERY deep horn? Well, let see the penalty we pay for it in term of unnecessary shrinking of dispersion…

Kevin wrote:

For example I did not find that time-aligning the bass and midrange drivers was musically that significant. What I did find critical however was the time alignment of the midrange, HF and super HF drivers. These drivers are adjustable for output level via attenuators on the back of the cabinet. This allows for adjustments to be made to the tonal balance to suit different room types and sizes as well as partnering electronics. The super HF unit and HF units are therefore independently mobile relative to the midrange to allow in-situ fine tuning of the phase alignment. The super tweeter is mounted on a mobile carriage with a calibrated helical worm drive. Similarly the HF driver and horn is also independently mobile against a calibrated inlaid bronze index.

It is not all so accurate.  The precession of time-aligning between bass and midrange drivers has less significance then in HF channels but the fact of time-alignment is not different – it is just necessary to know WHAT to listen when you make your claims about the “musical insignificance”. If Kevin went to some extends to make the HF time-aligned and if he feels that it is important at HF then why he feels that it is not important in lower frequency? The length of the wave is longer the need for the alignment precision is lower but the concept is very much there. Ah, it does not comply with the Vox Olympian design? Probably THAT makes it “musically not that significant” ….

Kevin wrote:

Also of great significance was the choice of materials throughout. A prior bespoke project involved casting a loudspeaker carcass out of LG2 bronze. This material had some very helpful and unexpected characteristics that I came to greatly admire. We therefore decided to prototype the HF horn of the Olympian in LG2 bronze. Simply replacing our preferred and highly evolved cast aluminum geometry with cast LG2 bronze was a delight and wonderful improvement. It revealed a lithe, supple and succulent quality to the tonality, a radiant and naturally heterogeneous quality that made the aluminum sound pale, pastel and dry in contrast. We finally built the Olympian's modified exponential HF horn geometry from seven threaded sections of LG2 bronze*. The sections screw together on fine threads and are separated by a combination of paper and Sylomer** gaskets, which damp resonances in the bronze

Possibly. I do not know anything about the LG2 bronze. The question that would ask – if the “significance was the choice of materials throughout” is suck a subject and if the LG2 bronze is such a wonderful then why Kevin did not make an attempt to made the S2 MF horn from  the LG2 bronze?

Anyhow, let go not to the general observations. With whatever it is the Living Voice Vox Olympian is juts MF speaker and it would be nice if Srajan or Kevin talk more about the supplementary LF sections. It would be very interesting to know if they do the new production of AK151. It might be interesting to hear the Vox Olympian. I still do not feel comfortable with Olympian lower tweeter. The time-missalignment of the upperbass I do not consider as a “problem”. Many speakers do the same and they sound OK. Can they sound better if the upperbass was aligned? Unquestionably!

However, looking at the first appearance of the Vox Olympian I would say that I do not like what 6moons did for Living Voice. I know that Srajan and Srajan read this site and I think they were a bit misguided with my initial speculations and skepticism. As the result, the format of the 6moon’s auricle was in a away a response to my sentiments of the sentiments of the people like me. I think it was a mistake on Srajan/Kevin’s part. The 6moons article is the Living Voice’s investment. I do not talk about the fact that the Living Voice ad “suddenly” show up at the 6moons’s site. I am talking that for the Living Voice and 6moons is was an opportunity to deliver a message to the prospective customers and the massage in my view was dreadfully weak.  How many people out there truly understand of care about the specifics of design? How many of them would consider buying the Vox Olympian?

My interest to the Vox Olympian is very atypical for the people out there. I have my interest because I am familiar with S2/ AK151 drivers and I am curious to see what others would be able to do with them. The normal people out there do not have those interests and I have no idea what interest they would have to read the 6moons article. Frankly, if not my interest in general horns subjects and in the Vitavox specifically then I would probably not read the Living Voice/6moons article. How many people out there like me? A handful?

The point that I am trying to make is that Living Voice shall use this marketing actions (and the print by 6moons is one of them) not targeting the freaks like me but appealing to the interests of wider public. Kevin Scott has some tendency to talk about “capturing human expression in musical performances” and the “musically satisfying results”, so instead of singing the songs about the importance or non-importance of time alignment and the diameters of the driver’s voice coils Kevin had to stress his semi-spiritual objectives in audio and his feeling that he have accomplish it with Vox Olympian. I think THAT would give to readers a feeling that the Vox Olympian might be “special”. Most of the 6moons readers are idiots and they will not consume valid information. Kevin Scott knows is,  Srajan Ebaen know is, the idiots- readers know it about themselves – anyone know that nothing sensible  might be posted at  6moons. The only option is to post the “sensual”.

 Pay attention what speaker advertisers do nowadays. Take a look the Wilsons. They do not sell the “secretive material”,  the  “modified drivers” and the “proton crossovers” anymore  – they sell the “promise of experience”. David Wilson is crying in those ads telling stories that listening his speakers his customers made the decision to run marathons,   switch political affiliation or undergo the sex change operations. The same level of “expected BS” Living Voice shall be deploying to their perspective customers during own initial introduction by 6moons. If I was Kevin I would ask refund from 6moons but it is not a completely the Srajan’s fault. Srajan is in away a stupid Lawn Mower – it will go wherever it will be pointed. I think Kevin Scott did not set the right boundaries for Srajan and as a result the information that was passed to public was not as potent as it might be.

jessie.dazzle wrote:

Romy wrote: "...The use of the Vitavox AK151 driver is very good.  They went for 8-ohm coil. Well, this is interesting. Srajan promoted in his article Kevin and SET devote and then Kevin drops the AK151 impedance from 16 to 8 ohm..." I think it does not matter what was the originally intended. According to the Vitavox spec sheet, the AK151 always did have an "8" Ohm coil (nominal rating as indicated on driver housing is 7 Ohms). Its the K15/40 that has the "16" Ohm coil (nominal rating as indicated on driver housing is 15 Ohms). The K15/40 is the version that was originally intended for use as a direct radiator.

Interesting, as all my drivers, the AK151 and K15/40 are high impedance (15R-16R, DCR around 12R). I do not see a lot of difference between AK151 and K15/40 that and they “meant” to use one as direct radiator and another as horn is not really important. They have the very same resonance frequency and the same cone mass. That is all that I feel is important. If they have some minor differences in T/S characteristics then it is not relevant as a horn overrides the T/S anyhow.

I think that 8Ohm coil for Vitavox voice coil was a Vitavox fantasy based upon the facts they needed to integrated it in System 191 and they did not what to burn too much power on MF voltage divider. I would still stay with high impedance bass driver if we are in SET world at least would have the MF as LF driver to be of the same impedance if you used just one SET. If so, then you can set symmetrical clipping of your SET across the full range. If not then pretend the situation at in bass you have your output tube is starving from voltage but in HF your output tube is starving from current. Well, in the real world the only bass clipping would count….

Still, if they used the vintage drivers then let them to stay with whatever they found but if they use new production then I would make them all 16R. With no feedback SETs it would be only better…