The KS12027 horn perched on top of my repurposed Altec 861 cabinet loaded with an Altec 414A woofer should actually be residing inside a ~ 4 cubic foot slanted cabinet with a Western Electric WE713C compression driver bolted to its throat + a WE728B 12" woofer = Western Electric WE757A monitor speaker system.
I was honored to host this KS12027 horn and provide more modest accommodations for a couple of weeks courtesy of my audio preservationist buddy John Piro.
I was honored to host this KS12027 horn and provide more modest accommodations for a couple of weeks courtesy of my audio preservationist buddy John Piro.
He rescued this KS12027 horn with a damaged 0.7" aperture and repaired/modified it so that mere mortals like myself can sample its delights using a more pedestrian 1" exit Altec 802 compression driver.
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| Mono Hi-Fi set up: Neat P58H + Calrad SV16 + GE RPX or DL102, JEL SE2A3 mono integrated amp with Hashimoto H-203S OPT. |
All of my listening was done with the above set up.
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| Altec 414A + mod'ed KS12027 + 802 + GPA34852 |
From the moment I mounted the KS12027 + Altec 802 combo above the Altec 414A woofer, the first adjective that came to my mind and stuck for the rest of its stay was, natural! Just like its WE/Altec 32 and KS12024 relatives, this is also a horn that doesn't sound like a stereotypical horn. In fact, the articulation (attack and decay of notes) and overall presentation of harmonic overtones via the KS12027 is even more natural and realistic. It made the Altec 32A/32C and Azzolina KS12024 sound merely like very high quality Hi-Fi which mainstream audiophiles may find more appealing. These findings were echoed by my friend Ding during his recent visit to the man cave.
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| Altec 32C, KS12027, Azzolina KS12024 |
Even if I loved the KS12027 so much, I didn't want to get attached to something I may never be able to own. So this past weekend I met up with John at a ham fest and handed back this valuable piece of audio history. After giving him my rave report, which is hardly representative of what most audiophiles like nowadays, he was not dissuaded. He is still seriously considering reproducing them. 😎
Thanks for sharing this write-up!
ReplyDeleteTo my mind, the question is begged: If this horn (and some of its antique kin) sounded so good and so "un-hornlike", why did "we" lose the recipe for them oh-so-long ago? ;) Is it like papyrus, or the Saturn V's mighty mainstage F-1 rocket engines, or was it just a Devil's bargain that asked horns to do something else (play loud and clear, with good/controlled dispersion no matter what was asked of them in a large venue), and some of their magic was simply lost in the scuffle?
Just musing, of course!
thanks again,
mrh
(and, yes, I'll admit to a certain amount of jealousy -- I actually probably didn't really need to add this, upon reflection!)
Hello mrh!
DeleteA few reasons off the top of my head:
1. Perhaps the KS12027 was very expensive to produce due to the complicated design - slim 4-cell horn with an abrupt 90 degree bend
2. Many moons ago I had a chance to examine the WE713A (8 ohm version of the 713C from the WE757A) compression driver from a WE753C and it made the 802 driver look like a toy, even to my then, novice eyes
3. The WE 32A horn was a simpler design and a lot cheaper to produce, which is why Altec kept it in their catalog where it morphed from the metal 32A all the way to the plastic 32B and C in the 70s
4. Changing tastes - the WE/KS 12027, 12024, 32A, 754A, 728B, 756A, 755A , L8/L9 theater systems, 753A/C and 757A monitors, etc. belong to the big band/bebop jazz era as well as the lush Hollywood soundtracks which required symphony orchestras...rock and roll was to come later around the time Altec ditched the complicated and expensive multi-cell 808 horn and switched to 811/511 horns which had greater projection at the expense of finesse
In short, it was all about money and fashion trends. :)
Always nice to hear from you!
JE
Hello Joseph! I really really really hope someone can reproduce these. I was just thinking about that as I looked up to see if these had been reproduced and I couldn't find anything. I hope someone can make that happen.
ReplyDeleteHi Jonas,
DeleteLet's see what my buddy JP comes up with.
Since I uploaded the article, I've been surmising the experience listening to J-Rob's WE728B in full range mode last year. Was the KS12027 held back by my Altec 414A? Is its fullest potential only realized when partnered with a WE728B as Western Electric originally intended?
Suffice it to say that I'm still enjoying my Altec 753As as I type. ;)
JE
Well in that case, you'd also have to wonder how the KS12027 horns would sound with the 713C compression driver! Those seem quite rare as well. I'd love to hear the 757a with these horns and the WE728B. The WE728B speakers can be found but the 713C drivers and these horns seem rare enough to warrant trying some alternatives. Please keep me informed if the KS12027 horns are ever made again!!!
DeleteVery true!
DeleteHowever I wanted to emphasize the greater significance of the 414A and/or WE728B because in this application they cover 5 octaves of fundamental notes in a musical score whereas the horn/compression driver combo is dealing with barely 3 octaves with the top 2 octaves practically being harmonic overtones. See this chart - https://i.redd.it/ez2km0qyoj101.jpg
As always I'd be reporting my audio adventures. ;)
JE
Oh wow, I didn't know the 757a was crossed over that high? What is the crossover point for the 757a? I'd love to see a schematic for that speaker.
DeleteI suppose when you have a 728B, it would be a shame to cross it over so low, as they sound so nice full range (just missing some highs).
My reply was in the context of how I use my 414/32/802 where the KS12027 horn was tested in place of the 32C. I don't have the specs of the WE702A XO used in the WE757A system but given the size of the KS12027, I doubt if the XO point could be lower than 1kHz.
DeleteGoing back to the musical notes/frequency table I linked above, crossed @ 1kHz, the horn/driver combo is tasked with a 4 octave range. But only 2 octaves of that are fundamental notes vs. at least 4-5 octaves of purely fundamental notes handled by the WE728B.
In my Silbatone/Bae 755 box entry, I talked about the rich harmonic overtones coming out of J-Rob's WE728Bs despite the HF roll off. My point is, as great as the KS12027 and WE713C are, IMHO, the WE728B has greater effect on the overall sound of the WE757A system than the horn or compression driver.
JE
Hello Joseph,
ReplyDeleteAccording to an old WE ad, the crossover in the 757A is 1000Hz.
Here's an image:
https://imgur.com/a/1r4QRj9
RH
Hi RH,
DeleteI am aware of the crossover specification. But since I didn't have access to a schematic of a WE757A, I resorted to the Joe Roberts approach of running a high quality low frequency driver that plays well into the midrange (ex: WE728B or Altec 414) running in full range mode and using the horn/driver to fill-in the missing top octaves.
JE
DeleteThe KS-12027 is probably a little undersized for a 1000Hz crossover point.
Still, I think many people are eager to learn what this horn is capable of according to modern standards.
If your friend manages to reverse-engineer the horn and reproduce it in CAD, a scaled-up version could be 3D printed.
I believe the magic of the KS-12027 as well as the WE32, is located in the bend. Immediately after the wavefront leaves the driver's exit it is forced - inside the bend - to spread across the (expanding) horn throat. This is somewhat similar to the workings of a pinched throat or a diffraction slot, without the nasty artefacts.
RH
I agree 100% with every point you made, RH!
DeleteLet's see what JP comes up with...
Cheers!
JE
If you read the spec's for electro voice 12s and 12l drivers, it mentions the asymmetrical placing of the voice coil in the gap, which will reproduce odd and even harmonics, resulting in a more complex sound, overtones etc, They are almost full range and 100db efficient and work good in open back enclosures.
ReplyDeleteWill look into those drivers, thanks for the tip!
DeleteJE
Here's a pair of clones, made in Korea. They look (almost) original and are sold as such.
ReplyDeletePrice in 2013: $1300 for the pair.
https://f.share.photo.xuite.net/jacky_audio/1f2a696/8843315/369399907_l.jpg
This looks like an honest attempt to reproduce the original KS12027 including the indented 0.7" aperture for a WE713C driver. Thanks for sending a picture link!
DeleteI had an opportunity to "borrow" a pair of these imitation 12027 horns. I turned it down. The owner sent me a few close up pictures. The front part of the flange where it mounts to the back of the front baffle still has the draft angle from casting. Should be machined flat to provide a good seal. The transition at the 90 degree bent was done poorly.
DeleteSeeing this picture, I keep wondering why I can't find a 713a,b,c clone. Even if the price were high, as the drivers from GIP. Its almost like: if you don't have the room for the huge WE systems, then you are "stuck" using oddballs (I use a pair of 720A drivers augmented with various tweets) or the earliest Altecs we can get our hands on. The good news is that with careful shopping we can pull together a beautiful sort of 753C for 2-5K. The bad news is that there's no clear step up. Next stop: 50-100K for the real deal. As a middle-age member of this niche hobby, it makes me a little sad and frustrated that the early adopters of collecting the gear chose to expatriate basically all of it. Here I am calling Japan and contemplating Prius like money to import a dusty pair of old drivers. But I don't care about the collectible aspect. If someone told me that for 5-10K, I could get a faithful reproduction of 12027s and 713s, that would be so cool. Maybe I'm in the minority on this.
ReplyDeleteWishing you the best hunting for those WE drivers!
DeleteThanks! Please encourage your angle on the 027 (John?) to make them available in both throat formats. My first quote on authentic 713c drivers from APAC was $35K! I should have grabbed the pair I saw for $20K--a steal (haha).
ReplyDeleteBut I mean this in all seriousness: has anyone here seen the driver in person in pieces? Would it be that hard to knock off if someone had a pair? Is the diaphragm totally different in size and style from either the 555 style or on the other end, the lansing 801 or the 802B? If aluminum diaphragms are totally impossible to source, would it be possible to make a batch of 713b drivers using 720A diaphragms? I have seen just the 720A diaphragms come up for sale, and it could also be possible to use 720A drivers as donners too. Of course the 752A is even worse, but JR reports that it is a PM 756/7 tweeter. Lots more options if willing to sub in a non-fc driver.
My brother is a machinist, so I'm not speaking from total ignorance and idle speculation here. The machining is obviously a specialist job, but nothing that couldn't be done if one had the driver. The diaphragms on the other hand...