Azzolina Audio KS12024

Western Electric KS12024

Western Electric KS12024
Note: ~ 140° throat bend

The Western Electric KS12024 is a 2-piece cast aluminum 4-cell sectoral high frequency (800-1000Hz cut-off) horn with a 50°H x 40°V dispersion pattern. It was implemented in the Western Electric L-8  and L-9 speaker systems.

Western Electric L-8
from the Silbatone Collection

Western Electric L-8  = 1 x WE754A + 1 x KS12024 + 1 x WE713B (phenolic diaphragm)

Western Electric L-9

Western Electric L-9 = 2 x WE754A + 2 x KS12024 + 2 x WE713B

Western Electric L9
(Note: 2 x WE713B)

Images were taken from J-Rob's KS12024/Western Electric L-8 post at Hifi Haven. If you want to learn more about the Western Electric L-8 and L-9, you can download the pdf file at the bottom of Joe's post.

Read about J-Rob's musings (post #125) about the original KS12024 and Azzolina repro at Hifi Haven.

Late 40s Western Electric Brochure
from www.hifilit.com

The KS12024 horn was from the same era as the WE32A horn that included the venerable WE757A studio monitor, WE713x compression drivers, WE755A, WE756A and WE728B direct-radiator speakers.

Having been a long-time user of the Altec 755A, Altec 32A/C and more recently an Altec 756B, I consider this period as the golden age of design and manufacture of permanent magnet transducers. So when J-Rob offered to loan his personal pair of Azzolina Audio 3-D printed KS12024 horns for me to blog about, it was a privilege and opportunity difficult to pass up.

Azzolina Audio KS12024

I've been a frequent visitor to the ElectraVolt blog but never imagined I would be listening to, let alone reviewing, Charles Michlin's KS12024 reproductions. 

The original Western Electric KS12024 has a 0.7" round opening* but this Azzolina remake was optimized for 1" compression drivers like the Altec 802 that I am using for this review. As relayed by J-Rob, Charles claims the oval (rather than round) aperture sounds better. 

*All the WE horns from this era (including the 32A) were designed for use with the WE713x compression drivers and shared the same aperture size

Just like the original, this is also a true 4-cell compound sectoral horn. AFAIK, this is the model built from an amorphous plastic material. Everything else you need to know about the Azzolina KS12024 can be found here.

Testing

Altec 414A/614 + Azzolina KS12024/802 + 3000H

The Azzolina KS12024 horns were tested in the Altec 2-way system. 

Altec 414A in 614 cab 

Altec 414A woofers in 614 bass reflex enclosures running in full range mode

High-pass XO w/HF eq

Altec 802-8D compression drivers (below) with 16 ohm GPA 34852 diaphragms were mounted to the horns using the above high-pass crossover

Amorphous Plastic Azzolina KS12024 vs. Plastic Altec 32C

Altec 32C + Altec 802

This horn presents a back row perspective and may sound too laid back to those who prefer a closer to the stage presentation. The mid-range is juicy, full and vivid without a hint of shout. While the highs are feathery smooth, silky and airy, which I've only heard from its smaller sibling, the Altec 3000H. Tish (my wife) describes this horn as sublime. I think the 90°H x 40°V dispersion helps provide that holographic and lush atmosphere. 

I've written so much about this horn. Just use the search button on the right hand corner to find past entries.

Azzolina KS12024 + Altec 802

I was initially lured into the 3D-like midrange this horn produced and that lingered on. There's an uncanny realism to male and female vocals as well as musical instruments that renders an "in your room" presence. Compared to the 32C, this horn offers a front row perspective. Yet there isn't a trace of harshness or shout. Definitely a horn that will appeal to those who find the 32C too laid back yet need a horn that doesn't sound like a horn.

It is superior to the 32C in terms of articulation and detail without ever sounding analytical. There's a lot of snap, if I may borrow a term from its owner 😉, just like its stable mate - the WE/Altec 755A.

Azzolina KS12024 + Altec 802 + Altec 3000H

Tish thinks it is as good as but not quite as lush as the Altec 32C. I agree. This is primarily a tonal balance issue. Due to the prominent midrange, the extreme treble frequencies are slightly subdued giving a less airy atmosphere. Adding the Altec 3000H to fill in the uppermost octave helped in approximating the lushness of the 32C. But I still found myself wanting more "hall sound." I speculate that the KS12024's narrower 50° horizontal dispersion contributes to the comparatively austere background. Perhaps I am belaboring this point since my personal preference when I attend concerts is to sit towards the back row so I can relish equal amounts of direct and reflected sound.

Summed up

2 x KS12024 = 100° H x 40° V

These two horns share the same sonic DNA but are genetically modified for different applications. The more up-front and involving Azzolina KS12024 betrays its theatre heritage versus the mellower 32C, which was intended for near-field monitoring. I can't help but wonder if a horn design combining the virtues of both designs is a possibility.

Magnavox CDB473 and Philips TDA1541

With barely 400 CDs and just a handful of SACDs and DVD-As in my collection, I didn't invest heavily on silver discs as much as I did on LPs. Likewise, I've spent much less on digital playback hardware.

However, due to the resurgence of interest in vinyl LPs and streaming, used CDs are available all over at bargain prices. Since I'm not committed to burning all my silver discs to a hard drive having had my own share of failures in the past, I was inspired to look into maximizing my CD playback system.

Sony DVP-NS755V

For the past 15 years, I relied mainly on this Sony DVD/SACD/CD player. It showed me that SACDs had an edge over CDs. Yet it proved that neither format was on equal footing with my LP set up. This is a polite sounding machine that also doesn't do anything great. Prior to the Sony, I owned an early bitstream (ca. '93) Philips CD921. It sounded sooo boring, I connected the digital out to an Audio Alchemy Dac In The Box to spice things up a bit until it (the CD921) prematurely died.

Nevertheless, I was still missing the lively sound of my first CD player, a Magnavox CDB472 I purchased in 1987. I had an inkling that the "bitstream" buzzword of the 90s was not an effort to improve sound quality but a watered down technology/marketing hype for manufacturers to maximize profits. Since I was more interested then (as now) in older technology, I placed digital audio tech aside, focused on learning how to build triode amps and high-efficiency speakers.

Denon DVD-2910

To re-acquaint myself with the few DVD-A titles I have, I acquired this reasonably priced Denon DVD-2910 multi-format compatible relic from the mid-2000s. It weighs almost 10 pounds, is built like a tank, is mechanically and functionally more refined compared to my entry-level Sony above due to higher quality materials (more metal). If this didn't sound better, it can serve as a CD transport for an external DAC. Fortunately SACDs did sound better, but not sure about CDs though...

Time Travel Machine

Philips TDA1541A

Ever since I embarked upon improving my internet streaming set up, I had to refresh and update my knowledge of Digital Audio, PCM, DSD, DACs, etc. It was inevitable that I'd encounter R2-R vs. delta-sigma debates in internet audio forums. I also discovered that there's a sub-culture of CD collectors/music lovers/DIYers (as opposed to meter readers/latest is best audiophiles) who maintain that the most musical sounding CD players are those 80s machines fitted with the more complicated and expensive-to-manufacture 16 bit Philips TDA1541 chip.

Under the hood of a CDB473

Out of retro-tech nostalgia, it was only fitting that I trace my steps back to my first CD player in ca.'87, the Magnavox CDB472, which used this ubiquitous chip. I did a bit better this time around with the higher model CDB473 which is equipped with a co-ax digital out, and can also be used as a CD transport. Considering that this unit celebrated its 30th birthday in December of 2017, it is a glowing testament to Philips' excellence in engineering and manufacturing that it still works today. 

Let's see how the Magnavox's 16 bit DAC chip which was truly designed for Red Book CDs fares against the Delta-Sigma DAC chips found inside the Denon and Sony.

Magnavox CDB473

From the very first CD I fed into the tray, the Magnavox sounded more transparent and dynamic while the Denon and Sony sounded comparatively veiled and compressed. Even my wife heard its superiority. The CDB473 may not possess ultimate refinement but there's an honesty in its musical presentation that draws the listener into the music, just like analog LP does. 

Truth be told, I don't remember the CDB472 sounding this good back in the 80s. But I had a totally different system then and was just beginning to wean myself off of the influence of underground audio journals of the era, which were largely pro-vinyl LP/anti-digital CD. I guess hindsight is indeed 20/20 with regards to the Philips TDA1541. I was too young to learn and appreciate its virtues. Besides, a year after this CDB473 was manufactured, Philips introduced bitstream technology, followed in the late 90s by Delta-Sigma, both claiming greater linearity. These were the technologies that dominated the market from the 90s to the present and also the sound I associated with the playback of 16-bit/44.1kHz mastered CDs.

Parts Express 1" Horns and Waveguide Buy Out Specials

July was a hectic month - four 4th of July concerts with Harrisburg Symphony + two concerts at the Shippensburg Summer Music Festival. It was a welcome respite to receive an invitation from Joe Roberts to meet him at his mom's house in South Philly after I was done with all those gigs.

Leica II + Summitar 50mm f2
Ilford FP4+ in Kodak HC110

He gave me a tour of his old neighborhood, pointing out areas where he started his archeological expeditions as a kid. For lunch we stopped by this hoagie shop for really great Philly cheesesteaks. 

It was very interesting to listen to his recollection of South Philly as a kid, and how the area continues to evolve as people of different ethnicities, socio-economic and cultural backgrounds come and go.  

Before I-95 swarmed with rush hour traffic, I had to head back north with this box filled with horns from Joe. I didn't envision writing about 1" format horns again since I posted this blog entry last February. But after spotting the Azzolina KS12024s, it was hard to pass up this opportunity. Meanwhile, this post will focus only on the Parts Express horns.

Testing

I used Altec 802 1" compression drivers fitted with GPA 34852 16 ohm diaphragms mounted on top of Altec 614 cabinets loaded with 414A woofers (running full range) with the crossover below tying things together. All listening was done in stereo in the man cave.

High pass @ ~ 2500 Hz

I used these two horns as references and for the first time I was able to convince my wife, Tish, to indulge me with her sonic impressions.

Altec 32C

Tish and I love this descendant of the old school WE32A horn. She describes it as sublime.😉 

Emilar EH500

This is my favorite horn from the 70s. It was designed by Jonas Renkus who worked with John Hilliard at Altec Lansing. 

Parts Express Specials 

Round 1 

(deeper/longer exit Altec 802)

Parts Express: 299-2303

+

Altec 802

There is an ongoing thread at Hi-Fi Haven about cheap horns where this particular horn/waveguide was mentioned. Its specs are listed as a 600 Hz, 10" x 14" exponential horn waveguide with a 90° H x 40° H dispersion pattern, made out of heavy ABS plastic. Price: $12.88/ea.

Sound

Tish: Not bad, but not as lush sounding as the Altec 32C. It will eventually hurt my ears. 

JE: Tonal balance is reminiscent of the Emilar EH500. However the sound gets congested with complex musical passages (especially at higher SPLs) which can cause fatigue during long-term listening.

Community UC-1
part# 299-522
+
Altec 802

Dimensions: 10 3/8" W x 5 7/8" H x 6" D

Dispersion: 90°H x 40°V

Cut off frequency: 2000 Hz

Price: $4.48/each

 I had to DIY adapter plates to mount the 802 drivers.

Sound

Tish: Harsh and shouty👎👎👎

JE: Sounds better disconnected. What were you thinking J-Rob???🤣

Faital Pro revisited

Faital Pro STH100 + Altec 802

Dispersion: 80° H x 70° V

Dimensions: 7" W x 4 3/4" H x 3 5/8" D

Material: Metal

Price: $67/each!!!

Sound

Tish: I like this best among the three - easier on the ears compared to the other two, but not even close to the 32C.

JE: I am less impressed this time around despite the clean sound. It has less congestion, harshness and tizz than the B52/QSC clone 299-2303. But the presentation still falls far short of what I hear live. With the recent price increase, I can no longer recommend this unit.

!!!STOP PRESS!!!

Pasted below is a post by @ARX in this Hi-Fi Haven thread

Gentlemen,

Very interesting experiments with different types of horns and waveguides (the B-52 1" QSC clone is a waveguide), both vintage and more recent designs.

The 802D with the B-52 1" might not be an optimal combination. The original QSC PL-000446GP was designed by Mark Engebretson, former VP of Engineering at QSC, to be used with Celestion compression drivers. From the many measurements available online it's obvious this waveguide performs best with modern, pancake style compression drivers, that have a short exit instead of the deeper/longer exit of most vintage drivers like Emilar, Altec etc.

You might try B&C, Celestion, Beyma, BMS and similar 1" drivers.

There's much more to the underlying physics, but it should come as no surprise the EH-500 and Altec 32A/B do indeed sound wonderful with the vintage drivers. The gradual expansion of the wavefront from driver diaphragm to horn mouth is (almost) perfect. On the other hand, a pancake driver behind an oldskool horn, with a few exceptions, is unlikely to yield spectacular results.

Altec 802 (left) + Renkus-Heinz SSD1400-8 (right) 

The only pancake type (short/fast exit) 1" compression driver I have on hand is a pair of Renkus-Heinz SSD1400-8. This is a smaller magnet version of the SSD1800, which I got to know quite well in the attic. Hence, I had a gut feel that I was going to learn something important from @ARX. So the SSD1400-8 was pressed into service for another round of listening.

Round 2 

(short/fast exit Renkus-Heinz SSD1400-8)

Parts Express: 299-2303

+

Renkus-Heinz SSD1400-8

 According to ARX's post above, this is a clone of the QSC waveguide, which was designed to be paired with a B&C DE250 compression driver in the Econo-wave project at Audiokarma.

With the short exit R-H SSD1400-8 mounted, this waveguide was transformed. Although not quite on the same level, the sound now more closely resembles the Altec 802/Emilar EH500 pairing. The congestion I heard in Round 1 is gone with a substantial gain in midrange lucidity. Long term listening fatigue is no longer an issue since the sound has opened up with a nice airiness to it.  👍👍👍

Community UC-1

part# 299-522

+

Renkus-Heinz SSD1400-8

This horn became a lot more listenable with the SSD1400-8 mounted behind it. It sounded even better crossed over @ 5kHz. Detailed and airy but the midrange isn't quite as vivid as the B52/QSC clone/299-2303. For the record, Community compression drivers are also short/fast exit (pancake) designs.

Faital Pro STH100 

+

Renkus-Heinz SSD1400-8

Sadly, this tractrix horn became unlistenable with the SSD1400-8. Probably a mis-match? Faital Pro 1" compression drivers look more like old school Altec 802s and Emilar EA/EC175.

Parts Express Horn Wrap

Two important lessons learned:

1. Thank you very much @ARX for enlightening me! Otherwise, I would have joined the ranks of fake news bloggers. 🤣

2. My preference for matching harmonically rich-sounding components will always entail a classic pairing of units that are long out of production and are becoming more unaffordable as the years go by...😞

Raspberry Pi 3B+

The FM tuner has been a de rigeur music source in my audio system. Between the dwindling quality of FM broadcasts and proliferation of internet radio and music streaming apps like Pandora, Spotify, Tidal etc., I had to jump the bandwagon with my first generation iPad mini.

But as I delved into how to get the best sound from the internet, I realized that I could improve upon the iPad mini > USB DAC set up for not much $$s.  I've seen Blogs and YouTube videos on how the Raspberry Pi 3B+ (henceforth, RPi3B+), a 40 something dollar single board computer, can be configured as a hi-fi music player.

 A discussion of the RPi3B+'s sonic merits in the Joe-list initiated by a long-time audio DIYer, Larry Moore, was pivotal in my decision to try it. He recommended using the RPi3B+ with an I2S Allo Boss DAC, moOde 4.1 + a linear power supply. Since I already had a couple of USB DACs, I just opted for the cheapest RPi3B+ bundle with a 5V/2.5A SMPS (switched-mode power supply), a molded transparent acrylic case and a couple of 16GB micro SD cards from Amazon.

The software for the RPi3B+ is contained in a micro SD card, which is inserted in the bottom mounted front slot. At the back is an ethernet port + 4 USB ports which can be loaded with USB thumb drives filled with music files and/or connected to an outboard DAC. On the right side, there's a mini USB for 5V power, an HDMI port and a 3.5mm below hi-fi grade audio out. 😞 To the left is a 40 pin GPIO header where an I2S S/PDIF device or DAC can be attached, which supposedly offers even better sound due to less jitter.  

 Once the software is loaded and configured the RPi3B+ will be operating "headless" (no monitor or touch screen). All functions are accessed and operated via a web browser on an iOS/Android device or laptop.

moOde 4.1

moOde GUI

Installing moOde 4.1 was not an easy task - not for me, at least. I had to bring the TV near the router to function as an HDMI monitor and plug a USB keyboard on the RPi3B+ to type commands which reminded me of WordStar word processing on an IBM XT/AT in the 80s. After two trials using the EZ install process and valuable assistance from the good guys at Hi-Fi Haven, my moOde 4.1 build was a success. 

The only glitch I had with moOde 4.1 is that Airplay doesn't work with the following DACs via USB: AQ Dragonfly Black, XtremPro X1 and Topping D30. So far I can only get moOde 4.1 Airplay to work with the Xiang Sheng DAC 01A below. I'm hoping that an update will address this issue. 

Volumio

Volumio GUI

After the moOde 4.1 initiation, installing Volumio was a breeze. The software is downloaded as a file, "etched" on a 16GB micro SD card and then set up for Wi-Fi connection. No MS-DOS style typing required. Everything went smoothly even for a not-too-tech-savvy computer user like me. There were no issues with Airplay connection, regardless of which DAC was connected to the USB port. The choice of internet FM radio stations is at par with moOde 4.1 and there's a "plug-in" for YouTube. There's also support for Spotify subscribers. Since I only have a Spotify free membership, I "Airplay" from an iPad.

Sound

I wouldn't have known that the software itself can influence the sound in computer audio if I didn't embark on a Raspberry Pi journey. The more complicated set up procedure and USB > DAC issues notwithstanding, moOde 4.1 rewards the listener with deeper and punchier low frequencies, crisper high frequencies and more lucid midrange. Volumio sounds as if the leading edge of transients are slightly rounded off. The difference is actually quite subtle and only discernible after extended listening to both platforms.

According to MikeyFresh, a moderator at HiFi Haven who helped me a lot with the moOde install, "Moode is a very lean distribution, perhaps that's why it can sound better, it runs super efficiently and thus taxes the RPi3's CPU and RAM very little, which in turn produces less EMI/RFI to contaminate the signal." 

iPad mini as controller, RPi3B+ and Topping D30 DAC

I'd hate to bid adios to my beloved Scott LT110B and Dyna FM-3 tube tuners, but the RPi 3B+ is getting more air time nowadays. 

!!!STOP PRESS!!!

I initially considered the cheaper Hifiberry Digi+ Pro, but based on the positive reports I've read on the internet from RPi users, I took the plunge and got the more expensive Allo Digione S/PDIF HAT (aka Hardware Attached on Top) instead. A layer of electronic hash was removed by this I2S device and took the sound quality to another level = more analog, less digital. 

Lafayette SK98 Reunion

 
Many years ago, I wrote about vintage Japanese drivers. From that survey, the 8" Lafayette SK98 aka Pioneer PIM8L full range driver emerged as a favorite due to its vivid midrange, balanced by respectable high and low frequency extension. Thinking that I could easily find replacements, I eventually unloaded both pairs to friends who didn't have the budget for Altec 755As. 

Lafayette SK98s in Altec 618 clones

Over 10 years have elapsed and I am happily reunited with a pair of SK98s, courtesy of my friend at Junkyard Jukebox. He believed that his treasured pair in Altec 618 clone cabinets should be in the JE Labs collection.

 Welcome back old buddy and thanks J-Rob!