OJAS 529B Horn

During my visit to the OJAS listening room late last year, Devon asked me to evaluate a pair of horns OJAS developed in collaboration with Lycan R&R. The OJAS 529B is a 500 Hz horn rescaled from the large format Altec 329A for use with 1" format Altec/GPA compression drivers.

  This horn was designed with a throat inspired by the Western Electric 32 horn to avoid the harshness and distortion I (as well as others 😉) associate with the Altec 811 and 511 horns, 

For more details about this horn's evolution and construction, please click here.

3D printed WP12024 horn from Lycan R&R

In late September, I received a message from Trieu of Lycan R&R, asking if I'd be interested in evaluating his 3D-printed prototype pair of multi-cell horns.

Before proceeding further, this blog entry contains a lot of hyperlinked texts to either previous entries or other sites pertinent to the article (e.g. "Lycan R&R" above). Mousing over and clicking those texts will open the link on another page. Thanks!

Design notes from Trieu: "These horns are slightly wider. The original KS12024 has a rather narrow 50° horizontal dispersion. When updated to the 1" driver opening, the wider initial diameter of the of the 1" driver would not allow for the throat geometries to work correctly. I felt the slim vertical profile of the original KS12024 is important sonically.

The best way to maintain it is to increase the horizontal width via a wider angle. So I increased the horizontal dispersion to 62.5° allowing for the proper expansion and geometries of the throat piece. BTW, I used carbon fiber infused PLA filaments."

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

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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...😞

Altec 32A, 32C, Emilar EH1210, EH800, EH500 and Faital Pro STH100

+ 

This is a cumulative report on horns I listened to and tested from May 2016 until the end of 2017. All the tests were done through the mono hifi rig using the above Altec 802 compression driver fitted with a GPA 34852 diaphragm + an Altec 414A in a repurposed Altec 861 cabinet running in full-range mode tied together by a 6dB/octave high pass crossover/EQ hinged at 2500 Hz. 

Altec 32A and 32C

Altec 32A (top)
Altec 32C (bottom)

 The Altec 32A (metal) and 32C (plastic with ribs) horns are lineal descendants of the Western Electric 32A horn as found in the WE753 speaker system. I've had the plastic 32C since '09 and lived with the metal 32A for over a year and can say that these are the most sophisticated native 1" horns I've heard and owned to date.

Altec 32A

Altec 32A

Altec 32A + 802 + 414A

Altec 32C

Altec 32C

Altec 32C + 802 + 414A

Metal or plastic? 

It's ironic that the later plastic 32C sounds more vintage than the earlier metal 32A. Definitely, the longer throat of the earlier 32A and the type of material used for construction influence the sound. But in what capacity, I cannot surely define. The iPhone RTA results reinforce the cooler and more modern sound I hear from the metal 32A versus the warmer and sweeter plastic 32C.

The magnitude of difference is not great. Similar to the 20275 vs. 34852 Altec 1" aluminum diaphragms - distinct enough not to be used as a stereo pair but still excellent performers in their own right. However, those who are expecting a front-row presentation may find both these horns too laid back.

Watch out for roughly finished throat edges in the 32A which are detrimental to performance. So far all the plastic 32Cs I've seen have very smooth throats.

Emilar 

As soon as I landed in the US in May 2016, I tried to collect the Emilar horns talked up by Joe Roberts in his war against the devil's trumpets before they became unaffordable. 😉

EH1210

Emilar EH1210

Emilar EH1210 + 802 + 414A

This wasn't recommended by J-Rob but it was cheap enough to try. The EH1210 has the most extended high frequency response according to the iPhone RTA but subjectively it was the least refined sounding horn in this group. I think one can do much better with some modern offerings, see the last entry below. 

Emilar "Bowtie" EH800 and EH500

Emilar EH500 (left) + Emilar "Bowtie" EH800 (right)

WARNING: these two Emilar horns are heavy cast jobs, doing the audiophile knuckle test can result in serious injury! 😃

EH800

Emilar "Bowtie" EH800 

EH800 + 802 + 414A

If you are looking for a modern sounding horn with a more forward presentation but without the shout and distortion of the Altec 811, then this is the horn for you. Exciting sound but guaranteed not to make your ears bleed. 

I think the low end cut-off at 800 Hz spec is a bit optimistic. For maximum satisfaction start around 1200 Hz and work upwards.

EH500

EH500

EH500 + 802 + 414A

This is a native 2" horn with a finely machined 1" - 2" throat adaptor. Once again I find the 500 Hz cut-off an overestimation for a horn of this size. I'd start crossing around 900 Hz and up. 

My ears do not agree with the iPhone RTA. I found this horn to be mellower than the EH800 "Bowtie." The tonal balance of the EH500 is somewhere in between the Altec 32A/B/C and the EH800.

EH500 in Large Format Mode

EH500 sans adaptor + Renkus-Heinz SSD3301

With the JEL N1600 XO in tow, I removed the 1"-2" throat adapter and bolted the 2" exit Renkus-Heinz SSD3301 directly to the horn to sample large format tones. I got juicy mids and smooth highs from this combo.

Late addition:

Faital Pro STH100

Faital Pro STH100

I wanted to sample what can be had off the shelf at Parts Express for under $100 and ordered a pair of these small aluminum tractrix horns by Faital Pro.

STH100 + 802 + 414A*

*RTA was done at a later date in another location,
hence the difference in low frequency response 

With the Altec 414A running full range and the STH100/802 combo crossed at approximately 2500 Hz, I got very clean (if a bit dry) high frequency harmonic augmentation with no nastiness at all. To my ears, this tractrix horn is preferable to the EH1210.

CODA

For the past 4 years, I've been blogging about horns and compression drivers. Justifiably, the horn/driver combo seasons the speaker system's sonic flavor. However, these components only cover the upper three octaves of the audio band (mostly harmonic overtones). I would be remiss if I didn't stress the greater importance of the Altec 12" 414 woofer/midrange because it is tasked to reproduce most, if not all, of the fundamental notes in music from 30 Hz to 4000 Hz. That's seven octaves, practically the frequency range of a piano.  

I've been trying, but so far haven't found alternative 15" or 12" woofers that play the midrange as well as the Altec 414. The good news is, Bill Hanuschak of Great Plains Audio told me last year that they still re-cone 414s and their product page lists an Alnico 414-8B(16B). 

Altec 2-way XO Redux

This is an update on crossovers I use for the Altec 2-way speakers.

JEL N1600 Crossover

JEL N1600C + HF EQ
optimized for the 802 driver fitted with the original
16 ohm 20275 diaphragm

The above crossover circuit, as discussed in this previous post, was optimized for my cherished pair of green Hammertone Altec 802Ds fitted with the original aluminum 20275 diaphragm, which has an aluminum wound voice coil. To my ears, this diaphragm has a more prominent midrange response which necessitates rolling off the upper midrange/lower high frequencies of the 414A woofer for flatter response.

JEL Universal Altec 2-way XO

For the Altec 802 driver equipped with the 34852 (16 ohm) or 34647 (8 ohm) diaphragms, which have copper wound voice coils, I recommend the 6dB/octave crossover circuit below which is hinged at around 2500 Hz + high frequency EQ boost. This aluminum diaphragm has less energy in the upper midrange giving a tonal balance that sounds more extended in the high frequencies compared to its 20275 predecessor. In this implementation the Altec 414A woofer is connected as a full-range driver inspired by Joe Roberts. 

JEL Universal Altec 2-way XO with HF EQ circuit

Altec 414A + 32A/802/GPA 34852
+
JEL Universal Altec 2-way XO

I've also used this crossover successfully with the Altec 802 driver fitted with the Symbiotik diaphragm, Emilar EA/EC175 and Renkus-Heinz SSD1800/1400. Please take note of the different capacitor values for 16 or 8 ohm drivers.

Simplest Crossover

If you want the simplest crossover, my buddy Joe Roberts listens to his Altec 414A/802/32 set-up with the woofer in full-range mode + a 1.5uf paper in oil cap for the compression driver, no L-pad or HF peaking EQ circuit. See his Audiokarma post for more details.