Altec 2-way horn system redux
Truth be told, I was never fully satisfied with the performance of the Altec 2-way which is why I never uploaded the old article in the Arkiv.
Let's recap how the 2-way horn system evolved...
The project was conceived in mid 1998 because I needed a monitor system that was more efficient than the OB/755 so I could listen to SE amps with 2 watts output and below.
I commissioned my cabinet maker neighbor to build 614 bass reflex cabinets and loaded them with Altec 419A 12" drivers + 811 horns (early version/heavy sand cast) and 804A compression drivers gathered from hamfests and radio shows. Crossover was a textbook 1st order/6dB/octave hinged at 900 hz and the horn padded down to match the sensitivity of the low frequency driver.
|Altec 614 cabinet plan|
Eventually I acquired proper 12" woofers - Altec 414As, which lack the upper midrange nasties of the 419As. The 414As have great midrange quality even if they lack the bass end of their larger 416/515 brethren.
|Note damping is applied only |
on two sides and the back.
802D compression drivers replaced the smaller magnet 804As
+ super tweets...
While exploring proper monophonic playback, I discovered the N1600C crossover which came with a single 605B Duplex I acquired. When I inserted it into my Altec 2-way, it sounded significantly better than the textbook parallel 1st order/6dB per octave crossover I had been using.
Using paper in oil caps and low DCR air core chokes, I cloned the N1600C and thought it was as good as it gets with my Altec components...
Lessons learned over the past 15 years
- Choose a woofer with excellent midrange characteristics.
- In hindsight, the 804A/811 was a much easier combination to tame than the 802D/811. Perhaps this is due to the smaller magnet on the 804A which makes it 3dB less efficient. Note: the 806A is similar in specs to the 804A but some sources say they are built differently.
- The 811 (as well as the 32B) sound better crossed over at a higher frequency than its rated cut off. In my implementation it's an octave above (~1600hz). Based on Western Electric documents I have read, the horn sections in the WE753C and WE757A were crossed over in a similar fashion.
- Don't be afraid to pad down the compression driver which is at least 10dB more efficient than the woofer.
- Try series type crossovers like the Altec N1600C above or N1500A which have lower insertion loss due to the 1st order/6dB/octave low pass filter.
- I only use paper in oil caps in my crossover.
Through the years that I had been attending radio shows and hamfests, I got to know people who opened rare opportunities for me to hear the Western Electric 753C, Western Electric 757A and Altec 1505 horns with Western Electric 555 field coil drivers on top of 825 cabinets loaded with 515s. Most memorable was a single Western Electric 15A horn + WE555 field coil compression driver driven by a pocket FM radio my buddy Ding and I heard at Scott Stilwell's shop in Philadelphia. The huge horn produced mid bass and rolled off like a 755C or 755E. Thus, "shouty," honky or harsh is not something I associate with good horn speakers.
|Altec 32B/802D + Altec 3000|
trial ca. 2009
A pair of Altec 32B horns I got in trade back in 2009 had been languishing in my storage bin despite realizing its potential after an initial test run. Given the 32B's pedigree - a direct descendant of the metal WE32A horn found inside Western Electric 753C monitors - I had an inkling that it would be better than the 811. But a busy schedule and other projects got in the way until I pulled them out to try before the end of 2013.
Replacing the 811 horns with the 32Bs transformed the 2-way horn system. The 32B/802D blended with the 414A/614 without any crossover alteration. If the 811 gives a front row seat perspective, the 32B is more like sitting at the middle to back row wherein instruments and/or vocals have been given enough time to reverberate in the hall. Exactly the kind of sound perspective I prefer. Despite its polite and refined presentation, the 32B still retains the transient speed and dynamic ability expected from a horn.
Although there is another tweak I am experimenting with at the moment, this horn is here to stay. As Johnny Hartmann sings, "...it's wonderful..."