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An Audio Diary (continued) Out Our Way, 2016 February 10, 2016 Please accept my apology for the "Out Our Way" hiatus the past couple
of years. Sometimes things get pretty busy. I added a new loudspeaker to the stable of speakers here in my listening room,
called "The Garden of Earthly Delights", and thought it might be informative to talk about the resident speakers.
I just added a pair of Altec A7-500-8 Voice of
the Theatre loudspeakers, manufactured in 1976, to my stable of speakers. Well actually, the speakers are on
long term loan from friend Harry. I don't think Harry is going to ask me to return them. Below you will find a photo showing
the left channel speakers of the speaker pairs used in the listening room.
On the left is the Altec Lansing A7 Voice Of The
Theatre speaker in its "stowed" position. In the center is one of the somewhat legendary Beveridge Model 2SW lens
loaded electrostats. On the right is one of the Po' Boy horn loudspeakers.
The next image shows the 9.5' wide by 6' high
mouth of the 20Hz (15 Hz flare frequency) horn used in the Garden of Earthly Delights. The horn is 29 feet long, driven by
two Altec Lansing 415 15" drivers. The 15 Hz flare frequency used in the design give a theoretical 20 Hz cutoff (-3 dB)
frequency. With some EQ to remove a bump centered at 33 Hz, the measured -3dB frequency is 20 Hz. In my next entry I'll have more to say about the three different sets
of speakers.
May 6, 2016
The Garden of Earthly Delights listening room now houses three different loudspeaker systems. These are the home designed and constructed Po Boy all horn system, the Beveridge Model 2SW electrostats, and the Altec A7 Voice Of The Theatre system, modified to use a crossover originally designed and implemented by the Frenchman Jean Hiraga, late in the last century, for use with his Altec A5 Voice of the theatre system. All of these are marvelous systems. Lately I have been toying with the Altec A7 system, getting what seems to me to be fabulous results. A now-extinct bias I had against vented loudspeakers interfered for years with any possibility that I might end up with a pair of the Voice of the Theatre speakers. Sometimes my pre-conceived notions have really gotten in the way.
In the photo above one can see the in-room locations used for the Po Boy and Beveridge systems. These speakers work fine as stereo pairs in these locations. The Altec A7 speakers are supported over carpet by plastic glides. The glides allow these 130 pound speakers to be easily waltzed into position in front of the Po Boys, which turns out to be a great position to play them from. Great sound stage.
The Monster In The Attic Subwoofer:
The mouth of the Monster is shown in a photo above.
The Monster In The Attic mono subwoofer, which plays down to 20 Hz and up to 160 Hz, supports each of the three loudspeaker systems now alternatively in use. The sub is played up to 160 Hz with all of the three speakers systems. This works very well. There is never a sense of being able to locate the subwoofer, or a sense of confusion over the location of bass instruments. And 20 Hz bass, when present on the program material, is marvelous. This subwoofer is driven by an inexpensive 100 watt mono plate amp from Parts Express. Input to the plate amp is taken from the speaker system being played. A pair of Altec Model 415 paper cone biflex drivers excite the 29 foot long bent sub-horn, which has mouth height of 6 feet and a mouth width of 9.5 feet. The biflex drivers seems a strange choice, but I used what I had on hand, and they work beautifully.
The Po Boy System:
The first system set up in the Garden, maybe 10 years ago, was the Po Boy horn system, which consists of a J shaped 70 Hz horn (j-horn) for the bass, a conical horn for the midrange, and a tractrix tweeter horn. This is a 16 ohm triamplified system. Crossover points are 350 Hz between woofer and mid, and 6000 Hz between mid and tweeter.
The Po Boy system is triamplified. Electronic crossover and room equalization are provided by a DEQX digital equalizer and crossover unit.
The woofer paper cone drivers are 8 inch units, two per channel, manufactured by B&C of Italy. The midrange phenolic diaphragm compression drivers are RCA Model 9584A units manufactured by RCA for a couple of years around 1960 to complement their theatre sound systems. The tweeter Mylar diaphragm compression drivers are by the German company BMS. This is a very sweet sounding horn system, perhaps because there are no metal diaphragms.
The stereo amplifier for the woofers uses Sovtek or Winged C 6550 tubes in push-pull. The Sovtek's do a very nuanced bass. The monoblock amplifiers for the mids use single Chinese 2A3C tubes operating single ended. The stereo amplifier for the tweeters uses single Amperex Bugle Boy EL84 tubes operating single ended.
To be continued . . .
November 25, 2016 More about the Altec A7 and A5 Voice Of The Theater Speakers
So many projects, so little time. I've recently added a page to this site dedicated to Altec A7. You might want to check it out at this link:
Altec A7 Voice Of Theatre Speakers |
