Jan 062016
 

In my Part 1 post I introduced you to Gary Fischer and the Altec-Lansing A5 Voice of the Theatre restoration he did for me that forms the basis of the Altec A5 VOTT Project here at Jeff’s Place.

Jeff's A5 VOTTs as restored by Gary Fischer.

Jeff’s A5 VOTTs as restored by Gary Fischer.

For my restoration, I chose two 825B bass horn cabinets, two 515B Alnico low-frequency drivers, two N-500-C crossovers, two 1005B 10-cell horns, and two 288C Alnico high-frequency compression drivers, which is a classic Altec-Lansing A5 Voice of the Theatre combination of components from that period, as shown in the brochure below.

Altec literature from GPA

In my Part 2 post, I described the labor intensive process that Gary goes through to restore the vintage 825B bass horn cabinets. It’s a lot of work!

825B bass horn cabinets going through the restoration process.

Then in my first post of 2016 – The Vintage Beat: An Altec A5 VOTT Project Update – I discussed the dismal performance I got on first listening with an Altec N-500-C crossover that was malfunctioning, which presumably got the worse end of being shipped.

I wasn’t sure what to expect from the N-500-C crossovers, but given that my Stokowski VOTTs were sounding so good with their N-500-D crossovers, I was hopeful. So much for that.

Altec 500C crossovers.

Altec N-500-C crossovers.

I boxed up the N-500-C crossovers  last night to send back to Gary, and Gary is going to send back a pair of Altec N-500-D crossovers like I have in my Stokowski VOTTs to replace them with.

It will make for an interesting comparison to see how the N-500-D crossovers sound on the A5 VOTTs once I get them from Gary, and will help give some insights to the Stokowski VOTTs as well.

A5 crossover circuit diagram from Yazaki-san.

‘Real Sound’ version of the Hiraga-style A5 crossover circuit from Yazaki-san.

In Part 2 I also discussed the plan to build a pair of Yazaki-san ‘Real Sound’ versions of the Jean Hiraga designed crossovers for the A5 VOTTs, which I find to be a tremendously exciting part of the project!

I have mentioned to Yazaki-san how handy the adjustability of the N-500-D crossovers is for getting the high-frequency horns to integrate smoothly with the Stokowski VOTTs, as well as the adjustability of Werner Jagusch’s pair of autoformer based crossovers (below) for doing the same with the A5 VOTTs.

As a result, Yazaki-san has suggested we use a quality NOS wirewound 20Ω to 30Ω variable resistor at the R3 position in the Hiraga-style A5 crossover circuit shown above, which will allow us to find the best point for the level of the 288C horn driver.

The NOS wirewound VR that Yazaki-san wants to use is the same one that he chose for the DA30 SET amplifier he built for his friend, Ookubo-san, and he is going to kindly send them to me for the circuit. Thank you Yazaki-san!

I’ll get started on breadboarding the crossovers as soon as the NOS wirewound VRs arrive from Yazaki-san, and the inductors arrive from Daryl at Arizona Capacitors.

We’re getting close!

Werner's autoformer based crossover for the Altec A5.

Werner’s autoformer based crossover for the Altec A5.

Additionally, I described Werner Jagusch’s pair of autoformer based crossovers (€549 Euros/pair) that I have been experimenting with, and how I found them to sound pretty nice with the high-frequency volume set on the sixth terminal screw from the left, with the roll-off starting frequency dial set at the 9 o’clock position. Those settings gave a rich, dark, sweet presentation to the A5 VOTTs which was nicely musical.

I also promised that in my next post on Gary’s restoration of the A5 VOTTs that I would cover the 515B Alnico low-frequency drivers, the 288C Alnico high-frequency compression drivers, and the 1005B high-frequency horns.

Altec 825B bass horn with 515B Alnico driver.

Altec 825B bass horn with 515B Alnico bass driver mounted inside.

Let’s talk about the 15-inch 515B Alnico low-frequency drivers first. Alnico is an acronym for the aluminum (Al), nickel (Ni), and cobalt (Co) that is alloyed with iron to make the magnets of the motor structure. I suppose I should make a brief mention that Alnico magnets are preferred by quite a few musicians, audiophiles, and music lovers, for their reputed ability to convey a finely textured, vivid, and colorful presentation of the music with superb micro-dynamics and ‘tone’.

The 515B Alnico low-frequency driver has a frequency response of 20Hz to 1000Hz, 103dB sensitivity, a 4.4 pound Alnico magnet rated at 14,750 Gauss, and weighs in a 26 pounds.

Given that Altec designed the 515B Alnico low-frequency drivers to essentially last forever blasting away behind the screen in a theater, I figured Gary wouldn’t have to do much more than pick out some nice vintage examples from his supplier, then check them to make sure they are not damaged & they’re working properly, and finally, install them into the restored 825B bass horn cabinets.

515B Alnico low-frequency driver front view from the 825B bass horn cabinet.

When I asked Gary about his drill for inspecting the 515B Alnico bass drivers, he told me, “I check the condition of the paint. I make sure there is no voice coil rubbing, and that there is no discoloration in the lead-in wires to the voice coils. If the lead-in wires are black in color they are burnt and junk. I make sure there are no tears or scratches on the cone paper, and that the cork surround is intact. Finally, I power them up to less than abusive levels to warm them up, then I turn down the volume and listen for flaws.”

Altec 288C 24-Ohm compression driver.

Altec 288C 24-Ohm compression driver.

Like the vintage Altec 515B Alnico low-frequency driver, the vintage Altec 288C Alnico high-frequency compression driver was built equally robustly for theatre duties.

The Altec 288C Alnico compression driver gives smooth response from 500Hz up to 16,000Hz, has a sensitivity of 115dB, a voice coil diameter of 2.8-inches, and weighs 20 pounds (Almost as much as the 515B!).

Gary gives each 288C a thorough check, and more importantly, he services the drivers by replacing their diaphragms with new aluminum diaphragms from Great Plains Audio (who are essentially what’s left of the original Altec manufacturing group), to make sure the high-frequencies are up to snuff.

Altec 288C compression drivers have 24 Ohm impedance, but you can change it to 16 or 8 Ohms depending on which diaphragms are installed. Great Plains audio says, “When the original 24 ohm impedance is not required, use the diaphragm manufactured for the Altec Lansing 299-8A, Altec original part #25884 (8 ohms), or the diaphragm manufactured for the Altec Lansing 299-16A diaphragm, Altec original part #25885”.

Gary installed the 16 Ohm diaphragms in my 288C drivers.

Altec 1005B horn & 288C driver.

Altec 1005B horn & 288C driver.

The 288C Alnico compression driver is mounted to the 10-cell Altec 1005B horn. Gary told me the original horn sled for the 1005B high-frequency horn – designed for filling large spaces with sound – puts it up too high for domestic use, and as a result it doesn’t blend together very well with the 825B bass horn in the smaller spaces of  home listening environments.

Gary’s mounting system puts the ‘big room’ 1005B 10-cell horn down lower so it works better in domestic listening environments.

Gary recommended a lower mounting system for the 1005B high-frequency horn, saying, “My means of positioning the horn is so much better for speaker phasing than the original sled. My little system is simple and it brings the high-frequency 1005B horn lower, and more in phase with the 825B low-frequency horn, so you don’t have to be 20 foot away to hear both drivers blend together and sing as one. But it is susceptible to being easy knocked off the cabinet if careless.”

Altec 1005B horns & 288C drivers.

Altec 1005B horns & 288C drivers.

Gary’s is a 3-point mounting system where the horn rests on top of the 825B. Ideally, the diaphragm of the 288C Alnico compression driver should line up with the 515B Alnico low-frequency driver for best integration of the high & low-frequencies.

Jeff's A5 VOTTs without grills.

Jeff’s A5 VOTTs without grills.

So that’s it. When you put all the pieces together you get a classic Altec-Lansing A5 Voice of the Theatre loudspeaker system.

Please join me as the Altec A5 VOTT Project proceeds, and we endeavor to get the best performance possible out of this important vintage design.

 Posted by at 7:03 pm

  18 Responses to “Gary Fischer’s A5 ‘Voice of the Theatre’ Restoration Part 3: the 288C, 1005B, and 515B”

  1. Thanks for trailblazing this project. Im following it with great interest.

    I know its early days, but how would you rank the bass quality of your a5, maestro and tannoys, respectively?

    The reason for asking is that I recently heard a heavily modified altec a5 system. Midrange and treble were top notch (detailed and sweet) but I was underwhelmed by the bass. Too little of it and none of that upper bass slam that Ive experienced (and
    crave) in other horn loaded system (oma, danley, funktion one).

    thx

    Jesper

    • Hi Jesper,

      I can’t really answer your question yet. The A5 VOTTs are a work in progress, and the Stokowski VOTTs are in a different room, so I haven’t been able to compare them.

      The bass on my Duelund-ized WRSEs is deep, taut, powerful, and will rattle your ribcage when called on.

      I doubt either of my VOTTs will ever be able to match the WRSEs in the low frequencies, but the verdict is still out until we build some simpatico crossovers for the A5 (and maybe the S-VOTTs).

      While the bass of the VOTTs isn’t as stygian as the WRSEs, what is there is really very nice. I’ll report on what happens as we proceed.

      Thanks for stopping by!

      Best,

      Jeff

  2. amazing build and weight on those compression drivers; no wonder these Altec models have lasted so long, even after all the play they got in theaters!

    Enjoying your Altec story

    • Built like the proverbial tank, George. I’ll be glad to see you back this way for a little listening session. Man, it must be chilly in Mongolia right now! Brrr!

      Cheers,

      Jeff

  3. Who’d have thunk that these monsters built for large theaters could work in a home environment, let alone sound great? Gary did an amazing job and I’ll be watching this project closely as I just HAVE to have a pair of Altec’s this year! It’s almost comical…..I invested quite a bit this year getting new speakers ( Tekton Enzo’s), pre amp ( Odyssey Candela), amps (Odyssey Kismet Monoblocks and DAC (Schiit Yggdrassil) and probably would have been very happy for years with it. Now I find myself NEEDING the Altec VOTTS, a McIntosh MX 110 and MC 240. If only I had come to this revelation a few months ago I’d already have them! I guess that’s the fun of this audio journey. I picked up a little vintage Magnavox 9304 tube amp from an old console unit and I’m in love with the vintage tube sound…..I just need more power, hence the McIntosh MC 240 in my future. Isn’t this just too much fun? 🙂

    • I know just what you mean, Tom. I always thought my buddy Stephaen’s Altec 604 speakers sounded great, but I never really thought about Altec’s for myself. To be honest, I just didn’t know how to go about making it happen.

      That’s when I came across Gary Fischer and decided to go for a classic pair of A5 VOTTs. Then I ran across the Stokowski VOTTs. I have an embarrassment of VOTT riches right now, and I’m hooked!

      It really is a ton of fun!

      Cheers,

      Jeff

  4. Hi Jeff
    Just stumbled across your blog this week, and what a great blog! VOTTs, tube audio, bikes, deep dish pizzas, and guitars, what more could a guy ask for:)
    Cheers
    Gustavo

  5. ummmm, a few cold beers with that Gustavo
    LOL

  6. Hi,
    I have the same Speakers, on construction
    The guy who had them, put a tweeter on them. Are they necessary?
    I miss the crossover, any idea where I can find a pair?

    • Hi Fabien,

      Nice speakers! 🙂

      I like the A5’s and A7’s better without an added super-tweeter, I think they sound more natural and musical as a two-way. I’d unhook the super-tweeters and listen without them and see what you think.

      I think the best crossovers for A5’s and A7’s are those designed according to the Hiraga crossover circuit. If you don’t feel like building crossovers yourself, Pete Riggle Audio Engineering can build you some very nice sounding crossovers at an affordable price that will help you get the best out of your A5’s.

      Let me know how your A5’s work out!

      Kind regards,

      Jeff

  7. Hi Jeff,
    One my friend replaced HF diaphragms with new aluminum diaphragms from Great Plains Audio in his A7.
    He didn’t like a sound and after one year (or even more) he replaced these diaphragms to old (that where inside these HF drivers before). He was shocked how old diaphragms sounded better in term of tone compared to Great Plains Audio diaphragms!
    Regards,
    Alex.

    • Hi Alex,

      The original Altec HF diaphragms in their compression drivers seem to be pretty robust and long lasting. The fifty-something year old diaphragms in my A7’s Altec 804A 16-Ohm compression drivers sound great!

      Gary Fischer replaced the diaphragms in my A5’s 288C compression drivers with those from GPA when he did the restoration, and they do sound very nice, although I didn’t get to hear the originals, so can’t comment on the differences.

      I would suggest that leaving the original Altec diaphragms alone if they’re working properly is probably a good idea. They were designed to operate for a very long time in professional applications, and chances are for home listening applications they’ll last as long as the listener does.

      Best,

      Jeff

  8. How does it compare to Tannoy SEs

  9. Changing that original diaphram changed the sound originally meant for that driver. 24 ohms

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