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Stephens Tru-Sonic 15" woofers in Ampex Signature

Discussion in 'Tube Audio' started by Omegaman, Sep 18, 2018.

  1. Omegaman

    Omegaman Ultra Super Member

    Messages:
    2,878
    Location:
    Scottsdale, Arizona
    SPEAKERS REASSEMBLED AND CLOSED UP

    Awesome, thanks for those pictures of the tape drawer. That will help
    Tape deck will be the easiest install

    That cover plate is what I will have to fashion
    [​IMG]

    I got both sides recapped, the nasty insulation back in place and the backs buttoned up

    I had to lay the console face down (drawers removed) to put the insulation back in correctly

    I flipped the one back panel, counter-sunk the screws and stained both sides to match-ish

    Nice and tight mitre fit now
    DSC07814.JPG
    I tested the speakers with my Marantz and used a cardboard tube to verify each driver operating. They all work
    DSC07810.JPG

    I also wired the on/off GE46 lamp in the front mid bottom so there was wire to one amp
    DSC07816.JPG
     
    Last edited: Sep 30, 2018
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  2. Leland47

    Leland47 AK Subscriber Subscriber

    Messages:
    2,511
    I'll take some pics of my Tape Recorder drawer tomorrow and post em...

    Just an idea....Get rid of one drawer and space out the mounting of the Tuner and Preamp so they are more prominent. Those to me are the gems of the console...and giving them more room to shine would look great IMO.

    On my console they looked very squeezed in, sitting right on top of one another...with no space in between.

    Since the console doesn't have an opening top....you've got all that real estate on top to put a Turntable....or ?

    Edited: Another possibility would be to mount the RTR vertically and see if that would also allow enough space to mount the Tuner and Preamp with a little more room in between them...

    I know....not original, but just some of my thoughts...
     
    Last edited: Sep 30, 2018
  3. Omegaman

    Omegaman Ultra Super Member

    Messages:
    2,878
    Location:
    Scottsdale, Arizona
    TESTING THE RECAPPED SPEAKERS

    Just testing the 16 ohm Speakers out with a MAC 1500 (Everybody wants a selfie)

    Really sounds nice and clean and open
    DSC07845.JPG

    Ampex pre-amp
    DSC07843.JPG

    Scott 299c
    DSC07853.JPG

    Polarity issue:
    So I'm playing these speakers on all my different gear
    and I'm NOT really overwhelmed
    where is the thunderous 15" bass?
    A little brittle on the top end

    I'm thinking to let the new caps work out (not really a believer in cap burn in, but hey)

    I know the woofers are moving and producing sound
    I go over the crossover pictures of before and after
    Nothing obvious
    I'm ready to pull the drivers completely out

    Then I think to try reversing the polarity
    BIG DIFFERENCE, the bass is there, everything is good to go now

    I guess the connections make a difference when using coils in the crossover?

    Does this sound reasonable?
     
    Last edited: Oct 8, 2018
  4. KlipschFan61

    KlipschFan61 Smooth Jazzer

    Messages:
    863
    Location:
    Manchester, NH
  5. Omegaman

    Omegaman Ultra Super Member

    Messages:
    2,878
    Location:
    Scottsdale, Arizona
    Here is a picture of the back of one grill with the cut out for the woofer
    Each side is "handed" left and right
    These grills do not have metal cages

    DSC07897.JPG
     
    Last edited: Oct 8, 2018
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  6. Omegaman

    Omegaman Ultra Super Member

    Messages:
    2,878
    Location:
    Scottsdale, Arizona
    I picked up the glass top
    DSC07900.JPG
    DSC07901.JPG
    DSC07902.JPG
    DSC07904.JPG

    Its like 800 coats of clear
     
    Last edited: Oct 9, 2018
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  7. CoastinHome

    CoastinHome Member

    Messages:
    80
    Location:
    San Diego
    Looks great Omegaman!

    Mine came with a glass top -- which obviously had been on it since the day it was delivered in 1961.

    In your picture it looks like there is a significant gap between the glass and the top of the cabinet. I learned that what is used is in this application is thin plastic spacers which are specifically intended for this application. I lost a couple when the cabinet was moved -- and was very glad that I was able to find the identical item on that auction site. After placing the glass I used a thin steel ruler to push the (non-adhesive) spacers back into their original locations -- where the wood was slightly darkened in the original six locations.

    Glass Top Spacers.jpg

    Here's what the inside and outside of my cabinet grilles look like. They are all the same on 3 cabinets. Makes me wonder if yours are original. It looks like your cloth has a much denser weave. These are more like thin and soft burlap.

    I was successful at cleaning one set by scrubbing partially dissolved powdered Oxi-Clean into the cloth and leaving it on the cloth until it dried. The next day I rinsed it off and let the grilles dry quickly in the hot sun to keep the grill metal from rusting. No such luck with another pair which are water stained from wicking up water from a garage floor after a previous owner had them separated from the cabinet for a period of time. I may eventually dye them.

    IMG_3717.JPG

    IMG_3716.JPG

    As far as having to change the polarity of your crossover connections to get your woofers to woof in unison:

    You might want to confirm that you changed the polarity of the correct woofer. If you reverse the wrong woofer in the process of reversing connections to get the woofers in phase, the woofers will both be out of phase with the midrange drivers. If that's the case you will have the woofers and midranges acoustically canceling each other near their crossover frequencies and will end up with an anomaly in the midrange.

    I thought it would be helpful to share this eBay picture of a pair of crossovers from a 1961 Signature 8202-2, but after studying the picture I notice that the polarity is reversed to the woofer on one of these.

    Crossover from Ampex Signature 8202 Console 1.jpg


    My guess is that the woofer polarity is incorrect on this one (the connections with the yellow jumper between them. The jumper is for connecting the pair of 12 inch drivers in series):
    Crossover from Ampex Signature 8202 Console 2.jpg

    ...and is correct on this one:
    Crossover from Ampex Signature 8202 Console 4.jpg

    Hope this helps!

    Bob
     
  8. CoastinHome

    CoastinHome Member

    Messages:
    80
    Location:
    San Diego
    Did you happen to sketch a schematic of the crossover when in the process of replacing capacitors?
     
  9. Dswankey

    Dswankey Super Member

    Messages:
    3,683
    @Omegaman

    Looking good so far and @CoastinHome has been quite the font of knowledge. Good job guys!!
     
  10. Omegaman

    Omegaman Ultra Super Member

    Messages:
    2,878
    Location:
    Scottsdale, Arizona
    Thanks for all the replies

    I did not sketch a schematic of the crossover, but I used tried and true techniques for replacing the caps one leg at a time

    I'll get those plastic disks. I just used what I had on hand. Good idea

    After reviewing the polarity throughout the crossover circuit, I have high confidence it is wired correctly...now

    Odd things about this console:
    - All the connections on the Stephens crossover are soldered whereas the other crossovers I have seen use connectors
    - There are NO QA stamps anywhere
    - I see no evidence that any model plate was attached to the back
    - There are no tube layout stickers
    - I see NO evidence that any pre-amp or tuner mounting hardware screws were installed
     
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  11. CoastinHome

    CoastinHome Member

    Messages:
    80
    Location:
    San Diego
    Re: Odd things about this console

    It is an interesting variant. After posting I looked back over the earlier pictures you posted of your crossover -- and noticed that it has a simpler crossover than the production units I've seen. These generally use three inductors (though I have seen one with four).

    Your console has enough differences from what I have encountered that I have continued to wonder whether it was an early prototype / demonstration unit.

    In addition to what you listed above I noticed that several other of these differences amount to construction techniques which would've evolved as the design went into production.

    - The use of (green-yellow) vinyl-harnessed speaker wire pairs. The many Ampex console interiors photos I have encountered all use non-sleeved twisted-pair black/green wiring to all drivers - with green as the (+) connection.The sleeved wires would add to the production cost - both in materials and in the additional labor of cutting back the sleeves or feeding wires through the sleeves. (Perhaps the polarity on yours has green as (-) and yellow as the (+) connection?)

    - The gauze which keeps the cotton candy out of the back of the drivers is taped to the driver frames. I haven't paid attention to other examples but on a 1958 unit here the gauze is attached to the inside of the baffle plate. Ampex stapled a sliver of the 12" cardboard surround from the woofer mounting face to the back side of the baffle plate to assist the staples in holding the gauze in place. That would improve production efficiency.

    - It doesn't appear that a handle was originally installed on the front of the baffle plates. That installation could greatly improve production efficiency.

    - The baffle plates were countersunk after the baffles were painted. At some point they would've realized that having the baffle plates pre-drilled was a better idea.

    So allowing for the possibility that this is a proof-of-concept unit, I have to wonder whether the custom faceplate for the preamp/tuner (which you received the console with) was actually part of a prototype.

    Perhaps your console had the Ampex combined tuner/preamp installed at one time? That could explain the lack of holes for preamp/tuner mounts as this could have been mounted to a platform which stands on the blocks for the drawer slides.


    Ampex Integrated Preamplifier Tuner 1.jpg

    Ampex Integrated Preamplifier Tuner 2.jpg
     

     

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  12. CoastinHome

    CoastinHome Member

    Messages:
    80
    Location:
    San Diego
    Getting slightly off-topic but here's another oddity found on eBay a while back --- a gold faced 503 tuner.

    Ampex 502 Gold Face Tuner eBay 1.jpg
     
  13. Omegaman

    Omegaman Ultra Super Member

    Messages:
    2,878
    Location:
    Scottsdale, Arizona
    Thanks for all that


    The combo pre-amp/tuner would not have fit the cutout the console came with

    The cut out is much too wide and not tall enough to accommodate the combo unit
    It appeared to accommodate a standard type receiver in size

    The install of the receiver bezel did not appear to be factory. rather shoddy

    The added bezel wood did not match

    I added the speaker wire from the crossover to the amp. Wires internal are green/black
    Oh, I misunderstood. Yes, the internal wiring is sheathed. That is different

    The console was owned by a person in the TV broadcast business in Phoenix. They claimed he bought it in the 50's
    They didn't know what was in it when it worked

    I have the crossovers from the original 7208 console with three INDUCTORS. Maybe I'll swap them out and listen to them with the Tru-sonics


    I did get those vinyl pads for the glass top like suggested. They are made from some of the same stuff used in the Space Shuttle. That's why they are so expensive the guy at ACE hardware said
    DSC07908.JPG
     
    Last edited: Oct 11, 2018
  14. matt e.

    matt e. Active Member

    Messages:
    162
    Location:
    Chicagoland
    Here's a 1958 Ampex Audio Operation Manual. 36 pages covering (I think) all of the Ampex Audio consoles for '58.
    1958 Ampex Audio Op Manual No.842

    Not to hijack the thread, Got the manual this morning as part of an Ampex console purchase. Lots of work to do to get this thing moved. Weighs a ton. It is in the 3 door parquet walnut cabinet with glass top and appears to be a Model 8002. Have to get busy and make room for it before my wife finds out.

    Matt
     
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  15. Omegaman

    Omegaman Ultra Super Member

    Messages:
    2,878
    Location:
    Scottsdale, Arizona
    Awesome post pictures or start a thread

    I would be very interested to compare our consoles

    And in regards to moving Ampex consoles, I find it best to use 4 people minimum

    and get new casters for it if it needs it
     
    Last edited: Oct 12, 2018
  16. matt e.

    matt e. Active Member

    Messages:
    162
    Location:
    Chicagoland
    I have to get it down my basement stairs so everything that comes apart is going into separate boxes. I make custom sized dollies by bolting a piece of 3/4 sheet plywood to a pair of small harbor freight dollies. It's fast, cheap, and I can move the console around in my basement when needed without breaking legs. Also gets it off the floor about 6 inches just in case of water. Every basement I've ever had one time or another gets wet from something.
     

     

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  17. Dswankey

    Dswankey Super Member

    Messages:
    3,683
    Thanks for sharing!! great source of information and as @Omegaman suggested pictures would be nice.
     
  18. matt e.

    matt e. Active Member

    Messages:
    162
    Location:
    Chicagoland
    No pictures today, but will take plenty tomorrow. A couple pics from the sale can be found here:
    https://www.estatesales.net/IL/Mount-Prospect/60056/2019423
    If it's not an 8002 I will be disappointed. Looks like the glass top was standard. The manual shows an 8012 coming with optional turntable vs record changer. Anyone know what model of turntable was supplied?
     
    Last edited: Oct 11, 2018
  19. matt e.

    matt e. Active Member

    Messages:
    162
    Location:
    Chicagoland
  20. CoastinHome

    CoastinHome Member

    Messages:
    80
    Location:
    San Diego
    Nice score, Matt!

    It looks like a 1959 or so Model 8002 -- which should have a Garrard RC88 changer according to your manual. For another hundred dollars the 8012 model had a Garrard 301.

    Thank you for posting the clear scan of your owners manual. I have the same manual with the same part number but mine shows a different feedback loop for the 30W amplifier...without any other indication that either manual is a revision.

    Your manual certainly has an error in how the additional feedback components have been drawn on the schematic: As drawn it shows a short across the three feedback components. The wire shown from the second area of the output transformer near the label "GREEN" doesn't belong there. You may find that R20 is 56K rather than 33K...according to my SAMS manual. Ampex might have revised the feedback loop to accommodate a change in output transformer etc. Let us know what you find when you get there.

    ampex_audio_1958_op_man.jpg

    Ampex-Stereo-Systems-1958-Owners-Manual.jpg

    Thanks for posting the Signature store ads. I have searched extensively online for the most complete documentation I can put together for the Signature. I've found a couple of similar ads but had not seen either of these. Great to see some info on when the driver configuration was revised.

    Very interested in what all docs you got with your Signature!

    Ampex Signature Sunset Magazine September - November 1960.jpg
     

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