Stephens Tru-Sonic 15" woofers in Ampex Signature

[Omegaman]

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

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

I tested the speakers with my Marantz and used a cardboard tube to verify each driver operating. They all work


I also wired the on/off GE46 lamp in the front mid bottom so there was wire to one amp

 

[Leland47]

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...

 

[Omegaman]

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


Ampex pre-amp


Scott 299c


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?

 

[KlipschFan61]

I was browsing the local Craigs and ran upon this lovely thing https://boston.craigslist.org/gbs/ele/d/vintage-stephens-tru-sonic-15/6713252598.html
which in turn drew me to this topic.

What a lovely console. Grandfather had a Magnavox when I was a sprite and I remember its sound vividly. Nicely done!

 

[Omegaman]

re: <<The screens have cut outs for the woofer so they only fit on one way>>

Oh... then the screens are different as well. (Screens = the metal frames that the grill cloth is wrapped around, right?). Those that I've seen are symmetrical open mesh -- they are interchangeable between left and right and can be swapped top for bottom as well. Interested in adding pictures of this variation to my "recognition guide".

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

 

[Omegaman]

I picked up the glass top





Its like 800 coats of clear

 

[CoastinHome]

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.



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.





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.




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):


...and is correct on this one:


Hope this helps!

Bob

 

[CoastinHome]

Did you happen to sketch a schematic of the crossover when in the process of replacing capacitors?

 

[Dswankey]

@Omegaman

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

 

[Omegaman]

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

 

[CoastinHome]

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.

 

[CoastinHome]

Getting slightly off-topic but here's another oddity found on eBay a while back --- a gold faced 503 tuner.

 

[Omegaman]

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

 

[matt e.]

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

 

[Omegaman]

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

 

[matt e.]

yeah, post pictures or start a thread

very interested

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

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.

 

[Dswankey]

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

Matt

Thanks for sharing!! great source of information and as @Omegaman suggested pictures would be nice.

 

[matt e.]

Thanks for sharing!! great source of information and as @Omegaman suggested pictures would be nice.

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?

 

[matt e.]

Speaker changed from 4) 12" woofers to 2) 15" woofers and tweeter horns around 1960 best I can tell from ads.


http://indoorphin.com/radio/ampex/Nov1958_vs_Oct1960.jpg

 

[CoastinHome]

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.





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!