Realistic Optimus T-100 Speakers

[Francis55]

All,

I just picked up a pair of Realistic Optimus T-100 speakers for $20 . Hooked them up, tweeters seem dead. Just checking that I'm wiring them correctly. This is a dumb question, but does that silver barrel, across from the wire terminals, need to be hooked up at all? Just checking! See picture. That would require a third connection, so I thought maybe that's why tweeters are silent. More likely is that they are just dead and need to be replaced. If I'm replacing them, ideas for what would be a good substitute? Many thanks for any ideas you guys might have!

Francis

 

[hjames]

My guess is that some stereo systems used RCA cables to connect from the amp to the speakers. (generally cheaper systems)
Most better systems used zip cord or something similar to what you used.
There would not be a specific wire just for the tweeter, unless it was an obviously labelled "BiWire" system.
If the tweeters are not working, my first guess is someone blew them out.

I mean, if you got a pair of floor standers like this for $20, there may be a reason ...

 

[Lavane]

No. You can either use the screw terminals, or speaker wire with RCA jacks.
Many Realistic speakers had them. Are the foam woofer surrounds intact? I've seen them that have rotted. If the tweeters are dead, get the part number off the back of the magnet and troll Ebay for pulled, used replacements. Realistic used the same tweeters in various models. Just do a search for "realistic parts" etc., on Ebay and match the part numbers. If you don't see them, chances are they will pop up sooner or later. You can test the tweeters a few ways. Place a paper towel tube over the tweeter while it's playing. Can you here it, does it sound distorted, no sound at all? Or pull them and use an ohm meter to check impedance. You should get an ohm reading. Depending on whether it's 4 ohm or 8 ohm, you should get a reading around 3 to 8 ohms. The tweeter adjustment on the front under the grill, maybe it's turned to "low?

 

[Francis55]

My guess is that some stereo systems used RCA cables to connect from the amp to the speakers. (generally cheaper systems)
Most better systems used zip cord or something similar to what you used.
There would not be a specific wire just for the tweeter, unless it was an obviously labelled "BiWire" system.
If the tweeters are not working, my first guess is someone blew them out.

I mean, if you got a pair of floor standers like this for $20, there may be a reason ...

View attachment 2330416

Yes, got them from a local online auctioneer--I've gotten some insane deals this way, with speakers that are just brilliant, I've gotten a few clunkers, and then something like this, in between. Also note that the cabinets are very weathered--I'm going to oil them up to see if they can be brought back to life. And they were from a smoker's house, so the cloth covers are pretty rank. Now I'm caught betwixt and between--do I get replacement tweeters and hope they work, or do I cannibalize these guys and try to sell off the four drivers that work? Hmmm.... Many thanks for your insights!

 

[Francis55]

No. You can either use the screw terminals, or speaker wire with RCA jacks.
Many Realistic speakers had them. Are the foam woofer surrounds intact? I've seen them that have rotted. If the tweeters are dead, get the part number off the back of the magnet and troll Ebay for pulled, used replacements. Realistic used the same tweeters in various models. Just do a search for "realistic parts" etc., on Ebay and match the part numbers. If you don't see them, chances are they will pop up sooner or later. You can test the tweeters a few ways. Place a paper towel tube over the tweeter while it's playing. Can you here it, does it sound distorted, no sound at all? Or pull them and use an ohm meter to check impedance. You should get an ohm reading. Depending on whether it's 4 ohm or 8 ohm, you should get a reading around 3 to 8 ohms. The tweeter adjustment on the front under the grill, maybe it's turned to "low?

Great insights--yeah, knobs being turned to high does nothing. Ah, great, so that barrel terminal is to be used with an RCA jack instead of wire terminals, got it, thanks for that--so it's inconsequential, good to know. Great idea on looking for exact replacements by casting a wide net, I might do that. The surrounds seem to be those rubber ones that last forever. Ohm meter--too tricky for me! Thanks again, those are really good insights.

 

[Francis55]

No. You can either use the screw terminals, or speaker wire with RCA jacks.
Many Realistic speakers had them. Are the foam woofer surrounds intact? I've seen them that have rotted. If the tweeters are dead, get the part number off the back of the magnet and troll Ebay for pulled, used replacements. Realistic used the same tweeters in various models. Just do a search for "realistic parts" etc., on Ebay and match the part numbers. If you don't see them, chances are they will pop up sooner or later. You can test the tweeters a few ways. Place a paper towel tube over the tweeter while it's playing. Can you here it, does it sound distorted, no sound at all? Or pull them and use an ohm meter to check impedance. You should get an ohm reading. Depending on whether it's 4 ohm or 8 ohm, you should get a reading around 3 to 8 ohms. The tweeter adjustment on the front under the grill, maybe it's turned to "low?

.

See the picture posted above for some brilliant cabinets--sadly the ones I got look nothing like this! Super weathered and beat up.

 

[hjames]

I had gotten a pair of the T-120s, the next model up a year ago - replaced the rotting surrounds in the mids and woofers, and they played nicely -
but I couldn't sell them. So I gave them to a friend for the $50 I had in them for the surround kits, and he's is going to pass them on to a friend of his thats putting together a budget system.
Nothing wrong with the Optimus speakers when they are working.

 

[Francis55]

I had gotten a pair of the T-120s, the next model up a year ago - replaced the rotting surrounds in the mids and woofers, and they played nicely -
but I couldn't sell them. So I gave them to a friend for the $50 I had in them for the surround kits, and he's is going to pass them on to a friend of his thats putting together a budget system.
Nothing wrong with the Optimus speakers when they are working.
View attachment 2330421

Yes, exactly, I could invest in the replacement tweeters and still not be able to sell them--so either I cannibalize the other drivers to sell or I take the chance I might have to "eat" them when they're fully functional--I might try oiling the cabinets first, if they look good enough I might chance the replacement tweeters, figuring I can use them in the house later (if my spouse doesn't kill me).

 

[Lavane]

If you can't find original replacement tweeters, the cheap Goldwood paper cone tweeters that Parts Express sells would probably work. You would just need to know if the original is 4 or 8 ohm. It's probably printed on the back of the tweeter. I've tried the Goldwoods in a couple pairs of speakers with good results.
https://www.parts-express.com/Goldwood-GT-25-3-Cone-Tweeter-270-018

 

[faber12]

T-100 are very nice speakers, I would replace the caps with new electrolytic from Parts-Express. The tweeters can be tested by playing low volume audio directly to the driver.

The T-100 I had were equipped with a different sort of speaker foam that never seemed to deteriorate.

 

[kfa888]

I have (had?) T-100's. The drivers on these are very cheap all around. rubber surrounds on mine were cracking. Still have the woofers. I hated the sound of them even with all drivers working as they should minus the slightly cracking of the rubber. I replaced the woofers with Altec 8" alnico drivers and the tweeter with a EPI inverted dome. Sound fantastic now.

here is my thread on these. IMHO making them sound good with the very cheap stock components might be very hard.

https://audiokarma.org/forums/index.php?threads/ultra-rare-raltecepi-speakers.923829/#post-14081524

 

[Francis55]

T-100 are very nice speakers, I would replace the caps with new electrolytic from Parts-Express. The tweeters can be tested by playing low volume audio directly to the driver.

The T-100 I had were equipped with a different sort of speaker foam that never seemed to deteriorate.

Yes, I think they are some form of rubber, they will probably outlast me. I will need to Google "How to replace caps on a speaker." I'm somewhat handy, maybe I'll give this a try. Thanks!

 

[Francis55]

T-100 are very nice speakers, I would replace the caps with new electrolytic from Parts-Express. The tweeters can be tested by playing low volume audio directly to the driver.

The T-100 I had were equipped with a different sort of speaker foam that never seemed to deteriorate.

Interesting--so I can hook the speaker wires directly to the terminals on the tweeter? Didn't know that was possible.

 

[faber12]

Interesting--so I can hook the speaker wires directly to the terminals on the tweeter? Didn't know that was possible.

Yes, just be careful not to send much signal to them as they are delicate.

 

[crazy-in-az]

Interesting--so I can hook the speaker wires directly to the terminals on the tweeter? Didn't know that was possible.

Yup, this will at least tell you if the tweeter works. If it does, then there is either a short in the wiring somewhere, or the crossover cap needs to be replaced.

 

[Gnesen]

I just picked up a pair of the T-100s. The tweeters would cut out when the L-pads were turned to certain positions, which might cause one to think the tweeters were dead. Cleaning the L-pad pots with contact cleaner eliminated the drop-outs. I know it's been a while since this thread was started, but the OP might want to try doing that if the tweeters tested good.

The foam surrounds on mine are still good, but they were separating from the frame due to glue failure. For those curious, I took a few photos of the drivers and L-pad/crossover. Unfortunately, mine are missing the woofer trim pieces. I might fashion some.

A few observations:

1) the crossover consists of a single 4.7 uF cap across the L-pad. As I mentioned above, clean those L-pad pots!





2) the woofers are wired in parallel.



3) There is no choke on the crossover, so the woofers run wide open and have significant output up to ~10 kHz. I ran a 50 Hz tone while re-gluing the surrounds, but also did a non-scientific frequency sweep for the heck of it. They were still putting out plenty of sound at 10 kHz even though they are labeled "40 Hz - 3 kHz". Not much natural roll-off going on here! Here are a couple of photos of the woofer.





4) the tweeter is a simple paper cone. Nothing special, but not bad either. One of mine had a pushed in center, which I was able to pull out with a vacuum cleaner wand.

Before...


After vacuum...


Tweeter back...


5) As was common of RS speakers of this era, the cabs are very nicely finished. The backs are also veneered and, as previously noted, the speaker terminals are located on the bottom of the cabs. While the cabs are of substantial construction, they would probably benefit from some extra bracing. According to the serial numbers, mine were built in November 1977.



6) How do they sound? I haven't had a chance to listen very much, but they are pleasant sounding and somewhat laid back. I will probably put in new caps and report back later.

 

[onwardjames]

T-100 are very nice speakers, I would replace the caps with new electrolytic from Parts-Express. The tweeters can be tested by playing low volume audio directly to the driver.

The T-100 I had were equipped with a different sort of speaker foam that never seemed to deteriorate.

I really enjoyed a pair my friend had. Great all-around little speakers, nothing special, just pleasant.

Faber12's comments all the way, tho I would spring for some nice poly caps. It's what my friend Vegaman9 did.

 

[Gnesen]

I really enjoyed a pair my friend had. Great all-around little speakers, nothing special, just pleasant.

Faber12's comments all the way, tho I would spring for some nice poly caps. It's what my friend Vegaman9 did.

I agree with your take on the sound, but our definitions of "little" must be different. These are ~36" x 12" x 13". Not huge, but not little either, IMO. For what it's worth, my understanding is tower speakers weren't very common when these were first released.

 

[onwardjames]

I agree with your take on the sound, but our definitions of "little" must be different. These are ~36" x 12" x 13". Not huge, but not little either, IMO. For what it's worth, my understanding is tower speakers weren't very common when these were first released.

Well, yeah, that's true enough. I guess I meant their footprint, which is indeed small for a floor speaker.

I really enjoyed those little guys.

 

[Gnesen]

I just picked up a pair of the T-100s. The tweeters would cut out when the L-pads were turned to certain positions, which might cause one to think the tweeters were dead. Cleaning the L-pad pots with contact cleaner eliminated the drop-outs. I know it's been a while since this thread was started, but the OP might want to try doing that if the tweeters tested good.

The foam surrounds on mine are still good, but they were separating from the frame due to glue failure. For those curious, I took a few photos of the drivers and L-pad/crossover. Unfortunately, mine are missing the woofer trim pieces. I might fashion some.

A few observations:

1) the crossover consists of a single 4.7 uF cap across the L-pad. As I mentioned above, clean those L-pad pots!

View attachment 2346930

View attachment 2346932

2) the woofers are wired in parallel.

View attachment 2346936

3) There is no choke on the crossover, so the woofers run wide open and have significant output up to ~10 kHz. I ran a 50 Hz tone while re-gluing the surrounds, but also did a non-scientific frequency sweep for the heck of it. They were still putting out plenty of sound at 10 kHz even though they are labeled "40 Hz - 3 kHz". Not much natural roll-off going on here! Here are a couple of photos of the woofer.

View attachment 2346939

View attachment 2346938

4) the tweeter is a simple paper cone. Nothing special, but not bad either. One of mine had a pushed in center, which I was able to pull out with a vacuum cleaner wand.

Before...
View attachment 2346947

After vacuum...
View attachment 2346945

Tweeter back...
View attachment 2346946

5) As was common of RS speakers of this era, the cabs are very nicely finished. The backs are also veneered and, as previously noted, the speaker terminals are located on the bottom of the cabs. While the cabs are of substantial construction, they would probably benefit from some extra bracing. According to the serial numbers, mine were built in November 1977.

View attachment 2346959 View attachment 2346960

6) How do they sound? I haven't had a chance to listen very much, but they are pleasant sounding and somewhat laid back. I will probably put in new caps and report back later.

I replaced the old electrolytic capacitors with new 4.7 uF Dayton polys (1%) this weekend. I had to mount the new larger caps on the back of the L-pad instead of on the side, otherwise the housing wouldn’t have fit back in the hole. The old caps measured 5.2 uF on my tester, so either they drifted over time or were a little high to begin with (but probably still within tolerance at the time).

Not sure if I hear a big difference with the new caps, but these are quite pleasant sounding speakers. Plenty of bass for my liking and the highs are nice and smooth. Unsolicited, my wife also said she likes how these look, so that’s a plus. She usually just ignores my hobby, at least outwardly.