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 Post subject: Realistic Optimus 1 and Opt. 5 Speakers--Great Finds
PostPosted: May Fri 08, 2015 5:35 am 
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Location: Central PA 16801
this nice pair of speakers opened my trunk and hopped themselves in it for 20 bucks. i tried to fight them off to no avail, but it did not work.

i have always liked better realistic/radio shack line of speakers from the 70's and 80's.

they are the optimus 1b with a 10 inch duped surround woofer and two tweeters. the tweeters have a 12db/oct crossover with a coil and a 33 mfd cap. i have not done any calculations but i would guess that they are crossed over pretty low. the woof is heavy with a thick basket. it is wired wide open to the terminals with no coil.

they are very similar to the later Nova 7b. i also read that they are compared up with the KLH 5 or 6 of which i have no first-hand experience.

what i like about these is (like the other Nova series speakers that i have) they are very smooth and natural sounding.

the highs are very clean and so is the bass. nothing is harsh or boomy about the 1B. the best way i can describe these speakers (and the other Nova series) is that they are absolutely NOT tiring on the ears. one can listen to them for long periods of time at an increased volume without the ears saying "enough".

the only drawback is that they (like the other Nova's) are perhaps a bit less sensitive than average and do like some power to make them kick. they run and perform very well on a 20-40 watt receiver of the era, but one would certainly not get their full punch with anything less than 15 watts. a couple vintage 10 watt bench amps that i have here just won't cut it.

sometime this summer, i'll lightly sand the cabinets, give a nice coat of stain/rejuvinator, and perhaps a top coat.

they are nice speakers. they certainly won't do what a mach one, mach two, mach three, pioneer cs, or wharfedale w70 will do, but for a mid-sized system, they are great.

if you see a pair at the local flea, gw, or sa, they are worth a pickup and a few 33mfd caps.

i'd pay 75 or less if i saw another pair.

steve


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Last edited by Dutch Rabbit on May Wed 20, 2015 8:21 pm, edited 3 times in total.
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 Post subject: Re: Optimus 1B Speakers
PostPosted: May Sat 09, 2015 5:24 am 
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Joined: Jan Tue 27, 2015 12:41 am
Posts: 33
Location: USA
Nice find!
I'm a fan of old realistic stereo equipment myself :mrgreen: , and understand your satisfaction with these speakers; though I don't have these exact ones. One note about freshening up the cabinets; like most realistic speakers, they are oiled (see link below), so if you want to keep the finish original, stain/top coat isn't what they originally had. Though you can do whatever you like best. I like using boiled linseed oil.
Enjoy those fabulous speakers! :P

http://www.radioshackcatalogs.com/html/1974/h025.html


Note: they may be listed in other years catalogs as well


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 Post subject: Re: Optimus 1B Speakers
PostPosted: May Sat 09, 2015 6:33 am 
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wow. i see that the ad also says "no booming" as i do.

i believe these will clean up nicely with some very fine sanding and some of the oil-style rejuvination fluid.

they are incredibly easy and smooth on the ears.

as far as i am concerned, Realistic and Optimus speakers were the best kept secret around. these are much bigger than they appear in the pictures and weigh a good bit too.

radio shack's "nova" line really began to decrease in quality after the last good grand-daddy Nova, the Nova 10 with the passive radiator, finished up in the early 80's. the nova's after that all used the same cheap woofer and cone tweeter. these weren't impressive at all.

one thing for RS audio equip, they had good stuff. the catch was that one had to buy from the top tier to the high-middle tier to get the good stuff in receivers, speakers, turntables, etc. once a person started in the low-middle and cheaper levels of equip, that's when the junk started.

in about 1988 when they introduced the black faced receivers, that's when the real garbage started, whether you bought the top line or not.

the STA-2700 top dog receiver certainly is NOT built an-y-thing like its earlier brothers, the 2600 and 2500. i've repaired lots of all these models and there is no comparison in build quality once the black-faced stuff came along. it all was junk no matter what you paid.

steve

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 Post subject: Re: Optimus 1B Speakers
PostPosted: May Sat 09, 2015 1:48 pm 
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Agreed, some of the mid to upper Tier RS can be really nice.

I'm using a pair of these driven by a Sherwood S5500II (7868) while I have been working on a 3,000 sq ft building.

http://www.ebay.com/itm/Vintage-Realist ... 1e9e09a225

The Sherwood does okay with them, and I been known to crank it up, but they are extremely power hungry.


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 Post subject: Re: Optimus 1B Speakers
PostPosted: May Sat 09, 2015 2:47 pm 
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Location: New Hampshire U.S.A.
Radio Shack corporate buyers made some very good manufacturer choices back in the day (the venerable 1970's in particular). My STA-250 receiver is still an almost daily "driver" I got new on my 16th birthday back in 1974. It was built by Sylvania U.S.A. It's built like a tank, not a piece of plastic on it anywhere; glass dial plate, solid aluminum knobs & switch buttons, cast aluminum chromed front bezel, solid wood cabinet, all semi-conductors socketed, etc. It was noted for its superb FM tuner performance. I had to fix it 2 times, once due to a nearby lightning/surge hit which took out about 10 transistors and once for a shorted FWB rectifier diode. I guess the "sucky '70's" weren't so bad after all in certain ways.

https://www.google.com/search?q=realist ... B768%3B576

Tom (PK)


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 Post subject: Re: Optimus 1B Speakers
PostPosted: May Mon 11, 2015 7:24 pm 
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Location: Minnesota
Quit it you guys. The word will get out that vintage RS stuff is not junk.

My 1972 STA180 is pretty amazing. Can hold it's head with anything I have. Weighs a ton too. A lot of older RS stuff was made by Hitachi or Foster. Foster was good enough to have McIntosh select them to build their Stereotech line. Some of the older tube stuff was HK.


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 Post subject: Re: Optimus 1B Speakers
PostPosted: May Thu 14, 2015 2:50 pm 
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Calculate the crossover frequency then see what capacitor and coil is needed for the woofer to make it cross over at the same or close to the same tweeter crossover frequency and you may notice a nice improvement in the sound.

Also for the cabinets if the finish is not water based you could try some Kramer's Best http://www.kramerize.com/


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 Post subject: Re: Optimus 1B Speakers
PostPosted: May Thu 14, 2015 11:42 pm 
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so i'm installing new capacitors in them today.

as i ran the numbers in the calculator. the second order crossover for an 8 ohm load with a 33 uf cap and a 2.0 mH coil on the tweet yields a crossover frequency around 500 hz.

although these are two 16 ohm tweeters in parallel for the 8 ohm load, my question is:

why oh why would they cross these over so low at 500 hz ?

strange.

steve

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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Fri 15, 2015 12:43 am 
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They are mid/tweeters.


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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Fri 15, 2015 1:12 am 
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i figured as much but that's kind of low. i would have guessed the woof would have taken care of those freqs since it is wide open and the tweets would have hit at the lowest, 1K.

i *should* break out the freqquency generator and all the equip to analyze....but i don't believe that's going to happen 8) .

i'm very happy with their sound, however RS configured it...

steve

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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Fri 15, 2015 1:24 am 
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From what I read the Radio Shack woofers of that time had either a bump or continual rise in output somewhere above 500Hz.


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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Fri 15, 2015 1:45 am 
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i'm listening to them now with some oakridge boys, winger, dean martin, and steve windwood, and 7k of others pinging off the computer's playlist.

i can't believe how smooth, easy on the ears, but yet, well defined these are.

i'm a lucky guy for this find at 20 buckeroos.

they are the best large bookshelf/small floor speaker of this size that i ever heard ; at this stage of the game, it takes a lot to impress me these days.,.,....

steve

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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Fri 15, 2015 11:38 am 
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Very nice.


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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Fri 15, 2015 4:41 pm 
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I also have those speakers and really like the sound. A friend gave them to me for free! One of the mids has an open voice coil, I tried sending it in to a speaker repair place. They can't repair it. But being deaf in the mids anyway it still sounds good to me!


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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Fri 15, 2015 8:13 pm 
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Location: Vincennes Indiana
I picked up a similar realistic speaker years ago on closeout - $9, it was an orphan for some reason. Very similar to yours depicted, but mine has a tuned port in place of one of the tweeters. It's my goto speaker for ambc and swbc listening, I concur with your evaluation of their performance even if a radioshack product.

Some kindhearted soul gave me two of the rs minimus speakers, these are outstanding for voice frequency work and take up so little space for the audio they reproduce. I've not checked the crossover crct for the big speaker but have seen various mods for the minimus types online.


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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Fri 15, 2015 8:24 pm 
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hello steve,

you should go to ebay and find one of those infamous optimus or nova tweeters--the 16 ohm version. this will allow the power to be divided evenly between both tweeters since they are in parallel. the working tweeter will be much happier with its working counterpart.

they are often listed on the bay.

do an ebay search for:

optimus tweeter

nova tweeter

radio shack tweeter

realistic tweeter

you could perhaps put a classified ad on this forum.

there are some tweets on the bay now, but they are the 4 and 8 ohm version.

i strongly suggest that you replace the defective 16 ohm tweeter to keep the good tweeter happy. since these are crossed over so low, they need to be in a pair to share the power and yield the proper crossover frequency.

Minimus 7: i've exclusively used them for icom and kenwood communications receivers from the 80's. they are absolutely fantastic for that purpose, a small hi-fi system, and surround sound systems. they are just a great all-round speaker.

steve

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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Sun 17, 2015 5:11 am 
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""Minimus 7: i've exclusively used them for icom and kenwood communications receivers from the 80's. they are absolutely fantastic for that purpose, a small hi-fi system, and surround sound systems. they are just a great all-round speaker.

steve""


I use my 7's (wood cabinet/) for my ham rigs as external speakers too. I disconnected the tweeters as they just added noise really as I am mostly doing sideband. There is no low pass on the 4" and it goes high enough for voice.



E
T

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T

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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Sun 17, 2015 11:34 pm 
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Hi Steve,

I'll follow any thread on RS gear and speakers. I'm not a collector per se, but they seem to find me and follow me home.

I bought a pair of Nova 7b at a thrift, $40 for the pair, that's 20 more than you paid, but I see they're originally priced $20 higher than the Optimus 1 so I didn't do too bad on 'em! ;) They have a fancy plastic fretwork grille, and a bit more detail in the cabinet, that may be the principal difference between them and the Optimus 1.

They have the identical tweeters. I recall reading these have an oil-filled voicecoil. To my ears they have the "East Coast" sound, that is a bit muted on top but with a good, solid bottom end. The woofers are a bit different in appearance, mine have a black butyl rubber surround that, like yours, does not rot as foam will. A big plus, and they're very hefty and well-made to boot.

The tweeters I am not very fond of. RS used the identical units in many, many of their other speakers. I think the oil slows transient response and cone tweeters just lack clarity to my ears. I replaced them with some nicer Yamaha carbon-fiber dome tweeters and I like that sound much better. No doubt it's due in part to my battered eardrums lacking more than a little high-end response, but with the domes, I run the amp nearly flat on the treble. I don't recall modifying the crossovers much if at all. I still have the original tweeters and "conehead" baffle if you want to double-up in your Optimus 1 system, har har!

I have a dumpster rescued Optimus STA-3250 receiver. An honest 100wpc unit that doesn't sound too bad after repair. The miniscule "rear channel surround" amp had smoked, the previous owner hit it good and square with a fire extinguisher and tossed it. All I did was disable that board and rewired the "rear" speaker terminals as a second pair. I just wish he woulda tossed the remote control for it in the garbage along with the receiver! :lol:

I also have an STA-225, a nice mid-tier receiver with 60wpc. Also free to me, it's a lightning strike survivor after a fairly simple fix for a couple blown parts in the driver stage. Very lucky.

I have a single Minimus 7 all neglected and a pair of Minimus 18 I use a lot after a rebuild. Did a lot of selecting among several 4" woofers and added a tweeter which the original did not have.

In 1973, I bought one of their 4-channel receivers, maybe one notch above the lowest price. I did enjoy the sound, but the 7wpc rating was too anemic to go much above a casual listening level so I traded it off after a few months when I lucked onto a Heathkit AA-15. Wish I still had both units now, but no room or need for more gear.

-Ed


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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Mon 18, 2015 12:33 am 
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hello ed,

funny you say that. i have a set of 7b also and absolutely love them. they are the later version of the optimus 1 speakers pictured in this thread, only with a different woof and the lattice grill.

today i found a pair of optimus 5 speakers. they are the big 4 way version of the opt 1, the next step up.

the speaker gods are shining upon me.

i'll post pics this week.

i recommend changing the crossover capacitors, that will improve the sound of the original tweets. for me, i absolutely love the sound of those cone tweeters/mids as pictured in this thread. they are so easy on the ears.

i have not fired up the today's acquired optimus 5 speakers but they have a 12" duped inverted surround woof, two midranges, and one tweeter. they also have Lpad controls for the mids and tweets.

radio shack speakers from the 70's and 80's, mid tier to top line were the best kept secret in town. i've owned pioneers criterions, sansui, yamaha, fisher, advent, cerwin, and many other brands over the years. my ears like vintage wharfedale and 70's-80's realistic.

steve

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 Post subject: Re: Realistic Optimus 1 Speakers--Crossed Over So Low ?
PostPosted: May Mon 18, 2015 5:05 pm 
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Looks like there is room to add a dome tweeter to the speaker for those who don't like the cone tweeters.


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