View Full Version : Realistic Optimus-1 (KLH-6 copy)


HTHMAN
10-14-2010, 03:53 PM
I used to own the Realistic Optimus 5B speakers that were a blatant KLH-5 copy. Those were great sounding speakers, but sold them because they did not fit into my wife's decor.

I was on Craigslist and saw a pair of Optimus-1 speakers listed in town for $10. I could not get there fast enough. Those were the first and one of the best of the good Radio Shack speakers. Their ad from about 1970 said that they copied the sound of their favorite $134 speaker at 30% less cost. They would not mention the brand, but the excellent KLH-6 by coincidence was selling for $134. Both were acoustic suspension with a 10" woofer (that look very similar) with a 2-way crossover. The difference was that KLH used 1 tweeter and Radio Shack used two. The speaker uses a 3-way switch to adjust the tweeters for normal, low and high levels.

I cleaned them up and hooked them up today. Wow!!! These are great sounding speakers. This is without a doubt the best buy I have ever gotten on a set of speakers. Here are some shots of them.

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-18.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-17.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-16.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-15.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-14.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-13.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-12.jpg

dew042
10-14-2010, 05:57 PM
Those look to me to be more like the KLH 17 or 23 cabinets. And, didn't the 6's have a 12" woofer?

dew.

xpert54
10-14-2010, 06:04 PM
I have a set of the Optimus ones however mine have the black Grill cloth. Except for the grill cloth they are identical to the set you have and yes they are great sounding speakers.

speedle
10-14-2010, 06:08 PM
Very nice Optimus 1's! Those look like early versions of the woofers from the 5's and later the Optimus 9's. I love those woofers, I use them in the bass bins you see in my avatar.

aabottom
10-14-2010, 06:10 PM
Yeah, I should have got the Optimus-1B instead of the Optimus-2B back in 1975. I was too cheap/poor to spend an extra $40.

JohnVF
10-14-2010, 06:14 PM
I agree, they look more like KLH-17s. They're in really nice condition, too. I wouldn't look to flip them for a profit. However nice they might sound and look, you aren't going to bring in a lot for vintage Optimus speakers. Best to sit back and enjoy the music because you aren't going to find much else for $10 that looks like that (and makes music instead of sound).

glen65
10-14-2010, 06:16 PM
Very nice condition, here's from the 1970 catalog.


http://i29.photobucket.com/albums/c264/Genx65/Optimus1and2.jpg

HTHMAN
10-14-2010, 07:26 PM
Those look to me to be more like the KLH 17 or 23 cabinets. And, didn't the 6's have a 12" woofer?

dew.

The KLH-6 was a 2-way acoustic suspension with a 10" woofer. The KLH-5 was a 3-way with a 12" woofer, 2 mids and 1 tweeter. The Optimus 5b (which I owned) was a copy of that speaker. To quote Radio Shack in the 1970 catalog "We designed around the sound of our favorite speaker (selling for $134.00)". The price of the KLH-6 in the 1967 Radio Shack catalog (back when they sold Scott, Fisher Marantz, Electrovoice, Wharfedale etc) was in fact $134. The KLH-17's were also a 2-way with a 10" woofer in a smaller cabinet (not sure if they used the same drivers) and sold for $69.95 in the same catalog. The Optimus-1 cabinet is closer in size to the KLH-6. What the Optimus 1 really looks like is the AR3, but that had a 12" woofer and was a 3-way system. Sure wish I would have bought those when they were $200 as you pay many times that now.

JohnVF
10-14-2010, 07:43 PM
The second speaker in Glen65's ad looks a LOT like an AR-3a. I wonder how those sounded?

stereofanboy
10-14-2010, 08:02 PM
The KLH 17 is not quite a quarter of an inch taller and one quarter of an inch wider than the Optimus 1B. The Optimus 1B is about two inches deeper than the KLH 17. The frame of the woofer in the KLH 17 is about an eighth of an inch larger than the frame of the woofer in the Optimus 1. The cone on the KLH is about one half inch smaller than the cone on the Optimus.

I should mention that the box measurements were taken from an Optimus 1B, while the woofer measurements were from a woofer from an Optimus 1 no B.

dr*audio
10-14-2010, 08:41 PM
You got a great deal! My first good speakers were Optimus 1's. I got the white grille, like yours and my Dad got the black grille. He still has his. The friend I sold mine to still has his. When we bought them, they were on sale for half price; $60 for the pair. The deal was actually "buy one for $60, get the other one free." Silly. I have a friend with the KLH 17's and the Optimus 1 cabinet looks just like it, with that extra strip on the front. The KLH 6 had at least 2 versions. The earliest had a 12" woofer and the drivers were epoxied in, so you could not service the cabinet. The later version, which I had, used a 10" woofer, and the drivers were not epoxied in.

rmeade
10-15-2010, 12:16 AM
Is it possible that the two smaller speakers on the Optimus are not identical high frequency speakers? Could one, perhaps, actually be a midrange - powered on the same circuit as the tweeter and thus using a 2-way crossover?

absolve2525
10-15-2010, 01:03 AM
Hey guys - an easy trick to fix those dented tweeters... First, get a simple drinking straw. Then, lightly "wet" the dented dome with whatever u feel like. I used a dab of alcohol with my finger. Then, with the straw in ur mouth, suck as hard as you can with the other end of the straw as CLOSE as possible to the dome, so its nearly air tight. Easy as pie! I used this method on some seemingly impossible Kenwood phenolic tweeters... and theyre fine now! I also did it on a pair of old Nova/Optimus speakers.

AnalogDigit
10-15-2010, 01:10 AM
Those look nice. I notice Radio Shack sold those speakers for quite a long time.

dr*audio
10-15-2010, 06:59 AM
Is it possible that the two smaller speakers on the Optimus are not identical high frequency speakers? Could one, perhaps, actually be a midrange - powered on the same circuit as the tweeter and thus using a 2-way crossover?

I replaced both of the tweeters in mine once, in warranty. They are identical.

kreichenbach
10-15-2010, 07:10 AM
I saw a single 1B? in excellent condition the other day. If there had been a pair I would have picked them up and been able to add to this post. It might still be there if anyone in Central CT area is interested PM me for the location.

HTHMAN
10-15-2010, 09:38 AM
Hey guys - an easy trick to fix those dented tweeters... First, get a simple drinking straw. Then, lightly "wet" the dented dome with whatever u feel like. I used a dab of alcohol with my finger. Then, with the straw in ur mouth, suck as hard as you can with the other end of the straw as CLOSE as possible to the dome, so its nearly air tight. Easy as pie! I used this method on some seemingly impossible Kenwood phenolic tweeters... and theyre fine now! I also did it on a pair of old Nova/Optimus speakers.

I will try that on that dust cover on the tweeter. Sure beats picking at it with a needle. I have never understood why people find it necessary to poke the dust covers with their fingers. Thanks for the tip.

Copa1934
10-16-2010, 11:52 PM
Per the catalog they are mid/tweeters. http://www.radioshackcatalogs.com/catalogs/1975/ page 24.

HTHMAN
10-17-2010, 10:40 PM
The speakers in the 1975 catalog were Optimus 1b's. The ones I picked up were about 5 years older and at least the woofer was different.
http://www.radioshackcatalogs.com/catalogs/1968_small/ page 18
I used to have a set of Optimus 5b's that I sold a couple months ago that were fine sounding speakers. Since I no longer have them, I can not do an A/B comparison, but I seem to get better imaging with the 1's than I did with the 5b's. Perhaps someone who has/had both can chime in on the sound comparison. Also what people think of the 1's vs the 1b's and the 5's vs the 5b's. To me, the drivers in the b models looked to be a little more cheaply made.

geiman
10-18-2010, 07:57 AM
The "B" drivers are a homage to efforts at cost cutting.
We had both Optimus 5's and and 1's in stock when I was a Radio Shack manager.
The Ones image better like you suspected.
Also,
I think a better crossover would help the Optimus 1 a great deal.
I would like to see the T/S parameters for the drivers in these.

stereofanboy
10-18-2010, 09:28 AM
.......I think a better crossover would help the Optimus 1 a great deal.
I would like to see the T/S parameters for the drivers in these.

+ 1, I'd like to see them for the Ones, One Bs, Fives, and Five Bs.

speedle
10-18-2010, 10:34 AM
These are for the Optimus 5's I believe. I got them from Ed over on the Yahoo Realistic group.

Vas: 4.5848
Qms: 4.8624
Qes: 0.6577
Re: 7.0658 ohms

No Fs or Qts though, dunno why.

dew042
10-18-2010, 10:35 AM
The KLH-6 was a 2-way acoustic suspension with a 10" woofer. The KLH-5 was a 3-way with a 12" woofer, 2 mids and 1 tweeter. The Optimus 5b (which I owned) was a copy of that speaker. To quote Radio Shack in the 1970 catalog "We designed around the sound of our favorite speaker (selling for $134.00)". The price of the KLH-6 in the 1967 Radio Shack catalog (back when they sold Scott, Fisher Marantz, Electrovoice, Wharfedale etc) was in fact $134. The KLH-17's were also a 2-way with a 10" woofer in a smaller cabinet (not sure if they used the same drivers) and sold for $69.95 in the same catalog. The Optimus-1 cabinet is closer in size to the KLH-6. What the Optimus 1 really looks like is the AR3, but that had a 12" woofer and was a 3-way system. Sure wish I would have bought those when they were $200 as you pay many times that now.

For clarification, I just measured each and the 17 has a 10 inch woofer and the 6 has an 11 inch one. Definitely not the same woofer.

dew.

speedle
10-18-2010, 10:36 AM
Here's the full skinny, unedited:

Just finished testing a coupl more woofers, and thought I'd share
the
> findings:
>
> Optimus-5B/Nova-8B 12" Woofer
>
> Better than I thought it would be. This woofer, like it seems all
> Realistic speakers, was designed for max whomp with a Qtc of 1.15-
1.2
> in in the Opti-5B enclosure. The F3 is 36-37 Hz, only ever so
slightly
> better than than the 10" Opti-1, which achieves an F3 of around 38
Hz,
> but not close to the claimed 20 Hz. It is best suited for sealed
> enclosures, so I wouldn't try porting this box. It would seem that
as
> with the Opti-1 vs. 1B, the newer B version of the 1 and 5 are
indeed
> improvements, even though they utilize slightly smaller cabinets.
>
> Optimus-2B/Nova-6 8" Woofer
>
> Same as above, maxed out Qtc of 1.2, F3 47-48 Hz. Not suitable for a
> ported enclosure. If you plan on upgrading the tweeter and leaving
the
> stock woofer in place, you *must*:
>
> a.) Replace the crossover or kiss your new tweeters goodbye. A
Dayton
> 12 dB crossover at 2000 Hz works beautifully, and
>
> b.) Add a Zobel circuit to flatten out the impedance. The impedance
> begins to climb with all of these Realistic woofers around 400 Hz,
> because that's about where they were crossing over to the cone
> tweeter. The correct values to use for the Opti-2B are 16.04
> microfarads cap, 9.5 ohm resistor. Solder the cap & resistor
together,
> and bridge them between the positive and negative connections on the
> woofer.
>
> If you'd like to try adding a Zobel circuit to your existing
Realistic
> woofer, here are some values:
>
> Opti-5B/Nova-8B: 32 uf cap, 8.83 ohm resistor
> Opti-1/Nova-7: 12 uf cap, 8.21 ohm resistor
> Opti-1B/Nova-7B: 31 uf cap, 9 ohm resistor

Again, just reposting what I got over there in response to my investigation back when I was working with these woofers.

stereofanboy
10-18-2010, 12:58 PM
Super!

geiman
10-18-2010, 06:46 PM
Thanks Speedle. Thanks for sharing.

I guess I need to check into joining over at Realistic Group too.

Copa1934
10-18-2010, 11:15 PM
I'll have to join that group.

proimage1
03-05-2012, 07:22 PM
I have a lead on these speakers on my local Craig's list for $30 - original owner and claims they are in perfect condition - would $30 be a fair price for a pair of these.

Ironically there is also a pair of these listed one line below these for these - also $30for the pair - and nope, it's not the same seller from what I can tell.

REALISTIC NOVA 15 SPEAKERS

HTHMAN
03-05-2012, 07:51 PM
I have a lead on these speakers on my local Craig's list for $30 - original owner and claims they are in perfect condition - would $30 be a fair price for a pair of these.

Ironically there is also a pair of these listed one line below these for these - also $30for the pair - and nope, it's not the same seller from what I can tell.

REALISTIC NOVA 15 SPEAKERS

I would take the Optimus 1's. They are very good speakers-I have 2 pair. I would pass on the Nova 15's. I have a pair of Nova 5's that are probably the same drivers in a little different box. They just are not in the same league as the Optimus 1's. Much too boomy for my taste, but I got them for free because they needed foam. They are worth a generic refoam but not much more.

proimage1
03-05-2012, 08:08 PM
I would take the Optimus 1's. They are very good speakers-I have 2 pair. I would pass on the Nova 15's. I have a pair of Nova 5's that are probably the same drivers in a little different box. They just are not in the same league as the Optimus 1's. Much too boomy for my taste, but I got them for free because they needed foam. They are worth a generic refoam but not much more.

Then the 1's I'll get - seemed like a good deal if they're in as good a condition as he says they are -- hopefully sometime this week I can run over and check them out - about 45 minutes from where I live -- they might be gone, but I'll know soon enough. Really, the last thing I need right now are MORE speakers OR anything else to - but we all know how we are ! :banana:

Thanks for the advice ! Appreciate it !

eizner23
07-21-2013, 08:03 PM
Thank you speedle for the post about the zobel circuit. I just bought a pair of Optimus-1 speakers and realized the high freq was bleeding through the woofer when at high volume after reading your post. To balance out the impedance I put together the zobel circuit then hooked it up using alligator clips and tested it. The low frequency is a lot cleaner and less distorted than when bypassing the circuit. Your friend really knows his stuff. Cheers to him.

Here are a few images for those interested
http://i44.tinypic.com/okoowj.jpg
http://i39.tinypic.com/29ymu1k.jpg

n.phelge
12-13-2013, 09:27 PM
Quick question: I picked up a pair of Optimus-1 speakers today, and I don't see how the cloth grill is removed. There isn't any gap between the cabinet and the grill - I tried to wedge a butter knife in, and it wouldn't fit. How is the cloth grill removed from the front?

Thanks

HTHMAN
12-13-2013, 10:05 PM
Quick question: I picked up a pair of Optimus-1 speakers today, and I don't see how the cloth grill is removed. There isn't any gap between the cabinet and the grill - I tried to wedge a butter knife in, and it wouldn't fit. How is the cloth grill removed from the front?

Thanks

There is a strip of Velcro at each corner. You need to pry a corner out and the rest will follow. Try a putty knife or a stiff wire bent at 90 degrees at the end to get behind it. Every time I take mine off, I say that I need to put a pull tab on it, but never do it.

Hooked one of my pair to my Realistic STA-2000 a couple days ago. Great match for each other.

n.phelge
12-14-2013, 02:16 PM
There is a strip of Velcro at each corner. You need to pry a corner out and the rest will follow. Try a putty knife or a stiff wire bent at 90 degrees at the end to get behind it. Every time I take mine off, I say that I need to put a pull tab on it, but never do it.

Thanks a lot. It took a while, but I was finally able to get them off, and then I stapled a short piece of ribbon to the back of the grill cover to help in the future. Now I just need to clean them up and try to restore the finish a bit.

Copa1934
12-14-2013, 02:44 PM
There is a strip of Velcro at each corner. You need to pry a corner out and the rest will follow. Try a putty knife or a stiff wire bent at 90 degrees at the end to get behind it. Every time I take mine off, I say that I need to put a pull tab on it, but never do it.

Hooked one of my pair to my Realistic STA-2000 a couple days ago. Great match for each other.
Another option is a paint can opener. I've been using one for years now for MANY speaker, shall I say, challenges. Prying up drivers, taking off stubborn grills, etc.

n.phelge
12-15-2013, 06:42 AM
Another option is a paint can opener. I've been using one for years now for MANY speaker, shall I say, challenges. Prying up drivers, taking off stubborn grills, etc.

That was exactly what I used, but with the addition these tiny strips of ribbon, I won't have to worry about scratching up the frame.

Copa1934
12-15-2013, 11:05 AM
That was exactly what I used, but with the addition these tiny strips of ribbon, I won't have to worry about scratching up the frame.
Yeah, definitely like the idea of the ribbons. Or something, anyway, to make removal easier. Just messing with my 5b speakers yesterday. Not too bad, but still would be a lot easier with something to pull on.

Soundminded
12-15-2013, 05:26 PM
I used to own the Realistic Optimus 5B speakers that were a blatant KLH-5 copy. Those were great sounding speakers, but sold them because they did not fit into my wife's decor.

I was on Craigslist and saw a pair of Optimus-1 speakers listed in town for $10. I could not get there fast enough. Those were the first and one of the best of the good Radio Shack speakers. Their ad from about 1970 said that they copied the sound of their favorite $134 speaker at 30% less cost. They would not mention the brand, but the excellent KLH-6 by coincidence was selling for $134. Both were acoustic suspension with a 10" woofer (that look very similar) with a 2-way crossover. The difference was that KLH used 1 tweeter and Radio Shack used two. The speaker uses a 3-way switch to adjust the tweeters for normal, low and high levels.

I cleaned them up and hooked them up today. Wow!!! These are great sounding speakers. This is without a doubt the best buy I have ever gotten on a set of speakers. Here are some shots of them.

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-18.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-17.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-16.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-15.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-14.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-13.jpg

http://i301.photobucket.com/albums/nn47/jsaus63304/Optimus-1/Optimus-12.jpg

the edge to edge diameter of the actual cone...the black part for KLH model 6 is 7 inches. The 12" rating is based on the distance between opposing mounting screw holes. The distance across the cone is what matters. The KLH model 6 and AR2series have the same effective size cone even though the AR2 series is rated at 10". This may be a KLH woofer but maybe not. It has the same orange concave outer suspension many variants of the KLH model 6 speaker had but there's no way to tell if it really is one. The tweeter does not look like a KLH tweeter. My hunch is that they are not the same.

Copa1934
12-15-2013, 05:47 PM
Those are serious cabs! With the exception of a couple 15" driven speakers, early RS speakers had good size cabinets, probably much better matched to the drivers installed. Mach speakers are notorious for having too small a cabinet.

They sure look nice. Deep buggers, like my HPM speakers. They aren't very wide, but boy they are deep.

GD70
12-15-2013, 07:20 PM
the edge to edge diameter of the actual cone...the black part for KLH model 6 is 7 inches. The 12" rating is based on the distance between opposing mounting screw holes. The distance across the cone is what matters. The KLH model 6 and AR2series have the same effective size cone even though the AR2 series is rated at 10". This may be a KLH woofer but maybe not. It has the same orange concave outer suspension many variants of the KLH model 6 speaker had but there's no way to tell if it really is one. The tweeter does not look like a KLH tweeter. My hunch is that they are not the same.

Those are not KLH six woofers. Just a copy. KLH baskets don't protrude out, the dust caps are much smaller, the cone material is not smooth but textured. The cloth surrounds are actually white, the sealer is black on model sixes except for the early epoxied woofers, which are similar to the Optimus surrounds, and used a clear surround sealer. I have both versions of the model six. I also believe the six and model five and twenty three woofers are the same size, but the five and twenty there's magnet is larger. The six woofer is unique to that speaker. KLH advertised them as a 12 inch woofer, the model 17's as a 10 inch woofer.

GD70
12-15-2013, 07:22 PM
Those are serious cabs! With the exception of a couple 15" driven speakers, early RS speakers had good size cabinets, probably much better matched to the drivers installed. Mach speakers are notorious for having too small a cabinet.

They sure look nice. Deep buggers, like my HPM speakers. They aren't very wide, but boy they are deep.

The KLH six's cabs are deep and the Optimus clearly copies the KLH six cab size with the seventeen lip around the front.

Copa1934
12-15-2013, 10:54 PM
RS, and I guess Heathkit to some extent, were some of the best copycats and I mean that in a flattering way. They did their homework, though much of the credit likely lies with the manufacturer since RS didn't "build" speakers, that I'm aware of.

Heathkit, however, did have speakers identical to JBL, like the L88 clones, had the same drivers, crossovers, terminal plates. If they weren't rebadged JBL speakers, they were bloody good clones.

BillyBatts
12-15-2013, 11:03 PM
Nice speakers.

I've got a pair of Optimus 10's I bought around 1978 ish.
8" drivers with 10" drones. Just re-foamed them about 3 years ago.

Only issue is I really feel they are lacking in high frequency. I tend to use them with the Realistic "Super Tweeters" that are stand-alone speakers. I have always felt this way, even with 16 or 17 year old ears.

Copa1934
12-16-2013, 10:41 AM
Nice speakers.

I've got a pair of Optimus 10's I bought around 1978 ish.
8" drivers with 10" drones. Just re-foamed them about 3 years ago.

Only issue is I really feel they are lacking in high frequency. I tend to use them with the Realistic "Super Tweeters" that are stand-alone speakers. I have always felt this way, even with 16 or 17 year old ears.
http://www.radioshackcatalogs.com/html/1978/h041.html

3-1/4" tweeter. Pretty large for a tweeter. Might be limited by it's design or the crossover. Kind of funny how they state in bold print "Passive Radiator" then call it a drone in the description. Gotta love RS marketing.

mcsew2k
12-31-2013, 11:05 AM
I just picked up a pair of these (Opti-1) at the local thrift store. What is the max watts these are rated for? Can they handle 70 watts/ch from a Marantz 2270?

n.phelge
03-30-2014, 07:11 PM
The used pair I picked up has some stains on the speaker cloth, so I was looking to replace it. If found some online with a similar tweed look, but it states it is 'acoustically neutral, but not 100% acoustically transparent'. Does anyone know what this means or have a recommendation for a replacement cloth? (color doesn't have to be an exact match) Thanks in advance.

johnda
03-30-2014, 08:56 PM
The RS Nova 8 was a clone of the KLH 5 and mine still sound really good. I also have a pair of KLH 6 speakers that also are still working fine. Henry Kloss advertised the KLH 6's as having 12" woofers. I had been swapping them back and forth in my unheated basement but when it warms up I plan on setting up the A/B speaker option so I can not need to swap them any longer. I need to work on the gear placement so I can do this. The amplification is via my Sony STR-6055. Fun,fun,fun!