Realistic Minimus-7 Measurements

[mhardy6647]

The "Idea" and the looks of them are honestly better than the reality of them.

Yup. They were an attempt to cash in on the then-growing popularity of the diecast minispeakers. Everybody did it, but R/S was probably the most successful of the second to market crop.
This is probably well known to anyone here who cares about such things but there is a fairly interesting gangbang review of a bunch of minispeakers from the height of their popularity from Stereo Review.
https://www.worldradiohistory.com/A...iFI-Stereo/70s/HiFi-Stereo-Review-1979-08.pdf pg. 58ff

 

[mhardy6647]

Lafayette's entry (entries, I suppose -- but mostly the, ahem, Pip-Speak ), from the back cover of the last LRE annual catalog (1979).

https://www.worldradiohistory.com/Archive-Catalogs/Lafayette-Catalogs/Lafayette-1979.pdf

 

[GoodSammy]

When we built our home in 1992 we were the first on the block to have an early home theater. It had a Pioneer VSX-5900s receiver driving Boston Acoustics tower front and center with Minius 7s rears. Times moved on, our son took the stereo and speakers off to college. Thought all was lost to history. At Thanksgiving he brought some “junk” he found while remodeling his house. In the pile was the receiver and speakers. All in decent condition. Hooked the Minimus’ to the Pioneer, still sounded great 30+ years later..

 

[Bigaudiodynamite]

I have an old pair of Realistic Minimus-7 speakers. They were from the previous owner of our house, installed as outdoor speakers. They spent 30+ years under an awning. I removed them from the outdoor spot a few years ago and put them aside, they were in surprisingly decent shape despite being covered in dirt and cobwebs. I got the pair out of storage and decided to take some measurements, see if they match previously published data. For instance Archimago's excellent review:

RETRO-MEASURE: Radio Shack / Realistic / Tandy Minimus 7 speakers (early 1980s, Cat. No. 40-2030A)

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

The Minimus-7 was introduced in 1978:
View attachment 394110
There are a bunch of iterations. My pair are 40-2030C, which I believe are from the mid '80s. Archimago's test is an earlier version.

Here they are, just out of storage:
View attachment 394139

There isn't much to them except slick design:
View attachment 394141

Once you have them apart, I recommend washing them with soap and water.
View attachment 394230

The tweeter LC network uses a 0.4mH inductor and a 4.7uF capacitor.
View attachment 394154
The woofer has no filter.

The individual driver measurements in free-air; woofer on left, tweeter on right:
View attachment 394159

The woofer has some evidence of resonances, the impedance slope varies starting at ~2kHz. The tweeter is odd with a double-peak.

Prior to disassembly I had measured both speakers' on-axis frequency response in my room. Both of the speakers are closely matched, small 1dB difference at the 3.5kHz resonance, but within 0.5dB over the rest of the frequency range.
View attachment 394160

I took horizontal and vertical measurements of the speaker at 1 meter on a turntable in 10 degree increments. These measurements were with the grille on. These were merged with nearfield measurements of the woofer using VituixCAD:
View attachment 394222

Bass rolls off below 200 Hz, large peak at 3.5kHz. I have never liked the sound of the Minimus 7. The midrange hump is difficult. The lack of bass and upper treble exacerbates my dislike. That being said, I am awestruck that after 30 years outdoors in the Pacific NW the measurements indicate the speakers work as Minimus 7 should. And sound similar to others I recall.

This measured result is similar to older measurements I have seen of the 40-3030C model, for example:
View attachment 394234

Archimago's test of the earlier version of the Minimus 7 has slightly better bass extension, similar 3.5kHz treble peak.
All of the various models need to reduce the level and integrate the tweeter differently, it's ridiculous! The peak at 3.5kHz sticks out like a sore thumb being right near the crossover frequency where the directivity is also changing rapidly. Even worse sounding with no bass. It's very distracting to listen to.

The resulting horizontal and vertical directivity plots are similar to Archimago's as well:
View attachment 394229

Where is that peak coming from? The tweeter.
View attachment 394264

Rich in odd HD at 3.2kHz, the tweeter's peak is a distortion machine! In a compression test you can see it actually result in positive compression at high volume due to energy sprayed in the tweeter's distortion components!
View attachment 394263

The woofer is a bit ragged with resonances above 2kHz at the same frequencies the blips in the impedance slope occur:
View attachment 394235

View attachment 394238
The tweeter and the woofer are perhaps competing to make the midrange bad.

I know there are some simple proposed tweaks for the Minimus 7. A better crossover that lowers the tweeter level, and reduces the peak. And a crossover for the woofer. The industrial design is fantastic. And the speakers are incredibly weatherproof, durable, and look good. Taming the tweeter/midrange crossover point would help make them completely appealing.

With the Ziltch PZ2.0 crossover installed the 3.5khz disappears and they become smooth as silk. Add a sub and they are very impressive.

 

[plastic_avatar]

With the Ziltch PZ2.0 crossover installed the 3.5khz disappears and they become smooth as silk. Add a sub and they are very impressive.

Working on my own layout and external backplate fir the Zilch mod the past couple of weeks.

Even stock, with a WiiM Mini, Neohipo DC-10, and Douk A5, the stereo imaging across my work desk is as good as my big system. They do better than the little Bostons or Paradigms in my desktop setup.

I'm looking forward to the crossover upgrade =)

 

[son_of_wasps]

I used my phone, Hifi-Apps Speaker Setup, and REW to make an EQ profile. Pop it into Equalizer APO (or EasyEffects for linux) with a -10db preamp. Anyone looking for a free way to make these sound about 5 times better should give it a try. Honestly really impressive. Makes them sound wayyy bigger, not like tin cans anymore. Yes, it is tuned to my room to some degree, but the difference is so large it should help anywhere.

Call me sacrilegious, but I'm a college student with 0 time and $0 in my bank account so... I'm trying to get my money's worth out of these things. Also, in the IEM scene EQs are already pretty well accepted (as it's really hard to perfectly tune and preference varies a LOT).

I'd love to make a better preset at some point, but I don't have the money for calibrated mics right now. If @MAB could send over their raw frequency data I would be happy to do the work!

 

[middlemarch]

I have a set of these, plus some unused amps, plus a couple of unused MiniDSP 2x4HDs and plenty of time on my hands. This thread may just have motivated me to try my hand at doing an active version of my set. Have never tried that before, can't hurt these guys, I don't think.

 

[EJ3]

I have a set of these, plus some unused amps, plus a couple of unused MiniDSP 2x4HDs and plenty of time on my hands. This thread may just have motivated me to try my hand at doing an active version of my set. Have never tried that before, can't hurt these guys, I don't think.

I would be inclined to do the Ziltch PZ2.2 mod and then use active EQ.

 

[JeffS7444]

I used to love endlessly browsing the Radio Shack flyers and catalogs in the 1970s and 80s. Was well aware of higher-end products like Linn turntables, but in the 1970s, my budget was maybe $50 on a really good day. Didn't feel poor, because it seemed to me that I was merely on the low end of "normal". Compared to other RS speakers of the era, I thought Minimus-7 was rather good.

Think I had 4 Realistic Minimus 0.5s at one time or another. Amazing how a $15 speaker could be finished in actual walnut veneer (later ones were vinyl), and sport a die-cast baffle. The self-adhesive grilles never stayed properly in place. And the sound? Eh, it was better than nothing. I imagine that it's frequency response would be an inverted "U" centered around 1 kHz.

I don't currently own any Minimi, but I do have the matching STA-7 receiver.

By the time the Fostex Kanspea became a thing, I could afford to buy 'em on a whim, so that's what I did, along with the fancier metal-domed drivers which were sold as an upgrade. I later found someone who had been seeking the exact things, and off they went, along with the matching Fostex mini-amplifier (should I have kept that last item? Hmm).

 

[Gringoaudio1]

I found the Minimus-7 fantastic at the time. Had three sets over the years. Even had a pair of the ported ones that were put out years after the originals. Bought a mint pair a couple of years ago. After all this time and years of great equipment they sound meh. Nostalgia sometimes is just undeserved.

 

[EVDavis]

I have a pair of wood Minimus 7w's connected to my late 70's cheap Fisher amp with the loudness on and the bass increased just a tad more and they can sound pretty impressive for their size. I think without adding a lot of EQ to them they just aren't that great, okay but not great. But with the loudness on and extra EQ-ing they're fun. I can enjoy them. I'm surprised they can put out as much bass as they do. If they were connected to some high end tube amp or a solid state amp without any type of EQ then they won't work.
Realistic made a couple of small receivers that had a special EQ switch on the back exactly for the Minimus 7's. My guess is that switch plumped up the bass a lot.

 

[plastic_avatar]

I finished my Minimus 7 Ziltch crossovers, but decided to use all the parts as donors for another project...

I have unrealized speaker designs from 26-35 years ago. I thought 'Why don't I put my 3D printing/modeling to use and make some mini proof-of-concepts?'

I'm tired of watching other people make variants on the same themes- for decades =(

Anyhow. The parts are great for the time, and the Ziltch crossover is very nice. The flared/horned/waveguided version sounds best (nearfield) in my setup.

My oldest calls them 'the babies' or 'b4abies' (with the a as a 4, to represent the woofer size).

Pictures:

- finished crossover
- installed crossover
- prototype v1.5 and finished v1
- finished v1 and its adjustable tilt add-on
- a few of the 3D versions I made over a week, before I made prototypes v1 and v1.5

Playing the finished v1's on the big amp, for fun:

The Minimus 7 still give a great bang for the buck, for all kinds of reasons =)

 

[EVDavis]

On a Realistic side note. I found the most pleasant amp that goes well with my John Blue JB3 speakers is my Realistic SA-102 amp. I know it sounds crazy or even stupid but it works. I have found my JB3's to be too bright with most solid state stuff or uninteresting with tubes. JB3's are about the same size as Minimus 7's but it is a single driver "full range" speaker.
I have them in a 8 hole Kallax on its side in the top holes on the ends on a couple of heavy books to give them a bit more height. Realistic amp with a Sparkler CD player. Hi-end, mid-end and low-end all together. Sometimes it works. BTW, I hate bright sounding stuff, so maybe that's why I like this combination.

 

[EJasonC]

Realistic Minimus 7 made in Japan driven by Douk Audio

 

[mhardy6647]

Realistic Minimus 7 made in Japan driven by Douk Audio
View attachment 522211

Ahh, the SA-102. Redoubtable little piece of hardware. All discrete inside, too -- audiophile-approved!

Borrowed internet image.
I've never had an SA-102. I did have a dump find SA-10 that used for some time as a bench test amp, but it's long gone. I actually think I sold it for $2 or $3 at an local/regional antique radio/audio swapmeet.


Pictured just after having undergone a CAT scan, as one may note.

 

[EVDavis]

Ahh, the SA-102. Redoubtable little piece of hardware. All discrete inside, too -- audiophile-approved!
View attachment 522221
Borrowed internet image.
I've never had an SA-102. I did have a dump find SA-10 that used for some time as a bench test amp, but it's long gone. I actually think I sold it for $2 or $3 at an local/regional antique radio/audio swapmeet.


Pictured just after having undergone a CAT scan, as one may note.

The SA-10 is a heck of a design. I have one but I can't get the volume past the 9 o'clock position without bad distortion. At low volumes it's fun but not really serious. Whatever that means.
I also have the Realistic SA 100 which is a lot heavier than the SA-102 but the 102 is the better amp. Later the SA-102 had the insides changed to a chip amp but one can only know the change by looking at the back of the amp to see what production number/code it has. My SA-102 is dead silent. I find that incredible for something at least 45 years old with no work done to it.
Radio Shack made some interesting things. God Bless them and your kitty.

 

[ianbtv]

I had a pair of these in the 80’s in a Toyota SR-5 pickup. Radio Shack sold matching metal brackets that I screwed into the sheetmetal behind the kick panels. Had some nice head unit and an amp driving them. Loud as hell. With the baffles facing the driver and passenger, the “image” was good compared to other in-door solutions. For their time and size, they weren’t bad. Like any small speaker, they benefited from a small room, or in this case, pickup truck.

Did the same, except with the mounting brackets in the back of a ... 1982 Chevette. I know - but that car went to 150K and cost $1500 used. YMMV!

 

[ianbtv]

Yup. They were an attempt to cash in on the then-growing popularity of the diecast minispeakers. Everybody did it, but R/S was probably the most successful of the second to market crop.
This is probably well known to anyone here who cares about such things but there is a fairly interesting gangbang review of a bunch of minispeakers from the height of their popularity from Stereo Review.
https://www.worldradiohistory.com/A...iFI-Stereo/70s/HiFi-Stereo-Review-1979-08.pdf pg. 58ff

View attachment 402233

Size and listenability scores matter here (7's are smallest and highest, respectively, in this review). Form follows function. For bass reinforcement, Kloss intended them to be wall-adjacent, and there were external subwoofers offered. Smart engineering - and now, we have crossover improvements. I'm glad to have my well-maintained black aluminum pair - using with a $60 TPA3255-chip class D amp nearfield (desktop system), mounted ear level on the wall 3 feet away and toed-in.

 

[Torin Krell]

Has anyone compared Minimus 7 measurements between the metal grill off and it on? I wonder if there is any significant difference.

 

[EJ3]

I found the Minimus-7 fantastic at the time. Had three sets over the years. Even had a pair of the ported ones that were put out years after the originals. Bought a mint pair a couple of years ago. After all this time and years of great equipment they sound meh. Nostalgia sometimes is just undeserved.

Good enough to run preliminary tests on gear.
And actually not bad (that does not mean GOOD, either) with a sub.