Clean low powered amplifier recommendations [available to purchase new from online retailers that ship to Canada], please! :)

[mike7877]

It absolutely does not.

Audibility thresholds of amp and DAC measurements

Introduction A recurring theme on ASR is whether or not the various measured qualities of the devices are audible. In this post, I'll present some clear and visual thresholds for when those imperfections can be considered a potentially audible concern. I will not explain the basics of amp/DAC...

www.audiosciencereview.com

We'd like 85. This amp is very cheap and very close. If you want to spend more money you can get better, but you don't.


You probably need to read this article - it gives a more positive impression than we're giving you here (but deals mainly with a different version of the speaker), and a good idea of the faults involved. It comes from a reliable source.

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 measurements for other models at the bottom of the page shows you what yours are doing. They switched to cheaper drivers and the results are slightly worse, as you might expect.

And no matter what amp you use, it won't stop the driver mismatch or cone breakup from happening. Listening at low volume may help though. Tney may not be so bad subjectively as you are using them, as you say.

85 might be OK because they're not very efficient.

Those speakers are different than mine - the crossover doesn't have a coil on the woofer. Other specs could be different too, but even if they're not, I'd wager my version is later with an added coil on the woofer to fix the trough in response between 2 and 3kHz. Proper driver integration is important and these speakers have it! At least my version does lol. They also have great off-axis response from the small LF driver diameter.

I know what good 2-3kHz range is supposed to sound like - my most listened to speaker is ATC SCM20 Pro PSL Mk II (completely different tweeter and redesigned woofer and completely different enclosure than the aged thing with similar name reviewed here). It now has their S-Spec tweeter which is flat and damped and damn near perfect in its design. It's offered in their best speakers which rival the price of good new cars (yeah, price isn't the only indicator of performance, but they're all about driver design).

So yeah, 18dB butterworth at 2.1kHz to the similarly excellent midbass driver they engineered. Anyway, low distortion, best integration: my baseline.

 

[restorer-john]

It comes from a reliable source.

Even if the comments are from people with very rose-coloured glasses...

 

[mike7877]

Let's pretend I'm just looking for something available in Canada with THD+n >= -85dB @ 5W that can put out 10-20WRMS and costs $100-$150 tops CDN (~80-125US?)
MUST SHIP TO CANADA, and hopefully is in stock lol

 

[VMAT4]

Let's pretend I'm just looking for something available in Canada with THD+n >= -85dB @ 5W that can put out 10-20WRMS and costs $100-$150 tops CDN (~80-125US?)
MUST SHIP TO CANADA, and hopefully is in stock lol

This?

 

[mike7877]

Even if the comments are from people with very rose-coloured glasses...

View attachment 265696

Tolerance on caps could be an issue for why some people had great experiences and some people not so great. Even 10% - +10 on one, -10 on another, that'd screw up imaging. ESR difference between runs because of periodic availability issues... so many things could've gone wrong.

The guy is correct about the huge image.

edit: my version is 4169 if that means anything. Not sure if you saw what I wrote in post 21

 

[mike7877]

This?

About $110 delivered and 82dB,
it's a contender!

 

[mike7877]

It absolutely does not.

Audibility thresholds of amp and DAC measurements

Introduction A recurring theme on ASR is whether or not the various measured qualities of the devices are audible. In this post, I'll present some clear and visual thresholds for when those imperfections can be considered a potentially audible concern. I will not explain the basics of amp/DAC...

www.audiosciencereview.com

We'd like 85. This amp is very cheap and very close. If you want to spend more money you can get better, but you don't.


You probably need to read this article - it gives a more positive impression than we're giving you here (but deals mainly with a different version of the speaker), and a good idea of the faults involved. It comes from a reliable source.

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 measurements for other models at the bottom of the page shows you what yours are doing. They switched to cheaper drivers and the results are slightly worse, as you might expect.

And no matter what amp you use, it won't stop the driver mismatch or cone breakup from happening. Listening at low volume may help though. Tney may not be so bad subjectively as you are using them, as you say.

An 80mm diameter (effective), 73mm cone, 93mm cone+ surround, should NOT break up at 2.1kHz. The driver is so small it's practically working as a piston there... Breakup that low on a driver that size is indicative of a faulty driver

edit: at 2.1kHz dispersion is so wide from an 80mm cone - it's barely out of piston range! There's no severe breakup, that review is faulty.

an 80mm driver is a piston to over 1.6kHz and would have flat frequency response way off centre through at least 3.2kHz

edit2: that speaker.... if you look at its filling material it's yellow. My speaker? White as snow. The rest of that driver is probably equally more decayed than mine. Glue could be failing, any number of things (it doesn't look good). Also don't forget my woofer has a coil so the slopes match and there's proper woofer/tweeter integration (sounds like a point source - probably why the guy wrote they put magnapans to shame (not quite, but they're huge and image better (not wider etc))

edit3: yeah this is the internet - I don't need to convince everyone of how these speakers sound to experience them - I guess those who know, know, and those who don't, don't!

I'm still looking for good > -85dB THD+n @ 5W and 10-20WRMS @ 100-150CDN

 

[restorer-john]

Look, I'm glad you love them. I don't think anyone who bought Minimus 7s from me was ever disappointed either. They did what people wanted and gave tremendous value. Even 35 years on.

As a fun fact, Tandy had no decent amplification/receivers at the time and I'd just built a 200wpc@8R/350wpc@4R dual mono power amplifier. I had it in one of our vertical smoked glass door HiFi racks and used it to demo all the speakers. Including the Minimus 7s. I could sell a pair instantly with Phil Collins' Another Day in Paradise track off CD. People could not believe such a tiny speaker could fill the sound area so well.

When we had Mach Twos (15" 3 way 160W) on sale, we made a 8ft long by 2ft deep board (covered in red fabric) with 6 swivel casters on it, put 8 Mach Twos on it (4 long, two high) and wheeled it out into the shopping centre in front of the store. Series/parallel to my monster amp and lit up the whole shopping mall from our upstairs shop. I used to 'demo'* speakers at lunch time when people were eating in the food court downstairs. You could easily sell several pairs after they heard what they thought was a rock concert upstairs. LOL.

The good old days.

*When security came running we'd just say we were demonstrating for a customer and they said fair enough. I got a few letters about breaching noise rules, but nothing ever came of it. I pointed out each demo was a $600+ sale to our business.

 

[mike7877]

Since that 2.1kHz breakup shown in the review is next to impossible because piston range extends past 1.6kHz and breakup doesn't usually start until more than an entire octave above that, and my speaker has a better crossover and no 2-3kHz dip, I'm going to put my final thoughts on why these speakers are the best choice in my case, before a flood of awesome recommendations for 10-20W amplifiers with better than -85dB THD+n @ 5W come... flooding in!!! (for lack of a better word lol)

Minimus 7:

Weaknesses:
- limited power handling
- limited dynamic range and peak output at lower frequencies
- 3dB less peak bass in the 70-90Hz range than a ported version

Strengths:
- resonance free enclosure (effectively, in practice)
- perfect driver integration
- consistent and wide dispersion of frequency response, aka: "good imaging"
- no port noise
- distortion free operation from quiet up through reasonable listening levels
- LF extends lower because of the nature of sealed enclosures: 12db/oct rolloff reaches lower than any same-sized ported design (this is always the case re: sealed vs. ported)
- finally, with the caveat of lowering maximum average music power, low frequency response can be extended to well below what most consider physically possible at 1 atmosphere due to physics, using just a bit of equalization (mirroring the rolloff in the positive, then rolling off aggressively (like ported) to avoid over-excursion

There just isn't anything that brings these things to the table (especially the resonance free enclosure and point-source-esque-ness) for $100-200, and likely more (especially in the new market).
Considering I already have them and they're for use in a very secondary system that's effectively a research workstation also occasionally used for media consumption, I'M KEEPING 'EM
lol

Awesome amps commence in 3, 2...

 

[mike7877]

*When security came running we'd just say we were demonstrating for a customer and they said fair enough. I got a few letters about breaching noise rules, but nothing ever came of it. I pointed out each demo was a $600+ sale to our business.

I'm surprised you got to keep getting away with it! Lol
I bet nobody ever complained, it was just the administration.
Was giving them the reason that it made you money helpful? Past what your store gave for rent, that's something I wouldn't think they'd care about (unless your store was doing so bad that those $600s were what was paying the rent lol)

 

[posvibes]

I remember reading about the Minimus 7's on almost every second speaker thread at Audiokarma, they were nuts about them, and they were always found for $5 a pair at a garage sale or Goodwill stores throughout America for chump change and then hooked up with what seemed a bottomless ocean of vintage amplifiers of yesteryear manufacturers.

 

[mike7877]

I remember reading about the Minimus 7's on almost every second speaker thread at Audiokarma, they were nuts about them, and they were always found for $5 a pair at a garage sale or Goodwill stores throughout America for chump change and then hooked up with what seemed a bottomless ocean of vintage amplifiers of yesteryear manufacturers.

It's sad that they're [vintage amplifiers] becoming more rare... capacitors only last so long and the era ended in the early 80s... I still have an RT-707 - all original components. Coming up on 45 years old, it still works perfectly!! I want to recap it, but there are so many boards and they all have soooo many caps. It'd be so much work. I just got two new old stock Type II Maxell EE tapes for it. And two of the Maxell 7" steel reels (new)
It all cost almost $400. No more than new with inflation. Geesh audio equipment was expensive!! And that's part of the reason why it's still around and the stuff from the late of the early 80s on, is not!! Stuff got cheaper then... and not designed with repair in mind. Schematics? Who needs 'em! The exceptions were mechanical stuff, but by then that was all slowly on the way out

 

[Galliardist]

Archimago describes a resonance, not woofer breakup, at 2.1kHz. Different things.
I'm left wondering if your speakers are modded. I don't know that they were built with anything in the woofer path.
I note also that he describes the speaker cabinets as vibrating, something I can confirm from experience, and you say yours are solid. Maybe you are listening at a lower volume and getting less of the negative?

I can't concur with your findings from my experience of these speakers, and I would suggest that even some of the poorer Edifier models are better in practice for little more money.

But it's your show. I'm on the other side of the planet and we're just typing at each other.

Better you find that good amp. In the reviews:

https://www.audiosciencereview.com/...ics-sylph-d200-amplifier-module-review.25295/ (SINAD 94)

https://www.audiosciencereview.com/.../topping-pa3s-review-desktop-amplifier.27079/ (SINAD 87)

Both probably a bit out of your price range, I'm afraid, but they hit your target. The first one's available as a kit if you're OK with that.

 

[restorer-john]

unless your store was doing so bad that those $600s were what was paying the rent lol

We were doing very well. The store was highly profitable and back then, managers received on top of all other perks, 10% of bottom line profit annual bonus. Sadly, that was done away with due to some unprofitable managers complaining they missed out. We'd agressively pushed for lower rents, contributions for fitouts etc and had a great lease, small shop, high turnover and low staff costs. Very tight inventory control and consistently solid inventory gains by moving, stocking and selling the right mix of product.

But what we also had was one of the finest salesman I have ever met. I was young, knew tons about everything electronic but he was a seasoned salesman and I wanted to be as good as him. I soaked up everything from him and Tandy Corp like a sponge, went to all the meetings, drank with the old timers and learned how to sell snow to the eskimos. I took over the store and he went on to a bigger, better store to turn it around and make more money.

One of those people you meet and work with who leave an indelible mark for the better. Lost track of him now, but I'm sure his daughters are all grown up and he's most likely a grandfather several times over.

Fun times.

 

[mike7877]

Archimago describes a resonance, not woofer breakup, at 2.1kHz. Different things.
I'm left wondering if your speakers are modded. I don't know that they were built with anything in the woofer path.
I note also that he describes the speaker cabinets as vibrating, something I can confirm from experience, and you say yours are solid. Maybe you are listening at a lower volume and getting less of the negative?

I can't concur with your findings from my experience of these speakers, and I would suggest that even some of the poorer Edifier models are better in practice for little more money.

But it's your show. I'm on the other side of the planet and we're just typing at each other.

Better you find that good amp. In the reviews:

https://www.audiosciencereview.com/...ics-sylph-d200-amplifier-module-review.25295/ (SINAD 94)

https://www.audiosciencereview.com/.../topping-pa3s-review-desktop-amplifier.27079/ (SINAD 87)

Both probably a bit out of your price range, I'm afraid, but they hit your target. The first one's available as a kit if you're OK with that.

I know they're not modded because my dad bought them and gave them to my mom's parents, and they've kept them in their living room since new. Basically they've been used for music at family gatherings and that's about it. Per year they got maybe 20 hours playing background music for 30 years. Some might say they've just broken in!

Yeah, their enclosures are effectively dead. That's whether I don't equalize the bass at all (flat) and play music louder until just before excess woofer excursion starts affecting the sound, or if I pump even more energy into them by rolling off the extreme lows (which for them is 120Hz 12dB, making an effective 24dB/oct cut, because the sealed enclosure also does 12 from around 120Hz) and turn the volume up even higher.
Also I've never heard a buzz from them of any kind. Actually, maybe once during over excursion of a test tone. During testing I've brought these woofers up to the level that's right before harmonic distortion sets in (~6mm peak to peak for a sine wave). Frequencies covered were between 30 and 180Hz and sweeps of smaller portions. Nothing!
I really hate speakers that buzz, and you can probably tell, I like these ones haha

Checking out links. I'm OK with kits as long as they come with all the parts and there aren't an excessive number of them

 

[restorer-john]

Well @mike7877 , we can make you the unofficial President of the "ASR Minimus 7 Appreciation Society", going forward. You should post anything and everything to do with these little wonders of HiFi in this thread.

They appear to be the Chuck Norris of mini loudspeakers.

I'll take a few pics of some of mine and we'll do a few shoot-outs just for fun.

 

[mike7877]

We were doing very well. The store was highly profitable and back then, managers received on top of all other perks, 10% of bottom line profit annual bonus. Sadly, that was done away with due to some unprofitable managers complaining they missed out. We'd agressively pushed for lower rents, contributions for fitouts etc and had a great lease, small shop, high turnover and low staff costs. Very tight inventory control and consistently solid inventory gains by moving, stocking and selling the right mix of product.

But what we also had was one of the finest salesman I have ever met. I was young, knew tons about everything electronic but he was a seasoned salesman and I wanted to be as good as him. I soaked up everything from him and Tandy Corp like a sponge, went to all the meetings, drank with the old timers and learned how to sell snow to the eskimos. I took over the store and he went on to a bigger, better store to turn it around and make more money.

One of those people you meet and work with who leave an indelible mark for the better. Lost track of him now, but I'm sure his daughters are all grown up and he's most likely a grandfather several times over.

Fun times.

Nice. 10% of profits is fair, and like you pointed out it incentivized you to bring costs down. The only potential problem I see with that would be the incentivization of higher turnover rates for regular employees. Most people are moral though and don't deliberately mistreat others for what might amount to a small fraction of a percent of that 10%. But there are psychopaths - those sick and twisted creatures with lobotomized emotional centres. I wonder if as a group they're a large part of why a lot of places don't have similar incentives anymore.

Your post was so positive and I seem to be ruining it by talking about the present climate! I didn't mean to lol

 

[mike7877]

These aren't pretty (I already had them from when I put together the picture in the OP), but I got one of the crossover. I'll show the magnets of the woofer and tweeter, better pictures of them to follow tomorrow:

Big magnets!

I remember looking at the back and there not being a power handling printed - just impedance

 

[Adaboy4z]

When I was in college me and some friends would go into Radio Shack and look at all the modern electronics. I remember seeing the Minimus 7s and other small speakers. I always wanted a pair but ended up buying a Koss mini system from sears. There is a pair for sale on Offerup locally right now.

 

[mike7877]

It looks like the tweeter is 2nd order electrical!
I didn't look in all the fluff for more components, but it's possible the woofer is filter free (its coil is a coil... lol). It'd have to be down 6dB by ~3kHz (I plotted voltage then calculated power to the tweeter through the crossover (assuming 8 ohms) and by 3kHz the woofer would have to be down ~6dB. Or something like that.. the file disappeared. I have some time in the next few days, maybe I'll get my scope out for some really accurate measurements that I don't have to first control for my multimeter's decreasing sensitivity above 2000Hz...