Minimus 7 Loudspeakers - Measurements

Neat! The casting boss is already tapped on my mini's. Is that normal? Either way, saves me a trip to the machine shop (where I'm quickly exhausting my cache of favors.)

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Edit... the bottom two aren't tapped and it seems folks are using those to secure the crossover board to the cabinet. Off to the machine shop, it seems.
 
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It's not so hard to DIY. The right drill bit, a steady hand and a tap set of appropriate specs. Oh and a bit of patience too..........
 
Edit... the bottom two aren't tapped and it seems folks are using those to secure the crossover board to the cabinet. Off to the machine shop, it seems.
That seems odd.

So what model M-7 do you have? Except for the very first model with round terminal cups (Cat.No. 40-2030), I thought all Realistic Minimus branded 7s in aluminium cabinets have tapped holes at either side of the terminal port at the bottom. Weren't there screws in there holding down the plastic terminal/crossover plate?

If you're referring to the cast bosses in the bottom corners, those too are tapped, but from the outside to attach optional mounting brackets. Haven't seen anyone use those for the crossover mod ...
 
That seems odd.

So what model M-7 do you have? Except for the very first model with round terminal cups (Cat.No. 40-2030), I thought all Realistic Minimus branded 7s in aluminium cabinets have tapped holes at either side of the terminal port at the bottom. Weren't there screws in there holding down the plastic terminal/crossover plate?

If you're referring to the cast bosses in the bottom corners, those too are tapped, but from the outside to attach optional mounting brackets. Haven't seen anyone use those for the crossover mod ...

Sorry, my mistake. The the terminal holes are tapped, I was referring to the bottom corner bosses which aren't tapped from the inside of the cabinet. Due to interference from the front baffle, there's no way to drill and tap those. I'm going to mount the crossover board with the two terminal holes, and the center boss that is tapped from the inside.
 
Lately, I have been debating what to do with the oversized woofers...and separately, I have been thinking about building a portable bluetooth speaker/boombox. Now, I think I will use the components of this crossover with the drivers and make an enclosure that will house everything in one.

The idea was an evolution of thinking about making a speaker box like the wood cabinets some of the 7s come in....Then I started thinking about using the drivers in a bluetooth speaker system....I already have the drivers and crossover so It is just a matter of building the box and adding an amp board that has blutooth and a battery/powersupply.
 
I picked up a pair of the RCA Minimus 7s (metal, Malaysian-made with bass reflex port) a few months back and I've started using them with a Yaqin MC-100B amp. I was going to go the eBay crossover route, but since I found this thread I plan instead to try the Zilch 2.1 crossover. It looks like Parts Express is out of stock of the 10W 40ohm resistors until June. Has anyone tried a non-"audio-grade" resistor in place of the Parts Express resistors, and have you had any issues with them?
 
It looks like Parts Express is out of stock of the 10W 40ohm resistors until June. Has anyone tried a non-"audio-grade" resistor in place of the Parts Express resistors, and have you had any issues with them?
That resistor seems to be frequently out of stock at PE. Blame the popularity of PZ-2.1 ...

Pete B, who's original design is the basis for PZ-2.1, has developed an alternate version, PZ-2.2, that uses standard sand cast resistors and also offers an optional variable tweeter level control. Details can be found in his thread which demonstrates an easy method for fabricating a PCB for the crossover.

Many highly regarded loudspeaker systems use similar resistors in their crossovers without issue.
 
That resistor seems to be frequently out of stock at PE. Blame the popularity of PZ-2.1 ...

Pete B, who's original design is the basis for PZ-2.1, has developed an alternate version, PZ-2.2, that uses standard sand cast resistors and also offers an optional variable tweeter level control. Details can be found in his thread which demonstrates an easy method for fabricating a PCB for the crossover.

Many highly regarded loudspeaker systems use similar resistors in their crossovers without issue.

Cool, thanks! I did a little bit of searching but this is such a large thread that things can get buried a bit.
 
I just picked up a pair of optimus pro x7, so decided to dig out my pair of minimus 7 to compare side by side. At first glance the similarities are obvious, probably the same spring connectors, and tweeters. Possibly the same woofer. The optimus are larger, with cooler looking shape casted to the cabinet. But once you start pumping music through them, there's no contest. The pro x7 trounce the minimus 7 in every category. Especially in the low end.

I was searching if anyone had experimented with similar crossover upgrades on the pro x7. I'm hesitant to try the minimus 7 upgrades on them as is, they just sound too different stock.
 
I just picked up a pair of optimus pro x7, so decided to dig out my pair of minimus 7 to compare side by side. At first glance the similarities are obvious, probably the same spring connectors, and tweeters. Possibly the same woofer. [snip]

I was searching if anyone had experimented with similar crossover upgrades on the pro x7. I'm hesitant to try the minimus 7 upgrades on them as is, they just sound too different stock.

Woofers, at least, are different. Pro-X7 woofer is labeled "6Ω." They run free in stock form like M-7 woofers. So they probably suffer similar driver interference issues as a stock Minimus-7, which would undoubtedly benefit from an upgrade. It does seem unlikely they would realize optimum performance using PZ-2.1 / PZ-2.2 crossovers which are modeled for the 8Ω M-7 woofer.

For whatever reason, Pro-X7 never excited the market quite like Minimus-7. After Pro-X7 faded from the catalog Radio Shack still offered the Optimus (and later RCA) PRO-X44AV, a ported and magnetically shielded Minimus-7.
 
For whatever reason, Pro-X7 never excited the market quite like Minimus-7. After Pro-X7 faded from the catalog Radio Shack still offered the Optimus (and later RCA) PRO-X44AV, a ported and magnetically shielded Minimus-7.

Strange indeed, stock to stock, the pro x7 are far and away the superior speaker.
 

Within the context of Minimus-7 modded with PZ-2.x crossovers, the aluminum coned mid-woofers from MCM will likely offer closest sonic compatibility.

Pete B. installed and measured 55-1853 and found it to be "an excellent match." Pete also references Zaph's build of a well regarded mini speaker with this mid-bass driver, while exploring optional low pass filter options for its use in PZ-2.x crossover modded Minimus-7.

Also see streckfu's posts about replacing the stock woofer with MCM's similar 55-1856. He reports "great" sound and notes a satisfying balance with "much more low end."

From your list of PE's small woofers, consider that PRV Audio 4MR60-4 boasts a relatively high 90dB sensitivity rating, which would likely overpower the stock tweeter. Doesn't look like any of these drivers will fit a stock Minimus-7 cabinet. Are you planning to build custom cabinets?
 
Within the context of Minimus-7 modded with PZ-2.x crossovers, the aluminum coned mid-woofers from MCM will likely offer closest sonic compatibility.

Pete B. installed and measured 55-1853 and found it to be "an excellent match." Pete also references Zaph's build of a well regarded mini speaker with this mid-bass driver, while exploring optional low pass filter options for its use in PZ-2.x crossover modded Minimus-7.

Also see streckfu's posts about replacing the stock woofer with MCM's similar 55-1856. He reports "great" sound and notes a satisfying balance with "much more low end."

From your list of PE's small woofers, consider that PRV Audio 4MR60-4 boasts a relatively high 90dB sensitivity rating, which would likely overpower the stock tweeter. Doesn't look like any of these drivers will fit a stock Minimus-7 cabinet. Are you planning to build custom cabinets?

No I was not building custom cabs, I have a credit with PE and thought I might use it on this project, but if the MCM are a better match then I will go that way then.

Has anyone reviewed the PE rebuild of the M7's?
 
I just bought a pair of Minimus 7's this week and have spent a few hours reading through these pages. I want to thank Pete and Zilch (RIP) for the work in perfecting this design, plus all the others that have contributed to this topic over the years. What a valuable resource to a beginner like me. Building these cross overs is my first soldering project.
I just want to update everyone in the latest cost from Parts Express for the parts. I ordered everything including the optional binding posts and inductor. Apparently the cost has doubled since this was first posted. My cart total was a bit over $50 plus the shipping. The cost is not all that important since this is a learning project. Still it is less than the cost of a nice Starbucks beverage for a month of mornings, something that I don't indulge in.
 
This place is a great resource. Audio has become my main hobby because of AK. I was always interested but needed some guidance, a starting point in order to get serious. Fasten your seat belt and lock your beverage tray in the upright position. You're cleared for takeoff.
 
I found a couple of Pro 7's for $5 at the local SA thrift store.
I was not particularly impressed but them. They were thinner-sounding than I expected.

I picked up a Bose Acoustimass passive sub for $3 at GW a few weeks back on a lark, but never hooked it up.
I presently have the two Pro 7s and the sub wired to the A and B outputs respectively on the Sherwood S7100-A in my bedroom.
I need to rewire them the speakers to sub's output terminals, but this is OK for now. I won't be adding additional speakers to this system.

Since the little Sherwood is so punchy, I have had to turn the bass knob well below flat to balance the sound out.
I have to say that with A+B selected this is a really surprisingly nice sounding setup for $8.

This is way less obtrusive than the Infinity tower speakers that I had hooked up previously.

I may just need to freshen this Pro 7s up.
 
Needing some office desk speakers I hit the thrifts and found a nice set of 7s. Using the parts list here's a price update from PartsExpress.

266-550 Inductor $7.50
004-3 Resistor $1.38
004-2 Resistor $1.38
004-40 Resistor $1.38
027-422 Cap $2.79
027-414 Cap $1.61
255-032 Inductor $6.04
090-475 Binding Posts $3.88
Total $51.92

I got a $15 off of $100 coupon so I thought I'd toss a Topping VX1 in the pile to run them.

Coupon expires the 15th so I have a couple of days to procrastinate..
 
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