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Minimus 7 Loudspeakers - Measurements

I've been getting a PE order together for a while, and I've hit a snag. The suggested 1.0mH inductor has been on back order for weeks; was due back 1-22-10, now says 2-19-10.:( So can I substitute any other 1.0 inductor?
 
vanquishfist said:
I've been getting a PE order together for a while, and I've hit a snag. The suggested 1.0mH inductor has been on back order for weeks; was due back 1-22-10, now says 2-19-10.:( So can I substitute any other 1.0 inductor?
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As long as it is the same type (Air core or Iron Core) then go for it.
 
chicks said:
Pete, did you ever get these? Did they work out? I'm fixin' to pull the trigger on these for my powered M7's, and maybe a set for my M77's after that...
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Hi, yes I got several of them and actually measured the inductors but all my M7 work is on hold until I have some spare time, or need them for something, LOL. I don't have any use for them at the moment. My computer speakers are floor standing Polks and I really like them, don't want to go to smaller speakers, LOL!

I'm certain that you can also reuse the crossover board, just strip out all the parts you don't need.

I'm not sure if my first post on this was clear, I would not use the crossover as is, just salavage the 1.1 mH for the woofer and any other parts that can be fit into mine or the final XO design. Inductors can be put in series if you want to try my version with the larger woofer inductor.
 
vanquishfist said:
I've been getting a PE order together for a while, and I've hit a snag. The suggested 1.0mH inductor has been on back order for weeks; was due back 1-22-10, now says 2-19-10.:( So can I substitute any other 1.0 inductor?
Click to expand...
We selected this one for its compact form factor. You can see how neatly it fits in the cabs.

There's available direct from Erse, as well, but they have a $25 minimum.

I usually just place the PE order, they send what they have, and the B/O'd item(s) come later, as soon as they have them, which is sometimes sooner than stated. Get in the queue.... :yes:
 
I had the exact same scenario. Went ahead and placed PE order but the B/O'd inductors showed up a few weeks later. By the time they got here I had completed the build using a different 1.0 pair. Consequently I still have they ones they sent late.
 
Lafayette PipSpeak - Another M7 Variant

Picked up a pair of black-painted Lafayette Pip-Speak Model 1's (Label info: 99-03824W, 8 Ohm, 40W, Made in Japan) at a thrift store last week in both cosmetic and good working order. These are the only pair I have seen, though they do show up on Google and Ebay searches.

Sorry that I can't post pictures but I will do my best to describe them as I have not seen any references to them in AK.

They are the same size and heft of the RS-M7's.
The grill is removable, sits flush with the cabinet face, with the perimeter frame painted brushed-silver. The grill itself is perforated black-painted aluminum with holes a bit bigger than the ones in my M7's. An inner flange on the grille frame makes contact with the inner perimeter of the cabinet and are located with some gummy adhesive blobs as well.

The back has a single tapped hole for a mounting backet (?) and 4 small tapped holes with no screws supplied. SW connections are the typical M7 push-in type.

The drivers have a glued-on red trim ring around the outsides of the two surrounds. The front baffle plate has a layer of thin black foam beneath the mounting flange of the woofer. No foam or gasketing behind the tweeter.

The tweeter (on one anyway) has a label with the speaker model#, and the legend: 1370-36, 8 Ohm, SD-14, 1.7KHz-18KHz, Nominal 10W, Music 20W Max, Japan, 8309NT. The Woofer has a typical rubber-like surround and is labelled: Woofer, 220, 8 Ohm, Japan, 66N. The XO has one copper-wire round coil marked 0.4 and a gray plastic (?) cylinder that I assume is a capacitor. The cabinet itself is partially stuffed with fairly dense FG or rockwool along the back and covering the XO.

A not-very-extensive listening comparison between the PipSpeaks and a pair of my Japanese-sourced M7's began with my thinking that the PS's seemed a bit brighter and more forward than the M7's, but after going back and forth the differences seemed to diminish. Didn't have time to compare them to a pair of Korean-sourced metal M7's or my pair of wooden 7W's yet. These comparisons may not be worth much considering that I have no idea how well the XO caps are working in any of them. Plan to make the AK mods to all of them some day.

Hope that this adds something to the M7 database.
 
I think I figured out what I'm going to do, since two of the inductors are going into M77's, I should be able to easily fit this larger air core in these. As for my M7's, I have something else in the works for those two.
 
Having more than four times the DC resistance of the one we spec'd, I'd suggest that's not a good substitute.... :no:
 
Zilch said:
Having more than four times the DC resistance of the one we spec'd, I'd suggest that's not a good substitute.... :no:
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What issues would one expect if using a substitute from Solen (since I'm Canadian Eh... ) for the 1 mH, such as an 18 gauge with a .47 DCR or a 16 gauge with .31?
 
It's like putting a resistor in series with the woofer; it will increase the damping. Maybe good, maybe not so, but it will decrease the woofer SPL, and you may need to adjust the series resistance in the highpass to bring them back into balance, as disucssed earlier in this thread.

Since the stock unit has nothing in series with the woofer, we strove to minimize the additional resistance using a laminate-core inductor.

Physical size also matters; there's not a lot of excess space in those cabs.... ;)
 
Zilch said:
This better work.... ;)
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Hey Hey Hey Zilch, it really did work! Got them finished up. It was a little tight working inside these with Xtra large size paws. Well worth the effort. Very smooth response within frequency limitations. Nothing like the old edgy brittle response. Zilch, your data don't lie, but of course we all know that anyways. They now rest on the computer desk serving as nearfield monitors with the low end being serviced with a powered sup.

So, here is the computer audio system setup:

USB out to a "Hot Audio" usb dac/headphone amp from an Epay vendor.
PE Sonic T amp
Energy 8" powered sup, $79 on a closeout, driven by the headphone out on the Hot Audio DAC.

Presently listening to Flim & the BBs, "Big Notes"
Thanks Zilch and to all who contributed to this project.
 
1MOR said:
Zilch, your data don't lie, but of course we all know that anyways.
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This one certainly has a good record; all of the collaboratives have produced worthy outcomes.

We're pleased to have you as a satisfied M7 modder! :thmbsp:

[Now, where's the Murphy guy...? ;) ]
 
I recently joined the Minimus 7 club with a pair of thrift store 7W's. One little problem - the tweeters are dead. I don't feel like futzing around trying to find for used replacements, and so am looking for a new tweeter - which may have better performance than the old one. None I've seen has faceplate dimensions nearly equivalent to the stock tweeter.

I see favorable mention of the Aurasound NT1-204-8D titanium dome tweeter from the Zaph Audio site. It's housed in a circular barrel with a mounting flange on the back. It looks like it's just barely too large in diameter to fit in the faceplate hole for the Minimus 7 tweeter. Rather than filing or sanding the original faceplate, how about making a new faceplate out of 1/8" thick wood? Would such a faceplate be sonically acceptable ?

There's still the problem of any differences in efficiency between the new tweeter and the stock tweeter, and effects on response. Also, it looks like a lot of work has been done in modifying the crossover to improve frequency response with the stock tweeter. Would these modifications be reasonably valid with the Aurasound tweeter? Or, maybe a worthy research project for the people in this forum who are well-equipped enough to do it?

I also see mention of a Dayton tweeter that should fit in the Minimus 7 tweeter face plate. Would that be the Dayton ND20FB tweeter that looks a lot like the Aurasound?
 
I've got 3 pairs of these I've picked up over the years. All are the ported version.

One pair I use for the speakers on my Alesis synthesizer. I've always noticed a "pulsing growl" on very low notes on the keyboard due to the port. I can actually feel the air pulsing in and out!

After reading this thread I bought rubber plugs to turn them into accoustic suspension speakers, and holy cow, do they sound nicer at low frequency! Nice clear piano tone!

I think I'll buy plugs for my other two pairs. One is used for my television (with a small subwoofer) and the other for speakers in our kitchen.
 
Zilch said:
Wired:

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Lucked out again:

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So?

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CRAP! Now I gotta build another one....
attachment.php
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File
 
Zilch said:
I've completed modding the second unit, and it's clear that flattening the response and mitigating the high-frequency excesses of the stock Minimus 7 has allowed what bass they produce to balance the overall response nicely; these are eminently listenable minis now. :thmbsp:

In the course of completing the second one, I learned the following:

1) It's not necessary to remove any but the yellow woofer (+) wire to complete the mod. The other driver connections remain at the stock locations.

2) Nor is it necessary to desolder all of the terminals, so long as the lower hole in each is exposed.

Here's the layout and wiring diagram I made while doing this one:

attachment.php

Notes:

http://audiokarma.org/forums/attachment.php?attachmentid=132322&d=1233206613

http://audiokarma.org/forums/attachment.php?attachmentid=132323&d=1233206613

a) A cable tie secures the 3-Ohm resistor to the stock aircore inductor.

b) A short piece of wire (blue) connects IN (-) to the junction of the 40-Ohm resistor and 4.7 uF capacitor, lower right.

c) All other connections are made using the respective component leads.

d) The large inductor lead and tweeter wires dress neatly through the center of the stock aircore.

e) A #4 solder lug installs on the existing plastic boss, upper right.

f) Drill the rear panel to mount the large inductor between the two bosses on the inside centerline using #4 machine screws from the outside.

g) Double-stick foam tape secures the two caps and bottom two resistors to the stock input terminal plate/cup. Epoxy and other glues are suitable alternates.
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File
 
I used the surplus crossover from Apex Jr. that Pete had mentioned. Unwound a couple turns from the coil and then performed the mod.

Happy as ever that these are now listenable with a sound that my wife described as much more refined. She normally doesn't care about sound.

Thank you guys.
 
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