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Minimus 7 Loudspeakers - Measurements

Zilch,

Is blue (turquoise) what Pete recommended? Grey is stock?

Looking much flatter anyway.

This mod has some serious potential as so many Minimus 7s are still out there. Probably many will not care though but very cool, nonetheless.

I'm really excited by the prospect of a better sounding Minimus 7. I never really heard the magic in them but use "double Minimus 7s" every day (side by side and wired in parallel) as my computer speakers via an Accurian.
 
Robie said:
Is blue (turquoise) what Pete recommended? Grey is stock?
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It's a mod of Pete's mod. Yes, grey is stock. The difference is certainly not subtle.

I just want to kerfutz a bit more with it, and then I'll post the details of both, later today, probably; gotta draw up schematics and stuff.... :thmbsp:
 
Zilch, as Ray has observed before, "you the man."

BTW, glad you're "kerfutzing." Wish I could do more than "kibitz."
 
Zilch said:
Very nearly:

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PB-1 had a smoother response 10 to 30 deg above the top of the enclosure IIRC so that if placed on a desk or another speaker ( say a LA for example) then the main lobe points up as it should.
 
these are not minimus 7's but are similar.they handle much more power and sound great for little guys. 8.5in tall,5.5in wide and 4.5in deep and aluminum housings.
 

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Ooooo! Those are some nice curves compared to stock or even the ebay mod. Can you characterize the sonic differences betw the "B" version and the "Z" version. Also wondering if it's worthwhile specifically going after rise/peak @~4KHz with added parts count or other means.
 
skywave-rider said:
I gotta get the parts, that must be night and day.
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I'm running with 2.0 mH right now, 'cause there is no 1.8 mH I-Core from PE. The P-Core is pretty big to be stuffin' in Minimus 7.

The 2.0 mH I-Core could be uwound to 1.8 mH, OR order 1.8 mH from ERSE direct, also an AK sponsor. Gotta order for two pair to meet their minimum, though.

The small inductor is the one already in the Minimus, as Pete suggests.... :thmbsp:


RayW said:
Bravo, gents!
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Thanks, Ray!

After hearing your Mod #1, I was determined to get there with a lower parts count, and Pete pointed the way. :yes:


Steve O said:
Ooooo! Those are some nice curves compared to stock or even the ebay mod. Can you characterize the sonic differences betw the "B" version and the "Z" version. Also wondering if it's worthwhile specifically going after rise/peak @~4KHz with added parts count or other means.
Click to expand...
I think a notch will get the 4 kHz peak substantially flatter yet, but I'm reluctant to add more parts in this tiny box. Looks like we're +/- ~2 dB right now. If I were to try that, it'd be with Pete's original circuit, most likely, as it's already flat from there up.

"Z" version is less sibilant (Peter Gabriel, "Red Rain") than any of the others; I'll have to build up a second one to know how good this really is. Others are just gonna have to do the same; they may hate it, or perhaps we can all just shut up with the "flat response sucks" thing.... :dunno:


Edit: The aftermath, assuming it's over. ;)

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[Indignia, left, Presidian, rear.... :) ]
 

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Zilch said:
<snip>​

I think a notch will get the 4 kHz peak substantially flatter yet, but I'm reluctant to add more parts in this tiny box. Looks like we're +/- ~2 dB right now. If I were to try that, it'd be with Pete's original circuit, most likely, as it's already flat from there up.

"Z" version is less sibilant (Peter Gabriel, "Red Rain") than any of the others; I'll have to build up a second one to know how good this really is. Others are just gonna have to do the same; they may hate it, or maybe we can all just shut up with the "flat response sucks" thing.... :dunno:
Click to expand...

I was just catalog surfin' and was really surprised at how physically large a 1.5-2mH inductor is regardless of wire gauge or core. I'm still wondering how much the internal volume can be reduced w/o affecting the "low end". Since every M7 I've seen has four threaded holes on the back plate for mounting brackets, maybe an outboard xover board is the way to go with something like this. Or are there tiny, large value inductors out there?

P.S.

I for one wouldn't worry about the "flat response sucks" thing. That's why all good amps have tone controls.
 
Steve O said:
I was just catalog surfin' and was really surprised at how physically large a 1.5-2mH inductor is regardless of wire gauge or core. I'm still wondering how much the internal volume can be reduced w/o affecting the "low end". Since every M7 I've seen has four threaded holes on the back plate for mounting brackets, maybe an outboard xover board is the way to go with something like this. Or are there tiny, large value inductors out there?
Click to expand...
There are smaller, but the quality goes down. Laminated I-Core is already a compromise.

Frankly, I'm not much concerned about the bass response. These need subs; there's no getting around it, anyway. There was allegedly a matching sub, and if somebody who has one would step forward with some info, that'd certainly be helpful.... :thmbsp:
 
I spent about 2 hours on this mod, maybe 2 more listening to it. I don't remember the peak in the lower end of the tweeter but then I wasn't taking a lot of measurements. Could try reducing the cap to say 1 or 1.5 uF then reducing the resistor to bring the 5 to 7 kHz level back up, would have to recheck that the drivers are in phase at the crossover point and that the lobing is still acceptable.

Something like the Large Advent woofer inductor would work fine, even a higher gauge wire say as high as .7 ohms DCR, but they're hard to find.
Found this company but have not ordered from them. I'd like a bar type, however they don't have a 1.5 or 1.8 mH in the bar type:
http://www.chokes.com/ferrite.htm
I do not normally suggest iron core types, however we need small for this application and the power is low so it should be fine. I prefer the laminated iron core type, but again not much to choose from.

These caps are fine and inexpensive:
http://www.madisound.com/catalog/index.php?cPath=404_5_12
 
skywave-rider said:
Great!
I gotta get the parts, that must be night and day.
Click to expand...

It is clear that the original design went for loud with minimal power, and therefore none of the driver resonances were dealt with, and little was done to provide a balanced FR. What is night and day is that in order to provide some bass the mid and treble is now attenuated by about 5 to 8 dB so the system will sound much less sensitive, but far better balanced and natural sounding. Also, the woofers are going to run out of steam without the system sounding loud because we've knocked down the mid and treble so much without providing more bass output. I expect that people who know and like good sound will like the mod, those who just want or need volume will likely not. I would need a sub with these for any serious listening.

I actually experimented with a 2.0 mH inductor but felt that too much sensitivity and max SPL was lost - the 1.5 mH value is a compromise.

I would simply replace the tweeter rather than provide a notch on the tweeter circuit.
 
Stuffing

Mine have about a 1" layer of fiberglass toward the back of the enclosure. I would make this twice as thick, say 2" and I would completely fill directly in back of the tweeter but not the woofer. This will maximize what little enclosure volume there is and attenuate any cavity resonances.

Keeping the material away from the woofer will avoid lowering the system Qtc and loosing more bass.
 
Thanks, Pete.
What you say makes sense.
I noticed chokes dot com says all custom windings are available, but it would take a phone call at business hours to get a price.
http://www.chokes.com/ferrite.htm

I don't remember seeing the RS sub for these.
Would make a good 2.1 HT or music secondary system.
I'd like to put mine in the kitchenette.
 
Yes, I agree that they do make a lot of sense in secondary applications.

I think that they'll wind their other types but I'm not sure if they'll go any higher than 18 ga for those. Could use two .75 mH bar types in series (or wind it up), or wind down the 2.0 mH (21 ga) bobin type from that page.

Don't know of a good sub for these, will have to start looking around for one.
 
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