"The Minimus" Project

VR3

So a buddy of mine is knee deep in the old Realistic Minimus 7s which can be had for approximately $50 bucks on EBay. There are many different iterations but apparently the ones with the metal tweeter faceplate are most desirable.

There is a mod that flattens the response to these called the "Zilch Mod"

https://www.lostinsound.space/minimus-7-upgrade/

So this is my chronicle of fun with the Minimus 7.

First step is anti-diffraction inserts!

More to come as I go! :-P

gp4jesus

Cool!
Where to buy the felt?

F1nut

Ha, I had a "desirable" pair that I took to the dump instead of trying to sell and I have no regrets.

mhardy6647

The late "zilch".
More on the Minimus 7 from the man himself at

I am in the same camp as @F1nut, FWIW -- Radio Shack's Visonik/ads ripoffs just... weren't... great. I do still have a pair but it's completely nostalgia-driven. I am sure Zilch's mods make 'em better, for as Paul McCartney wrote (a long, long time ago) can't get no worse.

https://audiokarma.org/forums/index.php?threads/minimus-7-loudspeakers-measurements.199790/

VR3

I can say without question the anti-diffraction pad alone completely transforms the sound. Those edges for the grill to grip are a nightmare!

I have been enjoying them nearfield, I imagine they would fall apart in a larger room (maybe).

This felt/wool combo is from Madisound

JayCee

I have a pair that were thrown in as a give-me when I bought my CRS's. Use them w/a $20 Goodwill find Onkyo receiver in the garage. Provide the needed background music for shop projects, bier drinking and throwing darts. Looks like a fun project. Interested in your impressions, Trey.

VR3

It is definitely a fun project!

Will keep this thread updated 😜

pitdogg2

Duelands on a RS speaker???
Boy you've lost your mind


You're knocking it out of the park with these wood projects 👍

VR3

I KNOW RIGHT? This is a purely "fun" project! That blue cactus capacitor is a paper and oil cap, supposed to sound suh-weeet!

Gracias!

mhardy6647

How did you tattoo the anti-diffraction mat? That is exceptionally cool.

VR3

The laser at reduced power was able to "engrave' it instead of cutting through

gp4jesus

You used a laser to cut openings in the felt?

xschop

Do I see custom laser-cut tweeter gaskets in the future?

VR3

Yes the felt was cut with a laser.

Hmm, I know @F1nut had a material he found that I could totally cut on the laser!

VR3

Dynamat! Had just enough left over

skrol

I have had 3 pairs of the Minimus 7. The metal enclosure makes them very solid and seem somewhat impressive initially. My first was back in the late 80's and I was playing around with them for cross talk cancellation, messing with phasing. Then I discovered Polk Audio had already done this with the SDA. I sold them to a friend.

Knowing they have had a cult following, I recently bought a couple few pairs of different versions for about $20 / pair including that latest with the port on the back. To be honest, I don't get the fascination with these speakers. They aren't bad but really not that impressive. I may try the mods to see if I can make them sing.

VR3

If you do nothing other than fix the diffraction issue you will see a good gain. The baffle is a joke! Fix this and you may like them a lot more.

schwarcw

Polkie TNRabbit (RIP) did a crossover upgrade to a pair of Minimus 77s. He replaced the woofer and modded the front baffle. I think the crossover design was the product of an ad lib crossover design project on AudioKarma some years ago. The 77s sound real nice and I use them in my computer system every day. I get the power powered by a Fisher X-1000 integrated amplifier.

JayCee

@VR3 Just came back in from my garage. Was putting some stuff up and looked up, eye level, and the 7's said, "Come on man, give me some felt."

So, how 'bout making me a pair and adding to the tweeter order/ship in the same box? PM me total cost for both orders and I'll send payment when you want.

VR3

No problemo, will Pm you in a bit.

You will be surprised, really balances it out, especially considering it is just felt!

JayCee

Thanks.

gp4jesus

@VR3 would you consider cutting felt for any
RTi A series speakers?

Thanks either way

VR3

Yes, I actually have some cut that should work given the slim faceplate. Can you send me dimensions height and width?

skrol

VR3 wrote: »

If you do nothing other than fix the diffraction issue you will see a good gain. The baffle is a joke! Fix this and you may like them a lot more.

Perhaps I'll give it a try. I think I might even have some similar material. Are you leaving grills off after the material is applied?

skrol

I have a friend who used to work for Polk Audio back in the later 80's early 90's (ZSP) and worked on the Monitor Series 2, RTA (TL) SDA (TL) and S series. When I asked him about tweaks for my RTA11TL's he mentioned that they played around with putting felt around the tweeters but didn't get much benefit. Perhaps this material is better suited? It certainly looks more absorptive than regular felt.

mhardy6647

That's interesting. A very early tweak suggested for the (Peerless!) dome tweeters in the Monitor Series Polks was to put a ring of felt or even cotton around the dome.

I honestly don't remember when or where I heard/read that suggestion -- but it was a long, long time ago (probably before 1980).

Gardenstater

Oh .......so now you mention it.....finally!

I think that the baffle rout-outs (is that a word?) are a bit oversized and that groove will cause a diffraction resulting in a 180deg out of phase waveform that is approximately at a frequency of: Speed of Sound/distance from center of dome to the groove. I figure maybe a range of 2600 Hz to 6000 Hz for the horizontal waves. That can cause a trough in the output of the tweeter response at those frequencies. It would be MUCH worse if the tweeter bezel were a circle with a groove around it. I may fill mine with some brown modeling clay (can you get black?), in addition to the felt pads.

VR3

I keep the grills on since my pad fits perfectly snug in place

Black modeling clay, an enigma!

gudnoyez

Interested on what the results are on the RTIA's are if someone tries them out.

Gardenstater

VR3 wrote: »

I keep the grills on since my pad fits perfectly snug in place

Black modeling clay, an enigma!

Yes. My biggest fear, that keeps me lying awake at night, is that it may be even harder to find than black paint!

gp4jesus

gudnoyez wrote: »

Interested on what the results are on the RTIA's are if someone tries them out.

I’m game to try. Been thinking about this on my RTi A7s and my ‘A6 center.

Correct me if I’m wrong w/ my “A7” thinking. Focus on the baffle to the edges all around the tweeter, from the top to the top of the mid, extending to the 3 & 9 o’clock positions around the mid would be a great start. Could as far as the 5 & 7 o’clock positions - but ~ an 1” below mid is a port.




For A6 center - similar thinking sideways: Below the tweeter an opening for the port. 6 &12 o’clock positions around the mids.




I realize the challenge for someone doing the trimming or (laser cutting) is very precise measurements

Thoughts?