"The Minimus" Project

VR3

If you could get me perfect nhung measurements, I can cut that all day 😁

F1nut

skrol wrote: »

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.

I'm not surprised as the raised bezel on the SLxxxx/RDOxxx tweeters already addresses the diffraction issue. Years ago in an attempt to tame the SL2000 I tried purpose made diffraction pads. They didn't do a damn thing because the real problem lay elsewhere.

gp4jesus

VR3 wrote: »

If you could get me perfect nhung measurements, I can cut that all day 😁

you’ve proven again you are bigger and better😊.

At the moment I’m taking advantage of the gorgeous N GA spring weather doing battery maintenance on my small fleet of cars, vans, and SUVs.

Taking a close look @ the tweets...

they’re exactly 1” in diameter, very slightly horn loaded though I’m sure all will agree that tweeter demands we cover those shiny surfaces!

From your pics I see you can get very precise. I suppose just tiny fraction larger than an inch should do it allowing the felt to appear to horn load the tweeter. In the interest of simplicity I may go basically square*/rectangular** from the baffle top to the mid top*/side edges**.
*A7s **A6

Taking a close look @ those mids...

Before I start measuring, should I allow the silver trim ring* exposed? It* does horn load the driver just slightly. Mostly it makes them look pretty.


Perhaps I could attempt a template for the center. Either way advise me on the A6 tweeter/port arrangement.

Both speakers front baffles are, I think, 8 3/4” across (A7) or high (A6). I’ll get back to ya w/the details.

Please PM an e$timate to me. One day I may do the same for my ‘A3 surrounds.

1000 thanks in advance for even considering doing this. Perhaps a simple tweak for the so many other speakers using that tweeter

VR3

Made a custom mount for a barrier strip (with a little modification) to go external. Will combine the ground to one output

VR3

Dh labs t14 internal wiring, direct soldered
Filled enclosure with polyfill

VR3

All mods up to this point, with diffraction pads, at the listening position


No diffraction pads

BlueFox

So it is basically indistinguishable between the two?

VR3

I wouldnt say there isnt a difference, with the pads on it is almost ruler flat from 300hz to 1.5khz versus some peaks and valleys and a reduction in peaks in other parts of the graph

This is a desk setup so nearfield

VR3

For comparison sake, this is the Definitive PowerMonitor500 at the same listening position (PM 500 has an 8" powered sub per speaker, 4.5" midrange, 1" tweeter.




No where near as flat, but also not saying the Minimus 7 sounds better or worse. No comment on that yet haha

mhardy6647

VR3 wrote: »

I wouldnt say there isnt a difference, with the pads on it is almost ruler flat from 300hz to 1.5khz versus some peaks and valleys and a reduction in peaks in other parts of the graph

This is a desk setup so nearfield

I'd expect the smoothing out of that hump from 2 to 4k would be both audible and quite beneficial

Also, it would be interesting to look at the frequency-dependent dispersion pattern sans and avec the baffle matting. That would probably show substantial alteration (I would think) -- again, with significant audible consequences in terms of "transparency" of the sound. I always found the Minimus-7 (and most R/S loudspeakers of the 1970s into 80s) to be quite opaque sounding -- as in "not transparent". The source of the sound, from most of them, was often blatantly obvious; the speakers call attention to themselves "as is".

The mod, apparently, improves that substantially, based on early posts to this thread.

xschop

Looks like an improvement for sure. What is the x-over point?

VR3

That frequency response at the listening position is crazy because that's still the stock "crossover". As I am waiting on parts.

The woofer is full range and the tweeter is a simple 2nd order at 2khz

Gardenstater

I think without so much smoothing, the differences between w/ diffraction pad and w/o would be even more apparent. That is a very real improvement though!

What's with the hump in freq. resp. at around 28 Hz? Is that from the fact that you're not testing in an anechoic chamber?

VR3

I believe that 28hz is the room doing something. When I listen to music, there is some definite low bass that makes no sense given what they are. One speaker is pretty close to a corner and the other is pretty far away from other boundaries other than the back wall

gp4jesus

VR3 wrote: »

All mods up to this point, with diffraction pads, at the listening position


No diffraction pads

I see a small diff/improvement at 4.5 K - one of the frequencies that tends to annoy

VR3

Indeed, I am also using a revised, oval, diffraction pad versus the round one at the start of the thread.

So the effect is far different, I will cut one with a round cut out next time I'm doing runs to compare.

mhardy6647

VR3 wrote: »

...
The woofer is full range and the tweeter is a simple 2nd order at 2khz

I was gonna ask -- although, that was my recollection. Kind of a funny configuration when running a woofer fullrange, i.e., it was more common to use first order on the tweeter with an un-throttled woofer (a la EPI's "Burhoe Modules"). I guess that whomever designed the Minimus-7 was trying to protect the tweeter near its Fs by using a second order XO.

skrol

This is a neat project and I'll probably try some of this on my 7's as I'm kind of into making lowly or old stuff perform better than it was meant to.

I see you are experimenting with round vs oval cutouts. Have you considered different texturing? For example, rather than a flat felt surface, concentric channels around the tweeter or other patterns. Kind of like acoustic panels to trap the sound as some may still be reflecting off the flat felt surface. I assume this could be done with the laser.

VR3

I'm trying something like that with my utopias right now

Getting to fancy with the laser adds considerable time to its operation. It cuts at the size of the human hair, so getting crazy can add hours to a print

Hansvelton

Some other measurements......

http://murphyblaster.com/content.php?f=minimus.html

VR3

ken brydson

VR3 wrote: »

Guessing it needs to be a bit out from the wall? Lol...

VR3

😜

Big ol coil! Sounds excellent though, from 100hz upx it easily outperforms the definitive monitors I have

JayCee

Seeing, in the pic you posted, what the LSi "flame" resistor did to the cap it was mounted on....no worries w/the wood board and heat? Duelund's alone...plus, those have to be the most tricked out Minimus 7's on the planet!

VR3

Nah, I don't see it causing any issues. The burning point for wood is around 400 plus degrees.

The problem with mounting the caps next to the resistors is that the poly film starts to melt and shrink and it just gets nasty from there!

The cap you see in the photo is enclosed in an aluminum tube

Thank you! They do sound great too, dissappear well, great staging and neutral tonality. Great for a desk setup

skrol

Thread resurrection... So my home office has moved from our sun room to a small room where I can freely listen to my music. I've been auditioning different small speakers in my collection for a desktop system including a pair of LSi7. The setup doesn't do the LSi7s justice with a Parasound Zpre2/Zamp2 and they are too close to me and the back wall. I dug out some Minimum 7s and am actually enjoying them. That of course has me thinking that maybe I would enjoy them more with some mods. Also could use a little sub.

Have you done anything more with the Minimus 7 Project?

VR3

I sold my set but I sell alot of the diffraction pads.

The zilch mod is a must!!

Great speakers for the $$$

skrol

I may be interested in the pads.

I also found a pair of LX5ii with the Linaeum bipolar ribbon tweeters hiding in my basement. The imaging always gets me. I’m getting lost listening to some old Genesis. However, the bass sounds like dung. Helps to stuff the ports. There are mods out there for these but probably better to scavenge the tweeters for a DIY project.

skrol

I received the anti-diffraction pads for the Minimus 7s today and look forward to trying them out.

Trey, are these things made from hemp? They kind of smell like somebody tokin' . I thought my son was ordering stuff off the internet or something.

VR3

Lol, burnt hair smell from the laser 😁