"The Minimus" Project

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  • VR3
    VR3 Posts: 24,686
    If you could get me perfect nhung measurements, I can cut that all day 😁
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • F1nut
    F1nut Posts: 46,139
    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.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • gp4jesus
    gp4jesus Posts: 1,706
    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
    Samsung 60" UN60ES6100 LED
    Outlaw Audio 976 Pre/Pro
    Samsung BDP, Dish Rcvr, Phillips CD chgr, various game consoles

    Canare 14 ga - LCR tweeters inside* & CC outside
    BJC 10 ga - LCR mids, inside* & out
    8 ga Powerline - LR woofers, inside* & out
    *soldered

    LR: Tri-amped RTi A7 w/Rotels. Woofers - 980BX; Mids & Tweets- 981
    CC: Rotel RB981 -> Bi-amped CSi A6
    5 Subs: Sunfire True Sub Signature -> LFE & CC & 4 Audio Pro Evidence Subs
    Surrounds: Rotel 981 -> AR 12 ga -> RTi A3
    Power Conditioning & Distribution:
    3 dedicated 20A feeds; APC H15; 4 Furman Miniport 20s
  • VR3
    VR3 Posts: 24,686
    Made a custom mount for a barrier strip (with a little modification) to go external. Will combine the ground to one output

    h5hrnaprmlox.jpg
    deyilfpoghva.jpg
    huf2jnlmy7y5.jpg
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • VR3
    VR3 Posts: 24,686
    edited March 13
    Dh labs t14 internal wiring, direct soldered
    Filled enclosure with polyfill
    ygoaanhf8hjs.jpg
    0j3mg8qok43q.jpeg
    ge2uu2ucxjzc.jpg
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • VR3
    VR3 Posts: 24,686
    All mods up to this point, with diffraction pads, at the listening position
    pv0rbyie5w6r.png

    No diffraction pads
    eid42fe8zzd9.png

    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • BlueFox
    BlueFox Posts: 14,687
    So it is basically indistinguishable between the two?
    Lumin X1 file player; Sony XA-5400ES SACD; Pass XP-22 pre; X600.5 amps
    Magico S5 MKII Mcast Rose speakers; SPOD spikes

    Shunyata Triton v3/Typhon QR on source, Denali 2000 (2) on amps
    Shunyata Sigma XLR analog ICs, Sigma speaker cables
    Shunyata Sigma HC (2), Sigma Analog, Sigma Digital, Z Anaconda (3) power cables

    Mapleshade Samson V.3 four shelf solid maple rack, Micropoint brass footers
    Three 20 amp circuits.
  • VR3
    VR3 Posts: 24,686
    edited March 14
    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
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • VR3
    VR3 Posts: 24,686
    edited March 14
    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.

    7kv8xcy1a6g6.jpg


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

    8qzy556kqcnh.png
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • mhardy6647
    mhardy6647 Posts: 27,930
    edited March 14
    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
    xschop Posts: 2,020
    Looks like an improvement for sure. What is the x-over point?

  • VR3
    VR3 Posts: 24,686
    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
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • Gardenstater
    Gardenstater Posts: 1,997
    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?
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    Logitech Squeezebox Touch Streamer w/EDO applet
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  • VR3
    VR3 Posts: 24,686
    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
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • gp4jesus
    gp4jesus Posts: 1,706
    edited March 14
    VR3 wrote: »
    All mods up to this point, with diffraction pads, at the listening position
    pv0rbyie5w6r.png

    No diffraction pads
    eid42fe8zzd9.png
    I see a small diff/improvement at 4.5 K - one of the frequencies that tends to annoy
    Samsung 60" UN60ES6100 LED
    Outlaw Audio 976 Pre/Pro
    Samsung BDP, Dish Rcvr, Phillips CD chgr, various game consoles

    Canare 14 ga - LCR tweeters inside* & CC outside
    BJC 10 ga - LCR mids, inside* & out
    8 ga Powerline - LR woofers, inside* & out
    *soldered

    LR: Tri-amped RTi A7 w/Rotels. Woofers - 980BX; Mids & Tweets- 981
    CC: Rotel RB981 -> Bi-amped CSi A6
    5 Subs: Sunfire True Sub Signature -> LFE & CC & 4 Audio Pro Evidence Subs
    Surrounds: Rotel 981 -> AR 12 ga -> RTi A3
    Power Conditioning & Distribution:
    3 dedicated 20A feeds; APC H15; 4 Furman Miniport 20s
  • VR3
    VR3 Posts: 24,686
    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.
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • mhardy6647
    mhardy6647 Posts: 27,930
    VR3 wrote: »
    ...
    The woofer is full range and the tweeter is a simple 2nd order at 2khz

    I was gonna ask :p -- 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
    skrol Posts: 3,093
    edited March 14
    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.
    Stan

    Main 2ch:
    Polk LSi15 (DB840 upgrade), Parasound: P/LD-1100, HCA-1000A; Denon: DVD-2910, DRM-800A; Benchmark DAC1, Monster HTS3600-MKII, Grado SR-225i; Technics SL-J2, Parasound PPH-100.

    HT:
    Marantz SR7010, Polk: RTA11TL (RDO198-1, XO and Damping Upgrades), S4, CS250, PSW110 , Marantz UD5005, Pioneer PL-530, Panasonic TC-P42S60

    Other stuff:
    Denon: DRA-835R, AVR-888, DCD-660, DRM-700A, DRR-780; Polk: S8, Monitor 5A, 5B, TSi100, RM7, PSW10 (DXi104 upgrade); Pioneer: CT-6R; Onkyo CP-1046F; Ortofon OM5E, Marantz: PM5004, CD5004, CDR-615; Parasound C/PT-600, HCA-800ii, Sony CDP-650ESD, Technics SA 5070, B&W DM601
  • VR3
    VR3 Posts: 24,686
    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

    1vj91xf1ge2g.jpg
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • VR3
    VR3 Posts: 24,686
    kncvzwgx9b2h.jpg
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • ken brydson
    ken brydson Posts: 8,155
    VR3 wrote: »
    kncvzwgx9b2h.jpg

    Guessing it needs to be a bit out from the wall? Lol...
  • VR3
    VR3 Posts: 24,686
    😜

    Big ol coil! Sounds excellent though, from 100hz upx it easily outperforms the definitive monitors I have
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro
  • JayCee
    JayCee Posts: 1,237
    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!
    Speakers: Polk1.2tl's (Uber Mods) Pre/Amp/DAC: PS Audio BHK Signature & 250, DirectStream Cables/IC's: MIT S1Bi-Wire/S1 Balanced +Avel Lindberg 1000VA "Dreadnought" Power Conditioner: PS Audio P15 Power Plant Power Cords: Core Power Technologies Gold, DH Labs Power Plus DIY w/Neotech NC-P301 & P311ends Streamer: Roon ROCK on wifi'd NUC & Uptone EtherREGEN, AfterDark, Emperor Double Crown Clock, Black Modernize LPS⟿Ω☯☥☮⟿🔊♩♪♫♬♩♪♫♬♩♪♫♬
  • VR3
    VR3 Posts: 24,686
    edited March 27
    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
    - Not Tom

    "No, that's silly talk. Dude, you can't possibly be this audio dumb so quit the act." - Doro