Second Monitor 7 project.

Got these back from Jeff at Sonic Craft the other day. Thought he did a beautiful job!fmxbp1u94tto.jpg
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Comments

  • xschop
    xschop Posts: 2,050
    Slow down, I haven't even gotten to my 1st Monitor 7 project.

    Looks good.
  • Gardenstater
    Gardenstater Posts: 2,026
    edited January 14
    It looks like quality workmanship. What did he use for the black goo (?); I ASSume that is probably as hard to find as black paint is :D What wire did he use for you?

    Did these XO's originally have a fuse block, which he took out/eliminated? If so, did he add 0.2Ohm to the resistor to compensate, since the cold DCR of the fuse is 190 mOhms? What MW# drivers and tweeters are you using with these XO's?

    I like the over/under solution he went with and I see he used some longer hex nylon standoffs with nylon screws (?) and black goo on the heads.
    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
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • I am not sure about any details I am embarrassed to say. The wire is some type of wire which has insulation on each strand I think. The wiring harness I chose was on the high end and the price jumped significantly. I wish I knew more. These were out of the first 7bs I owned, the one in my first thread. The drivers are.MW-6502, one which is original.

    My goal is to compare, by my ear, the first upgrade with the $200.00 build compared to this which was three times that. If my old construction ears can't tell much difference I will know which direction to go on the next project.

    Any more comments are welcome. Thanks for the large amount of time you invest here.
  • Oh, they had the external fuse.
  • Gardenstater
    Gardenstater Posts: 2,026
    If you have the same crossover network as I have in my 7B's and it is paired with a Peerless Tweeter and a 3.52 Ohm DCR MW6502 (not a 6.5 Ohm DCR MW6500?), well all I can say is somethin' darn sure don't seem right about that. That's all I'll say because I don't want to be redundant or a nuisance. I hope they sound good to you. That is the ultimate test.
    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
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
  • skrol
    skrol Posts: 3,096
    Cool, that is a nice way to do it instead of adding another board.
    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
  • whoban72
    whoban72 Posts: 4
    Looks really good, I just snagged a pair of 7's although I haven't identified them fully. Gives me a couple ideas, thanks for posting.
  • The caps and resistors were only $116.55 per XO. The $192 bump was for the labor of cleaning, repairing, modifying, building harnesses, and additional parts. We used top of the line binding posts (not brass), Cardas litz wire, cable sleeving, etc... I projected and charged for 3 hours per XO, but ended up with ~10 hours for the pair. That pair alone required end prep and tinning of 36 ends. The cable sleeving is sonically superior to other sleeving. Far more resilient, but it does not expand easily. Beautiful, but hell to work with.

    I think the driving factor behind the works package was the extremely poor condition of the assemblies to start with. Rotten fuse holders, broken post, separated cup, cut harnesses... It takes time to repair those things... Why would you repair it with crap? Hopefully, the cash discount helped ;)

    Middle of winter, and Covid...my tech is slammed, so I actually did these. I haven't physically modified XOs in ~13 years, and no Polks in maybe 18 years... Meaning it could have been a bit better. His second pair were much better sorted and executed.

    The black stuff is hot melt. I used it everywhere as I am just finishing an evaluation of the product. Black was only necessary for sealing the 3 fuse block holes. The nylon stand offs were 4-40. The end connecting to the board was studded. It was fastened with a substantial nylon nut, but I did not like the nylon screw that fastened the other end to the cup. The head seemed weak, so I replaced them with brass screws. On his second set, I went to a 6-32.

    The tweeter harness is Cardas 17.5g litz, and the woofer is Cardas 15.5g litz. I did not increase the 4.5 Ohm tweeter pad to 4.7 Ohms because most seem to prefer no compensation on this speaker. A minority actually like a little more than 4.7, but I attribute this to room response, and/or system synergy. Either way, it can be adjusted after the complete system is sorted, and the speakers have had 350 hours of burn-in.

    Below are our before and after pics.
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  • Mystery
    Mystery Posts: 2,543
    Nice work!

    Sonus Faber Concerto Grand Piano, Klipsch, B&W DM602.5, Epicure 20+, T/E 280, 100V, Polk.
    Subwoofers: Monitor Audio, B&W ASW300, Triad ProSub Bronze.
  • Thanks doing more than just answering the few questions Jeff. I appreciate you spending so much time on those with limited funds and people with no knowledge of electronics! I hope to have these in boxes and working in the next couple months. I have a pair of SDA-1 headed your way next week! The savings were a blessing and extremely appreciated! I hope it was worth your while.