Monitor 10b xover rebuild.

sansuibutchsansuibutch Posts: 141
edited March 5 in DIY, Mods & Tweaks
Im rebuilding the the crossover on one of these speakers. I purchades one monitor 10b crossover so this is not a set of speakers. Its going to be used in a center channel " a design westmassguy created and awsome he shared with us all" . The parts of the crossover for the tweeter are going to be the same specs just new caps and resistors. I notice the tweeter circuit has a inductor, couple caps and a couple resistors. The schematic i see calls for a 2 ohm resistor and a 2.7 ohm resistor. My xover from the factor has two 4 omh five watt resistors in parallel to get the 2 ohm with 10watt rating. But the other resistor is a 2.5 ohm 5 watt resistor when it looks like it should be a 2.7 ohm. Was there any variations of the monitor 10b xover to make sense of this or do you guys think they were just out of 2.7ohm resistors?

Answers

  • westmassguywestmassguy Posts: 6,625
    The 2.7 ohm resistor is used to pad the bypass circuit and should be left as is. The 4 ohm should be replaced with a .7 ohm resistor as outlined in my thread. The woofer leads must be modified from parallel to series, if you're using two MW6502 woofers.
    Home Theater/2 Channel:
    Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
    Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
    Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
    Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
    Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer
    Cables: Speaker: Furez 10/2 with GLS Locking Banana Plugs
    Interconnect: Furez 10/2 with SpeakONs
    ICs: Custom Furez by Douglas Connections
    Den:
    Bose 901 Series II Continentals Restored, Re-Built Equalizer with Elna Silmic IIs, Sonicaps, and Silver Mica Caps
    Carver CT-3 Pre, Carver C-500

    dhsspeakerservice.com/
    Exclusive Distributor of Gimpod's Custom SDA Circuit Boards

    "And keep her under 70, would you, huh? Betty likes a slow ride"
  • sansuibutchsansuibutch Posts: 141
    The 2.7 ohm resistor is used to pad the bypass circuit and should be left as is. The 4 ohm should be replaced with a .7 ohm resistor as outlined in my thread. The woofer leads must be modified from parallel to series, if you're using two MW6502 woofers.

    My 10b crossover does not have a 2.7ohm resistor. In your thread i asked you if replacing parts of the high frequency was for modding for the rdo198 or for matching tweeter and woofer output, you said it was for the mod. Now im confused ahahahah.
  • westmassguywestmassguy Posts: 6,625
    The 2.7 ohm resistor is used to pad the bypass circuit and should be left as is. The 4 ohm should be replaced with a .7 ohm resistor as outlined in my thread. The woofer leads must be modified from parallel to series, if you're using two MW6502 woofers.

    My 10b crossover does not have a 2.7ohm resistor. In your thread i asked you if replacing parts of the high frequency was for modding for the rdo198 or for matching tweeter and woofer output, you said it was for the mod. Now im confused ahahahah.

    Sorry, teachable moment or cautionary tale...
    Never post before your brain is fully awake.
    I mistook the sandcast resistors and blue electrolytic cap as originals.
    I see now what you did.
    I"ve never seen a 2.5 ohm resistor in the shunt circuit, it's always been 2.7 ohm.
    Home Theater/2 Channel:
    Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
    Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
    Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
    Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
    Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer
    Cables: Speaker: Furez 10/2 with GLS Locking Banana Plugs
    Interconnect: Furez 10/2 with SpeakONs
    ICs: Custom Furez by Douglas Connections
    Den:
    Bose 901 Series II Continentals Restored, Re-Built Equalizer with Elna Silmic IIs, Sonicaps, and Silver Mica Caps
    Carver CT-3 Pre, Carver C-500

    dhsspeakerservice.com/
    Exclusive Distributor of Gimpod's Custom SDA Circuit Boards

    "And keep her under 70, would you, huh? Betty likes a slow ride"
  • sansuibutchsansuibutch Posts: 141
    The sandcast resistors and blue cap are original. I plan on replacing them with same value except for the 2.5ohm will be a 2.7 ohm. I just found it interesting that the schematic and every other 10b crossover used a 2.7ohm resistor.
  • pitdogg2pitdogg2 Posts: 16,303
    Well they did have a 10% variance so the .2 meant little in the grand scheme.
  • sansuibutchsansuibutch Posts: 141
    pitdogg2 wrote: »
    Well they did have a 10% variance so the .2 meant little in the grand scheme.

    Ya i figured you would need golden ears to hear the difference. And those sand cast resistors suck as it is. Either way il replace it with a 2.7 just to keep it on par with the project. I might have to make some minor adjustments when all said and done but that doesnt bother me. Pretty excited to get this center done as ive wanted one voiced like my polks for a couple years now.
  • westmassguywestmassguy Posts: 6,625
    I ended up using a small 15 watt LPad in place of the Polyswitch. I found .7 ohms to be perfect for my taste, but you can play with that value. I mounted it right inside the binding post
    Home Theater/2 Channel:
    Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
    Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
    Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
    Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
    Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer
    Cables: Speaker: Furez 10/2 with GLS Locking Banana Plugs
    Interconnect: Furez 10/2 with SpeakONs
    ICs: Custom Furez by Douglas Connections
    Den:
    Bose 901 Series II Continentals Restored, Re-Built Equalizer with Elna Silmic IIs, Sonicaps, and Silver Mica Caps
    Carver CT-3 Pre, Carver C-500

    dhsspeakerservice.com/
    Exclusive Distributor of Gimpod's Custom SDA Circuit Boards

    "And keep her under 70, would you, huh? Betty likes a slow ride"
  • sansuibutchsansuibutch Posts: 141
    I ended up using a small 15 watt LPad in place of the Polyswitch. I found .7 ohms to be perfect for my taste, but you can play with that value. I mounted it right inside the binding post

    I used a .5 ohm resistor in place of the polyswitch. I have a .75 ohm one incase the tweeter is to loud.
  • sansuibutchsansuibutch Posts: 141
    I mounted it between the board and original low end inductor. I left a few inches of wire on each end of it so i can still pull the board off far enough to get in there and replace it if need be
  • sansuibutchsansuibutch Posts: 141
    "After firing it up, It sounded quite good, except for a rather hot top end. The 10 crossover was designed for drivers with higher output, and a much larger enclosure. I decided there were two ways to balance the Tweeter and Woofer output. I could change the value of the .5 ohm resistor I installed in place of the Polyswitch. By raising the value, I could reduce the output of the hi-pass without adversely affecting the voicing of the tweeter. The other option is to install a much lower resistance Inductor, to increase the output of the two woofers. I found a 4ohm, 25 watt L-Pad, and temporarily installed it in place of the .5 ohm resistor. I used the common and 4 ohm leg, and preset it to .5 ohms. I fired up the speaker, and slowly increased the resistance until my ears told me it was in balance with the Woofers. The value turned out to be approximately 7.5 ohms. I wanted to test my other theory, and found a 15 gauge, 3.3 MH P-Core Inductor in my parts bin. I re-installed the .5 ohm resistor. I unwound the Inductor, until I reached the correct 3.1 mh rating on my LCR Meter. I disconnected the other inductor, and installed the P-Core. Woofer output increased, and to my ears, everything was balanced. I don't like P-Core Inductors, since they saturate easily, and have other distortion components. I decided to order a new Erse Hi-Q, Laminated Steel Inductor, which I've used in the past with great results. I also ordered a 17 uf Cap from Sonic to complete the permanent modifications to the crossover."

    Here you said you reinstalled the .5ohm resistor and used the erse hi-q laminated steel inductor unwound to 3.1mh and it was well balanced. I took your advice. Same .5ohm resistor and same erse hi-q laminated steel inductor unwound to 3.1mh. 😁
  • westmassguywestmassguy Posts: 6,625
    You have to tune it by ear really. That resistor is going to get really warm underneath, and wrapped in heat shrink tubing.
    Home Theater/2 Channel:
    Front: SDA-2ATL forum.polkaudio.com/discussion/143984/my-2as-finally-finished-almost/p1
    Center: Custom Built forum.polkaudio.com/discussion/150760/my-center-channel-project/p1
    Surrounds & Rears: Custom Built forum.polkaudio.com/discussion/151647/my-surround-project/p1
    Sonicaps, Mills, RDO-194s-198s, Dynamat, Hurricane Nuts, Blackhole5
    Pioneer Elite VSX-72TXV, Carver PM-600, SVS PB2-Plus Subwoofer
    Cables: Speaker: Furez 10/2 with GLS Locking Banana Plugs
    Interconnect: Furez 10/2 with SpeakONs
    ICs: Custom Furez by Douglas Connections
    Den:
    Bose 901 Series II Continentals Restored, Re-Built Equalizer with Elna Silmic IIs, Sonicaps, and Silver Mica Caps
    Carver CT-3 Pre, Carver C-500

    dhsspeakerservice.com/
    Exclusive Distributor of Gimpod's Custom SDA Circuit Boards

    "And keep her under 70, would you, huh? Betty likes a slow ride"
  • sansuibutchsansuibutch Posts: 141
    You have to tune it by ear really. That resistor is going to get really warm underneath, and wrapped in heat shrink tubing.

    I dont know how i missed that. I will trim the heat shrink off the resitor, il leave it on the leads. Thank you for pointing that out 👍

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