SP1200, 1700, or 2500 Crossover Diagrams

Discussion in 'Exclusively Sansui' started by Culpeper, May 17, 2017.

  1. Culpeper

    Culpeper Active Member

    Messages:
    188
    Attached are a schematic and an image of back and front of the circuit board. Interesting how the woofer is not filtered but runs from the "W +" to one end of Caps 1 and 3. The opposite end of these two caps are negative. The particular board is from an SP1700 but the 1200 and 2500 are the same circuit board with the same 700/6500 cutoffs. The only difference is Cap 3. The 1700 uses 3.3uF and the 2500 uses 4.7uF, etc.

    I also can't figure out how the switches work. L2 and L3 appear to be resistors? C N S stands for Clear, Natural, and Soft switch settings

    This thing is telling me the sluggish old OEM woofer can be changed and won't effect the crossover frequency range.
     

    Attached Files:

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  2. moefuzz

    moefuzz Active Member

    Messages:
    406
    Location:
    Peeyong Bangyou
    L1 L2 etc = are iron or ferrite core inductors -tap-able transformers.
    The taps allow you to select different crossover slopes and points depending on the tap and additional circuit/capacitance etc in that line..
    As opposed to Iron core, Ferrite core inductors are more expensive to manufacture and seem to work better in the circuit at higher frequencies where as iron core is less efficient at inducing higher frequencies.


    : an RLC circuit.
    R= Resistor,
    L= Inductor
    C= Capacitor

    An RLC circuit would be necessary when you need to control both the high and low cutoff frequencies (and their slopes) on things like a midrange in a three way system.

    An RLC can be tuned to both inhibit/roll off the mid highs (so as to not muddy the highs/tweeter) while also rolling off the mid lows (so as to not muddy the woofer).
    For the midrange, the correct circuit is a bandpass filter as it passes a frequency "range" while rolling off both the high and the low frequencies as per it's design.

    The idea is to allow each speaker/driver to reproduce their own frequencies in their own frequencies range. -Allowing the tweeter to also produce some/limited mid tones could cause undesirable coloration/harmonics. It's best to allow each driver to reproduce a certain range and inhibit adjacent drivers from 'attempting' to reproduce similiar frequencies in order to keep unwanted harmonics and coloration at bay.


    In a three way crossover, the woofer and tweeter would get sloping filters while the midrange would get a bandpass.
    All drivers would then be preforming in their own specific freq range with less chance of any 2 drivers broadcasting the same frequency thru a differently designed/sized cone or diaphragm.


    The addition of taps on the inductors allows you to somewhat tailor the bandpass, lowpass and highpass filters (using the rotary dials) to your individual tastes all while still keeping all three drivers limited into their own frequency/spectrum.

    Have a look here for more info...


    https://en.wikipedia.org/wiki/RLC_circuit


    .
     
    Last edited: May 18, 2017
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  3. Culpeper

    Culpeper Active Member

    Messages:
    188
    Thanks for the link. I attached another image as a result. In the center are a couple of tapped inductors.
     

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  4. Culpeper

    Culpeper Active Member

    Messages:
    188
    Those switches have me baffled. I can see where two of the connections = 16 ohms with a DMM, which corresponds with the white resister but I can't figure out what the switch is doing to change the tweeters or squawkers to clear, natural, or soft. Is Clear turning the volume up 3db and the Soft turning it down 3db? I don't think they are changing the crossover frequency. I can't find anything on these types of switches. They appear to be exclusively Sansui, no pun intended.
     
  5. Culpeper

    Culpeper Active Member

    Messages:
    188
    I've measured the inductor and two transformers

    351 = .348mH

    202T1 = Clear 1.99mH, Natural 1.053mH, and Soft .342mH

    301T1 = Clear .298mH, Natural .132mH, and Soft .039mH
     
  6. Culpeper

    Culpeper Active Member

    Messages:
    188
    Original factory setup. No filter on the woofer. Basically, a 2nd order bandpass (700/6500) on the midrange and a high pass (6500) on the tweeters. The original woofer acts as its own inductor and has a low frequency range. Thus, the muddy bass and superb highs on some of these vintage loudspeakers. Some of these crossovers come with 3.3 or 4.7uF caps. The difference is minimal. This is the typical Sansui ferrite core crossovers they bragged about back in the day.


    "Transformer Type 12 dB Crossover Network

    Here's the Sansui's exclusive knowhow of the transformer. The transformer type network is designed to let each of woofer, midranges and tweeters function in its most suitable frequency range, assuring clear sound even at the crossover points." [only there is nothing on the woofers]

    "Specially Designed Level Control

    The Sansui's exclusive transformer-type crossover network changed the level control from the conventional volume-type attenuator to the latest tap-type control whose operation does not influence the damping characteristics at all. This level control has three positions to adjust clear, natural and soft. The "natural" position is for the average rooms; "clear" for the rooms where the highs are swallowed up and the lows are exaggerated and "soft" for rooms where the lows are swallowed up and the highs are exaggerated." [explains nothing. Natural is the advertised 700/6500 crossover for the bandpass and 6500 for the high pass. Clear lowers the respective crossover points and Soft raises them. Soft has the most noticeable effect. The 16 ohm resistor only works on Clear.]
     

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    Last edited: Jun 11, 2017

     

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  7. Culpeper

    Culpeper Active Member

    Messages:
    188
    Replaced original sticky woofers with same weight 8ohm woofers (Pioneer A30IR50-51F) and added a filter. Original crossover is the same. Basically just added a 1st order 2mH inductor on the woofer. Port boxes are tuned at about 60Hz. Before the end of Hotel California's steady bass riff sounded like one continuous note. Now, it sounds proper and can make out the bass as meant to. Bass is no longer not vibrating the room but is still very much there.
     

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    Last edited: Jun 16, 2017
  8. Culpeper

    Culpeper Active Member

    Messages:
    188
    FR graph. Original system (green) and the new woofer (black).
     

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  9. Culpeper

    Culpeper Active Member

    Messages:
    188
    Woofer with and without RC circuit.
     

    Attached Files:

  10. VanArn

    VanArn Member

    Messages:
    67
    Location:
    Melbourne,Australia.
    The original Sansui woofer may have used a 4 layer voice coil and possibly a heavy cone assembly to provide a natural HF roll-off. All I can see is cost cutting measures in place. The tapped inductors simply allow for the levels to be changed and I would think the 16 ohm resistors are fitted , partially to flatten the impedance and to prevent a brief open cct. event from happening when a switch is operated. Obviously this is not a speaker that was intended to be used with high powered amplifiers or made to suit serious listeners. Those Japanese fretwork speakers of the 60,s and 70,s were made for people who went for looks and features at an attractive price . Unfortunately it gave them a poor reputation that took many years to overcome.
     
  11. Culpeper

    Culpeper Active Member

    Messages:
    188
    Agreed, but the cabs are solid, the crossover is printed, original damping material is no joke, and the caps were replaced. You should see the Sansui ones where the crossover is wired up on a plank of compressed cardboard. I have them on a 80W HK amp. The highs are outstanding and back in the day they would demo these by letting the upper range blow out a candle. That info I got from Atkinson at Stereophile who is older than dirt, lol. Nevertheless, there is enough potential with these that some simple replacement decent caps and a modern simple filtered woofer replacement can't resolve to reverse the manufacturer cost saving bug-a-boo. And I'm not sure at that time what was used had any measurable difference based on the playback media at that time. Including amplifiers that complemented them. Klipsch is still toting their classics, people are cloning their design, and these particular Sansui boxes can easily and cheaply brought to that level without spending a couple thousand dollars. All I have in these is the cost of good caps, bargain woofers with a bobbin inductor that cost a few dollars. The RC circuit I'm going to put on the woofers is where I am probably getting too extravagant. But, what the heck. Attached is a typical Klipsch crossover on a wood plank which people clone and/or sell for a couple of hundred dollars.
     

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    Last edited: Jun 27, 2017
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  12. Culpeper

    Culpeper Active Member

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    188
    Also, looks like my woofer is rolling off at about 650Hz based on that 2mH inductor. It crosses over the midrange at about 1000Hz.
     
  13. sragan

    sragan New Member

    Messages:
    44
    I've lurked for a long time, and found this thread. Great reading for me, as I'm considering rebuilding on of my 3 pairs of 2500s. Very interested in what you're doing with the crossover, good info. I've been thinking of completely rebuilding the factory crossover and getting rid of the switches and possibly going with Lpads for the mid/high behind the crossover, just to make it easy on me.. I used the Dayton DATS to measure the T/S of the woofer (info at end of post) and tried to measure the inductors, but DATS had a hard time below .5mh. Thanks for posting up your findings. WiniSD, if I'm using it right, puts an ideal box at 11cft! Bad as I hate to do it, I'm thinking of putting the Dayton DC300-8 12" Classic woofer in as a replacement, and your woofer bypass looks ideal with it. I still may rebuild the cabinets and retain the lattice grills.

    Would definitely like to see pics of how your new crossover is laid out. I recapped one of the crossovers already just using Mundorf E-caps and will be using just the mid/high combo for my center channel in HT combined with Klipsch KG4s and HSU dual 10" sub.

    My audio listening is in a separate room using an HK 3475 and I'm using an 8" bucket sub as a midbass (70-200) and a TC Sounds 12" for lows. I've upgraded the wiring inside the cabinets as well as polyfill and weatherstripping on the back panels. Love my 2500s.

    T/S as measured by DATS:

    * This data was exported from the Dayton Audio Test System: DATS
    *
    * Piston Diameter = 241.3 mm
    * f(s)= 85.46 Hz
    * R(e)= 5.167 Ohms
    * Z(max)= 30.14 Ohms
    * Q(ms)= 4.842
    * Q(es)= 1.002
    * Q(ts)= 0.83
    * V(as)= 29.35 liters (1.036 cubic feet)
    * L(e)= 1.768 mH
    * n(0)= 1.744 %
    * SPL= 94.52 1W/1m
    * M(ms)= 34.71 grams
    * C(ms)= 0.1 mm/N
    * BL= 9.805
    * K(r)= 0.3454
    * X(r)= 0.3894
    * K(i)= 0.1606
    * X(i)= 0.4374
     
  14. Culpeper

    Culpeper Active Member

    Messages:
    188
    Great job. That is good useful information. I'm just using the stock recapped crossovers. I ended up with the 1st order inductor and zobel network between the crossover and the woofer since the crossover just bypasses the woofer anyway.
     
  15. sragan

    sragan New Member

    Messages:
    44
    I just got a couple of 1.5mh coils in this week to try them out on the factory woofers. Hopefully I'll get them installed this week.
     
  16. Kenny*G

    Kenny*G AK Subscriber Subscriber

    Messages:
    44
    Location:
    Dickinson, Texas
    Culpeper, any chance you build these cross overs & sell them ? I have a pair of SP-1700 I was thinking about replacing the caps in, then I saw this thread and I'm really interested in your woofer upgrade and doing the cross overs. Did a search for the woofers you used and of course they are discontinued, any other good options you know of ?

    Thanks in Advance

     

     

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  17. Culpeper

    Culpeper Active Member

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    188
    KennyG, recap your existing SP1700 crossovers. Put a first order 1.5mH inductor for the the Sansui W-110 woofer between the speaker and the SP1700 crossover. The output signal from the amp is fed directly to the woofer. Adding the inductor will create a simple 850 Hz 1st order crossover for the woofer. If you want to replace the woofer that is fine because the originals are rated at 8 ohms so replacement is a matter of the same size. You can use the same size inductor as explained above.
     
  18. Kenny*G

    Kenny*G AK Subscriber Subscriber

    Messages:
    44
    Location:
    Dickinson, Texas
    Any chance you have a list of what I would need to recap mine and do the mod you did on the woofer, capacitor quantity & values need ? I would like to be able to order everything and then break the speakers down for the refresh.
    If I decided to go the B&K Cross over route, is the (Type AA) the one you have posted the correct one to use for this app ?
     
  19. Culpeper

    Culpeper Active Member

    Messages:
    188
    For each speaker cabinet 1 each...

    https://www.parts-express.com/erse-15mh-18-awg-i-core-inductor-crossover-coil--266-552

    https://www.parts-express.com/jantzen-audio-22uf-400v-z-standard-capacitor--027-266

    https://www.parts-express.com/jantzen-audio-33uf-400v-z-standard-capacitor--027-270

    https://www.parts-express.com/jantzen-audio-10uf-400v-z-standard-capacitor--027-282

    Here is an example on replacing them. I actually seal the new caps on top of the old ones with silicone adhesive you can get at the hardware or auto parts store.

    https://retrovoltage.com/2011/04/05/refurbishing-vintage-sansui-sp2500-speakers/

    The inductor is placed in the cabinet between the crossover and the woofer on the positive side. You may need additional speaker connectors and wire. I glued a piece of 1x2 cheap pine lumber inside the cabinet wall to mount the inductor.

    See the diagram below for the inductor on the "low pass" woofer....

    http://www.erseaudio.com/CrossoverCalculators/First-Order-2-Way
     
    Last edited: Dec 18, 2017
  20. Culpeper

    Culpeper Active Member

    Messages:
    188
    You are not going to hear an advantage using a Klipsch cloned crossover. I was just using them as example to compare and contrast with the stock Sansui "SP" crossovers. The Kipsch crossovers are for specific Kipsch speaker systems.

    Also, you should test each speaker in your cabinets and make sure they are all good before upgrading the crossovers. You never know, you might have a broken tweeter or midrange that will need replacing.
     
    Last edited: Dec 18, 2017

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