Upgrading OLD Speakers

Discussion in 'Home Theater Projects' started by Ryan_N, Feb 11, 2004.

  1. Ryan_N

    Ryan_N Auditioning

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    I have a pair of OLD Bozak Speakers (I think they are from between 60's to late 70's). I want to upgrade them. They have 12" woofers, 4" midranges, and 1" dome tweeters. I'm very new to DIY and home theater in general. What can I do do improve upgrade these speakers?

    -Ryan
     
  2. Bob K

    Bob K Stunt Coordinator

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    Ryan,

    I certainly know the Bozak name -- very famous -- but don't know much about his designs.

    Do the speakers work at all? Are the drivers completely shot? Are the crossovers still intact?

    Depending on the answers, there are several ways to go. First, if the drivers still function, you could just make new crossovers, using better, more modern parts, rewire and restuff.

    If the drivers are shot, it's unlikely you are going to find identical drivers, or even identical-size drivers. In that case, I would try to estimate the inner volume of each speaker and then look around the web and forums such as http://www.madisound.com for a diy design or kit designed to fill that volume. With this approach you are basically just using the box. You would remove the old drivers, crossovers, stuffing etc. You would also have to create new front baffles to accept the new drivers.

    One of my first speaker projects involved doing just this with a pair of old Ohm C2 speakers a friend was throwing out. It was very educational, and I now have a great pair of speakers.

    Tempest Construction Pix: http://www.audiocircle.com/circles/m...view_album.php
     
  3. Ryan_N

    Ryan_N Auditioning

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    Actually the speakers work very well. The drivers are in perfect condition. All I want to do is make them sound better. Like I said I'm new to this so I dont exactly know how to upgrade a crossover network. What kind of stuff should I search for? (I love search functions BTW-Crossover Networks? What else. Anywhere you can point me would be great. And what kind of rear surrounds and center channel could I match to something like this? Thanks for all of the help.

    -Ryan
     
  4. Bob K

    Bob K Stunt Coordinator

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    Ryan,

    First, if the speakers sound just fine, you can just do nothing!

    Assuming you want to try anyway, you can probably access the crossovers by taking out the drivers. (In the alternative, if the speakers have cups or panels on the back, the crossovers may be accessible by taking out the cups.) Assuming you can access them, you will see that they are (probably) boards to which are soldered wires and two, or possibly three, types of components: inductors, capacitors and, possibly, resistors. If you don't know what these different components look like, take a look at some of the pictures in the Catalog section at http://www.madisound.com .

    Examine each component and see whether you can determine (a) what it is, and (b) what its relevant measurement is.

    For resistors, you are looking for resistance and wattage. The resistor might say "3R5 50W", which means 3.5 Ohms, rated up to 50 Watts. The resistor might use the Greek letter Omega instead of "R", so it might read "3.5 [Omega]. (It is conceivable that the resistors could be color coded. If so, let me know.)

    For capacitors, you are looking for micro Farads and voltage. The cap might say "2.0 uF [the "u" being the convention for the Greek letter Mu] 200V."

    For inductors, you are looking for milli Henries. The inductor might say "1 mH".

    After you identify the parts (or as many as you can), and if you want to keep going, post back here. We can then consider which parts to replace and where to source them.

    DO NOT UNSOLDER OR DISASSEMBLE ANYTHING WITHOUT TAKING A PICTURE OR MAKING A VERY CAREFUL DIAGRAM so you can put the crossover back together again properly.

    Unfortunately, I'm no help in matching a center and surrounds to your Bozaks since I don't know them. Hopefully, others can help.

    Let me know how it goes. Good luck.

    Tempest Construction Pix: http://www.audiocircle.com/circles/m...view_album.php
     
  5. Joseph Sabato

    Joseph Sabato Stunt Coordinator

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    The Bozaks were great speakers in their day. They used "infinite baffle" woofer designs (very small Vas) in their systems. The ones I remember hearing were the Concert Grands; (4) 12 woofers, several midranges and a line array of tweeters firing through a slot. Their main competition at the time was the Klipshorn and the big Altec Lansing Horn systems....they were considered expensive speakers at the time. Finding imprved replacement drivers thet would not require a full system re-design would be difficult. I think improving the crossovers would be the best track. Good Luck.
     
  6. Ryan_N

    Ryan_N Auditioning

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    Ok I opened them up today. Here is what I found:

    Woofer-
    -12" MDL# B199bc
    -Polypropelyne or treated paper
    -rubber suurounds

    Midrange-
    -4" MDL# B450c
    -aluminum cone
    -some kind of thin clothlike surround
    -PVC dome behind the driver

    Tweeter-
    -1 1/8" MDL# HD 12x9D 25hr
    -silk-dome

    Enclosure-
    -3/4" MDF No Internal Bracing

    Hookups-
    -Screw in wires
    -Variable Resistor (3 Settings)
    --Mellow
    --Normal
    --Bright

    Crossover
    -Has wire hookups and vaiable resistor on it
    -Parts
    --Caps
    ---100uF 50V
    ---4.7uF 50V
    ---15uF 50V
    --Resistor
    ---10ohm 10W (square)
    ---6ohm 10% (square)
    ---10ohm 10W (square)
    ---5.0ohm 10% 250V (long cylinder)
    ---15ohm 10%
    --Inductors
    ---no values listed but there are 3 sizes
    ----2.25"
    ----1.5"
    ----1"
    --Fuse
    ---unknown value-inline with tweeter

    So what can I do? I can try to get a schematic of it up tonight, and maybe a digicam pic.

    -Ryan
     
  7. Chuck Bogie

    Chuck Bogie Second Unit

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    About all I'd do would be to _maybe_ find some fresh components for the crossovers, and build some new ones with identical values - sometimes old stuff can deteriorate a bit.

    A while back my sister's husband was cleaning out the basement, and gave me a pair of "really old" speakers. They were kinda small, and I didn't want to reuse the boxes, but they appeared to be in decent enough shape, so they were given to a friend...

    Then they got hooked to a Marantz 4240, and I realized that I'd screwed up... They were some old EPIs, and I wish they were in MY bedroom instead of in her living room.

    Don't fix it if it ain't broke.
     
  8. Todd Shore

    Todd Shore Stunt Coordinator

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    What don't you like about the speakers? I'm asking since you say they sound fine but you are still looking for improvements. Are you comfortable listening to them for long sessions?
     
  9. Bob K

    Bob K Stunt Coordinator

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    Ryan,

    I'll start by repeating what others have said: If you like the sound of the speakers, you don't have to do anything!

    That said, if I were to replace anything I'd replace the capacitors, particularly if the 100 uF cap is an electrolytic. I took a look and Madisound has Solen caps in all three values you mention. For the smaller values (I don't think there's a lot of choice in non-electrolytics for the 100 uF value) there are some "designer" alternatives (e.g., Hovland and Auricap), but they get pricey.

    You would just do a part-for-part substitution of each cap. Remember to take a picture or make a careful diagram before you do anything!

    Good luck. Let us know how it goes.
     

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