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  1. Retrovert

    Polarized capacitors in crossovers

    I suspect you are thinking that the current seen by the speaker is moving from positive to negative and then negative to positive as with the mains. That is not happening because the current source in an amplifier typically is a mono-polar rail. Think instead about the direction of the...
  2. Retrovert

    Polarized capacitors in crossovers

    I, alas, lack the time to respond in detail or with a custom response, but here's a brief explanation culled from other writings of mine. I refer you to my earlier explanation about the output stages and capacitors, some of which I have linked. I think this is going circular, as the questions...
  3. Retrovert

    Southwest Technical Products Corp. (SWTPC) Headphone Amp 202-C

    I would like to have the entire manual and schematic. Is the circuit identical to a Plastic Tiger with biasing modified for Class A instead of Class AB? BTW, I tried to send you a PM, but your account is not configured for PMs from members.
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    Bozak Mystery

    Scrim: https://www.google.com/search?q=scrim Buckram: https://www.google.com/search?q=buckram
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    Bozak Mystery

    Here is what I elsewhere wrote (slightly edited to remove extraneous material and for clarity) two years ago on the subject of Tufflex. That yellow material is Tufflex, a reprocessed cellulose (industry names viscose or rayon), praised be its name. Bozak originally used Tufflex for the lining...
  6. Retrovert

    cerwin vega hed u-15

    A crossover is an electrical filter designed for specific frequencies, and a mass-market crossover may not have the appropriate frequencies or may have filters which are unsuitable because of steepness of slope which controls how effectively the filter removes out-of-band signal. The formulas...
  7. Retrovert

    Newer bozak speakers?

    Shrug. The B-209 is a vastly superior, and far more costly, midrange. Someone ought to explain why the smaller B-450 is superior to its larger sibling.
  8. Retrovert

    Newer bozak speakers?

    The B-450 is inferior to the B-209 used in the non-budget Bozak line. The B-450 was created as a cost-savings measure circa the mid-1970s.
  9. Retrovert

    Karlson K-15, how do I replace the grille cloth?

    A simple option might exist for you. When I was in high school, and not knowing much about wood finishes beyond what I read in my dad's books, I used a colored polyurethane varnish on my flat-pack Karlsons which were raw plywood. Red Mahogany which did not look like mahogany, although it was...
  10. Retrovert

    Newer bozak speakers?

    The dimensions of a B-302, Rhapsody, or even the B-313 are quite manageable. Not every Bozak is a refrigerator-sized Concert Grand or Symphony. My point remains valid: a ported Bozak with inferior components delivers a different sound than the original infinite-baffle Bozak with a quality...
  11. Retrovert

    Newer bozak speakers?

    The DMS line was designed to be able to compete with smaller, less-expensive, ported speakers, and consequently incorporates an inferior midrange and uses a ported cabinet with is totally different than the infinite-baffle cabinet for which the original Bozak drivers were designed. I suggest...
  12. Retrovert

    Newer bozak speakers?

    The DMS 3500 is a ported cabinet with a three-way consisting of a B-800 as the woofer, B-450 midrange, and a dome tweeter of some sort. It was introduced sometime in the mid-1980s after the dismemberment of Bozak. A ported cabinet design is NOT the traditional infinite baffle used by Bozak...
  13. Retrovert

    Bozak DMS 2500; Specs? Opinions?

    Sigh. Four years ago the problem was resolved! Please read the thread. The OP did not like the boomy nature of the DMS 2500 and found the sound much improved by plugging the port. Again, see the thread. I pointed out that the problem had been resolved, that the ported Bozaks have a...
  14. Retrovert

    Bozak DMS 2500; Specs? Opinions?

    The OP inquired FOUR YEARS AGO, and the OP's problem was fully solved, as he posted, by plugging the port AND adding a functioning tweeter. Well, that's an absurd claim! The circumstances and location of your birth have nothing to do with whether or not a ported speaker, using drivers...
  15. Retrovert

    Bozak DMS 2500; Specs? Opinions?

    Thread necromancy — nearly four years! — never decently ends. Sigh. The DMS 2500 is a budget two-way constructed from a B-800 and a tweeter, in a tiny, ported cabinet notably lacking the famed Bozak curtain. The too-small, ported cabinet is stuffed with a pile of chopped up solid-latex foam...
  16. Retrovert

    Bozak speakers with Marantz?

    Thread necromancy. You do realize you are following up to a thread about speakers available for sale five years ago, correct?
  17. Retrovert

    Reaching out for the community wisdom

    Looks like an Audiom 70, likely from the late 1950s. Now all you need is a ported cabinet with a Acoustic Resistance Unit, an aperiodic port which may be approximated using filter scrim in a frame. Here is a few paragraphs I previously wrote about Goodmans drivers of this vintage. The...
  18. Retrovert

    Sorta Bozak Urbans

    Crossovers do not require a break-in period. That is audiophoolery unsupported by physics and electrical engineering, let alone double-blind testing. If capacitors required break-in, then military equipment, hospital equipment, and mission-critical equipment would require it. The brain...
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    Sorta Bozak Urbans

    Soldering I don't mean this in any mean or snarky way, but your soldering technique is misguided and the entirety of those connections should be repaired prior to further use. The key to soldering is a solid mechanical connection with the wires or leads physically wrapped around each other...
  20. Retrovert

    Sorta Bozak Urbans

    When the ferrite magnets were designed as replacement for the alnico the magnet strength should have been matched to maintain the same characteristics. I doubt you could hear any difference. Much of the desire for alnico is audio fetishism. One caution. Do not make the speakers completely...
  21. Retrovert

    Sorta Bozak Urbans

    Two issues: (1) Many times boosting the higher frequencies can overcome age-related hearing loss. The Morel super-tweeters I suggested for Bozaks are very efficient so it should be possible to boost without an equalizer. The L-pad would normally be used to attenuate, so it can be reduced to...
  22. Retrovert

    Sorta Bozak Urbans

    Which is why the four-way modification, adding a super-tweeter at 8,000 Hz and removing the distortion of the B-200Y which increases with frequency, is the next obvious improvement.
  23. Retrovert

    Sorta Bozak Urbans

    Very likely not your ears. Bozak was trying to compete with other awful speakers and made its own awful speaker. Nobody wins that speaker comparison battle, particularly the consumer. I don't own a Rhapsody, and the crossover schematics are often inaccurate or different, but here's what I...
  24. Retrovert

    Sorta Bozak Urbans

    The B-207 is a B-199 woofer combined with a tweeter bracket. Each B-200Y tweeter is 16 Ω, with the pair parallel wired to yield 8 Ω. I suggest exercising a bit of caution when handling or attaching the midrange domes, as the plastic is brittle and may easily be cracked. I have seen a number...
  25. Retrovert

    Sorta Bozak Urbans

    Based upon your description of the raw material and your skillset this sounds like very bad project for you. A great deal of expense and effort will be required to line the cabinet and properly construct the curtain. Both may not succeed if you do not have the requisite expertise. The...
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