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Small variations in Mini III crossover assemblies are evident from the more detailed audio forum posts. They typically appear to have identical potentiometers in Mid and Tweeter circuits, with either 5 Watt or 10 Watt midrange 4Ω series resistor and approximately 1.8µF to 2.2µF tweeter series...

Toasty! It is indeed a 16Ω resistor. Some are labeled "K 16 Ω," which is a bit different than above. "K" is presumably for 10% tolerance rating. Both tweeter and squawker circuit resistors are always identical. Those displaying the Matsushita symbol are marked "6P." The other style is...

Woofer and tweeter are both made in 1971 by Becker. Input terminals look fairly stout. If they sound good I don't see anything not to like.

That's a good point and, as shown above, clockwise rotation would indeed attenuate rather than increase lower tweeter frequency output. So if keeping with convention is preferred, just use the opposite terminal to connect between R1 and R2.

With the 25Ω potentiometer, just connect the center terminal to the 3Ω resistor (R4), and either of the other terminals connects between R1 and R2. A 10Ω resistor can be substituted between the same two connection points.

That's actually a New Advent Loudspeaker (aka NLA). It's tweeter uses ferrofluid -- an important distinction from earlier versions. Advent tweeters were readily found on auctions sites not so long ago. Which may have been partly influenced by a peak in econowave mod activity. They can still be...

It's beautiful! You've done a really impressive job managing the physical restoration and technical challenges of this project. It's been so much fun to vicariously follow along! :thumbsup:

Had a close look at the Dayton Audio XO2W-2K crossover assembly so I'll post some details to more fully document this thing. It provides 2nd order filters for both woofer and tweeter with a target frequency of 2kHz. The tweeter filter is fixed for an 8Ω load using a 5.1µF series cap and 1.4mH...

Those sneaky bastids! :thumbsup:

Enjoying following your progress in this thread. Especially finding the grille cleaning tips useful. :thumbsup: It's perplexing that no capacitors are found in the crossover. Inconceivable (to me) that the tweeter could survive without a high pass filter. Might there be a series capacitor...

Here's what appears to be the basic crossover configuration: The woofer filter inductor has an unused tap suggesting flexibility to accommodate different woofer impedance loads -- reminiscent of some classic Bozak crossovers. It's depicted above with woofer connected to full inductance, though...

OUCH!

Hi-Vi L5-8R is said to be a drop-in replacement for the Minimus-77 1291 woofer. Popular replacement for LX-5 family of Linæum tweeter topped speakers. Though it specs quite well in a sealed enclosure. A possible dimensional issue is its mounting depth of 77.5mm, which is frightfully close to...

There should be three versions of US built Formula 1 sold in North America. Yours appears to be early, with its product label spelling out "BRITISH INDUSTRIES CO." below the "Brightness" knob. Later version label changes that to "B·I·C VENTURI" under knob now called "Balance Control" The...

Apparently made in both 16Ω and 8Ω versions.

That schematic just shows how a 24dB/octave (steep cutoff) high-pass filter could be inserted into a generic woofer circuit. The component values would be chosen to block only very low frequencies to spare the woofer from excessive excursion. The XO2W-2K crossover has a 2nd order (12dB/octave)...

These are perfect! I didn't realize R43 through 46 have printed values rather than colour bands. This couldn't be more clear. And red band confirms 1.5kΩ for R41/42. Now I can finalize and post this with confidence. Many thanks! :thumbsup:

That low pass filter is intended for a subwoofer and not what you want. Low pass at 80Hz means only frequencies from 80Hz and below will pass through. Frequencies higher than 80Hz will be filtered out. That will create a large gap in sound before the tweeter comes in at around 1,500Hz. I read...

My Optimus-21 aren't convenient to access just now, though reverse calculating from published "46 square inches" of cone radiating area gives the effective diameter of 7.65 inches. Tandy may have used cone diameter inside the surround for this calculation. :dunno: Marketing does play fast and...

According to Pete's Advent website, yours appear to be closest to revision 1.

Optimus-21 ran for two years only. It was introduced in the 1978 catalogue as having an 8" woofer with 25 square inch cone radiating area. The 1979 catalogue changed that to a 10" woofer with 46 square inch cone area. All else (cabinet dimensions, frequency response etc.) is identical. Have...

The three resistors provide various series attenuation levels to both mid/tweeters according to position of the HF Compensation switch. The 2Ω resistor is always in circuit and works alone in "High" setting. "Normal" adds the 4Ω resistor and "Low" adds the 6Ω resistor as well . The first...

A few years back member @richartistic reported figuring out how to open the meters, but didn't describe the method. This at least suggests it's doable. While you have the unit open, would it be inconvenient to verify value of a couple of resistors? The seemingly only existing schematic (posted...

I grabbed frequency response files (.frd) and impedance files (.zma) from Dayton's website for the drivers you're using. These can be used to run crossover circuit simulations in XSim to get an idea of what to expect with various crossover configurations. Published frequency response graph for...

Didn't realize your turntable uses a ceramic cartridge when I suggested a phono preamp. If there was more room in the console compartment, SA-155 could be used as the preamp. There is a switch on back near the phono input jacks labeled "CER" and "MAG" for selecting input of either ceramic or...