Revised MBOW1 3-Way

Revised Crossover for the Best Buy Insignia

Revised Crossover for the BR-1 Kit

Mod for Morel 403.5 3-Way


Revised Crossover for the Norh 9.0 Marble

The New Vifa Tower

Fixing the Polk RTi28

The MB20

The MB27

The Plop-in-the-Box

The Usher Two-Way

Revised Crossover for the Radio Shack LX550

Alternative Crossover for the Dynaudio Gemini

Crossover for the Revelator-RT1 Mini Monitor

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The Acoustic Research AR4x

A Tale of Two Cabinets

Tweeter Comparison

The RadioShack Minimus 7

JMLab Mezzo Utopia,
Tannoy Westminster,

Measurements for the Radio Shack LX550

Proac Super Tablette

Acoustic Research AR3a

Sound Dynamics RTS-3

Stock vs Modified Gemini

NHT Super One

The RadioShack Minimus 7

The RadioShack Minimus 7, AKA Optimus 7, OptimusAV, and I'm not sure what else, is by a wide margin the largest selling speaker on the planet.  A diminutive 7" X 4.5" in a black or white metal case, it is a ubiquitous presence in dentists' offices, college dorms, and anywhere else cheap small decent-sounding speakers are required.  For decades, the regular price of $49.95 each was reduced in June to $29.95, and I suspect that's when most of the sales were made.

There have been a number of attempts by experimenters to improve them, but these efforts were thwarted by frequent changes in the parameters of the drivers (as RadioShack sourced out from a different Asian factory) or by the lack of interior room for extra crossover parts.  The stock crossover is just a coil and cap on the tweeter.  The little woofer runs free.  What you end up with is very smooth response up to about 1200Hz, followed by a woofer break up in the 2500 Hz-3500 Hz region, followed by destructive interference between the woofer and tweeter from 5k-8k, and then fairly strong output up to 15k.  It looks like a mess, but it sounds quite good at low volumes, particularly if they're sitting on a shelf near a wall boundary.  I have a pair attached to my clock radio by the bed, and they're fine for that.  Crank up the volume and they start sounding edgy real fast.