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

Revised Crossover for the BR-1 Kit

Parts Express currently has their popular BR-1 Kit on sale for $125 a pair, which includes decent cabinets. 

This is a deal.  The sound of the stock crossover is about a B+/B.  Better than any commercial budget speaker you'll find at Circuit City, but it does lack presence in the lower treble due to interference effects between the tweeter and a woofer peak in that range.  Understandably, the designer did not want to throw a lot of parts at smoothing out the woofer roll-off given the severe budget constraint he faced.  I have reworked the crossover topology to eliminate the interference problem, and I think the sound is much improved.  That's the good news.  The bad news is that I could only salvage 3 components from the stock board--the resistor (8 ohms) and capacitor (47 uF) that form the impedance compensation network, and the .4 mH inductor in the tweeter circuit.  If you have the ability to measure an inductor, you could also unwind the stock 1.5 mH inductor until you reach 1.0 mH.  That would save you about $15.  As it stands, the replacement parts will cost you about $50 with shipping from PE.

Here is the response of the stock unshielded BR-1 as simulated by lspCAD:

Here is the response with the revised crossover:

Here is the schematic for the unshielded woofer crossover circuit:

And here is the unshielded tweeter schematic:

Please note that any resistor shown in line with an inductor doesn't really exist if it's value is below 1.0 ohms.  That's just lspCAD's confusing way of telling you the approximate dcr of the inductor itself.  But any resistor above 1.0 ohms is very real--and very important.

Finally, here is a parts list, with links to the correct components from Parts Express.  You'll need 2 of each.

Parts List




Here are the schematics for the revised shielded BR-1.  In Net 2, the .5 ohm resistor in line with the .33 mH shunt inductor is real.  It does not just represent the dcr of the inductor.  But the .4 ohm resistor in line with the main woofer series inductor does not really exist--that's just the approximate dcr of the 1.2 mH inductor.