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

Mod for Morel 403.5 3-Way

Here is a very simple crossover modification that will substantially improve the performance of the popular Morel 403.5 speaker.  The mod has been auditioned and approved by Morel, and implementing it will not void the factory warranty.  The Morel is available at

This model uses a dome midrange that has a huge 10 dB breakup mode between 6 kHz and 9 kHz.   It looks like this:

The factory crossover does not adjust for this, and the result is destructive interference between the midrange and tweeter in the mid treble, and ringing due to the midrange breakup.  Fortunately, the midrange peak can be suppressed by adding a simple trap filter composed of a 1 ohm resistor, an 8.2 uF capacitor, and a .06 mH inductor, all connected together in series and then wired between the terminals of the dome mid.  Just take the midrange out, remove a little bit of the insulation near the terminals, and twist the 3-component trap circuit to each section of bare wire.  It doesn't matter what order the components are in, or which end you connect to which midrange wire.  You should solder the new connection, but if that isn't possible, make sure the twisting is tight and cover with electrical tape.  This produces the following response curve:

I can send you the little .06 inductors -- they aren't commonly available.  The cost for a pair with shipping would be $5.  I can also send you the whole circuit ready to install.  That will cost you $20 per pair (my cost for the Mills resistors, poly caps, and inductors).  Just e-mail me.

The change in phase relationships between the mid and tweeter will require that the wiring be reversed on the tweeter.  So take the tweeter out and switch the connections on the back.  That's it.  The sound will now be much more focused and accurate.  If you have any questions or problems, just e-mail me.