The iixo is a subtractive cross over suitable for horn systems I came up with a while back and have used for several years. I have made a few for other people and others have made their own with good results. While it has all the limitations of a 1st order xo in terms of excursion, (see threads here on diyAudio), with a suitably robust driver and horns and low power requirement it integrates a bass horn with a mid-upper horn very well, and provides the attenuation for the upper driver.
The iixo is nothing more than a low pass inductor in series with the bass driver, with a secondary winding to feed the upper driver. It is a transformer and the turns ratio sets the attenuation. The inverse of the signal across the bass driver appears across the inductor, since the output of the amplifier is flat.
The iixo requires there be a minimum step down ratio, of at least -6 to -9dB. More on this later, but you cannot get a 1:1 output. Attenuation is usually required for the upper horn and you can include a number of taps on the secondary to adjust this.
The iixo models and measures as expected with resistive loads but things change once you include the voice coil reactance. The bass driver requires a Zobel, which is no surprise. Another issue is that inductor coils with iron cores do not have constant inductance with frequency. A cheap LCR meter reading at 1kHz may not be the same reading given by a meter that can be set to 100Hz. But there are ways to wind a coil and choose a core that is much more constant.
The signal across the inductor can be taken to a second amp, and then you can have a 2nd order or greater slope. I got the idea for the iixo from jc morrison’s subtractive xo where he takes the signal across a high pass cap to a second amp. The iixo has the advantage of no cap and single amp.
I encourage anyone to try this simple idea, just wind a secondary on top of a LP inductor. I do some interleaving but it is not critical. If you don’t know the turns you can use the ratio of inductance which is the square of the turns ratio. I would welcome any comments. Also any history, as hard to believe I am the first. I nearly fell off the Listening Chair when I thought of it! But nobody has yet told me of any and I sent it to jc and others notorious. I have put it up on my website here:
https://www.azurahorn.com/azurahorn_system.html
The iixo is nothing more than a low pass inductor in series with the bass driver, with a secondary winding to feed the upper driver. It is a transformer and the turns ratio sets the attenuation. The inverse of the signal across the bass driver appears across the inductor, since the output of the amplifier is flat.
The iixo requires there be a minimum step down ratio, of at least -6 to -9dB. More on this later, but you cannot get a 1:1 output. Attenuation is usually required for the upper horn and you can include a number of taps on the secondary to adjust this.
The iixo models and measures as expected with resistive loads but things change once you include the voice coil reactance. The bass driver requires a Zobel, which is no surprise. Another issue is that inductor coils with iron cores do not have constant inductance with frequency. A cheap LCR meter reading at 1kHz may not be the same reading given by a meter that can be set to 100Hz. But there are ways to wind a coil and choose a core that is much more constant.
The signal across the inductor can be taken to a second amp, and then you can have a 2nd order or greater slope. I got the idea for the iixo from jc morrison’s subtractive xo where he takes the signal across a high pass cap to a second amp. The iixo has the advantage of no cap and single amp.
I encourage anyone to try this simple idea, just wind a secondary on top of a LP inductor. I do some interleaving but it is not critical. If you don’t know the turns you can use the ratio of inductance which is the square of the turns ratio. I would welcome any comments. Also any history, as hard to believe I am the first. I nearly fell off the Listening Chair when I thought of it! But nobody has yet told me of any and I sent it to jc and others notorious. I have put it up on my website here:
https://www.azurahorn.com/azurahorn_system.html
