[scottw]

Seems to me it would be cost effective to have a multi-tap iron core choke for fiddling around with xover points of the 'augmenting' woofers on our OB's. Something like 5 to 15 mH. Anybody make these?

Scott

[Graham Maynard]

Hi Scott,

2x 5mH chokes in series and at right angles = 10mH
2x 5mH chokes in series, from 90 to zero degrees with adjustable gap end to end -
gives approx 1 to 10mH with winding sense in opposition,
or 10 to 19mH when the widings are in the same sense.

Hence 2x 5mH chokes are all you need for 1 to 19mH; simply adjust the gap and rotational angle between them to acheive the desired reproduction.

Cheers ...... Graham.

[scottw]

Thanks Graham,

That's brilliant. Glad I asked.

Should you stick with an "I" type core with this method or would it work with an "H" core like the Erse super q's?

Scott

[guest4954]

Thanks Graham,

Sounds very smart and simple.

Can you carify with a little drawing or photo so I can see wether I understand correctly

Regards,

Michiel

[Graham Maynard]

I change impedance at LF using simple 'I' cores.  I do it with lower value 'I' cores for midrange too.

As you move two cores in line and closer together you can either degrease or increase their mutual coupling with opposing or same winding senses respectively.

It is very useful having this variable choice, especially with white noise (FM hiss), because this makes peak and dip control far easier than when trying to discern which aspect is affecting audio reproduction.

Cheers ........ Graham.

[JoshK]

Hi Scott,

2x 5mH chokes in series and at right angles = 10mH
2x 5mH chokes in series, from 90 to zero degrees with adjustable gap end to end -
gives approx 1 to 10mH with winding sense in opposition,
or 10 to 19mH when the widings are in the same sense.

Hence 2x 5mH chokes are all you need for 1 to 19mH; simply adjust the gap and rotational angle between them to acheive the desired reproduction.

Cheers ...... Graham.

Huh, didn't know that.  Learn something new each day.  I knew that angle affected the coupling of the magnetic fields but I didn't know it changed the inductance. 

Does it affect to capacitive reactance too?  Would it be easy to cause it to resonate if not careful?