I am building a pair of Jeff Bagby's "Kairos Woofer Modules" for use with my Jeff Bagby "Aurcicle", RAAL/SB Acoustics standmount speakers.
These woofer modules are not subwoofers, but designed to create a 3 ways system when used with a standmount/monitor speaker.
The design, for the low pass portion of the crossover (2nd order Lenkwitz-Riley) includes a 5.0 Mh inductor in series with the woofer, and a 200 mF cap and a 3 ohm resistor in parallel. The inductor is an laminate core with a DCR of .25. The SB Acoustics woofer is 6 ohms.
My question is, what would the overall effect be, if I replaced that 5.0 mH inductor with an air core with a DCR of 1.2? I guess it would attenuate the bass output, but by how much? And would it do it over the entire range of the woofer's output?
Thanks!
Kairos Woofer Write up
These woofer modules are not subwoofers, but designed to create a 3 ways system when used with a standmount/monitor speaker.
The design, for the low pass portion of the crossover (2nd order Lenkwitz-Riley) includes a 5.0 Mh inductor in series with the woofer, and a 200 mF cap and a 3 ohm resistor in parallel. The inductor is an laminate core with a DCR of .25. The SB Acoustics woofer is 6 ohms.
My question is, what would the overall effect be, if I replaced that 5.0 mH inductor with an air core with a DCR of 1.2? I guess it would attenuate the bass output, but by how much? And would it do it over the entire range of the woofer's output?
Thanks!
Kairos Woofer Write up
Not only will the higher resistance of the air core inductor lower the woofer's output, it will increase its Qts and effect the tuning frequency of the enclosure for the woofer. While these effects might be inaudible or very small, the woofer's enclosure will no longer be optimally tuned.
Paul
Paul
I know many think this is a waste of money and real-estate but the 10AWG 5.0mH air core inductors direct from Solen are going to have the lowest distortion and meet the schematic specifications while also being the least expensive of the air core brands at this gauge/L value.
Is there a point to modifying x/o parts of the kit? Do you believe original designer wasn't competent enough?
If so, why can't you start from scratch?
If so, why can't you start from scratch?
Thanks for the responses!
The main reason why I was considering trying to find an air core to replace the laminate core, is mostly cosmetic.
I am planning on building the crossovers in outboard enclosures, and air core will look better, IMO. I have some aluminum boxes with plexi tops to show them off.
Obviously, I think Jeff Bagby was a great speaker designer. I have a pair of his Auricle kits that I think are comparable to speakers that would cost at least 3X as much at the retail level.
The main reason why I was considering trying to find an air core to replace the laminate core, is mostly cosmetic.
I am planning on building the crossovers in outboard enclosures, and air core will look better, IMO. I have some aluminum boxes with plexi tops to show them off.
Obviously, I think Jeff Bagby was a great speaker designer. I have a pair of his Auricle kits that I think are comparable to speakers that would cost at least 3X as much at the retail level.
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Hmmm. Where I come from, Qtc is derived from Vas, Qes and Qms, and the port. Re is not in that equations.
1 Ohm additional resistance may be enough to change the response as it is 16%. I agree, As long as you don't play insane levels and saturate the core, which the laminate is somewhat more resistant to than a sintered core, the additional distortion and considering it is in the bass, I seriously doubt would be audible.
If you have the parts already, you can always build it with the iron core, then add a 1 Ohm and see if you hear a difference.
Of course, esthetics is up to you.
I don't know where you come from but Qms and Qes are measured parameters and Qts (not Qtc) is mathematically derived only from them just like a pair of paralleled resistors. Thus, if resistance is added in series with a driver, Qes is increased followed by an increase in Qts. An increase in Qts requires the tuning frequency to be lower.
Paul
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I assume the curve with the 2-dB peak at ~60 Hz shows the effect of the higher resistance of the air-core inductor as compared to the other curve with the lower resistance of the specified laminate inductor?
Paul
I looked it up, and if I'm not mistaken it's 0.24Ω
I thought it was a little too much difference, higher than I normally expect. So I looked into it and it seems the parallel section of the crossover pulls the impedance down enough to make the inductor resistance have more effect.
I thought it was a little too much difference, higher than I normally expect. So I looked into it and it seems the parallel section of the crossover pulls the impedance down enough to make the inductor resistance have more effect.
Okay, but is my assumption correct about the pair of curves and what they represent correct?
Paul
Yes. The only difference between the sims is the resistance of the coils. Here is the schematic and beside it is the factory traced impedance per driver sans crossover.
You beat me to making a similar comparison and you have confirmed what I stated regarding the effects of adding resistance in series with a driver's coil will be; a lower tuning frequency will be necessary. Whether the difference would be audible or objectionable if not taken into account is perhaps debatable.
Paul
Qtc is the lumped (viz 'total') damping of a loudspeaker drive unit, including all constants, in a sealed enclosure, although it has sometimes been used to define it in other loads.
Qts is the electromechanical damping of a loudspeaker drive unit, nominally under free air conditions, and defined by the equation Qts = (Qes * Qms) / (Qes + Qms). Since there is no port involved, no such constant is included in its derivation. Neither is Vas, although Re certainly is in the background, because it's part of the derivation for Qes:
Qes = (2pi * Fs * Mms * Re) / B*L^2
Qms = (2pi * Fs * Mms) / Rms
Effective Qts' = Qts + any series resistance in circuit plus as relevant the output impedance of the amplifier, as both are equivalent to raising Qe & thereby Qt. Therefore, as has been noted above, when designing, if a specific LF alignment is desired effective Qts' is what should be used. Per usual, as [effective] Qt increases, so you either need to increase Vb, lower Fb, or both, until such a point as you exceed the range in which a given alignment type / shape can be achieved & you need to consider alternatives.
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