Speaker filter question...

[bernieclub]

I recently dug out an old set of Hammer 12 full ranger plus tweeter speakers for service and I find there are two slightly different arrangements of crossover.    The 12 incher has a zobel directly across the speaker lugs.  Then there is a coil to roll off the highs, and a parallel notch filter in series.    Some schematics show the notch filter first, then the low pass coil.  Some show the low pass first, then the notch filter connected to the driver.  Does it matter which order these elements are connected?  TIA!

 

[Paul Birkeland]

If the notch filter and the coil are in series, then the order isn't important.  It is important that the zobel is last (positioned electrically across the voice coil).

 

[Jamier]

Bernie, when you say that the Zobel is connected across the speaker lugs, do you mean the binding posts where the speaker cables connect, or do you mean the terminals on the driver frame itself?

Jamie

 

[bernieclub]

The zobel is directly on the driver frame.  This had me scratching my head a little because I thought that each elements response was determined by the impedances immediately before and after.  I guess I better do some reading, thanks guys.

Bernie

 

[Jamier]

Bernie,

    Can you post a Xover diagram? The component values are not necessary, and maybe you can post both versions? The Zobel should be the last parallel circuit before the driver, I understand that it is wired across the terminals.

Jamie

 

[Paul Birkeland]

each elements response was determined by the impedances immediately before and after. 

A parallel notch filter uses a cap and inductor independently of load impedance.  The resonance just is what it is.  The resistive portion of the notch filter (if there is one) determines the attenuation. 

If you pick a frequency, say 1kHz, then convert all of the elements of the crossover into resistors, what effect is produced by swapping the notch filter and the low pass inductor?  Try this again for five or ten different frequencies. 

The series coil will always convert to a simple resistor if frequency is fixed, as will the notch filter.  Those resistances will always be in series with the load, so their ordering isn't critical.

 

[bernieclub]

PB, thanks for the detailed reply.  For some reason I'm not able to transfer pics from my phone, but here is crude schematic of the two versions....

                cap                                                                                      cap
    +-------resistor--------coil----zobel--driver                    +-----coil------res-------zobel--driver
                coil                                                                                      coil

Thanks again!
Bernie

 

[Jamier]

Bernie,

    Draw the two schematics, take a picture with your phone and email it to yourself. On your computer, pull the image(s) from your email onto your desktop and put them into the post. It’s not really clear what’s going on with the diagram from your last post.

Jamie

 

[bernieclub]

Got a new phone last week and for some reason, it's not letting me email to myself!  I'll sort this out today.    Basically, the cap/resistor/coil stack is wired in parallel creating the notch filter.  You'll notice that in the first schematic, the input goes through the notch filter first, then the low pass coil, then to the zobel and driver.  The second one has the low pass coil first, then the notch, then driver.

 

[Paul Birkeland]

I will again recommend picking a frequency, then turning all of the C's and L's into resistances (you can use an online calculator to do this, just search for "inductive reactance calculator" or "capacative reactance calculator" and you'll find them).  Once they are turned into resistances, you can apply 10V at the input and calculate what comes out.

 

[Jamier]

Bernie,

    I've been following this thread on my phone, not a computer. Today, I looked at it on a computer and now  realize that your diagram looked way different here, on the computer, than it  does on my phone. I never realized that the phone smooshed those graphics up that way. I see what's going on now. If those component values are  identical in the two Xovers, PB is right, as usual, they are the same.In general most Xovers will have the primary inductor placed first in line but, in this case, that's not necessary.

Jamie

 

[bernieclub]

I appreciate all the feedback...I plan to run through PB's exercise this evening.

Bernie