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Silly notch filter question

nitrous

nitrous

pfm Member
Ok so to the experts, this will be a daft question, but I'm confused:confused:

I'm busy messing around with a pair of full range driver CSS FR 125s I built into some cabinets (for a bit of fun). Some reading up has revealed a notch filter can smooth things out a bit....so I got the inductors, caps, resisters etc. the diagram

http://www.vikash.info/audio/FR125S/filters.asp

appears to show these are all on the + side only. But further reading elsewhere shows these parts go across the +and - terminals. What is the correct layout please?

I know if I have to ask I shouldn't be doing it, but it ain't high voltage and it is just a bit of fun learning:D.......which beats work any day of the week:p

Cheers for any help.

Nitrous
 
That would look to be on the + side only, AFAICS. I'm not sure it will necessarily work though and I suspect you may prefer it without. But no harm in trying. Your cabinets would need to be exactly the same dimensions at the very least and I'd be very impressed if you got that axial response.
 
Chris, thanks for reply. If I understand you correctly, in the example I showed the design appears to be on the + side and could work. Equally another design may be to put components across the terminals? I was thinking that only one of the arrangements would be electrically correct in my ignorance!

Cheers
 
There are several different ways notch filters can be done.

For a wide range driver, the standard way is the one shown on Vikash's site.

In multi-way systems, the notch often gets integrated into the crossover, and rather than a parallel tuned circuit (high impedance at resonance) in series with the driver, a common method is to use a series tuned circuit (minimum impedance at resonance) in parralell with the driver. If you used this in a wide range driver, it just shorts out the amplifier at some frequency, but in a system with a crossover, there is some other component between amp and driver, and so the impedance minimum gives lots of extra attenuation at that frequency.
 
nitrous said:
Chris, thanks for reply. If I understand you correctly, in the example I showed the design appears to be on the + side and could work. Equally another design may be to put components across the terminals? I was thinking that only one of the arrangements would be electrically correct in my ignorance!

Cheers
Click to expand...

Yup, exactly as in the drawing. Putting it across the speaker would do nothing in this instance, as PD says. One thing, if you get a less than convincing result with both, there is always the option of using just one of them. That would probably be the higher one as there is a very real resonance there.

Good luck.

CT
 
PigletsDad, thanks for taking time to explain that for me, all part of my learning and hanging around PFM!

Chris, As it happens I have now wired up the one filter (higher) as you are suggesting as a test.

Cheers for replies
 
PigletsDad said:
There are several different ways notch filters can be done.

For a wide range driver, the standard way is the one shown on Vikash's site.

In multi-way systems, the notch often gets integrated into the crossover, and rather than a parallel tuned circuit (high impedance at resonance) in series with the driver, a common method is to use a series tuned circuit (minimum impedance at resonance) in parralell with the driver. If you used this in a wide range driver, it just shorts out the amplifier at some frequency, but in a system with a crossover, there is some other component between amp and driver, and so the impedance minimum gives lots of extra attenuation at that frequency.
Click to expand...
Just to add to what PD said ...

The parallel notch (which is connected in series with the driver) as shown is generally used where the attenuation applies within the intended bandpass of the driver. This is less deleterious for sound reproduction.

The series notch (which is connected in parallel, shunted to ground) is used to attenuate break-ups beyond the intended passband. Seas magnesium midbass drivers, which break up around 8-12kHz, are typically 'controlled' by these. These series filters are more 'brutal', and therefore more effective at controlling spurious out-of-band resonances.

James
 
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