Disadvantages of Capacitor in series with main driver.

[Moondog55]

Let me see if I have any driver files suitable for a "Q" = 1.1 box or I could hash something up using factory data and post a page dump
EDIT
I had to go back and re-read the "Cookbook" to refresh my memory, now I do that I remember that this works best with heavy drivers with a high Qms, which the Kicker sub was [ very much so and needed no extra mass added] so if Petes woofers are light weight cones it won't work as well.

 

[PeteMcK]

' Unless you have a drawer full of 1000uF cap' - as it happens, I do have a box of scavenged high value caps!! Re: measurements, I did an impedance plot while measuring the parameters with ARTA, as it happens these have a high Qms, but I'm not going to spend much time on them at the mo, too many other projects backed up.... Got the Roadkill crossovers wired today, might get to assembling them tomorrow.....

 

[AllenB]

I went to Eminence's site and took a plot of the Alpha15a. They say it's Qts=1.26, my simmed fit was closer to 1 (first image). The next shot runs about 1,300uF. The impedance peak was about 40Hz.

 

[PeteMcK]

Hi Allen, thanks for your kind offer, can you work with the attached files? (Impedance plot & Unibox sim). I'm only really interested in what happens below ~200Hz. Cheers

 

[AllenB]

Here is 250uF. All values produce comparable results. The response EQs but the group delay wanders. It is not an ideal fix, presumably due to starting with such a high Q.

Proper EQ will still fix it properly.. this capacitor method remains as a simpler option.

 

[PeteMcK]

Cool thanks Allen, appreciate your time spent on this. Looks like it's a good Q&D fix for dodgy drivers, as long as you don't want to go much below Fs. The drivers I have on hand have Fs of 48Hz, so worth trying...

 

[DaveFred]

Here are two Dayton DA175-8 nearfield responses with a 560 cap in series and without in a sealed 10 liter box.





The flatter extended response is with the 560uf cap.

 

[Defo]

Would an aperiodic vent do the same thing?

 

[philpope]

does a high value resistor (~50ohm) in parallel with the woofer allow you to control the peak resistance and shape the bass response at resonance?

 

[peterbrorsson]

Here is 250uF. All values produce comparable results. The response EQs but the group delay wanders. It is not an ideal fix, presumably due to starting with such a high Q.

Proper EQ will still fix it properly.. this capacitor method remains as a simpler option.

The q of the box with driver needs 1-1.2 value, then play with everything between 300-1000uf! DaveFred has got it above...