John Warren Posted February 25, 2012 Share Posted February 25, 2012 Filter schematic at bottom of page. Design attempts to attenuate "hump" in bass response. If iron core Ls and polyester Cs are used, cost is low. So, if you build it and you don't find it to your taste, its not a large investment and you've learned something. It's offered as a project. It's an interesting modification. The current version of the Klipschorn filter (AK-5?) uses a similar approach as did the AK-4. The filter alters the response in the frequency domain. http://www.northreadingeng.com/Klipschorn_notch/Notch_Filter.html Quote Link to comment Share on other sites More sharing options...
Guest " " Posted February 25, 2012 Share Posted February 25, 2012 Overall, a good idea. So I looked at your schematic and that of the AK-4 for the notch filter, they are very similar.....but I think it might be worth clarifying, this is/is not intended to be used with the AK-4 or AK-5 since they already have one and the component values are pretty close functionally ? I don't think it's worth the trouble to disable the onboard AK-4 or AK-5 to replace with this one (the only major difference is the series inductor and pro's and con's about using a 6mh vs 13mh might be ambiguous) So is this intended for AK-3, AK-2 xovers? I don't think the ALK Universal uses a notch filter so would it work there? The ALK ES line I think uses a notch filter so maybe not intended for use with ES xovers? What about the ALK gentle slope xovers? it would work with Bob's AK-3 and AK-2 xovers. I think the point being folks need to understand notch filters are good....but they might already have one. A list of which xovers don't have one would be helpful. What about the LaScala? AL-4 and AL-5 uses a notch filter. There's some crazy stuff happening in the LaScala bass bin when using xovers with out notch filters like the AL-3 and AA . The Al has a notch filter. Quote Link to comment Share on other sites More sharing options...
John Warren Posted February 25, 2012 Author Share Posted February 25, 2012 For the Klipschorn, I'm not aware of notches used in any net other than the AK-4, -5 To validate the response of the notch requires the horn output to be measured and, for a Klipschorn, this is a challenge. The technique I'm using (which requires altering the horn in a way that is not reversible) appears to produce a magnitude response consistent with the factory results. It will work with AK, AK-2, -3, AA, A. For other suppliers such as ALK or BEC, it's not clear to me, I haven't considered them. The notch is specific to the Klipschorn, it will not work properly in Lascala. I would suggest building the LF filter as is shown in the schematic as a stand alone and use mid and HF filter sections from factory network. Thanks for the input. ps. giving up sensitivity for linearity. p.p.s if Bob's are copies of the factory nets, it should work with those also. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted February 25, 2012 Share Posted February 25, 2012 jubilee passive has notch filters Quote Link to comment Share on other sites More sharing options...
Guest " " Posted February 25, 2012 Share Posted February 25, 2012 LaScala type AL has notch filters Quote Link to comment Share on other sites More sharing options...
Guest " " Posted February 25, 2012 Share Posted February 25, 2012 Belle AB-3 has notch filters Quote Link to comment Share on other sites More sharing options...
John Warren Posted February 25, 2012 Author Share Posted February 25, 2012 The Jub LF filter with and without notch. The notch increases attenuation above 400Hz big time. Quote Link to comment Share on other sites More sharing options...
LarryC Posted February 25, 2012 Share Posted February 25, 2012 What about the DeanG K-horn filter, do you know? Does it have a bass horn notch filter? Thanks, Quote Link to comment Share on other sites More sharing options...
John Warren Posted February 25, 2012 Author Share Posted February 25, 2012 What about the DeanG K-horn filter, do you know? Does it have a bass horn notch filter? Thanks, Don't know but if it's a copy of AK-4 then it does. Post a photo, should be easy to determine. Quote Link to comment Share on other sites More sharing options...
djk Posted February 26, 2012 Share Posted February 26, 2012 John, may we ask the design DCR of your L2 (12.9mH)? One could use an inexpensive inductor by adjusting the total R of R2~R5 + DRC of L2 to keep the Q of the notch the same. C3~C6 should be low ESR (film type, not electrolytic) to maintain proper filter Q. Oh, nice work! Quote Link to comment Share on other sites More sharing options...
John Warren Posted February 26, 2012 Author Share Posted February 26, 2012 Thank you. The inductor DCR is about 0.4 Ohms, It's an unwind from a Janzten 15mH powder core. The resistors are simple wire wound. Caps in the prototype are Jentzen or Solen (polyetheylene film). The filter shown in the schematic will present a minimum impedance magnitude of 3.8 Ohms to the amplifier over the stop band. That, plus improving linearity of the frequency response were "design goals". Tweaking is fine as long as one is aware that there are relationships between inductor DCR, inductance, total power dissipation, total capacitance, horn magnitude response, impedance magnitude and so on. Amplifier can get damaged or, at best, shut down if the notch is tweaked into no-man's land. I've used polyethelyene and polyester film caps. Quote Link to comment Share on other sites More sharing options...
Greg Oshiro Posted February 26, 2012 Share Posted February 26, 2012 <snip> To validate the response of the notch requires the horn output to be measured and, for a Klipschorn, this is a challenge. The technique I'm using (which requires altering the horn in a way that is not reversible) appears to produce a magnitude response consistent with the factory results.<snip> John-- Hey! Another measurement-type guy! What do you think of this LF measurement idea? http://community.klipsch.com/forums/t/160262.aspx --Greg Quote Link to comment Share on other sites More sharing options...
LarryC Posted February 27, 2012 Share Posted February 27, 2012 Don't know but if it's a copy of AK-4 then it does. Post a photo, should be easy to determine. I don't have Dean's xover. Maybe he'll chime in. Quote Link to comment Share on other sites More sharing options...
John Warren Posted February 27, 2012 Author Share Posted February 27, 2012 Impedance magnitude comparison between bass horn, no filter RED (no notch, no low pass) and the folded unit with notch+ low pass BLUE between 30-1000Hz. Quote Link to comment Share on other sites More sharing options...
John Warren Posted February 27, 2012 Author Share Posted February 27, 2012 Complex impedance over the same range, BLUE is notch + low pass, RED is stand alone folded unit. Quote Link to comment Share on other sites More sharing options...
John Warren Posted February 27, 2012 Author Share Posted February 27, 2012 A closer look over the range where the notch is active. Note that the loops, which indicate reflections, are reduced. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted February 27, 2012 Share Posted February 27, 2012 The AK-4 uses a notch filter in the LF and MF section Quote Link to comment Share on other sites More sharing options...
John Warren Posted February 28, 2012 Author Share Posted February 28, 2012 The AK-4 uses a notch filter in the LF and MF section This is the first I've seen a factory schmeatic of the AK-4. Now folks can build both and compare the diiferences. The factory unit will produce about 2dB additional attenuation (and a bit more phase error). I looked at a very wide range of Q values for this project including more than a single notch (sometime in the late 80s btw).. The model responses are provided as comparison below (AK-4 brown, KS2 blue). The simualtion loads each filter with a simulated Klipschorn load. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted February 29, 2012 Share Posted February 29, 2012 This is the first I've seen a factory schmeatic of the AK-4. Now folks can build both and compare the diiferences. The parts count has made this a vary unpopular DIY xover. They don't come up for sale on the forum often, and sell fast when they do. Quote Link to comment Share on other sites More sharing options...
John Warren Posted March 10, 2012 Author Share Posted March 10, 2012 What do you think of this LF measurement idea? http://community.klipsch.com/forums/t/160262.aspx --Greg What are the results using your approach? Do you have any measurements? Quote Link to comment Share on other sites More sharing options...
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