Klipschguy Posted July 1, 2022 Share Posted July 1, 2022 Greetings, Does a notch filter (for instance, to tame the midband frequencies of an Altec 802D driver) depend on the impedance of the driver? In other words, will the notch filter designed for an 8 ohm diaphragm also work for for a 16 ohm diaphragm? Thanks, Andy Quote Link to comment Share on other sites More sharing options...
billybob Posted July 1, 2022 Share Posted July 1, 2022 5 hours ago, Klipschguy said: Greetings, Does a notch filter (for instance, to tame the midband frequencies of an Altec 802D driver) depend on the impedance of the driver? In other words, will the notch filter designed for an 8 ohm diaphragm also work for for a 16 ohm diaphragm? Thanks, Andy Abit esoteric but, until you can do better here, would think it would work. How much or to what extent could be interesting. Regardless of any supposed impedence. @Klipschguy 1 Quote Link to comment Share on other sites More sharing options...
babadono Posted July 1, 2022 Share Posted July 1, 2022 Are you talking about speaker level as in a filter in a speaker crossover? If so then yes the load impedance the filter is feeding into will effect the notch filter. Sorry that's electrical engineering and physics and such. Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted July 1, 2022 Author Share Posted July 1, 2022 Thanks, BillyBob. See the picture for what I have in mind. This picture/schematic is the Altec factory designed midrange compensation network to reduce/notch the mids to allow less relative roll-off of the highs in 2-way system when utilizing an 802D driver. So, the circuit will operate the same whether the driver is 8 or 16 ohms? Andy P.S. I miss Gil; this question would be right up his alley. 1 Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted July 1, 2022 Author Share Posted July 1, 2022 BD, when I look at notch filter equations, they do not have impedance in the equation. Online notch filter calculators do not ask for driver impedance either. BTW, I am a student science and engineering as well. Andy 1 Quote Link to comment Share on other sites More sharing options...
babadono Posted July 1, 2022 Share Posted July 1, 2022 Ok learn something new everyday. Load impedance does not effect a filter feeding it. Quote Link to comment Share on other sites More sharing options...
billybob Posted July 1, 2022 Share Posted July 1, 2022 Cool... Let's see if others chime in. Otherwise, would try it as can see no harm. Quote Link to comment Share on other sites More sharing options...
Khornukopia Posted July 1, 2022 Share Posted July 1, 2022 6 hours ago, Klipschguy said: Greetings, Does a notch filter (for instance, to tame the midband frequencies of an Altec 802D driver) depend on the impedance of the driver? In other words, will the notch filter designed for an 8 ohm diaphragm also work for for a 16 ohm diaphragm? Thanks, Andy 25 minutes ago, Klipschguy said: BD, when I look at notch filter equations, they do not have impedance in the equation. Online notch filter calculators do not ask for driver impedance either. BTW, I am a student science and engineering as well. Andy Are you asking if it does or, are you telling us it doesn't? Quote Link to comment Share on other sites More sharing options...
Edgar Posted July 1, 2022 Share Posted July 1, 2022 There is no notch filter in that circuit. SPICE simulations using 8 Ohm and 16 Ohm resistive for HF: Quote Link to comment Share on other sites More sharing options...
babadono Posted July 1, 2022 Share Posted July 1, 2022 All I know is if you try and run a short it will make no sound Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted July 1, 2022 Author Share Posted July 1, 2022 Kornukopia, I am definitely asking. The “Altec 3904” is supposed to attenuate the mid frequencies leaving the highs in tact. In the schematic, the high frequency driver has an attenuation filter, the low frequency driver has a zoebel network to equalize the impedance. The “Altec 30923” only has the midrange attenuation circuit - no zoebel. My question is will this attenuation unit have to modified to work with a 16 ohm driver? I would ask this question on the Altec heritage forum, but as a lifelong Klipsch listener and owner and member of this forum for over 20 years, I have really come to respect the knowledge and opinions found on this board. Andy P.S. Edgar, thank you most kindly for taking time to run the curves; I am not sure what think yet. Please know I am not doubting, it just doesn’t seem to make sense Altec would design an attenuation circuit that doesn’t attenuate. It’s kinda like having a machine that goes “ping” but nothing else. Quote Link to comment Share on other sites More sharing options...
Edgar Posted July 1, 2022 Share Posted July 1, 2022 3 minutes ago, Klipschguy said: P.S. Edgar, thank you most kindly for taking time to run the curves; I am not sure what think yet. Please know I am not doubting, it just doesn’t seem to make sense Altec would design an attenuuation circuit that doesn’t continuate. It’s kinda like having a machine that goes “ping” but nothing else. Looks more like a HF horn driver compensation circuit. HF response starts to roll-off at some high frequency due to mass reactance. Boosting the highs (or attenuating the lows) in the HF circuit compensates for that. Some horns compensate by collapsing the coverage angle in favor of the on-axis response, in which case the circuit is not needed. https://sound-au.com/project173.htm Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted July 1, 2022 Author Share Posted July 1, 2022 Yes exactly! Are these circuits impedance dependent? By the way, I skimmed over the article and I see it has good information; when I have more time I am planning to read it more carefully. Thank you for posting! Quote Link to comment Share on other sites More sharing options...
Edgar Posted July 1, 2022 Share Posted July 1, 2022 13 minutes ago, Klipschguy said: Yes exactly! Are these circuits impedance dependent? Well, yes. The 8 Ohm version has 3 dB more attenuation below 1 kHz than the 16 Ohm version. Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted July 1, 2022 Author Share Posted July 1, 2022 Hmmm…3db more attenuation for the 8 ohm versus the 16 ohm. So, the high frequencies from the 8 ohm driver will effectively have 6dB more SPL relative to the 16 ohm driver (3dB more mid attenuation relative to the highs plus 3dB more sensitivity from the lower 8 ohm driver impedance)? It seems like the curves would intersect of that were the case. Interesting. Please know your input is very much appreciated! Quote Link to comment Share on other sites More sharing options...
Edgar Posted July 1, 2022 Share Posted July 1, 2022 2 minutes ago, Klipschguy said: So, the high frequencies from the 8 ohm driver will effectively have 6dB more SPL relative to the 16 ohm driver (3dB more mid attenuation plus 3dB more sensitivity from the lower 8 ohm impedance)? Assuming that the 8 Ohm driver will be 3 dB more sensitive than the 16 Ohm driver may or may not be valid -- you'd have to check with Altec or GPA about that. If the assumption is valid, then for the same voltage input to the circuit, below 1 kHz both drivers will have the same acoustic output -- 3 dB more attenuation in the circuit compensated by 3 dB more sensitivity in the driver. At 20 kHz, where both versions have about the same voltage output regardless of the driver impedance, the 8 Ohm driver will be 3 dB louder than the 16 Ohm driver. 2 1 Quote Link to comment Share on other sites More sharing options...
Klipschguy Posted July 1, 2022 Author Share Posted July 1, 2022 Thanks, Edgar. I appreciate your time and insight. Andy 1 Quote Link to comment Share on other sites More sharing options...
DavidF Posted July 2, 2022 Share Posted July 2, 2022 Every change in impedance in one position in the circuit will ripple throughout the circuit to some degree, large or small. It becomes really difficult to assume inserting components into a circuit tuned to one set of variables won't significantly alter the intended effect of the total circuit. Quote Link to comment Share on other sites More sharing options...
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