80 HZ high pass crossover frequency [Archive] - Audio & Video Forums

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edlchiang62
03-01-2006, 07:18 AM
Sorry to ask another basic question, but when a subwoofer is said to have an 80HZ high pass crossover frequency with a 6dB/ocatve slope, does that mean there is absolutely no 80 HZ info sent to the main speakers and a gradual increase of 6dB/octave at frequencies above 80 HZ or is there full 80HZ info sent to the main speakers and a gradual decrease of info at a rate of 6dB/octave slope below 80HZ? I hope my question isn't confusing.

kexodusc
03-01-2006, 11:15 AM
Sorry to ask another basic question, but when a subwoofer is said to have an 80HZ high pass crossover frequency with a 6dB/ocatve slope, does that mean there is absolutely no 80 HZ info sent to the main speakers and a gradual increase of 6dB/octave at frequencies above 80 HZ or is there full 80HZ info sent to the main speakers and a gradual decrease of info at a rate of 6dB/octave slope below 80HZ? I hope my question isn't confusing.

The filter in the subwoofer doesn't completely cut off the 80Hz signal...But I don't generally see it described as you've written. A 6dB/octave slope, high pass at 80Hz would imply that the signal is up 6 dB at 160Hz. Can't imagine a sub being made that only has a 6 dB/octave low pass filter.

RJW1138
03-03-2006, 08:42 AM
Sorry to ask another basic question, but when a subwoofer is said to have an 80HZ high pass crossover frequency with a 6dB/ocatve slope, does that mean there is absolutely no 80 HZ info sent to the main speakers and a gradual increase of 6dB/octave at frequencies above 80 HZ or is there full 80HZ info sent to the main speakers and a gradual decrease of info at a rate of 6dB/octave slope below 80HZ? I hope my question isn't confusing.

First of all, I just want to make sure that you're indeed talking about the high pass filter, and not the low pass filter. The high pass filter is what you'd use if you were sending your main speaker signals to your sub, having it do high-pass filtering on this signal, and then passing the resultant signal on to your speakers. Is this what you're referring to?

Anyways, your 2nd guess is the correct one. Well, almost. The crossover point is not actually at 0db, but is rather the -3dB point. This is the standard way for measuring crossover points. So then, everything above 80-something Hz is passed through, 80Hz itself is -3dB below this, and the slope reduces everything below this by 6dB per octave (40Hz = -9dB, 20Hz = -15dB). Hope this is what you wanted to know.

edlchiang62
03-03-2006, 11:32 AM
Thanks for the info..I was about the high pass filter.