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View Full Version : quick question about LPF and HPF



tank65
02-01-2007, 01:02 AM
so im filling out this form for team toxic bass on a phase box... and its asking for lpf cut off and hpf cut off. im taking it i put 34hz in lpf as thats what i want it tuned to? or am i wrong. and if i was right on the first part what should i put on my hpf cut off

ffkk
02-01-2007, 06:22 AM
whats a phase box? Or are you talking about a bandpass box which has LPF and HPF?

nismos14
02-01-2007, 04:21 PM
Lpf and hpf are filters, there's no filter in boxes.....

ffkk
02-02-2007, 02:42 AM
Lpf and hpf are filters, there's no filter in boxes.....


From what I have read, bandpass boxes provide rolloff at a high frequency and low frequency providing a bandpass filtering of signals. a 6th order will provide a higher rolloff frequency than a 4th order and so forth. frequencies within the pass band are raised for a flatter response in that band.

but I could have read wrong :D . Perhaps you can enlighten me on how they work.

nismos14
02-02-2007, 08:03 AM
You're right, I'm probably just not in the loop about these phase boxes :)

helotaxi
02-02-2007, 09:42 AM
Order has to do with rate of rolloff, not frequency. There are a lot of things that can be done with bandpass boxes and the overwhelming majority do not have a flat response within the passband but rather accentuate one frequency. Those that do have a really flat frequency response are either really efficient with a really narrow passband (still effectively accentuating a small frequency range) or are fairly inefficient but have a broader bassband.

The hpf and lpf referenced in the form are high pass *frequency* and low pass *frequency* not filter. The hpf should be the bottom of the passband and the lpf should be the top.

bikinpunk
02-02-2007, 09:46 AM
I'm just curious...is the benefit still there if you have an amp/processor that will controll rollofs, q, center frequency, etc? Seems to me that would negate the need for a one of these boxes?

ffkk
02-02-2007, 09:54 AM
I'm just curious...is the benefit still there if you have an amp/processor that will controll rollofs, q, center frequency, etc? Seems to me that would negate the need for a one of these boxes?


Perhaps, but that would mean turning the eq up on that frequency you want higher, and making your amp work harder. The bandpass would do it for you.

You are correct Halo, I meant the rate of roll-off. my english went a bit blurry there:D .

as the rate of roll-off is higher, the gain outside the passband drops much quicker than with other enclosures, almost like using active or passive crossovers. Or am I wrong?