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|4th May 2009, 02:43||#1|
Senior - BHPian
Join Date: Mar 2006
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Slope? Active v/s Passive???
I was just reading about Slopes on Basic Car Audio Electronics, and I got mighty confused. Can someone clear the concept of Slopes and explain what roll off means?
Also, I wanted this knowledge to apply to my present setup.
What slope settings are considered ok?
In my 9887, I set the fronts, the rears and the sub to 12dB.
what does this mean? I just did what Bass&Trouble instructed me to do and it sounded awesome. BUT i want to know what it exactly means.
One more question!
We do not have an Active V/S Passive thread on team-bhp, and with so many of us owning some decently respectable equipment, we MUST speak of the pros and cons of each, thus prompting many of us here to take the plunge and go active.
PS: While answering questions, can we keep our first few explanatory posts a little simple, and then have the knowledge gradient go up slowly? We don't want to scare everyone away
PS: This didnt help much
Last edited by frankmehta : 4th May 2009 at 02:56.
|4th May 2009, 08:10||#2|
Join Date: Mar 2004
Thanked: 4,282 Times
In general any slope made by a passive filter can be duplicated using small signal components (aka an active filter). This includes Butterworth, Linkwitz-Riley, Bessel, Chebyshev, Sallen-Key, inverse Chebyshev, etc..
A fiilter (high pass or low pass) has a cut off point point and a roll off. The cutoff point for most filters (except L-R) is accepted as the point at which the filter is -3db below it's nominal voltage.
A designer chooses a filter topology (Bessel, Butterworth, etc..) based on thier needs. In addition to the "standard" topologys" there are various other topologies that are created just to compensate for the anamolies of a particular component (in this case in the audio chain). VMPS for example uses slopes that are variable meaning that the slope is -6db/octave for about 1/2 an octave and then fall faster after that.
1. flat amplitude response
2. Phase response is NOT linear
3. phase shift is nonlinearly with frequency
4. each frequency have a different time delay
5. ringing in step response due to overshoot
1. overshoot and ripples - more than butterworth or bessel
2. Linear phase response
1. Linear phase response
2. phase shifts are linear with frequency
3. slower roll off hence little driver protection
Effectively a modified Butterworth filter where the cut off point is -6db down. This filter has a flat power response (not the same as flat amplitude response as amplitude often refers just to the voltage).
In addition to the regular high pass and low pass filters are special filters such as ladder networks used to time align drivers (See John "Zaph" Krutke's ZD5 design)
Zaph|Audio - ZD5 - Scan Speak 15W8530K00 and Vifa XT25
This link explains things in more detail
Filter Solutions Descriptions
Active filter design is explained here
Design and Dimensioning of Active Filters
Free Filter calculators, active filter design, chebyshev filters, Bessel filters, butterworth filters
and heres a quick design helper but it is not complete
Butterworth / Bessel / Chebyshev Filters
|4th May 2009, 09:34||#3|
Join Date: Mar 2009
Thanked: 168 Times
Read in http://www.team-bhp.com/forum/ask-gu...ng-active.html that active means having HIGH, MIDS and LOWS, but there is also said that no rear fills can be possible, but if we set tweeters at 3KHz LPF, Midbass at 3KHz HPF and 80Hz at LPF and the sub at 80Hz HPF, so the tweeters play the highs so can t we use 4 midbass? just a question.
Also related to what you had said, all are flat amplitude and flat power response, so does this mean we are running the equlizer at 0 for all? i prefer to have alot of bass and a bit more of midbass and almost equal but a little more of highs, so what is that called?
Sorry for being such a noob
|4th May 2009, 10:21||#4|
Join Date: Mar 2004
Thanked: 4,282 Times
Last edited by navin : 4th May 2009 at 10:24.
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