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Overlapping Xover bandpasses/points

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taurusty View Drop Down
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    Posted: 18 September 2017 at 2:24pm
Good Morning SP'ers!

Regarding the captioned; is there any benefits to be gained? Have always been of the opinion that with quality components & flat(ish) response it's a waste of power and affects phase negatively.

Secondly, I have always used the same crossover type & slope on each side of a bandpass, again for phase reasons and using flattish components. I note the DBX Venu360 manual states assymetric slopes are no problem.

Any comments?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dj jammin Quote  Post ReplyReply Direct Link To This Post Posted: 18 September 2017 at 7:15pm
I'm also very interested in this topic..  What crossover slope are most people using? Is there any advantage to using 12dB slopes rather than 24 when using active crossovers? I assumed 24dB per octave is the 'standard' (?) and 12dB is mainly used in passive crossovers?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Requiem Quote  Post ReplyReply Direct Link To This Post Posted: 18 September 2017 at 9:11pm
Also interested in the outcome of this convo. In the past I have intentionally overlapped crossover points as long as the delays were set correctly. I don't do this anymore, but always thought it sounded pretty good at the time. Only on subs and then kicks though
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 18 September 2017 at 9:31pm
Originally posted by dj jammin dj jammin wrote:

I'm also very interested in this topic..  What crossover slope are most people using? Is there any advantage to using 12dB slopes rather than 24 when using active crossovers? I assumed 24dB per octave is the 'standard' (?) and 12dB is mainly used in passive crossovers?

Good hi-fi sounds better than 24db slopes, doesnt?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 18 September 2017 at 10:25pm
No crossover filter is a perfect brick wall so there is always overlap between bands.

For low power levels with nearly perfectly behaved home audio drivers a 6 or 12db crossover can deliver very good results, but at PA system power levels and with drivers that often behave less gracefully outside of pass band a 24db crossover is the minimum acceptable slope IMO, anything less just produces way too much overlap and exposes the drivers to potentially damaging power levels below box tuning or horn cutoff.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gen0me Quote  Post ReplyReply Direct Link To This Post Posted: 18 September 2017 at 10:48pm
You can always put weak slope and after fast one. If you know horn cutoff.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 19 September 2017 at 12:06pm
Originally posted by taurusty taurusty wrote:

Good Morning SP'ers!

Regarding the captioned; is there any benefits to be gained? Have always been of the opinion that with quality components & flat(ish) response it's a waste of power and affects phase negatively.

Secondly, I have always used the same crossover type & slope on each side of a bandpass, again for phase reasons and using flattish components. I note the DBX Venu360 manual states assymetric slopes are no problem.

Any comments?


There is too much phase issues outside 18 dB per octave for my taste in addition, the sharp cutoff makes things sound too ear fatiguing based on my analysis. I use 12 dB per octave. I carry enough boxes so, trying to extract every bit of SPL with the least amount of boxes is not my cup of tea. 

There is a video I made on my Youtube channel showing the affects of phase once you increase the dB slope.

Best Regards, 

Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 19 September 2017 at 12:42pm
Originally posted by Elliot Thompson Elliot Thompson wrote:

Originally posted by taurusty taurusty wrote:

Good Morning SP'ers!

Regarding the captioned; is there any benefits to be gained? Have always been of the opinion that with quality components & flat(ish) response it's a waste of power and affects phase negatively.

Secondly, I have always used the same crossover type & slope on each side of a bandpass, again for phase reasons and using flattish components. I note the DBX Venu360 manual states assymetric slopes are no problem.

Any comments?




There is too much phase issues outside 18 dB per octave for my taste in addition, the sharp cutoff makes things sound too ear fatiguing based on my analysis. I use 12 dB per octave. I carry enough boxes so, trying to extract every bit of SPL with the least amount of boxes is not my cup of tea. 

There is a video I made on my Youtube channel showing the affects of phase once you increase the dB slope.

Best Regards, 



In isolation sure but all filter design should be based upon the drivers response in the box and it’s interaction with other parts of the system - at various onax and offax positions. 4th order slopes are most common because with careful box design they become relatively easy to align with an allpass or delay.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 19 September 2017 at 1:12pm
Originally posted by toastyghost toastyghost wrote:

Originally posted by Elliot Thompson Elliot Thompson wrote:

Originally posted by taurusty taurusty wrote:

Good Morning SP'ers!

Regarding the captioned; is there any benefits to be gained? Have always been of the opinion that with quality components & flat(ish) response it's a waste of power and affects phase negatively.

Secondly, I have always used the same crossover type & slope on each side of a bandpass, again for phase reasons and using flattish components. I note the DBX Venu360 manual states assymetric slopes are no problem.

Any comments?




There is too much phase issues outside 18 dB per octave for my taste in addition, the sharp cutoff makes things sound too ear fatiguing based on my analysis. I use 12 dB per octave. I carry enough boxes so, trying to extract every bit of SPL with the least amount of boxes is not my cup of tea. 

There is a video I made on my Youtube channel showing the affects of phase once you increase the dB slope.

Best Regards, 



In isolation sure but all filter design should be based upon the drivers response in the box and it’s interaction with other parts of the system - at various onax and offax positions. 4th order slopes are most common because with careful box design they become relatively easy to align with an allpass or delay.


The driver's response in the enclosure is only part of it in the eyes of a Manufacture. Manufactures use a proprietary designed passive crossover network within their enclosures. So they can get away with things the Do It Yourself person cannot. Manufactures realize the majority of their customers will sacrifice sound quality to a degree for high dB levels. Under those conditions manufactures tend to put maximum dB before thermal breakdown at the forefront with Sound Quality being secondary.


Best Regards,    



Edited by Elliot Thompson - 19 September 2017 at 1:16pm
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taurusty View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote taurusty Quote  Post ReplyReply Direct Link To This Post Posted: 19 September 2017 at 2:16pm
Good morning. Thanks for all comments/contributions.

Any comments on the second question, i.e., mixing say, BW 18db/oct and LR 24 db/oct on either side of a lo mid bandpass of say 100hz to 300Hz as an example? What are the sonic implications for the <100hz bandpass if that is crossed using for example, L/R 24 db/oct on the lo pass section.

Is the rule all bandpasses same type/slope or whatever works?


Edited by taurusty - 19 September 2017 at 2:17pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 19 September 2017 at 2:42pm
It depends on the driver and box. You need to measure and set crossover filters to ensure that the different bands are phase aligned. It is typical for electrical crossover filters to be chosen to allow for the desired acoustic crossover point to be at -6dB points for each passband, which should sum to flat or close when phase aligned using delay or allpass filters.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 19 September 2017 at 3:30pm
The end goal with any crossover is flat summed response in terms of amplitude and phase/time, so there is nothing wrong with using asymmetrical crossovers if it produces the above result.
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