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Todays Stupid Question - DSP Crossovers
Todays Stupid Question - DSP Crossovers
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Old 8th September 2020, 04:41 PM   #1
garym999 is offline garym999  United Kingdom
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Default Todays Stupid Question - DSP Crossovers

With the advent of DSP's and using them for crossovers, why at the crossover point can't we just cut the signal? I understand the reason in the analog world but other than "thats the way we used to do it" I don't see why you can't just hand off from one speaker to the next?
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Old 8th September 2020, 05:02 PM   #2
picowallspeaker is offline picowallspeaker  Italy
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...harmonics reproduced by the same trasducer?
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Old 8th September 2020, 05:21 PM   #3
Markw4 is offline Markw4  United States
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Originally Posted by garym999 View Post
With the advent of DSP's and using them for crossovers, why at the crossover point can't we just cut the signal?
Do you mean, why not make a near-ideal brick-wall filter?
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Old 8th September 2020, 05:28 PM   #4
garym999 is offline garym999  United Kingdom
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Yes. Ie cut the woofer off a 3KHz and start the tweeter at 3KHz
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Old 8th September 2020, 05:56 PM   #5
CharlieLaub is offline CharlieLaub  United States
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Quote:
Originally Posted by garym999 View Post
With the advent of DSP's and using them for crossovers, why at the crossover point can't we just cut the signal? I understand the reason in the analog world but other than "thats the way we used to do it" I don't see why you can't just hand off from one speaker to the next?
You asked "why can't we". The answer is "we can".

You should probably be asking the question "why shouldn't' we" be doing that, or when should we do it and how should we do it.
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Old 8th September 2020, 06:02 PM   #6
scottjoplin is offline scottjoplin  Wales
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Very sharp cut offs can be achieved using active analogue elliptical filters.
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Old 8th September 2020, 07:14 PM   #7
MarcelvdG is offline MarcelvdG  Netherlands
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I can think of a couple of disadvantages:

When you make the filters very steep, you get a rather abrupt change in directivity. Besides, you get a very poor phase response with minimum-phase filters and a very long pre-echo with linear-phase filters. The woofer's and tweeter's pre-echoes are supposed to cancel each other, but will never perfectly do so.
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Old 8th September 2020, 07:30 PM   #8
digitalthor is offline digitalthor  Denmark
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My experience with digital filters, is that you are making a compromise. You can never do something perfect. And when a midrange has to work in unity with a tweeter, because the theoretical best sound, comes from a single source - you then have to make both drivers blend seamlessly in a way, that you dont notice the crossover.

You could do the opposite of the first order filters and try to make a very sharp filter. But you have to remember that a driver is a mechanical device, which take time to move and stop again - and the size plays a role too. Furthermore - you have to be extremely precise, to make sure that the tweeter does absolutely what the midrange does not - and vice versa. Herein lies the rub. We easily hear when something is out of tune. So even though it might work in theory - my guess is, that it will sound less good, than with a bit of blending in the cross over region.
How much blending? - you might ask. Well.... some make something work - others dont.
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Old 8th September 2020, 07:42 PM   #9
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by digitalthor View Post

You could do the opposite of the first order filters and try to make a very sharp filter. But you have to remember that a driver is a mechanical device, which take time to move and stop again - and the size plays a role too.
Would that be an issue in practice at the frequency a tweeter would take over?
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Old 9th September 2020, 08:05 PM   #10
garym999 is offline garym999  United Kingdom
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What prompted this question is that in a number DSPs I have seen now they all offer the standard analogue filter curves. I understand this when EQing and when starting and ending the filter curves but for crossovers I would have thought we could have steeper curves almost to the point of on/off
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