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Multi-Way Conventional loudspeakers with crossovers

Freq measurements and Hypex Filter Design adjustments
Freq measurements and Hypex Filter Design adjustments
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Old 29th July 2019, 06:55 AM   #101
Steve2111 is offline Steve2111
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Default Freq measurements and Hypex Filter Design adjustments

My question was whether a Passive XO can do everything a DSP can? I didn't think that a passive could do what a DSP can. I attach a photo of the passive XO that was designed for me. You may not be able to appreciate how large it is. At the moment (with one stereo amp) it still sounds better than my DSP with 6 amps. I do not have the circuit diagram and the person who designed it for me is now ill, so I don't want to bother him.

I still hope that my DSP solution will sound better when configured correctly.
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Old 29th July 2019, 09:06 AM   #102
YSDR is offline YSDR  Europe
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The short answer is no. A passive xo cannot do everything what a DSP can, and the passive network can easily become too complicated if we try to copy the response of a DSP xo.
The biggest drawbacks of the passive xo is that the endresult depends on the driver's impedance and the xo network sits between the amp and the drivers.
The high impedance created by the xo network flushes the driver's Qes to the toilet and that's audible i think.

Last edited by YSDR; 29th July 2019 at 09:10 AM.
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Old 29th July 2019, 09:57 PM   #103
PLB is offline PLB  United Kingdom
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Hi Steve,

Re. your post #99. The method I personally use to design active Xovers employs software having optimisers to accurately generate filters to match target responses and is definitely not suitable for DIY use.
So for this reason I would encourage you to carry on with the method that DeniBeni is showing you, especially since he is the one (as you pointed out) that first suggested you use a target response.
The target response in ARTA only generates a target response curve. It is simply a visual aid that provides a means to check if your acoustic response (via your Xover) matches the response of the target curve.
In order to generate a target curve for an LR4 LPF at 500Hz with its passband set to a level of 135dB, all you have to do is enter the values I show in the attachment of my last post.
One thing I forgot to mention in my last post is that with near-field measurements there is an upper frequency limit to its accuracy that depends on the drivers diameter. For the Focal Audiom 15 WX it will be at approximately 332Hz. You can check this out via this link: HiFi Loudspeaker Design . Hope this helps.

Peter
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Old 30th July 2019, 05:30 AM   #104
YSDR is offline YSDR  Europe
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Yes, target response overlay comes in handy as PLB suggested, especially with the tweeter, where in your case you don't want to measure without crossover filter.
Just measure the tweeter only (with xo filter) and compare the response to the 2kHz LR4 target overlay or whatever xo you want to use and correct the response according to that overlay. It's slightly harder to do this way than flattening first, because the response has to be aligned to a curve and thus harder to visualize, but can be done with a little practice.
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Old 30th July 2019, 01:38 PM   #105
CharlieLaub is offline CharlieLaub  United States
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The "target response curve" approach will work will if:
  • Your acoustic centers are well aligned and so is the phase between highpass and lowpass filters, or
  • You happen to get lucky with phase alignment
In general, even if the SPL follows a target curve of a known filter response (e.g. LR4, 2nd order Butterworth, etc), the phase response at some listening position can be completely different. This is because the SPL and phase are unrelated in the far field (the far-field response is not minimum phase). The phase is strongly influenced by the pathlength from acoustic center (source) to the listening position, but also varies with the driver's inherent frequency response and the added phase lag/rotation of any filter elements added to the input to the driver.

There are some crude approaches to improve the phase alignment, like reversing the leads on one or more drivers or adding another filter to increase the phase rotation, but these are mostly shots in the dark unless there is accurate modeling of the output from the drivers in the loudspeaker system that carefully accounts for all the phase relationships.
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Old 30th July 2019, 02:02 PM   #106
YSDR is offline YSDR  Europe
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Of course, the phase response of more drivers cannot be aligned to all point in space.
So all we can do is to align the phase in the gated measurement around the main listening axis.

If all the drivers follow their LR4 response you only need to adjust the delay of one driver to the next in row around the choosed axis and you get a good phase match for that two driver.
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Old 30th July 2019, 02:25 PM   #107
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by denibeni
The high impedance created by the xo network flushes the driver's Qes to the toilet and that's audible i think.
I'd like to see you prove this, and certain other assertions..
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Old 30th July 2019, 02:38 PM   #108
YSDR is offline YSDR  Europe
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Quote:
Originally Posted by AllenB View Post
It's a shame to see such passionate conjecture.

Which may explain why some can do it while some ask for assistance.More conjecture, please show me the numbers.
Since when is this a thing?
Ohh AllenB, a loyal follower of the passive crossover cult. Are you serious?

For good reason I wrote that the short answer is "cannot". Yes the long answer would be that you can do all the things passively, but i don't think it's worth the effort.
For example, please make us an LR4 curve from an LR2 in a few clicks and then set the timings of the drives with microsecond accuracy to each other in a minute and in a way that it only takes time. Sure, you can approach it passively, but it won't work the same way, i'm sorry.
By the way, i've built quite a few passive crossovers, and i liked it, so i'm aware of it.

But anyway, I don't think this is the place where we have to deal with such disputes yet. So please give us some constructive tips for this active DSP project, we are curious.

Last edited by YSDR; 30th July 2019 at 02:47 PM.
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Old 30th July 2019, 02:43 PM   #109
AllenB is offline AllenB  Australia
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I've been doing active crossovers since last century
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Old 30th July 2019, 02:52 PM   #110
YSDR is offline YSDR  Europe
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Quote:
Originally Posted by AllenB View Post
I'd like to see you prove this, and certain other assertions..
If you think that a high impedance network (like a passive crossover) between the amp and the drivers is not spoil the driver's Qes, then i don't know what to say.
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