I would think more than twice about starting out with a USB microphone setup like Omnimic. While the software and system is great, the process of measuring a speaker for development is so much easier with an analogue mic and interface. There are a few very reasonably priced calibrated mics like the Sonarworks SoundID or Cross Spectrum labs sells different mics with their own calibration. The Dayton analogue mic is OK but some of the calibration files have been suspect. Add a cheap but good quality interface like the Focusrite Scarlett's or Behringer units and you get the phantom power, mic preamp and sound card all in one. With an interface REW can measure impedance and associated parameters with two resistors and a few parts, you might prefer a DATS but it is not necessary.
Warning in the Vituixcad measurement instructions
"Note! Single channel measurement systems such as USB microphones with latency variations by default are not recommended for speaker engineering due to timing and phase variations and normalizations. REW should not be used with single channel connection or mode for far field measurements because timing is normalized by the program. Single channel connection and mode is acceptable for near field measurements only"
If you plan to make speaker design your hobby, listen to the warning 🙂
Wow! Thank you for the detailed advice. Funny enough I actually already have an interface with phantom power kicking around somewhere. It's called the Steinberg UR44C. So, I am already halfway there! I will heed these warnings and hopefully my designs will be better for it 🙂
Indeed you are Steinberg makes good stuff too.
This is how to measure impedance and TS parameters with REW
https://www.roomeqwizard.com/help/help_en-GB/html/impedancemeasurement.html
As the opening post is explicitly about passive filters, my earlier remark about FIR filters was off topic, apologies for that.
System phase response is normally way down on the priority list of loudspeaker designers, because unless it is exceptionally bad, it is barely if at all audible.
Phase coherence between different drivers in the crossover region is a different matter. For example, if the drivers were 180 degrees out of phase on axis, their sound would cancel and you would get a deep notch in the on-axis magnitude response. It's not that bad with less than 180 degrees, but you still get some aberration on axis and in the radiation pattern (tilted main lobe).
System phase response is normally way down on the priority list of loudspeaker designers, because unless it is exceptionally bad, it is barely if at all audible.
Phase coherence between different drivers in the crossover region is a different matter. For example, if the drivers were 180 degrees out of phase on axis, their sound would cancel and you would get a deep notch in the on-axis magnitude response. It's not that bad with less than 180 degrees, but you still get some aberration on axis and in the radiation pattern (tilted main lobe).
Hi,
Buy a mic, be ready for a bit of frustration ( the time to learn how to interpret) and it'll be good.
You are a young guy! So refreshing to see young people interested in loudspeaker design in the 'engineer' approach to it! 👍
Phase and time alignement.
They are linked.
With passive filter (IIR) yes to your first question (but it can be mitigated/optimised with some 'global' filtering approach/strategy).
Rather than 'coherence' at xover fc i would think about what kind of compromises are going to be made (as there will be some issues involved) and why.
Group delay is one of this point where compromises are going to be made. But the power response or directivity of your complete system ( finished loudspeaker) might be compromised too.
I agree with other that if interested in it read or search about treshold of audibility for it ( hint: there is agreement of what happen in mid/high, about low freq...).
That said with FIR complementary filters ( xover duties) you have access to filters that don't induce phase 'anomaly' by themself. They also offer way steeper slope if you ever need it.
These one i use and with the gear i own there is no 'pre ringing' issue audible to me.
Once you start to use 'DRC' ( 'Room' Correction) then potentiality to hear 'pre ringing' rise imho, as they are more 'complex' profile and 'non complementary' anymore ( except at one and unique spot in space). That do not say it won't bring good thing over a wider area though, but as always it might induce compromise ( on pre ringing audibility in this case).
The use of steep passive filter could be of help in certain cases but... it doesn't comes free: you'll compromise on transient behavior. Trade off, tradeoff,...
'180 degrees out of phase' ( it's usually called a polarity inversion rather than '180* out of phase') over a region? Na, you can be out of phase over a given freq (reference) but unlikely over a 'region' as there is few loudspeaker i know of which can maintain 'flat' phase over large freq coverage ( especially at both end of spectrum where there is an defacto lowpass ( in the highs: physical limits of your tweeter) and highpass ( lows, your box).
Some odd order filter implementation will require one of the driver in oposite polarity: otherwise you'll have an amplitude notch at xover freq (a 'valley' in freq response). Not the best way to render an invisible transition ( if that is your goal).
I think it is misleading to mosts.
Don't take someone's words: it's so approach dependent.
Better try to find different design approach and study them imho. Then try to apply them on prototype design to gain knowledge and see by yourself if you are sensitive or not to the different approach.
Some food for thoughts:
Stereophile.com/interviews/163/index.html
Try looking for Rane's white paper titled "Linkwitz Riley A Primer.pdf" an " Bessel filter and it's relation to others.pdf"
Buy a mic, be ready for a bit of frustration ( the time to learn how to interpret) and it'll be good.
You are a young guy! So refreshing to see young people interested in loudspeaker design in the 'engineer' approach to it! 👍
Phase and time alignement.
They are linked.
With passive filter (IIR) yes to your first question (but it can be mitigated/optimised with some 'global' filtering approach/strategy).
Rather than 'coherence' at xover fc i would think about what kind of compromises are going to be made (as there will be some issues involved) and why.
Group delay is one of this point where compromises are going to be made. But the power response or directivity of your complete system ( finished loudspeaker) might be compromised too.
I agree with other that if interested in it read or search about treshold of audibility for it ( hint: there is agreement of what happen in mid/high, about low freq...).
That said with FIR complementary filters ( xover duties) you have access to filters that don't induce phase 'anomaly' by themself. They also offer way steeper slope if you ever need it.
These one i use and with the gear i own there is no 'pre ringing' issue audible to me.
Once you start to use 'DRC' ( 'Room' Correction) then potentiality to hear 'pre ringing' rise imho, as they are more 'complex' profile and 'non complementary' anymore ( except at one and unique spot in space). That do not say it won't bring good thing over a wider area though, but as always it might induce compromise ( on pre ringing audibility in this case).
The use of steep passive filter could be of help in certain cases but... it doesn't comes free: you'll compromise on transient behavior. Trade off, tradeoff,...
'180 degrees out of phase' ( it's usually called a polarity inversion rather than '180* out of phase') over a region? Na, you can be out of phase over a given freq (reference) but unlikely over a 'region' as there is few loudspeaker i know of which can maintain 'flat' phase over large freq coverage ( especially at both end of spectrum where there is an defacto lowpass ( in the highs: physical limits of your tweeter) and highpass ( lows, your box).
Some odd order filter implementation will require one of the driver in oposite polarity: otherwise you'll have an amplitude notch at xover freq (a 'valley' in freq response). Not the best way to render an invisible transition ( if that is your goal).
I think it is misleading to mosts.
Don't take someone's words: it's so approach dependent.
Better try to find different design approach and study them imho. Then try to apply them on prototype design to gain knowledge and see by yourself if you are sensitive or not to the different approach.
Some food for thoughts:
Stereophile.com/interviews/163/index.html
Try looking for Rane's white paper titled "Linkwitz Riley A Primer.pdf" an " Bessel filter and it's relation to others.pdf"
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Learning to drive Vituix from the beginning is a good way to spend your time. If you really want to understand phase and time relationships in crossovers then you need to be able to see both on and off axis angles and how the changes affect the directivity, power and early reflection responses.
Start reading here and keep going in the thread, there is a great deal of information, examples and advice. Bookmark it as it won't all sink in at first.
https://www.diyaudio.com/community/threads/vituixcad.307910/post-6531747
At the risk of getting piled on, here's my $0.02...
I'm not sure if you've done a DIY speaker build yet or not, but my best advice would be to first solidify what you enjoy- what are you after? "I just want speakers that sound awesome", well that's fine but you don't know what you prefer until you actually hear something you love or hate. Because regardless of what everyone says on forums, speakers that measure very similarly can sound vastly different, and a flat measurement is definitely relative. Some people like the highs slightly rolled off, some like a mild uptick from 8khz up, some prefer a mild dip in the upper midrange/lower treble... and none of them are wrong (some people like spicy food, some don't).
I've been avidly building speakers for over 10 years now, I've designed more speakers than I can remember and I'm still learning. Don't worry at all about phase, spend time learning and understanding the basic concept of 1st, 2nd, 3rd... order acoustic (and electrical) filters, and the general reasons for why someone chooses a 1st, 2nd, 4th, whatever. And even this can be tough, because not everyone is correct, and in my opinion this is the most difficult part of actually learning this. And the tough part is, you don't know for sure until you try it yourself. Once you have a good, first hand grasp of this, then try to figure out if (or where) phase matters.
Another suggestion is to go to a DIY event and listen to what people are actually building and talk with some of them, doing this can be a real eye opener. The next one I'm aware of is in Grand Rapids, Michigan, put on by Meniscus Audio on September 24. If you think you might be interested, give Meniscus a call for more info.
Remember, it's just a speaker, and we're only doing this to have fun. So go make some mistakes but have fun doing it. The only downside is... it gets expensive if you end up enjoying it lol.
I'm not sure if you've done a DIY speaker build yet or not, but my best advice would be to first solidify what you enjoy- what are you after? "I just want speakers that sound awesome", well that's fine but you don't know what you prefer until you actually hear something you love or hate. Because regardless of what everyone says on forums, speakers that measure very similarly can sound vastly different, and a flat measurement is definitely relative. Some people like the highs slightly rolled off, some like a mild uptick from 8khz up, some prefer a mild dip in the upper midrange/lower treble... and none of them are wrong (some people like spicy food, some don't).
I've been avidly building speakers for over 10 years now, I've designed more speakers than I can remember and I'm still learning. Don't worry at all about phase, spend time learning and understanding the basic concept of 1st, 2nd, 3rd... order acoustic (and electrical) filters, and the general reasons for why someone chooses a 1st, 2nd, 4th, whatever. And even this can be tough, because not everyone is correct, and in my opinion this is the most difficult part of actually learning this. And the tough part is, you don't know for sure until you try it yourself. Once you have a good, first hand grasp of this, then try to figure out if (or where) phase matters.
Another suggestion is to go to a DIY event and listen to what people are actually building and talk with some of them, doing this can be a real eye opener. The next one I'm aware of is in Grand Rapids, Michigan, put on by Meniscus Audio on September 24. If you think you might be interested, give Meniscus a call for more info.
Remember, it's just a speaker, and we're only doing this to have fun. So go make some mistakes but have fun doing it. The only downside is... it gets expensive if you end up enjoying it lol.