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Multi-Way Conventional loudspeakers with crossovers

Well I suppose the shallow vs. steep argument will just go on and on
Well I suppose the shallow vs. steep argument will just go on and on
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Old 27th October 2017, 02:29 AM   #11
5th element is offline 5th element  United Kingdom
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To be fair there have been audio files posted where you can compare the difference between 2nd and 4th order filters.

These are files where an audio sample has been taken, digitally filtered and therefore split into two separate streams. One of the streams is a low passed version, the other a high passed version. The two streams are then recombined back into a single file.

Basically with the above the amplitude of the input and output remains exactly the same, only the phase shift, associated with the different filters, is left present.

Various filters orders were provided. I couldn't hear any difference between the different slopes. Nada, zilch, nothing. If there was any difference it was so minuscule as to be irrelevant.

This also ties in well with my own experience. Using suitable drivers I have directly compared 2nd order vs 4th order Linkwitz Riley xovers. This was done via a DSP where both sets of filters were stored in memory and could be swapped between at the touch of a button. Switching between the two took such little time that you couln't even hear an interruption in the music except for a small 'click' or 'pop'.

Could I hear any difference? Short answer yes. But only because the vertical off axis, from one design to the other, affected the power response ever so slightly and this resulted in a tiny difference in tonal balance. You really had to listen hard to be able to hear it and without the ability to quickly swap between one and another it would have been impossible.

My conclusion from all of this is basically along the lines of - use whatever filters are necessary to get the job done. Striving for certain filter orders, because they somehow contain audio magic, when any kind of compromise is going to introduced by lowering the filter order, is just silly.
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Old 27th October 2017, 02:33 AM   #12
planet10 is offline planet10  Canada
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Well I suppose the shallow vs. steep argument will just go on and on
5th element… that process leaves out a lot of context.

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Old 27th October 2017, 03:46 AM   #13
system7 is offline system7  United Kingdom
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Well, I suppose we'd like to know the exact drivers, but an interesting test by 5th element.

I built 3kHz all-pass op-amp filters years back. We could never hear the group delay overall.

Click the image to open in full size.

The current big wheeze is time-alignment: 18W-8434G00

It seems to make sense to recess the top end to even out the group delay as much as is possible. And this must help phase, because as a lot of people know, ideal LR2 (acoustical 12dB/octave slopes) is a negative polarity solution, and LR4 (acoustical 24dB/octave slopes) a positive polarity one when time aligned.

Quote:
Originally Posted by Troels Gravesen
Second order, flat baffle with notch and positive polarity near LR2:
Setting up V1 crossover was easy and overall tonal balance was good, but the transition from upper mid to treble appeared rather fizzy and blurred. Something just wasn't right despite the ability to play all kinds of music without any distress to the ear.

Same but third order tweeter, which phase-aligns better with asymettric slopes:
The V2 crossover solved this problem and kind of made the sound well known from many other speakers I've made, but not up to the level of stepped baffle/LR2 speakers I've made ever since the launch of the first Jenzen speaker - or the ScanSpeak Illuminator with its all-pass filter to the tweeter. The quality of the W18 driver strongly suggested there were more goodies in store.

Same idea, but negative polarity on stepped baffle and second order tweeter:
V3 crossover: Making the stepped baffle and implementing a true LR2 filter made a world of a difference. Suddenly music started flowing and sense of depth and perspective improved vastly. I never heard the difference between a flat baffle/2nd-3rd order crossover and a stepped baffle/true LR2 filter so clearly. It's night and day. It also made me think I have to do the Ellam XT once more with an easy stepped baffle because people continue building the Ellam XT speaker rather than the much better Ellam FLEX with its more complex front panel layout. There are more to be gained from these Ellam XT. And I would love to do the 9800 tweeter again in such set-up... well, well, back to the Discovery here.

4th. order electrical:
V4 crossover (stepped baffle): This has the well known 4th order characteristics. Even power response and a balanced presentation with a noticeable presence character. Good for monitoring! I know some people like this a lot but to my ears it sounds kind of flat and without the sense of depth and 3-dimensionality of the LR2 filter. Matter of taste in the end.
It's all good fun, IMO. To me, the cleanest, loudest sound is always higher order filters. There is something spooky about a speaker with no colouration or distortion and narrow dispersion, IMO. And I have heard a few, even expensive Koss electrostatic headphones. They actually sound, er, spooky! I can't describe it. But I think it's the lack of room acoustic or spatial context. Sort of hollowness. It's slightly uncomfortable.
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Old 27th October 2017, 03:57 AM   #14
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Old 27th October 2017, 04:39 PM   #15
gedlee is offline gedlee  United States
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Quote:
Originally Posted by 5th element View Post
My conclusion from all of this is basically along the lines of - use whatever filters are necessary to get the job done. Striving for certain filter orders, because they somehow contain audio magic, when any kind of compromise is going to introduced by lowering the filter order, is just silly.
I completely agree. I use a steep filter on the woofer and a shallow one on the tweeter, but the bottom line is whatever works. This idea of using "name brand" filters is absurd - especially in the electronics, because the acoustics will dominate the end result and there nothing is simple.
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Old 27th October 2017, 06:18 PM   #16
andy2 is offline andy2  United States
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Out of curiosity, is our vocal cord + diaphragm combo combined to be 1st, 2nd, 3rd, or 4th? I mean natural our voice has a high frequency rolled off so the freq. response would be like a 5.5 in. woofer unless you're a bird then it would be more like a tweeter. This would lead to another point I would like to make, but not now.
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Old 27th October 2017, 07:23 PM   #17
bbutterfield is offline bbutterfield  United States
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Quote:
Originally Posted by 5th element View Post
...

Various filters orders were provided. I couldn't hear any difference between the different slopes. Nada, zilch, nothing. If there was any difference it was so minuscule as to be irrelevant.

This also ties in well with my own experience. Using suitable drivers I have directly compared 2nd order vs 4th order Linkwitz Riley xovers. This was done via a DSP where both sets of filters were stored in memory and could be swapped between at the touch of a button. Switching between the two took such little time that you couln't even hear an interruption in the music except for a small 'click' or 'pop'.

Could I hear any difference? Short answer yes. But only because the vertical off axis...

My conclusion from all of this is basically along the lines of - use whatever filters are necessary to get the job done. Striving for certain filter orders, because they somehow contain audio magic, when any kind of compromise is going to introduced by lowering the filter order, is just silly.
I pretty much agree with this. In the low Khz range, phase just doesn't matter much, if at all. In the several hundred hz range, it matters a little. I did ABX testing with wav files with and without phase distortions like those from a crossover, and couldn't tell them apart if the crossover emulated was 2 Khz. At 200 Hz I could, but didn't really have a preference.

I know how to use DSP to fix phase distortions on axis (even did that as a senior design project) but I don't bother.

YMMV.
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Old 27th October 2017, 07:33 PM   #18
andy2 is offline andy2  United States
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I was wondering if DSP is a valid way to test, since your signal is already has a lot of phase shift to begin with due to the ADC stage and DAC stage(if that is what you are using). Also, given most DSP do not have good ADC and DAC, the tests you're referring to is a bit of suspect. I used to have an old Kenwood receiver and I couldn't tell much from anything since the signal was so corrupted by the internal digital processing.
People who designed audio DAC had to deal with phase shift way back then. In the early 80's, DAC didn't have any fancy upsampling so they had to use very steep filter for the reconstruction stage after the DAC so early CD player sounded harsh because of the excessive phase shift especially in the higher frequency caused by steep slope filter. Now with better upsampling, they can use gentle slope on their filter which fixes a lot of the issues back then. Of course there are other factors in making good DAC but it was one of the main one. One of the reason behind SACD was to use very high sampling rate (MHz rate) so to shift out of band harmonic way out of the audible range which helps make the reconstruction filter much easier.
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Old 27th October 2017, 08:05 PM   #19
bwaslo is offline bwaslo  United States
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Well I suppose the shallow vs. steep argument will just go on and on
Actually, modern ADC and DACs have virtually no nonlinear phase shift in the audio band, as the filtering is mostly done with internal DSP processing. Easily shown with a square wave generator and an analog oscilloscope.

Audio band phase linearity is almost trivial to correct even with speakers (at least for one point in space) these days, using FIR equalization. But the importance of having linear phase appears to be mostly for the benefit of marketing magazines and speakers rather than higher-fi.
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Old 27th October 2017, 08:45 PM   #20
uzernaam is offline uzernaam  United States
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It has been argued all over the internet that phase differences are inaudible, even by experts.

My ears tell me a different story entirely. I first noticed a large improvement in sound quality back when I was installing car stereos in the 90s. Back then there were a few systems you could install which included a digital signal processor box which among other things could function as a digital crossover. Some of these as I recall had linear phase FIR filters.

The first of these systems I installed resulted in a night and day improvement in sound quality. I wanted one, but they were too expensive for my personal budget so I continued to tinker with inexpensive solutions.

I started building 2-way speakers as a hobby for myself, and began settling on designs which could get away with using the simplest crossovers that could still be properly called a crossover - the 1st order Butterworth, with just a cap on the tweeter and coil on the woofer. Driver selection is important because you're not getting as much attenuation as you would with higher order filters. Tweeters especially needed to be able to handle some energy at one or two octaves below the crossover point without being destroyed, and it also helped to have a low resonance frequency.

Many of these 2-ways had dome tweeters by Morel and Dynaudio, but my favorite was the Bohlender Graebener Neo 8, since it could handle a bit of lower frequency energy and a somewhat lower crossover point.

The results were so good that I could say they compared to some high end commercial speakers. The smoother phase across the audio band really did seem to have the effect of getting the speaker "out of the way" and let the music come out more true to form. These speakers are not capable of high power handling or volume compared to many other designs, but I never listened to music that loud anyway, and the smoothness and finesse of a properly implemented 1st-order system had me sold on the idea that phase response was important. Keep in mind my conclusions are after literally years and years of first installing car and then high-end home theater systems. I have a crate full of caps and coils from crossover experimentation all the way to 36 dB/oct and everything in-between.

The "holy grail" of crossovers to me is one that essentially "does no harm" to the signal, not just amplitude, but also phase. An "ideal" crossover, if you will, but that solution can only be done via technology.

Fast forward today and I am experimenting with a miniDSP 4x10, which has the ability to tailor the audio reaching your amps and speakers with surgical precision. Results have been fantastic. Never have I heard such realism from a pair of speakers except perhaps some of the exotic ultra-high end systems being demonstrated at boutique shops, which I could never afford anyway.

Last edited by uzernaam; 27th October 2017 at 08:54 PM.
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