We are bashing without mercy DACs filters for filtering frequencies over 44khz -6db/octave with a little inductor. However we don't have any issue with inserting a big inductor 1khz filter -12db+/octave and a capacitor which are reactive/capacitive (on top of the driver's own problems) without any objection...
this is just food for though, I am puzzled by the 'tolerance' toward cross overs, just add enough and you will be fine, sound will be fine.
this is just food for though, I am puzzled by the 'tolerance' toward cross overs, just add enough and you will be fine, sound will be fine.
The CTC craze works well in practice not necessarily because of better lobing but because it compels one to use a smaller midrange and thereby getting better dispersion.
Who are we? Audioholic numb nuts with anal obsessions
Yes, some audiophiles use their cats as an assistant.
In particular : GoodSoundClub - Romy the Cat's Audio Site
CTC
Here is a simulation of the response of a (theoretical, ideal) 2-way speaker with 1st order crossover at 2kHz, using a 1" tweeter, 7" midwoofer with different CTC spacings and at 0degree vertical offset (from tweeter), -20 degree, and +20 degree. The simulation was done in XSim (beta version), the plots are show in Omnimic, just to use its multicurve display function.
The 4"CTC (light green curve) is about as close as is done normally with that kind of 1"/7" driver set. There is a mitigating factor: 1st order has the highest driver overlap, speakers with higher order crossovers won't be perturbed over as much of a frequency range (though they might have higher amplitude swings over the narrower crossover ranges).
The effects will get worse at more than the +/-20 degree angle offsets shown, of course. 20 degrees at 5ft away is 18.5" from the tweeter axis. That might seem like it wouldn't matter, but try playing a speaker for a minute while holding an album cover or large book between yourself and the speaker and notice how VERY little the volume level really drops at your ears! Speaker wavefronts and their responses are heard to some degree no matter what directions they left the speaker at, they just get to you at different times, except in anechoic chambers. There are far fewer directions in a room that have nice direct responses like the top graph than that have curves like the other two, or worse.
That's why there's all the interest in coaxials, full range, or synergy speakers.
Here is a simulation of the response of a (theoretical, ideal) 2-way speaker with 1st order crossover at 2kHz, using a 1" tweeter, 7" midwoofer with different CTC spacings and at 0degree vertical offset (from tweeter), -20 degree, and +20 degree. The simulation was done in XSim (beta version), the plots are show in Omnimic, just to use its multicurve display function.
The 4"CTC (light green curve) is about as close as is done normally with that kind of 1"/7" driver set. There is a mitigating factor: 1st order has the highest driver overlap, speakers with higher order crossovers won't be perturbed over as much of a frequency range (though they might have higher amplitude swings over the narrower crossover ranges).
The effects will get worse at more than the +/-20 degree angle offsets shown, of course. 20 degrees at 5ft away is 18.5" from the tweeter axis. That might seem like it wouldn't matter, but try playing a speaker for a minute while holding an album cover or large book between yourself and the speaker and notice how VERY little the volume level really drops at your ears! Speaker wavefronts and their responses are heard to some degree no matter what directions they left the speaker at, they just get to you at different times, except in anechoic chambers. There are far fewer directions in a room that have nice direct responses like the top graph than that have curves like the other two, or worse.
That's why there's all the interest in coaxials, full range, or synergy speakers.
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A 7" woofer (5.6" effective diameter) at 20 deg offset, per the rigid piston model. Not too far down at 2kHz yet (scale is 2dB/)
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Actually you'd be surprised. As stated this is only with a 1st order crossover so we're getting significant output above 2kHz too. This is all irrelevant though because you've completely missed the point.
The C2C spacing is important for the vertical off axis response. What's being shown is the inteference of the tweeter and woofer as you move up and down from the proposed listening axis. This changes the path differences between the two drivers and you start getting destructive interference at relatively low off axis angles.
The problem is exacerbated here by the 1st order filter, things look a lot better if you use the typical 4th order acoustic filter, as is usually dictated by 1"+7" designs.
Still it is a problem. It's another compromise. Ideally you want a coaxial. Slightly less than this you want a small format midrange driver (3") crossed low to a capable, small format, neo tweeter mounted chassis to chassis. You really do need to cross this below 2k as well.
Very few non-coaxial speakers accomplish this and everything else is a compromise around the vertical off axis. Is it a disaster? It's nowhere near as high on the list as other compromises but it depends on how you listen to your music. If you are always sat with your ears at the perfect listening height then it's not a huge issue. All that happens is the tonal balance changes slightly as there's less energy thrown into the room at certain frequencies (the nulls in the vertical off axis). If you listen at different distances and at different heights, ie you stand, walk around etc, then it can have a huge impact. First of all the frequency response at your ears will change dramatically as you stand and move around and then there's the power response tonal balance changes, which of course, pale in comparison to the interference pattern.
Note here that we are not and have not mentioned the drivers natural directivity/off axis response yet. This is purely the result of the drivers interfering with one another due to the different path differences. Of course the drivers own off axis response comes into this too, but it's a different kettle of fish.
Usually the drivers natural off axis response and crossover frequency that governs the horizontal off axis response of the final loudspeaker. Horizontally the path difference, between the two drivers, remains identical regardless of angle, so you're always properly in phase (providing the crossover is decent).
The C2C distance and crossover frequency are what determine the vertical off axis response. Of course the drivers off axis response comes into this but it tends to be a minor contributing factor, at least in designs that don't try and give you a huge vertical window. In most typical designs the vertical off axis response collapses at very low angles, usually you only need to look out to 25 degrees to see things fall to pieces. By 25 degrees most drivers off axis response is still pretty great, unless you've got an atypical design with huge drivers and comparatively high xover frequencies.
@5th element
Thank you very much for your elaboration on this topic. My (possibly mistaken) conception so far was that lobing is just a race to the shortest CTC, but it is not a pursuit without end - once your mid's off-axis takes over as the bottleneck you are off the hook.
For example, it takes only inches for the off-axis of a nearfield monitor to fall off the cliff (this is a virtue for its intended application). And it is not because a nearfield is designed to lobe, it is because it is easy for a woofer to lose response off-axis (when playing high, of course). The headache is reversed and is now how to limit tweeter dispersion.
I am more used to the quasi-LR4 acoustic and I am still not grasping how a 1st order is different because at exactly the crossover frequency the lobing problem is the same regardless of crossover order (except for phase changes at the crossover point and any associated power response changes). Given my total lack of experience with 1st order designs I guess it might be true in that case that lobing dominates vertical off-axis. But woofer off-axis still dominates the vertical off-axis of a quasi-LR4 1+7 - we are clearly not only having a problem near the crossover point, where the higher-order has significantly narrowed.
For this reason, I am a disbeliever of claims that coaxials have it all. There is still a dispersion gap when the mids cross to the tweeter and that must be audible off-axis. Coaxials only solve lobing issues but did nothing to improve the sudden transition from narrow woofer dispersion to wide tweeter dispersion. If anything coaxials tend to be crossed higher and thereby only worsening this dispersion gap. As with all engineering coaxials are but another set of compromises.
Thank you very much for your elaboration on this topic. My (possibly mistaken) conception so far was that lobing is just a race to the shortest CTC, but it is not a pursuit without end - once your mid's off-axis takes over as the bottleneck you are off the hook.
For example, it takes only inches for the off-axis of a nearfield monitor to fall off the cliff (this is a virtue for its intended application). And it is not because a nearfield is designed to lobe, it is because it is easy for a woofer to lose response off-axis (when playing high, of course). The headache is reversed and is now how to limit tweeter dispersion.
I am more used to the quasi-LR4 acoustic and I am still not grasping how a 1st order is different because at exactly the crossover frequency the lobing problem is the same regardless of crossover order (except for phase changes at the crossover point and any associated power response changes). Given my total lack of experience with 1st order designs I guess it might be true in that case that lobing dominates vertical off-axis. But woofer off-axis still dominates the vertical off-axis of a quasi-LR4 1+7 - we are clearly not only having a problem near the crossover point, where the higher-order has significantly narrowed.
For this reason, I am a disbeliever of claims that coaxials have it all. There is still a dispersion gap when the mids cross to the tweeter and that must be audible off-axis. Coaxials only solve lobing issues but did nothing to improve the sudden transition from narrow woofer dispersion to wide tweeter dispersion. If anything coaxials tend to be crossed higher and thereby only worsening this dispersion gap. As with all engineering coaxials are but another set of compromises.
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