Why is the Active Cardioid unpopular in DIY projects?

[Arindal]

Between 100-300 I think the advantage is placement near a wall, particularly for nearfield type monitors.

A cardioid is surely a foolproof solution to this placement problem, yet a rather expensive one. Particularly in a nearfield environment without room modes dominating, the frequency band 100-300Hz is rather easy to deal with using a DSP correction.

Aside from dipoles I'm not aware of any compact solutions for directivity control from 100-200hz.

A line source would do this job, but could hardly be called ´compact´, if effective all the way down to 100Hz. The question is why you need such directivity control? This is the frequency band in which directivity errors are least likely to become audible, hence easily equalizable, if there is no sudden step in directivity towards a neighboring band.

 

[phr33ksho]

A cardioid is surely an foolproof solution to this placement problem, yet a rather expensive one. Particularly in a nearfield environment without room modes dominating, the frequency band 100-300Hz is rather easy to deal with using a DSP correction.



A line source would do this job, but could hardly be called ´compact´, if effective all the way down to 100Hz. The question is why you need such directivity control? This is the frequency band in which directivity errors are least likely to become audible, hence easily equalizable, if there is no sudden step in directivity towards a neighboring band.

The theory behind it is that the more constant the directivity index, the more reflective of the original sound the reverberant field will be - yes you can eq to get a flat frequency response, but you cannot equalize the ratio of direct to reverberant sound - that is the reason you'd want directivity control. I've found this theory to be borne out in my experience - when a speaker has controlled directivity the drivers tend to sound better integrated, and more natural. Granted the bulk of my listening to a controlled directivity source is on dipoles, so some of the benefits I chalk up to the directivity in that frequency range may be the result of the lack of cabinet resonances which tend to be most noticeable in that range, but I think the dispersion accounts for a lot of what I like about the sound of my current speakers (lx 521.4 w a different woofer section)

 

[Arindal]

the more reflective of the original sound the reverberant field will be - yes you can eq to get a flat frequency response, but you cannot equalize the ratio of direct to reverberant sound

I am aware of that, being a strong supporter of any constant directivity concept. I have extensively listened to a large number of different loudspeakers, applied various room correction methods and found the theory behind CD to be applicable in almost all cases. Very uneven directivity particularly between 500 and 8,000Hz leads to audible problems which cannot be EQ´ed to satisfaction.

We should admit, though, that below 300Hz human perception does not really differentiate between direct and reflected sound. Due to long duration of a period compared to relatively short delay of the reflections in a typical room, these two seemingly blend with each other. If you make sure that no other side-effects of dominating energy in the room, such as distortion, very long sustain of resonances, rattling or alike, become audible, the 100-300Hz band should be correctable via EQ in most of cases.

I think the dispersion accounts for a lot of what I like about the sound of my current speakers (lx 521.4 w a different woofer section)

Had the chance to listen to the most current iteration of Siegfried Linkwitz´ speakers and can confirm that - excellent midrange, bass timing and presence, a very fine example of constant directivity. I do not agree with the theory regarding treble dipole and the use of two identical tweeters.

 

[phr33ksho]

I am aware of that, being a strong supporter of any constant directivity concept. I have extensively listened to a large number of different loudspeakers, applied various room correction methods and found the theory behind CD to be applicable in almost all cases. Very uneven directivity particularly between 500 and 8,000Hz leads to audible problems which cannot be EQ´ed to satisfaction.

We should admit, though, that below 300Hz human perception does not really differentiate between direct and reflected sound. Due to long duration of a period compared to relatively short delay of the reflections in a typical room, these two seemingly blend with each other. If you make sure that no other side-effects of dominating energy in the room, such as distortion, very long sustain of resonances, rattling or alike, become audible, the 100-300Hz band should be correctable via EQ in most of cases.



Had the chance to listen to the most current iteration of Siegfried Linkwitz´ speakers and can confirm that - excellent midrange, bass timing and presence, a very fine example of constant directivity. I do not agree with the theory regarding treble dipole and the use of two identical tweeters.

I think at the margins things still have an impact - there is no exact frequency where people stop differentiating direct and reflected sound its a smooth transition and I would put 300hz as the beginning of the transition not the end. Like everything in life, you gotta make value judgements in audio - I suppose for me the controlled directivity at lower frequencies may not be as important as the lack of cabinet resonances and internal reflected sound, but it comes for free with an open baffle.

I can't claim to have done enough critical listening to say for certain whether the directivity at lower (150-300hz) is audible, but I guess the best sounding speakers I've heard have had that characteristic so is easy to ascribe part of the sound to that quality.