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.

 

[carlosatl]

So can we just connect 2 subs to our current speakers to make cardiod response? Keep it really simple ?

 

[somebodyelse]

So can we just connect 2 subs to our current speakers to make cardiod response? Keep it really simple ?

Unlikely. How do you think that would work?

 

[carlosatl]

Unlikely. How do you think that would work?

It was a question if it were possible, guess not.

 

[NTK]

It was a question if it were possible, guess not.

According to these guys you can form a cardioid sub array with 2 stacked subs. See section 4.2 of this paper.

SIMULATION AND APPLICATION OF BEAM-SHAPED SUBWOOFER ARRAYS | Institute of Acoustics

www.ioa.org.uk

 

[voodooless]

According to these guys you can form a cardioid sub array with 2 stacked subs. See section 4.2 of this paper.

SIMULATION AND APPLICATION OF BEAM-SHAPED SUBWOOFER ARRAYS | Institute of Acoustics

www.ioa.org.uk

This is a really common setup in pro-audio, like large festivals, especially in crowded areas. It’s used to steer the bass towards the audience.

 

[somebodyelse]

According to these guys you can form a cardioid sub array with 2 stacked subs. See section 4.2 of this paper.

SIMULATION AND APPLICATION OF BEAM-SHAPED SUBWOOFER ARRAYS | Institute of Acoustics

www.ioa.org.uk

That's not the arrangement I understood the question to be about - it seemed to be sub plus bookshelf/floorstander (x2 for stereo) where there's only a limited frequency range where both could operate at the same time to shape the dispersion.

On a related note did you ever model the interaction between cardioid subs and room with different placement options? I only remember seeing monopole and dipole. Some have suggested that in the acoustically small space of a domestic room the cardioid wouldn't be much different to the monopole, and 2 monopoles would be a more effective way to use the drivers, amps and DSP than 1 cardioid.

 

[NTK]

On a related note did you ever model the interaction between cardioid subs and room with different placement options? I only remember seeing monopole and dipole. Some have suggested that in the acoustically small space of a domestic room the cardioid wouldn't be much different to the monopole, and 2 monopoles would be a more effective way to use the drivers, amps and DSP than 1 cardioid.

If I have done any, it would be too long ago for me to remember I think in simulations cardioids may just show they couple to the room differently from monopoles, and their perceptual effects may be difficult to discern from the simulation results. Dr Toole thinks that monopole subs should be the norm (see post).

I think pyroomacoustics may be useful here for the room simulations (for in-room frequency response). It is free and the cost of entry is a working knowledge of Python. A cardioid sub can be simulated using two monopole subs. I think it would be a fun little year-end project for me. Give me a few days so I can reaquaint myself with it. If I am successful I can post a quick tutorial, and provide some example Jupyter notebooks so those interested don't have to start from scratch

 

[Ktacos]

New-ish tech to most DIY'rs, most people running active are already doing their own thing, not really any comprehensive plans for diy cardioid speakers afaik.

I recall someone sharing their cadioid speaker here, was a kii seven clone basically and they wouldn't share some of the info people wanted so there's that problem. I think someone asked for cabinet plans and they said it was too complicated to make without cnc, which was hilarious because I had the same box sitting on the floor in front of me that I made with a track saw lol. People are silly sometimes.