Constant directivity vs. smoothly increasing directivity

[Senior NEET Engineer]

For example you are comparing two speakers: Genelec 8351B+W371A and Genelec 8351B. Both are equalized to have similar in-room frequency response below 1khz, including the bass extension. Assuming distortion and output capability is not an issue, what would be the main differences in sound?

 

[thewas]

Higher directivity in the bass (so the first option) gives me personally the feeling of a less muddier bass, but I unfortunately don't have loudspeakers where I can switch directly directivity like that.

 

[Juhazi]

I think that we must concider sound radiation in 3D space, but typical directivity plots show only frontal hemisphere (up to 90deg). Horizontal directivity is much more important than vertical, but extreme cases of vertical will sound diffferent no doubt.

High directivity down to low mid - upper bass easily leads to more or less constant directivity index and it can be seen typically with dipoles and modern cardioid designs. Dipoles have strong backside radition which has more variation in directivity and perhaps that is why it is typically hidden info. Cardioids are getting more popularity and that design has least amount of variation from wall reflections. My guess is that it will definitely sound different to "normal" small box speakers with rather narrow baffles - and better!

More about this
https://kimmosaunisto.net/CardSub/CARDSUB.html
https://www.princeton.edu/3D3A/Directivity.html
https://www.stereophile.com/content/going-dutch-dutch-conversation-martijn-mensink
https://assets.ctfassets.net/4zjnzn...f44ec7867f674a109a/W371A_operating_manual.pdf

 

[aarons915]

Smoothly increasing directivity seems to be subjectively preferred in most listening tests I've seen and my own personal tests. The most famous one of course is the Salon 2 vs JBL M2.

 

[phoenixdogfan]

I think a more interesting question is whether there's any way a DSP program can change a speaker's directivity? And, if so, is anything like that on the market now?

 

[wwenze]

I think a more interesting question is whether there's any way a DSP program can change a speaker's directivity? And, if so, is anything like that on the market now?

Without additional drivers, not possible. Cardioid speakers use multiple drivers too.

If it were possible, antenna design would be so simple, we could create directional antennas using just a single stick. But the fact that it doesn't exist despite millions spent into DSP-ing RF signals makes me not hold my breath.

 

[somebodyelse]

I think a more interesting question is whether there's any way a DSP program can change a speaker's directivity? And, if so, is anything like that on the market now?

With a single driver you're stuck with the directivity defined by the speaker's physical construction. When you start combining multiple speakers you have the physical construction, but you also have the way the sound from the multiple drivers combines. You can alter the combined output so some degree by controling the output of the individual speakers. This doesn't need to be via DSP (the CBT kits do it all with passive components) but using DSP does make it easier to tune parameters, or switch between responses.

 

[Absolute]

Smoothly increasing directivity seems to be subjectively preferred in most listening tests I've seen and my own personal tests. The most famous one of course is the Salon 2 vs JBL M2.

It's popular to cite this particular comparison, but my problem with that is that this is only one data-point. Interestingly one of the participants bought both the M2 and the Salon 2 and had them in his home at the same time for a while. He ended up preferring the M2 at home.

Regardless, one comparison of two very different speakers doesn't give enough data to assume particular causation of a result. It could be the directivity, it could be that the M2 needs a small high-shelf in a small room to avoid being bright due to a small increase in sound power, it could be that the Salon has more drivers closer to the floor and thus is impacted less by the dreaded SBIR dip in the upper bass etc.
We just don't know until we dig more into it.

 

[phoenixdogfan]

It's popular to cite this particular comparison, but my problem with that is that this is only one data-point. Interestingly one of the participants bought both the M2 and the Salon 2 and had them in his home at the same time for a while. He ended up preferring the M2 at home.

Regardless, one comparison of two very different speakers doesn't give enough data to assume particular causation of a result. It could be the directivity, it could be that the M2 needs a small high-shelf in a small room to avoid being bright due to a small increase in sound power, it could be that the Salon has more drivers closer to the floor and thus is impacted less by the dreaded SBIR dip in the upper bass etc.
We just don't know until we dig more into it.

Definitely seems there is not enough research on this. Would be nice if the work of the Harman Laboratories was checked by other independent researchers. Who knows, maybe they could find variables other than directivity influence subjective preferece in loudspeaker reproduction, perhaps even more strongly.