Effect of Loudspeaker Directivity Compared with In-room Measurements

[markus]

Those are from vendor specs. The highest scoring speaker is 8030c with score of 9.0.

I just picked the first small speaker with a high calculated preference rating that is definitely not cardioid and not broad constant directivity. Cardioid being somewhat the topic of this thread.

 

[Kvalsvoll]

I don't own any cardiod type speakers, but I do have the KH120 (since it was already mentioned) to test easily side-by-side the Sceptre S8.

The KH120 has wider directivity above 2 kHz owing to its waveguide, but also less controlled directivity in the mids due to its smaller driver size and baffle.

Both monitors are placed in a very compromised position near the immediate sidewall, and somewhat in the middle of a hallway -- absolutely necessary due to space constraints in the room I'm in. Both monitors are pointing exactly on-axis to the center MLP of my main listening couch.

View attachment 174267

While I am certain the KH120 will have a higher preference rating score, we know that doesn't account for everything.

DISTORTION
View attachment 174268
KH120 ~vs~ S8

There's probably a 1dB (maybe less?) loss of efficiency in the low end of the Sceptre S8 due to my having added extra damping inside. The improvement in simple measured distortion sweeps is negligible in reality, but it did help reduce some resonance between 400-500Hz (as evidenced by nearifield wavelet and burst decay spectograms compared in the past) so I kept the modification.

For distances of 2 meters or more, the Sceptres to me are more preferable due to the better low-end performance -- both use limiters and that flash alarmingly bright red when active. Needless to say, the Neumann KH120 starts limiting earlier and is a bit unsatisfactory when it comes to loud listening; bass subjectively comes across as "boomier" and a little "hyped" even before I added the extra damping to the S8.

You may have noticed the steeper slope in the high frequency of the KH120 above 12 kHz or so... destructive interference with the adjacent sidewall seems to be unavoidable here in this position.

View attachment 174269
*note last two (60 degree horizontal) traces

The Sceptre S8's narrowing directivity above 12 kHz helps to avoid combing/cancellation in the aforementioned region. I also think the narrowing directivity and dips (normally considered as "bad") makes this speaker sound less "harsh" to my ears -- notwithstanding other disadvantages like the high-mid excess and off-axis "bunching" between 6-11 kHz -- which can be reduced with EQ, according to taste.

With/out 5 cycle Windowing applied
View attachment 174270
*note the somewhat worse performance between 400-1,300 Hz of the KH120 with it's smaller, and less directive mid-woofer


View attachment 174271
effect of bunching between 6-11 kHz from the S8's small horn directivity waveguide is evident in this spectrogram view

If you really look closely above, we see that between 400-1,300 Hz, the S8 actually has better time domain performance -- at the final MLP.

ZOOMED-IN VIEW
View attachment 174273
more coherent or controlled mid-energy decay readily evident from the S8

That's all...


BTW, I just want to ask why the constant insinuation of some nefarious intent behind the data (before and after spectrograms) and explanations previously posted? I don't really understand why @markus has to keep on repeatedly insisting on getting the mdat data files. I mean, it would be nice, but not totally necessary. The example graphs @Kvalsvoll provided already seems pretty self-evident to me: where controlled directivity of some speakers can help improve performance in a real room. People's actual in-room situation may vary from the specific examples provided, of course -- as with this particular little side case note of mine.

It is possible to see from the measurements that those speakers are different, when we know what to look for. The S8 with a larger mid/lf radiating surface gives a bit more directivity control, enough that it can be seen here.

The point here is the radiation pattern, not how this pattern is achieved. If the speaker is cardioid or not, is irrelevant. As this shows, just being larger changes the pattern enough to give a measurable difference in the time domain, and this can explain why speakers sound different even if the frequency response is similar.

 

[Kvalsvoll]

I have measurements from 2 different speakers, set up in 2 different rooms. This is interesting, because then we can see how the differences between the speakers are affected by room acoustic properties.

We can also see how the response of the same speaker changes with different room acoustics.

I have to make the pictures and put together some text for this, in-between, then I will post it here.

 

[Kvalsvoll]

While we wait for this yet-another-round of measurements and graphs - that maybe is not really necessary or of much use to most people, look at this comparison done by @Bjorn , of 2 different horns:

One moment, please...

 

[tuga]

Excellent engineering with unproven benefits

Objective or subjective benefits?

Because if you mean subjective then it is a matter of taste, and thus it depends on who you ask.
And, as has been mentioned, in-room performance/benefits are also relative depending on the room (size, construction, amount of treatment).

 

[thorvat]

While we wait for this yet-another-round of measurements and graphs - that maybe is not really necessary or of much use to most people, look at this comparison done by @Bjorn , of 2 different horns:

One moment, please...

Well, this comaprison is subjective only, and I can't resist the impression that bear fur on the floor provides great help in enjoying in those 2 horn speakers. Glass of fine drink would help even further!

 

[markus]

Objective or subjective benefits?

Because if you mean subjective then it is a matter of taste, and thus it depends on who you ask.
And, as has been mentioned, in-room performance/benefits are also relative depending on the room (size, construction, amount of treatment).

Cardioid is first and foremost an engineering challenge. Whether the design is working or not can be objectively demonstrated with measurements. What problems it actually solves hasn't been evaluated in an objective way though. I've made a couple of suggestions how that could be done but it was rejected as "demanding an unreasonable level of proof".

If someone would present a "rotated cardioid pattern" I would be very interested by the way as it tries to solve a fundamental objective problem of stereo, the small sweet spot. See http://www.aes.org/e-lib/browse.cfm?elib=5177

Source: https://pure.tue.nl/ws/files/2873329/Metis235355.pdf

 

[tuga]

Cardioid is first and foremost an engineering challenge. Whether the design is working or not can be objectively demonstrated with measurements. What problems it actually solves hasn't been evaluated in an objective way though. I've made a couple of suggestions how that could be done but it was rejected as "demanding an unreasonable level of proof".

If someone would present a "rotated cardioid pattern" I would be very interested by the way as it tries to solve a fundamental objective problem of stereo, the small sweet spot. See http://www.aes.org/e-lib/browse.cfm?elib=5177

View attachment 174679

Source: https://pure.tue.nl/ws/files/2873329/Metis235355.pdf

Cardioid, through the control of directivity, addresses a very real issue by reducing (early reflection) room interference. Sufficient evidence has been posted already as far as I can see.

 

[markus]

Cardioid, through the control of directivity, addresses a very real issue by reducing (early reflection) room interference. Sufficient evidence has been posted already as far as I can see.

The discussion has become repetitive.

 

[tuga]

The discussion has become repetitive.

Start a new one.

 

[markus]

Start a new one.

I just tried. Obviously it didn't work.

 

[Kvalsvoll]

Cardioid is first and foremost an engineering challenge. Whether the design is working or not can be objectively demonstrated with measurements. What problems it actually solves hasn't been evaluated in an objective way though. I've made a couple of suggestions how that could be done but it was rejected as "demanding an unreasonable level of proof".

If someone would present a "rotated cardioid pattern" I would be very interested by the way as it tries to solve a fundamental objective problem of stereo, the small sweet spot. See http://www.aes.org/e-lib/browse.cfm?elib=5177

View attachment 174679

Source: https://pure.tue.nl/ws/files/2873329/Metis235355.pdf

Here you point out something that is challenging, not only for stereo, it applies to multichannel as well, and a center speaker does not fully solve this issue. Since you also only have a minor insult in your comment, it deserves a reply.

The problem lies in the fact that as the listener moves, the distance to the different sound sources change, and this destroys the timing. While this is not possible to solve completely, it can be improved a lot, and this article describes how.

And indeed, speakers with a radiation pattern that gives better stereo across a wider area exist. Some speakers collapse all sound into the closer speaker as you move to the side, while others manage to still present a sort of stereo soundstage, covering the whole width of the room, even when you listen from far left or right.

The worst is a box speaker with collapsing high-frequency pattern, with no toe-in. The better ones are horns, toed in towards the center listening position.

The "cardioid" is typically used to control the pattern in the lower midrange, this is not sufficient, and the pattern is usually chosen too wide to have any huge effect for this specific issue. Without pattern control at higher frequencies, it will not work. The solution is to use some sort of horn for high frequencies, so that it is possible to create a radiation that matches closely a desired pattern.

This makes it possible to achieve a more consistent sound across a wider area. Frequency response that does not change much across this area, and a small reduction of overall loudness when moving off-axis. In center there will still be a precise rendering, while off-center is not equal, and images will move towards the closer speaker, but there can still be a wide soundstage far off-axis, and the images do not collapse into the closer speaker.

What exactly happens far off-axis is not so simple. Timing will also be affected when the far speaker is louder.

 

[thorvat]

Timing will also be affected when the far speaker is louder.

Hmm.. You may want to re-think this statement.

 

[Vuki]

imo just like high performance racing car, high performance stereo system is single seat affair.
Who needs wide sweet spot and why? For casual listening off centre is quite good too.

 

[Holmz]

imo just like high performance racing car, high performance stereo system is single seat affair.
Who needs wide sweet spot and why? For casual listening off centre is quite good too.

What about group B ralley cars?

One can extend the two seat affair with the single seat to company with a partner listening to the music… versus solo.

 

[Vuki]

What about group B ralley cars?

One can extend the two seat affair with the single seat to company with a partner listening to the music… versus solo.

One is driving the other is suffering

 

[markus]

One is driving the other is suffering

Sounds like he's having quite a bit of fun

 

[Kvalsvoll]

Hmm.. You may want to re-think this statement.

Very bad formulation, changing the level does of course not move the signal in time by itself. But it is the time that is the problem here, and the reason why this fix only partially manages to solve the problem.

 

[Kvalsvoll]

imo just like high performance racing car, high performance stereo system is single seat affair.
Who needs wide sweet spot and why? For casual listening off centre is quite good too.

Yes, that is my conclusion as well. As long as tonality and clarity is still good, the sound can be good enough across the whole room. But there is a difference here, between systems - some still sound much better off-center.

 

[Kvalsvoll]

This method described in the article to achieve consistent imaging across a wide area is only partially successful. I will try to explain why, and it is easy to test for yourself, on your own system.

We have a vocal located in center position:

Then we move it to the left, either by moving our listening position to the left, or delaying the right speaker:

To restore this, level is reduced on the left speaker and increased on the right speaker. What we get, is something like this:

The image moves back to center, sort of, but it is no longer a solid, consistent image, parts of it is still left back on the left side, and the overall impression is a smeared image that lacks the clarity and solidity of the original.

This can be explained from what is known about how hearing works. The higher frequencies are moved back quite well, so the higher frequency spectrum from the object is now moved back to center. The lower frequency part which depends on time arrival for location, is not much affected, and thus remain at its far left location. This gives an image that is now spread around and no longer resembles a solid, connected object with clear boundaries.

In the article, it is claimed that the objects are located in the same position when observed from across the whole listening area. And this can be true, for that specific system and set-up. For a system that is able to reproduce realistic images, which requires control across a much wider frequency range, this is not true - the images will change when you move far off axis, and it is not possible to fix this by manipulating level from the left or light channel speaker.

What can be fixed, is tonality and frequency response errors at far left or right locations, and this will also give a much better spatial impression at those locations. Allowing images to move a little towards the closer speaker is not destructive to the experience.