Controlled directivity speakers

[TimVG]

If one take the plunge to read the whole story: "Some of the improved properties may be due changes in the in–situ magnitude response." (page 62)

But these changes would be a direct consequence of the differences in directivity, which is a good thing - so I don't understand the facepalm reaction. If you want to compare the differences between DI's, of course you don't want to equalize the responses. Then you introduce a new variable.

 

[fineMen]

But these changes would be a direct consequence of the differences in directivity, which is a good thing - so I don't understand the facepalm reaction. If you want to compare the differences between DI's, of course you don't want to equalize the responses. Then you introduce a new variable.

To the contrary, and that is the 'face palm' for: if the difference was just due to differing sound power, why then bother with directivity. One could use an equaliser instead

 

[TimVG]

To the contrary, and that is the 'face palm' for: if the difference was just due to differing sound power, why then bother with directivity. One could use an equaliser instead

Because in the lower midrange, by equalizing the response, we'll degrade the direct sound, which will have an arguably bigger impact on the perceived sound than if you were to leave it as-is.

 

[fineMen]

Because in the lower midrange, by equalizing the response, we'll degrade the direct sound, which will have an arguably bigger impact on the perceived sound than if you were to leave it as-is.

Ja, sure! Still the 'thesis' was aimed at that very question, if directivity was directly or indirectly beneficial. He missed to exclude other reasons for better preference, as to say. Hence the thesis is again left to be speculative.

... if that makes any sense to a human mind

Anyway, I've got a plan (s/ above). The automated vacuum cleaner will make the deal.

 

[TimVG]

One thing that I have measured myself with such a loudspeaker, is a smaller mean spatial variance in the lower midrange over a larger area compared to a conventional loudspeaker. That's one thing at least you cannot fix with EQ.

 

[fineMen]

One thing that I have measured myself with such a loudspeaker, is a smaller mean spatial variance in the lower midrange over a larger area compared to a conventional loudspeaker. That's one thing at least you cannot fix with EQ.

The contrary is to be expected ... as explained before.

Nevertheless, coming back to the sound balance, changed by less reflections in the lower mids, as compared to conventional speakers.

Don't we get back into the infamous "circle of confusion"? What if the studio which designed the recording did so with reference to conventional speakers, with steadily increasing dispersion towards the lower mids?

Again, I'll first try to validate the concept for itself: does it actually work, if positioned close to a (front) wall?

c/u

 

[abdo123]

One thing that I have measured myself with such a loudspeaker, is a smaller mean spatial variance in the lower midrange over a larger area compared to a conventional loudspeaker. That's one thing at least you cannot fix with EQ.

This is completely logical as the higher directivity will push the transition frequency of the room much lower.

With multi-subs working below 100Hz this should provide a state of the art system.

Are you open to the idea of hosting auditions any time soon?

 

[abdo123]

He missed to exclude other reasons for better preference, as to say. Hence the thesis is again left to be speculative.

It's not that he missed that, it's that he cannot exclude all the other reasons.

At the end of the day if two speakers have different directivity you can only equalize them to have the same on-axis response, the same early reflections response or the same sound power response.

 

[fineMen]

This is completely logical as the higher directivity will push the transition frequency of the room much lower.

Really, what's the math behind this?

At the end of the day if two speakers have different directivity you can only equalize them to have the same on-axis response, the same early reflections response or the same sound power response.

Did You read the paper completely? All down to the final summary the author refers to masking effects and the like, and in doing so addresses timely properties of reflections. Once reaching a final statement, he, in a sudden, switches to say that his investigations are not conclusive, because all the observations could be due to trival sound balance. I won't say this is a disgrace, but usual in this field of physiology.

Still my argument regarding the reintroduction of the 'circle of confusion' holds.

Stick to the standard, please. Do not try to conquer new grounds without taking the studio guys with You. Stop investigations on 'stereo' altogether and steer the expenses towards real problems ;-)

btw., learning question: what about (real) in-wall speakers?

 

[abdo123]

Really, what's the math behind this?

it basically has the same effect as treating the room.

an anechoic room has the least amount of spatial varaiation because the walls don't reflect sound, but if you don't radiate the walls with sound to begin with then you arrive at the same conclusion / effect.

 

[fineMen]

it basically has the same effect as treating the room.

I don't think so. This has some more into it.

Anyway, the paper / thesis. It is not a personal thing, and I do not accuse the guy individually. I just compare the methodology to what I was educated to do.

Why didn't he state a hypothesis to begin with. Why not discuss with himself by which means he would proof it wrong. It would have been so easy to compensate - or not, for the differing spectral balance. Even as an aftermath.

Please bear in mind, that 'stereo' is a completely artificial thing made in the studio. It is designed anew record by record to the sound engineer's and maybe the musician's liking. Reference is the studio's equipment, or in general its setup. Your milage at home varies, logically.

So why then only 3 test signals, plus noise, which is utter nonsense in this regard. And so on, always the same. Inconclusive speculation on a topic in the realm of a big industry. Harman did a good job in convincing people of a standard. Let's exploit it a bit longer, before we run for something new - ahh: better!

 

[TimVG]

The contrary is to be expected ... as explained before.

But reality says different, which is what matters in the end

Don't we get back into the infamous "circle of confusion"? What if the studio which designed the recording did so with reference to conventional speakers, with steadily increasing dispersion towards the lower mids?

Many mastering studios use large in-wall mounted loudspeakers which by default have absolutely no radiation to the rear and due the infinite baffle, also feature controlled radiation in the lower mids. It's not that controlled radiation to the lower mids is a new concept, speakers used to be larger on average (physically) anyhow.

Neutral direct sound, and reflected sounds which spectrally match it is the only logical goal to strive for, imo.

 

[ctrl]

I hope @TimVG and @Rick Sykora won't take offense (both building r2 prototypes) if I post results from Tim's first Directiva R2 prototype here.

The diagrams are based on real measurements (no simulation, except XO), the fliter slopes and crossover frequency are not final yet, so there can still be significant differences in the vertical radiation (ignore all below 200Hz in the diagrams).

Since half of the slots were covered when measuring the vertical FR (Tim had no better choice for vertical measurements), the vertical radiation should be somewhat better controlled in reality.

In order to better illustrate the "problem" of dispersion with small loudspeakers, the on-axis normalized sonograms of the r2 are contrasted with those of the comparably sized Neumann KH80 ***.

Hor normalized sonogram Directiva r2 (black line is -6dB limit), then KH80

Ver normalized sonogram Directiva r2 (black line is -6dB limit), then KH80

Therefore, a small "normal" (without directivity control) speaker plus subwoofer can never achieve the radiation characteristics of a large floorstanding speaker - however one may evaluate this in terms of sound quality.

Besides the already mentioned differences in the ratio of direct to diffuse sound for loudspeakers with controlled directivity (compared to "normal" speaker), small loudspeakers with controlled directivity below 1kHz, have the possibility to achieve the dispersion characteristics of wide floorstanding and horn loudspeakers.
How this affects the sound will be exciting to observe as the r2 develops.

*** Update: Of course, the comparison is not entirely fair, since the r2 can only be used down to 150-200Hz, so it needs at least one more driver.

 

[Schollaudio]

I would not say with certainty that directivity control as low as possible is needed, but if you can do it down the transition frequency then you can be assured that in the range where it potentially still audibly matters, the reflected sounds are spectrally more similar to the direct sound than with a more conventional loudspeaker, which is never a bad idea.
There's many different ways to achieve a goal like this, but it is tricky if you are trying to do it in a smaller speaker. Not impossible though, as we've already proven. For our R2 project we have settled on controlling the beamwidth down to somewhere between 200 and 300Hz, which should suit many rooms well.

Agreed, I don't see the point of controlled directivity below the Schroeder frequency.

With making good device choices a 15" woofer and horn crossed at 700ish hz will have good directivity.

 

[Rick Sykora]

I would not say with certainty that directivity control as low as possible is needed, but if you can do it down the transition frequency then you can be assured that in the range where it potentially still audibly matters, the reflected sounds are spectrally more similar to the direct sound than with a more conventional loudspeaker, which is never a bad idea.
There's many different ways to achieve a goal like this, but it is tricky if you are trying to do it in a smaller speaker. Not impossible though, as we've already proven. For our R2 project we have settled on controlling the beamwidth down to somewhere between 200 and 300Hz, which should suit many rooms well.

I thought I should add that Directiva r2 requirements were intentionally scope limited to NOT consider improved directivity much lower than 200-300 Hz...

This was not because it cannot be done but was to keep the bass module simple and time constrain the overall effort. Clearly while a bass module with a different radiation pattern is possible, it would have complicated the r2 project. Something like a dipole bass module is possible, but felt it was better left to those who are interested in extending into low bass frequencies.

In any case, I am not expecting Amir will be prepared to measure either and lower bass measurements are where a Klippel would come in handy.

 

[abdo123]

By the way there might be something in the works that would make things like controlled directivity in the upper bass / low mids kind of moot.

Dirac has been developing for quite a while a room-wide multi-speaker room correction (they call it spacial room correction technology) that is supposed to dynamically use every speaker available to smooth out the in-room response AND reduce seat to seat variation.

From what i understand if speaker A would have a cancelation speaker C would play the frequency instead with a delay. Ofcourse it's MUCH more complex than i what have just shared.

Feel free to read the sneak peak article for more information https://www.dirac.com/the-arrival-of-spatial-room-correction-technology/

The emergence of such technology would instantly shift the focus to output capibility and extension (R1 project already succeds in that in several ways).

 

[jhaider]

Bad week: 2 bugs! I fixed this one, website is currently uploading corrected contours. Thanks for pointing the discrepancy.
Corrected version for the Revel:

View attachment 195291

This frequency scaling is also much better than the Klippel default polar maps, which waste too much space showing bass frequencies and compress midrange dispersion disruptions.

 

[TimVG]

Are you open to the idea of hosting auditions any time soon?

I may plan something like that in summer. Still working out the details.

 

[tuga]

So, why do it? The only reason to not do the cardioid is the placement of drivers on the side or back, which kind of looks too technical for my significant other.

What would she say of something like this?

 

[fineMen]

Many mastering studios use large in-wall mounted loudspeakers which by default have ...

Exactly, no argument about this. Good point for the camp of "less reflection (in the lower mids) is better". (That is why I asked for in-wall above ;-)

Neutral direct sound, and reflected sounds which spectrally match it is the only logical goal to strive for, imo.

Alas, "the score" and with it the suggested standardization follow another route, me thinks.

Again beating the dead horse:

Harman's recommendations aims at the consumer market. Designs shall be kept practical regarding placement, cost, looks etc. Less complication, more sales.

For me personally it boils down to a notion like this, and I feel it cannot be said too often:

stereo / fidelity is a thing generated in the studio, especially there is nothing in the primary recording that is 'naturally original'
stereo / fidelity is a matter of taste, first of all taste of the sound engineer, especially the taste cannot be disputed
stereo / fidelity is best preserved if play-back at home replicates the sound engineer's experience, especially regarding important parameters

So, if the s/e would evaluate the recording / mix using more traditional speakers, and finally would say "well, that's done", that would be it.

In consequence, in order to introduce narrow-dispersion-in-the-lower-mids speakers, You better first convince sound engineers to use them. Then sound engineers have to convince consumers, that the effort--and there is a lot!, is worth it.

Reiterated, the more narrow dispersion first has to add something completely new to the s/ engineer's toolbox to justify itself.

You say: "more punch"
Sound engineer: "can be done with a slight turn on the equalizer too"

You say: "more defined room"
Sound engineer: "got my reverberation add-on already"

... and so on ...

Once I have my down-sized experimental 'cardioid', i'll give note in the DIY section, o/k?