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Multi-Way Conventional loudspeakers with crossovers

An Improved Array
An Improved Array
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Old 27th December 2016, 05:27 PM   #11
wesayso is offline wesayso  Netherlands
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Quote:
Originally Posted by Grasso789 View Post
Hi, forget money. I have seen JBL's CBTs, Don's long-bows, Don's and Mister Horbach's and Follgott's FIR stuff, Follgott's CBT+horn combinations, Bessel arrays, simple and J-shaped line arrays and beaming by destructive interference as in Kiii, open baffles and now Beolabs. But the only effective arrays, effective in ratio of sound quality to building effort, are some big-*** Public Adress ones, because 18" is maximum driver size yet too few for a stadium, JBL's inobtrusive church CBTs, Follgott's principle of combining array and horn, and my Krassolito. Krassolito: Wide-range drivers, possibly stopped (read: less than) first-order filters and possibly bent baffles. Combine simple bricks well, avoid what is bad. Forget money.
I have no idea what you just said, sorry .
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Old 27th December 2016, 07:12 PM   #12
Patrick Bateman is offline Patrick Bateman  United States
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Originally Posted by FoLLgoTT View Post
With my line array with waveguide prototype I also tried the Bessel array a time ago. The directivity is close to that of the single driver. This means beaming above 10 kHz is the same, too.

Bessel array with 1" drivers:
An Improved Array-bessel-vertikal-ohne-stege-png

Directivity index is not very good. An 1-dimensional Waveguide does a better job and takes not much more space than such an horizontal array.

The idea to change directivity "on the fly" is tempting. But I still don't see the real benefit in home use.
I think waveguides are the 'gold standard' for directivity control.

The thing that's so enchanting about the Beolab 90 is that it has that 'waveguide speaker' sound, but with more spaciousness.

I'm not sure if I can describe the difference, but I'll try:

Big waveguides eliminate early reflections, and I believe this is a large part of the reason that their imaging is so pin-point. For instance, a Danley SH-50 can create a center image that's so solid, you would swear there's a speaker there. The images are solid as a rock.

Dipoles create a big spacious soundstage, largely due to reflections off the back wall I think. Cardioids are similar in nature. For instance, the Gradient Helsinki creates a very pleasant soundstage, it's big and it's spacious.

Beolab 90 seems to do both; it has that 'giant headphone' effect like the SH-50, but there's also "space" like the Gradient Helsinki.

One theory I have is that we can perceive the early reflections in a waveguide, and it reduces the soundstage size. Basically the bigger the waveguide, and the "less perfect", the more the soundstage suffers.

This is pure speculation of course. About the only evidence that it may be true is that I've noticed that waveguides that feature really clean impulse response seem to "disappear" into the soundstage better. An example of this is the 18Sound XT1086.

I wish I had some big LeCleach horns to test this hypothesis. If you look at their simulated impulse response in Hornresp, it's about as clean as it gets.

But back to the subject at hand!

Click the image to open in full size.
The Beolab 90 patent is very difficult to follow, but it's referenced Mr Stiles' Bessel patent. The B90 uses a circular array.

So...

It's possible that the circular array in the B90 is some type of improved Bessel array, possibly inspired by the Stiles array.

Click the image to open in full size.
Here's one last thing to ponder. I don't know how many of you have heard the Gallo Acoustics speakers. They come *really* close to that ideal that I mentioned, the ability to generate a rock-solid center image while also creating a big stage. Basically the best attributes of a waveguide speaker like the SH-50, along with the best attributes of a good cardioid or dipole.

Obviously, the enclosure plays a big part in this.

Click the image to open in full size.
Fujitsu's speaker also has jaw-dropping imaging. At CES last year, it was shocking that this unassuming speaker imaged better than many $100K setups. And look at it! It's basically a $15 Tymphany TG9 in an egg. It sells for $1000.

Just to be sure that I wasn't taking Crazy Pills, I 3D printed a similar enclosure, and loaded it with a Tymphany TC9. Sure enough, it sounds incredible. (Measures really great too!)

Of course there's a "but" here...

The power handling on these speakers is dreadful. Imaging in spades, no dynamics.

But a Bessel array of five drivers raises the output level by 6dB over a single driver, and the improved Bessel array described in Stiles' patent gets that even higher.
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Old 27th December 2016, 08:26 PM   #13
Patrick Bateman is offline Patrick Bateman  United States
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Let's see what the Bessel array looks like in Hornresp.

Click the image to open in full size.
Click the image to open in full size.
Here's my enclosure. It measures 43.5cm wide and 6cm deep. There are five drivers, each with a diameter of 4.5cm. The center to center spacing is 6cm.

It's your basic computer speaker, fairly similar to the Harman Sound Sticks, but arrayed horizontally instead of vertically.

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Here's the wavefront shape at 1000hz, 2000hz, and 3000hz

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
I can't make a "true" simulation of a Bessel in hornresp because there's no way to vary the voltage to the elements in the wavefront simulator.
But I can get close; we can see the effect of the reversed driver in the array. The pics above show the results at 1000Hz, 2000Hz, and 3000Hz.

Some random observations:
1) The straight array is WAY more directional, it's basically firing a narrow beam at high frequency, a beam that 'spreads out' as the frequencies get lower.
2) Possibly the most interesting thing about the Bessel array is that the nulled driver 'steers' the beam quite a bit! In the sims you can see that the Bessels' beam is significantly tilted away from the nulled driver. This opens up some interesting possibilities; seems like it would be possible to use phase to 'steer' the wavefront to a specific spot in the room. This is particularly useful with a MiniDSP. For instance, you could create an all-pass filter in a MiniDSP to steer the beam at high frequency, while leaving the low frequencies unaltered. Basically simulate the beam control of a waveguide at high frequency, while leaving low frequencies unmodified. (So you don't lose a ton of efficiency.)

Interesting stuff.
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Old 27th December 2016, 09:20 PM   #14
Grasso789 is offline Grasso789  Germany
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Wesayso, i do not understand any of that imaging, soundstage, focus talk. You, especially Patric, hear things, which are not there, you dream, phantasize. Since you do that, you fall for things, for which i would not fall. If Beolab90 were full of bugs, you would not hear them. In a trade show in a big hall you do not have much horizontal and ceiling reflections anyway. Your conclusions are worth next to nothing, at least not in a scientifically provable context.
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Old 27th December 2016, 09:43 PM   #15
Patrick Bateman is offline Patrick Bateman  United States
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For my next trick, let's look at the wavefront shape of something like the Beolab 90.

Click the image to open in full size.
Click the image to open in full size.
From the patent application, the enclosure is hexagonal. On each face of the hexagon there is a single driver, except for the front and the back. The back has no drivers, and the front has three.

Click the image to open in full size.
Click the image to open in full size.
Hornresp can only simulate wavefronts in two dimensions, so I've only simmed six of the seven drivers in the cabinet. (I omitted one of the three drivers on the front.)
My hexagonal enclosure is 24cm deep, and each face of the hexagon is 13.5cm in diameter. The drivers are the same as the sims from post #13, they're 4.5cm in diameter.

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Here's the wavefront shape of the loudspeaker at 1000Hz, 2000Hz, and 3000Hz.

Click the image to open in full size.
I'd expected that the Beolab 90 would be omnipolar with all drivers playing, but it's not. It's a straight up cardioid. And the wavefronts are quite exact; I don't know that I've seen anything so cardioid-ish from a speaker. (I've messed around plenty with various cardioid types, and they can be frustrating because it's easy to get a speaker to be cardioid at a single frequency, but trying to make it cardioid over a wide range is very difficult. Even John Kreskovsky stopped selling his cardioid sub a few years back. From what I read on this forum, he ceased selling it because the performance was so dependent on stuffing that the results would be unpredictable for customers.)
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Old 27th December 2016, 09:59 PM   #16
Patrick Bateman is offline Patrick Bateman  United States
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Hornresp has yielded some interesting results here.

This is speculation on my part, but here's what I'm seeing from the data in post 15:

Click the image to open in full size.
When B&O takes a "straight array" and wraps it around a hexagon, the wavefront shape becomes cardioid. The cardioid response is particularly noticeable beginning at 2000Hz. The enclosure from post #15 is 26cm wide. 2000Hz is 17cm wide. So it looks like the width of the hexagon largely dictates how low the directivity control goes. IE, you'd want an enclosure that's wide at the bottom (for lower directivity control) that tapers to a "point" at the top. The Beolab 90 is a three way speaker apparently, albeit a strange looking one.

Furthermore, I'd speculate that there's three drivers on the front, and zero on the back, to make the cardioid more directional. IE, if you put a single driver on all six faces, the response would likely be closer to omni.

Off the top of my head, if you were making a three way speaker like this, with the following crossover points, you'd want the following sizes:

1) A tweeter array with a crossover of 2500Hz would measure approximately 14cm in diameter. (5.5")
2) A midrange array with a crossover of 350Hz would measure approximately 97cm in diameter (38")


Of course, the midrange array is NOT that wide.

But I think there's a solution! I'll bet you could combine this hexagonal line array with an end-fire array. Basically use DSP delay to strengthen the forward lobe.

Stay tuned, hornresp can model that...
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Old 27th December 2016, 10:16 PM   #17
wesayso is offline wesayso  Netherlands
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Have you played in Hornresp with the pair on each of the sides directly beside the 3 frontal driver out of phase? It is interesting as B&O will have the advantage of playing with levels and phase for each driver.
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Old 27th December 2016, 10:20 PM   #18
Patrick Bateman is offline Patrick Bateman  United States
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Originally Posted by wesayso View Post
Have you played in Hornresp with the pair on each of the sides directly beside the 3 frontal driver out of phase? It is interesting as B&O will have the advantage of playing with levels and phase for each driver.
I'm starting to think it's a plain ol' straight array wrapped around a hexagon.

Not entirely sure why they referenced the Stiles patent at all. Perhaps because Stiles is using all-pass filters, so that the phase at high frequencies is different than the phase at low frequencies?

I did a sim of the same enclosure as a Bessel array and it was quite a mess. The near-perfect cardioid pattern just turned into a mess of lobes. I'll post that after I post the end-fire results.
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Old 27th December 2016, 10:25 PM   #19
wesayso is offline wesayso  Netherlands
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I was thinking of the steering effect in the straight array and not using an out of phase driver on the front end, just wondering out loud if that's the beam steering they used as they have about 3 big modes, selfish (where they optimise for one listener), normal, where the beam width would be used to supply a couch and party where it would behave more like an Omni.

Now these 3 modes aren't their real names, but you get the drift.

B&O would be able to change the phase and level of each driver. That's a lot of freedom right there.
However it may just be level and delay. Though I expect they do use some extra tricks in the selfish mode with mid/side EQ.
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Last edited by wesayso; 27th December 2016 at 10:34 PM.
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Old 27th December 2016, 10:46 PM   #20
mitchba is offline mitchba  Canada
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Don't know if you have seen this article: B&O Tech: Beam Width Control A Primer earfluff and eyecandy

Happy Holidays guys!
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