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Open baffle with SB Audience Bianco-15OB350. FR + distortion measurement outdoors and indoors.Plus measurements FR on IEC baffle.

DanielT

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I thought this was interesting. Might be of interest to someone who is thinking of building an open baffle speaker. Too big speakers for me to fit in my living room/ listening room (plus I have other projects going on) but for those who have room for such big ones, why not? They seem to require a lot of EQ. The SB Audience Bianco-15OB350 seem to have low distortion.
Screenshot_2022-11-28_114948.jpg


______
Measurement outdoors:
Screenshot_2022-11-28_114832.jpg

Screenshot_2022-11-28_120252.jpg


______
Measurement indoors:
Screenshot_2022-11-28_120517.jpg

____
Distortion measurement:
Screenshot_2022-11-28_120724.jpg



...plus subwoofer that takes care of everything below 50 Hz seems to be needed, thus there will be many speaker boxes in the room. ...:)
(or rather in this case baffles + boxes).

Edit:
Here are SB's own measurements of them. Performed on an IEC baffle. I don't know the size of an IEC baffle, I might add.
Screenshot_2022-11-28_121436.jpg


 
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DanielT

DanielT

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As usual the companies own measurements are much, much better.
That may be so, but in these specific case it is an open baffle construction in the video and SB's measurements made on an IEC (open?) baffle. Since the shape and size of the baffle is decisive for the FR, it is like comparing apples with pears. This IF the IEC baffle is different in size compared to the one in the video, that is.:)

Edit:
It, size baffle, regarding the lower frequencies in any case. For the higher frequencies, the difference in the video vs. SB is a bit strange.You have a point there.:)
They probably shouldn't measure so differently, I think.
 
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ROOSKIE

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That may be so, but in these specific case it is an open baffle construction in the video and SB's measurements made on an IEC (open?) baffle. Since the shape and size of the baffle is decisive for the FR, it is like comparing apples with pears. This IF the IEC baffle is different in size compared to the one in the video, that is.:)

Edit:
It, size baffle, regarding the lower frequencies in any case. For the higher frequencies, the difference in the video vs. SB is a bit strange.You have a point there.:)
They probably shouldn't measure so differently, I think.
As usual the companies own measurements are much, much better.
I doubt the companies Klippel measurements are off by much.

The IEC baffel is 53"×65" with the driver mounted unequal distances from all 4 sides, and SB was measuring @ 31.6cm (1foot+).

Very different from what JC is doing. There is no way boundary influence is not a factor. Plus edge diffraction with the driver in the middle.
 

ctrl

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Might be of interest to someone who is thinking of building an open baffle speaker.
An interestingly done product introduction for the SB Audience OB driver.
A classic OB baffle. You can't do much wrong there ;)

Perhaps the driver arrangement on the baffle should be reconsidered. If the reference axis is to be at a height of 100cm (39''), then it would be advisable to arrange the driver vertically asymmetrically - the optimal arrangement can be simulated very easily.

The orange frequency response shows the edge diffraction with a fully symmetrical arrangement on the baffle, in blue the slightly optimized position of the woofer with a reference axis at 100cm (39'') height.
1669831691578.png

The horn could then be integrated into the baffle or possibly placed on top of the baffle (then the woofer would probably have to be even further up).

If one removes the hump around 200Hz, one gets a flat free field FR.
1669836904713.png
Sensitivity is pretty good at 93dB@2,83V. However, an f3=70Hz and f6=51Hz delivers almost no low bass - subwoofer, as said in JC blog post, is a must.

For low bass using a passive crossover, sensitivity must be sacrificed, so that ultimately only 84dB@2,83V or something similar can be achieved.
If you don't want to use a subwoofer, consider using two 15'' woofers per speaker, with the lower woofer crossed earlier - 2.5-way speaker.
 
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DanielT

DanielT

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The IEC baffel is 53"×65" with the driver mounted unequal distances from all 4 sides, and SB was measuring @ 31.6cm (1foot+).
Perhaps the driver arrangement on the baffle should be reconsidered.
This with asymmetry. I think you are on the right track. Also in a general, it can certainly be worth keeping in mind regarding measurements on speaker element
on IEC baffles (it measures as it does because the conditions are such).:)

This is how SB themselves measured their SB Audience Bianco-15OB350:

Screenshot_2022-11-30_211205.jpg

Regarding IEC Baffles.From that link CristianoLO gave in #4:

Asymmetrical baffles, enough ditto, reduce edge distortion effects. To be on the safe side, round the corners of the baffle. Extra round,extra safe.:)
 
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ROOSKIE

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To be on the safe side, round the corners of the baffle. Extra round,extra safe.:)
My understanding is that rounding the edges of an open baffle is not advisable, at least from the mids on up. (Bass below about 200hrz is a different matter but it would not be affected by small round overs anyway)

The edge diffraction artifacts I was referring to were specifically reguarding asymmetry vs centered. (Compounding diffraction at the same frequencies)
I believe it is good to give the front and rear waves some space before they meet to help develop the figure 8 radiation pattern equally front to back. So I suspect keeping that sharpe edge is good idea.

Linkwitz is gone now and his designs are a bit older time wise now, but likely still SOTA in terms of dipole/ob designs using conventional drivers.
He pretty much covers every single aspect and nuance of designing on his website which is still available. Plus no bulky huge baffels, though still a pretty complex set-up vs a set of passive or active boxes.
 
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DanielT

DanielT

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My understanding is that rounding the edges of an open baffle is not advisable, at least from the mids on up. (Bass below about 200hrz is a different matter but it would not be affected by small round overs anyway)

The edge diffraction artifacts I was referring to were specifically reguarding asymmetry vs centered. (Compounding diffraction at the same frequencies)
I believe it is good to give the front and rear waves some space before they meet to help develop the figure 8 radiation pattern equally front to back. So I suspect keeping that sharpe edge is good idea.

Linkwitz is gone now and his designs are a bit older time wise now, but likely still SOTA in terms of dipole/ob designs using conventional drivers.
He pretty much covers every single aspect and nuance of designing on his website which is still available. Plus no bulky huge baffels, though still a pretty complex set-up vs a set of passive or active boxes.
If we take it regarding tweeters. For example this one currently highly appreciated and used tweeters:SB26ADC-C000-4
SB themselves have measured it on an IEC baffle and I assume, but I don't know, that an IEC baffle does not have round baffle corners. Then you get this FR.Which looks good and with such a wide and large baffle no rounded edges seem to be needed:
Screenshot_2022-12-01_090834.jpg


BUT in practice, when building speakers, edge diffractions can cause trouble for tweeters because you rarely build speakers for home HIFi use that have a baffle as large as the IEC standard. The solution then, with smaller, narrower baffles, to counteract edge diffraction effects, can be round baffle corners. Here is a simulation:
100x40 rounded (2).png

100x40 rounded diff (2).png



Or you can add a waveguide to the tweeter so you don't need such round corners as, for example, McFly did when he used that tweeter and then he got this FR. Narrow baffle but also slightly round baffle corners:
IMG_0365 (2).JPG

M105 Copy as built measured Power+DI.png

More measurements can be found in MCFly's DIY thread:

Here the same tweeter, with waveguide and hardly any round baffle corners at all but it seems to work well as long as wavegudide does a good job.:)
Revel M105 bookshelf speaker Audio Review (1).jpg


 

ROOSKIE

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If we take it regarding tweeters. For example this one currently highly appreciated and used tweeters:SB26ADC-C000-4
SB themselves have measured it on an IEC baffle and I assume, but I don't know, that an IEC baffle does not have round baffle corners. Then you get this FR.Which looks good and with such a wide and large baffle no rounded edges seem to be needed:
View attachment 246960

BUT in practice, when building speakers, edge diffractions can cause trouble for tweeters because you rarely build speakers for home HIFi use that have a baffle as large as the IEC standard. The solution then, with smaller, narrower baffles, to counteract edge diffraction effects, can be round baffle corners. Here is a simulation:
View attachment 246962
View attachment 246963


Or you can add a waveguide to the tweeter so you don't need such round corners as, for example, McFly did when he used that tweeter and then he got this FR. Narrow baffle but also slightly round baffle corners:
View attachment 246964
View attachment 246965
More measurements can be found in MCFly's DIY thread:

Here the same tweeter, with waveguide and hardly any round baffle corners at all but it seems to work well as long as wavegudide does a good job.:)
View attachment 246970

None of these are open baffle.
I do design speakers as a hobby so I understand rounding is often a benefit to them when making typical boxed speakers.
The waveguide in the Revel is doing it job and no round over is really going to benefit the tweeter here, however if Revel did round the corners for the benefit of the woofer it would require a huge round like your other examples over due the frequency range the woofer plays in so they chose not to create that aesthetic.

Open baffle works on different principles and as I understand it rounding the edges is a bad idea as you want the waves to collide at the edge in equal amounts as they attempt to wrap around the baffle.

Here is an example of the still pre-imminent open baffle design using contemporary principles. The Linkwitz LX521

He covers the way of these principles in the vast info he published here

1669923406513.png

1669923440156.png
 
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DanielT

DanielT

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None of these are open baffle.
I do design speakers as a hobby so I understand rounding is often a benefit to them when making typical boxed speakers.
The waveguide in the Revel is doing it job and no round over is really going to benefit the tweeter here, however if Revel did round the corners for the benefit of the woofer it would require a huge round like your other examples over due the frequency range the woofer plays in so they chose not to create that aesthetic.

Open baffle works on different principles and as I understand it rounding the edges is a bad idea as you want the waves to collide at the edge in equal amounts as they attempt to wrap around the baffle.

Here is an example of the still pre-imminent open baffle design using contemporary principles. The Linkwitz LX521

He covers the way of these principles in the vast info he published here

View attachment 247140
View attachment 247141
True, it was mostly just to highlight the issue with the size and design of the baffle, to get maximum or good sound out of the tweeters.
I know you know this but others reading might maybe find it interesting,... new knowledge.:)

Linkwitz LX521 you say. Why not.:)

The best speakers I heard were dioples, DIY AMT with neodymium magnets, + DIY amps (see attached pictures).
Too bad Solhaga couldn't fit more bass modules in the trailer but other than that it sounded damn good. :)
(really good bass but with more of Solhaga's bass modules it would have been world class) :


The listening room was not optimal. I think, guess that Solhaga EQ the shit out of his speakers. EQ as far as possible given the condition, but damn it sounded good. :)

Edit:
The most fascinating thing about that video. Looks like there are some listening who aren't even 40 years old. It at a Vintage DIY HiFi fair. Not just old farts like it usually is.:)
 

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Richard G

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An interestingly done product introduction for the SB Audience OB driver.
A classic OB baffle. You can't do much wrong there ;)

Perhaps the driver arrangement on the baffle should be reconsidered. If the reference axis is to be at a height of 100cm (39''), then it would be advisable to arrange the driver vertically asymmetrically - the optimal arrangement can be simulated very easily.

The orange frequency response shows the edge diffraction with a fully symmetrical arrangement on the baffle, in blue the slightly optimized position of the woofer with a reference axis at 100cm (39'') height.
View attachment 246833

The horn could then be integrated into the baffle or possibly placed on top of the baffle (then the woofer would probably have to be even further up).

If one removes the hump around 200Hz, one gets a flat free field FR.
View attachment 246837
Sensitivity is pretty good at 93dB@2,83V. However, an f3=70Hz and f6=51Hz delivers almost no low bass - subwoofer, as said in JC blog post, is a must.

For low bass using a passive crossover, sensitivity must be sacrificed, so that ultimately only 84dB@2,83V or something similar can be achieved.
If you don't want to use a subwoofer, consider using two 15'' woofers per speaker, with the lower woofer crossed earlier - 2.5-way speaker.
Thank you, a very helpful post

Did you do the simulations with VituixCAD?
 
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