It is a trend but also least amount of diffraction, if you think it through. Small driver on large baffle has diffraction wigle over wide bandwidth. Keep the baffle small and drivers big, in other words as little baffle surface as possible.
Also, the baffle step is easy fix with EQ/crossover, but the wigles you can't EQ without causing more problems.
One more example showing the "bandwidth" I've mentioned multiple times now 🙂 Small driver on large baffle has a lot of wiggle (over wide bandwidth), big driver has no wiggle at all. Attachments demonstrate 43cm square baffle, driver in the middle and 0 degrees reference axis to maximize the effect seen on the SPL graph. Attachments are 1", 3", 6.5", 10" and 15" drivers on the same baffle. You'll see the bandwidth that has diffraction "problems" gets narrower until almost disappears on the 15" driver. Last attachment shows ~6.5" driver on ~6.5" baffle and you see there is no wiggle at all.
This means less baffle surface = edges as close to driver as possible, is better. When the baffle edge is right at the driver edge, the frequencies which don't beam are long enough to not cause diffraction at the edges. Makes sense. Slanted edges / roundovers help to get bigger box and still have baffle "edges" close to the drivers. On a direct radiating multiway speaker there is large and small drivers on same baffle so some tricks must be done to minimize baffle area. Google up the Revel Ultima Salon 2 images, pretty much minimal baffle right there 😉 Pulled up the Revel Salon 2 since it is often mentioned here in the forums due to infamous comparison between Salon 2 and JBL M2 some years back. By the way the M2 also has pretty much a minimum baffle area.
This means less baffle surface = edges as close to driver as possible, is better. When the baffle edge is right at the driver edge, the frequencies which don't beam are long enough to not cause diffraction at the edges. Makes sense. Slanted edges / roundovers help to get bigger box and still have baffle "edges" close to the drivers. On a direct radiating multiway speaker there is large and small drivers on same baffle so some tricks must be done to minimize baffle area. Google up the Revel Ultima Salon 2 images, pretty much minimal baffle right there 😉 Pulled up the Revel Salon 2 since it is often mentioned here in the forums due to infamous comparison between Salon 2 and JBL M2 some years back. By the way the M2 also has pretty much a minimum baffle area.
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Theoretically, if you had a driver which was completely directional (emitted no sound 90 degrees off-axis) then the baffle would have no effect what so ever.
The closer the driver is to a point source (omnidirectional - small dome tweeters typically), the more the baffle edge diffraction comes in to play. This is why it is a good practice to position the tweeter precisely on the baffle (off-centre for smoothest on-axis response) and the woofer can just go wherever it will fit.
Re: 6.5" 2-way speakers with minimally sized baffle. This is probably for two reasons; firstly for aesthetics as most people don't want huge wide monkey coffin looking speaker enclosures, and secondly because the 'ripples' due to edge diffraction will typically occur in the few-kHz range, so a passive crossover can perform double-duty, crossing over and compensating for some edge diffraction ripples at the same time. If a huge baffle was used the ripples would occur down at a few hundred Hz, requiring a dedicated filtering network to achieve flat on-axis response.
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It's possible. You need more than 1m wide baffle for a 100Hz -3dB point: f(3) = 115/W(B) (where W(B) is the baffle width in meters).
But that's just the baffle step loss itself, it not contains the own response of the driver nor your room.
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If i like to stick with a baffle that is rectangular and as wide as the woofer needs it to be, would it be an option to put slits on the side of the mid woofer to keep the large baffle with the properties of a smaller one?
I have seen baffles with slits and holes but i cant find any now. So if someone knows something about that...
I have seen baffles with slits and holes but i cant find any now. So if someone knows something about that...
If you like visually the old school box shaped speakers with sharp corners (like I do *) I'm not sure if there is any other way to manage the diffraction than using waveguide and / or offsetting the drivers so that the listening axis doesn't have the worst diffraction problems 🙂 If ultimate audio performance is appreciated over the visual appeal then use some other shape than shoe box.
Any obstacle will diffract some including all furniture and belongings in the listening room so I'm not sure if this is something one should agonize over. Go with the looks you like and enjoy the sound you get 🙂
* I'd like invisible speakers best. Second best is the oldies shoe box look. Salon 2 and M2 mentioned earlier, cheez. I will probably end up with some freestanding horns that are tucked in corners and camouflaged with wall color. It has been plywood since few years and some years to come, still prototyping 🙂
Any obstacle will diffract some including all furniture and belongings in the listening room so I'm not sure if this is something one should agonize over. Go with the looks you like and enjoy the sound you get 🙂
* I'd like invisible speakers best. Second best is the oldies shoe box look. Salon 2 and M2 mentioned earlier, cheez. I will probably end up with some freestanding horns that are tucked in corners and camouflaged with wall color. It has been plywood since few years and some years to come, still prototyping 🙂
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A direct effect caused by a physically smaller driver being closer to a point source, the larger driver has a greater radiation area and one gets an averaging as a waveform meets the edge excited by a wider range of distances from the source causing plus & minuses in the ripple cancel out yeilding a smoother large scale FR (what we measure). One wonders if that acoustic smearing at the edges causes some low level detail to be lost in the averaging. Consistent with the generalization that smaller drivers do higher frequencies better.
Much better to minimize the issue in the first place, i have found that removing as much of the diffraction signature as possible yields positive benefits.
dave
Right now I'm the fun stages of figuring out what to do, it will not be perfect, intact some chooses are just plain wrong from an engineering perspective, I can only motivate it by curiosity and the fact that I like the looks, 🙂
Martinsson's Blog -
My current idea is a 600mm wide baffle 820mm high, images in the link above.
Martinsson's Blog -
My current idea is a 600mm wide baffle 820mm high, images in the link above.
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planet10: Yep same thing you are talking, small baffle size related to driver size yields the minimum wiggles. Doesn't matter if it is big or small driver as long as the baffle is as small as possible. When driver is small compared to baffle the wiggle is a lot worse.
Go ahead, looks fun project! the 15" driver will limit diffraction effects below ~1kHz. I'd like to think that it is not as bad as having diffraction ripple above the 1kHz. Anyway, having fun is more valuable than worrying about diffraction 🙂 It is quite hard to build such big slanted box though. Prepare some jigs for assembly. I've done one and the gluing wasn't fun 😀 Measurement was slow and needed bulky jig as well.
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Might be, but I couldn't think other case than if the speaker/baffle was flushmounted. The logic: if sound radiates along the baffle it will meet baffle corner before the wall so there is diffraction. Maybe on very low frequencies there isn't as much ripple but if the baffle was narrower there wouldn't be anyway.
You've got large bent on the baffle maybe it helps. I can't simulate or measure that so have no idea how it affects but since small roundovers help some i could think this would as well.
You've got large bent on the baffle maybe it helps. I can't simulate or measure that so have no idea how it affects but since small roundovers help some i could think this would as well.
Alright few more 😀 This time driver size stays same but baffle gets wider. The diffraction starts lower in frequency when baffle gets larger. Upper frequency for the ripple is bound by the driver beaming as in examples before and when the bottom frequency slides down as baffle gets wider the ripple gets wider bandwidth and effects seem to get worse. Edge diffraction is still there even when the baffle is size of a wall, 3m x 2.4m.
Attachments are 8" ideal driver on 82cm tall baffle. Widths are 20cm, 40cm, 60cm and 1000cm. Last one is the 3m wide 2.4m tall baffle and Directivity polar chart is seen underneath the diffraction simulator. The diffraction effects in the listening window are very closely stitched (orange dots on the red area) so maybe the ear isn't sensing them anymore on a large enough baffle? This is silly big though, and lot more artifacts than narrow baffle.
My conclusion based on the diffraction simulator with ideal conditions that wide baffle (compared to driver size) yields worse diffraction effects (more ripple) than narrow baffle. Roundovers and slants seem to help. When baffle is no wider than the driver, no diffraction ripple is seen.
The experiment was purely visual and considers only the diffraction effects I don't know what audible differences there is. It is high probability that less ripple sounds better though. There is lot more to loudspeaker design so wide baffles shouldn't be skipped. Diffraction can be reduced with roundovers and beaming (horns) 😉
Attachments are 8" ideal driver on 82cm tall baffle. Widths are 20cm, 40cm, 60cm and 1000cm. Last one is the 3m wide 2.4m tall baffle and Directivity polar chart is seen underneath the diffraction simulator. The diffraction effects in the listening window are very closely stitched (orange dots on the red area) so maybe the ear isn't sensing them anymore on a large enough baffle? This is silly big though, and lot more artifacts than narrow baffle.
My conclusion based on the diffraction simulator with ideal conditions that wide baffle (compared to driver size) yields worse diffraction effects (more ripple) than narrow baffle. Roundovers and slants seem to help. When baffle is no wider than the driver, no diffraction ripple is seen.
The experiment was purely visual and considers only the diffraction effects I don't know what audible differences there is. It is high probability that less ripple sounds better though. There is lot more to loudspeaker design so wide baffles shouldn't be skipped. Diffraction can be reduced with roundovers and beaming (horns) 😉
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You could play with this, it might help visualise what's happening Ripple Tank Simulation
There's evidence that less ripple equals better imaging due to there not being secondary sources, probably.
There's evidence that less ripple equals better imaging due to there not being secondary sources, probably.
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That is only 2D and no delay possibility?🙂
ripple tank example, edges radiating
The baffle edge becomes a "ring radiator" but with varying delay (if distance from driver to edge varies like in round driver square baffle) and radiates sound all directions. At listening spot (or any spot) this additional source combines with the direct sound and creates the "ripple". All simulations I've posted have been 3m away on axis and the SPL curve would change if axis or distance changes. This is why I think it is easiest to approximate effect of the diffraction from the polar map since it shows many axis. and distance change isn't very large (distance along baffle is small compared to listening distance).
edit. gotta experiment more on the ripple tank
ripple tank example, edges radiating
The baffle edge becomes a "ring radiator" but with varying delay (if distance from driver to edge varies like in round driver square baffle) and radiates sound all directions. At listening spot (or any spot) this additional source combines with the direct sound and creates the "ripple". All simulations I've posted have been 3m away on axis and the SPL curve would change if axis or distance changes. This is why I think it is easiest to approximate effect of the diffraction from the polar map since it shows many axis. and distance change isn't very large (distance along baffle is small compared to listening distance).
edit. gotta experiment more on the ripple tank
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Yes, but you can place shapes and walls anywhere and actually see the diffraction if you adjust the visual parameters, I found it helped to visualise what the actual waves are doing. You can slow the speed so you can see the delay, there is a 3D setting but I haven't played with it. I haven't got a proper computer so limited as to what programs I can use.
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Hello,
Have read some even look for such diffractions there to make the loudspeaker more lively, dynamic.... pyramid shape seems a good bet while a little rounded and large width à la Sonus Faber Stradivari seems to image quite well, trade offs as always ?
Ah what happen about the large width ESLs ???
+1 for the fun 🙂
Scottjoplin, Tried to experiment a bit and couldn't get "diffraction as sound source" effects to appear. Walls and boxes seem to bend the wave around but couldn't get the another sound source nature to appear. I've just discovered the grid scale is in meters and options can change it. Individual sound sources can have delays etc. At some point gotta try more, for now, coffee break over 🙂
Meanwhile here is nice paper which shows a way to visualize loudspeaker edge diffraction https://users.aalto.fi/~ktlokki/Publs/pulkki2003.pdf
Diyiggy, I don't know. My intuition says the diffraction doesn't help since it just is another delayed / smeared sound source and thus it is just degrading what the driver outputs. On the other hand hearing system is quite amazing and might perceive things that can be described with positive adjectives 🙂 Never heard any of the speakers you described so no comments.
Edit: Diyiggy checked out pictures of the speakers and red your post again. Your examples seem to address the diffraction by reducing flat baffle and it seems good thing to do based on the simulations I've posted. Stradivari is similar what Planet10 posted, might work well I don't know, not able to simulate it. ESL don't seem to have baffle at all so not much diffraction ripple is my guess. They beam a lot being such large transducers (see attachment, a lazer beam and not much diffraction).
Meanwhile here is nice paper which shows a way to visualize loudspeaker edge diffraction https://users.aalto.fi/~ktlokki/Publs/pulkki2003.pdf
Diyiggy, I don't know. My intuition says the diffraction doesn't help since it just is another delayed / smeared sound source and thus it is just degrading what the driver outputs. On the other hand hearing system is quite amazing and might perceive things that can be described with positive adjectives 🙂 Never heard any of the speakers you described so no comments.
Edit: Diyiggy checked out pictures of the speakers and red your post again. Your examples seem to address the diffraction by reducing flat baffle and it seems good thing to do based on the simulations I've posted. Stradivari is similar what Planet10 posted, might work well I don't know, not able to simulate it. ESL don't seem to have baffle at all so not much diffraction ripple is my guess. They beam a lot being such large transducers (see attachment, a lazer beam and not much diffraction).
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