Hoping there's a baffles expert around!
I understand that having a large radius on the edges of a baffle reduces diffraction effects. I also understand that the "half space/full space" radiation transition frequencies are related to the distance of a driver from baffle edges (simplification: call it the width of the baffle).
Imagine I have a speaker with a 10" (25cm) wide front baffle, with the vertical edges of the baffle rounded over with a 1/2" (1.27cm) radius. Is the baffle considered to be 25cm wide (with 1.27cm roundovers) or is it considered to be 25 - 2 X 1.27 = ~22.5cm wide?
I ask because I'm wondering about (for various reasons) taking the above speaker, and giving it a much wider roundover - effectively 3.8cm, such that the total baffle width would now be around 30cm wide, but the flat width across the baffle would be the same as before: 30 - 2 x 3.8 = ~22.5cm.
Would this have a significant effect on the response of the system, such that any baffle step correction in the crossover would need to be changed to account for the new baffle width. And if so, for what width?
On the same subject, at what angle should we consider something to be baffle, and when to consider it the sides? A perfect 10cm cube obviously has a 10cm wide baffle, as the sides are at 90 degrees to the front. But what if the sides were at 45 degrees to the baffle? Or 30 degrees with a large roundover? How do you account for this?
I understand that having a large radius on the edges of a baffle reduces diffraction effects. I also understand that the "half space/full space" radiation transition frequencies are related to the distance of a driver from baffle edges (simplification: call it the width of the baffle).
Imagine I have a speaker with a 10" (25cm) wide front baffle, with the vertical edges of the baffle rounded over with a 1/2" (1.27cm) radius. Is the baffle considered to be 25cm wide (with 1.27cm roundovers) or is it considered to be 25 - 2 X 1.27 = ~22.5cm wide?
I ask because I'm wondering about (for various reasons) taking the above speaker, and giving it a much wider roundover - effectively 3.8cm, such that the total baffle width would now be around 30cm wide, but the flat width across the baffle would be the same as before: 30 - 2 x 3.8 = ~22.5cm.
Would this have a significant effect on the response of the system, such that any baffle step correction in the crossover would need to be changed to account for the new baffle width. And if so, for what width?
On the same subject, at what angle should we consider something to be baffle, and when to consider it the sides? A perfect 10cm cube obviously has a 10cm wide baffle, as the sides are at 90 degrees to the front. But what if the sides were at 45 degrees to the baffle? Or 30 degrees with a large roundover? How do you account for this?
I am a rank amateur so consider the following with added sodium:
Skimming through this: Baffle Step Compensation and focusing on the part about a sphere shaped enclosure is very revealing and should help answer the question.
Based on that information, the baffle step loss transitions such that when the wavelength is smaller than the diameter of the sphere, the baffle gain (transition to 2pi space) is fully realized.
Since that works on a sphere, I have to assume that you can treat the full cabinet width as your baffle width regardless of edge treatments.
I could be very wrong 🙂
Eric
Skimming through this: Baffle Step Compensation and focusing on the part about a sphere shaped enclosure is very revealing and should help answer the question.
Based on that information, the baffle step loss transitions such that when the wavelength is smaller than the diameter of the sphere, the baffle gain (transition to 2pi space) is fully realized.
Since that works on a sphere, I have to assume that you can treat the full cabinet width as your baffle width regardless of edge treatments.
I could be very wrong 🙂
Eric
In my simplistic understanding "Half space/full space" radiation transition is a different effect from diffraction, it creates a steady rise from -6 to 0db (or 0 to +6 db depending on the measurement reference). The frequency of the rise is related to the baffle width - so yes, adding wider round-overs will change the frequency at which this rise occurs as some of the round over will count towards the width - perhaps a good estimate is to use half way around the round-over?
Diffraction supplies the wiggles on the frequency response graph. Again I can't tell you how large a radius you need to get rid of it - perhaps someone else can comment. What I can say is the larger the better - the 300mm sphere in the linked page above seemed to be free from these wiggles so this is obviously large enough 🙂
Nick
Diffraction supplies the wiggles on the frequency response graph. Again I can't tell you how large a radius you need to get rid of it - perhaps someone else can comment. What I can say is the larger the better - the 300mm sphere in the linked page above seemed to be free from these wiggles so this is obviously large enough 🙂
Nick
Unless the enclosure is a sphere (or a teardrop), the BS rolloff is not smooth, it will have ripple.
The BS happens at "low frequency". With a baffle of the size the OP is suggesting the waveforms will not even see a 1/2" roundover, so the baffle width remains 25cm.
Even if the round over was 12.5 cm radius, the baffle would still be 25cm -- the transition would be much smoother thou.
dave
Yes, at higher frequencies.
He (sploo) will probably end up with "invisible" speakers...😀😀
And now... a tool (or two) to simulate all of the above:
Home of the Edge
Baffle Diffraction Simulator
Home of the Edge
Baffle Diffraction Simulator
Thanks all for the responses. I've spoken with the original designer, and gist is that extending the baffle width due to having slightly larger round overs wouldn't have a negative affect on the sound, given the existing baffle step compensation.
My motives behind the mod are mostly to experiment with a cabinet with curved walls, but didn't want to mess with the existing crossover, so I was wondering what I could get away with. The mid-bass driver is fairly close to the width of the baffle, so I couldn't flare out the sides (to create curved side panels) without widening the width slightly.
> He (sploo) will probably end up with "invisible" speakers... 😀 😀
Cool idea 🙂. Stealth. Would make them very "wife friendly"
Shaun - I've seen those baffle tools before, but not tried them. Can they simulate the effects of adding (extreme) rounding to the edges of baffles?
My motives behind the mod are mostly to experiment with a cabinet with curved walls, but didn't want to mess with the existing crossover, so I was wondering what I could get away with. The mid-bass driver is fairly close to the width of the baffle, so I couldn't flare out the sides (to create curved side panels) without widening the width slightly.
> He (sploo) will probably end up with "invisible" speakers... 😀 😀
Cool idea 🙂. Stealth. Would make them very "wife friendly"
Shaun - I've seen those baffle tools before, but not tried them. Can they simulate the effects of adding (extreme) rounding to the edges of baffles?
Meaning invisible to your ears not to your wife. The baffle straight edges and "big size" make them more prone to location in space. Nothing is said if the sound is better or not, and this can be very questionable (by other members, that I will not).
Yes. But don't take my word for it. Playing with those tools will give you a feel for roundover radius vs effect. Below a certain radius it won't be worth bothering.
Edit: I just realised that you said "extreme" rounding. I don't know what you mean by this, exactly. I presume you are referring to radius (size) of the rounding.
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When using these programs wondering if there is an optimum baffle design for a wide range driver or is it dependent on so many other variables such as driver , room, etc.
Symetrical or non symetrical placement of driver?
how much rounding of edges? Is large curved depth of baffle at edges better?
Height of baffle over driver vs width?
Irregular shape baffle vs. rectangle?
Is there a consensus on these parameters after more than 10 years of so many efforts in open baffle experimentation?
Symetrical or non symetrical placement of driver?
how much rounding of edges? Is large curved depth of baffle at edges better?
Height of baffle over driver vs width?
Irregular shape baffle vs. rectangle?
Is there a consensus on these parameters after more than 10 years of so many efforts in open baffle experimentation?
Hi,
Planet10's comments are correct and roundovers on a baffle affect the
smoothness of the ripple which is caused by small drivers on larger
baffles, i.e.for a typical 2 way the treble ripple for a 1" dome.
FWIW that ripple is smoothed by also spacing the boundary distances,
0.6:1.0:1.6 or something similar, this applies to a 1" dome or a small
FR in a big baffle, for drivers as big as the baffle there is no choice.
For FR or widerange drivers its basically nonsense, as off-axis response
is so poor there is nothing to smooth with large edge radii unless as I
said the driver is small compared to the baffle dimensions.
FWIW also, waveguides for OB treble units largely remove edge effects,
and flat OB's do have the worst edge effects of any speaker type.
rgds, sreten.
Planet10's comments are correct and roundovers on a baffle affect the
smoothness of the ripple which is caused by small drivers on larger
baffles, i.e.for a typical 2 way the treble ripple for a 1" dome.
FWIW that ripple is smoothed by also spacing the boundary distances,
0.6:1.0:1.6 or something similar, this applies to a 1" dome or a small
FR in a big baffle, for drivers as big as the baffle there is no choice.
For FR or widerange drivers its basically nonsense, as off-axis response
is so poor there is nothing to smooth with large edge radii unless as I
said the driver is small compared to the baffle dimensions.
FWIW also, waveguides for OB treble units largely remove edge effects,
and flat OB's do have the worst edge effects of any speaker type.
rgds, sreten.
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I find large round-overs (we use champhers) really help in reducing the diffraction signature of a speaker and helping it to dissappear as the source of sound (ie helps imaging).
dave
That being a good thing of course, like with waveguides, it's probably my favourite quality of a wide range driver, but there will be lobing and the baffle will still come into play at higher frequencies.
This is a simulation of a small, non-directional radiator that shows: pink - a (very tall) 40cm wide flat baffle, yellow - a 40cm wide baffle made of a 20cm wide flat section and 45 degree wings on either side making up the rest, and blue - just the 20cm flat section without the wings.
Attachments
I find large round-overs (we use champhers) really help in reducing the diffraction signature of a speaker and helping it to dissappear as the source of sound (ie helps imaging).
dave
Hi,
Yes but in your example the driver is not taking up most of the baffle,
and you have the space for large roundovers / champhers which does
help the diffraction signature for smaller drivers on bigger baffles.
rgds, sreten.
But when the tests were done it was an Alpair 12 in there (ie the big dark wood circle was the rebate for the bigger driver). The swoopy box vrs the classic Golden Ratio version with only a 1/2" champher.
dave
So Sreten if I use the .6, 1.0, 1.6 rule, my Raal tweeter which sits on a ledge on top of my baffle with no baffle around it presently other than its own which is 1.5 inches sides and .75 inch top would ideally have pieces of curved felt sized as follows...
one side of tweeter add 1.5 in. curved felt to existing 1.5 in. flat part for 3in. total
other side add 3.3 in. curved felt to existing 1.5 flat part in for 4.8 in total (representing 1.6)
top part of tweeter add 1 in. curved felt to existing .75 flat part for 1.75 total (to get .6)
Is that what you mean?
one side of tweeter add 1.5 in. curved felt to existing 1.5 in. flat part for 3in. total
other side add 3.3 in. curved felt to existing 1.5 flat part in for 4.8 in total (representing 1.6)
top part of tweeter add 1 in. curved felt to existing .75 flat part for 1.75 total (to get .6)
Is that what you mean?
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