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Multi-Way Conventional loudspeakers with crossovers

Baffle Diffraction
Baffle Diffraction
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Old 8th January 2018, 10:52 AM   #11
Juhazi is online now Juhazi  Finland
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One very reasonable solution is to use a wide and curved baffle, like in late Sonus Faber Stradivari, now ceased in production Sonus Faber Stradivari Homage loudspeaker Measurements | Stereophile.com


WE have at least two published diy-copies of it, from Troels and kimmosto! "Poor Man's Strad"
Click the image to open in full size.
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Old 8th January 2018, 10:57 AM   #12
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by Oneminde View Post
instead of a hard and flat surface
I don't think so. You have to define the issue..

Sound begins radiating into some portion of space, eg a flat baffle is half space. Without control it would try to fill full space. Without adequate control, it will do some spreading once the baffle runs out.

First question - how much of this space do you want it to radiate into.
Second question - how much control do you need to keep certain frequencies going this way.
Third question - what can I do when the baffle is already as big as I want to allow in my room.

By rounding the baffle you give the waves something to (partially) follow so the diffraction happens gradually.. but by using absorbing material on the baffle you are doing almost the same thing through different means.

If you get the sound to ride the baffle correctly from the start (and this is critical), then the best move is either a continuation of that baffle or a careful easement. If there is an interruption at some point, like a tweeter faceplate or an non-ideal horn profile or a step, then maybe some absorption could be used to reduce the error.
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Old 8th January 2018, 11:13 AM   #13
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by Oneminde View Post
Ideally, there is only direct sound. Ideally we listen only to the recording without reflective sound being added
That is an approach, whether it is ideal is another question, particularly when you realise it's impossible. If that is your goal, why don't you just listen on headphones and be done with it?
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Old 8th January 2018, 11:24 AM   #14
AllenB is offline AllenB  Australia
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Originally Posted by TMM View Post
If the sound propagating from the edge of the baffle towards the listener is much attenuated compared to the sound coming directly
Additionally, lower frequencies will diffract more wholly as the baffle becomes acoustically small and higher frequencies will be more independent. The larger the baffle the lower the frequency that this will begin possibly lower than perception makes it an issue. The same argument might be made in reverse WRT narrow baffles although it is difficult to make one small enough, especially faced with the flat faceplate of a dome tweeter which limits options.
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Old 8th January 2018, 01:57 PM   #15
Juhazi is online now Juhazi  Finland
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Quote:
Originally Posted by kimmosto View Post
..but the result is very wrong - such as with The Edge. Both have diffraction model which is valid for axial response, about +/-15 deg. window. Please try to remember this while advertising quick & dirty tools.
As far as I know (I am not an engineer or scientist) every simulation is imperfect. This kind on simple, quick&dirty programs eg. assume that panel is flat, driver membrane is flat, flush mounted and response constant. The result/response given is obviously not reliable or valid enough to be used in a loudspeaker simulation software. But these will easily and quickly give the user some idea about the phenomenom discussed.

It is up to the anyone to personally decide what programs (s)he uses and trusts, but anyway I have found these to be very easy, educative and reasonably reliable for general "tinkering" of baffle diffraction. That's why I repeatedly recommend The Edge. Anyone with some measuring system can check the validity of these personally. Then we must remember the difficulties and caveats of making measurements at home...
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Last edited by Juhazi; 8th January 2018 at 02:02 PM.
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Old 8th January 2018, 04:11 PM   #16
kimmosto is offline kimmosto  Finland
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Quote:
Originally Posted by Juhazi View Post
It is up to the anyone to personally decide what programs (s)he uses and trusts, but anyway I have found these to be very easy, educative and reasonably reliable for general "tinkering" of baffle diffraction. That's why I repeatedly recommend The Edge. Anyone with some measuring system can check the validity of these personally.
The problem is off-axis and directivity in general. You have advertised several years and times Edge also for that purpose. It's quite clear that Edge is not designed for off-axis, but that doesn't stop you. Now you mentioned BDBS up to 89 deg, though error is as obvious to high off-axis.
I'm painfully aware that fully accurate diffraction simulator does not exist, but better app(s) for off-axis and directivity should be quite easy to find.
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Old 8th January 2018, 05:40 PM   #17
Oneminde is offline Oneminde
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Thanks guy's for all the reply's, just as a I wanted.

One even mentioned headphones. Sure, headphones are great, but imaging or experience of space is extremely difficult. Even the Focal Utopia's have issues.

To clarify better what I was initially going for. Room acoustic is addressed with different traps and one of these are Acoustic Panels which comes in different flavors such as: Hard surface w/ holes, slits etc (absorption) and 3D patterns (diffusion) and often with absorption materials behind. Since no one is mentioning these solutions for the baffle, how come not ? What real science exist addressing these and not only shape, driver distance and bevel edges.

Anyone ?
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Old 8th January 2018, 07:21 PM   #18
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by Oneminde View Post
headphones are great, but imaging or experience of space is extremely difficult.
Not really, special delayed crossfeeds can fix that.
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Old 8th January 2018, 07:45 PM   #19
Juhazi is online now Juhazi  Finland
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The baffle must be rigid, that is the most important feature besides shape. Baffle surface material/coating has extremely little influence on sound radiation, I have seen different texture patterns and felt on some commercial and diy speakers, but none serious comparative measurements. Obviously guestion is irrelevant. Google search links mostly to guitar cabinets.

Sound absorbent material on front baffle.

AES E-Library >> The Effect of Commonly Used Baffles on the Sound Dispersion of a Typical Direct Radiator Loudspeaker

US Enclsoure Engineering Solves Diffraction Problems

This was linked earlier, but it is about minimizing edge diffractions with felt strips, not about flush mounted felt on baffle Diffraction Doesn't Have to be a Problem
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Old 8th January 2018, 08:03 PM   #20
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by Oneminde View Post
imaging or experience of space is extremely difficult
<snip>Room acoustic is addressed with different traps
You keep mentioning what you want the baffle not to do, but what do you want it to do for you? Are you going to let it make a mess and fix it with absorption? Do you want imaging or spaciousness or both?
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