Actually, there's only one trade secret of importance, which is the way we optimize the acoustic cardioid. Besides that I will not give you an exact how-to if you wish to copy our design. Pretty much all else I'm happy to discuss.
There indeed is not one "best" way to deal with diffraction, there are several methods to deal with it. Some are better than others. Generally though, I think diffraction does not get the attention is deserves. Minimize rapid diffraction and you'll be rewarded with a smoother frequency response, a cleaner impulse and generally a more consistent frequency response within the listening window.
With a bigger baffle you shift the frequency range where you see diffraction effects downward. In case of the tweeter, you can push the biggest issues down to below its passband. Diffraction issues in the midrange can be pushed to the transition region between the modal range and the range described by ray-acoustics. Those are generally good things.
The Grimm designs sound really superb and I have to admit I've learned a lot from analyzing them. I obviously made a couple of very different design choices, but the LS1 design surely was a big inspiration.
One excellent way to deal with diffraction, I've not seen mentioned here, is to use a minimum amount of baffle. If the membrane is almost as big as the baffle, diffraction is spread out in time and thus its effects are smeared in a very wide frequency range. The result is that there are no clear peaks and dips in the response, and dispersion is smooth. This works really well!
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As shere has (mainly...) one dimension it will generate a strong internal resonance based on that mode.
French manufaturer Elipson used to fight this using an internal helmotz anti resonator.
French manufaturer Elipson used to fight this using an internal helmotz anti resonator.
The problem with minimal baffle/sphere is that you will loose bafflestep reinforcement, which means more stress for the driver in it's lower band. Could be a problem for a midrange in practise. The effect is not as remarkable as with dipoles and cardioids, but exists and might be a challenge for passive crossover design.
Like many have said, edge interferences can be minimized in many ways, each has it's own caveats. One solution has not been mentioned yet - in-wall mounting! We see that in many recording/mixing studios, AV/movie theatres and at some dedicated listening rooms. But even then tweeters remain critical...
SAM™ Master Studio Monitors | Genelec.com
Like many have said, edge interferences can be minimized in many ways, each has it's own caveats. One solution has not been mentioned yet - in-wall mounting! We see that in many recording/mixing studios, AV/movie theatres and at some dedicated listening rooms. But even then tweeters remain critical...
SAM™ Master Studio Monitors | Genelec.com
Those look nice.
Ikea bowls? I'd like to see measurements but I'm not sure what to do or look for to find diffraction. Off axis, maybe?
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It was your project that triggeredmy comment earlier.
... Seems that it would only require some 'objects' inside the cavity to break up the internal mode without fancy anti-resonators.
Juhazi - in wall is low WAF due to the destruction of the wall, especially in houses with real walls made of brick or stone instead of 'cardboard' like my house. Better to make an on-wall speaker perhaps ? We have the Cornu thread for inspiration.
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Or bookshelf... Imo the main problem with the front wall is that it is never accounted for in loudspeaker design...
Allison did an were actually quite room friendly.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Btw most active pro monitors come with several preset low end eqs to account for different boundary effects.
But in audiophile integrist litterature they prefer the most radical solution: off the walls!
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We are now a bit too far from baffle diffractions, but I agree, typical way of setting hifi speakers at home is far from ideal - more like the worst scenario. Compared to edge diffs, first reflections are way more important, and anyone can do something about them! On-wall, bookshelf, in-wall should not be forgotten!
Speaker Placement 101: How to Fight Boundary Interference
Here are nice simulators, REW has similar tool also hunecke.de | Loudspeakers Calculator
hunecke.de | Room Eigenmodes Calculator
and one for a single reflection Floor/Ceiling Reflection Calculator
Here a floor bounce at various IR gating - from same measurement
Speaker Placement 101: How to Fight Boundary Interference
Here are nice simulators, REW has similar tool also hunecke.de | Loudspeakers Calculator
hunecke.de | Room Eigenmodes Calculator
and one for a single reflection Floor/Ceiling Reflection Calculator
Here a floor bounce at various IR gating - from same measurement
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Or bookshelf... Imo the main problem with the front wall is that it is never accounted for in loudspeaker design...
Allison did an were actually quite room friendly.
An externally hosted image should be here but it was not working when we last tested it.
Btw most active pro monitors come with several preset low end eqs to account for different boundary effects.
But in audiophile integrist litterature they prefer the most radical solution: off the walls!
Funny you should mention Roy Allison. I owe huge credit to him, because it was reading about the Allison effect that inspired me to incorporate boundary coupled subwoofers in the 8c. It works really well!
A Tribute to Roy F. Allison (1927-2016) | Audioholics
for starting,I do not want to put too much meat on fire..
measuring have some limits, the microphone
not work exactly like our brain.
if during reproduction you have lost informations space/time,
the microphone of measure will not know.
We need to reconsider a bit the description how the sound work and especially how our brain perceive and elaborate the sound.
i think that we are bogged down in some old concepts,
in which there is no distinction between the original sound produced by live playing instrument and the same sound when played, again once time the microphone don't know the difference..
Regarding microphones and measurements, i think mikes really allow to make perfect measurements (though maybe not so great recordinds...), the only problem with this being we need to have a clear idea of what measurements do we need and what for.
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If on wall mountng greatly reduces diffraction and also eliminates the baffle step issue for bass dispersion WHY do we have speakers pulled out away from the wall in the first place ????
Because somebody long long time ago had full BSC loudspeakers and it sounded better away from wall. The rest is history.....
Also, the delayed reflection off a wall 4ft behind gives a nice delayed reflection, adds an illusion of depth. There are other ways to do that, though.