As I read it, Earl doesn't say that the diffractions are not visible in a polar map, only that their appearance may be smaller than perhaps anticipated from their audibility, i.e. it may not be obvious from a FR (alone) what is a diffraction and what is not - but for that we have polar maps that help to differentiate that pretty well I think.
We've been over this. Relative smoothness of polars isn't on its own a clear indication that you don't have a problem. The amount of variation could even be inversely proportional to audibility.. you'd have to demonstrate otherwise.
Alright, we have a loudspeaker box with best driver money can buy but the frequency response has ripple to it. Now I roundover the edges with my big router and the ripple is gone, frequency response butter smooth, secondary sound source is gone and there is only single impulse arriving to ear, and sound got worse? I simply cannot see any logic in this, the sound can only get better with ripple reduction, which is reducing secondary sound source amplitude, which must reduce its audibility, what ever that is.
Well I beg to differ then. You would have to show me "a problem" with smooth polars.
Last edited:
That's quite easy, diffraction shows up very well in the off-axis response or a contour plot.
There is no need to compare any simulations with this.
If you understand the underlying principles of diffraction, it already explains itself why this is.
And why any abrupt off-axis issues, are basically all a form of diffraction.
The only tricky part with a wavegeguide, is that the coupling between tweeter (transducer) and the waveguide can be less ideal. Which rather gives local resonances/standing waves or local diffraction as well. (aka acoustic impedance jump)
The same for a irregular waveguide itself, although with modern printing techniques that's a problem from the past.
But in general the frequencies where this happens correspond pretty well with what is theoretically expected.
Last edited:
AllenB claimed that even if the polars are smooth and clean, you can't be sure that there isn't a (strongly audible) diffraction. I don't agree with that (I can't see how could a diffraction leave all the polars unaffected) so I asked how does he recognize the presence of such diffractions if not from a polar map. He insist that a polar map is not enough which I insist to disagree with, so that's it.
Last edited:
That was certainly not my intention and I don't think I twisted anything. I'd more than happy if you corrected it though.
Todays, most of the designs are trading offs with smal front baffle surface with very smooth round edges and look like close : 2 ways + radiator or 3 ways with bass on the sides or bottom... big cubes. Difference is some use WG, others not. All Purifi based.
Brandon's : Purifi woofer + Bliesma ; alternatiive with SBACOUSTICS CAC line (a good idea)
HifiCompass launched (in a country in war and invaded, so bravo) a monitor : same philosophy
there was that monitor they talked a lot at ASR : blesma + Be tweeter in a huge WG
Purifi with the monitor linked in the white paper link some posts above.
Heissman acoustic with Wavecores and cheaper tweeters : how refreshing as well
Large front baffle has disseapared as well as short width front bafles with huge recessed and large bevel surrounds Avalon loudspeaker style ?
I also note the philosophy of high end spreading is not the same between them at redaing Puurifi white paper above. SOme like tweeter off axis to have as much spl than on axis or close (Purifi), some others smooth directivity off axis, some others a last octaves that loose fastly off axis its magnitude not to excite the room !
Now JMF and Allen are talking of large width front bafflee à la Sonus Faber Stradivarius (but still with smooth radius rounded edges) ! Not saying the in between with great Pida member cabinet designs ( but made with pro skilled wood workers) .
Ahaha I am lost ! (ssorry for the off topic, get free please not to answer to not polute Brandon's good thread, but there is a subject than disearve a thread imho for people hesitating.
Brandon's : Purifi woofer + Bliesma ; alternatiive with SBACOUSTICS CAC line (a good idea)
HifiCompass launched (in a country in war and invaded, so bravo) a monitor : same philosophy
there was that monitor they talked a lot at ASR : blesma + Be tweeter in a huge WG
Purifi with the monitor linked in the white paper link some posts above.
Heissman acoustic with Wavecores and cheaper tweeters : how refreshing as well
Large front baffle has disseapared as well as short width front bafles with huge recessed and large bevel surrounds Avalon loudspeaker style ?
I also note the philosophy of high end spreading is not the same between them at redaing Puurifi white paper above. SOme like tweeter off axis to have as much spl than on axis or close (Purifi), some others smooth directivity off axis, some others a last octaves that loose fastly off axis its magnitude not to excite the room !
Now JMF and Allen are talking of large width front bafflee à la Sonus Faber Stradivarius (but still with smooth radius rounded edges) ! Not saying the in between with great Pida member cabinet designs ( but made with pro skilled wood workers) .
Ahaha I am lost ! (ssorry for the off topic, get free please not to answer to not polute Brandon's good thread, but there is a subject than disearve a thread imho for people hesitating.
Yeah its always a compromise, these commercial endeavors need to sell to keep on business, I bet small and slim sells more. DIY is of course possibly to make anything that one fancies. Big baffle has advantage on affecting directivity which can be better, all depending on room and positioning and stuff like that, max SPL requirement. Disadvantage of big speaker is on the looks (to some), difficult to manufacture (some care some don't) and the above debated diffraction stuff which is hard to tell unless someone shows a proper research which would show what is better or worse 🙂 There are many reasons to put big drivers into big boxes, but I cannot currently see good reason why small ones should be on the same box, given all other options open. Sometimes all drivers on rectangular baffle is the ticket but to me it appears like an old bad habbit with no good reason to hold on to, no matter if its big or small.
Since all happens in space and time, even though these forum posts are here to stay, I might change opinion on instant if I ever get to listen to a situation which proves opinions wrong. Listening, and thinking, is key, progress is slow as its a hobby 🙂
Since all happens in space and time, even though these forum posts are here to stay, I might change opinion on instant if I ever get to listen to a situation which proves opinions wrong. Listening, and thinking, is key, progress is slow as its a hobby 🙂
Last edited:
It's possible I think 🤔 on a cnc but yeah the plywood is pretty fragile before glued up I personally wouldn't waste time on it and it's a lot easier to just make a panel for the top and bottom that's rounded with kurfs then trim cut to size since you can match upto a 3 inch radius with a long flush cut bit which is what I would do. If you do try this use a jig saw with a long blade to cut off 90 percent of the overhang on the edges.
Diffraction by definition can be seen as a secondary sound source.
Therefor will always show up as a discrepancy in the off-axis response.
How audible this is, is a totally different story.
One that is also very dependent on context.
I am under the impression that @AllenB was talking about the audibility.
That being said, I don't completely follow why @gedlee said that diffraction effects can't be seen in the off-axis response?
Although I am also missing loads of context here as well, or it's just a misreading.
In a practical environment, I have found the negative effects of diffraction not being on the top priority list to tackle tbh.
Although this really depends how well this has been taken care off (read: what compromises have been made) in the chosen crossover, filtering and overall response of the speaker.
Thanks for that link neutrino_th! Interesting how modeling the cabinet ABEC and prototyping dispersion in VCad has brought me to a speaker that looks almost identical:
Really looking forward to this Brandon!.
I am stuck with bromo (sounds good btw, but a waveguided design should be much better!)
Here is an update on the recent Scanspeak and Satori waveguides. I've added to them to my website now, including the CAD files. We now have 4", 5", and 6" sizes for the Scanspeak 6640 and Satori TW29TX.
Great work @augerpro
Any advance on the speaker design using the marvelous SB Acoustics SB17CAC35-4 + Ceramic SB26???
Cheers
Any advance on the speaker design using the marvelous SB Acoustics SB17CAC35-4 + Ceramic SB26???
Cheers
Sort of. Just to make sure I'm comfortable with the wide ctc idea, I made a new box last week with a minimal ctc and plan to directly compare them, listening to music, next week. If that goes as expected, then I can move forward with voicing and start putting some details out.