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jr and jhollander. re a port causing serious reflections when nearer the tweeter
I was just looking at this again and it hit me that…so wouldn’t the affects of a 2 1/2 inch port pale somewhat in comparison to a 5 to 7 +/- inch woofer set next to a tweeter (as in a two way)? Or, am I not grasping the difference of reflection vs diffraction ?
Thx
There is an impact due to the woofer, but it doesn't seems as great. The hole for the port has an edge diffraction and the drop out based on the size of the port. Those effect are high in the FR range. Then there are the resonances in the port that are also in the tweeters range. The impact from the woofer are more ripples as it isn't a hole and tended to line up with the edge diffraction in a 2-way I was doing.
You can do these tests yourself with packing tape or blue tape over the woofer and close to the tweeter port.
It's interesting to see some well established manufacturers do things that most of us would never do. Like putting the port beside the tweeter, or inset the baffle to accommodate a flush looking grill, or using 90 degree cabinet edges.
.jhollander
Thx for your reply.
I’m in the process of moving, but I will give it a go and post measurements when I get a chance.
I can knock down one issue a bit > as I’ll be doing a 3 way with the coax (beyma that has a substantial tweeter wave guide) you helped me with (its crossover) a while ago, so less high frequency off the back of the lower crossed (rel to a 2 way) woofer to flow out the port- which is an issue for all front baffle port designs.
I was thinking not only the size of the woofer, but its concavity and movement creating potentially more negative affects... As mentioned, I’ll build a baffle and do some testing- should be interesting.
You'd be surprised to know that many design decisions in commercial speakers are not driven solely by acoustic performance, but by visual elements and marketability. The reality is that most consumers purchase with their eyes, and many can't tell the difference acoustically or don't care, as the performance bar is often to simply be better then the speaker next to it at the store, or better than the TV speakers, bluetooth radio or soundbar they have at home.
Anyway, I personally think most ports are visually detracting elements, so I almost always put them on the back side. The only speaker where I didn't put the ports on the back would be my Bamboozled speaker, and in retrospect if I were doing it again I probably would relocate it to the back side as well. In the photos above, both speakers appear to be intended for use with a grill, so the port location is a bit silly in the first photo, as well the tweeter location is not very exciting either, with the sharp cabinet edges you can expect significant diffraction effects in this one, not a speaker I would recommend based on visual inspection alone.
As far as port vs speaker for diffraction, the port in the photos above are sharp 90 degree edges, where the driver is a rolled, lets say 45 degree edge. The woofer certainly has "some" effect, but not as great. Besides, you have the choice to move the port to the back side, but what are you really going to do about the woofer, it has to be there so you just have to deal with it.
On top of the port being located next to the tweeter, the tweeter appears to be equidistant from the top and both sides which is pretty much a worst case scenario.