Also another thing I noticed from the large wave guide I built. Without a phase plug the response after 9-10k drops off fast on axis. With a little round 5/8th sticker over the grill on the tweeter(cheap man’s phase plug) the response continues out to 15 on axis and even better off axis . If the tweeter has no phase plug in a wave guide a .5” to 5/8” sticker seems to help it in the upper frequencies quite a bit.I think diffraction from the waveguide when the mic is placed directly on-axis to the tweeter. Simply blocking the center point with your thumb makes the dip flatten out. Moving the mic slightly off-axis greatly reduces the severity of the dip.
And since most here won’t go to my page to look, here is a picture of the gloss top. This isn't something you expect from a $170 speaker which I think is a welcome change to the budget market.
That cancellation occurs only with axisymmetric waveguides, the circular waveguide (like in this review) is the worst in this regard. Elliptical or rectangular waveguides don't have that problem.It's not so much that. You do have the typical waveguide cancellation when directly on-axis. This occurs (as you noted before) in practically every waveguided design. The severity changes depending on where the reference axis is (above/below the waveguide vs on-axis). This is also why many manufacturers of waveguide designs (from typical dome tweeter in a waveguide to coaxial designs) recommend the user listen off-axis; typically 10 degrees is the norm.
That dip is too wild to be an axisymmetry waveguide problem. The on axis is a big dip and off axis are actually peak, I think it is break up.That cancellation occurs only with axisymmetric waveguides, the circular waveguide (like in this review) is the worst in this regard. Elliptical or rectangular waveguides don't have that problem.
Here is a response of an elliptical wg on- and off-axis with proper throat termination:
View attachment 171088
Yes, it can be a break-up, or improper dome-to-throat termination.That dip is too wild to be an axisymmetry waveguide problem. The on axis is a big dip and off axis are actually peak, I think it is break up.
or improper dome-to-throat termination.
Does anyone also measure with the ports plugged? I plug most my speakers since ports seem to add too much to frequency after 300hz I don’t want. I use subs anyway I don’t need super low speakers 80-100hz is good to me
I've never heard of "throat termination" but it sounds like a serious condition. I do think it does have to do with the symmetry of the waveguide since a make-shift phase plug does make the problem go away. If I put the UMIK-1 up next to the tweeter less than an inch away on-axis, you see that dip. If I move it a half an inch down the waveguide, it goes away. That narrow dip will be present if you listen on-axis from a distance. I'm sure someone will make a mod of some sort to address it, and that's kind of fun. It kind of reminds me of when people would mod the old ELAC Debut speakers or the Pioneer BS22LR's. I hope someone does it.That's what I was thinking initially. I'm used to seeing diffraction effects at >10kHz and you/we can calculate that based on distance of tweeter center to waveguide. As for the additional peaks/dips, yes, it's possible those are some sort of breakup modes but I'm leaning more toward the actual throat termination.
Would be hard to verify exactly what the cause is without breaking this thing apart and doing individual testing of the tweeter on a baffle by itself. And I don't have time nor desire for that.
Love it.I've also got a lot of stuff here to test.
Love it.
Sorry for Off-Topic:
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I've been meaning to ask...
Are there times where you want to review a speaker, say from someone who's willing to ship the speaker to you for testing, but the cost turns out to be too large for it to be feasible?
In which case, you end up not reviewing that speaker due to lack of $.
Just wanted to hear your thoughts on this scenario.
We really don't deserve you .Well, I paid $430 round trip for @Spocko to send me his Perlisten speakers. (Which he was kind enough to help me recoup $200, though I had already paid for them from his house to mine and was planning to pay it for returning them)
I’ve also bought a lot of stuff myself. $1200 for the 12-inch subs. $88 last week on something. Little bit here and there. It adds up. That’s why I started a Patreon.
But most of the time the person or company sending stuff for me to review takes care of shipping or at least helps.
I always put the port plugs at the very end of ports. You think the internal port length would cause issues with things? I just thought it meant a little more airspace inside the box if it’s at the very end of the portWhen the speaker comes with port plugs then I typically measure both ways. When it doesn't, I might... or might not. Logic being, if it isn't provided then most people aren't going to use a sock or something else to plug the port; they'll just live with it being ported.
However, I actually did plug the port of this speaker and I have the data for that. The problem is that I plugged it from the outside and the port tube is rather long and I didn't get the port plugged all the way down the tube. The data didn't quite make sense so I think the "void" on the inside of the cabinet created by the unsealed portion of the tube might have yielded the wrong result. I'd have to take the waveguide off and plug it from the inside. I *might* do that but I've also got a lot of stuff here to test. And, again, circle back around the logic on that... how many people are going to know to stuff the port all the way down to the end of the inside of the tube?...
That's what I was thinking initially. I'm used to seeing diffraction effects at >10kHz and you/we can calculate that based on distance of tweeter center to waveguide. As for the additional peaks/dips, yes, it's possible those are some sort of breakup modes but I'm leaning more toward the actual throat termination.
Would be hard to verify exactly what the cause is without breaking this thing apart and doing individual testing of the tweeter on a baffle by itself. And I don't have time nor desire for that.