I would also add that when I closed the end after the experiment and made just one reflex port to that end, even that didn't work as well as two ports spread behind the drivers, when I measured the output with different configurations. About half of the output energy was lost. I even tried very different port sizes but the problem and the reduced output remained the same. So, even if many people say you can make a port anywhere in the enclosure, but it's not so at all, sometimes its too far from the furthest of some drivers or there is some internal resonance etc.
They act as a line array in terms of how the phase interacts inside and out, as well as a very restrictive box on the boundaries, causing destructive interferences from way-too-early reflections. A badly made line array also makes destructive interaction instead of constructive, which is defined by the spacing between the drivers.
I assume you experienced comb filtering? Is that what you mean by "only in some narrow frequencies a bit"?
I assume you experienced comb filtering? Is that what you mean by "only in some narrow frequencies a bit"?
The Zd is certainly important, but end loaded is not always best.
Half-way as your second is, is most often seen in an ML-Voigt.
dave
Yes it seems there was some comb filtering in the sound that came out from the open end. I measured the frequency response and it did not boost the bass almost at all, except a bit on the high mid bass area.
The drivers were time aligned to the listening/measuring position, since they were all installed in a straight line and tube was positioned vertically on the floor. Spacing between the drivers was short as possible, as they were in a line side by side. There was nothing wrong on the sound coming from the front of the speaker, just the garbage from the inside was the problem.
Best we can do sim wise is to use the mean of the driver array Vs the cab's harmonic structure unless doing each driver individually and averaging them out with the assumption that both the driver(s), vent(s) are at one or more of these nominal locations:
Z = (L)x ~ 0 (top), 0.217, 0.349, 0.424, 0.561, 0.651, 0.714, 0.848, 0 (bottom)
Z = (L)x ~ 0 (top), 0.217, 0.349, 0.424, 0.561, 0.651, 0.714, 0.848, 0 (bottom)
With time alignment you mean time aligning the exit location placement of the transmission line to the main drivers? Well that I didn't do, I clearly wrote how it is, it's s straight tube, one end open and I gave dimensions. You see the question was:
"Did you time align all the drivers in the tube, to the listening position???"
I was asked about drivers, and not the exit location. Drivers distance from the listening position is equal, all are connected parallel, therefore they are "time aligned".
And if with DSP I would start to change the individual drivers delays, and would sync them optimizing for the exit side only like camplo suggested, then the front wave of the drivers would be messed up to the listening position, wouldn't it? So I don't see that working either. Unless tilting the speaker to some direction and therefore putting some drivers more far away from the listening position would happen to hit some sweet spot.
"Did you time align all the drivers in the tube, to the listening position???"
I was asked about drivers, and not the exit location. Drivers distance from the listening position is equal, all are connected parallel, therefore they are "time aligned".
And if with DSP I would start to change the individual drivers delays, and would sync them optimizing for the exit side only like camplo suggested, then the front wave of the drivers would be messed up to the listening position, wouldn't it? So I don't see that working either. Unless tilting the speaker to some direction and therefore putting some drivers more far away from the listening position would happen to hit some sweet spot.
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Who are you responding to?
Regardless, my response is about trying to align the drivers as a whole to the pipe's harmonics and secondarily the vent(s), so nothing to do with any time alignment per se, though it obviously would impact the delays at the LP since they would be jammed together for minimal ctc spacing.
Regardless, my response is about trying to align the drivers as a whole to the pipe's harmonics and secondarily the vent(s), so nothing to do with any time alignment per se, though it obviously would impact the delays at the LP since they would be jammed together for minimal ctc spacing.
To Camplo or anyone wondering about the alignment.
Yes very true, the pipe harmonics would be the priority. In any case, this experiment was just a stab in the dark since I had the tube and the drivers, to see what happens without any calculations or preparation.
Now I just remembered that I have also another, 10" diameter tube, which is about 8 feet in length and a 6.5" driver. I think I will try that next to get a feel to how this works.
Yes very true, the pipe harmonics would be the priority. In any case, this experiment was just a stab in the dark since I had the tube and the drivers, to see what happens without any calculations or preparation.
Now I just remembered that I have also another, 10" diameter tube, which is about 8 feet in length and a 6.5" driver. I think I will try that next to get a feel to how this works.