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Collaborative Crossover HiVi RT1.3WE and Tang Band W6-1721

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  • #46
    You can measure from different distances if you like, but it changes the diffractions effect on the measurement. I see very little reason to get closer than 3 feet, if you are building a 2-way. There is some geometry effect that is probably accounted for in PCD, but maybe not if you are not careful. If I was measuring outdoors, or a big room with very high ceilings, then I'd measure from 6'. Eventually you may end up with the same xo either way.

    Here's an example of an issue when measuring from 16". Draw a picture. Side view of the speaker, and the mic 16" away. Draw a straight line on the woofers axis, and a line from the woofer voice coil to the mic. Now measure, or calculate how many degrees off axis you are measuring the woofer from. The woofer response can change off axis. If you measure from 36", the angle is smaller. This might be no big deal, but it might hide a peak that you want to know about. I make lots of measurements. Some from the woofers axis, if just to take a quick look.

    Also.... I'm used to using HOLM. Below 300hz usually rolls off smoothly due to the gate. I'm not used to using REW, but I believe that in a relatively recent thread someone posted measurements that looked a lot like my HOLM measurements. I forget which thread.

    I like to clearly see the baffle step. Here's an example.. The step starts around 300hz, and stops around 1k.



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    • #47
      rpb a4eaudio I measured the TB responses at both 24 inches and 36 inches with the bass boost off and the results look pretty different between 300 to 500 Hz region. In the graph below, the orange line is measured at 24 inches and the purple line is measured at 36 inches. I have taken 3 measurements for each responses and they look the same.

      Click image for larger version

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      And for easy reference, I will attached a4eaudio's TB responses curve below.
      Click image for larger version

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      • #48
        Zoom in on the impulse, and post the gate setting. To zoom in, highlight a section, and right click. (I think.) Your measurement looks like it includes some room reflections. It should look smoother.

        Another thing you could try is to move the speaker about a foot, maybe two, and remeasure from the same distance. The room reflections should change if they are being picked up in the measurements.

        Might help to post some pictures of the speaker measurement setup showing the speaker, mic, and any items nearby.

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        • #49
          rpb Taking your advice, I adjusted the impulse window to try to eliminate the reflection, here is what I get. Blue-24 inches and brown-36 inches. Still looks pretty different from a4eaudio's curve especially in the lower frequency region (200 Hz to 1.5 kHz). Not sure if the responses below are still strongly affected by reflection because my measuring location is not really a very open place.Click image for larger version  Name:	TB foam 24n36inch-Boostoff-100-Impulse FR.jpg Views:	0 Size:	104.1 KB ID:	1453729

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          • #50
            Did you try any of the suggested x-overs yet? If so, did any sound thin in the bass, or too warm in the mid-bass?

            It looks like your driver as a significant dip at about 1.2k. I will see if I can make a sim that fills in that dip a little. This driver is different than most I use. Looking at the factory data, it looks like a 5dB drop from 300 to 1000hz. That's enough to compensate for baffle step. But, it looks like diffraction is making the peak at 800hz. It's just hard to tell what's going on. A dip at 1.2k is going to sound odd I think.

            Here's a filter to play with.
            Click image for larger version

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            Last edited by rpb; 10-09-2020, 05:18 PM.

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            • #51
              Hello guys, really sad to inform everybody that one of my TB driver blew up yesterday while I was listening to music (happened to be the one I used for measurement). I was listening at a relatively low volume around 25 (maximum is 99 or 100) on my pre-amp, so I really doubt it is due to overload. Now I am seriously wondering are we dealing with a faulty driver right at the beginning. I have contacted PE on this matter and waiting for reply. It might be a sad ending now for this project but it has been a good learning process. Hopefully everything gets sorted out and I can carry on from where I stopped. Have a nice weekend to everyone who has helped in the process. Thank you.

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              • #52
                JamesTan - here is a pic of the inside of the cabinet I constructed and the port. I did not add any lining and the port is very close to 2" inside diameter and 10" long. According to my simulation in WinISD that should be tuned to 44Hz but my measurements suggest the actual tuning is about 53Hz. BUT...I don't think that would really change much above 300Hz.

                When I first got a mic and did measurements I had some pretty weird results that ended up being due to my laptop. I would suggest you post pics of your speaker cabinet inside and out. Take screenshots of REW or whatever program you are using for measurements. There could easily be some default setting somewhere that is messing things up and people here on the forum my notice that and offer advice. And of course, re-measure with the bass-boost turned off and let us know what that does.

                Click image for larger version

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                • #53
                  Hi a4eaudio , just notice your reply (did not get any email notification). Thanks for the photo. The interior of your box seems bigger than mine but it can be due to angle the photo was taken or because I have stuff my box with damping material and it made my box looks smaller. Do you find the base of the TB driver very close to (or almost touching) the pipe? I actually need to turn my pipe at an angle.

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                  • #54
                    Originally posted by JamesTan View Post
                    ...Do you find the base of the TB driver very close to (or almost touching) the pipe? I actually need to turn my pipe at an angle.
                    Yes. I actually planned to re-measure the tweeter with the woofer "ring" removed to see what kinds of diffraction are happening. But without the woofer ring the woofer hits the pipe and can't be attached.

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