Jims 3 way speaker build

[jimbones]

In the Sim a 3uf cap helps. But the bump is really persistent lol. resistance didnt do much

[jimbones]

yes, in the last measurements i just tuned gating off. Also when I measure the port I assume I put the mic tip flush or just a bit into the opening.(maybe a 1/2 inch)

[rpb]

Id really like the get that woofer response to tail off a bit. In an earlier post (i could not find it) Someone suggested a notch filter. I simmed it and it does look like it may work but I will need to order some parts. What do you think??

I would suggest a close mic on the woofer before deciding on the xo change.

There is another way to reduce the 800hz range. Check with your siim to see how it affects the impedance, etc. This a WAG on the cap value. Add a 2uf cap in parallel with the 5.11 mH coil. This is called a tank filter. A smaller cap moves the notch higher. A bigger cap moves it lower. You may need to add a small amount of resistance in series with the cap to keep impedance amp friendly. Maybe 2 to 4 ohms. If it helps you to get a better measurement for this you can plug the port with a rag. Since the port is close to the woofer, it may be affecting the close mic measurement. Set the gate around 100ms as DeZZar suggests in the previous post. This may be a very narrow notch due to the coil being so large.

[DeZZar]

Your real system bass response is the combination of the port and woofer FRD. Can you attach the files and confirm the inner diameter of the port? Set the gate time to 100ms before you export the FRD on both woofer and port.

[jimbones]

Id really like the get that woofer response to tail off a bit. In an earlier post (i could not find it) Someone suggested a notch filter. I simmed it and it does look like it may work but I will need to order some parts. What do you think??

[rpb]

I don't know. What I would close mic, is the woofer.

For a second measurement, plug the port, and measure again.

[jimbones]

ok no gating, port "correct" I have a 5mh and 82uf on the woofer and it is not enough to get a XO point of about 300hz. Also why does the port look like that? I though it is supposed to be a fairly narrow response centered on the tuning frequency? why whould I be getting high frequency information ??

[a4eaudio]

T...There is no need to process the measurement! Just look at it. It can tell you a lot. Don't use the measurement for any other reason, unless someone points out how to do it. I just want to see the tuning frequency, and woofer roll-off.

Got it! I hadn't followed exactly what the measurements were for and jumped to the conclusion it was for MERGING nearfield, port and farfield.

[rpb]

There's different reasons for doing different things, in different ways. I agree that 1/4" should work well, but I didn't want Jim to hit his woofer. The gating needs to be very long, or possibly no gating at all. I use HOLM. It's easy to extend the gate a long way, so that's what I do. See my post. 172 Looks like I went about 65 meters on that one. There will be a dip at the box tuning frequency. The roll-off will probably be smooth, like mine is. My box is sealed, so there's no dip. There is no need to process the measurement! Just look at it. It can tell you a lot. Don't use the measurement for any other reason, unless someone points out how to do it. I just want to see the tuning frequency, and woofer roll-off.

[jimbones]

all, Hold the phone! In prior posts I had asked about ports (proximity to cabinet etc and port length) Well I cut the port for one speaker and additional inch-1.5 inch so it gives me more room between the padded rear wall and the port. Today I was playing bass heavy material and in one speaker air was coming out of the port and on the other nothing. I am wondering it is being blocked. This coincidentally is the speaker I was making measurements on. I will go and cut the other port so the match and rerun the sweeps. Stay tuned (pun intended)

[DeZZar]

I don't mean fill the cabinet up, I'm just referring to the material you would need to add to tame those box resonances - polyfill top and bottom etc - tuning has to be done with those final quantities in place.

[a4eaudio]

On the plus side, both the baffle step and gating are simply processing of the raw measurement. You shouldn't have to re-measure.

[a4eaudio]

I'm not sure, but I think:

Jeff Bagby's white paper and VituixCAD guide both recommend nearfield at about 1/4".
You need to run your nearfield measurements through a diffraction simulation to remove baffle step. Your farfield measurements would already reflect this, as they were measured in the actual cabinet on the actual baffle.
You do NOT need gating on nearfield (or at least it can be long, like 30 to 50 ms). You're a quarter of an inch away, no room reflections are making it to the microphone for quite a while relative to the primary signal.

[jimbones]

i was about 1/4 to 1/2 inch from cone. I was flush with port opening. I did 2.5 msec gating. We also did other freq tests and it is fairly flat to about 60 then it drops and there is a shelf such that the output at 25hz is the same as 40 hz. there is little "weight" to the music.

[rpb]

That does look odd. Were you playing only one speaker at a time? How close to the woofer was the mic? I'd suggest about 2". Can you do gated, with a long gate time?