What I did:
Took full measurements of my 3 including this Peerless 8" woofer here.
Took near field of woofer
Took near filed of port
Took far field of woofer
Aligned near field measurments SPL to the near field SPL so that I can use the far field measurement for my crossover design (mic never moved between measurement of the other 2 drivers so this should keep the SPL and phase aligned for crossing over purposes)
What I don't get:
1. I kind of understand the giant rise from the port as expected something like that but this seems excessive
2. Why the woofer near field starts to rise up dramatically as well around 100 hz
Is is possible that the port output leaked into the woofer near field measurement? Is is literally about 5 inches below the woofer and this would explain a lot
It is also VERY possible I do not know what I am doing with REW. If so, please let me know. I am very good at following directions and I tried very hard to follow the REW directions to the letter.
One last question..... Do I need to combine both the nearfield woofer and port measurements to accurately crossover the woofer with the mid? I would think the port acts almost as its own driver so its response would need to be added to that of the woofer, yes?
Took full measurements of my 3 including this Peerless 8" woofer here.
Took near field of woofer
Took near filed of port
Took far field of woofer
Aligned near field measurments SPL to the near field SPL so that I can use the far field measurement for my crossover design (mic never moved between measurement of the other 2 drivers so this should keep the SPL and phase aligned for crossing over purposes)
What I don't get:
1. I kind of understand the giant rise from the port as expected something like that but this seems excessive
2. Why the woofer near field starts to rise up dramatically as well around 100 hz
Is is possible that the port output leaked into the woofer near field measurement? Is is literally about 5 inches below the woofer and this would explain a lot
It is also VERY possible I do not know what I am doing with REW. If so, please let me know. I am very good at following directions and I tried very hard to follow the REW directions to the letter.
One last question..... Do I need to combine both the nearfield woofer and port measurements to accurately crossover the woofer with the mid? I would think the port acts almost as its own driver so its response would need to be added to that of the woofer, yes?
Attachments
Last edited:
Where exactly were your nearfield measurements taken? Distance from microphone to woofer cone or dust cap? Distance from microphone to plane of port opening? What diameter is the port?
I was just going to mention that. Nearfield in measurement parlance means almost touching the woofer's dustcap and at or just inside of the port baffle plane.
Dan
Dan
Lacking any driver specs, etc., can only comment that a nearfield measurement of a driver is < ~ 13543"/pi/20 kHz = 0.216" (0.55 cm) and a like amount inside a vent's, horn's, etc., pipe end correction.
.5" inch from the cone of the woofer. The port measurement was taken .5" inch from where the flare of the port begins. The port is 4" in diameter
This is the exact driver
https://www.parts-express.com/Peerless-830667-8-Paper-Cone-SLS-Subwoofer-264-1102?quantity=1
https://www.parts-express.com/Peerless-830667-8-Paper-Cone-SLS-Subwoofer-264-1102?quantity=1
Basics of nearfield technique discussed at link below. It covers several of the things you are seeing and asking about.
Another thing you should be seeing (but aren't in your plot) is a minimum in woofer nearfield output at the port tuning frequency. That leads me to believe your current nearfield measurements aren't great or there's smoothing in the data.
https://audioxpress.com/article/measuring-loudspeaker-low-frequency-response
Another thing you should be seeing (but aren't in your plot) is a minimum in woofer nearfield output at the port tuning frequency. That leads me to believe your current nearfield measurements aren't great or there's smoothing in the data.
https://audioxpress.com/article/measuring-loudspeaker-low-frequency-response
For the greatest accuracy, that's the correct way to do it. But if your port is well behaved, it probably won't have much impact on frequency response where you are likely to cross to a midrange. If the port has resonances, broad output, or other complications, then its contribution to higher frequencies may be more relevant. If it's misbehaving, you should probably fix the port problem instead of trying to incorporate that into the crossover design though.
Last edited:
Matt,
I 3d printed the port. Is it possible it is too thin or it is flexing and that is causing the resonances we see in those higher frequencies?
I 3d printed the port. Is it possible it is too thin or it is flexing and that is causing the resonances we see in those higher frequencies?
Where is the port in relation to the woofer?
What size cabinet is the woofer mounted in? Does it have any stuffing?
It is possible that you got some of the port in your woofer measurement. The port measurement doesn't look abnormal to me but the rise in low frequency from the main driver looks suspicious. It should remain flat.
Modeling that driver shows what could be your problem. It calls for a very large enclosure ported. Plus, a 4" port needs to be 32" long to match the driver characteristics. This woofer has a QTS of .66 which is very high. I would use it in a sealed box. I think your measurements are accurate but your box and port are the problem.
What size cabinet is the woofer mounted in? Does it have any stuffing?
It is possible that you got some of the port in your woofer measurement. The port measurement doesn't look abnormal to me but the rise in low frequency from the main driver looks suspicious. It should remain flat.
Modeling that driver shows what could be your problem. It calls for a very large enclosure ported. Plus, a 4" port needs to be 32" long to match the driver characteristics. This woofer has a QTS of .66 which is very high. I would use it in a sealed box. I think your measurements are accurate but your box and port are the problem.
Last edited:
The enclosure is 3600 in cubed. Increasing the enclosure size didn't help much. The wife acceptance factor dictated the size of the enclosure and I searched for a woofer that would fit said spec. According to Winisd this woofer should have done the trick. I have attached the Winisd file for you to look at if you'd like. All the specs are there
I will attach some pictures so you can see where the port is. Center to center it is 10.5" apart.
I definitely feel like the port is leaking into the driver measurement.
I will attach some pictures so you can see where the port is. Center to center it is 10.5" apart.
I definitely feel like the port is leaking into the driver measurement.
Attachments
Those are beautiful speakers!!!! Nice work. According to my calculation, a 4" port in this enclosure wants to be 24" long with this woofer. So you might have some leakage in the measurements from the port since it's right next to the woofer, but your port is likely too short also, which can cause some problems in the response.
I don't have WinSD so I can't check your file, but other calculators should confirm what I'm saying here. I would try this: Elevate the speaker above the ground to get it away from any coupling from that and then do the near field measurements to see if anything changes. I doubt it will much. Also, how does it sound? Maybe there is a way to incorporate the low end boost into the crossover. It seems fairly smooth so maybe it won't be too bad with how it sounds.
I don't have WinSD so I can't check your file, but other calculators should confirm what I'm saying here. I would try this: Elevate the speaker above the ground to get it away from any coupling from that and then do the near field measurements to see if anything changes. I doubt it will much. Also, how does it sound? Maybe there is a way to incorporate the low end boost into the crossover. It seems fairly smooth so maybe it won't be too bad with how it sounds.
Yes, that is exactly what I am trying to do. I am trying to sum the woofer and the port response into a summed frequency so that they be crossed to mid together in vituixcad.
The issue I am running into right now is that my summed response, which, if you look at the screenshot below clearly shows it as a higher DB than both the woofer and the port(see screenshot), as it should, somehow appears to be lower in SPL when I take a look at the ALL SPL tab (see screenshot)
The issue I am running into right now is that my summed response, which, if you look at the screenshot below clearly shows it as a higher DB than both the woofer and the port(see screenshot), as it should, somehow appears to be lower in SPL when I take a look at the ALL SPL tab (see screenshot)
Attachments
With Qts=0,66 you have to tune the port below Fs to get more flat response.
Check parts-express vented-box recommendation for this driver. I would tune to 30Hz, and box volume may need some reduction too.
Check parts-express vented-box recommendation for this driver. I would tune to 30Hz, and box volume may need some reduction too.
Davor,
I don't have enough space to tune to 30 hz with a 4" port. I can downsize to 3.75" and do that. The port size is on this driver taking the full wattage which it will hardly ever play at. Only to show off to friends for fun.
I don't have enough space to tune to 30 hz with a 4" port. I can downsize to 3.75" and do that. The port size is on this driver taking the full wattage which it will hardly ever play at. Only to show off to friends for fun.
I see what you're talking about here and I'm not sure why it would do that. Is there some sort of offset baked into the summed response? Are the measurements out of polarity from each other? Maybe you could just manually move it up until it looks like it's in line where it should be (obviously that's not very scientific, but it could work). I would just use the near field woofer measurement to cross to the mid and ignore the port measurement. Don't worry about summing it with the port since the port is theoretically just dealing with frequencies well below the mid range driver.
A 4" port would be fine if it was 24" long. A 3" port should be about 13" and would fix the rise below 100Hz.