Assuming your ports are approx 16.1(h) x 8cm (w) each, then the equations in post #46 predict a required length of 21.2cm for 37Hz and 170l net box volume.
Thank you again @David Morison
I did the calculations using the formulas in post #46 and for 16.2x10cm ports it is giving me a port length of 30.6cm.
We have to take into account that the volume of the box changes when you change the port, because it is contained inside.
I will check what I have later tonight (I think it's pretty close to that).
I did the calculations using the formulas in post #46 and for 16.2x10cm ports it is giving me a port length of 30.6cm.
We have to take into account that the volume of the box changes when you change the port, because it is contained inside.
I will check what I have later tonight (I think it's pretty close to that).
I did this Excel spreadsheet to help using the formulas for the port length... Hope it helps someone.
Link: https://www.dropbox.com/s/odks2uclc23iea3/Port_calculator_pass_diyaudio.xlsx?dl=0
Link: https://www.dropbox.com/s/odks2uclc23iea3/Port_calculator_pass_diyaudio.xlsx?dl=0
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I ended up adjusting the port once again, now it is bang on 37hz. I’m glad I did it, it sounds much better to my ears 😉
The port is 29cm which is really close to the value the calculations gave me. Thanks once again @David Morison
Now, because the port is so much shorter, I will have to correct my bracing… take a look at the left side of the window brace… it no longer connects to the left side of the box:
The port is 29cm which is really close to the value the calculations gave me. Thanks once again @David Morison
Now, because the port is so much shorter, I will have to correct my bracing… take a look at the left side of the window brace… it no longer connects to the left side of the box:
And now it has some color (black) on it!. Some more coats and it is done, finally...
Finished, minus the front grill...
Some dust on the thing, sorry.
It is on the heavy side for sure, I will need help to carry this thing around.
Some dust on the thing, sorry.
It is on the heavy side for sure, I will need help to carry this thing around.
That is a great looking sub, nice work. What are you planning to do for a grill? The EV style wrap around would look killer but I don't know what luck you would have getting one made to fit.... unless those boxes were built to use the EV grill. I have had custom grills made (pre covid) but I don't know what companies are doing that type of thing anymore,
The front grill is done but I don't have it yet.
Another question I have... What would be an effective (and not to complicated) way of measuring the frequency response of the subwoofer?
I saw an interesting article online that talked about Nearfield and Microfone inside the box methods:
https://audioxpress.com/article/measuring-loudspeaker-low-frequency-response
Any suggestions? I have REW and a calibrated microfone available but never used this tools before.
Another question I have... What would be an effective (and not to complicated) way of measuring the frequency response of the subwoofer?
I saw an interesting article online that talked about Nearfield and Microfone inside the box methods:
https://audioxpress.com/article/measuring-loudspeaker-low-frequency-response
Any suggestions? I have REW and a calibrated microfone available but never used this tools before.
You need to get it outdoors and well away from buildings, and with the mic in the far field you can get an accurate full response measurement with a single sweep. There are lots of variations on exactly how this can be done but I like to mic at 10m with 28.3v to the driver because it can be scaled back to a 1w@1m spec and because it's enough drive signal to be beyond the small signal response of the driver and activate any potential box/grill resonances that you may have to fix.
Indoors you will always be measuring the sub/room combo and that can produce wildly different results depending up the position of the sub and mic in the room.
Indoors you will always be measuring the sub/room combo and that can produce wildly different results depending up the position of the sub and mic in the room.
I tried near field measurements today... but I'm a complete beginner with REW...
I don't know how to add the various measurements together in REW. And I'm not sure if the fase measurement is correct.
I'm using the Umik-1 with its 0º calibration file.
REW file: https://www.dropbox.com/s/6feweyhw8hpi68o/NF_01.mdat?dl=0
Maybe the Outdoors measurements suggested be @conanski would be easier and more reliable?
I don't know how to add the various measurements together in REW. And I'm not sure if the fase measurement is correct.
I'm using the Umik-1 with its 0º calibration file.
REW file: https://www.dropbox.com/s/6feweyhw8hpi68o/NF_01.mdat?dl=0
Maybe the Outdoors measurements suggested be @conanski would be easier and more reliable?
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Outdoors at distance is easier in that you don't have to add together 2 traces, each created by a sound source with different radiating area etc etc.
It's harder in that you have to find a big open space where you can make lots of noise, and have power available for your amp.
For combining the 2 parts of your measurement, Jeff Bagby wrote a well respected paper on it which can be found here: https://app.box.com/s/fefis558wna1d6pd07r3
There is a discussion thread on it here too: https://www.diyaudio.com/community/threads/nearfield-farfield-curve-splicing.249310/
VituixCAD can also combine measurements in its Calculator utility.
It's harder in that you have to find a big open space where you can make lots of noise, and have power available for your amp.
For combining the 2 parts of your measurement, Jeff Bagby wrote a well respected paper on it which can be found here: https://app.box.com/s/fefis558wna1d6pd07r3
There is a discussion thread on it here too: https://www.diyaudio.com/community/threads/nearfield-farfield-curve-splicing.249310/
VituixCAD can also combine measurements in its Calculator utility.