DIY - Sealed Subwoofer's (External powered)..

There was some big improvement in the dip bet 60 - 80 hz, after dropping both the subwoofer height by 20 inches from its first position.. So am thinking to try a measurement with subs in differential heights and check if there could be any further improvement in the dip..

q6TmItI.jpg
Oh btw what are you using to measure?
It is very difficult to measure the sub 100hz region, I am having doubt regarding the accuracy of your measurement instrument. Why don't you try placing the sub of the ground and search for room modes by crawling around the room?(Might sound dumb and weird but try it)
 
Oh btw what are you using to measure?

Am using the mini DSP microphone UMIK-1 - https://www.minidsp.com/products/acoustic-measurement/umik-1 with REW..

It is very difficult to measure the sub 100hz region, I am having doubt regarding the accuracy of your measurement instrument.

This microphone is rated at 20Hz - 20Khz, i use the provided calibration files and this microphone seems to be most used for acoustic measurements across most forums..

Why don't you try placing the sub of the ground and search for room modes by crawling around the room?(Might sound dumb and weird but try it)

Ok.. I will put it from my understanding of room modes.. I use a 80Hz crossover on my AVR..

Below 80Hz, there are 3 room modes per the above chart.. 1st width mode at 40Hz, 1st length mode at 51Hz, 1st height mode at 59 Hz and 2nd width mode at 81hz, just after the crossover..

If i put it on the floor, i need to put them at 1/4th (to minimise 1st width mode at 40Hz), 3/4 (to minimise 2nd width mode at 81hz ) in the room width & 1/2 the length placement in the room (to minimise the 1st length mode at 51Hz).. Am unable to place them on the floor in the right locations as it is a small living room.. But i thought of placing it on ceiling space, which remains unused in a listening room..

Since i used ceiling, i was able to mount them at the right locations as mentioned above..
LiTJWBu.jpg


i also have the liberty to minimise the height room mode (1st height mode at 59 Hz) if i can place the sub at room midpoint between ceiling/floor.. This way, there is all the probability that it will minimise all the room modes below 81Hz in my room, post which i can cross it to mains.. Pic below of what i planned earlier..
rz0gmtp.png


I have suspended the sub from ceiling as much as i can.. The down facing driving on the enclosure is at 44 inches from the ceiling.. If i can have it near 57 inches (midpoint between ceiling/floor), it should minimise all the room modes below 81Hz..

If you look at the above graphs and the room mode chart, 1st width mode at 40Hz, 2nd width mode at 81hz, 1st length mode at 51Hz, is all minimised (almost flat, no peaks).. With the exception being 1st height mode at 59 Hz, which i have minimised to the extent possible..

Had it been a dedicated HT room, i would have placed the subs at 57 inches from ceiling (room height midpoint) on either sides of my listening position and every possibility that i would have minimised all the room modes below 81Hz with two subs..

I still have a minimised peak at 60Hz, have been suggested to use a crossover of 60Hz, so that it is passed on to L/R speaker..
 
Am using the mini DSP microphone UMIK-1 - https://www.minidsp.com/products/acoustic-measurement/umik-1 with REW..



This microphone is rated at 20Hz - 20Khz, i use the provided calibration files and this microphone seems to be most used for acoustic measurements across most forums..



Ok.. I will put it from my understanding of room modes.. I use a 80Hz crossover on my AVR..

Below 80Hz, there are 3 room modes per the above chart.. 1st width mode at 40Hz, 1st length mode at 51Hz, 1st height mode at 59 Hz and 2nd width mode at 81hz, just after the crossover..

If i put it on the floor, i need to put them at 1/4th (to minimise 1st width mode at 40Hz), 3/4 (to minimise 2nd width mode at 81hz ) in the room width & 1/2 the length placement in the room (to minimise the 1st length mode at 51Hz).. Am unable to place them on the floor in the right locations as it is a small living room.. But i thought of placing it on ceiling space, which remains unused in a listening room..

Since i used ceiling, i was able to mount them at the right locations as mentioned above..
LiTJWBu.jpg


i also have the liberty to minimise the height room mode (1st height mode at 59 Hz) if i can place the sub at room midpoint between ceiling/floor.. This way, there is all the probability that it will minimise all the room modes below 81Hz in my room, post which i can cross it to mains.. Pic below of what i planned earlier..
rz0gmtp.png


I have suspended the sub from ceiling as much as i can.. The down facing driving on the enclosure is at 44 inches from the ceiling.. If i can have it near 57 inches (midpoint between ceiling/floor), it should minimise all the room modes below 81Hz..

If you look at the above graphs and the room mode chart, 1st width mode at 40Hz, 2nd width mode at 81hz, 1st length mode at 51Hz, is all minimised (almost flat, no peaks).. With the exception being 1st height mode at 59 Hz, which i have minimised to the extent possible..

Had it been a dedicated HT room, i would have placed the subs at 57 inches from ceiling (room height midpoint) on either sides of my listening position and every possibility that i would have minimised all the room modes below 81Hz with two subs..

I still have a minimised peak at 60Hz, have been suggested to use a crossover of 60Hz, so that it is passed on to L/R speaker..

Sounds good, update what results you get.
 
The earlier two DIY sealed subwoofers which i had in my room + the Sonodyne SPA 202, 2 channel power amp which was used to power the subs, i moved them to my brother, which he is also using it on ceiling..

This time ordered 4 pieces of 12 inch IWAI subwoofer drivers..
JIZN5IM.jpg


Two sealed boxes of the dimension 15 x 15 x 17 (H) were made like before..
IeZl6MN.jpg


Two more sealed boxes of the dimension 8 x 18 x 30 (H) were made..
M6j2l50.jpg


Also picked up an used, faulty Parasound 5 channel power amplifier, of which only 4 channels work, which would be used to power the Quad DIY sealed subs..
x9gt5wM.jpg
 
The earlier two DIY sealed subwoofers which i had in my room + the Sonodyne SPA 202, 2 channel power amp which was used to power the subs, i moved them to my brother, which he is also using it on ceiling..

This time ordered 4 pieces of 12 inch IWAI subwoofer drivers..
JIZN5IM.jpg


Two sealed boxes of the dimension 15 x 15 x 17 (H) were made like before..
IeZl6MN.jpg


Two more sealed boxes of the dimension 8 x 18 x 30 (H) were made..
M6j2l50.jpg


Also picked up an used, faulty Parasound 5 channel power amplifier, of which only 4 channels work, which would be used to power the Quad DIY sealed subs..
x9gt5wM.jpg
pretty exciting :D:D:D

so the two 15 x 15 x 17 subs will hang from the ceiling.
and where are you placing the two 8 x 18 x 30? Behind the screen?
 
pretty exciting :D:D:D

so the two 15 x 15 x 17 subs will hang from the ceiling.

They are fixed to ceiling firmly.. I posted the pics in another thread.. Her is a picture after mounting a pair of subs to ceiling..
nUquCag.jpg


and where are you placing the two 8 x 18 x 30? Behind the screen?

Yes.. Right..

Ht9dBVZ.jpg


The subs on the front wall are hidden behind the screen..

QPXMeWO.jpg
 
Of the 4 subs, i had connected a passive sub to the defunct speaker output of power amplifier :p.. But now, have fixed it..

I had manually dialed the subs (by ear) to my liking by adjusting the gain control on the power amplifier.. Decided to run the Audyssey calibration and noticed that Audyssey sets the sub volume (gain control on the power amplifier) way lower than what i felt was good..

Anyways, post calibration, i bumped the subwoofer levels on the AVR slightly.. Was able to do only 3 point calibration, as full Audyssey calibration wasn't possible as it errored out " Ambient noise is too high".. Will try to redo it later this weekend..

Of the 4 subs, i had placed 2 subs in between the L-C-R and at mid height of the room.. Which is slightly above ear level.. The front stage sounds bigger with action scenes and most surprising thing is am able to feel the sub even in quieter scenes.. Will also try to measure the response..
 
anybody have this particular driver t/s parameters. There website lacs certain values like Sd, Dd..etc
Below is what a FM sent me that was supplied by iWai

"Title: Measured Parameters"
"Method: Fixed-Mmd (161.000 grams)"
"DCR mode: Measure (-0.45 ohms)"
"Area (Sd): 522.79 sq cm"
"QC-limits file: "
"Last setup file: C:\MLS2000\SPO4K.SET modified "
"Series resistance: 75.00 ohms"
"Stimulus level: 1.00 volts"
"SPLref reference impedance: 8 ohms"
"Large units (volume = liters, mass = grams)"
1.230 "RMSE-free Ohms"
25.875 "Fs Hz"
3.261 "Re Ohms[dc]"
51.314 "Res Ohms"
6.911 "Qms "
0.439 "Qes "
0.413 "Qts "
1.078 "L1 mH"
1.262 "L2 mH"
9.550 "R2 Ohms"
0.000 "RMSE-load Ohms"
86.571 "Vas(Sd) liters"
167.763 "Mms(Sd) grams"
225.527 "Cms(Sd) æM/Newton"
14.231 "Bl(Sd) Tesla-M"
91.059 "SPLref(Sd) dB "
0.006 "Rub-index "
 
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