Subwoofer experiments can be enlightening!

[Dumdum]

See, with sealed you just put the drivers into a cab and stuff works, no potential issues with almost anything and low group delay, for domestic use the simplicity is hard to pass on and if you are going the multisub route lack of output shouldn't be a thing.

I have four tens sealed in my front room, plenty of output to below 20

I will say this, having been an avid user of smaart for years I obviously put a dsp on my avrs sub output and then experimented

Using subs to fill nulls is bonkers if you can use eq to flatten the response and then add more subs in roughly the same location

I tried a single location where I thought they’d work best with two tens in a single 60l cabinet, and then moved the other cabinet around the room to measure the phase compared to the first…

I have read lots of myths and put politely… crap, on the av forums by people who clearly have tried to fill out a single subs output by using a second sub with little or no regard to phase…

I read if you put subs behind you you must reverse the phase, and every one applauds without knowing why

As long as timing is correct and phase matches a sub behind you or anywhere should be in the same polarity as any other sub, if you have to flip phase to get it to fill a null you haven’t set timing correctly for it’s location for the most part, there’s always a way and a method to get it to fill the subs output, but by filling nulls you are costing yourself overall output as you are effectively using a subs output for a narrow band, and not getting 6db of summation I can normally get from a second sub

In my case I ended up with a. Flat response to 80hz +/-1.5-2db, it sounds very good

So don’t take much heed in the guides you see that don’t advocate measuring phase of subs and just using amplitude measurements and placement to overcome a null or two, and stupid rules like you ‘have to’ invert the phase of subs behind you are just wrong for me

 

[Dumdum]

Subs are in the left corner

 

[sarumbear]

It just it seems at a certain point the resonance is completely gone because the excursion is back to sealed levels under the tuning frequency.

As the name implies a resonance happens around a resonance frequency. At that frequency the cone movement is zero (almost zero due to the unavoidable losses) below and above that frequency the driver behaves as if it is by itself.

 

[sarumbear]

See, with sealed you just put the drivers into a cab and stuff works, no potential issues with almost anything and low group delay, for domestic use the simplicity is hard to pass on and if you are going the multisub route lack of output shouldn't be a thing.

Good observation.

 

[Rick Sykora]

It just it seems at a certain point the resonance is completely gone because the excursion is back to sealed levels under the tuning frequency.

It is close, but if the design was optimized for a vented speaker, you are not getting the ideal closed box response. Ofc, depends on how much you seal the port too…

This might help as I showed here: https://www.audiosciencereview.com/...-vented-speaker-impedance.36331/#post-1289357

 

[Rick Sykora]

For more comprehensive look, consider the following VituixCad models of the Purifi 6.5 woofer in a (typical) 14 liter box. First is the vented box. The next image is when you stuff the port significantly. The final one is the same box with the port sealed entirely...



Aside from the changes in the frequency response, you can see the stuffed port is still acting as a port. Notably, this is most obvious when comparing the excursion difference between the stuffed port and sealed boxes.

Hope the helps!

P.S. If you double click on each image, they should open in a new tab and then you can click each tab to more readily compare them.

 

[Jungstar]

This is an excellent video, explaning bass and subwoofers.
And why some speakers works great at some frequencies and not.
Super interesting!

Do you agree about the video.

 

[AdamG]

This thread and video were previously posted. Threads merged.