From my experience asking questions, the port just creates one more complexity in phase. If LF extension is challenging excursion then add more woofers. Don't forget also, fixing Group Delay with DSP, adds more delay to the whole signal.
I would appreciate if somebody could answer point by point for better understanding.
Thanks and Regards,
WonderfulAudio
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Having spatial diversity in that dimension is what gives you control over those modes. People speak of leaving certain things to chance. Who knows, you might get lucky. Go ahead anyway, do some measuring and see how it goes.
The original Summa had ports. But after I went with multiple subs I realized that at best porting was not necessary and it could also be detrimental because of the total lack of cone control below tuning. So I just deleted them. All my subs are closed box.
The bass was clean, cleaner than most monopoles, but still not as good as multiple subs.
I think that it should be advantageous, but not critical. Only one of my subs is a few feet off the floor.
We can, but I am not sure why one would want to do that. In my room, the first mode is at about 22 Hz. Not much point in trying to go lower than that.
You could never do that. One cannot control the phase difference (180 degrees) between the cone and the port with DSP so below tuning the two are just cancelling each other out - no sound to EQ - and trying to do so would just add a lot of excursion with no gain in output.
Hi Earl (@gedlee)
1)Can the corner sub be the one that is lifted? It could be aesthetically more acceptable, the other two subs not so.
2)The multi sub article at https://mehlau.net/audio/multisub_geddes/ recommends adding delay, but you have told delay is not a good idea, am I understanding right?
Thank you,
Warm Regards,
WonderfulAudio
Hi Earl,
Few more relevant questions came to my mind, hope you find time to answer them.
3) It seems like each additional sub we are adding contribute less and less spl, then can we optimize by having 1st sub 12 inch driver, 2nd sub 10 inch and third sub 8 inch driver, each tuned to 25hz (with PRs) just to avoid loss of loading at low frequencies. I am just thinking of saving some real estate if it works. In the city where I live rooms are typically small 🙁
4) If after multi sub approach we move the listening position, the sofa a foot ahead or back(for cleaning the room), do we need to do multi sub tuning again or should the sofa be at exact the same place that we better mark its position on the floor and always keep it there?
5) The multi sub article at https://mehlau.net/audio/multisub_geddes/ uses mp3 for whitenoise, doesn't MP3 format remove quite a lot of frequencies that are required for this multi sub technique?
6) Can we use frequency stepped sweep (from lets say freeware Arta-Steps) instead of whitenoise for this technique? If yes, then is 1/6th octave between 25Hz and 200Hz good enough? We could take just one measurement with linear mic array instead of rotating the mic by hand. There are 2 feet and 4 feet versions available at https://www.shure.com/en-IN/products/microphones/mxa710?variant=MXA710AL-2FT%20
7) Is first room mode always a peak or a null or could be anything?
8) If this technique was done with door closed (almost sealed room) and we then open the door then should this technique be done all over again?
Thank you,
Warm Regards,
WonderfulAudio
Few more relevant questions came to my mind, hope you find time to answer them.
3) It seems like each additional sub we are adding contribute less and less spl, then can we optimize by having 1st sub 12 inch driver, 2nd sub 10 inch and third sub 8 inch driver, each tuned to 25hz (with PRs) just to avoid loss of loading at low frequencies. I am just thinking of saving some real estate if it works. In the city where I live rooms are typically small 🙁
4) If after multi sub approach we move the listening position, the sofa a foot ahead or back(for cleaning the room), do we need to do multi sub tuning again or should the sofa be at exact the same place that we better mark its position on the floor and always keep it there?
5) The multi sub article at https://mehlau.net/audio/multisub_geddes/ uses mp3 for whitenoise, doesn't MP3 format remove quite a lot of frequencies that are required for this multi sub technique?
6) Can we use frequency stepped sweep (from lets say freeware Arta-Steps) instead of whitenoise for this technique? If yes, then is 1/6th octave between 25Hz and 200Hz good enough? We could take just one measurement with linear mic array instead of rotating the mic by hand. There are 2 feet and 4 feet versions available at https://www.shure.com/en-IN/products/microphones/mxa710?variant=MXA710AL-2FT%20
7) Is first room mode always a peak or a null or could be anything?
8) If this technique was done with door closed (almost sealed room) and we then open the door then should this technique be done all over again?
Thank you,
Warm Regards,
WonderfulAudio
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For those that dont know, REW has a nice Room Simulation tab. I guess 8 subwoofer + Main Left and Main Right is sufficient to most.
I dont know how accurate it is, but it is really easy to try ideas and theory from the couch 🙂
For example my room. I like to keep my mains rather close to backwall:
Only mains:
Adding one sub at backwall at midpoint (huge dip at 50 hz is gone)
Adding 3 ms delay (delay added is the same as if plateamp had phase turning knob - Took me some time to realize that):
Adding third sub:
I dont know how accurate it is, but it is really easy to try ideas and theory from the couch 🙂
For example my room. I like to keep my mains rather close to backwall:
Only mains:
Adding one sub at backwall at midpoint (huge dip at 50 hz is gone)
Adding 3 ms delay (delay added is the same as if plateamp had phase turning knob - Took me some time to realize that):
Adding third sub:
Attachments
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It is educational. However straight simulations (in general) tend to give tall peaks calculating on point placement, and real subs can give different results even when you rotate a sub in the same position.
As a result of the uncertainty, any real fine tuning you'd do in a simulator is time better spent measuring.
This is just how SPL combines with ever-smaller increases in Vd. It is not because the additional subs are each moving less air.
Think about this way: adding a second, identical sub increases total Vd by 100%. A third sub 50%. A fourth only 33%. Etc. Turn those incremental changes into dB, and you see small gains after the first 2-3 subs.
All that said, if your room size & SPL needs are modest, then smaller subs can work. Or, if you're trying to improve a specific issue at ~60Hz, a smaller sub can do so without <40Hz extension.