Yes, close-up stereo dipole where the null of the right "sub" is aimed (usually a bit left) of your LEFT ear.. and the null of the left "sub" is aimed (usually a bit right) of your RIGHT ear. This does however depend on exactly where the null is, with time/phase manipulation the nulls for each sub may not be where you expect them to be. (..you are trying to get a lower pressure basically in-between both ears and particularly in a stereo context if possible, recording-dependent.)
..and the ripole is of course a dipole (..below any "cabinet" resonances). Chances are though that the cardioid was operating as a dipole below 40 Hz. (..about the only way you get "around" that is with an active cardioid w/ two sealed drivers in their own cabinets run back-to-back and delayed to get just the right pattern control for a cardiod.)
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That's because the best location for your bass drivers is not the same as the best location for the midrange and treble.
Such delay is not a requirement for multi subs (even though it could be done passively, it has been done successfully without delay.) The steady state response plays the significant role once below a certain frequency and the room dominates in other ways. The response phase changes things, the modal response does as well. Some even use several subs for specific modes over a narrow band.
How do you do such alignment? Timing of very low frequencies are impossible to measure with mic in small room, so do you do it with higher frequency? Or just by tape measure, or perhaps combination? Or steady state, including room and looking at frequency response?
If I remember mark100 used some clever dirac pulse trick or something
If I remember mark100 used some clever dirac pulse trick or something
Ok, searching finds more, here is one method https://www.audiosciencereview.com/...e-aligning-subwoofer-s-to-mains-how-to.15269/
mark100 wavelet stuff https://www.diyaudio.com/community/...ind-delay-phase-and-polarity-at-xover.370287/
mark100 wavelet stuff https://www.diyaudio.com/community/...ind-delay-phase-and-polarity-at-xover.370287/
Exactly, and that's the "problem" I've been trying to "work around" & try to make as "minimal" a compromise as possible.
My idea was to "exaggerate" the total bass capacity from the front speakers in my DIY, and in this way (even with unfavorable speaker placement) get a really good final result at the listening position.
In a way try to compensates ultimate woofer placement, by "strengthen base capacity"
So instead of assuming in the speaker construction that the bass, mid-range and treble should make up approx. 33.3% each (to get a 100% sound image), the bass "on paper" got 45% so that at the listening position it would still fulfill (its part of the sound image) i.e. 33.3%
And to find really good drivers to put together a really "perfect" speaker, is a "eternal work" just full of compromises.
It also getting even harder when you want to use your woofer up to 340 hz.
I'm crazy, I know
Perhaps you know already, but I'll add as reminder for readers who haven't sunked it in yet that modes are inherent to room and nothing to do with speakers, no matter how much inches in the drivers, which brand and how cheap or expensive price, still the room would have exactly same influence on the sound. Dips and peaks are at same position and as severe as before. All we can do is work with the room, eg. move the (bass) speakers, move the listening position, distribute more bass sources in the room and use DSP if available.
Absolutely right tmuikku, but even small changes in speakerplacement make sometimes BIG differences.
So with a more "bass strong" speaker, you will have a better "chance" to be satisfied at listeningpoint.
My room is relatively acoustically regulated with 25,5 kvm 70mm stonewool with 35mm air behind it ( behind plank wall with different sized gaps), and thick carpet and and thick curtains.
The room is also airtight if i close the door and plugs the ventilation, but the door handle shakes like crasy when i do that, and it feels like the room will implode....earthquake feling
Agreed. I think bass traps in general ...well, don't really do much. And I've built some big ones...
I think your 'active trap' setup is the way to go. I hope someday to be able to try it.
Thanks for bringing it to this thread.
I know StigErik, but total sound quality increases significantly.
And even if it like in my case (have about 22-24 cm through the absorbent and back out in the room again), it only work good up to a certan hz.
The room size etc is "the invisible everything" to good bass possibilities, and it's not always logical.
As we had a lot of discussion here and rarely facts ... I produced some. I have the feeling some here don't do a lot of room measurements and subwoofer integration in a system. It needs plenty of measurements and for sure a delay for speakers to get the crossover perfect. And the easiest way is to invert the sub and do your delay for maximum chancellation - you can do this in any sized room.
So, here are some measurements. 1 Subwoofer, room size 4,8 x 4,4m (my office), Ceiling compeltely treated and one wall with slot absorption. So no real bass absorption.
First graph shows all the measurements in different distances. 5mm in front of the Dustcap is nearfield.
Up to 10cm room influence is small but already to recognise. At 30cm there is clearly room influence, +-3dB. At 1m (still at dustcap height) there is FULL room influence - it doesn't get fuller as that. Frequency response with >+-10dB.
Frequencyresponse at ear level in 1m distance (=sitting next to the woofer) ist actually not bad - but depends on the position in the room. So this was a lucky shot.
Comparison of the close FRs:
30cm and 100cm distance, normalised at 105Hz:
Earlevel (=sitting next to the woofer) compared to nearfield:
So no - in 1m distance is no nearfield for a subwoofer. Also not with big drivers (this was 10") - there is no significant directivity for normal subwoofers.
30cm already show about +-3dB FR variance - which is actually pretty good. So putting the cahssis in the backrest should work.
Way more important factor here seems that a woofer probably plays and interacts with the room more linear at listening position as at the walls! This is easy to measure, it's just a lot of work to do these 50 positions and find the perfect one.
Then get the levels right, get the acoustical cross over right and the search the perfect delay - and you don't hear the subwoofer at all, just great low end.
So, here are some measurements. 1 Subwoofer, room size 4,8 x 4,4m (my office), Ceiling compeltely treated and one wall with slot absorption. So no real bass absorption.
First graph shows all the measurements in different distances. 5mm in front of the Dustcap is nearfield.
Up to 10cm room influence is small but already to recognise. At 30cm there is clearly room influence, +-3dB. At 1m (still at dustcap height) there is FULL room influence - it doesn't get fuller as that
. Frequency response with >+-10dB.Frequencyresponse at ear level in 1m distance (=sitting next to the woofer) ist actually not bad - but depends on the position in the room. So this was a lucky shot.
Comparison of the close FRs:
30cm and 100cm distance, normalised at 105Hz:
Earlevel (=sitting next to the woofer) compared to nearfield:
So no - in 1m distance is no nearfield for a subwoofer. Also not with big drivers (this was 10") - there is no significant directivity for normal subwoofers.
30cm already show about +-3dB FR variance - which is actually pretty good. So putting the cahssis in the backrest should work.
Way more important factor here seems that a woofer probably plays and interacts with the room more linear at listening position as at the walls! This is easy to measure, it's just a lot of work to do these 50 positions and find the perfect one.
Then get the levels right, get the acoustical cross over right and the search the perfect delay - and you don't hear the subwoofer at all, just great low end.
Interesting lamJF
Had to do a random sweep with the microfone not in good place ca 1,5 meter from speaker little aside( my daughter and 4 of her friends was around in the room and prepared sleepover) but anyway.
Always interesting to try to "understand" things
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@jawen - about 25dB from lowest to highest. That's not unusual in untreated rooms.
Did you measure both speakers at the same time? Try to do R, L and R+L.
Here is a measurement of my main system.
LF raises 3-4dB to have a little more fun and there are still some combfilters from table and one SBIR. But over all I'm quite happy.
And here the "manufacturers scale" from people who want to sell stuff
Btw - that's already pretty good bass with a singel bass array. But the room is HEAVILY dampened - would not go that far in a normal music room.
Did you measure both speakers at the same time? Try to do R, L and R+L.
Here is a measurement of my main system.
LF raises 3-4dB to have a little more fun and there are still some combfilters from table and one SBIR. But over all I'm quite happy.
And here the "manufacturers scale" from people who want to sell stuff
Btw - that's already pretty good bass with a singel bass array. But the room is HEAVILY dampened - would not go that far in a normal music room.