Hi all,
I built two 12" subs tuned to 30hz and another two subs tuned to 40hz.
Is there any bad effect if I use all 4 of them for home theater?
Since the subs are tuned to different frequencies, What kind of bass management is needed?
Any suggestions please ....
(see the picture of my sub in the attachments)
I built two 12" subs tuned to 30hz and another two subs tuned to 40hz.
Is there any bad effect if I use all 4 of them for home theater?
Since the subs are tuned to different frequencies, What kind of bass management is needed?
Any suggestions please ....
(see the picture of my sub in the attachments)
Attachments
It will be difficult to get it right, the 40 Hz tune is quite high. The response of these will fall like a cliff below 40Hz. Chances are high that the 40Hz is below the lowest mode of the room (if the room is small) where multiple subs ideally should sum in phase (since there are no modes). This way they share the load, due to the high tune they cant.
Make the width/dia of the ports smaller to get 30Hz tune on those. High pass the mains very shallow at around 100 Hz.
Make the width/dia of the ports smaller to get 30Hz tune on those. High pass the mains very shallow at around 100 Hz.
I don't know what your main speakers are, but if they are small you can use the 40Hz subs to make them full range. Then put the other subs front and rear of the listening position.
But best imo would be to make 4 identical subs.
But best imo would be to make 4 identical subs.
I built these to experiment different drivers and different box tuning.
Finally I ended up with two subs with 30hz and two subs with 40hz 😀😀
As you said, if there is a possibility of phase mismatch, I will build two more subs with 30hz and use the existing 40hz subs in a different room.
Thanks a lot !!
This is interesting!! but my AVR can not drive them as fronts.
I am using 12" FR drivers for fronts and center.
But this is a good idea indeed.
I'm thinking that the JBL reference is to Pro Audio and not home theatre.
I asked the same question several years ago with regard to my own HT application using cheap powered subs and the consensus was that it helped with room modes, ditto with mixing ported and sealed boxes in the same room
I think JBL are concerned with the phase relationship of different subs and this is valid at home or in a live venue. I would recommend identical or near identical subs (yours may be close enough) and use positioning and room correction to get the desired response. I have done this analogue using a simple notch filter to take out the first room node and used DSP to get better tuning
Brian
Brian
The fundamental problem is that it is stupid engineering to play a device that has its basic resonance inside the passband - like pretty much every sub in the world.
At the least, you can strive for some heterogeneity by mixing different subs and different types of locations in the room. The JBL comment was self-serving and written by their marketing department.
B.
At the least, you can strive for some heterogeneity by mixing different subs and different types of locations in the room. The JBL comment was self-serving and written by their marketing department.
B.
Can you elucidate?
I play my subs XO at 80hz Admittedly my tops roll off at ~60 but I haven't actually heard any bad effects to using my subs this high.
Maybe I need more coffee this morning
Todd Welti's/JBL's Sound Field Management software can use different subs and locations. multi-Sub Optimizer software might be able to do it as well. Multiple Subwoofers: Optimize Them With Multi-Sub Optimizer Software
Earl Geddes said he doesn't pay a lot of attention to sub tuning because it's easy to excite room modes down to 20Hz. Your 40Hz subs will work fine at 20Hz in a room.
Because you're designing for a home theater you'll optimize for multiple listening positions. That means you need to use multi-subs, microphone measurements and DSP. There may be other ways to do it but Todd Welti and Geddes are both authorities on small room bass.
Earl Geddes said he doesn't pay a lot of attention to sub tuning because it's easy to excite room modes down to 20Hz. Your 40Hz subs will work fine at 20Hz in a room.
Because you're designing for a home theater you'll optimize for multiple listening positions. That means you need to use multi-subs, microphone measurements and DSP. There may be other ways to do it but Todd Welti and Geddes are both authorities on small room bass.
Yes, I've checked, it's true 🙂 There is plenty of his work available online about multiple subwoofer set up, YouTube videos as well.
A typical cone lower-range driver might be crossed over to cover 100-800 Hz, a nice 3-octave run. And that sounds great and works so well there are few discussions at DIYaudio about such speakers. The system resonance is maybe 70 Hz - so that is mostly outside the passband of the speaker.
For a sub tasked with say 25-100 Hz (an easy 2-octaves), the system resonance might be 30 Hz - right inside the passband.
That's stupid engineering.
B.
Might want to set your sights a bit lower 😉: The Low Frequency Content Thread (films, games, music, etc) - Bass Content - Data-Bass Forums
GM
Since your subs are ported, they won’t work at 20Hz. You must high pass them slightly below port tuning to prevent mechanical damage
Brian
The context is a home theater, a small room. After he looks into Geddes and Welti he might take one of his subs and dedicate it to the first, second, and third modal region. Then he'd use the remaining three subs to tame his bass up to the transition frequency of his room.
Why do you think his 40Hz subs won't be fine at 20Hz?
Why do you think his 40Hz subs won't be fine at 20Hz?
Check the output and come excursion on WinISD. Below port tuning, the output drops very quickly and the one excursion rises very quickly as the port just becomes a hole and the speaker cone is unloaded
I don’t have access to a PC as I am traveling, but google found this: Speaker Response Curves
Brian
- Status
- Not open for further replies.