Does anyone have a different opinion on whether/what/how much acoustic damping should go into a subwoofer box? About to seal this one up & would rather not open/close again. Only opening is through the driver hole.
Looking good 🙂
As others have said, I struggle to find strong arguments for both the "no damping material" and the "use damping material" in a sealed box where the biggest internal dimension is still much smaller than the shortest intended wavelength.
I always add at least some damping to closed box bass sections, but that's because I usually don't build test-boxes for each x-o section before measuring in box FR and performance. So if a system works better with the bass-mid xo at 300-350Hz, more damping usually works better overall IMO.
As others have said, I struggle to find strong arguments for both the "no damping material" and the "use damping material" in a sealed box where the biggest internal dimension is still much smaller than the shortest intended wavelength.
I always add at least some damping to closed box bass sections, but that's because I usually don't build test-boxes for each x-o section before measuring in box FR and performance. So if a system works better with the bass-mid xo at 300-350Hz, more damping usually works better overall IMO.
Right.
The biggest unsupported outer panel is around 10x8", I think. So panel resonances will be many times higher than 120Hz. Knuckle knocking sounds quick, but no ringing. Interestingly, the frequency varies a bit even when the unsupported area of the panel seems identical.
Will measure air resonance of the box tomorrow and try a bit of lambs wool, see if the amplitude lowers. If not, empty it will remain.
The biggest unsupported outer panel is around 10x8", I think. So panel resonances will be many times higher than 120Hz. Knuckle knocking sounds quick, but no ringing. Interestingly, the frequency varies a bit even when the unsupported area of the panel seems identical.
Will measure air resonance of the box tomorrow and try a bit of lambs wool, see if the amplitude lowers. If not, empty it will remain.
So I made an attempt at checking the air resonance in the sub box. Stuck an 8" driver in with UMIK mic, ran sweeps with & without half the box filled with a light wad of wool.
There seemed to be some reduction of spikes, including one around 120Hz, so I just left the wool in there for now.
I was too impatient to add any more wedges to go between the back of the speaker & the braces. I did add a strip of foam to damp the mechanical contact.
The thin rather dense gasket strip provided with the SBA 15SW800 was applied. Holes poked for the bolts. Some of the gasket foam caught in the threads of the bolts & T-nuts, but it wasn't a problem. Bolts tighten by hand to a bit beyond finger-tight.
yellow line: 8" driver (Dayton RSS225) on floor
blue line: 8" driver in bare box
green line: 8" driver in wool box
Test with Dayton DATS v3 showed the Qts dropped about 0.1 compared to when the driver was enclosed by the sonotube. It's now 0.45 compared to 0.54. This probably means the box is bigger; maybe it's the bit of wool inside. Fs is virtually unchanged -- 54Hz.
REW sweeps --
The first sweep was 20-2K with the mic an inch from the dust cap.
2nd sweep 20-2K 1m away with mic on the floor.
3rd sweeo 20-2K 1m, after PEQ (based on REW's auto-EQ) in miniDSP 4x10HD
4th sweep 20-2K 1m, after auto EQ with 80Hz LR4 on miniDSP 4x10HD
5th sweep 20-2K 1 inch, after auto PEQ with 80Hz LR4 on miniDSP 4x10HD
6th sweep 20-2K 1 inch, after manual EQ with 80Hz LR4 on miniDSP 4x10HD
Listening confirmed that my LX521-clones have bass about as deep & extended & powerful as the single SBA Nero-15SW800 in the 2.8cf box. There was an audible benefit with selected heavy bass/drum tracks when the sub was run parallel with 70Hz LR4 low pass.
First day...
There seemed to be some reduction of spikes, including one around 120Hz, so I just left the wool in there for now.
I was too impatient to add any more wedges to go between the back of the speaker & the braces. I did add a strip of foam to damp the mechanical contact.
The thin rather dense gasket strip provided with the SBA 15SW800 was applied. Holes poked for the bolts. Some of the gasket foam caught in the threads of the bolts & T-nuts, but it wasn't a problem. Bolts tighten by hand to a bit beyond finger-tight.
yellow line: 8" driver (Dayton RSS225) on floor
blue line: 8" driver in bare box
green line: 8" driver in wool box
Test with Dayton DATS v3 showed the Qts dropped about 0.1 compared to when the driver was enclosed by the sonotube. It's now 0.45 compared to 0.54. This probably means the box is bigger; maybe it's the bit of wool inside. Fs is virtually unchanged -- 54Hz.
REW sweeps --
The first sweep was 20-2K with the mic an inch from the dust cap.
2nd sweep 20-2K 1m away with mic on the floor.
3rd sweeo 20-2K 1m, after PEQ (based on REW's auto-EQ) in miniDSP 4x10HD
4th sweep 20-2K 1m, after auto EQ with 80Hz LR4 on miniDSP 4x10HD
5th sweep 20-2K 1 inch, after auto PEQ with 80Hz LR4 on miniDSP 4x10HD
6th sweep 20-2K 1 inch, after manual EQ with 80Hz LR4 on miniDSP 4x10HD
Listening confirmed that my LX521-clones have bass about as deep & extended & powerful as the single SBA Nero-15SW800 in the 2.8cf box. There was an audible benefit with selected heavy bass/drum tracks when the sub was run parallel with 70Hz LR4 low pass.
First day...
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Damn dogg! You have some cool projects!! Do you have a thread on your LX(not)521's? What drivers are you using?
😉
LX521 shape for upper baffle, but everything else is slightly different. It's a mix of John K.'s NaO Note II & SL's LX521. "bass bin" is Linkwitz W-frame.
-tweeter: Aurum Cantus AST2560
-high mid: ScanSpeak 10F4424G (re NaO Note)
-low mid: ScanSpeak 22W8534 (re NaO Note)
-bass: 2x SB Acoustics SB29SWNRX-S75
miniDSP 4x10HD -- x@ 120, 1200, 3000 Hz LR4 Lots of PEQ
Buckeye amp -- NC252MP x4 -- 150W x8
Sources: JRiver on PC, Qobuz, Tidal
By far the best speakers I've built, but never heard them outside my studio.
Can't recall if I posted more details here...
You don't happen to have a measurement of the AST2560 in baffle without eq applied? I'm curious because they had a couple of iterations and the lowend response seemed to vary quite a bit.
Does this seem more "impressive" from the perspective of the LX521 clone, or the Nero-15SW800? Either way, it's an interesting comparison.
How much difference do you notice in the texture of the notes, the interaction with the room, and the sense of pressurization (or not)? What happens when you unhook the LX521 bass section and run with the Nero alone?
This is all out of curiosity, of course, and not expecting a universal "better" response! 🙂
Well, since the 4 10" SBA drivers in the LX521 clones have about double the cone area and pretty good Xmax, I expected them to at least match the single Nero-15SW800 sub, and they do. The pressurization of the room isn't that noticeable. Both sound good, but I haven't had enough time to listen, measure, analyze.
See above answer... and I haven't tried the Nero sub w/o the LX521 woofers. Might have to give that a try
A couple days ago, several friend came over to see & hear creations that they hadn't heard yet. Their reaction was that the LX521 by itself has great balance & presentation & bass, and switching to the sub w/o the LX521 bass was not better, probably worse. We tried the sub as an addon coming in at 60Hz LR4, and that made no difference except on tracks where there was bass down low. Then it made a subtle & powerful difference, adding drama and more ambience.
The sub's best showing was when it was brought in at 80Hz to a pair of omnidirectional speakers using 6.5" woofers which are surprisingly good to ~40Hz, even at fairly high volume, say 95 dB. The omnis were well received by themselves, it's really easy to accept their presentation, which seems unusually "natural" for many listeners. But adding the sub totally filled out the sound.
I cleaned up the studio for the first time in who knows how long. One benefit of having guests over, even friends. 😉
Haven't had time to explore this fully, but the box for my sub might be too big. I was shooting for 0.7 Qts but it's measuring 0.54. Gross internal dimensions are 6000 cubic inches -- 3.46 cubic feet. Even if the braces & driver take up a half cubic feet, it's 3cf. Downslope starts around 70Hz. I realized I need nearly 20 dB boost to get -3dB at 25-27 Hz.
Still, I didn't hear signs of overload when driving it hard today with both test signals & music. Didn't check distortion. Not happy about so much boost. Maybe I need to aim for 30Hz/-3dB to reduce the boost. Have to examine more tomorrow.
Sitting on the sub while it's cranking is amusing. I can feel the box panels flexing despite the bracing!
Still, I didn't hear signs of overload when driving it hard today with both test signals & music. Didn't check distortion. Not happy about so much boost. Maybe I need to aim for 30Hz/-3dB to reduce the boost. Have to examine more tomorrow.
Sitting on the sub while it's cranking is amusing. I can feel the box panels flexing despite the bracing!
The best thing with an active sub is the easiness of eq to personal taste and the room. Measured response is very specific to mic placement, so multiple measurements are needed, perhaps averaging. Basically only the lowest and stronges mode peaks should be tamed and xo range set. Spl level is a matter of taste and to some extent music/recording -sensitive choice.
You should try at least different places for the single sub and if you have several of them, distributed setups. https://audioroundtable.com/misc/Welti_Multisub.pdf
You should try at least different places for the single sub and if you have several of them, distributed setups. https://audioroundtable.com/misc/Welti_Multisub.pdf
My main setup is at our living room, so separate sub(s) are not practical. This was one point for making 4-way stereo speakers with sealed subwoofers. I had to go back ten years to find measurements with both speakers playing at same time (mono test sweep) Speaker placement is dictated by esthetic and practical reasons, not by measurements and the room is asymmetrical. Speakers are along the long wall.
Congrats - critically damped - now use LT to get your desired FR and you will be pleased. This is the way to build subs ;-)
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