For my small sealed sub project, I settled on a sealed box design of 12"w x 18"h x12"d and a 10" driver from SB Acoustics. Approx 1ft3 /30l of internal volume. I am using as a passive design with an external amp.
I am using 3/4" baltic birch, and routering the ends of the panels to create notches on the side and top panels to maximize glue contact area, eliminate any gaps, and minimize the plywood edge exposed. I plan to add extra 1"x1"xL" blocks inside on all the edges for more panel glue contact to really make a strong seal and joint all the way around. I should have about 1.5in of glued wood along every edge.
For a small box, do I need to worry about extra bracing?
And, I see mixed opinions on adding damping materials on the inside walls/ stuffing in the box. Should I line the walls, add stuffing, or at this small size does it really even matter?
The low pass filter on my amp is set around 100Hz. This is really just for low end extension in my basement music/ 3.1HT setup. Low ceilings in my 1927 house, so I get decent room gain, and I small sub is all I need (and have room for).
I am using 3/4" baltic birch, and routering the ends of the panels to create notches on the side and top panels to maximize glue contact area, eliminate any gaps, and minimize the plywood edge exposed. I plan to add extra 1"x1"xL" blocks inside on all the edges for more panel glue contact to really make a strong seal and joint all the way around. I should have about 1.5in of glued wood along every edge.
For a small box, do I need to worry about extra bracing?
And, I see mixed opinions on adding damping materials on the inside walls/ stuffing in the box. Should I line the walls, add stuffing, or at this small size does it really even matter?
The low pass filter on my amp is set around 100Hz. This is really just for low end extension in my basement music/ 3.1HT setup. Low ceilings in my 1927 house, so I get decent room gain, and I small sub is all I need (and have room for).
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Its not that small… i would probably put 2 braces in that box… a set of vertical braces 90° with one another, one of them bracing the magnet against the rest of the box.
Next time, keep in mind that a pair of woofers mounted push-push can dramatically reduce the boxes vibrational load. Align them just off centre.
dave
Ok. So, what would that be. I tend to get confused on this topic. I abondoned my earlier idea of an M&K style subwoofer because the second woofer only reduced second order harmonic distortion.
The scenario you are recommending: Is that (1) the woofers both mounted with magnets inside the box, on opposite sides, mounted just offcenter? And wire in phase so they both push out at the same time? Or (2) 1 mounted magnet inside, 1 magnet outside, wired out of phase so the cones move in opposite directions with the input signal?
I am up to getting a second driver, just dont quite understand how to install it / wire it up.
I am using the 10″ SW26DBAC76-4. A good shallow 10" that looks amazing when the basket is exposed, so I am totally up for a design that does so.
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Push Push woofer is the real thing.
I build a box and cancellation of vibrations is very obvious.
Calculation is very simple. Calculate 1 woofer in closed cabinet.
Double that volume because you use two drivers.
Ie: One driver like 30 Liter closed, then two drivers like 60 liter.
If you use two drivers then I would build a bit smaller like 50-55 liter and boost a bit with DSP. Smaller cabinet is stronger.
Remember price to pay for boosting is more distortion.
You still need to make the cabinet strong.
IME magnets of drivers don’t need to be too close to each other- obviously should not if drivers have vented pole piece.
I build a box and cancellation of vibrations is very obvious.
Calculation is very simple. Calculate 1 woofer in closed cabinet.
Double that volume because you use two drivers.
Ie: One driver like 30 Liter closed, then two drivers like 60 liter.
If you use two drivers then I would build a bit smaller like 50-55 liter and boost a bit with DSP. Smaller cabinet is stronger.
Remember price to pay for boosting is more distortion.
You still need to make the cabinet strong.
IME magnets of drivers don’t need to be too close to each other- obviously should not if drivers have vented pole piece.
That's correct, for those subwoofers.
What Dave's advocating is something like the B&W PV1 or similar. Drivers mounted on opposite faces of the box, so that the cones are moving in mechanically-opposite directions while being acoustically in-phase.
I'd call it "force cancellation", since the opposing forces from the drivers will cancel each other, so the cabinet exhibits relatively little vibration.
Chris
In theory you would need no damping material in that box.
In practice i like to add thick felt (10 mm) to Walls. Also in subs.
You May experiment with some dense damping material - Fluffy polyester and the like should not be used. Of course you could experiment with What you have at Home for instance dense pillow.
In practice i like to add thick felt (10 mm) to Walls. Also in subs.
You May experiment with some dense damping material - Fluffy polyester and the like should not be used. Of course you could experiment with What you have at Home for instance dense pillow.
I have this scrap bedding topper foam. It is a bit thick tho. If I line the walls with it, does it act to reduce the internal volume, or does it instead increase the "effective volume" to act like a bigger box?
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I ended up with no stuffing. Just the reinforcement on every internal edge. Stained fairly dark with a mix of Black and Crimson Fire gel stain. Wired it up. The SB Acoustics driver is very good for a 10". Very tight. Kickdrums and double bass sound like they should with weight and snap.
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Looks nice!
In my experience, stuffing can be tested by speaking into the empty box, then add the stuffing, and see how much your voice is damped down. I do remember that real wool is the king of stuffing too, perhaps that's changed, but for me it seems to always work well. Not sure how much you need it as you say it sounds good - but if experimenting one day, maybe try a woollen blanket or jumper and see what it does 🙂
In my experience, stuffing can be tested by speaking into the empty box, then add the stuffing, and see how much your voice is damped down. I do remember that real wool is the king of stuffing too, perhaps that's changed, but for me it seems to always work well. Not sure how much you need it as you say it sounds good - but if experimenting one day, maybe try a woollen blanket or jumper and see what it does 🙂
Thanks. I discovered that I definitely have a room null right at 20Hz. I cant really play around with the sub position much, but I have 1 corner that I could explore a bass trap.
Well, I went back and added bracing and some light stuffing. It definitely seems to dig a bit lower now, and I can now hear a bit of 20Hz despite the room null at that freq. So the bracing definitely helps.
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In thoery, decent stuffing like wool adds (slightly) to the effective goemetric volume inside the box.
It does this via a heating as it absorbs the sound, IIRC
It does this via a heating as it absorbs the sound, IIRC
That reminds me... I saved some thick wool stuffing from an Epipen shipment (to keep it cool). I had put some thin and flimsy poly batting in the sub, but I am going to open it back up and try this stuff instead!
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Holy cow!n! I pulled the driver and swapped in the blue wool. You can see below the thin wispy stuffing that was in previously. This blue wool extends the base even deeper. I can now hear the 20Hz test tone, even a rumble at 10Hz. And it hots HARD now on kickdrum.
So, the answer to my very first question is, YES! Bracing and stuffing matter a whole heck of a lot even in this size of a box. (And it pays to be a packrat!)
So, the answer to my very first question is, YES! Bracing and stuffing matter a whole heck of a lot even in this size of a box. (And it pays to be a packrat!)
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Hi,
do you have the box and yourself at the same location in room as before?
Room has much more effect on bass than stuffing in the box. It has more effect on bass than brand of the driver, model of your amplifier and so on, room dominates bass response, at any given location in a a room and it changes per location. If you previously listened at a position with a strong modal peak in the response, it would have masked everything and in general sounds like poo. If you now are at position where there is not such huge peak, the sound is much better.
This is all a good thing, and I hope the stuffing also helps and makes difference. It's just that nothing has such a strong effect in sound, except room 😉
Yes, exact same position. My layout is unfortunately rather constrained...I really only have one place for the sib in my layout, between my center speaker and right speaker.
It is in a finished basement with low ceilings (<7ft) and even lower boxouts around the steam heat pipes that create really weird reflections. Definitely not ideal, but still perfectly fun for watching movies and listening to music.
Mass damping works well.
I spread 1cm of Bitumastic underbody sealant on my smaller speakers and also filled them with pure wool.
They were very dead and non resonant when tapped.
I spread 1cm of Bitumastic underbody sealant on my smaller speakers and also filled them with pure wool.
They were very dead and non resonant when tapped.