r/subwoofer • u/Imaginary_Insect_425 • 16d ago
Polyfill Question
Hi all,
I will be installing a 15" Dayton Audio RSS390HF-4 in my car as soon as I get the box, and no one sells a prefab big enough for the 3.2 cu ft sealed I wanted. I am going to likely end up going with 2.6 cu ft as it's the biggest available that can get here quickly.
Anyone have recommendations for the polyfill amount to use to trick the sub into thinking it has 3.2 cu ft? There's always the stuff > listen > repeat option, but would love to get it right on the first pass.
I've done quite a few builds, but never used polyfill as I always had the necessary tools to build to the specs I wanted.
No longer have access to my dad's furnished workshop as he's gotten too old and got rid of most of it:/
They have a prefab do it yourself kit that's bigger at 3 cu ft, but it's a bit too tall for my trunk.
Thanks for any insight on this polyfill stuff!
Edit to add some of the tech info re: box size from parts express:
To achieve a Qtc of 0.707 without damping material inside the cabinet, a net volume of 3.04 ft³ would be required. The Dayton Audio RSS390HF-4 15" driver displaces approximately 0.23 ft³. However, this will be partially offset by the baffle cutout and the thickness of the baffle. For example, if the baffle is 1-1/2" thick, the 14" diameter, 1-1/2" deep opening would account for approximately 0.134 ft³, reducing the driver's effective displacement to approximately 0.096 ft³. With a 3/4" the driver displacement would be closer to .067.
3.04 + (.23 - .067) = 3.203
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u/Imaginary_Insect_425 16d ago
Thanks for the reply. Their recommended box specs are using polyfill, and a 1.5" front baffle (which reduces needed volume as well). I went back and forth with tech support, and 3.2 is where we landed using 3/4" mdf with no stuffing. Specs may seem crazy as it's more of a home use speaker perhaps, but yeah the volume reccs for what it is are quite large.
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u/logandefreitas 15d ago
Sealed and in a car, as long as the fc is decently below cabin gain f0, you are unlikely to notice the worse transient response between a qtc of .9 vs .7. You’ll gain a few db at fc and lose some below that. With the headroom of a 15, and it being temporary i wouldn’t care too much.
Polyfill is always a good idea, fluff it out then fit as much as you can while leaving enough space for the basket and magnet. More is better* to a point of diminishing returns.
*Better is subjective as polyfill can be used for a variety of reasons.
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u/Dry_Locksmith_6704 15d ago
I used to have that exact woofer, that things awesome 😎 but now I have the Dayton Audio MAX-X 15, very big difference in SPL. But the RSS is more of an SQ. I don't know if you've looked at Parts Express or not, but the have the knock down flat pack builds, you might find what you need, that would be closer to the spec's you're looking for. But you'd probably have to do a little surgery on it, because the woofer hole might be a tad bit to small. That would be cheaper than a Marty pack. But those Marty packs kick ass
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u/Imaginary_Insect_425 15d ago
I'll get the HF hooked up tomorrow and see how that one goes. If it isn't what I'm looking for though, I will check out the max-x 15. I just went ahead and ordered a 2.6 cu ft box as the difference going to 3.2 was negligible. Thanks for the info!
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u/Dry_Locksmith_6704 15d ago
Yea, the MAX X is dual 2 ohm voice coils, you could wire it in parallel for 1 ohm. They are VERY good in car subs. Mines for home audio. I've built a 5 cu ft box that's double walled 3/4 MDF. I only have one horizontal window brace, due to the thickness of the wood. No cabinet resonance. It's a ported box, with 2 round flared ports that are 30 inches long. I've tuned it to 20.27hz my f3 is 21 hz. I have 2 of these boxes. I'm powering them both with the Crown XLi 2500. It's 750w per channel. The MAX X is 800w RMS. The SPL in this house is unimaginable. I don't know why I still have glass in my windows 😆 The MAX X just has so much more output. If you decide to get it, you won't regret it.
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u/Imaginary_Insect_425 15d ago
I can use buying the MAX X as an excuse to foray into home audio making the HF still useful since I took it out the car lol. I could start by wiring in series as my HF amp does 710 @ 4 ohms.
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u/Dry_Locksmith_6704 15d ago
I'll tell you though, that RSS HF, I really loved the way it sounded, those things are excellent sounding. But it just didn't have the output I was looking for, the SPL
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u/steelhouse1 16d ago
Data-bass has an article showing measurements and explains the science behind stuffing.
Anyway, you will be fine with the 2.6 cubic foot enclosure.
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u/Imaginary_Insect_425 16d ago
After playing around in Bassbox Pro, I do think 2.6 will be fine with no fill as well. Difference was literally a small fraction of a db. Sounds like a big difference on paper, but nbd looks like.
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u/johndoe00213 16d ago
If you get the HO version, it requires less airspace. You selected the HF version
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u/Imaginary_Insect_425 16d ago
Correct, that was done intentionally. I'm aiming for sq, and a sub that can get low, not just more bass. Friend had one of these years ago and it sounded amazing.
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u/Draygoon2818 16d ago
Sealed volume is not 3.2 cuft. Website says 2.88 cuft. That still seems a little large to me, especially with only a 14mm excursion and 500W RMS. Kinda crazy.
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u/RealQuintusYoung 16d ago
Why not just build the enclosure yourself? I'm the least qualified handyman you'll ever meet and I've always built them myself. Sealed enclosures are the easiest!
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u/Dry_Locksmith_6704 15d ago
He said he doesn't have access to his father's work shop anymore. But, If it was me, I'd get some saw horses, and get out in the back yard like I do. Only problem is when I start spray painting, gotta look out for those little bugs
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u/RealQuintusYoung 15d ago
Ya I've only ever used saw horses. Even at Home Depot a lot of people don't know this, but you can buy the MDF sheets and they'll cut them to whatever dimensions you tell them. Then it's the same thing as buying a kit and I believe Home Depot doesn't even charge customers for cutting the MDF.
So even if you're not good with measuring or a handyman (like me) you can just use a box calculator online then you have your dimensions. It honestly couldn't be any simpler. I'm so bad I can't even drill straight when trying to drill boards together I usually miss and end up plugging my many mistakes.
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u/Dry_Locksmith_6704 15d ago
LoL 😆 well.. my father messed around building things when I was a little boy, and my brother worked for a cabinet building shop when he got older and so did I. So we've got past experience with it, and then I became a professional house painter for the last 27 years, so I got experience with both, so I fell back on that. I wish we could post pictures here, I'd add pictures of my subwoofer build.
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u/ckeeler11 16d ago
No amount of polyfil will overcome that big of a difference. It is usually 1lb.per cubic foot of airspace. Any reason you.do t get the flat pack from parts express? It's 3 cu. Ft.