If you go the RSS315 path, the HO version looks like it's better for a small box. Even tho EQ can do wonders, I have the distinct impression that using less of it end up sounding better.
I used a pro driver -- SB Acoustics NERO-15SW800 -- in a 3cf sealed box of 18mm BB plywood well braced much like you're planning, with a 24+18mm baffle. Q in the box was ~0.7 and the rolloff began ~80Hz. Didn't use Linkwitz transform. Used REW EQ feature to get F3=30Hz and F6=25Hz. The driver is 96 dB/W and the 1W response is >90 dB even at ~40Hz. Rated 800W AES. Powered it with 600W. I ended up using it only under 50Hz. Crossed higher, I had the subjective impression of "fatness" even though the FR showed it to be flat to 100Hz in the listening area.
PS -- That's a lot of bass potential. Do you need it? (I know, I know: never ask a guy if he really needs more bass.)
I used a pro driver -- SB Acoustics NERO-15SW800 -- in a 3cf sealed box of 18mm BB plywood well braced much like you're planning, with a 24+18mm baffle. Q in the box was ~0.7 and the rolloff began ~80Hz. Didn't use Linkwitz transform. Used REW EQ feature to get F3=30Hz and F6=25Hz. The driver is 96 dB/W and the 1W response is >90 dB even at ~40Hz. Rated 800W AES. Powered it with 600W. I ended up using it only under 50Hz. Crossed higher, I had the subjective impression of "fatness" even though the FR showed it to be flat to 100Hz in the listening area.
PS -- That's a lot of bass potential. Do you need it? (I know, I know: never ask a guy if he really needs more bass.)
I'm mostly interested in how the L-T is supposed to handle group delay. If it can really give me the response of an absurdly large box, it's worth trying.
Likewise, since I'm trying to do so much in such a small (sealed) package, my goal is to overkill the requirements, future proof and turn down from max amplitude.
Nice build, btw.
Likewise, since I'm trying to do so much in such a small (sealed) package, my goal is to overkill the requirements, future proof and turn down from max amplitude.
Nice build, btw.
The 12's fit very comfortably in this box once it's scaled up by 1mm in each direction. That brings the scale up to a 15.5" cube for the imperial system users around here. SB Acoustics builds a massive frame for their subs. The internal difference between the 10s and 12s isn't that significant either, just cutting the braces back an inch at most in every direction to fit. I have a few more choices to make, like final materials and their thickness. I am considering a full 3/4" design with a double thick baffle. It would shave 1/2" or 13mm from the outer edges. I may have to redesign the panels into something I can cut and round over, though the long flat corner cuts are appealing to me.
The RSS315 series is listed as having the exact same dimensions from HF to HO. I think the frames and magnets are all reused. After some more sims, the clear winner is the RSS315HO-44. Dual binding posts give me the most flexibility for wiring, the rated sensitivity is the most accurate to the measurements in the sub-bass region. And the alignment requires the least correction in a small box. 20L/driver yields a ~45hz cabinet resonance, which is fine for music playback. Correcting to get equal output at 30hz and below was always going to be a given in my space. But the HO-44 appears to have a better response with less power than the HF-8. All of these subs seem to dip 6-10dB below their rated sensitivity from 50hz to Fs. I have a hard time assuming the response will match these sims and it's why I keep leaning towards overbuilding, though room gain will probably equalize these issues.
The RSS315 series is listed as having the exact same dimensions from HF to HO. I think the frames and magnets are all reused. After some more sims, the clear winner is the RSS315HO-44. Dual binding posts give me the most flexibility for wiring, the rated sensitivity is the most accurate to the measurements in the sub-bass region. And the alignment requires the least correction in a small box. 20L/driver yields a ~45hz cabinet resonance, which is fine for music playback. Correcting to get equal output at 30hz and below was always going to be a given in my space. But the HO-44 appears to have a better response with less power than the HF-8. All of these subs seem to dip 6-10dB below their rated sensitivity from 50hz to Fs. I have a hard time assuming the response will match these sims and it's why I keep leaning towards overbuilding, though room gain will probably equalize these issues.
Last update for a while (I think). Cabinets redone in 3/4" or 18mm. This is a simpler set of cuts, all butt joints with smaller roundovers. Designed to roll up like a burrito. All cut from the same sheet, it is just as easy to make two subs from the same standard sheet, I can't figure a way to fold it all into a half sheet yet. The internal dimensions are still the same, between 30-40 liters. I have the front baffle fully sunk with a planned roundover on any excess space inside the circle. The driver should screw into the inner baffle and the cross brace.
The final size dips below 15" total in every direction, ~380mm. It should be a mean little package when it's all over.
The final size dips below 15" total in every direction, ~380mm. It should be a mean little package when it's all over.
I just use the free version of Sketchup. I like doing initial models in it because it's easy to manipulate each line, point or panel. Fusion360 is what I would finalize in, but it's been so long since I started learning Autodesk I would actually have to start over. Sketchup can't do curves as cleanly as Fusion, so prints are better off in the pro software.
The benefit of 3D modeling is twofold, I can "test fit" and adjust parts together before cutting them. And I can check any measurement I want against the model for my own sanity once the pieces become real.
I have a few shops in my area where I can rent a CNC wood mill designed for a 4x8 ply/MDF sheet. There are a couple of shops I can buy short term membership with for larger projects.
The last design is simple enough to be made with a router and saw of any kind, given a good protractor and some straight edges. This model is even simpler, circle cuts are full depth, the only complication being the (optional) braces at ~1/4" or 8mm depth.
And I'm not a professional, so thank you. It means a lot.
The benefit of 3D modeling is twofold, I can "test fit" and adjust parts together before cutting them. And I can check any measurement I want against the model for my own sanity once the pieces become real.
I have a few shops in my area where I can rent a CNC wood mill designed for a 4x8 ply/MDF sheet. There are a couple of shops I can buy short term membership with for larger projects.
The last design is simple enough to be made with a router and saw of any kind, given a good protractor and some straight edges. This model is even simpler, circle cuts are full depth, the only complication being the (optional) braces at ~1/4" or 8mm depth.
And I'm not a professional, so thank you. It means a lot.
That's very cool. I need to ramp up my Sketchup skills. Haven't spent enough time with it. Had a chance to learn Adobe Illustrator decades ago when I mastered desktop publishing & Photopshop but somehow never got around to it. Methods in Illustrator, I've heard, are transferrable to most drawing programs including CAD etc... Oh well.
BTW, for a sub it's really best not to use MDF. Baltic Birch plywood is best, and for your box dimensions, even 15mm thickness would be fine with the internal bracing. MDF is heavy but not strong, doesn't have the rigidity of good plywood (read: hardwood plywood). @planet10 (Dave) will tell you MDF delays energy transfer through it, blurring the sound. Might not matter for low transient music but anything percussive will be affected.
BTW, for a sub it's really best not to use MDF. Baltic Birch plywood is best, and for your box dimensions, even 15mm thickness would be fine with the internal bracing. MDF is heavy but not strong, doesn't have the rigidity of good plywood (read: hardwood plywood). @planet10 (Dave) will tell you MDF delays energy transfer through it, blurring the sound. Might not matter for low transient music but anything percussive will be affected.
Autodesk Fusion360 has a totally different workflow to a lot of modeling software. It all starts with 2D sketches and extrusions/shaping of those sketches. Complex lines are just as valid as my protractor perfect angles.
That is not exactly correct about "slow energy transfer". Double the thickness of MDF over plywood will win in every way except not related to audio quality. Final strength and resistance to bending can differ between samples and grades, but "double" MDF thickness is around the thickness where it starts to win over plywood.
Well, if we get the exact numbers of strength, MDF strength * 2 > plywood strength. And you get almost twice heavier cabinet, which is a HUGE advantage also.
Impossible to carry is ergonomics and economy thing, not audio quality
No he is pretty close. But MDF is way heavier, and 2 layers? Given the same stiffness lighter is better, sonically and for your back.b
dave
dave
Over 2x as heavy and heavier is a disadvantage, especially in a push-push woofer.
With a single driver extra mass can help reduce box walk, but i would put it in topnot in the box. And given the active reaction force cancellation is a clever trick that largely eliminates the source of box walk, so heavy no longer serves a purpose.
dave
Your arguments?
Mine: the cone of speaker reacts to panel and to the cabinet in overall. The force of reaction acts in a more detrimental way to the lighter thing. In case of opposed speakers the panel still has the mass. More mass = less reaction from movement of cone.
Newton kinda explained this
Ply, MDF, particle board, there is something religious going on with cabinet building material.
I have my own church, which has it's godspell from quite complicated experiments and measurements, testing materials like already mentioned, also sandwich constructions with any stuff you can think of, including steel ball filled compartements, tiles and tar coatings.
If you analyze this stuff for some time, you will find that very cheap and not even exceptionel heavy constructions will give you 98% of what you can do at any cost, may it be money, work or weight. I don't want to start a war, so I will not elaborate further, but differences are much smaller than some of the crusaiders will ever believe. It is not the material, but how you use it and once you have reached 98% there are only 2% to be gained, even with steel enforced concrete.
The constructions the thread opener has made are quite near to perfect, may he use 15mm ply or 20mm MDF. It is a sub, so many theories about resonating regions are just academic. Just don't let the whole thing contract and expand like a ballon. Give it some kind of wool filling for peace of mind and some virtual extra volume and you are done.
PS and a personal one: Don't ever use a plate amp. They suck, in price and quality a no-no.
I have my own church, which has it's godspell from quite complicated experiments and measurements, testing materials like already mentioned, also sandwich constructions with any stuff you can think of, including steel ball filled compartements, tiles and tar coatings.
If you analyze this stuff for some time, you will find that very cheap and not even exceptionel heavy constructions will give you 98% of what you can do at any cost, may it be money, work or weight. I don't want to start a war, so I will not elaborate further, but differences are much smaller than some of the crusaiders will ever believe. It is not the material, but how you use it and once you have reached 98% there are only 2% to be gained, even with steel enforced concrete.
The constructions the thread opener has made are quite near to perfect, may he use 15mm ply or 20mm MDF. It is a sub, so many theories about resonating regions are just academic. Just don't let the whole thing contract and expand like a ballon. Give it some kind of wool filling for peace of mind and some virtual extra volume and you are done.
PS and a personal one: Don't ever use a plate amp. They suck, in price and quality a no-no.
Which is close to ZERO in a push-push woofer.
0 x <anything> = 0. The math behind the physics is pretty clear.
And what said earlier about box walk. I would put the mass on top, not into the box. A subwoofer box should have (potential) resonances above the pass band of the loudspeaker. Treat the box resonance issues separatly from having sufficient mass to minimize box walk.
dave
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What I’d like to understand better is the impact these changes have on resonance, whether it changes the resonant frequencies of a panel, bracing it through the center, or if it lowers the amplitude of the resonance by reducing the compliance of the panel.
Since we’re talking subwoofers, we’re talking about changing the resonant frequency of each panel by adjusting its compliance, (BB PLY vs MDF) against mass (material thickness/density). Can bracing, damping and selecting materials for a cabinet be explained in this way?
Since we’re talking subwoofers, we’re talking about changing the resonant frequency of each panel by adjusting its compliance, (BB PLY vs MDF) against mass (material thickness/density). Can bracing, damping and selecting materials for a cabinet be explained in this way?