Trevm Posted November 4 Posted November 4 Hello. I am looking to fabricate my own outdoor subwoofer. I am thinking result will be something similar to https://avaustralia.com.au/sonance-ps-s83wt-8-70-100v-weatherproof-outdoor-surface-mount-woofer-each/ Woofer to be mounted high up near speakers, not in ground. This will be paired in with my JBL Control T28. Fabrication and weatherproofing etc I have sorted. Looking to use a Daytona 8". Can anyone suggest what box style would be suit this type of area, it won't be sealed. Any other comments from people with experience would be appreciated, I've never made an enclosure for outdoor sub before.
almikel Posted November 10 Posted November 10 On 05/11/2024 at 6:44 AM, Trevm said: Can anyone suggest what box style would be suit this type of area, it won't be sealed. when I 1st read that I inferred that the sub box wouldn't be sealed, and I wondered, "why?"...but then I realized you probably meant the outdoor area wasn't sealed? I would definitely recommend a sealed enclosure for this - you don't want snakes, possums, wasps etc making a cosy little home inside your sub...(or subs ). Can you send a link to the Dayton 8" sub driver you mean? Is it this one? https://www.daytonaudio.com/product/130/sd215a-88-8-dvc-subwoofer-4-ohm A very quick sim of this driver says a 17 liter sealed enclosure will have an F3 point (3dB down) at 56Hz with a Qtc of 0.7. Did you want to go lower than that? You only have 6mm of Xmax available, so I'd likely not push them much lower with EQ - my goto quick sim calculator doesn't include driver excursion 2 subs - one near each main JBL speaker will give you some more headroom, or if staying with single maybe consider a larger driver with more Xmax? Enclosure shape doesn't matter, only box volume. Build a strong sealed box - with bracing if you want overkill - but likely not required. It won't need any internal damping (eg poly batts stuffed inside), but put some in if you want overkill - just keep stuffing away from the rear of the driver when it travels backwards. The lowest F3 for a sealed box has a Qtc of 0.707 - I'm happy to give you the maths/my easy goto sim tool. Using a larger box decreases the Qtc, increases the F3, adds droop in the passband, but decreases the steepness of the high pass rolloff, so less EQ is needed to push the sub lower. Using a smaller box increases the Qtc, also increasing the F3, adds peaking in the passband, and increases the steepness of the high pass rolloff, so more EQ is needed to push the sub lower. My starting point for designing a sealed enclosure is always calculating box volume based on a Qtc of .707 (16.7 liters for that driver) - but with a miniDSP available for EQ you could easily make the box volume as low as 7 liters (Qtc of 0.99) - A Qtc of 1.0 is the highest Qtc (ie smallest box) I would go for a sealed DIY speaker. At the other end of the scale (bigger box), going lower than a Qtc of around 0.6 yields diminishing returns (30 liter box for that driver). With that driver - ignoring driver excursion - to use EQ to hit an F3 around 40Hz: a 30 liter box (Qtc 0.59) requires around 3.5dB of EQ boost a 17 liter box (Qtc 0.70) requires around 6dB of EQ boost a 7 liter box (Qtc 0.99) requires around 11dB of EQ boost It's important to note that driver excursion won't change for that F3 - regardless of box size the driver excursion will be the same to hit a particular F3 target. It's only the amp power and EQ that changes. Other considerations: where will the amp for this sub be? If you run a plate amp as part of the enclosure then you need to get 240V there...and the plate amp controls will be high off the ground. I'd be more inclined to have the amp and miniDSP at ground level and only run speaker cables to the sub box. Definitely use Neutrik SpeakOn connectors or similar that have a locking mechanism. All my DIY speakers use Neutrik these days - even more important when your speaker is up high out of reach WinISD is free and can model driver excursion - but there's a learning curve. I used Rod Elliot's version of the True Audio Linkwitz Transform spreadsheet for my calcs above - it's been my initial goto for quick sims for ~30 years. cheers, Mike
Trevm Posted November 10 Author Posted November 10 I honestly didn't think a sealed enclosure would be suited. If it will work would much prefer that to due to smaller box size. With price of Daytona I see no reason not to use their best driver. I plan to run it off a Crown which will be inside the house. https://www.daytonaudio.com/product/2062/umii8-22-ultimax-ii-8-dvc-subwoofer-2-ohm-per-coil
almikel Posted November 10 Posted November 10 so that driver has way more Xmax - 18mm vs 6mm ! 29 minutes ago, Trevm said: I honestly didn't think a sealed enclosure would be suited. There's plenty of BS around whether a driver is better suited to ported or sealed, like the "Efficiency Bandwidth Product" (EBP) being above a certain threshold etc, so supposedly the driver is better suited for ported compared to sealed etc... Once you have DSP EQ available (ie your miniDSP) - within the excursion and heat limits of your drivers, and the amp power you have available - these limitations disappear. The drivers I run as my mid bass in my setup are a classic example - stereo Acoustic Elegance TD18s in small 60 liter sealed enclosures - I've had lots of people tell me the boxes are too small! But they model with a Qtc lower than 0.7 in sealed enclosures and sound awesome! You really should download and learn how to drive WinISD - it can show you driver excursion for a given input power. I've never bothered to learn how to drive WinISD properly, and I continue to use Rod Elliot's version of the True Audio Linkwitz Transform spreadsheet as my 1st simple goto sim, which tells me a bunch...but not enough for your situation (like maybe 2 subs is needed to hit your SPL targets within driver excursion limits). Message me your email address and I'm happy to share my version of Rod Elliot's True Audio spreadsheet - or you can google it. Essentially you input driver specs and a box size into the spreadsheet, and it calculates the raw response. In a separate tab you can calculate the Linkwitz Transform EQ required to push the speaker lower. I haven't used analog EQ for 15 years, but I find this spreadsheet incredibly useful. The Dayton UMII8-22 driver has very different specs to the Dayton 8" driver I linked to earlier. The box size is much larger for a Qtc of 0.707 - 75 litres! with an F3 of 44Hz But dropping to a 20 liter enclosure only increases the Qtc to 0.89 with an F3 of 46Hz Reducing to a 12 liter enclosure increases Qtc to 0.98 with an F3 of 48Hz You can muck with the box volume then the Linkwitz Transform tab endlessly to see how much EQ is needed to push the speaker down to any frequency. I create a new version of the spreadsheet for each new driver I come across cheers, Mike
almikel Posted November 10 Posted November 10 This is a 12 liter enclosure for the UMII8-22 Ultimax II driver - Qtc of 0.98 1
Sub Sonic Posted November 12 Posted November 12 Glad I came across this, I’ve been eyeing off a pair of 8” Ultimax ii to go with a small pair of coaxial speakers. Apparently they will become available fairly soon
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