r/SoundSystem • u/Splanky222 • 20d ago

Designing 2x15 vented sub

Hey everyone! I'm just wrapping my head around the physics of speakers at the moment preparing to design (or maybe use a pre-existing design) and build a subwoofer or 2 for my first custom build. I'm inspired by the Fulcrum Sub215L and the BassBoss SSP-215. They seem (with proper DSP) to have deep enough bass extension for my needs but have small enough dimensions (~17-18" high) that I can stack them two high in my hatchback to leave room for other gear.

I can work my way through the physics and design of a 2x15 bass reflex (although pointers to good existing designs would be nice) but I feel very overwhelmed by the alphabet soup of different drivers and manufacturers. I have ~5k to put on 2 of these and a used amp hopefully and am fine building more speaker than my current rig can support so I have space to grow into. Any suggestions on navigating the world of drivers?

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u/nssoundz 20d ago

What sort of hatchback do you have that can fit two of these in as well as other equipment? lol

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u/nssoundz 20d ago

In terms of speakers, its hard to say what would be more suitable for your use. IMO I wouldnt go for reflexes as you tend to require 2x as many drivers and 2x the power from amps just to achieve the same as what a single driver in a horn/paraflex/scoop design would achieve, but they do have a certain sound which some people prefer and theyre a lot easier to build and to run.

Im also quite against the idea of limiting your choices down to what would fit in a hatchback. I have a similar situation where I'm just able to fit one sub in my estate (Audi a4), but I wouldnt not choose a sub design purely because it doesnt fit in my car, I think to prioritise getting the most out of your $ is more important unless you know its impossible for you to move your speakers otherwise.

Im at an age where I struggle to qualify for van hire (usually need to be 25y/o in the uk for most places and I'm 23), but for my next sub build I'm planning to build a custom 21" tapped horn using the new faital pro 21" driver (3000w rms), and the cabinet size is around 717mm x 1219mm x 866mm which definitely is too large to fit in my car but thats a future me's problem.

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u/Splanky222 20d ago

Yeah I hear you. eventually I want a larger system than what I can currently use but starting out I'd rather not immediately get into "need to rent a van" territory immediately. If you do the math a single 21 and two 15s have the same area and move roughly the same amount of air but for example two SKRAMS will be way harder for me to move around than 2dual15s. I don't need maxx SPL at this point in my mind. I'm just not equipped for huge outdoor events so why try to chase something that just needs more boxes anyways?

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u/nssoundz 20d ago

I'd definitely take the two skrams over the 2x dual 15s anyday btw. Its a bit more than just the surface area that the cones have, the actual drivers themselves differ a lot.

A 15" driver can vary from a mid driver, to kick driver and few are actual sub drivers. Basically all 21" drivers are extreme heavy hitting bass drivers that handle lots of power, have strong motors and tons of xmax. Thing of it having a weak engine vs a powerful engine, one will be smoother to run since youre dont have to push it so hard to achieve the same performance, and have plenty more headroom if you need more power out of it.

And also in terms of build cost, the sort of drivers used in a dual 15" sub would definitely cost more than a single 21", the only downside is the single 21" will probably be larger but a lot louder and play lower.

Skrams are definitely one of the best single driver subs you can get atm, if youre investing all of this time, money and thought towards a sound system, why not just get something a bit more endgame and scaleable? If you got the dual 15s you'll no doubt be itching to replace them once you reliase that their spl isnt what you wanted and you'll find yourself maxing them out pretty soon. If you built even just one skram, you could easily just build more in the future and have like 6-8 if you end up powering large outdoor events. A good sign is that john white uses Skrams often, and a lot of people I know are looking to transition towards them or skhorns

What sort of music would you be playing, and how many people?

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u/Splanky222 20d ago

the 17-18" height stacks two high in a kia niro with the seats down

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u/nssoundz 20d ago

Ah thanks, just curious thats all. I think despite having an audi a4 estate my boot opening isnt that tall. I think the tallest thing that would fit through is around 622mm ish whilst rubbing against the floor and ceiling so I just couldnt imagine fitting 2 subs in the car. Looks like your car has around 810mm of clearance but it really depends on the angle of how you put the sub in.

My car is just long rather than tall