First Build... Reccomendations for extreme low freq. drivers?

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Hi everyone, I hope I have the right forum... I've been reading around for the last few months checking out different designs and things for speakers and while I have an idea what I want now, there's so many to choose from I dont know how to go about getting started. I will mostly be playing minimal techno, and from what i understand the best part of the experience is from the parts of the spectrum which we dont hear but really really feel. (~10hz?) I would be very open to putting a subbox into the mix but I really have no idea so I hope someone here can help. here's an example of what music i would like going on it... I think this pretty much explains what i'm going for. my budget for this first one is about $500 (all in, it's my first one so i don't want to go tooo crazy on the credit card.) Boxes can be a good size. not couch size... but recliner size :) Low End!!! can you guys recommend me some drivers? thank you! *edit* topic got moved i think, just so everyone knows i'm looking to make a set of speakers for that $500, not just a sub.
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What do you mean by a set for $500, do you mean a pair for $250 each and with infra sound capable... and small? What, (do you mean) about 100L each?
So after all (the thread gets matured for more understanding of the project directions) the Econowave comes to mind but as PA/SPL type doesn't have anything of sub frequencies. How far off am I?
xsundown, your case might be different or r your requirements the same?!
haha, thanks for the responses guys (we'll figure this out sundown.) :D i thought I was getting a feel for what needed to be done but now that it's time to buy parts i'm so over my head. a pair of 3way speakers for $250 each. 2x woofs,mids,tweeters. I would really love a deep low bass build, but would like to achieve this more with size and not ultra expensive drivers. the unit is for home and does not need to be super loud. cabinet size is relatively open. I don't have a good eye for liters yet, but the size of a 50 gallon drum seems pretty manageable to me. I would go bigger too if need be. I would like to keep each one smaller than a refridgerator. if you can point me in the direction of some drivers i would sure appreciate it. thanks again :)

Do you have any electronics to work with?

If it were me, I'd look for a pair of Mission 760i speakers as they're very cheap 2nd hand, but still sound very good. They do need bass support below ~90Hz though.
You'll need an amplifier for them.

If you have the amplifier already, those Missions would be my go-to, and then you can spend most of your budget on a decent subwoofer: 10Hz will take a lot of doing. I think you might need to look 2nd hand for that.

You could try going for 4x 12" long-throw car subwoofers, such as the JBL GTO1214, or there's a similar one by Infinity.

4x 12" drivers provide similar cone area to a pair of 18"ers, with ~12mm one-way travel.
Put them in a sealed box as big as you can, or maybe go for an EBS ported alignment, tuned for 10Hz - decide on a cabinet volume and see what you can get away with.

You're gonna need a couple of kilowatts for this.

Hey Chris! thanks for the advice. I looked up the 760i's and while they are sexy looking I have to admit that i am more eager to build than I am to own... someone has recommended I try starting with the Econowave speakers, which from what i read seems like as good a place as any to begin. I'm not sure how that will affect which sub design to settle on, and I dont know enough about the science of it to say for sure that 10hz is what i'm going for, it's not written in stone... I'm mostly looking for that "underwater feeling" and figured lower is better. Is there much of a difference between car drivers and home audio? besides marketing and maybe durability? a couple Kilowatts meaning I should run them through a seperate amplifier? sorry for my noobishness. I have a small Dennon Amplifier here, RCD M37 (~65w), but it's nothing much. For the sake of making a decision how does (2 x 2 x 3.25 ) sound? approximate.
Okay, a really quick simulation with 4x JBL GTO1214s in a 360L enclosure tuned to 12Hz (assuming your dimensions are in feet) gives just over 110dB down to 10Hz, with 2000w input power.

Note this must be clean power, no clipping, and I hope your building is strong.

Tuned to 17Hz, you can get ~116dB to 15Hz.
For both of these, you need a 2nd order low pass at 20 and 30Hz respectively - this flattens the frequency response, which would otherwise droop down because the ports are tuned so low.

You'll definitely need a seperate amplifier for this, and you'll also need some kind of line-level crossover to split the subwoofer frequencies from everything else.

The Denon amplifier will be fine for powering your main speakers.

Car audio and home audio subwoofers can be interchangable. What matters here are T/S parameters, which give an idea of how the driver will perform in various enclosures. Some car subs are designed for one-note loudness in tiny boxes, which is fine for a car (the car's "room" gain adds a lot to the low end) but terrible for home use, as there isn't so much gain available.

The car subs I recommended above will do nicely for home use (I'm using a pair of JBL GTO1214s at the moment, they've half a kilowatt between them) and are widely available.

IMO, its worth building the biggest enclosure you can (2'x2'x3.25' is plenty), add 4x 12" drivers and play with port tuning and eq. I think you'll find something you like, and those drivers aren't all that expensive if you do cook them.

I'd struggling to find what you're referring to.

There's a Celestion 15"er for that much, but no 18"s in sight.

I'd be tempted, but ensure they have plenty of Xmax before going for them. Going this low is all about moving lots of air, so be sure to compare Vd (cone area x excursion) with other drivers before going for it.

Power handling is also important, as designs like these tend to be very inefficient, so need a rocket up them to get serious SPLs.
For the majority of the time, however, subwoofer drivers have enough power handling. Its only when you want lots of output from a tiny sealed box that power becomes an issue.

Celestion mostly make PA and guitar speakers, the latter of which won't even be discussed for subwoofer use: a bendy cone and <1mm of Xmax? No thanks.
So, PA drivers.
Generally speaking, the primary purpose of PA speakers is to survive putting out loud SPLs for a long time.
So, first up they make them as efficient as possible. That means you get more sound out for a given power input, so you don't need to hit them with a couple of kilowatts to hear them. To get a high-efficiency speaker, all the moving parts must be nice and light, and the motor assembly must hit a compromise between efficiency and linear excursion.
Efficiency is key, so they concentrate the magnetic field over a fairly small area, and fit a voice coil that's only a little bigger. That way, little of either magnetic field (from the coil or the speaker magnet) is wasted. So far we have a driver with relatively small Xmax, but high efficiency because of it.

But we want more.
Lets take a look at the cone and suspension. If we make the cone nice and light, there's more efficiency to be gained - its easier to wave a light thing around than a heavy thing.
The suspension must also be fairly stiff, particularly so toward the ends of its travel: PA speakers must be designed to survive abuse, mechanical or thermal. If some really low frequencies come along that hit the speaker, a HiFi speaker will often bottom out. Coil hits backplate, nasty clacking sound, and you know you've done something wrong. Chances are the voice coil is also ruined and needs replacing.

A big bunch of 18" drivers suddenly subjected to infrasonic turntable feedback must be designed to survive, despite the lack of cone support from the cabinet (we're using resonant enclosures that "let go" of the cone below tuning). You can't run around re-coning them all every time someone does something stupid.
So, the suspension is designed to gradually lock up when driven past the driver's relatively small Xmax.
Check out the excursion specs for some Eminence drivers - Xmax is tiny (that's the linear bit), Xlim is usually quite big. Home drivers often have Xlim and Xmax within a few mm of each other, as the suspension tries to lock up all at once, (with some success). You get clean bass while you stay in Xmax, and it suddenly goes horrible if you push too far.
PA speakers distort gradually with low-order distortion, because of the gradual change in suspension compliance. Some find it pleasing to the ear, and it certainly doesn't sound as bad as a home driver driven past its Xmax.

So, now we have a PA driver with a fairly stiff suspension, a light cone and a fairly small Xmax. The first two raise the resonant frequency of the driver, which is a big knock against bass performance. The latter means the low-bass SPL is limited, but it'll go much louder higher up in the frequency range (say, 60Hz and up, where it really hits you in the chest).

Based on that lot, PA drivers aren't fantastic for use as subwoofers compared to a similar-sized home driver, but they will go effing loud if you need them to.

Note that WinISD simulates for ground plane SPLs. As soon as you back the subwoofer up against a solid wall, you get +6dB for free, and another 6dB if its in a corner.
You also get gain when the half-wavelength exceeds the longest room dimension (IIRC), but that's for perfectly sealed rooms, so don't rely on that.
Also remember that concrete turns to paper at frequencies this low, so take the groundplane SPLs as roughly what you'll get, and anything over that is bonus.

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