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Bass Driver (speaker) Specifications

Discussion in 'Live Sound [BG]' started by type C basses, Apr 13, 2011.

  1. I think this is the best place to post this question.

    I'm looking to add more low end to my bass rig. I've decided to build an 18" cab that resembles a PA subwoofer, then bi-amp it and set the crossover so that it handles everything below a certain point. I'm not sure where yet, but I think it will be somewhere between 35-70 Hz. Also, I plan to play a bass with a low F# (23 Hz) through it. I need to decide what driver I will be using before I plan the cabinet.

    What traits should I be looking for in a driver for this application?

    What would be the the deciding factor(s) of air displacement and how much of that would I need to fill a medium sized club (down to 23 Hz) without PA reinforcement?

    What makes a driver good (NOT sound quality-wise) for live sound vs home theater or very large venue PAs? Something with the length of the driver's excursion or its rigidity? Or even the surround material, foam vs. rubber?

    Before I begin to ramble, please share you knowledge with me. I promise I'll make a build thread.;)
  2. I don't think you realize what you are asking for. 23 Hz is very low, and pretty much inaudible without massive amounts of power and displacement.

    This is down a full 10 dB at 24 Hz. That's a box bigger than an Ampeg fridge that weighs 200 pounds and costs about 2 grand. With a couple thousand watts it will almost do what you want, two of them would be better.
  3. Passinwind

    Passinwind I Know Nothing Supporting Member Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Let's start at the very beginning. Do you have a dedicated electrical service outlet available to you (just you, not the band or anything else) at every gig? If so, what are its specs?
  4. Still looking for info on THE DRIVER ITSELF!!!
    I have a decent understanding of the physics behind sound reproduction and room acoustics, as well as basic power handling.
    FWIW, my home theater sub hits flat down to 20 Hz, with +/-3 down to 15 Hz, 11 Hz @ +/-6...so I KNOW my low-end, friend.:cool: And it's only 13", run by less than 600W! Enough about that.
    People can already 'hear' my bass lines fine, it just lacks the visceral impact in the lowest few notes, and I'm about to add five notes even lower to this.

    In short, yes, although not 'every' gig. 230V, 30A seems to be the standard around here. Let's pretend I can harness the power of all the lightning in the skies! Now, what aspects of the construction and materials would make this lightning-driven 18" speaker suitable for live bass guitar?
  5. Sounds like you've got it all figured out.

    Just get a couple more of these magic, physics defying, home theater subs and use those.

    Problem solved,
  6. kesslari

    kesslari Groovin' with the Big Dogs Supporting Member

    Dec 21, 2007
    Santa Cruz Mtns, California
    Lark in the Morning Instructional Videos; Audix Microphones
    Manufacturer's specs, by any chance? Or do you have accurate measuring equipment?
  7. They're $1500 each, jack***, that's why I'm going DIY! DO IT YOURSELF=CHEAP!

    I have figured out that since you had not a clue to answer of my original question, you decided to chime in with some trivial observation questioning whether or not I know *** I'm even talking about. What I haven't figured is why you chose to do so. However, that is history and this is now; so I shall handle the present in a manner in which I failed to handle the past.
    You offer no help. Please leave my thread.

    To anyone else...I understand, from a power handling standpoint what demands need met to build a subwoofer enclosure.

    My question, as still stands, is what do I need to look for in a subwoofer driver that will be used to run live bass guitar?

    Material stiffness? No?
    Abnormally high excursion? No?
    Overweight magnet? No?
    Am I just not getting something, here? Should I be less selective in my driver choices? Should I just throw a dart at my computer screen?:p
  8. SVS 13 Ultra, 2 ports plugged. Mine's tuned up real nice to the room (vs. anechoic measurements) so some room gain may be factored in...but can we please keep this on topic.

    p.s. my sub's better than yours; and if it's not, I want yours!:D
  9. from my rather limited understanding of these matters you're really going to need excursion so you can move lots of air.

    I would look to some of the Eminence speakers, both 15 and 18 inch and model them on WinISD. Good PA subwoofers are built to be sturdy enough to handle the serious wattage required to get where you're trying to go.

    Good resources to check into on this forum also would be Bill Fitzmaurice, Greenboy, and Duke LeJeune, they post a lot on various low frequency matters and know their stuff. Hope this is helpful.
  10. fwiw, the most highly touted 15 that might be of interest to you would be Eminence 3015LF, a big neo job. I know you said 18, but that's a start since there appears to be a lot of experience here w/that driver in very low frequency DIY cab builds, notably Greenboy's fEARFUL.

    Eminence makes a line of 15s and 18s called Omega or something like that for pro PA sub/woofer applications but I really don't know much about them. Check their site as they have a lot of helpful info on their products.
  11. Thank you for your input. A high excursion makes sense, to be able to move the most air. I guess the area that I am failing to grasp is the break-even points. Like, how much wattage to displace X amount of air with an 18" and would it be more efficient to move X air with 2 15"s. The thing is, I am concerned only with frequencies approx. 23-50 Hz. The 18" just makes more sense to me since it will be experiencing less wear and tear (performing less work) than a 15" in the same situation (I think). I also realize that enclosure design is a huge factor, but that's for later. What are some good brands other than Eminance? I'll definitely check out fEARFUL.
  12. Eminence is the one I have the most experience with because they tend to be the most accomodating to DIYers, they have a big selection at all different price/performance points and they're readily available from a bunch of different places like Parts Express, Speakerhardware, etc here in the States (I'm assuming you're in the UK).

    Not sure if you need to be focused on an 18, the latter day 15s are really something else, excursions up to 10 mm or more, low Fs's and there's more to choose from than in the 18s.

    Like I mentioned earlier, take a look at some of the higher performance Eminence drivers (i.e. more expensive), pop their T/S parameters into WinISD and see what happens. And check into the fEARFUL wiki, there's a 2X15 sub that gets very low and it's a lightweight cabinet. Relatively speaking, of course, compared to the venerable SVT 8 X 10......:bag: But they're well designed and highly regarded here on TB.

    What are you planning on for the cabinet design to get that low and still be able to tote it?
  13. cableguy


    Jun 4, 2009
    North Bend, WA
    Fearful 15/6 with a 15/sub should be a good starting point. If that's not enough add 2 more. Lightweight, modular (you cann build one at a time) and move a lot of air. I don't know all the frequency plots and such but if you need to go lower than they provide I have no clue how to do it cheaply.
  14. View attachment 208723

    there's been a lot of ways over the years to move a lot of low frequency air, none of it simply or cheaply, but this has to be one of my all time favs :cool:

    GL said that on stage he could actually feel the air blasting into his back from these old JBL scoops. And they (and Genesis et al) put Moog Taurus pedals into them w/kilowatts of Crown etc amps so you know they could go low. Of course they had battalions of roadies to move the stuff but that's another story.......:meh:
  15. Good stuff!

    I like the idea of using the 15" or 18" to handle the low low and allow my Ampeg PR410 to cleanly handle the info above 40 Hz. This is opposed to stacking 15"s until it reaches the desired output.

    I definitely haven't had enough experience with different cabinet configurations to know what I like yet. This is my jumping off point, so to speak, from 8x10s 6x10s 4x10s. I hope I never look back. Also, this cab will primarily be used if the venue has no subs/ very poor subs, in their PA system.

    I'm from the US, east coast. I'm liking Eminence more and more...
  16. I'm a fan of starting with established configurations and then taking it from there. Provided one has the necessary information and tools to work with the data, otherwise I won't stray.

    I don't believe the question is whether or not you going to be able to get that low, you can, it's done. The question is how well and still keep everything reasonable for a gigging musician, in short, it's an engineering exercise. You know you're going to need serious power so you're looking at a big amp, but you have a lot of choices there w/all the Class D/switching power amps. So the earlier posts on power requirements are to be heeded, it's gonna take a lot of juice that may not always be available.

    The point being, you may be leaving behind your old 10s rigs but you may be going into more complicated and expensive territory that may or may not work out. Once you run the numbers and do the design homework first then you'll have a better idea of how feasible this is given the limitations you have of $, schlepability, house power, etc. I'm not being a naysayer or anything, but be please be careful because this could be a real rabbit hole and a lot of folks have gone to extremes to address these same issues over the years w/huge folded horns, 30" woofers (yup, Electrovoice made one years ago), the Grateful Dead's famous walls of Alembic speaker cabinets and McIntosh amps (the reasoning being that a 30 foot long wavelength needs an equivalent speaker size) and on and on.

    I'm glad my needs are a little simpler (GK400RB, 2 Peavey 10s in DIY cabs, done) but then I'm just an old geezer :D Good luck, post the build, please, this sounds interesting.
  17. Thank you so much, dhsierra1. You have alleviated my apprehension. Don't worry, I'm an experienced rabbit hole navigator.;)

    With what formula(s) should I start? I guess I need to consider estimated max room size, air displacement needs/speaker specs, enclosure stuff, power requirements (could probably use the most guidance here), and lastly crossover point, placement, and empirical testing. Wish me luck and success!
  18. BogeyBass


    Sep 14, 2010
    If your trying to get amazing amounts of low end from a Single 18" speaker....its not going to happen.....the SPL is limited to a single driver and you need to dump alot of power into it...to get up to high levels.

    If your going to try and get alot of bass from a low cost 18" speaker...then your choices are a Eminence Sigma Pro or a Eminence Delta Pro. both should be in the $139 to $159 price range.

    Like i said doing a single 18" cabinet with those speakers would be a waste of time.

    To bring up the sensitivity and power handling you would be better of doing a 2x18" cabinet....and at that point it would not take more than 150 to 200 watts to get up in the 122 to 128dB range....

    with a single 18" you would get to much distortion at those levels and distortion would kick in pretty early with only 120 to 150 watts

    So if your willing to stick 2x18" in a BB4 alignment your looking at 11.4 cubic feet ported at 28Hz for the Sigma Pro
    and 15.7 cubic feet ported at 27Hz for the Delta Pro

    that would be the way to go...otherwise a single 18 is a waste of time really more than money....the Eminence drivers are cheap as heck.

    A more expensive route that would make you happy is a 2x15 cabinet with Eminence 3015LF.....i would have to run those threw WinIsd to get the numbers....most likely be somewhere around 9 cubic feet tuned to 40Hz.

    cost wise the 18" speakers would be cheaper....but they require a bigger box.
  19. What you're asking for is a bit beyond what I can help you with here on this forum due to space and my lack of expertise, but I would do the following to at least get started.

    You need to learn more of acoustical engineering to answer a number of those questions, and remember, that's all going to vary anyway from venue to venue anyway. I'd go to the "amps" forum and check out some of the FAQs and stickies there and you will find a treasure trove of great information and links. In fact, I'd start there before you even start messing with the cabinet design. Look at some other builds to get ideas, esp the fEARFUL.

    Then, download the free "pro" version of this program and get to know how to be at least a 20% user:


    Peruse the Eminence website and start identifying speakers that have T/S parameters like high xmax and low Fs. Then start plugging those into WinISD and play away. Eminence sometimes posts cabinet suggestions for some of their models and those are helpful, too.

    You will spend long evenings in front of your computer screen but there is no other way to learn this stuff. I've been fooling w/DIY spkr builds for many years and I'm an engineer by training but I am in no way an expert, guys like Bill FitzMaurice and Duke LeJeune do this for a living and have forgotten more than I will ever know about this. Check their websites out, too.

    Hope this helps, take your time and don't spend money until you've got the math and physics down a little more.

    Then, once you narrow stuff down you can proceed to spending money and creating lots of sawdust. And if you can find an established design that could work, I'd take that route, but at least if you do the previous stuff you'll learn a lot and that is in and of itself worth doing, esp if you're serious about all this. It's provided me years of entertainment, education, successes and failures, and an emptier wallet, but why not? :D

    Good luck.
  20. Sound advice from someone who obviously knows his way around this stuff, just short-cutted my suggestion, thanks! :hyper:

    The 3015LF suggestion sounds like the fEARFUL design. Those drivers are something like 350 clams or more a pop, but then who said generating low frequencies was cheap? :eek: