Subwoofer Questions

Discussion in 'Computer Audio' started by Neapolitan6th, Feb 13, 2018.

  1. Neapolitan6th

    Neapolitan6th Gawd

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    Hello all, I am a two channel user who is looking into subwoofers and I have a few general conceptual questions.

    I have a really solid pair of floorstanding speakers that extend down to 35hz. (JBL 590)

    My question is if an 8 inch driver can reach 35hz at the same spl/dB/ect. as say an 18 inch subwoofer, is there any perceptible difference in bass quality? Is a bigger driver going resonate/fill up a room more fully than a smaller woofer will with all other factors being equal?

    (I want to know if a subwoofer can feel "bigger" without actually being louder in dB)

    Thanks, I'm trying to see if a sub would be much of a value add for me. I'm more interested in music, but I plan to integrate into a home theater at some point.
     
    Last edited: Feb 13, 2018
  2. John721

    John721 [H]ard|Gawd

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    The trouble with that 35hz spec is that it doesn't mention a +/- db value. Which means a person should be at least mildly skeptical of it, despite the dual 8" drivers. Moving on from that though, I do think a good ported sub that can hit down to 20hz with proven authority would add to your listening experience. My older B&W 600 series with three 7" drivers definitely benefit from my SVS subwoofer - especially in movies and some kinds of music.
     
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  3. rive22

    rive22 [H]ardness Supreme

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    The smaller driver in the right enclosure can hit low notes just fine, but no it won't sound the same as an 18" at all, nor will it play those notes as loud. Yes the bigger driver will resonate and fill up the room much more fully and let you play it substantially louder before distortion. Basically if you're in a living environment where other people are in the same building like an apartment/condo then get the 8" and even that will get you in trouble. If it's a house get bigger for sure and even consider dual. What size room is this for? Is this for music or movies? What genre of music? Keep in mind 18's are hardcore, common in dance clubs and used with professional soundproofing, albeit lots of them. Dual 12" or Dual 15" in a typical house living room is nice, depending on what you're going for.
     
    Last edited: Feb 13, 2018
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  4. Neapolitan6th

    Neapolitan6th Gawd

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    Thanks for the input. This is more of a theoretical question really.

    I suppose I'll put it this way. I am cautious of my hearing as it is important for my career.

    I'm not wanting to increase volume to high values as my space isn't huge and I want to mitigate the risk of hearing damage.

    So I am curious of the importance of a larger diaphragm subwoofer if I have dB limitations.

    Given my constraints of room space and dB levels, lets for the sake of discussion assume a 12 inch and an 8 inch subwoofer are capable of producing an equal level of decibels at 30hz.

    With those factors being equal, what variable accounts for the difference in perceived sound favoring the larger subwoofer?

    I'm curious about the science of it. The wavelengths must be the same if they are both producing 30hz at the same volume, no?

    I wish to quantify the difference, but I'm not sure what that would be.

    I suppose I will just have to audition one and hear the difference for myself. Quality bass is important to me so I would like to gain a better understanding of it so that it will allow me to make a more informed purchasing decision at some later date.
     
  5. B00nie

    B00nie [H]ardness Supreme

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    The answer is a solid yes. A large driver moves air much more efficiently. Think of trying to peddle your boat with a pencil vs a paddle. The difference is present especially in the dynamics. A small driver can't 'grab' the air as well as a large one. That's why bigger is (once again) better. You don't have to play any louder to hear the difference.

    There is one caveat though. It's not enough to have a large driver but also the driver must have an engine strong enough to actually move that 18-32" cone - and it needs to be in an enclosure suitable for the driver.

    A superb solution would be a hole in your wall and stick a 18" Dayton audio ultimax through the wall. Cheap and you get bass extention close to 10hz.

    Edit: And your wife or mom will absolutely LOVE the idea. lol.
     
    Last edited: Feb 14, 2018
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  6. Pandur

    Pandur Limp Gawd

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    30Hz is a 30Hz sine wave no matter what size the speaker is. So yeah they have to produce the same wavelength. And the 8" will have to work harder to do so than the 12". But there are plenty of 8" subs on the market that will do 30Hz. Personally I'd lean towards something in the 12" range because your main speakers already claim to do 35Hz and you want something to fill out below those properly.

    There are many variables to this though. Magnet size, how far the stroke of the membrane is, membrane material, electronics quality: both crossover filters and amplifier. Type of enclosure: with or without a bass port. So bearing this in mind, a well designed 8" sub can outperform a 12" sub. But that also means you are likely looking at a higher price tag as well. Because the basic physics of this is in favour of a larger speaker.
     
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  7. SineDave

    SineDave Limp Gawd

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    The real reason most subwoofers use larger drivers is that it's more efficient, which means lower distortion. When you produce 35hz with an 8" driver, you have to get the driver a lot closer to xmax (limit of excursion before sound degrades), which distorts the sound somewhat. Larger drivers driven by larger amps will have more headroom, less required excursion and lower distortion, which you will hear as "cleaner" or "tighter" bass.
     
    Last edited: Feb 18, 2018
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  8. Neapolitan6th

    Neapolitan6th Gawd

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    Thanks you guys, some really quality responses here. It gives me a lot to think about and has helped point me toward areas of research that will help me better understand what solution will best meet my preference.

    I've been a bit wooed by what I've heard of Rythmik followed by SVS. I have heard of Dayton and a few others as well. Always open to new suggestions.

    Thanks b00nie, Pandur, and SineDave!
     
  9. B00nie

    B00nie [H]ardness Supreme

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    Xmax is not the mechanical limit, Xmech is. Xmax is the air gap minus the height of the voice coil (i.e. the length the voice coil can travel without leaving the magnetic field in the air gap). Most drivers can handle way larger excursion mechanically but the distortion and compression rises rapidly.

    For example the 18Sound 21" 1400LW has an Xmax of around 18mm but an Xmech of 57mm. So you can really punish it without the danger of bottoming the voice coil.
     
  10. Commander Shepard

    Commander Shepard Proud Brony

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    I'm a big fan of SVS subs. Have an SB-2000 on my PC audio system. Love it!
     
  11. Stoly

    Stoly [H]ardness Supreme

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    While its basically true that a 12" subwoofer will deliver a deeper and louder bass than an 8" driver, it is possible for a properly designed and placed 8" driver to deliver good bass that rivals a subwoofer.

    That said, its will certainly cost a lot more. So you are better off just getting a 12" subwoofer.
     
  12. HammerSandwich

    HammerSandwich [H]ard|Gawd

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    The Daytons offer crazy value with free shipping from Parts Express. Hsu is another good company to look into.

    And I believe you'll learn a lot by comparing various subs at Data-Bass.
     
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  13. HammerSandwich

    HammerSandwich [H]ard|Gawd

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    Oops - forgot to add:
    It's specced at -6dB. This is JBL, so you have to ignore the normal, "consumer" site & dig better info from either jblpro.com or jblsynthesis.com. They still don't have spinorama charts for all of their products, though...
     
  14. DoubleTap

    DoubleTap [H]ard|Gawd

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    I have an M&K 12" sub that goes down to about 24hz (I tested it with tones) and an 8" that starts dropping way off around 32hz

    I'd prefer to use the 12" sub, but it was just too much for my 10x10.5' office and even at a very reasonable volume, it was almost giving me a headache and making me feel.... not good. (and I like loud music and bass)

    I'm not an expert, but I do read and try to understand room acoustics, but I can't explain this one - I ended up putting it in the living room and using the 8" sub in my office (the only place I listen to music)

    So that's just anecdotal and some might poo-poo it but the level of compression was just physically uncomfortable YMMV.
     
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  15. HammerSandwich

    HammerSandwich [H]ard|Gawd

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    Rooms increase deep bass. When a wavelength's longer than 2x the room's longest dimension, the entire room will pressurize or rarefy right with driver movement. There are no modes, and bass boosts at 12dB/octave as Hz drops. (This is why you shouldn't use an anechoically flat sub in a car, at least with the windows rolled up.)

    So, smaller rooms boost from higher frequencies than larger rooms. And because the boost keeps growing, small rooms REALLY boost deep bass. In reality, you won't have that much boost, because your room leaks a bit. Put your subwoofer in, say, a small submarine, and theory should match closely. (I wonder if anyone's ever tried that one!)

    The typical speed of sound is about 1130fps, which means your room becomes a pressure vessel below 53Hz or so. Unless you have a very odd ceiling height, of course.
     
    Last edited: Feb 15, 2018
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  16. John721

    John721 [H]ard|Gawd

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    Neat. Handy little resource there.
     
  17. B00nie

    B00nie [H]ardness Supreme

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    Most likely you had a nasty reverberation in the room (bass notes stay 'alive' and bounce around). This makes it extremely uncomfortable. The solution is (reason defyingly enough) to add one or two more subwoofers on other walls or apply a good amount of acoustic treatment.

    The extra subwoofers help because the sound waves coming from multiple subs cancel eachothers out and act like a powerful acoustic treatment. You can simulate how it works using Room Eq Wizard.
     
  18. DoubleTap

    DoubleTap [H]ard|Gawd

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    Yeah, that's possible, but I managed to find a good spot for my 8" that reduces the 42hz null by a decent amount and it sounds good. I might make another run at the 12 as I'm going to go with all new living room HT gear in the next few weeks and my wife keeps making the stink eye at the giant black cube...
     
  19. HammerSandwich

    HammerSandwich [H]ard|Gawd

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    Paint it white.
     
  20. Wyodiver

    Wyodiver [H]ard|Gawd

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    If the local urban crowd aren't impressed, den you doin' it wrongly. Even on yo' birf' day, ya gots'ta represent, no whut I sayin'?
     
  21. SineDave

    SineDave Limp Gawd

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    Yes, good catch. That's what I get for trying to dumb it down :D

    I think the point in either case is that you don't want to use tiny drivers that have to come close to xmax to achieve reasonable output at lower frequencies. That also doesn't address the issue of power - so many cheap subwoofers are criminally underpowered. It takes roughly double the power for every 3dB of output you wish to add. Then you account for the fact that most subs roll off around 30 Hz, so if you want to play clean down to 20 or the teens, you need thousands of watts instead of hundreds.
     
  22. B00nie

    B00nie [H]ardness Supreme

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    The old saying there's no replacement for displacement is valid also with subs. You can go only so far with a small driver. Even if you have an insane amp to run it, the drive will die either to heat or overexcursion and still do a poor job before it dies. A small piston is ineffective in pumping air and that's basically all what a bass driver does.

    Of course a good quality bass is possible also from a 8" driver, especially if it's servo driven. You just won't get a whole lot of it.
     
  23. SineDave

    SineDave Limp Gawd

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    Yes, and this is my problem with audiophile subs like REL. Small drivers, weak amps and generally no "brute force". I have found that when properly implemented, the bad-boy subs actually play much cleaner than any audiophile sub.
     
  24. HammerSandwich

    HammerSandwich [H]ard|Gawd

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    Hofmann's Iron Law is a bitch.
     
  25. butterfliesrpretty

    butterfliesrpretty 2[H]4U

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    Don't get a Dayton, I had one and it wasn't bad with my Klipsch bookshelves, but I would not in anyway consider pairing with some 590's. If you want something to accompany the 590's properly go Svs, Velodyne or Hsu and it should probably be one of the more expensive models. Or you can be happy with what you have with the 590's because even if they won't reach 20hz, they are still amazing as far as bass in concerned.
     
    Last edited: Feb 21, 2018
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  26. Nenu

    Nenu Pick your own.....you deserve it.

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    Something to watch out for.
    Many subs minimum crossover point is 40Hz, no lower.
    Because your speakers extend lower than this you could end up with an overlap.

    I had exactly this with my Transmission line speakers that extend to 22Hz.
    The room booms around 30Hz which made it worse.
    The sub is a BK Monolith with a min xover of 40Hz so I contacted the mfr and they told me which cap to change.
    I set it at 25Hz which is perfect.

    Moral is make sure you can modify the circuit if the stock min xover Hz isnt low enough.
     
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  27. butterfliesrpretty

    butterfliesrpretty 2[H]4U

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    A lot of receivers these days will allow the speakers to either be set to small, or stop at a specific frequency. I would check the manual to see where the speakers stop at if set to small if they don't allow it to stop at a specific setting.
     
  28. Mega6

    Mega6 Gawd

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    Yep, see Dolby, AC-3 and DTS to crossover the Subwoofer with the rest of your system. Once the crossover is set, your home theater amp doesn't waste energy on the low frequencies and everything gets a lot louder with a high powered self amplified sub. SVS is great - have a PB-12Plus and it can move a lot of air.
     
  29. Nenu

    Nenu Pick your own.....you deserve it.

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    You can hook many subs up in 2 ways at the same time.
    1) Line in/balanced from the receiver for the LFE channel (and other bass mixing if you dont use 2)
    2) High level input from the front speaker amplifier outs, matched to the speakers response.

    I prefer the response of 2) for non LFE use.
    All processing can be disabled for stereo playback to get max fidelity.
    Line in/balanced is then used for LFE only.
     
  30. BigJayDogg3

    BigJayDogg3 [H]ard|Gawd

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    I will absolutely disagree with this based upon personal experience. That is almost purely a function of enclosure design. Even an average subwoofer in the right, well built enclosure will produce a ton of output over a fairly broad spectrum without needing a ton of power. I had a cheap 8 in a thrown together ported enclosure that had more extension than a pair of 12s in a sealed enclosure with the same power. Had I built that enclosure to be more home theater style, I probably could have gotten it to go even lower.

    That said, the 12s had more overall output almost everywhere in its usable spectrum.
     
  31. |Tch0rT|

    |Tch0rT| [H]ard|Gawd

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    I'd take a Dayton Ultimax DIY build over any of those prebuilt ones. Though if you don't have the tools then it's best to go pre-made.

    WTF you set your subs to 25hz and below? lol There's usually no reason to cross over that low. Where your mains are aren't usually where the bass is best. Also the subs will do anything 100hz and under better than most mains. You use a crossover between the mains and subs and there shouldn't be any overlap. ¯\_(ツ)_/¯
     
  32. Nenu

    Nenu Pick your own.....you deserve it.

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    In your opinion ;)
    Have you heard a transmission line speaker?

    I explained the exact reason why a crossover was needed at 25Hz, odd you would go directly in the face of that.

    There is a crossover between the sub and mains using my method 2, I described it.
     
    Last edited: Feb 22, 2018
  33. |Tch0rT|

    |Tch0rT| [H]ard|Gawd

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    I find your Xover spot to be odd. Yes I get you have boom at 30hz which is probably due to the dimensions of your room (room modes). Your speakers or sub is probably in where it resonates at that frequency the most. My room has one around 40 - 45hz and my mains are good to about 45hz but it doesn't make sense to X over my sub at 40hz as my 4 subs will do under 80hz much better than my mains and gives more headroom. There is no overlap as I have my active crossover set to 80hz with a 24dB slope. I also use a mic and REW to measure and PEQ's to tame peaks (can't do as much in the room mode though). Yes I know about transmission lines. You usually see them with small subs to get big bass in a space that a larger sub wouldn't fit in or floor standers in 2 channel systems that don't have subs. There isn't much information in music under 25hz and most commercial subs will struggle with anything under 30hz with any kind of authority up until internet brands like SVS and HSU started becoming popular. That's usually in the realm of movies and LFE channel.
     
  34. Nenu

    Nenu Pick your own.....you deserve it.

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    My speakers in this room roll off at 25Hz and above that give "substantial" tight bass from 2x 10" woofers in transmission line.
    The sub needs to take over from 25Hz.
    I dont want the sub to be pumping at 30Hz+. I explained that my room booms around 30hz.
    Straight forward.

    There is plenty of sub 25Hz bass in music.
    Have a listen to Tron Legacy.
    My sub has in room response down to 15Hz, it rocks!
     
  35. B00nie

    B00nie [H]ardness Supreme

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    You have to reverse the sub and cross it over at 30hz - no boom.
     
  36. SineDave

    SineDave Limp Gawd

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    Find me one example that can hit 16Hz or lower with acceptable distortion at reference level. Emphasis on "play clean". Look at your THD+N on those subs, you'll find that they don't play clean down below 20 with low distortion, regardless of enclosure. There is a reason that all the top ranked subs use beefy amplifiers and large transducers to play down into the teens. Data-Bass has all the info necessary to vindicate that.
     
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  37. jevans64

    jevans64 Gawd

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    Another recommendation for an SVS sub, simply because they have a built-in DSP. This will allow you to just split the full bandwidth signal and let the sub handle the cross-over. As one who has an SVS SB16 Ultra ( 16", 1500 watts ), I rarely turn it on for music unless I'm listening to stuff with heavy bass, like EDM.
     
  38. B00nie

    B00nie [H]ardness Supreme

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    It's not a very good recommendation for a sub if you choose to not use it with music.
     
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  39. butterfliesrpretty

    butterfliesrpretty 2[H]4U

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    You have a very odd setup, and your description for how to setup the speakers/sub is also unique. It might work for you, but is not the way to go for the vast majority of people.
     
  40. Nenu

    Nenu Pick your own.....you deserve it.

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    I explained the setup so if it matters the method should be considered.
    Its not odd or unique that some speakers respond below the min cutoff of many subwoofers.
    It was worth the mention.
    Would you rather this wasnt covered when his speakers respond to 35Hz?
     
    Last edited: Feb 25, 2018