General SUBwoofer Advice Thread

Discussion in 'Speakers' started by shotgunshane, Dec 31, 2019.

  1. shotgunshane

    shotgunshane Floridian Falcon

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    I thought it was about time we had a general subwoofer advice thread. And with that, I’ll start it off with my request for powered subwoofer advice.

    I have a 2 channel set up in my living room. It is for music only. The room is approximately 15 feet deep by 21 feet wide with 8 foot ceilings. It opens up into the dining room, which is approximately 10 1/2 feet by 12 1/2 feet.

    My speakers are NHT C3 bookshelves on stands. They are a 3 way, sealed design. Soundstage and imaging are fantastic. They are amazingly clear and neutral, however they lack punch and low extension.

    I have read multiple subs (2-4) will sound more even at multiple positions, which is desirable for me, as most listening will be done out of the primary listening spot (the C3’s are excellent in off axis response and sound great from anywhere). However, that raises the need to spend more and size/WAF is crucial.

    When I was first looking at single subs, I was considering the Monoprice Monolith M-10S, HSU VTF-2mk5, Rythmik L12 and the Martin Logan Dynamo 800x (for its room correction; otherwise seems overpriced). But now that I’m leaning towards 2, some of those larger sizes will become an issue for the second one (not to mention price). So RSL Speedwoofers were added to the list. I’m not looking for validation of these choices but real advice on how I should handle this and if I should consider other subs makes/models I’m definitely open to it.

    Since I’m music only, I’m really only concerned about enough SPL down to 30 Hz. I don’t have sealed or ported preference, other than concerns of ported size getting to big and sealed having enough room filling SPL. A lot of listening will be done on the dining room b/c that table is used as a family area for legos, puzzles, etc. I’m hoping 2 subs resolve any suckouts and I can always add a MiniDSP or Anti-Mode (just for the subs) for troublesome peaks later.
     
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  2. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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    SVS' 12" sealed boxes are also really nice. For a swarm of subs a mic and DSP is a must because with every sub the system complexity goes up by the order of magnitude. 1 sub means you need to match it to the mains and the room/listening position, every extra sub means you need to match it to the previously mentioned stuff and make sure you don't get extra suckouts when they all play together. More subs allow for extra control, a more controlled response can only be achieved if the integration is successful. If not - things can actually get worse.

    I'd use a MiniDSP 2x4HD to do advanced sub managment and DA for 4 channels. You'd just need a way to properly hi-pass your mains.
     
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  3. shotgunshane

    shotgunshane Floridian Falcon

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  4. fraggler

    fraggler A Happy & Busy Life

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    Not sure if my data point will help since I am a budget-fi speaker guy, but the Rythmik L12 was a revelation for me. Super compact for a 12", reaches very close to 20hz, comes in 3 finishes (WAF!), a couple different slopes for different use cases, and supposedly the servo tech provides better control for music. I definitely hear different bass notes and get no vibration/rumble unless I am supposed to (soo different from my past subs). If you get two, you get a minor discount. I came from big box store Energy, Yamaha, and Cerwin Vega subs in the past. Poops all over them for just a couple hundred more than I had spent. I also considered SVS subs, but only heard them in a showroom that made every sub, no matter how expensive sound like big vibrating fart machines.
     
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  5. ergopower

    ergopower Friend

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    In my experience, high passing the mains is another benefit of using subwoofer(s). Bookshelf speakers seem to clean up/open up when they don't have to deal with the bottom couple of octaves. Yes, they'll play down to a certain level, but without the ease if the bottom is cropped. The MiniDSP suggested by @Hrodulf is a good solution. Some subs also have speaker-level crossovers that do the same thing except in the analogue domain. Less manipulation of digital and line-level signals, but you lose the ability to digitally shape overall frequency response.
     
  6. Riotvan

    Riotvan Got lost for three weeks at Delft City Hall

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    I messed around for a while without a proper high pass on the mains and never could get it satisfactory. With a minidsp SHD studio having a digital crossover and dirac it's fucking awesome. No dips no bumps all the way down to 25hz. Just a gentle 5db slope.
    One sub for each channel crossed over at 100hz but since the mains are stacked on top of the subs there are no localization problems. Looks cool, I'm very happy.
    I'm digital only so for vinyl i guess you need something analog.
     
  7. randytsuch

    randytsuch Almost "Made"

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    For a while I had a couple desktop speakers with a subwoofer.
    For the speakers, I remember building a simple line level high pass filter to remove the low frequencies.
    I had a minidsp 2x4 setup to feed the subwoofer. It made subwoofer integration easy. I tapped my dac's analog output to go to the minidsp, it has analog and digital inputs.
    I also bought a mic and used REW software to help setup the sub.
    If I were doing this now, I'd get the minidsp umik.

    If you have multiple sources and a preamp, you should be able to Y the preamp outputs and connect to the minidsp analog input.

    On subs, I built a Rythmik a while ago using their driver and amp and a Parts Express cabinet. Its used in my HT, and does a great job there. Probably overkill for HT, but no regrets. Now I would just buy the L12.

    Randy
     
  8. squishware

    squishware Friend

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    I run the JBL LSR310S and feed it balanced out directly from the Bifrost 2 and it crossovers out (balanced) to my pair of 305P MKII monitors. The monitors are ear level on stands on top of the desk and the sub is centered between the monitors on a Auralex Subdude 2 on a stack of 3 layers alternating concrete pads and shower liner squares with the bottom layer being 4 - 6 x 6 Wagner neoprene and rubber vibration pads.

    The port of the sub is about 20 inches behind the face of the monitors. To my hearing the image is seamless. The wall behind all this is 13 inches from the downfiring sub and 43 from the rear ported monitors. When I recline fully in the recliner centered behind the desk I am inline with the port of the sub.

    I tried the sub in different off-centered positions since common knowledge is sub frequencies are non-directional. I think the people who say that are the same ones that cannot hear DAC differences. To my ear both DAC changes and sub positions in relation to the mains are super critical. I credit the seamless image to the crossover in the sub because if I change the volume of either the sub or the monitors in relation to the other it breaks it. I like engineered solutions.
     
    Last edited: Jan 1, 2020
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  9. Hrodulf

    Hrodulf Prohibited from acting as an MOT until year 2050

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    It always pays to hi-pass the sats. Especially if they're bookshelves. Even if they start to lose extension rapidly under 60Hz or so, it's good to have them not attempt to play anything there, you'll get cleaner mids that way due to decreased excursion.
     
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  10. edzyy

    edzyy Rando

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    Rythmik L12 is a hell of a sub at it's price point.

    IF you're looking at Martin Logan, browse around facebook market place and craigslist. Some of these things get let go for pennies.

    I was able to snag 2 Dynamo 700's for $145 dollars.
     
  11. Poleepkwa

    Poleepkwa Friend

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    I would suggest the following routes:

    -Satellites should be high-passed. They can play louder and cleaner. The less excursion the cleaner they will sound. You will be missing out on performance if you do not.
    - The minidisp 2x4 HD is probably the cheapest way to achieve this.
    - No point to only get the minidsp, get the Umik microphone for room correction.
    - Using REW you can flatten the whole response and get the integration right.
    - Using REW too much trouble? Upgrade the minidsp too Dirac.
    - Some good earprotection against “WHOOP-WHOOP” testones.
    Alternatively look at the Dspeaker Dualcore or the more simple 8033.

    Say screw all this nonsense and get a cheap Denon/ Yamaha AVR that offers:
    - multisubwoofer leveling and phase
    - crossovers
    - easy of use
    - loudness compensation
    - streaming

    About the subwoofers:
    2 subs are good if you place the same front side of the room than your speakers.
    4 subs are better if you can get them on the front and back of the same room.
    This is all dependent on the room you have.

    The idea is to have them symmetrically placed to get rid of phase issues between them while feeding them all the same signal. Once you get really pro you can’t start to move them around with asymmetrical placement to smooth the response more, but then you have to be able too phase align them.
     
    Last edited: Jan 6, 2020
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  12. fastfwd

    fastfwd Friend

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    +1 to this. And the filter needn't be anything complicated or expensive -- a simple RC will do the job. Just match its -3dB point to the subwoofer's lowpass.

    When I last needed to do this (coincidentally also with NHT speakers -- SuperZeros in my case), I soldered the components inside the RCA plugs at the amplifier end of my interconnects. Super clean and cheap. If you do it that way, don't forget to include the amp's input impedance in the RC frequency calculation. And also don't forget that the filters are in there, since you won't have any bass if you ever try to use that pair of interconnects with full-range speakers.
     
    Last edited: Jan 6, 2020
  13. squishware

    squishware Friend

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    This is a continuation from a post in the Nearfield thread:
    Does anyone have advice for placing a pair of matching subs in a rectangular room setup facing one short end? The desire is to eliminate room modes sans treatments.

    @purr1n Two subs is intriguing. I suppose I should place them even with the monitors in the room and feed one (left or right) channel from the Bifrost 2 into both channels of each sub or would I just feed one channel to one input of each sub? The sub has stereo inputs but not sure if I would be leaving half the wattage on the table only using one channel. The intriguing part is the idea of each sub only having to do one channel of the stereo like monoblocks and the room correction.

    EDIT: I suppose not duplicating both channels in both subs deletes the room correction aspect?
     
    Last edited: Jan 11, 2020
  14. purr1n

    purr1n Finding his inner redneck

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    Run the subs in stereo to retain the best sense of stereo separation. 70Hz is too high to run them in mono. In any event, the low bass in most recordings is going to be the same between left and right channels.

    Feed L to L and R to R. Don't worry if the subs have stereo inputs. You won't be leaving 1/2 of the gain (not power) on the table, but you will also have two subs. 0.5 x 2 = 1.0. So you will be fine.

    Room treatments don't do anything below 100Hz or even much under 200Hz unless they are the size of a mattress or sofa. People who do corner "bass traps" made of foam are really just hearing minor improvement in the lower mids, which does contribute to the quality of bass (or bass instruments).

    Room modes are difficult to get rid of. EQ that works for one position may not work in another and trying to fix nulls is next to impossible.
     
    Last edited: Jan 12, 2020
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  15. yotacowboy

    yotacowboy McRibs Kind of Guy

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    Lazy advice: plop 2 subs in front corners, run L&R stereo. pick up a Parts Express Umm-6 and REW. Run a couple 20-80hz or 200hz sweeps. Run convolution and tweak with some PEQ to taste.
     
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  16. Toolkit

    Toolkit Rando

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    Does anybody here know about mixing input sensitivities?

    I'm trying out the Mackie XR624, which doesn't have an input sensitivity selector (it's +4 dBu all the time I believe). I was going to run these monitors with a JBL LSR310S, which does have a user selectable input sensitivity, so no problem, right? Well, running my sub in +4dBu is so quiet and underpowered sounding that I think it won't be feasible. There is a negative review on Sweetwater that says "when attempting to use this with a professional balanced +4 setup is was so quiet you couldn't even tell it was active." which pretty much tells the whole truth. It's like this sub has to be run in -10dBv or it's over.

    Is there any negative aspect if you run your sub and monitors in different sensitivities?
     
  17. squishware

    squishware Friend

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  18. squishware

    squishware Friend

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    The LSR310S when paired with the 305P MKII is set +4dBu (assuming a balanced source) and the monitors -10dBv I do not see why it would be different with other monitors. Your source is Balanced +4dBu?
     
  19. Toolkit

    Toolkit Rando

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    I read before posting but the sensitivity knob is just generally a volume control, not an input sensitivity control. If you note the spec sheet, it specifies it's max SPL specifically with regards to +4 dbu input and there is no note to -10dbv anywhere. There is -10 marked, but I don't know if that is referencing -10dbV or -10dbU.

    Yes. Mackie monitors, even their lower end MR line that competes with JBL 3 series, does not have a +4dbu/-10dbv switch. Since both products specify their max SPL in relation to +4, I'm going to assume they function at +4dbu all the time. It's just that when running my sub in +4dbu (to match), it is so wimpy and quiet. I didn't expect this at all and if it was more well known (there are only a few reviews that bring this up, everybody else runs it in -10dbv), I probably wouldn't have bought this sub even with it on sale. I will need to have the sub at MAXIMUM VOLUME and then turn down the XR sensitivity a lot, unless I set the sub to -10dbu, but I'm not sure what happens when you mix inputs (-10dbv is much hotter than +4dbv for instance - will one of them clip?)

    While typing this up, I might have found my answer, but I don't like it. https://www.bhphotovideo.com/explor...humored-attempt-demystifying-10-dbv-and-4-dbu

    Here’s your practical takeaway:

    • If you’re feeding a +4 dBu signal into a -10 dBV input, you’re running hot levels into receivers not necessarily equipped to handle them. Turning the +4dBu level down is a good idea.
    • The reverse is also true; if you connect a -10 dBV signal into a +4 dBu input, you’ll want to raise the -10 dBV signal—however, beware: You will also be raising the noise-floor of the signal, which, depending on the consumer-level piece of gear, might degrade the sound.
     
  20. purr1n

    purr1n Finding his inner redneck

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    No, unless you start to get noise.

    I wouldn't put too much stock into Sweetwater reviews. Lots of dummies out there. I read that review. For someone who has "40+ years" in the business, you'd be diddling with much better quality pro gear (at a minimum for example, Dynaudio monitors powered by Crown pro audio amps and custom stereo subs each 2 x15"). You just never know, the output from the monitoring controlling might be too low, or the sub might be placed 10 feet away further back from the monitors, the sensitivity of the monitors turned way too far up in relation to the subs, etc.

    I'm always wary of people who need to rely on creds, e.g. I come from a land were Stradivari instruments are found at every corner; my mom, aunt, grandmother, and I are engineers; a musical guru taught me, etc.

    --

    I suspect the driver of the LSR310S might be a dual voice coil. If that is the case, make sure you get a splitter and feed both the L and R intputs.

    Therefore factor in extra costs for XLR or RCA splitters.
     
    Last edited: Jan 12, 2020

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