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Is 2 subs better than one

Discussion in 'Subwoofers' started by petrolhead, Nov 20, 2003.

  1. petrolhead

    petrolhead
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    Been discussed a while back but in the light of new makes and models ie SVS and Velo DD range I was wondering.

    So if one was to upgrade would they be better another of replacing with something bigger/more expensive.

    ie User has a CHT15. Should they:
    A) Sell the velo and but an SVS or better Velo
    b) Buy an other velo.

    Just an interesting thought
     
  2. Ian J

    Ian J
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    I don't think that one can generalize as each individual's circumstances are different.

    In your post you gave as an example the fact that the user currently had a CHT-15 (what a co-incidence, so do you :D ) but you neglected to mention the budget available for changing the subs which must have a major bearing on the answer.
     
  3. petrolhead

    petrolhead
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    LOL :p

    I somehow thought you would be the first. Yes a coincidence my friend but not deliberate.

    I simply used myself as an example but would think that same goes for all.

    The budget, well I would have to say the cost of a DD15 which RRP is £2800 (Phew!)

    So Ian, would selling the Velo for say £500 and adding £2300 be beter than buying an other Velo for say £500.

    Looking at that last comment I think you answer could well be coloured so regardless of cost wich would sound better :)
     
  4. buns

    buns
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    well like for like, you could probably have 4 cht15's for one DD15.....

    ad
     
  5. Ian J

    Ian J
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    I would suggest waiting for a couple of weeks to see what esta56 says when he has replaced his servo 15 with a pair of SVS PB2 Plus subs as his position will be similar to the one that you have speculated on.

    Jase has already gone the twin sub route by selling his CHT-15 and replacing it with a pair of SVS and he seems well pleased with the results but a second view would be interesting.

    If you have read the reviews of The Event you will have noticed the rave reviews that the Genelec subs on display there received including comments like "The best bass I have ever heard" so perhaps that's another make that should be on your short list.
     
  6. SamirP

    SamirP
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    Hi PetrolHead
    Or you could sell yr velo and buy Adz's Mackie HRS120 PM3 cert Sub. £1100 sounds like a good price then add a second at a later date. Retails at £1200 so still cheaper than a DD15
     
  7. petrolhead

    petrolhead
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    Yes I saw the ad but never heard of make.

    Do you have any links Ian?
     
  8. agw_01

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    I've had this thought quite a few times.

    Just wondering, if you did have 2 subs... would you set them both to be in phase, or would you set one to be in phase and another to be out of phase?
     
  9. Ian J

    Ian J
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    The first comment I noted was here and The Beekeeper has forgotten more about subwoofers than most of us have learned.

     
  10. Jase

    Jase
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    Depends on the room. Both mine are set the same. My Dad's subs are set to the opposite of each other.
     
  11. petrolhead

    petrolhead
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    Jase

    What position, 6 and 12 o'clock?
     
  12. Jase

    Jase
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    Dad's subs phase are set to 0 and 180. The phase on my two are set to 180.
     
  13. Nic Rhodes

    Nic Rhodes
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    are you guys talking the same language, one is talking phase, the other position?
     
  14. Jase

    Jase
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    I'm talking phase! LOL
     
  15. petrolhead

    petrolhead
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    And I am talking position!

    So come on Jase (Too much sun eh?) talk position please

    You must have read my mind Beekeeper as I have just sent u a pm
     
  16. Jase

    Jase
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    Not enough sun!:D Ok, position. I have one of mine between the front right and centre speaker and about a foot in front of them. The other is placed about 2ft directly behind my listening position. Dad's two are placed outside of the front left and right speakers, one either side.
     
  17. petrolhead

    petrolhead
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    so 6 and 12 o'clock for you then :clap:
     
  18. Jase

    Jase
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    Or 6 and 1 o'clock if you want to be picky.:D :rotfl:
     
  19. petrolhead

    petrolhead
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    :)

    Smart ....
     
  20. Smurfin

    Smurfin
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    Individual settings are a moot point, as they'll work completely different in different rooms...

    As for my feelings on two subs, I really HAVE noticed a difference. I added another Servo 15 to my existing one (I'm soo glad I made that decision when I did and @ £400 it was a no brainer!). Has it resulted in more bass? Nope, but what it has done it allow me to drive them at reference level (i.e bloody loud), with the individual subs volume controls lower than when I had just one. And the result?

    More db @ lower frequencies, and less distortion. Is that noticeable? Absolutely yes! I've found that adding another Servo, and BFD'ing them both has resulted in bass which is silky smooth, tight and clean yet able to plummet the depths and shake the entire room:)

    2 subs are definately better than one, but you need to play around with the setup, and you'll need an SPL meter and some test tones.
     
  21. Nic Rhodes

    Nic Rhodes
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    quality is the key not quantity, the Harmon Kardon web site has an interest powerpoint presentation on multiple subs which explains the benefits far better than any of us can
     
  22. petrolhead

    petrolhead
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    Beekeeper, do you have a link?

    Smurf, I have test tomes, SPL and have just bought BDF.
     
  23. lowrider

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    Two subs eliminate some ressonances, so they sound a lot smoother, plus bass fills the room better, whenever I disconnect one of them, I can hear the other, instead of just the room full of bass... :rotfl:

    Sorry for the confusing English... :blush:
     
  24. Ian J

    Ian J
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  25. Nic Rhodes

    Nic Rhodes
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    some questions answered and some more general stuff for everyone who is interested in dual subs


    http://www.harman.com/wp/index.jsp?articleId=default


    for HK White papers

    try

    Subwoofers: Optimum Number and Locations By Todd Welti

    http://www.harman.com/wp/pdf/multsubs.pdf


    Sort of a power point presentation that gives some excellent support for multiple subs. There is a technical appraisal of the advantages. Briefly they like 4 subs a la Steve but say 2 isn’t much different but 2 is a serious jump from 1. It shows why with a decent analysis

    there is other interesting stuff there as well.

    I was frankly amazed at how much better two subs can be than one but I say the same about low distortion subs as well. You all know this though. If you have the perfect, dedicate AV room, one is probably fine. Then it gives this wonderfully flat bass response. However most of us in the real world have our kit, with the approval (or not in case of dual Servo15s!), of her in doors. Here, in this situation, I think two subs works really well.

    All rooms have more nodes and troughs, these are dictated firstly by the three primary dimensions (H, W, L) and then 'modified' by what is in the room. You basically end up with a 3 dimensional plot of peaks and troughs (does anyone know an easy way of plotting this out in 3D?). Where we sit in the room effects how we 'interact' with these peak and troughs

    Now there are several things that need / can be done.

    1. Set up you subs correctly in the room first, in there best position, whether a single sub or two. Do the physiscal positioning first
    2. Apply any room acoustics stuff next, I mean Auralex, Grammas, bass tubes etc etc
    3. Now is the time to apply electonic signal manipulations to your signal Eq. Room eq is not the be all and end all but it is a very useful tool (BFD / Tag / Meridian).

    3 should be the last thing you do but as it is cheap it often gets done first. It is not a solution to problems, merely helps them and should be applied after you have the basics done correctly first. I can fully understand why people play with BFDs though, it is fun and cheap. Just don't use it to solve fundamental set up problems first.

    Though why is a flat response the best for sound? Everyone aims for really flat response, is it really the best sounding? Are your ears as flat as the microphone in their response? What about 'weighting' your flat response?

    3 can be divided into the following categories:

    A Frequency and level domain correction (Parametric Equalisation)
    The response of the room is analysed in terms of level vs frequency. The direct sound from the monitor (be it a sub or satellite or whatever) is then adjusted in terms of it's frequency response so that the sum of the direct output and the reflected output is notionally correct. Behringer Feedback Destroyer, TMREQ, Merdian (with twaeks) in fact it is an AD 'library' code so is available to all SHARC devices!! Most devices are in this category. It is easiest to do in analogue or digital domains.

    B Time, frequency and level domain correction (Dynamic Equalisation):
    This is a more complex method, which assumes (correctly) that different volumes at a fixed frequency will have more or less of an effect on the reflected sound. Otherwise it is very similar to the above methods. Behringer UltraCurve DEQ2496 cn sort of do this

    C Active room correction, as used by TacT:
    This adjusts the output from the monitor to not only correct for errors in the level of frequencies, but also to cancel out any reflections which cause group delays and phase shifts within the signal as it arrives at your ears. It is room and speaker dependent. Despite peiople claiming it takes silly processing power, a peep under the Tact hood might indicate otherwise ;)

    Please bare in mid that each of the 'after market mods (except the Tact system) is geared to where you listen to music, change this and the whole systems starts to loose it effectiveness

    With dual subs It doesn't go deeper per se, it isn't necessarily 'superior' in the conventional sense. It just makes every thing that much easier. You should be able to get an additional 3 to 6dB output, or put another way at your normal listening levels the sub has to work that much less (thus giving low distortion etc). It is sooo much easier flattening out room 'humps' as well. It deals with some of the fundamental first that can then be tweaked by applying 2 and 3 to your system LATER

    Positions that seem to work well are by L and R speaker, 12 and 6 o'clock and 3 and 9 o'clock. Phase will need to be adjusted accordingly (no clear rules here)

    So what do dual subs do?
    They reduce the load on each sub all other things being equal. 3dB is the equivalent of doubling electrical power, 6dB is quadruppling. Dual subs will give you between 3 and 6dB acoustic gains, abit like a spinal tap volume control ;)
    This means at the normal level, the sub can go a bit lower and still remain out of that nasty distortion region.
    They can go that little bit louder (do you ever want this?)
    They 'load' the room better giving a smoother response
    They allow a 'speading' of cost of purchase of subs
    Two subs could be easier to hide (smaller)
    They are cool boys toys :)

    Do they work everywhere?
    Yes I think they do, their effectiveness varies however. Really difficult rooms (square) are always tricky to get working correctly, two subs certainly 'help' but there are more fundamental issues that need to be dealt with here first. More normal rectangular rooms certainly benefit, IF YOU CAN PUT THE SUB IN THE BEST POSITION. Remember many of you out there have these things in living rooms / loughes etc. The best location might not be very convenient! The best I saw was basically behind the door!! In fact most of us don't have subs in 'optimum' locations as it is in the way. Bare this in mind please. We NEVER talk about this here. Even dedicated rooms like mine are a compromise to some extent, what happens if the sub should be in the place where the prokjector HAS to stand?

    without jumping I would generally prefer two smaller subs than one slightly larger subs assuming they have broadly similar distortion patterns. I feel this works better

    Bare in mind I am of the view that room acoustics makes more of difference to sub performance in a room than whether you have SVS / Servo / Velodyne (substitite your favourite mine is bigger than yours sub here). Get the positioning and acoustics correct first, IT IS IMPORTANT.
     
  26. lowrider

    lowrider
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    :clap: :clap: :clap:

    Mine, golden ratio, 15´x 9´x 24´:

    [​IMG]
     
  27. Apocalypse

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    I'm glad Beekeeper mentioned that 2 subs don't always benefit some rooms because they didn't do squat in my room which is small and has equal dimensions. IMO a large and powerfull sub in small room is preferential to 2 smaller subs in the same room. So going back to the original question, if you had a choice of a DD15 or twin SVSs I'd choose the DD15 if you have smallish room. My sub loads the room so well you have no idea where the sound is coming from. Beekeeper also mentioned room treatments, I can whole heartedly endorse this course of action, bass traps and sound diffusion made a greater improvement in sound quality than when I switched from a £500 sub to a £2600 sub.
     
  28. Nic Rhodes

    Nic Rhodes
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    Mudge made a very interesting suggestion to me the other day. Build a completely square room and get a honking great trough though L, W and H all being the same. Then you simply remove this with a BFD or similar and your problem is solved  There is something in it I think. If you have a square room (lucky sod Lowrider) then I think room Eq might be very beneficial (as would acoustic treatments) though I would still go dual but hey that me :)

    I still hold that you can get bigger differences to sub performance by acoustics rather than upgrading subs to the latest flavour of the month. I think the ‘weighting’ we put on this currently is all wrong, we currently have it back to front.
     
  29. lowrider

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    Even my golden ratio room with two subs still has a peak at 48hz, (according to the spreadsheet it is the second order of the room lenght modes), that the Krell handles very well with a Notch filter at 50hz...

    Of course TMREQ would do it better with any room... :rolleyes:
     
  30. petrolhead

    petrolhead
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    So maybe I have done the right thing and bought the BFD and maybee some well positioned wall carpets.
     

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