Home Theater Multiple Subwoofer Set-Up & Calibration Guide

Discussion in 'Subwoofers' started by admin, May 4, 2010.

  1. admin Audioholics Robot Staff Member

    admin
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    The goal of a serious home theater playback system should be even bass, plenty of dynamic range and smooth natural frequency response across all of the listening area for the most seamless blend. The best way of achieving good bass is by reducing the modal peaks and nodal dips by utilizing multiple subs, proper speaker/subwoofer and seating placements and setup, active equalization and passive room treatments. The key is proper subwoofer placement and setup to reduce the guess work and minimize chasing your tail to find the best settings that yield the most optimal measurable performance. This article discusses methods of proper placement, setup and measurements to help achieve the best measurable and audible results for your entire listening area, NOT just the money seat!
    [​IMG]

    Discuss "Home Theater Multiple Subwoofer Set-Up & Calibration Guide" here. Read the article.
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  2. nickboros Junior Audioholic

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    Gene,

    Very nice article. I only have one sub now, but I'm hoping in the near future to upgrade to two or four subs.

    You don't mention what the phase should be set at for the subs in the three optimal locations. For example in the four subs in corner placement are all the subs set with the same phase? In the midwall placement, with two subs, should the subs be out of phase with one another? In the 1/4 width placement on the front wall, with two subs, should the subs be out of phase?

    Thanks,

    Nick
  3. gene Audioholics Master Chief Administrator

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    Phase should almost always be set to zero for all subs. It should only be altered if its beneficial which is usually not the case. I did mention this in the article under Advanced Calibration tips.
    gene,
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  4. BMXTRIX Audioholic Spartan

    BMXTRIX
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    I didn't read the article, but just counted the words. 5,999... You are slacking! ;)
  5. skers_54 Full Audioholic

    skers_54
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    Fantastic article Gene. I've been trying to integrate two different subs into my system and this really helps. I had actually been using a similar overall method but yours is much more comprehensive and helped me figure out some stuff I've been doing wrong or wasting time with.

    Do any of the recommendations change if you have the system setup width-wise rather than length-wise (besides rearrange it :))?
  6. gene Audioholics Master Chief Administrator

    gene
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    Actually its more like 8400 words in the word document. should be the same online.
    gene,
  7. SnowmaNick Junior Audioholic

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    Gene, great article, thank you.

    I have a question on the level matching process if you don't mind?

    You mention that when measuring that you should use an equidistant measurement for all subs and that the measurement location may not necessarily be the primary listening position. Where/how exactly should one measure then? I am trying to determine if you mean measure the two/four subs and measure in the center of them, where all the subs are equidistant from the mic and you do not have to try to account for differences in mic placement. Or do you mean choose a distance from a sub to the mic and measure each sub at that distance IE: measure sub one with the mic 36" from the sub, then go to sub 2 and set up the mic 36" from that sub (lather, rinse and repeat as needed).

    If the former, what if that equidistant location is the middle of two parallel walls? Won't the walls being equidistant create some null/node/cancellation at that spot but not necessarily at the primary LP causing you to crank one or more subs erroneously?

    If the latter, is it best to measure from the sub into the room? This makes the most sense to me but I am unsure how room cancellation and distance may interact with multi subs and may be misunderstanding your advice.

    I have a couple of days off to relax next week and am looking forward to trying this methodology out. Thank you in advance and again, great article.
  8. gene Audioholics Master Chief Administrator

    gene
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    Good question. For years, I always measured at the listening area for each sub. It was a pain to match levels that way. Then it occurred to me when reading Dr. Floyd Toole's book that what matters is how the subs balance with respect to the room NOT the listening area. Remember in order to take full advantage of standing wave reduction, all subs must:
    • be level matched with respect to each other
    • be properly placed
    • play exact same mono signal (LFE + all speakers set small)

    The easiest way to measure each sub is to place the mic on the floor nearfield to the sub (within a few inches). If all your subs are single driver, then you can measure the SPL at the cone for each. You don't need to turn off the other subs if you do a nearfield measurement b/c the sound from that sub will dominate all others.

    After you level match each sub, then go to the listening area and level match the main channels to the combined sub output. Once you flatten the bass of the subs, you can even boost their combined output a few dB over the main channels if you like.

    Alternatively you can pick an equadistant point from all subs to measure their SPL individually but that can be difficult if they aren't all symmetrically placed in the room.
    gene,
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  9. gdsk39a Audiophyte

    gdsk39a
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    I have some questions. I have a rectangular room that is enclosed. I have the following subwoofers in each corner: ED A7-450, EPIK Tower, Sunfire True Signature, and 2 Def Technologies Reference stacked. The 2 Def Techs and Sunfire are hooked up to the Velodyne SMS-1. After calibration I pretty much have a smooth frequency response. I am running the subwoofers a bit hot for impact. The smooth response also includes having my front speakers set to large. They are massive Polk SDA SRS 1.2's.

    Concerning phase settings I notice that changing the phase with the Velodyne SMS-1 does affect the frequency distibution. I had to mess with the SMS-1 phase setting to get the perfect frequency response graph for my total setup including fronts set to large.

    My question is this. How do you know that you are listening to perfect bass? It sounds great to me, but could my ears be deceiving me as I have nothing to use as a reference. I can tell you the bass impact is phenomenal. All the Bass appears to be coming from my main front speaker stage. It doesn't sound bloated or distorted. Just a bit on the hot side.

    Your thoughts.
  10. xWARHOUNDx Audiophyte

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    Or you can just buy the SVS ASEQ-1

    Or just buy the SVS ASEQ-1

    I have two SVS subs and this was the best money I ever spent! I literally had a flat response in 25 minutes...would have been shorter but I wanted to do it again because I "THOUGHT" I had done something wrong because it was so easy. It is expensive but the end results are awesome and you don't have to do all the steps above!
  11. gene Audioholics Master Chief Administrator

    gene
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    You still have to:
    • follow proper placements for subs and seats.
    • properly set bass management
    • make sure all subs are playing exact same mono signal composed of LFE + all speakers set small
    • level match each sub

    EQ such as the Audyssey is a last step. It can flatten the frequency response but it can NOT reduce seat to seat variation. Only proper placement and level matching per our guidelines can accomplish that.
    gene,
  12. cmryan821 Junior Audioholic

    cmryan821
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    Gene, first off, thanks a bunch for the article. Second, I have a question regarding level matching a two sub setup. I'm using a two channel amp to power a pair of identical passive subs. In order to level match I'd only need to leave the gain on each amp channel the same correct? And if I do this for the Two Sub Midwall Placement, would I notice the sub behind me more than the one at the front of the room since I sit about 5' from the back wall and about 16' from the front wall? I'd really appreciate any info you can offer. Thanks again for the article.
  13. gene Audioholics Master Chief Administrator

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    Probably. You should check the level of each sub nearfield just to be sure. Alternatively, you can pick a point in the room equidistant from both subs to ensure they are level matched when playing them separately.

    You shouldn't perceive a difference despite your listening location as long as the Xover frequency is set at around 80Hz and not much higher.

    Good luck.
    gene,
  14. cmryan821 Junior Audioholic

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    Good deal. I really appreciate the help. Now I've just gotta test to find out if either is much better than the other.
  15. cconklin1 Audiophyte

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    great guide!
  16. scolburn Audiophyte

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    Gene,

    Thanks for completing and documenting this enormous task for us. There can be little doubt that great bass is one of the most difficult to achieve, yet satisfying when achieved aspects of home audio. Your works helps to clarify a lot, particularly the non-intuitive aspect of level-matching subs equidistant from each sub rather than at the money seat.

    First a question about optimal subwoofer positioning:
    If you can't position one of four corner subs precisely in a corner, is there a rule of thumb about how close/far from the corner still works acceptably?

    Then a couple about rooms:
    How large (%?) must an opening in a wall be before a room cannot be considered a rectangle? Does it matter where the opening is located?
  17. joebuzz Audiophyte

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    Subs

    Hi Gene,

    My name is Joseph and I am new to this forum. I read your article and i found it very interesting, but as i am rebuilding my HT, i just wanted to ask you some questions on the same article, if i may!

    My room size is 11ftx15.5ft with 9ft to the soffit. I have sold the bose speakers and decided to switch to the Jamo THX, namely the D600 in 5.2 configuration. I do not have the D600 subs as i feel that are too big for my room, and instead i have two D650 12" subs and am planning to get another two. Now comes the first problem! As my door is on one side of the room i cannot place 4 subs in each corner of the room. So how should i place them? I cannot put a sub where the door opens as it would be impossible to get inside the room. Would 3 subs work equally good or i should still get 4 subs and place the last one in the middle of the room? Should i place the four subs in the middle of each wall in my room?

    Thank you.
  18. Irvrobinson Audioholic Ninja

    Irvrobinson
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    Two glossary terms have incorrect definitions

    Nice article, but a couple of important glossary terms have incorrect definitions.

    A low-pass filter attenuates frequencies *above* a stated "knee" frequency with a specified slope. For example, a low-pass filter might be specified as 80Hz with a slope of 24db/octave, which means that frequencies of 80Hz and below pass through the filter without attenuation, but that frequencies above 80Hz are attenuated such that by 160Hz the signal level is reduced by 24db.

    A high-pass filter performs the inverse function. Frequencies *below* a specified knee frequency are attenuated on a specified slope. So a high-pass filter at 80Hz at 24db/octave would pass 160Hz signals without attenuation, but 40Hz signals would be reduced by 24db.

    The current glossary definitions are accurate only from the perspective of the satellite speakers.
  19. argiris Audiophyte

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    4 subwoofers

    dear sirs I saw a drawing with 4 sub woofers in not equal distances from the listening point,I wonder how we can have same phase from different distances
    , also the basic action comes the front of us , same must be the bass, so if we have sub woofer-s behind us we will have bass from wrong direction , so we will have a bass wave front of us and another behind us.
    Kind rgrds
    argiris
  20. scolburn Audiophyte

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    Choosing between two 4 sub locations.

    Hi Gene,

    Which of these 4 sub locations is likely to provide the most even response? Max output?

    1. One each at the 1/4 & 3/4 points of both front and back walls.
    2. Two each at midpoints of front and back walls.

    Many thanks,

    Steve

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