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Home Theater Calibration 101: Speaker Levels, Distances and Subwoofer Phase


This blog article will teach you about home theater calibration – in particular how to calibrate the audio side of your home theater pre-processor (pre-pro) or audio visual receiver (AVR). I’m not going to cover the video side.

The three basic elements of audio calibration in home theater setup are:

  • Speaker and subwoofer levels
  • Speaker and subwoofer distances
  • Subwoofer phase

Whilst many modern AVRs provide automated setup routines, such as those by Audyssey, the results can be variable and in many cases better sound quality can be achieved by manually setting up your system. For the purposes of this discussion we will assume that you are using the ‘industry standard’ THX 80Hz crossover between your main speakers and your sub. Sometimes you can get better results by using a different crossover frequency such as 60Hz, particularly if your satellite speakers are physically large, but exploration of this is beyond the scope of this article.

For best results we are going to use some special home theater calibration software – the XTZ Room Analyzer II Standard – to setup your system. The XTZ is a versatile acoustic measurement package that contains both the hardware (microphone, soundcard, cabling) and the software required to calibrate your home theater. There are four pieces of functionality that XTZ Room Analyzer provides that we will use to complete the calibration:

  • Sound Pressure Level (SPL) meter with C weighting and slow averaging to set speaker and subwoofer levels
  • Delay alignment tool to set speaker and subwoofer distances
  • Real time analyzer (RTA) to set subwoofer phase / polarity
  • Frequency response ‘Room Analyzer’ with 1/3rd octave smoothing to check subwoofer phase / polarity

Until recently we would have had to use an expensive collection of hardware to calibrate your home theater audio, and even then we wouldn’t have been able to do as good a job as we can today with the modern acoustic measurement packages. In particular the proper setting of subwoofer distance is not as straightforward as just measuring the physical distance from listening seat to sub as we will explain.

Speaker & subwoofer levels

The first step is to set the sound pressure level ‘trim’ for individual speakers in the AVR. We need to do this because quite often each speaker – even from the same manufacturer – has a different sound output or sensitivity for a given electrical input. I often find that surround speakers are less sensitive than left, center and right (LCR) speakers.

To setup the trims you will need to find out how to get into the speaker level setup screen in your AVR. It is quite often called ‘Speaker Levels’ or ‘Channel Levels’. There will be a command to start a pink noise type test tone signal. Once this is playing you should open up the XTZ Room Analyzer software on your computer and look at the left of the screen where you will find the the SPL meter section. The XTZ does not need to be connected to your audio system at this point. Set the controls to ‘C-Weighting’ and ‘Slow (1s)’ (see screenshot for the location of these controls). The process is then to go through each of the speakers (including the subwoofer) in turn on the AVR and change the trims such that the value next to the ‘LCS’ (i.e. Level with C weighting and Slow averaging) is 75dB for all speakers. The SPL readings from the XTZ are quite accurate. I checked them against my calibrated IEC Type II SPL meter and they were within 1dB and so can be relied upon.

Screenshot of XTZ Room Analyzer II Standard edition showing SPL meter with averaging and levels set correctly and where to read the SPL level

Speaker and sub distances

The next step in the process is to set speaker distances. For all speakers except the sub this can be done quite accurately by using a tape measure or laser distance meter. So go ahead and measure the distances and put these into your AVR – they are often found in a menu called ‘Speaker Distance’ or just ‘Distance’.

What we will do now is check all of these settings acoustically using the unique Delay Finder capability in XTZ Room Analyzer. With your left, right and surround speakers there will typically not need to be any additional delay changes – the physical distance measured is accurate enough to align the distances. With the subwoofer, however, that is generally not the case. Nearly all subwoofers introduce some additional acoustic* delay that must be compensated for – i.e. the physical distance is not the same as the acoustic distance. Using the Delay Finder you can compare the sub to a reference channel – I use the center – and determine the additional delay that needs to be added.

* here I use the term acoustic to refer to the sum of all delays in the subwoofer. These include DSP related delay (from A/D, processing and D/A conversions), electrical (from equalization and associated phase shift) and acoustic (delay caused by ports).

Typically you will find that all of the main speakers need to be compensated between 3ms and 10ms to align them with the sub. Remember that sound travels 1.1ft in 1ms. My JL Audio F112, for example, has 4ms of additional acoustic delay relative to my mains. In an AVR this is accomplished by setting the distance for the sub to be 4.4ft GREATER than the mains. The AVR will then delay the mains to align them with the sub.

Open up the XTZ Room Analyzer software and go to the ‘Full Range’ tab. Connect the output of the XTZ to the center channel analog input (or whichever input corresponds to the reference speaker you are using) of your AVR. TURN OFF THE SUB, so you are just getting a measurement of the speaker. Take a measurement of the center speaker and store the result as an ‘Overlay‘ section by hitting ‘1’ (see screenshot below).

The next step is to take a measurement of the sub only. TURN ON THE SUB, AND UNPLUG THE REFERENCE SPEAKER, so you are just getting a measurement of the sub. Once you have taken this measurement you will see the frequency response of the center and sub channels in the graph. You can now use the Delay Finder to check and adjust acoustic delays as necessary.

To use this function press ‘Align Delay’ and then ‘Auto Align’ (see screenshot below). Room Analyzer compares the two measurements and determines the delay that needs to be applied to put the two in alignment. 99% of the time you will find that delay needs to be added to the ‘Overlay 1 Measurement’ i.e. the center channel. Since we can pretty much always rely on the physical and acoustic measurements being the same for all channels except the sub we can add this delay to the center, left, right and surround channels.


Screenshot from XTZ Room Analyzer II Standard – the unique Delay Alignment tool automatically identifies the best time delay to apply to the main speakers to align properly with the sub

Subwoofer phase

The process we will use to correctly set subwoofer phase is the same as that covered in our article Subwoofer Integration for Stereo Systems.

Many people get confused by polarity and phase. The thing to remember is that both controls are adjusting the same thing. The phase control is normally variable between 0 and 360 and the polarity has two settings 0 and 180. Both controls are changing the phase at the crossover frequency. If you set polarity to 180 and phase to 0 you’d get 180 degrees of phase shift at the crossover. If you set polarity to 0 and phase to 180 you get exactly the same result. So they can be used interchangeably.

The method we use to set phase involves using a RTA. Go to the RTA tab in the XTZ Room Analyzer sotware and press the ‘Measure‘ which is found towards the top right of the screen (see screenshot). Now, with the RTA playing pink noise, slowly adjust the phase controls on the sub to get the maximum SPL at the crossover frequency. When you find the phase setting that produces the most SPL at the crossover frequency (80Hz in this case) it means that the sound waves from the sub and mains are properly in phase and not causing any phase based cancellation.

RTA screenshot from XTZ Room Analyzer II Standard – we are aiming to get the 80Hz SPL as high as possible i.e. most in phase

Once you’ve found this point a quick check should be done using a 1/3rd octave frequency response measurement. Go to the ‘Room Analyzer‘ tab, and take a measurement of the sub and center channel measured together. Once you have this save it as an overlay by hitting ‘1’ in the ‘Overlay‘ section. Now flip the polarity switch on your sub which will change the phase relationship 180 degrees. This should result in a nice deep null at the crossover point. So with the polarity flipped take another measurement and compare the two. If the new measurement does not have a symmetrical or deep null then keep on tweaking that phase control! The chart below shows the mains and sub measured together with the phase set correctly (blue line) and 180 degrees out of phase (green line).

In phase / out of phase – blue line is response of mains and sub when they are in phase. Flipping the polarity switch for a check gave the green line. The deep symmetrical null is what we expect when the phase control is set correctly.


In this blog article from Acoustic Frontiers we’ve shown you how to use an acoustic measurement package such as the XTZ Room Analyzer II Standard to calibrate and setup the audio side of your home theater system. The process described in this article is what I think of as a ‘basic calibration’. Acoustic Frontiers has developed a much more indepth calibration process which is available as a consulting service within the SF Bay Area and beyond – you can find the full home theater calibration checklist here and details on our calibration process here. Thanks for reading, and if you have any comments or suggestions on how to improve the process please leave a comment! Nyal / Acoustic Frontiers

40 thoughts on “Home Theater Calibration 101: Speaker Levels, Distances and Subwoofer Phase”

  1. Hi Nyal

    1.Which graph in the XTZ Full Range tab does the ear hear in the listening position?

    2. Which tab is best used for EQ full range in XTZ?

    Thank you

  2. Hi Nyal

    To use the Align Delay for time aligning the left main speaker + left sub with a receiver crossover set to 80hz and the subs crossover disabled (letting the receivers control the crossover).

    Would it be advisable to leave the receivers crossover at 80hz and measure, then measure the sub with the crossover disabled or set the subs crossover to 80hz as well.?

    Appreciate any comments

  3. Hi Peter, the crossover should ALWAYS be disabled on the sub if you are using the crossover in your AV receiver / pre-pro, otherwise your sub will have a 'double rolloff', since there will be a rolloff applied in the AV receiver / pre-pro and another by the sub.

  4. Hi Nyal thank you.

    Phase vs Distance settings

    As i bellieve phase setings effect the crossover frequency so what does distance effect?

    Appreciate your help to understand

  5. Hi Nyal

    When setting up dual stereo subs (one sub for each main speaker) is it strange to have extremes for each channel e.g. left sub and main, to have a distance of 0 meters for the sub and the left main to add 2 meters to the the already 3.50 meters, but with the right is suggesting to add 7 meters to the already 3.45 meters and leaving the right sub at 0 meters.

    Doesn't this now through out the mains distance delay?

    Thank you

  6. Hi Peter

    The left and right should always have identical delays, the subs can have different delays if your room is asymmetrical or placement is asymmetrical. XTZ tries to find the flattest frequency response overall.

    I'm not really a believer in stereo subs, and prefer to sum to mono and use a lower crossover point for two channel such as 50Hz. This allows you to place the subs separately to the mains for beneficial overall smoothing of the bass response and potential room mode cancellation.



  7. Hi Nyal thank you.

    I am trying stereo subs currently.

    All the original settings were set by the receiver in auto setup.

    I re-did the measurement and this time i ended up adding to the mains (left main original 3.5meters, now 5.55 meters, right main original 3.45 meters, now 5.70 meters).

    The subs were originally set to 7.25 meters, (i changed this back to 0 for the measurements) and XTZ suggested only a change to the mains. Does this sound right?

    When i measure both speakers combined with the Room Analyzer there is a null, but when i measure the left main and sub seperately the null isn't there as much. I change the phase of the left sub to reverse and the null appears, but when measured combined the null appears. Which phase is correct?

    For mono subs do i measure the 2 x mains combined, then the 2x subs combined, and then what do i add to e.g. 2 meters to both subs?

    Thank you very much

  8. Hi Peter

    1) Yes, adding delay to the mains rather than the subs is normal.
    2) Nulls can appear when both speakers are played together, though typically this is at a different frequency than the sub crossover.
    3) For mono subs, measure the L/R combined, then the subs combined.



  9. I have a quick question. I’ve read a couple of you articles regarding
    getting the sub and mains in phase with each other. Do I need to play pink
    noise from the mains and sub at the same time to measure the best response
    at the crossover frequency, or do I just measure the sub. My amp (Onkyo
    Thx) plays pink notice per Chanel, not simultaneously. Do I need a special
    disc to play pink noise thru my system for this?

    I’m using an iPad spectral analyzer to measure SPL

    1. The pink noise played back by most AVRs and pre-pros is not suitable for
      subwoofer integration. The signal is most often band passed pink noise
      (essentially pink noise with the top and bottom octaves filtered out) that
      is designed to be used for setting levels, not for integrating subs. You
      would need to find a source of pink noise to use for the calibration. I am
      not familiar with the calibration discs on the market but a search might
      reveal one that has the pink noise on it. If not then the XTZ Room Analyzer
      Standard edition provides an inbuilt signal generator that produces pink
      noise. You can plug the XTZ into your AVR or pre-pro via a two channel
      analog input and set the surround mode to Dolby Pro Logic II. With this
      done the sound will come out of the center speaker and subwoofer. A two
      channel input should generally be used rather than a multi-channel input as
      most multi-channel inputs bypass the DSP section and hence any level or
      distance adjustments. Using the two channel input you will be able to see
      changes in the subwoofer integration as you adjust the distance setting in
      the AVR or subwoofer phase control.

    1. Hi lukevw, thanks for reading. I’m not sure what you mean by your question “can you use the pink by in phase at home”, maybe can you please try writing it another way?

  10. Hi Nyal: In full-range measurement, the measured distances is a negative values(-0.044m), I had repeated again and again, but got the same results. Is there anything I do wrong? Best regard.

    1. That would mean you need to delay the sub relative to the mains. 0.044m is an extremely small delay (think about the time it takes for sound to travel that distance), and in terms of sub/mains integration not one that you would worry about.

  11. Hi peter
    I have some confused that after Full range calibration of the main speaker vs sub. I found the result as follows;
    – current measurements = 5.40ms(1.85m)
    – overlay 1 measurements = 0.00

    What should I do with the compensation of delay time to input into my AVR.

    I use MRZT 7009.

    1. Assuming “current” measurement is the sub and “overlay 1” is center, then that result means you should add delay to the sub. So set the sub distance to be 1.85m less than it currently is set to.

      1. Thank for your feedback, please clarify more “ add distance to the sub@ 1.85m”, I’m not sure that total distance of subwoofer should be set to 1.85m or reduce 1.85m from current distance.

  12. Maybe I’m missing something here, Nyal, but it sure seems like you are instructing people to add delay to their mains in order to sync with their subwoofer(s). Or, as you told psuedo, to subtract from their current sub distance setting the correct distance measurement in XTZ.

    Not sure if you’re familiar with Barry Ober but he runs JL Audio’s support. He’s quite the accomplished engineer in his own right. As he explains here, AVRs and pre-pros actually treat the distance settings a little counter intuitively. But it makes sense once you think about it.

    If I set my sub to 20 feet and my mains to 10 ft what is being delayed by such settings? Hopefully not my sub!! If the delay were added to the sub it would actually double the already late signal coming from my sub resulting in even muddier bass.

    Furthermore, it isn’t just a matter of a subwoofer’s acoustical delay. Some of the delay is due to DSP and other circuitry that the signal has to cross before even being converted into acoustical energy. For example, I have a Power Sound Audio XS15 subwoofer and I know from talking to the manufacturer that the DSP alone adds 2.5 ms. But I know from actual measurement that there’s another 5 ms of delay even when the sub is directly next to the reference speaker. That’s 7.5ms of total delay (electrical, DSP processing, mechanical, acoustical).

    Assuming my mains are set to 10ft, I simply add the delay (7.5 x 1.1) to 10. So, that gives me a subwoofer distance of 18′ 3″ (10 + 8.25). Given that this is the longest measurement of all the speakers, the AVR then delays ALL OTHER speakers relative to its proximity to the sub.

    Having a Pioneer receiver with MCACC Advanced room correction I know that when I let it setup the AVR automatically it measures the distance of the mains within a couple inches of reality and the sub is usually farther than actual distance. It’s not right on, because MCACC isn’t perfect, but the concept holds.

    Again, maybe I’m misunderstanding what you wrote and, if so, feel free to correct. But I see no other way for the distance settings to work properly.


    1. Hi John

      It’s been a while since I wrote that article and I saw that one of the sentences talking about delay / distance was confusing. That must have made you think we had things backwards. I’ve now changed this sentence so hopefully it’s clearer.

      I also added a note to clarify “acoustic” delay. I was trying to keep the article simple, and so used acoustic as a generalized way of referring to all delays to the sound coming out of the subwoofer, but yes, you are right, there are many different causes of this delay. It’s actually even more complex, because the delay changes depending on what crossover frequency you use (since phase shift due to equalization and possible phase shift due to porting).



  13. Hi Nyal when doing time align with the XTZ alignment tool is it best to:

    1. Have all the crossovers set or do I set everything to full range including the sub?
    2. Add the value to the sub or mains?
    3. Only have one main measured with the sub?


    1. 1. crossovers set, as they will cause phase shift and therefore change the optimal time alignemnt
      2. depends on what XTZ tells you (it can indicate a delay to either first or second measurement, this is explained in the manual)
      3. yes, typically I would recommend the center speakers, as that is most important for HT

      1. Hi Nyal thank you
        2. If the change was on the centre wouldn’t that make the mains wrong too if the centre was setup all around?

        Thanks again

  14. Hello Nyal
    What do I need to compensate? Subwoofer relative to the main speakers or main speakers regarding the subwoofer?
    Thank you

    1. Normally it is delaying the main speakers relative to the subwoofer. Sound typically takes longer to come out of the subwoofer relative to the main speakers due to most subwoofers having latency due to A/D, DSP and D/A conversion in addition to the time required to get the heavier subwoofer driver moving.

  15. Hi Nyal does the Distance Delay in the XTZ Room Analyser work for full range e.g. left and right main speakers?
    Mic orientation for surround speakers for measurements for the Version 1 (gooseneck) mic should be 90 degrees?
    If so 90 degrees should be for main speakers as well?

    Thank you

  16. Hi Nyal
    I am setting twin Rel Strata 5 subwoofers that are in front corners outside of speakers. Most of the time it is used for 2 channel music. The receiver is a Yamaha Z9 which is great on 2 channel. This was their flagship. The RELS have been setup in high level. The RELS have phase 0 or 180. Would I use the same as this article to calibrate?

    Thank you

  17. Hi Nyal thank you.
    With phase in general, is it time aligning at a specific frequency?
    Trying to understand.

    Stay safe.
    Thanks again
    Thanks again

  18. Hi Nyal
    I have started to read a little on time aligning and phase aligning and getting a bit confused.
    Does XTZ delay alignment tool align time or phase or both?
    Which one should be used?

    Thank you

    1. Time and phase are two sides of the same coin. For example, 180 degrees of phase at 50Hz is 10ms.

  19. Hi Nyal thank you.
    For distance setting above you say to output of the XTZ into the sub input, is that directly to the sub or use AVR?
    I am getting regular incorrect readings (hope that makes sense).
    The L&R main speakers have a delay of 3.50 metres & 3.45 metres, sub delay 0.30 metres (lowest setting) , xover set to 100 Hz (trying different setting)
    I seem to be getting consistent reading from the XTZ of an extra 6.71 meters to be added to the main speakers. When I do sweep measurements there isn’t good SPL summation though the xover region.
    Does this make sense to you?
    Thanks again

      1. Hi Nyall thank you.
        Do I need to set the reference speaker to full range in the AVR when the xover is going to be 100hz? Sorry I thought to measure as it would be played, 100hz setting in the AVR, turn the sub xover up as high as possible. Getting bit confused.
        Ok will do measurement with connection directly to the input of the sub.

        Thanks again

        1. Hi Peter, you are right. I corrected my earlier comment from May 13. You should be measuring via the AVR with bass management settings enabled as you are using them. I made some corrections to the process that is written up in the blog post.

  20. Hi Nyal, please see last post.
    This is for my other setup, I am using the bass management,
    speakers set to small.
    speakers xover 100hz (or might change to 80 or lower).
    sub xover disabled.
    Hope this makes it clearer.
    Please can you explain why to use the input directly into the sub, instead of going through the AVR. Not questioning you at all just trying to understand.
    Maybe this is where Im getting a bit confused because if the sub xover is disabled and plug directly into the sub, with the xover disabled that means the sub will be playing full range for the measurement.

    Thank you

  21. Hi Nyal thank you for clearing up.
    I measured the sub only with a 100hz crossover and the graph showed a roll off at 55hz Anechoic and 100hz Raw.
    Is this a acoustic issue?

    Thanks again

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