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Thread: Time aligning subs to main speakers

  1. #1
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    Time aligning subs to main speakers

    Iím after some advice on how to think about t time aligning subwoofers to main speakers. Two papers that have informed my thinking are the http://www.acousticfrontiers.com/gui...utm_source=CTA and http://www.soundoctor.com/whitepapers/subs.htm. The latter puts forward a case that the main speakers need to be delayed to cater for the delay common to subwoofers and this is a model that Iíve used with some success. My question though is whether, from a theoretical viewpoint, the delay should account for just the delay inherent in subwoofers or also account for the different distances from the listening position. The latter model sees, in the case of a distant subwoofer, the main speakers delay account for the additional travel time to the listening position as well as the inherent sub phase / EQ delay which makes sense. That said, with a set-up that is just focused on delaying the main speakers to account for the inherent phase / EQ delay in subwoofers all the different bass sources would excite the room modes / pressurise the room at the same time which also seems like a reasonable objective. What, from a theoretical viewpoint, is the right answer?
    Music System Source: CAPS Zuma PC / JRiver | DAC: ExaSound e18 | Cross-Over: JRiver Convolution using Acourate Filters | Volume Control: MSB MVC-1 | High Pass to First Watt F5 & Unity Horns | Low Pass to Perreaux 6000B & Sealed AE18H+ Bass Bins
    Family System Source: CAPS Zuma / JRiver, AppleTV, TiVo | DAC: Lite-DAC83 | Pre-Amp: Audio Note | Power Amp: Nacquadria AEON | Speakers: Gallo Strada 2 | Subwoofers: Various and changing

  2. #2
    Quote Originally Posted by zydeco View Post
    I’m after some advice on how to think about t time aligning subwoofers to main speakers. Two papers that have informed my thinking are the http://www.acousticfrontiers.com/gui...utm_source=CTA and http://www.soundoctor.com/whitepapers/subs.htm. The latter puts forward a case that the main speakers need to be delayed to cater for the delay common to subwoofers and this is a model that I’ve used with some success. My question though is whether, from a theoretical viewpoint, the delay should account for just the delay inherent in subwoofers or also account for the different distances from the listening position. The latter model sees, in the case of a distant subwoofer, the main speakers delay account for the additional travel time to the listening position as well as the inherent sub phase / EQ delay which makes sense. That said, with a set-up that is just focused on delaying the main speakers to account for the inherent phase / EQ delay in subwoofers all the different bass sources would excite the room modes / pressurise the room at the same time which also seems like a reasonable objective. What, from a theoretical viewpoint, is the right answer?
    You may want to speak to the guys at Lyngdorf and DEQX. I have a good friend, and he uses a fully active system using a computer as the crossover and passive subs (AMPS DRIVE THEM SEPARATELY) the software he uses does account for the issues that you raise it is called Accurate
    http://www.audiovero.de/en/acourate.php

    You really need to be in the digital domain to use this at its best as I understand it - the results are excellent but you really need to read up on the software functions. and 'know your onions' so to speak.

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    In my home theater systems that I have had over time, I discovered a few interesting things:

    1) Putting the subs at the same position as the front channels is not always optimum. One of the best results I got was the sub at the listener position or nearby, and inverted phase from the mains. The sub always appeared acoustically as if it was between the front speakers.

    2) Directing the sub at an angle into a fireplace hearth was beneficial. It activated the room modes less and integrated into the space better.

    Steve N.
    Empirical Audio

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    VIP/Donor [VIP/Donor] Folsom's Avatar
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    The subwoofer frequencies it produces has wavelengths so long that it generally can be nearly anywhere, depending on the crossover point. Here's distances from the main speakers based on frequency.

    200hz - 5ft
    100hz - 10ft
    80hz - 15ft
    60hz - 18ft
    40hz - 27ft
    30hz -36ft

    So you can see, it's pretty clear that depending on frequency you got some serious options. Just like with Steve, the best was not near the main speakers nor did it need to be if the frequency is low enough. The most important thing to the ear, once you find a good places that isn't riddled the nodes, is phase. Phase is what you really hear, but the room can suck out certain frequencies so finding the least node-ish spot is the goal. That issue is why Duke came up with the Swarm, which is 4 subs placed about the room to eliminate nodes.
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  5. #5
    Isn't a major problem ethos and reverberations with bass?

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    VIP/Donor [VIP/Donor] Folsom's Avatar
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    That is too broad of a question for me to get. Reverberations? Like a picture on the wall rattling? That's an easy fix compared to building a new room.
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    Quote Originally Posted by Folsom View Post
    The subwoofer frequencies it produces has wavelengths so long that it generally can be nearly anywhere, depending on the crossover point. Here's distances from the main speakers based on frequency.

    200hz - 5ft
    100hz - 10ft
    80hz - 15ft
    60hz - 18ft
    40hz - 27ft
    30hz -36ft

    So you can see, it's pretty clear that depending on frequency you got some serious options. Just like with Steve, the best was not near the main speakers nor did it need to be if the frequency is low enough. The most important thing to the ear, once you find a good places that isn't riddled the nodes, is phase. Phase is what you really hear, but the room can suck out certain frequencies so finding the least node-ish spot is the goal. That issue is why Duke came up with the Swarm, which is 4 subs placed about the room to eliminate nodes.
    I'm not too sure what, specifically, you're trying to say here (apart from the bit about the swarm which I do get). Is it that travel time to the listening position is unimportant or ...?
    Music System Source: CAPS Zuma PC / JRiver | DAC: ExaSound e18 | Cross-Over: JRiver Convolution using Acourate Filters | Volume Control: MSB MVC-1 | High Pass to First Watt F5 & Unity Horns | Low Pass to Perreaux 6000B & Sealed AE18H+ Bass Bins
    Family System Source: CAPS Zuma / JRiver, AppleTV, TiVo | DAC: Lite-DAC83 | Pre-Amp: Audio Note | Power Amp: Nacquadria AEON | Speakers: Gallo Strada 2 | Subwoofers: Various and changing

  8. #8
    [Industry Expert] Addicted to Best! DaveC's Avatar
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    Quote Originally Posted by zydeco View Post
    I'm not too sure what, specifically, you're trying to say here (apart from the bit about the swarm which I do get). Is it that travel time to the listening position is unimportant or ...?
    At those frequencies it's just not a big deal, we are much less sensitive to time delays at sub frequencies, and you'll do more damage trying to delay the main speakers vs solving a non-existent problem. Adjusting phase is also adjusting time, this is worthwhile to do with the subs but leave the mains alone. IMHO...
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  9. #9
    VIP/Donor [VIP/Donor] Folsom's Avatar
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    Quote Originally Posted by zydeco View Post
    I'm not too sure what, specifically, you're trying to say here (apart from the bit about the swarm which I do get). Is it that travel time to the listening position is unimportant or ...?
    Those are distances within the "time alignment" for the frequencies, or rather the spectrum of distance where phase can be set so our ears will percieve it correctly. Past them our ear will hear a seperation in the music, not related to direction. Above 80hz we can hear directionality as frequency goes up, so that is something to account for depending on the range being played. Below 80hz you get vast distance capability for placement because in most rooms there isn't anywhere out of time alignement, and you cannot sense direction of it either. The last bit is phase, which we are super sensitive to, but all subwoofer amps have adjustable phase.
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    Quote Originally Posted by DaveC View Post
    At those frequencies it's just not a big deal, we are much less sensitive to time delays at sub frequencies, and you'll do more damage trying to delay the main speakers vs solving a non-existent problem. Adjusting phase is also adjusting time, this is worthwhile to do with the subs but leave the mains alone. IMHO...
    X2 agree. If space allows another option is to place the sub(s) closer to the sweet spot than the mains and adjust phase (think someone earlier had a similar opinion).
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