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Thread: Subwoofer myth or misunderstanding?

  1. #11
    Join Date
    Dec 2013
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    Default Re: Subwoofer myth or misunderstanding?

    Quote Originally Posted by billy p View Post
    I agree folks often resort to buzz words in discreptive terms relating to subwoofers. Honestly.. I'm not immune from doing so.... on the rare occasion but I am fully aware and understand how transient response reproduction has a significant roll to play in a subs design and/or SQ.

    My old dual opposed unit sound great for movies but lacked some definition found within certain musical passages used during my demo sequences, much to my chagrin. I must preface this by adding I was also comparing it to my SB13U at the time. Easy fix really by a simple upgraded to the "SE" version drivers....instant improvement...less overhang ... better suited IMO for quickened pace or tempo changes....often required with musical pieces...I suspect and likely where transient response is often lost.

    Curious though to your final comment regarding the Caps.... I would suspect they'd be equally up to the task with music and movies going by their pedigree. Unless.. of course these were the massive units like Cap 4000 ULF or OS LFU designed specifically for HT SPL race purposes.
    Hey Billy, I didn't mean to imply that the Caps were not impressive with music. What I meant was that we didn't listen to much music on the system, so I can't really give an opinion on them for music.

  2. #12
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    Aug 2003
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    Default Re: Subwoofer myth or misunderstanding?

    Quote Originally Posted by astr0b0y View Post
    @davef How is driver transient response measured? Is it a near field measurement of SPL vs time?
    Microphone placement and SPL are irrelevant. To measure transient response (impulse response) - one must work or use testing gear designed to function in the time domain rather than frequency domain. A unique series of frequency impulses (maximum length sequence) is sent to the unit being tested. The microphone then picks up this sequence and a series of calculations is performed determining the deviations in the original sequence compared to the return sequence. Once the impulse response is calculated, nearly every other loudspeaker measurement can be determined from this data, including frequency response, by applying an FFT to the impulse response data.

    https://en.wikipedia.org/wiki/Maximum_length_sequence

    It is not something the typical hobbyist will be able to measure, which is likely why it is so rarely discussed regarding subwoofer performance. Additionally, it does take the right equipment and user knowledge to perform correctly. Besides Rythmik, I am not even sure if any of the other ID sub manufactures have access to this critical performance data, or even care about it. It is something we take very seriously (#1 priority in the design of many of our loudspeakers) and it is vital to Rythmik as well - transient accuracy is greatly enhanced by Direct Servo.
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    Good Sound To You!

    David Fabrikant
    www.ascendacoustics.com

  3. #13
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    Default Re: Subwoofer myth or misunderstanding?

    Quote Originally Posted by billy p View Post
    Different strokes for different folks I guess...purdy sure some of the folks who crave massive spl into the low teens or single digits are willing to forfeit some accuracy thou not much to reach their inevitable goals....you guys must experience first before you rule it out.... IMO.
    Not quite sure what you are referring to when you mentioned "rule it out". I have evaluated every type of subwoofer out there - from models designed to fill large theaters and concert halls - to those designed for ruler flat response and as good as possible transient accuracy. Like speakers, different subs for different purposes - no point in comparing apples to oranges.
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    Good Sound To You!

    David Fabrikant
    www.ascendacoustics.com

  4. #14
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    May 2007
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    Stouffville,Ont..
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    Default Re: Subwoofer myth or misunderstanding?

    Quote Originally Posted by davef View Post
    Not quite sure what you are referring to when you mentioned "rule it out". I have evaluated every type of subwoofer out there - from models designed to fill large theaters and concert halls - to those designed for ruler flat response and as good as possible transient accuracy. Like speakers, different subs for different purposes - no point in comparing apples to oranges.
    That remark was not directed at you or others members within this thread... if I dropped the "you" perhaps it would not sounded as a challenge...like you said it's about trade offs and I know unequivocally that all subs do not sound the same and fwiw....I use a different house curve for music vs. home theater for that reason....albeit with the same sub.
    Speakers: Towers & Horizon(w RAAL), HTM200 SE finished in espresso satin
    Sub: Funk Audio 18 in Santos

    Source: Anthem MRX 300, Oppo BDP 103D
    Apple TV, Giga 1800, & Panny 54"

  5. #15
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    Jul 2014
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    Melbourne Australia
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    Default Re: Subwoofer myth or misunderstanding?

    Thanks Dave, really well explained. The link to maximum length sequence was perfect to get me reading more on this.
    Do you design a driver with an impulse response as a target or is it a result of the rest of the design process the determines this?

  6. #16
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    Default Re: Subwoofer myth or misunderstanding?

    Quote Originally Posted by astr0b0y View Post
    Do you design a driver with an impulse response as a target or is it a result of the rest of the design process the determines this?
    There are many factors in driver design that influence its impulse response, optimize one characteristic and you end up changing other parameters. It is all a compromise.

    While I won't get into any of our design secrets, one simple aspect to improve impulse response (all other things being equal) is to decrease moving mass. However, in a woofer, decreasing moving mass also increases efficiency and decreases bass extension.

    I always try to achieve what I feel is the right balance of all driver characteristics to match the particular design. For example, in designing the final version of the Sierra-2 woofer, we sacrificed bass extension in order to go with a very low mass cone to improve impulse response to better match the near perfect impulse response of our Sierra-2 ribbon tweeter. We were lucky because we were able to go with a larger diameter cone in the same space which helped us get back some of the lost extension due to the higher efficiency of the larger cone. Many other optimizations to this woofer were implemented to improve impulse response - even in the crossover design, but I won't reveal this info.

    It is for these reasons why I spend so much time on driver design instead of simply using off-the-shelf components. I'm not saying off-the-shelf is bad (it would certainly make things easier and less costly for us) - but this is how we do things as I am obsessed with total performance, not just good performance in one or two characteristics.
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    Good Sound To You!

    David Fabrikant
    www.ascendacoustics.com

  7. #17
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    Sep 2015
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    Default Re: Subwoofer myth or misunderstanding?

    Dave, please do continue to be obsessed! We like the results

  8. #18
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    Aug 2007
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    S.E. La. - USA
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    Thumbs up Re: Subwoofer myth or misunderstanding?

    Quote Originally Posted by davef View Post
    I always try to achieve what I feel is the right balance of all driver characteristics to match the particular design...but this is how we do things as I am obsessed with total performance, not just good performance in one or two characteristics.
    I applaud your commitment, dedication and obsession with music reproduction, Dave! All AA owners greatly benefit from your passion and excellence to achieve accurate fidelity performance in a well made and beautiful product!

    Ted
    Sierra-1 NrT's, Axiom EP 500, Emotiva USP-1, Emotiva UPA-2, Phillips CD880 (dedicated 2.1 listening room)!

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