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Thread: Destructively Driving Modes

  1. #91
    Addicted to Best! RayDunzl's Avatar
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    Quote Originally Posted by dallasjustice View Post

    I'm not an IIR filter fan. There are phase shifts with IIR crossover and filters. IME, if one is careful to not ask too much from an FIR filter, it can't be beat. This is the whole point of the exercise for me. I want the best sub setup BEFORE I apply FIR impulse correction.
    Hmm... I don't have an opinion on that, but can add this from my humble place:

    AcourateDRC has the option to use (or not) IIR in addition to FIR, and splits the usage of the IIR to lower frequencies with FIR on the higher frequencies, although the IIR does gross level changes in the HF. Upper traces = FIR, lower traces, IIR.

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    I'll be back later...


    System: Equitech 1.5RQ - OpenDRC-DI w/AcourateDRC - DAC2 - Krell KCT and FPB 350mcx - MartinLogan reQuest

  2. #92
    Industry Expert [Industry Expert] Nyal Mellor's Avatar
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    Quote Originally Posted by dallasjustice View Post


    After measuring a number of sub setups with 2,3 and 4 subs in my room, the Welti 2 sub setup offers the most elegant and smoothest measurements of any other options. However, there are two ways I can improve the Welti 2 sub at midpoint, frontwall and backwall.

    1. Rear sub in reverse polarity to front sub. I measure +\- 3db from 20hz to 45hz with no DSP, 1/12 per octave smoothing. This is the "Welti optimized" setup which fazenda concluded was subjectively most preferred. The measurements in my room support that conclusion.
    2. 45hz low pass rear sub and 80hz low pass front sub. A multi-crossver sub array is needed in this setup due to the phase reversal from 2nd order length axial mode and choppy response up to 80hz with 2 subs in opposite polarity. DSP isn't needed to fight the phase shifts because the solo front sub measures very well; modex plates do their job from 45hz-80hz. The subwoofer array's level can be digitally reduced below 45hz to match solo front sub above 45hz.

    This setup is also great because only one sub (frontwall) needs to be time/phase aligned at 80hz crossover with R/L. It's also great, because a very low rear sub crossover means that the rear sub will be impossible to locate at MLP, no matter how extreme the bass levels.

    I'm not an IIR filter fan. There are phase shifts with IIR crossover and filters. IME, if one is careful to not ask too much from an FIR filter, it can't be beat. This is the whole point of the exercise for me. I want the best sub setup BEFORE I apply FIR impulse correction.

    I should have the JBL 4367s setup with the above described array using Acourate for delays, crossovers and EQ next week. I hope to post some measurements then and talk about how it all sounds.

    Michael.
    It's precisely the phase shift of IIR I was suggesting you take advantage of with the all pass filter, but nevermind.

    As to the rest of your plan, seems good. And maybe now you only need 2 subs you can use the Devialet D400!
    Acoustic Frontiers - specialists in the design and creation of listening rooms and home theaters. Experts in room design, sound isolation, acoustic treatment and AV electrical systems.

    High-end audio equipment from: ATC, Aurender, DEQX, Devialet, Exasound, JL Audio, Torus Power, Wireworld.

  3. #93
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    Michael

    Great thread. So, basically, you’ve high-passed the main speakers and then have a fleet (of two) subwoofers that are low-passed at 80Hz each with a mono-signal. And the approach has been to get as smooth as possible response in the bass via positioning on front / back walls before smoothing via Acourate. Is this correct? And, if so, then what was the process used re. filters for the subwoofers? Did you go through the full Acourate process for linearising the drivers or just use the overall room correction function for the combined main speakers + subwoofers?
    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

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