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Thread: Driver size has impact on center image size?

  1. #1
    Indecisive Tuner BowDown's Avatar
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    Driver size has impact on center image size?

    Just a theory.. but I'm curious if someone has come across the same observation.. or not. I know I posted this over on DIYMA, but there are a bunch of knowledgeable people here that may have more insight.

    I'm down to a 2-way front stage in an effort to clean things up, and so far so good.

    Anyway.. I have been playing with TA and a bit of EQ in an effort to get the softball sized center image I have heard in other vehicles. My pillars are running neo8's from 700hz+, and the stock door locations are running 45hz to 700hz.

    When I isolate the pillars I can get the image to about that softball size I'm looking for... but when I isolate the door speakers my image doesn't seem to get smaller than a soccerball. This is with our without the lowpass crossover point bypassed.

    Is this a limitation of the stock speaker location.. or a limitation of the 7" driver size?

    It seems most of the systems with tight center image are running a wideband 3 or 4" driver above the dash line and are crossed over lower than my 700hz point.
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    Controller AL9000's Avatar
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    Interesting topic...I'm curious myself. I wonder if difference in reflections that the pillars and door speakers see are what's causing it? Have you tried putting a towel in the driver and passenger windows as an experiment to eliminate that reflective surface?


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    Founding Member earthtodan's Avatar
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    I'm pretty sure that phase & time alignment are more important than level matching at any given band in the frequencies you're using in the doors, due to ITD vs IID and the precedence effect. What it boils down to for me is, you can EQ driver levels independently to bring each IID frequency to the center, but you can't do the same with phase for ITD frequencies because DSPs do not have phase adjustments every 1/3 octave.

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    Indecisive Tuner BowDown's Avatar
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    Quote Originally Posted by earthtodan View Post
    I'm pretty sure that phase & time alignment are more important than level matching at any given band in the frequencies you're using in the doors, due to ITD vs IID and the precedence effect. What it boils down to for me is, you can EQ driver levels independently to bring each IID frequency to the center, but you can't do the same with phase for ITD frequencies because DSPs do not have phase adjustments every 1/3 octave.
    Wouldn't that be the nuts. Especially after studying my driver's phase plots. Lol.



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  5. #5
    Founding Member earthtodan's Avatar
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    I've done slow test tone sweeps with individual drivers in the doors, and sometimes frequencies in the bands you're using sound like they're coming from the opposite side of the car. As in, I could swear that 250 hz (for example) is coming from the left side when only the right speaker is playing. Try centering that.

  6. #6
    Indecisive Tuner BowDown's Avatar
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    I know exactly what you mean there. My 80hz does that something awful. Also I have a wicked dip from 250-500 in the doors. I would imagine it's from cancellation as the wave length is about the distance from the cone to the center dash piece.
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  7. #7
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    It has nothing to do with driver size. it has everything to do with the wavelength though. Sometimes I think people believe the switch between ITD and ILD is on/off. It is gradual.

    Also, there is a big misunderstanding with ITD and understanding where it comes from. A single speaker creates it's own ITD based on azimuth+elevation angle (2 path lengths-one to each ear). Two speakers playing the same range each create their own ITD based on azimuth+elevation angle (total of 4 paths-one to each ear).

    Q: How do you correct all 4 PLD's with 2 time alignment adjustments?
    A: Short answer, you can't.

    Second
    Most of the midbass (~80-250Hz) is swamped by the room modes due to the dimensions of the walls, floor and ceiling of the vehicle because the wavelengths are > room dimensions, so all you can do is try to even out the room modes by smart speaker placement. This will reduce weird phasiness problems, just don't screw up sub to midbass integration.
    Last edited by durwood; 05-01-2013 at 01:10 PM.

  8. #8
    Founding Member earthtodan's Avatar
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    It is gradual, but the transition point is generally approximated as 1500 hz, so I'm assuming we can talk about 700 hz and below as ITD.

  9. #9
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    I'm with Darin. Nothing to do with size, everything to do with install and tuning.

    I'll bet smaller drivers TEND to get installed in places that allow for EASY tuning to get a super tight center image and a stage the size of a postage stamp (ie pillar mounting). Whereas large drivers tend to be installed in locations much more challenging to get right but yield a larger stage, or enabling more of those image smearing reflections to get in the way, turning a golfball sized voice into a soft ball. Either way would make your center "fatter".

    Therefore IMO at best it is a second order relationship.

    lower case i and m and capitol O.

  10. #10
    Senior Member cvjoint's Avatar
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    Two things going on here. Neo 8s and a 7" cone have similar surface areas, so it's not a small speaker big speaker comparison. Second, you are running different bandwidths. Third, they are different locations.

    experiment 1: equalize bandwidth, but keep it so that both speakers can handle it without differences in dispersion or non-linear distortion. Say 700hz-1400hz. Flip between the two and this will tell you what difference the locations have over this bandwidth on center/focus.

    experiment 2: this is not a great one because your drivers arent that different in size. But run both sets in pillars 2000hz up to one octave under cone resonance. This will test differences in dispersion, and therefore driver size on center/focus.


    But if you really want to get scientific on this one, use one small fullrange driver and one large fullrange driver. that way you bandwidths are wider you get a better idea in the same locations what difference the size of the driver makes. All you have to do is keep the SPL low so the small driver doesn't crap out.


    My guess is that since small speakers and big speakers have different dispersion patterns, differences in sound stage will occur based on driver size.
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