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  • gregrueff
    replied
    The DA215-8 really stressed my test baffle and there was definitely a panel resonance that shows up in the bass HD sweeps. You could hear it at the beginning of the sweep. The power and cone area of the DA215-8 really exposed this.

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    The test baffle was never intended to be perfectly rigid; only provide a semi-useful FR curve.
    You can see in this underside shot how I built the frame using 2x4s and laid the foam board on top of it.

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    Consequently, I wouldn't put too much stock into the bass HD sweeps and it also helps explain why that area looked high in the other driver's HD tests.
    The real test will be once the drivers are loaded into a real enclosure.

    Leave a comment:


  • gregrueff
    replied
    DA215-8 Results:

    Frequency Response
    Click image for larger version

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    Harmonic Distortion

    4" @ 2.83 Vrms
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    Harmonic Distortion
    4" @ 96 dB fundamental
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    Harmonic Distortion
    12" @ 96 dB fundamental
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    Harmonic Distortion
    24" @ 96 dB fundamental
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    Leave a comment:


  • johnnyrichards
    replied
    No, there is no safe assumption as such. If you assume the baffle is zero, than each different point source will exhibit an offset. What you are looking for is offset between two or more point sources. Estimating this distance is fuzzy math at best. If you are running a single point source, than there is no offset. Think of it in terms of a triangle - woofer, tweeter, listening position. So even changing listening position will impact the relationship - which is easily seen in modeling software.

    You need a microphone and a rigorous test methodology if you want to determine offsets.

    Leave a comment:


  • LOUT
    replied
    Originally posted by johnnyrichards View Post
    It is a relative measurement, as in "offset from what other driver?"
    I'm guessing that means it can't magically be measured as a woofer's "offset" from the baffle, assuming the baffle as zero? That kind of makes sense I suppose because the measurement must need a second sound source to act as the assumed "zero" or offset point.
    Do tweeters commonly have their own offset to worry about or is it usually safe to assume a tweeter as zero even if you're changing to a different tweeter while keeping the same woofer and baffle somehow?

    Leave a comment:


  • johnnyrichards
    replied
    Originally posted by LOUT View Post
    Do either of you happen to have an accoustic offset measurement for the PC105?
    It is a relative measurement, as in "offset from what other driver?"

    Leave a comment:


  • LOUT
    replied
    Do either of you happen to have an accoustic offset measurement for the PC105?

    Leave a comment:


  • Wolf
    replied
    I ran the 105-4 in a dual-chamber aperiodic sealed alignment, and they really sounded good like that. About a liter a piece with pegboard sandwiching 1" foam across the center. Later, Wolf

    Leave a comment:


  • gregrueff
    replied
    This is a little easier to read since it is clearly a two driver race between the LY302F and the PC105-8.
    Above about 1 kHz, the LY302F looks better in both HD3 & HD5.
    Given that I've been focused on how low I could cross either, I'm leaning towards the PC105-8 which suggests 250 Hz isn't too low.

    Click image for larger version

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    Click image for larger version

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    Leave a comment:


  • gregrueff
    replied
    It's a little tough to read, but on HD3 the PC105-8 really seems to win out.
    The LY302F is close if it weren't for the peak at 650 Hz that my measurements bear out, except for the low end where the increased cone area of the PC105-8 takes the cake.

    Click image for larger version

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    Attached Files

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  • gregrueff
    replied
    Originally posted by Wolf View Post
    I'm using mine in the OSFA BT-box in a 1/2" ply baffle with no relief, save for the required inset for the frame-lip. It seems like it doesn't have any issues.
    Later,
    Wolf
    Yeah, I think I was just hoping for better.
    I may still revisit this.

    On the other side of things, I'm pleasantly surprised that the PC105-8 appears to be beating out the LY401F in HD. It can't match the LY401F's sensitivity or thermal management, but looks really good nonetheless.

    Leave a comment:


  • gregrueff
    replied
    LY401F Results:

    Frequency Response
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    Harmonic Distortion
    12" @ 96 dB fundamental
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    Harmonic Distortion
    24" @ 96 dB fundamental
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    Leave a comment:


  • gregrueff
    replied
    PC105-8 Results:

    Frequency Response
    Click image for larger version

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    Harmonic Distortion

    12" @ 96 dB fundamental
    Click image for larger version

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    Harmonic Distortion
    24" @ 96 dB fundamental
    Click image for larger version

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    Leave a comment:


  • Wolf
    replied
    I'm using mine in the OSFA BT-box in a 1/2" ply baffle with no relief, save for the required inset for the frame-lip. It seems like it doesn't have any issues.
    Later,
    Wolf

    Leave a comment:


  • gregrueff
    replied
    I feel that the PC83-8 requires further investigation.
    I'm wondering if the backside of the test baffle is too restrictive, even with the chamfer.
    I may have to create a new insert out of 0.25" just to test if free-er flow reduces any of the HD seen here.

    Leave a comment:


  • gregrueff
    replied
    PC83-8 Results:

    Frequency Response
    Click image for larger version

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    Harmonic Distortion

    12" @ 96 dB fundamental
    Click image for larger version

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    24" @ 96 dB fundamental
    Click image for larger version

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ID:	1442110

    Leave a comment:

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