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Testing woofers question

isaeagle4031isaeagle4031
in Announcements
I haven't bothered with testing drivers without an enclosure. I am curious as to what method you guys use for taking FR without a baffle. Specifically I am testing the 55-3669 and what to make sure I have at least a decently accurate plan.

So far I have simply put the driver onto a bed of convulted foam with pieces around it and taken sweeps about 1/4" and about 6" from the cone. The FR and distortion profiles LOOK good, but I want to insure accuracy without needing to use a huge baffle if I can.

Comments

  • MzissersonMzisserson
    isaeagle4031 said:
    I haven't bothered with testing drivers without an enclosure. I am curious as to what method you guys use for taking FR without a baffle. Specifically I am testing the 55-3669 and what to make sure I have at least a decently accurate plan.

    So far I have simply put the driver onto a bed of convulted foam with pieces around it and taken sweeps about 1/4" and about 6" from the cone. The FR and distortion profiles LOOK good, but I want to insure accuracy without needing to use a huge baffle if I can.
    What really matters is FR from about 2 octaves above the knee (so for an50Hz Fs, 150 and up) since the box no longer effects the response at those Fqs. 

    Really, from room transition up is the most important for to get a good idea of the drivers reaponce. That is typically in the 250-350 range. 
  • isaeagle4031isaeagle4031
    edited April 2017

    kennyk
  • isaeagle4031isaeagle4031
    So there are a couple of quick measurements. These were taken with the driver sitting on a bed of convulted foam with additional pieces placed around it and about 4-6" away. The mic was placed directly above and about a 1/4-3/8" from the dustcap. 
  • PWRRYDPWRRYD
    Measuring that close (near field) will only result in accurate data to about 900-1000 Hz.
  • PWRRYDPWRRYD
    To get full range data you need to be at least 3x the cone diameter away.  Without a significant baffle you will see the first dipole peak and null right in the intended pass band.  It's ok to measure a tweeter (non open backed) like you did, but not an open backed woofer or mid.  You need a box or an infinite baffle.
  • isaeagle4031isaeagle4031
    I figured that craig. This was just a quick test mainly looking at the area where this driver would cross and the distortion in that area. 
  • jr@macjr@mac
    I should have a shootout between 2669, 3669, and Eclipse 5-1/4" next week. If I had one of those AC woofers used in that one design, I would add it into the mix. The measurements will be taken in-box, though. 
    I have a signature.
  • isaeagle4031isaeagle4031
    Maybe over the next couple of weeks, i will have time to build a couple of boxes for these. This first pair will probably be going to my niece.
  • PWRRYDPWRRYD
    If Geoff would like to send me a pair of 55-3669's I'd be happy to do independant FR and distortion measurements on my 4' x 4' infinite baffle and post them here and on PETT  ;)

    I think these drivers could make a killa economic bookshelf paired with the ND25FW.
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