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Helium - a true micromonitor

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  • Originally posted by Dunk_c View Post
    Just did some crude tesing, thought people might find it interesting. I am no audio engineer.

    I built a set of Heliums a while ago and they sounded good to me.
    I recently bought a pair of BIC DV32 and these have less base and sound harsh and bright to me, probably because they have low output below 100hz
    Play the Heliums with the BICs and I feel that the sound is better. I can now hear more of the high frequencies and still get the bass. For my ears the Heliums are lacking some trebble.
    I have some hearing damage and cannot hear much above 8khz.

    I used an EMM-6 calibrated mic to do some crude frequency response measurements with REW (please don’t give me grief about axis scaling) the speakers were outside on a stand and the mic was about 2ft in front, pointed at the drivers.

    First thing I noticed for the Heliums, good output at low frequencies, even response across the range, but with a dip around 5khz. Did I build the crossovers correctly?

    I don’t know if the 5khz dip is contributing to my listening experience, but the BIC DV32 are flat in this region. Perhaps that is why I am more satisfied with the listening experience when I play them together.

    Any thoughts?
    If I recall, the crossover for the Heliums was pretty high; somewhere around 5k...
    That looks like a reverse null when the tweeter is wired reverse of what was spec'd. In other words, you may have the tweeter wired backwards.

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    • OK, I will check that out pronto!
      When I placed the mic directly in front of the tweeter, the dip was absent.


      • The tweeter is the typical measurement axis. The polarity is likely just fine.
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        • I forgot to say that I put the mic closer, within 6” of the tweeter, not just aligned. Scrappy testing I know!


          • If I recall correctly, I measured at 0.5 meters (or about 19 inches) at tweeter height, but with the mic pointed at the center of the baffle. Since the dip is right at the crossover point, and I haven't seen it in several measurements that I have done over the years, I would at least double-check the tweeter polarity.
            Keep an open mind, but don't let your brain fall out.

            Sehlin Sound Solutions


            • The one speaker I tested did indeed have a reverse wired tweeter, the other was OK. I might redo the sweep and repost results on weekend.


              • Tweeter polarity corrected and retested.


                • Have you noticed a difference in listening with the tweeter polarity corrected?
                  Keep an open mind, but don't let your brain fall out.

                  Sehlin Sound Solutions


                  • Scott, I honestly cannot say. I didn’t do any A/B type testing with the other channel before I rewired. I think this is the only way I could tell. I don’t believe I have much ability to hear subtle differences. I think it is something that needs practice and maybe training.