Massive Dip at 110-95 Hz....!

Discussion in 'Speakers & Subwoofers' started by Ray_C, Jan 18, 2004.

  1. Ray_C

    Ray_C Stunt Coordinator

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    Hello All,

    When setting my Klipsch RB-25's to large/full range (sub off) on my Denon 2803, and running both a 20kHz-20Hz sweep and individual test tones thereof, I'm getting a massive dip in level (a;most gone!) between 110 and 95 Hz.* I'm aware that room acoustics have a lot to do with it, but it's also very evident when listening up close to the speaker, or putting a SPL meter very close.* It seems to pick up again once it gets down to 85 Hz, then slowly fades off as it gets down to the spec'd freq. floor of 50 Hz.* I noticed this same thing when I was using a Denon 1802.* Is this really mostly the room, the receiver/amp, or am I expecting too much from the 6.25" woofer-ed RB-25's, even though they are spec'd to go down to around 50 Hz.* If I were to try and eq this, I'd be boosting things something like 6-7dB in the aforementioned dips.* Shouldn't things, ideally speaking, be more flat?* I'd like to leave my crossover setting at 80 Hz, rather than bringing it up to 100 or 120, when listening to both music and HT/movies.
     
  2. Edward J M

    Edward J M Cinematographer

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    Sounds like room acoustics. Klipsch I'm sure has access to anechoic chambers and would (should) not have allowed such an obvious dip to make final production.

    The only way to tell for sure is to place the speaker outside with the mic at 1 meter and try it again.

    Also be sure the source of your sweeps/tones has not been compromised; sometimes they are off spec too.
     
  3. John Garcia

    John Garcia Executive Producer

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    Sounds like room modes to me as well, and adjusting your x-over point will not fix this. How do you have the sub's x-over set? If it is not set to max, you may be cascading the x-over and causing the gap as well. Do you have the same problem if you run the mains full range with no sub? If so, it is a speaker placement and/or phase issue, not the speakers.
     
  4. Ray_C

    Ray_C Stunt Coordinator

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    Thanks for the replies. I do this test with my sub off, because I feel like I'm missing some punch when listening to music in stereo. I have a test CD that has test tones each at -12dB at increments of 5 Hz from 15 to 20k. I've tested the speakers on the floor, on the stands and on a table and get the same thing. I run these same tones/tests on my powered mixing monitors that I use for video/audio editing, and I don't get such a big dip. Also, my center channel speaker (an RC-25) doesn't have as much of a dip, either. When I listen to 2-channel music with the xo at 80Hz, some tyhings sound good, others still have a bit of a hole. I'm looking to get a separate 5-channel amp anyway, but I'm a bit confused. I like the idea of thrying the speaker outside, but it's too darn cold right now.
     
  5. Justin_D

    Justin_D Stunt Coordinator

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    Forgive me, but I'm still learning:

    Coudln't you just use an equalizer and "turn up" those frequencies?
     
  6. Ray_C

    Ray_C Stunt Coordinator

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    In theory, yes, but we'd be talking something like 7-12 dB of boost, which is pretty severe, and if I was just using the receiver, I'd have to find a way of inserting the eq between the pre- and power amp internally. If it's the speakers that just aren't producing this range, then boosting the frequencies might damage them.
     
  7. John Garcia

    John Garcia Executive Producer

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    That's different then. If your studio monitors don't have the same problem, then it sounds like the speakers are the culprit, especially if placement doesn't at least make a noticable difference and you don't have the sub on.


    It probably won't damage them, but it also won't necessarily sound better.
     

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