JBL N26 with N-center..My Frequency test...

Discussion in 'Archived Threads 2001-2004' started by Richard_s, Apr 9, 2002.

  1. Richard_s

    Richard_s Second Unit

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    Now that my headache is gone I can share my test. I am not an expert so remember this is from an amateur but I felt worth sharing.
    The test was run as follows:
    Tripod mounted Realistic (model 33-2050) sound level meter (note that from 20hz to 3khz the meter is flat from 3Khz to 9Khz this meter reads on average about +3db and rolls off very steep at 10Khz on up).
    Wavetech precision signal generator.
    Tested the speakers with the meter approximately 2 feet away from the face of the speaker and put the meter on centerline of the tweeter when testing both the N26 and the N-center.
    My Pioneer amplifier using the left channel. Volume set at the position on the dial where I get 80db using avia. I then adjusted the amplification of the wavetech so that the sound level meter read "0" set on 80db range at 800Hz and the "C" weighting was used.
    What I was trying to do is see how flat the response is for the N26 and the N-center. Also I was looking for peaks in the 1khz to 8Khz range which might account for ther sibilance that I have posted about but did not know if it was the speakers or the source (TV, CD, DVD).
    Results (corrected for the characteristics of the sound level meter):
    N26 well what can I say except outstanding. It was -3db at 65hz and again -3db at approx 20kHz. From 70hz to 18Khz the speaker varies no more than +/-2db. A slight peak of +3db from 7kHz to 7.5Khz . The crossover is at 3kHz and there was no noticible imperfection there or around this frequency.
    N-center well not as good this speaker is a bit "brighter" than the N26. This "brightness" is in the 4khz to 10Khz (above that I can not tell since the sound level meter rolls off too fast). Here is what I got (corrected for meter response)
    70Hz -3db
    75hz to 4.6Khz +/-2db
    4.7Khz +2db
    5.5Khz +2db
    6.0Khz +4db
    6.5Khz +8db ****
    7.0Khz +1db
    8.0Khz +4db
    9.0Khz +6db
    9.5Khz +2db
    20Khz -3db
    It seems to me that the N26 should not exhibit sibilance unless it is the source. The N-center may have peaks that can cause or accentuate the sibilance. I put on the CD that gave me sibilance. I ran it in stereo mode (N26's only)and there was sibilance but minimal. I then used a surround mode that used the center channel speaker and the sibilance was much more pronounced and anoying. So It looks like my ears agree with the results above. This also might explain why I seem to hear moderately anoying sibilance while watching TV since I use DPL most of the time and this uses the center channel predominantly (DPL set to normal).
    Conclusion (from an amateur):
    N26 has a flat response. The sibilance I hear appears to be from the source primarily.
    N-center is not equalized as well as it could be the frequencies above the crossover (3.5Khz) need to be attenuated approximately 3-4db across the full range from 4.7Khz to 18Khz
    Question:
    Is there an easy way to build a circuit that can eliminate the "brightness" of the N-center that is a constant attenuation from 4.7khz to 18 khz.
     
  2. Scott L

    Scott L Producer

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    Thanks for the info, I have the N-Center and N26s as well. I wasn't expecting them to be even mid-fi at their budget price but they do their job well. Audio sounds crisp but bright as you pointed out. I was sure the brightness was from my Kenwood receiver but I guess the N-Center should be improved upon looking at your results.
    I wish I could help you out on the circuit matter but if you say that you are an amateur then I guess I'm a beginner. [​IMG] Keep us Northridgers informed.
     
  3. Richard_s

    Richard_s Second Unit

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    Scott:
    What I have learned about equipment and testing has been mostly from this forum and the links that many have spent time posting and I spent time reading. Everyone here deserve alot of credit for the time they spend helping others.
    I am sure my test was not run in the best possible manner but I feel it is consistent with what I hear. BTW I have a stereo only Kenwood and its sounds exactly the same as my Pioneer so I doubt my results have anything to do with the receiver.
    There may be a reason why the N-center is equalized so that it is intentionally bright I just do not know why. Maybe this is better for some reason. Overall these speakers sound quite impressive and I really like them. I would just like to improve the sibilance a little and now I know what I need to do but I don't want to spend alot of money for an equalizer for the center channel.
    I tried running my system with DPL set with the center channel as phantom and the sibilance was significantly reduced just like when I run the system in the stereo only mode. This tells me that the only issue I have is with the response of the center channel as my test showed.
    Anyone know an inexpensive way I can equalize the center speaker from 4.7Khz to 18Khz as I noted above? This would be a great help.
    Thanks All..
     
  4. Phil Iturralde

    Phil Iturralde Screenwriter

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    Richard_s - your using a Pioneer DPL AV Receiver, . . . let me tell you that most, if not ALL your sibilance issues should disapear once you've upgraded to a Yamaha, Onkyo or Denon DD/DTS AV Receiver w/at least 70w x 5.
    I did not have any sibilance problems with my entire NSP1 set (including the N-Center) with my 150+ Music CD's and 250+ DVD's using my Yamaha R-V905 (authorized mailorder version of the RX-V595) 70 x 5w AV Dolby Digital (only) Receiver and Yamaha RX-V995 DD/DTS AV Receiver.
    Like I mentioned before, I've heard the sibilance problem from my OTA (over the air) TV Broadcast programs via outside antenna (no cable, etc.) at times and some mis-tracking VHS Tapes. In both cases, it was the poor source and the JBL N24's & N-Center played all my software with glorious fashion.
    Keep in mind that since the JBL's have an extrememly wide flat frequency response beyond most hearing limits (especially if you damaged your hearing or finally getting up in years), if the source (Music CD, DVD or whatever) is bright w/sibilance or dull, that's exactly how it will play back the 'source'. It's easy to tell which of your Music CD's and DVD's have exceptional recording vs. average thin sounding recordings.
    2KHz to 4KHz Speech Recognition
    When Used Too Much Produces This Effect: 3KHz listening fatigue, lisping quality, "m:, "v", "b" indistinguishable
    4KHz to 6KHz Clarity and definition of voices and instruments, makes music seem closer to listener, adding 6db at 5KHz makes entire mix seem 3db louder
    When Used Too Much Produces This Effect: sibilance on vocals
    6KHz to 16KHz Brilliance and clarity of sounds
    When Used Too Much Produces This Effect: sibilance, harshness on vocals
    Phil
     
  5. Richard_s

    Richard_s Second Unit

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    Phil:

    Thanks for the Information I hope you are right you have been so far. Given that the N-center seems worse than the N26 with respect to sibilance in my set-up and the N24's when I had them did not have any sibilance that I could hear (I did not have the n-center at the time just running the N24's in stereo) then if you don't hear any center channel sibilance that is great that means if I chose the right receiver I am all set.

    The JBL was amazingly wide and flat I was astonished how good the N26's were. The n-center I think is not as flat as I stated and could use a little attenuation in the 5khz-15Khz (I cant hear any higher anyway). But maybe the n-center is just fine and it is my amplifier.

    You recommended I try the Diana Kral "live in paris". Does this "reference" dvd exhibit sibilance or If I hear sibilance then its my system (I guess the receiver given your experience with the N-center).

    Do you feel any of the Onkyo, Dennon or Yamaha's are going to be my best bet assuming I get one with at least 70W/channel. What I want as a minimum is DD5.1/DTS (dvd'S) and DPL II (cable since they don't give me SPDIF only down converted L&R analog). Not sure what other featurs I need but I want to keep the price down.
     
  6. Phil Iturralde

    Phil Iturralde Screenwriter

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  7. John Garcia

    John Garcia Executive Producer

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    What have you done in terms of altering speaker placement? While I have a feeling it could easily be the receiver causing this, another factor could be that the placement of the speaker itself is causing some odd reflections (and as so many like to point out an MTM center design is not optimal). In the tweak area, someone mentioned something similar, and aleviated it by putting some soft foam below the tweeter, similar to what M&K does (I believe it was M&K). This removed reflection of the tweeter off of the top of the TV in this case. A farily inexpensive thing to try anyway, but you may have to experiment with it a bit.

    If your center is flush with whatever it is mounted on, then I would probably look into a different receiver. Just for kicks, try hooking the center to one of the L/R channels and see if the sound changes. Then you will have a better idea if it is the receiver or the speaker.

    There is also the possibility it could also be a bad speaker...
     
  8. Richard_s

    Richard_s Second Unit

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    John:

    Somewhere along the way I read that tweak so I set the center so that the plain the speakers are on was flush with the front of my 53hs10 TV so the grill was hanging over. I also tried the left, center and right amps on the center and all sounded identical(all are rated at 80W as well). Also the test I did was using the left amp to test the N26 and the N-center but I am sure my testing technique is not all that good. As Phil said my receiver is about 7 years old and is a DPL with some surround modes not a new receiver so that may not be helping. Possibly could be the speaker had not thought of that but at this point it would be difficult to replace the n-center so I will keep that in mind and see if when I get a new receiver things are better.

    Phil:

    Think I will buy the Diana Kral to test my system. Her music is pretty good also I heard some on my cable music stations the other day so I will add it to my modest collection. Circuit city I think has it for $14.99. I will post how the "live in Paris sounds"

    Appreciate the help. Soon I think new receiver models will be out so I will take a look at the new ones but possibly I can get a current model that is being discontinued for a better price. Hope Yamaha, onkyo or Dennon has a moderately priced DPL II model coming out.
     
  9. ReggieW

    ReggieW Screenwriter

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    Richard,

    I have the Denon 1802 (80 x 5) running with the NSP-1 package (with N-26's as the mains). You can pick-up the Denon 1602 (70 x 5) for around 275.00-300.00 online. The Denon 1802 can be had for 50.00 to 100.00 more. Both of these receivers would blend beautifully with the JBL's, and all are DD/DTS/DPL2 ready. The 1802 has pre-amp outs if you ever decide to add more power. Great build quality and great sound (but horrible remotes).

    Reg
     
  10. Richard_s

    Richard_s Second Unit

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    Reggie:

    Thanks for the recommendation. I will do some reading up on the Dennon. I guess how bad can a remote be I think I can live with that. I know this is the wrong forum for receivers so I don't want to get into to much on the reciver.

    With regard to the sibilance predominantly from the N-center do you find this is not an issue. I assume that is what you mean when you said "blend beutifully with the JBL's".

    Phil/Reggie/others

    Also since you have N24's, N26's and the N-center do you find that the N-center is "brighter" than the N24's and N26's. Just trying to see if my n-center is typical or possibly as John Garcia said maybe the N-center I have is bad. I think the n-center is just a few db brighter and the sibilance is a compination of the source and my amplifier "feedback" capability is accentuating the sibilance and the N-center is not bad ( I guess I can always buy another n-center from Best Buy and see if it is the same as mine but I hate to do that knowing I am going to return it. I will keep the Diana Kral DVD I buy so they will get some business).
     
  11. Phil Iturralde

    Phil Iturralde Screenwriter

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