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NHT Evolution U2 Subwoofer Measurements!!!

Discussion in 'Speakers' started by terence, Jan 8, 2004.

  1. terence

    terence Well-Known Member

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    Check it out from Robb Reports Home Entertaiment & Design. Man talk about FLAT!
    http://www.hedmag.com
    The chart shows the frequency response of the NHT Evolution U2 subwoofer, measured with a calibrated microphone positioned about 1/4-inch from the speaker cone. The subwoofer was driven with the supplied X1 crossover and A1 amplifier. The purple trace shows the response with the X1’s low-pass filter deactivated, the green trace shows the response with the filter engaged and set to 80 Hz. (The low-pass filter blocks midrange and treble signals from reaching the subwoofer.)
    A frequency response measurement shows how consistently a subwoofer responds to different frequencies of sound. The flatter the curve looks, the better and more even a subwoofer will sound.
    Normally, when I measure a subwoofer, I take the peak level at the top point of a curve, find the frequency points in the upper and lower ranges that are 6 decibels lower than the peak, and specify the frequency response as the range between those two points. However, such a specification does not do justice to U2.
    Almost all subwoofers produce a curve that resembles a haystack—a gently rounded hump, with strong response in a fairly narrow frequency range, and declining response above and below that range. However, U2’s response looks more like that of a well-designed full-range speaker. It is flat over an extended range—well up into the midrange, in fact, if the X1 crossover’s low-pass filter is deactivated.
    Normally, I would specify U2’s frequency response as ±3 dB from 21 to 250 Hz, which is an outstanding measurement. But it is more illustrative to state U2’s frequency response as ±0.2 dB from 26 to 180 Hz. This is, in essence, perfect subwoofer performance—useful response down to 20 Hz, and dead flat response far past the point where the U2 will be crossed over to the main speakers. I have measured more than 100 subwoofers, and this is easily the best frequency response I have ever measured from any subwoofer, at any price. NHT’s engineers must have done considerable equalization inside the X1 to get the response this flat.
    NHT also probably included a limiter to prevent the distortion that can often result when a small subwoofer cabinet like this is force to play so deep. Clearly, they took some steps to prevent distortion, as these measurements(and my listening impressions) indicate. You may notice that the subwoofer’s response seems to fall off a cliff below 25 Hz. This is obviously the result of steep infrasonic filtering inside the X1, which is a very good idea—trying to reproduce frequencies below 20 Hz with this subwoofer would not result in an audible improvement, and would surely lead to distortion and a shorter product life.
    The X1’s controls , at least on the review sample, have some problems. According to my measurements, the boundary compensation barely works at all—setting it for +6 dB produced no effect, while setting it for –6 dB resulted in only a 1 dB response dip centered at 40 Hz. Also, the low-pass filter adjustment is not accurately calibrated: My measurements show that the –3 dB point with the 80 Hz setting is actually at about 100 Hz. The filter, by the way, has a 24 dB/octave (fourth-order) response, which in my opinion is the best all-around choice for a subwoofer low-pass slope.
    I’m going on far too long for an article that’s simply supposed to present a subwoofer measurement, but I have a hard time shutting up when I am so impressed. When I looked over the printed version of the U2 review in Home Entertainment & Design, I briefly regretted the statement that U2“delivers sound that compares favorably with that of any subwoofer I have heard.” Surely, a $1,400 subwoofer could not be so good. But the measurements bear out my listening impressions. This is a very impressive piece of engineering.
    [​IMG]
    Specifications:
    Description Dual W-1 enclosure subwoofer with A1 Amplifier and X1 Active Crossover included.
    Drivers Two 12" aluminum cone (1 per enclosure), high excursion.
    System Power 250W RMS.
    Peak Acoustic Output @1M 112dB SPL
    Frequency Response 26Hz-140Hz. +/- 3dB
    Input Connectors 5-way binding posts.
    Dimensions 14”H x 14"W x 14"D
    Weight (subwoofer enclosure) 38lbs each
    Finish Anthracite matte lacquer
     
  2. Jon_Welker

    Jon_Welker Well-Known Member

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    Yeah, gotta love thos NHT subs! I have the same action but in different packaging with 2 NHT T5's. Each pedastel has a 12" sub in it with the same hardware driving them. Talk about flexibility without sacrificing sound.
     
  3. jacbec

    jacbec New Member

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    Don't know if you are still around, but I am having problems with my NHT U2 System (A1, X1, 2 W2 Subwoofers, 3 M6 (front left, center, right) & 4 iC4 Surround speakers. The subs stopped working about 4 months ago (Yamaha V2600 receiver, connected to LFE). Now have a Marantz SR7007 connected to SW1 in PRE OUT. I have checked the A1 & Subs with my iPhone and get sound OK. X1 had continuous amber light so sent back to NHT for service. They couldn't find anything wrong with the X1. Now have it all reconnected and still no sound from Subs. X1 amber light stays on as before.
     
  4. Tom Vodhanel

    Tom Vodhanel Well-Known Member

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    In the owner's manual what does the "continuous amber light" indicate? Tom V.
     
  5. jacbec

    jacbec New Member

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    The Manual Trouble Shooting section says: If only the 'S' (Amber) LED is illuminated verify that he trigger mode switch is in the 'Audio' position. Mine is. I think my problem is a bad cable from the receiver to the X1. I ordered a new cable and it should get here in a couple of days,
     
  6. Tom Vodhanel

    Tom Vodhanel Well-Known Member

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    You can use any spare cable to test this....old composite video cables work fine for subs for example. Also, does the XI have an "always on" mode? If so, try that. It sounds like the amber lite only illuminates when the unit is having troubling detecting a signal to "auto on"? Tom V.
     

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