Qb vs. NLA

Discussion in 'Infinity Loudspeakers' started by Rdenney, Mar 13, 2019.

  1. Rdenney

    Rdenney Active Member

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    I’m currently running stacked Advents, and they sound fine. The stacking brought me the dynamics I seemed to be missing from a single pair.

    But, notwithstanding my aging ears, I am not unaffected by all the praise for the EMIT tweeter, and the benefits of adding a mid.

    Has anyone directly compared Infinity Qb’s with Advent NLA’s? They are just about the same size, but with the pre-Watkins “Q-woofer”, also acoustic suspension damped.

    What is the maximum output of the Qb? I am able to achieve what I call reference loudness with the four Advents—105-110 dB SPL without clipping the amp (a B&K Reference 125.2, 180 wpc into 4 ohms and a high-current design). Can a single pair of Qb’s keep up with that? They would only need to be 3 dB louder than Advents to do so, in theory. I mistrust efficiency measurements—I’m interested in maximum output, not output at 1 watt. The Qb’s are rated for higher power than Advents (also not a trustworthy specification), but stacked Advents will handle twice the power of a single pair.

    3. How critical is the tweeter position vertically? I know the dispersion is wide horizontally. I may need to position them on a high shelf (I know they prefer to be out from the wall, but so do Advents). (If I position them horizontally, I would turn the tweeters 90 degrees. I could then tilt the speakers down to point down to ear level.)

    Again, I’m just exploring possibilities.

    Rick “in learning mode” Denney
     

     

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  2. Pio1980

    Pio1980 AK Member Subscriber

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    I'll throw an Econowaveguide mod'ed Advent pair into the this mix as an acceptable alternative that might meet your requirements.
     
  3. Rdenney

    Rdenney Active Member

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    I have explored that already, and it is an interesting concept. I worry anoutduspersion, however. My experience woth gowns is that shape is everything, and some shapes disperse well while others are designed for throw.

    I’m just curious whether anyone has measured SPL from the Qb’s at their maximum capabilities, and what amp power was required to achieve it. And whether the speakers still sounded good and operated durably at that listening level.

    Rick “who doesn’t play really loud very often, but who wants the capability” Denney
     
  4. Ohighway

    Ohighway Wannabe Minimalist Subscriber

    Wonder what stacked Qb speakers would sound like !!?
     
  5. Pio1980

    Pio1980 AK Member Subscriber

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    Afaik, even dispersion ("constant directivity") is one of the virtues of the waveguide horns.
     
  6. TomBig58

    TomBig58 AK Subscriber Subscriber

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    I followed your other post and I can't speak to the "throw" of the Qb's in the elevated position you have the Advents but in a side by side the Qb's outperform a single pair of Advents handily through the mid-ranges. Low end is very similar. Surprisingly the Advent paper cone tweeters keep up with the emits admirably. Powerwise you should have no problem but the Qb's are 4 ohm rated. Note the off center location of the emits on the Qb's as well as the RSb's makes it a little weird for horizontal setups as they aren't L-R symmetrical.
     

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  7. swechsler

    swechsler Frog Whisperer

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    Wonder if anyone's ever stacked Qas or Qbs?
     
  8. TomBig58

    TomBig58 AK Subscriber Subscriber

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    I'm working on Qb-RSb compare but something is going on with the RSb's besides cleaning the pots. Just ordered crossover parts so more to come. I really think vertical stacked Qb's would be something special.
     
  9. Rdenney

    Rdenney Active Member

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    Yeah, it’s the same with the Advents, though the NLA’s aren’t quite as offset as the OLA’s wer, or as the Qb’s.

    My amp is rated at 185 wpc into 4 ohms, and can supposedly play a square wave at rated power and rated THD (<.09%) for 8 hours. 1.2 dB dynamic headroom. It has no trouble attaining 105-110 dB peaks with stacked Advents, which at best aspire to 4 ohms wired in parallel.

    All this is just thought experiments—my way of learning new stuff. Never can tell when something compelling might turn up.

    Rick “trying out ideas” Denney
     
  10. chef free

    chef free AK Subscriber Subscriber

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    Infinity Qb are rated as 89dB @ 1w/1m and can handle 150 watts. That's a bit over 110dB minus 3dB for each additional meter away from the speakers.

    I ran stacked Qb with a 75/100 watt MAC 4100 receiver with good results. It was kind of a "poor-man's line source". They were on one foot high stands, as recommended by Infinity, and wired in parallel for two ohms. The EMITs are a little "phasey" and sound best with zero toe-in but the four inch Philips midrange sound better toed-in to point right at you, so there is some compromise there.
     
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  11. Rdenney

    Rdenney Active Member

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    Or 6dB for each doubling of distance, assuming non-directional radiation. I’m looking at 10-15 dB if distance loss, less whatever the room reflects. I don’t think a pair will be enough louder than a single pair of Advents to do what I’m hoping, and stacking two pair would require series wiring with my amp.

    Rick “thanks all” Denney
     

     

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