Can you use a Clio system to

Discussion in 'Archived Threads 2001-2004' started by Mark_E_Smith, Jul 27, 2002.

  1. Mark_E_Smith

    Mark_E_Smith Second Unit

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    I have a Clio system that will be up and going soon. Can you use it to balance or adjust a HT system? I was thinking about putting it in all channel mode and shutting down the rear surrounds and doing a measurement that would include the room response. Then adjust the sub and its x-over. I do also havew a RS spl meter. Any sugestions? Also any tips on using the Clio to analyse speakers. ie damping the bass refections so I can measure below 200 Hz
     
  2. Dan Wesnor

    Dan Wesnor Second Unit

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    Suggest you find and read a copy of "Testing Loudspeakers" by Joe D'Appolito.
     
  3. Dennis XYZ

    Dennis XYZ Stunt Coordinator

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    Clio's SPL meter is much more accurate than the RS so it will work fine. Set it to C weighting and slow averaging so the readings will be what your pre/pro is expecting.

    I don't think you want to "damp the bass reflections" when you measure the frequency response. Rather, you want to measure them as they are included in the in-room response. If you do want to simulate an anechoic response, just stick the mic up close to the speaker.

    There are some gotchas using the MLS and FFT functions to measure bass response. It's best to confirm any readings you get by running a simple tone sweep and comparing the unweighted SPL reading to make sure you aren't screwing up the MLS and FFT. Carefully read the part in the manual about measuring frequency response with MLS.

    Short version, with Clio Lite, you can't get good HF and LF measurements with the same settings. There are two important settings, the sampling frequency and the sample size. Lite is limited to a 16K max sample size so just leave it there. Sampling frequency need to be at least twice the frequency you want to measure. I think the default is 51kHz so that's plenty to measure a 20kHz tone. But the problem with the defaults is at the low end. 51kHz/16K = approx 3 Hz. You will have a sample on the graph about every 3 Hz. That's plenty of resolution up high but that's 1/3 octave if you're measuring down around 10Hz - not fine enough. So, if you don't care about the HF measurement, reduce the sampling frequency to 8kHz. Now you will have a point every .5Hz and your bass measurements will be more accurate.

    The next gotcha is selecting your window size. Clio puts out a pulse and measures the return. It plots a graph with time on the X axis and you can pick which part of the return you want to look at. If you want to simulate the anechoic HF response, you want a pretty small window so it ignores all the wall reflections - just a few msec. But the catch for LF is you need to give it big enough a window for a whole cycle of the wave. For a 10Hz wave you need at least 100msec in addition to the time it took for the signal to travel through your pre/pro (with its delays) and travel through the air to hit the mic. If you want to measure the room modes too (you should) you need to give it time to bounce off all the walls and build up so that's maybe another 100 msec. If your window is too small, it will still plot the bass but it will look too "smooth" and won't be at all accurate.

    Hope that helps. It's a great tool once you figure it out.

    (edited: typing too fast)
     
  4. Mark_E_Smith

    Mark_E_Smith Second Unit

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    Thanks for your insite, I thought this instrument would be easer to use, maybe it is, just the manual isnt clear.(and I am waiting for some computer paarts to have its own dedecated PC so I havent completely fired it up yet) I was refering to damping the reflections to test a speaker not the system. I am trying to understand baffle step so I am trying to eliminate refections when I test the speaker. Short of build a chamber I was thinking about building some traps to suround the speaker. I have access to a large building with a 16 ft ceiling that I could use but it is concret and has really bad acoustics. Is the floor wave or standing wave of the room more important to damp? Or do I really need to worry about this as any room I put them in will have these relections? Also does the Clio lite ( the version I have) output directly to an amp or does it need a preamp also?
     
  5. Dennis XYZ

    Dennis XYZ Stunt Coordinator

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    You can always move outdoors to get rid of wall reflections. Put the mic on the ground to eliminate floor bounce. Clio can plug right into your power amp. Make sure the output level is down when you turn it on. [​IMG]
     
  6. Chris Carswell

    Chris Carswell Supporting Actor

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    Hey Mark,
    Did you get the computer fixed? How is the center comming?
     
  7. Mark_E_Smith

    Mark_E_Smith Second Unit

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    The new parts will be in tomorrow, I did hook it up to another computer I have and it works, The serial port controller was bad on the old PC MB, drove me crazy as the Clio has to have a working serial port attached to the A/D D/A converter box or it will not recognise the Clio system. All will be well soon. AMD 950 duron on a shuttle board 256Mb ram and a cd burner. I also repaired the leaking caps in an old NAD 3020 preamp/amp so its good for the amp to drive the speakers for testing. Now to build a few cables and try to understand the manual[​IMG] , I did order the speaker testing book by Joe D'Appolito hope it explains things a little better.
     
  8. Mark_E_Smith

    Mark_E_Smith Second Unit

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    Got it going and had some time this weekend and played around with it. I was pleased with the measurements on the center channel speaker. All that I need to do now is make a notch filter for the +4dB peak at 9300 Hz. No baffle step is evident. The box is sealed nicely but the tuning is lower that I targeted by 8Hz, but pro-logic and THX roll off the center below 100 Hz anyway. I am sure the signal has some reflections as it was taken in the room with furniture. Any way very interesting and not as hard to use as I thought. I do need to invest in some more playing around with damping and a semi anechoic room for testing.
     

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