Post by speakertom on Feb 10, 2024 11:13:03 GMT -5
Yesterday I heard the Philadelphia Orchestra conducted by Tugan Sohkiev present a program including Gabrieli, Britten, and Shostakovich’s Symphony No. 4. In addition to the music, I wanted to measure SPLs during the performance. To do that, I purchased an small measurement mic from Parts Express that would link to my iphone. Here is a link: www.parts-express.com/Dayton-Au ... quantity=1 The cost was a whopping $20. These mics have individual calibration date available by serial number for download from their site. This will not replace my ACO mic for serious in house work but it didn’t cost $2K either. I decided to use it with the app Audiotools. apps.apple.com/us/app/audiotool ... d325307477 I also had to get an adapter to go from the old TRRS connector to Thunderbolt.
When it arrived, I downloaded the correction file into the app and compared it to the Tenma 72-860 sound level meter I also have. It was immediately apparent that although the correction file adjusts the frequency response of the new mic, it has no effect on the sensitivity. I have a class 2 microphone calibrator that has output levels at 94 and 114 dB. Using that, I found that the new mic was low at both levels by 5.7 dB. I made that correction in the app. Just for grins, I compared it to the ACO at several different frequencies and found to my surprise that with the calibration file installed in the app it was within a few tenths of a dB at those frequencies. So I decided that with the correction file and adjustments to the sensitivity, it was more than adequate for casual in the field measurements.
I went to the concert with three other audio friends, one of whom for 40 years used to play bassoon for the orchestra. For reference, the seats were in the center of the first tier about 6 rows from the rear wall and under the overhang from the second tier. Usually I sit center in the orchestra anywhere from the 6th to 20th row. The sound in the upper tier was very different being much more diffuse with a softening of the transients and less detail but a very pleasing “homogenized” sound. My guess is that compared to the sound in the orchestra, most of what I was hearing was a much higher percentage of reflected than direct sound. It was more laid back than the stimulating sound I get from the orchestra seating but to my taste not what I am looking for when I go to a live performance. To each his own.
On to the SPLs that I measured. First, being as far back as I was, I expected the SPLs to be significantly lower than the orchestra positions. Here is a recap. During the breaks in the performances if no one was coughing or shuffling around, the background level was as low as 42 to 43 dB. That is still quite a bit higher than my listening room that can get below 30 dB if the AC is not running. I am limited by the low level sensitivity of my ACO mic to get an accurate reading but I believe is as somewhere around 26 – 28 dB. During the quietest musical passages, the level was in the range of 45 – 55 dB. That was not often but did occur. A large part of the performances were in the 75 – 85 dB range. During several parts of the 4th where the orchestra was really cranking, the levels stayed in the 95 dB range for a reasonable time which surprised me being that far back in the hall. The peak level I recorded was 100.7 dB. My estimate is that it would be at least 10 dB higher in one of my favorite orchestra locations.
This just reinforced my feeling that if you have a moderately sensitive speaker system you need lots of power if you are going to get the emotional impact of a live orchestral performance from the likes of Mahler, Shostakovich, or Prokofiev. If you are a chamber music or folk fan you can probably get by with less. In my case, I decided that rather than worry about how an amplifier performs when clipping occurs, I would just have sufficient power that the amps never clip. Problem solved.
Just wanted to fill you in on the results I got. I hope to repeat it in the near future at one of my closer orchestra locations and will sent the results.
Tom
When it arrived, I downloaded the correction file into the app and compared it to the Tenma 72-860 sound level meter I also have. It was immediately apparent that although the correction file adjusts the frequency response of the new mic, it has no effect on the sensitivity. I have a class 2 microphone calibrator that has output levels at 94 and 114 dB. Using that, I found that the new mic was low at both levels by 5.7 dB. I made that correction in the app. Just for grins, I compared it to the ACO at several different frequencies and found to my surprise that with the calibration file installed in the app it was within a few tenths of a dB at those frequencies. So I decided that with the correction file and adjustments to the sensitivity, it was more than adequate for casual in the field measurements.
I went to the concert with three other audio friends, one of whom for 40 years used to play bassoon for the orchestra. For reference, the seats were in the center of the first tier about 6 rows from the rear wall and under the overhang from the second tier. Usually I sit center in the orchestra anywhere from the 6th to 20th row. The sound in the upper tier was very different being much more diffuse with a softening of the transients and less detail but a very pleasing “homogenized” sound. My guess is that compared to the sound in the orchestra, most of what I was hearing was a much higher percentage of reflected than direct sound. It was more laid back than the stimulating sound I get from the orchestra seating but to my taste not what I am looking for when I go to a live performance. To each his own.
On to the SPLs that I measured. First, being as far back as I was, I expected the SPLs to be significantly lower than the orchestra positions. Here is a recap. During the breaks in the performances if no one was coughing or shuffling around, the background level was as low as 42 to 43 dB. That is still quite a bit higher than my listening room that can get below 30 dB if the AC is not running. I am limited by the low level sensitivity of my ACO mic to get an accurate reading but I believe is as somewhere around 26 – 28 dB. During the quietest musical passages, the level was in the range of 45 – 55 dB. That was not often but did occur. A large part of the performances were in the 75 – 85 dB range. During several parts of the 4th where the orchestra was really cranking, the levels stayed in the 95 dB range for a reasonable time which surprised me being that far back in the hall. The peak level I recorded was 100.7 dB. My estimate is that it would be at least 10 dB higher in one of my favorite orchestra locations.
This just reinforced my feeling that if you have a moderately sensitive speaker system you need lots of power if you are going to get the emotional impact of a live orchestral performance from the likes of Mahler, Shostakovich, or Prokofiev. If you are a chamber music or folk fan you can probably get by with less. In my case, I decided that rather than worry about how an amplifier performs when clipping occurs, I would just have sufficient power that the amps never clip. Problem solved.
Just wanted to fill you in on the results I got. I hope to repeat it in the near future at one of my closer orchestra locations and will sent the results.
Tom