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 Post subject: Live performance SPLs
PostPosted: February 10th, 2024, 9:27 am 
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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: https://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. https://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. He was able to get comp tickets which was also good. 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


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PostPosted: February 10th, 2024, 9:42 am 
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Tom,
Great insight into SPL's for live classical performances! Will be interesting when you get a closer set of measurements.

The D-A iMM-6S mic is one I use for checks as the MS-6 has a TRRS connection for use with REW with the downloaded calibration data. I have not checked the SPL with my calibrator, but will check it now that I see yours was different than spec'd. Not something I worry too much about for speaker frequency response checks to adjust mains and subs.

Fun stuff!
Rich


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PostPosted: February 10th, 2024, 1:12 pm 
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Location: Parkville, Maryland
Here are some other considerations. Sitting at floor level in the typical concert hall you will be in a null area that can impact the quality of the sound and intensity. And let's not forget the Inverse Square laws that apply here. To wit -- the observed "intensity" of a sound source is inversely proportional to the square of the distance from the source. I found that the best sound (based on my experience at the Meyerhoff) can be obtained at the pressure zone -- right at the rear wall of the hall.

If the measurements at the floor level during a concert seem reasonable -- imagine what the musicians and the conductor have to deal with on stage. At the Meyerhoff -- the on-stage acoustics are not what the architect expected in that the musicians have trouble hearing each other.

Yet -- not every audiophile is fond of classical music. I am no fan of rock concerts (I treasure my hearing) that can be ear bleeding loud. How loud? I did a study for Hilton Hotels at a disco club in Puerto Rico and during during maximum activity on a Saturday night I measure 114-dba and it was damn loud to me while wearing ear protection. Hell -- they even violated OSHA requirements for the work place.

So what do "rockers" do to get the live experience at home? LOUD doesn't mean good -- yet . . .

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Walt


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PostPosted: February 10th, 2024, 1:44 pm 
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There are lots of problems with much of live rock music being painfully loud. When I go to live rock music (not often), I always wear my Etymotic ER12 earplugs which have been replaced by a newer version. They are better than the common foam plugs because the attenuation across the frequency spectrum is better. I have never had problems with live classical concerts because the levels are not so consistently high and the unamplified music has much lower distortion.


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PostPosted: February 10th, 2024, 6:39 pm 
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It's worth reading about the bassoon player, Bernard Garfield. He's now 99 years old.

https://en.wikipedia.org/wiki/Bernard_Garfield

I went to many Philly concerts from 1986 to 2020 before I moved back to Australia. I thought the sound was louder in the old Academy of Music than Verizon Hall, and of course, much drier. I've always preferred to sit further back and as high as possible. Overhangs kill the high frequencies.

Perhaps the loudest piece I heard was Muti conducting Turangalila in the Academy. When the orchestra is going full tilt with the ondes Martinot wailing away, that is loud!

https://en.wikipedia.org/wiki/Turangal%C3%AEla-Symphonie

https://en.wikipedia.org/wiki/Ondes_Martenot

ray


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PostPosted: February 11th, 2024, 11:02 am 
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Rocknroller here, also motorsports instructor\racer and recreational shooter. Protect your ears. I have pairs of these in my car and in my travel kit for music. I have both the -19 and the -26db versions depending on the show. I'll use them on a plane ride at this point. I use different protection for motorsports and shooting. Wish I had been using protection 30 years ago.

https://www.earasers.net/products/earasers


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PostPosted: February 12th, 2024, 2:17 pm 
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Well, I didn’t expect to be taking more live SPL measurements at a concert this soon, but yesterday the Lansdowne Symphony played at a local high school. I heard about it from a response to my last posting from Chris Gately another member of the PAAG. Here is some info on Chris: https://wemindthegap.com/chris-gately-t ... the-scene/ . He was recording the concert and thought it would be something I could measure. The Lansdowne Symphony is a well known local symphony in the Philadelphia area. https://lansdowneso.org/ Being a local group, they are not as large as the Philadelphia orchestra but that would allow me to choose my seat. The Philadelphia orchestra has about twice the number of performers and in some aspects can produce a larger sound. For example, the Lansdowne Orchestra has one contra bass and one tympani. The Philadelphia Orchestra has seven contra basses and two tympanis. However, the hall size at the Harrington High School where the performance was held is a fraction of the size of the Verizon Hall at the Kimmel Center. The performance included:

The Leonore Overture by Beethoven
The Pezzo Capriccioso for Cello & Orchestra by Tchaikovsky with guest cellist Kwanyun Loo
The Violin Concerto Finale by Tchaikovsky with guest violinist Noelle Streuber-Eden
The Symphony No 7 by Dvorak

More about the guest cellist and violinist later. For this performance I chose a seat six rows back and centered. Chris had two matched Earthworks mics set up about 15 feet high and 10 feet apart in the center. Those are just guesses as I didn’t measure the placements. The hall has some treatments both on stage and in the audience area so it is not overly bright. Chris said he will provide a copy of the performance so I can listen to it at home at the same level. Should be interesting, but the brain is notorious for losing comparative ability as time extends from the original performance. These pieces were not as dynamic as the Shostakovich 4th I heard on Friday, but the orchestra played with great vigor at times. Here are some average measurements I got through all sections.

The background sound when all was quiet between passages was around 48 dB. That was slightly higher than at the Verizon Hall. Quiet passages were in the 55 – 70 dB range. Medium passages were in the 75 – 80 dB range and loud passages were in the 85 – 92 dB range. The peak loudness occurred toward the end of the Dvorak piece and reached 100.0 dB. If you remember, the peak I got further back at the Shostakovich performance was 100.7 dB. What this tells me is that peak and average SPLs that you will need to reproduce if you are looking for realism are not too different when going to different venues with different performances when dynamic music is involved. This is not a problem if you listen at lower levels, but to get concert hall realism in most homes, you need speakers with significant linear displacement. I’m not talking about sensitivity here, but rather the ability of the drivers to move a sufficient volume of air without distorting. If they have enough displacement capability, then the issue of sensitivity comes into play dictating the amount of power needed.

Finally, a word about the two guest instrumentalists. Both were teenagers and their performances were amazing. I got goosebumps listening to them. The audience erupted in applause at the end of each of their performances. It is reassuring that there is still enough interest in classical music to motivate youngsters such as this to such a high level of performance. Years ago, a friend who did a lot of recordings for NPR did a concert in Florida where all of the performers were teenagers. The sound was great. There is still hope.

Tom


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