[Mag]

I took my spl meter to a Chili Pepper concert awhile back. The sound was terrible as it was in an arena, so I was major disappointed, but it showed me that a home stereo has an advantage over the real thing in terms of clarity and quality of the sound although it may lack live realism.
  Anyways from where I was seated up in the rafters, the concert measured only around 95 db, much lower than I was anticapating. But when the crowd was cheering for an encore, it was a whopping 115 db. That's the kind of noise that can cause permenant ear damage. Fortunately I was wearing ear plugs.
At home I typically listen at about 92 db, more so when I'm in the mood to rock. Why because that's what most instruments emit their natural tonal characteristics at, some of coarse are louder but the vast majority is at the 92 db range. So its at this level that music sounds are natural and realistic without my brain having to compensate by making any mental adjustments for tonal charateristics, etc..
One argument I was making for home use was the scale used. From what I understand the 'A' scale is the standard measurement that most accurately reflects human hearing. So lets say you measure 92 db on a music passage. I know that's loud but it doesn't tell me how much bass your system is generating. Now if I use 'C' weighting and measure 110 db, that would indicate to anyone familiar with the scale that ones stereo is generating alot of bass even though on the 'A' scale it only indicating 92 db. You see how misleading that can be. It also doesn't indicate how much power is being used, as it takes way more watts to generate a 110 db 'C' weighted measurement.
I find with my best DTS recording, because of the detail in the recording that my speakers are working much harder. And after a few hours of play of this dts recording that one of my speaker tweeters was distorting. It was very hot to the touch and I suspect it was close to overheating. Not something I encountered before with any other recording. Also it took way more power. When I tried to push the db to 95 db, bar level, my amps would clip, indicating that there was no more reserve power. With a cd recording 95 db could still be acheived. So db readings can be misleading as well to how much power is being used, as detailed music requires more power in generating articulate bass.

Just my .02 cents

[BobRex]

Roger, maybe I missed it, but did you also mention the 3dB gain from stereo?

That's something to ponder. I will say that if you have one speaker playing (as done by swinging the balance to the right or disconnecting the other speaker) and you bring the other one in back in  the meter will go up  6dB for mono information. For uncorrelated noise (pink or white) you are correct, the meter will go up 3 dB.

As to 3 vs 6 dB are you considering the added amplifier/acoustic power that another channel produces or are you keeping total amp output constant?

I'm looking at it keeping the amp output as the constant.  Which is how most people would consider it, forgetting that driving both channels increases the available output power.  From my experience, most people don't consider both channels driven as an additive power function, the just think in terms of rated capacity, i.e.; a 100 watt amp actually can deliver 200 watts (both channels driven), yet few people ever think in those terms.  So when the queston comes up as: "How loudly will my 100 watt amp play with the Gazinta 500 speakers?, most people respond by determining the output of one channel, forgetting that it's a stereo amp.

[rabpaul]

Another question: I'm having a running argument with my wife about what the appropriate volume level should be when listening to classical music . Can anyone tell me approximately what the spl might be (on the loudest passages), in the dress circle say, at a symphony concert?

If I can get an answer to this question, and the question about the analogue vs digital Radio Shack meter I intend to get one.

I was told that you have to set the volume at home such that you can just hear the quiet passages in classical music. If you choose not to, the loud passages can become very loud. I would in any case get a RS meter if only just to get an idea of just how loud you are listening. This is what I did to show my wife and family that I was well within the safe limits which as per my measurements from the listening position has never gone above 85dB.

According to tables I have seen, here are the limits before hearing damage occurs:
for 8 hours @ 90 dB
for 2 hours @ 100 dB
for 30 minutes @ 110 dB

[Roger A. Modjeski]

I am pleased to see that this topic has more views and replies than any other topic on our circle. More than half of the conversations I have with customers hinge on this important issue. I helped a customer in Asia determine that he was using less than 0.1 watts yet he still wanted to hear an RM-200. Although it's good for business to sell the bigger amps, that is not by goal. My goal is to provide the best amplifier for the person's needs. While he thought bigger amps sounded better many of us believe just the opposite; that smaller amplifiers sound better.

Were I to make a 30 watt per channel amplifier using the same tubes and circuit of an RM-200 it would sound better because I could run higher bias in the tubes, run them in triode and have no feedback. If the listener determines his power peaks to be less than 30 watts there is no need for 100 watts.

Let's keep this topic going. This knowledge is essential to make wise choices of amplifier/speaker/listener combinations.

[JLM]

Yes, my experience is that most audiophiles do critical listening at 80 dB or below.  They way overestimate the sound pressure and frequency extremes they listen to.  It very easy to acclaimate or become conditioned to a particular spl and/or frequency range.  The last time I brought my beasty single driver speakers to a SET based audiofest the natives were shocked to find out how much of their recordings had been missing.  They were quite dumbfounded and confused when they heard something other than the thin/unbalanced the sound they were used to.

My rule of thumb is that the measured efficiency in a "typical" living room (say 12 ft x 20 ft) equals the standard 1 meter distance in a anechoic chamber (that manufacturers use for rating speaker efficiency) due to room reflections and having two channels.  The range of "proper" distances (speakers and listener away from walls) away the speakers in a room that size makes it difference as its limited to between 5 - 10 feet.  Obviously smaller rooms will play louder and larger softer.

Loss of a commanding grip, loss of macro-dynamics, and collapse of the soundstage are reasons why I recommend sizing amps based the above with the "half way accepted" peaks of 105 dB for classical, 105 jazz, and 110 rock versus the levels we hear.  Also keep in mind that we're always listening above whatever background noise is present, which at home is normally 30 - 50 dB.  OTOH I'm ready to "give back" 3 dB or so for the soft clipping characteristics of tubes.  BTW the last symphonic concert I attended probably didn't get above 75 dB, so it really depends on the hall, where you sit (we were in the 4th row - we rushed), and the mucial selections.

I'm too old to go to rock concerts anymore, but still have a hard time understanding why you'd go to a concert wearing earplugs.  Hopefully they provide quite a visual show as the sound in an arena via a PA system and earplugs must be horrible.

[Roger A. Modjeski]

Happy New year,

I am bumping this topic to the head of the list to aquaint a new member with our circle and this most important measurement. Remember that SPL levels vary more between listeners than between speakers. Read all my posts on this topic to know why this is so and the advantages of having an amplifier of the right power for your listening.

The new price list has several examples of what can be done on the RM-200 platform. This has become my most "tuned" amplifier, so much so that I am winding transformers myself. In doing so I have pushed the high end response close to 100KHz and balanced the halves of the primary to have equal response (that's a tough one). More on this later.

http://www.ramlabs-musicreference.com/pricelist.html

[Scottdazzle]

I'm too old to go to rock concerts anymore, but still have a hard time understanding why you'd go to a concert wearing earplugs.  Hopefully they provide quite a visual show as the sound in an arena via a PA system and earplugs must be horrible.

I gave up on arena type concerts after I got permanent tinnitus at a concert in 1984.  I use earplugs at concerts at clubs to this day because I love music too much to give up the live experience altogether, but I've concluded that most sound men are going deaf.  They keep raising the volume, year after year, apparently believing that it's the same loudness that it ever was!  Even clubs that feature artists who do not want or require ear-splitting volumes (Maria Muldaur comes to mind as a recent example) are ill-served by sound men who apparently can't hear anything below 100 dB.

[jamesgarvin]

I think it depends more upon the venue. Fortunately, despite the concerts I have attended, I, at the ripe old age of 41, can still hear a 16k hz tone, but not an 18k hz tone. I've noticed that rock concerts in my local open air stadium, while loud, are tolerable. The same acts I've seen in Pennslyvania were excruciatingly loud. For some years now, I've carried ear plugs with me in the event that I need them. I've also noticed that many sound men turn up the volume during the course of the concert. These so called "sound men" are either ignorant, deaf, or both.

[DustyC]

Everything is getting louder.    I routinely wear earplugs to the movie theater, and to any concert that I know will have miking. I went to a choir concert at a church. they used no mikes and the sound was heavenly! I don't think it was above 80db on the loudest climaxes, but the real joy was when they sang softly, I found myself holding my breath just to hear the echos tail off!
I've noticed that there is always a lot of discusion on how loud a speaker will play but not much is said on how good it sounds at a very low level. FWIW I listen at about 85db on peaks when the music calls for it and about 95 to 98db on big band climaxes (when the wife isn't home). Anything above that level in my room and it turns to mush. I can use a single 75 watt tube amp for about 95% of my listening.

[darrenyeats]

What I imagine is going on in the reader's mind (given those quotes and questions) is the assumption that one can measure frequency response in their room with this meter. The simple answer is you can't. Standing waves and reflections will cause the meter to swing wildly with small changes in frequency and the numbers will be meaningless. The best way of testing a speaker's frequency response is a tone-burst generator and an oscilloscope. We did this at Beveridge and I do it for all my speaker tests. The burst is all over by the time any reflection comes back to the mic. The burst amplitude is recorded and, even more valuable, I get to see the shape of the burst. MLSSA can not do this and frankly satisfying MLSSA has resulted in some pretty bad sounding speakers. Harold Beveridge (we called him Bev) often said to speaker makers when shown their frequency response curves "Yea, that's great, now what does it look like when you move the microphone". He could move the mic all over the place and the response was virtually unaffected.

After experimenting a lot with EQ I think you're right that measuring "in-room frequency response" is difficult and for the most part a waste of time. But I think the impulse responses used in digital room correction seem to give very erratic frequency response curves also. I'm not sure why but they have a comb-like response and I find it hard to believe that correcting so drastically over a few Hz one way then the other is what the ear needs. I understand the idea of the impulse is to reduce or eliminate the room reflections from consideration but in practice these weird FRs I see plotted on DRC sites look like comb-filtering...can you shed light on this? I've had a lot more success in getting smooth curves with a calibrated sound meter with WARBLE TONES. Warble tones are excellent for evening out the comb filtering and with these you can move the mic around without significant differences. Nevertheless even with these smooth curves I've found doing corrective in-room EQ hurts the naturalness of the sound at almost all frequencies.

BUT not in the bass region. When it comes to bass (about 100Hz and lower) warble tone FR measurements and EQ are valuable. Above the bass frequencies reflections occur but in the bass standing waves occur. It's a different way of interacting with the room and it is perceived differently by the ear/brain. You can't really separate out room interaction from speaker response in the bass, it's all one entity. I have found it valuable to measure in-room FR with warble tones and EQ it below about 100Hz. In fact, personally I wouldn't live without it now, it makes such a positive difference. However, I leave everything above around 100Hz-125Hz completely un-EQ'd to keep the naturalness.

A 10Hz to 200Hz calibration for the RS SPL meter using fine steps and qualified by catalogue number:
http://www.hometheatershack.com/forums/downloads-area/19-downloads-page.html (registration required).

AFAIK the best type of speaker for even in-room bass response is dipole. And as far as measurements for speaker design go I think outdoors on a tall pole is the ideal.

As I write this last part I recall a reviewer who wanted to review my 300 watt monoblocks. I asked what speaker sensitivity at which he listened. He already had determined he used just a watt or two so I suggested the RM-10 (my SE amps came later). He told me he could tell the difference between a 100 watt and 300 watt amp even at those levels. I did not send him a unit for review.

I'm not in favour of using overdriven tube amps as a kind of compressing filter, because I don't think compression is good. However, I do agree that having a too-powerful amp/speaker combo is bad. There is a lot said about the qualities of SE amps etc but don't forget a lot of less powerful SS amps can sound just fine. I remember the Cambridge Audio A5 integrated from the early 90s - nice detailed sound as I recall. The reason less powerful amps can have an advantage (at the right volume levels) is clear enough. With over-powered amps/speaker you need to reduce the gain, and using a low gain hurts the effective SNR. In laymans terms less powerful equipment can dig out smaller details, not because it uses a superior technology which only works at lower power, but just because it is lower powered!
Darren