paranoid listener-damaging speakers?

I am one of those guys who is always wondering if he is listening too loud for his speakers capability. my system briefly consists of a prima luna prologue 2 integrated, custom eton 2 way speakers with a silk dome tweeter and 8 inch midrange, with a mhdt labs constantine dac. my room is 15x12 feet roughly. i listen about 6 feet away.
I like to listen at a level where i can feel the bass and midbass and feel that the speakers are loud enough to recreate their original acoustic on the recording. is there a rough guide to know if i am listening too loud without a meter? i will occasinally think i hear some distortion on loud passages, but it may be on the recording, i may just be paranoid? advice please? thanks.
Buy a $50 Radio Shack meter. You've probably got at least $2,000 invested in your system so you've got something to protect in the way of equipment. It is very helpful to have a solid reference point when you're talking volume. It appears you like to listen "loud" but without an outside reference readers can only guess what that really means.
Without a meter, you're totally guessing. With a dB meter, you can loosely define your margin of safety.

You get the specs for your speakers' sensitivity (e.g., 87 dB @1 meter w/1 watt input), and their power handling capacity. These specs may be a little harder to get in your case since your speakers are custom made from a (presumably) Eton kit. You get the specs for your amplifier (40 wpc).

You double the amp power output for every 3 dB increase in SPL. So if, for example, your speakers are putting out 87 dB at 1w input, they're theoretically putting out about 16 dB more (103 dB) at 40 watts input. You may be able to add 2-3 dB output to the 1w input because you're listening to 2 speakers instead of one and another couple dB because you're listening in a room instead of an anechoic chamber.

Anyway, if you know the sensitivity rating and the max power handling, you can measure with a Radio Shack dB Meter when your speakers reach an SPL approx. equal to the amp's clean output max, after which it starts to clip and could damage your tweeters. Or if your speakers can't absorb as much power as the amp can put out cleanly (unlikely in the case of 40 wpc), you turn down the volume at the point the speakers are putting out more SPLs than their power handling indicates they can absorb.

For example, if your speakers have a sensitivity of 87 dB you hear distortion around 103-106 dB consistently from recording to recording, it's probably your amp being overdriven.
On a small two way when it sounds really "loud" then there is usually distortion either on the system or the recording. It is not well known but undistorted music can be played much louder without fatigue or sounding loud than distorted music many modern pop/rock CD's are badly distorted from audio compression -they sound harsh and loud at modest SPLs.
I would worry more about damaging your ears. Eton drivers are only $200 each or so. Your ears are priceless. As a rough estimate, try talking at a normal volume level, as if you were talking to someone else in the room. If you can't hear your own voise very well, the music is really loud.
As for your speakers, it is very frequency dependent. The more very low frequency content, the less loud you can play them before they reach their limits. there are at least 2 ways to damage a speaker - emlting the voice coil and bottoming out the voice coil. I'm not swure there's a good way to tell your overheating the voice coil until it's too late. If you hear a buzzing sound or a loud crack on loud deep bass notes, your hitting the voice coil against the magnets, and are at risk of bending the voice coil and ruining the speaker.
When you hear distortion at a loud volume, turn it down a bit to see if you hear the same distortion. If you do, it's the recording. If you don't, you're over driving something in your system.
Not able to shed any further light on your question, but Shadorne's point put something into focus that had been perplexing me for awhile.

"It is not well known but undistorted music can be played much louder without fatigue".

I had recently converted my little entry level Arcam/Magnepan system to a biamp system through an active crossover. Despite the documented gains in power efficiency's (no passive crossovers, etc.) I found myself listening comfortably and enjoyably at much higher levels as judged by the level of attenuation at the preamp.

I had noted the fact, but didn't understand the dynamic. Shadorne's statement just rang so true and explains my observations. Distortion, whether on the recording or in the playback system, really is a factor in percieved volume.

In my case, the distortion was from overdriving the little amplifiers in a non-active system and from the passive crossovers in the speakers. Free of that distortion, I enjoy much higher volumes for longer periods. Put on a highly compressed or poorly recorded track (yes, I do also love mainstream/pop rock like U2 and Audioslave) and I am reaching for the remote to turn down the volume.

Jim S.
You stated, you like to hear and feel the bass, As do I. Your speakers it seems, need alot of volume to start hitting you the way you like it. What you need to do if you wish to keep those speakers, is to add a subwoofer to your system. You will get the bass slam you are looking for without having to crank your speakers to the max. A sub will also give you a nice bass fullness even at low volumes, if that is your desire.
Djwilbourn - When you overdrive speakers you might damage woofers but when you overdrive amplifier than you'll damage tweeters. In either case you'll hear distortions before it happens.

In case of woofers I would be afraid of mechanical damage and not the overheating since average music power is only few percent of peak power. Tweeters usually fail when amplifier is clipping - sending a lot of high frequency energy (harmonics) to tweeter.
Jim S.

Well I am glad to see my comment helped at least one person.

Basically you need to think of your ears/brain as responding to the overall acoustic power in your room. A squashed distorted signal may have a much higher RMS (Root Mean Square) power than a nicely shaped sine wave with huge dynamics. (Distortion adds all kinds of harmonics that were not there. Compression flattens everything so that the sound becomes droningly monotonous at the same time as it adds all kinds of harmonic distortion and creates an all frequency at once assault on the hearing)

This is all very counterintuitive but real instruments (like a drum set) actually produce extremely high acoustic energy even if this only instantaneous and over a few precise frequencies. Ever notice how you can clearly hear a marching bands' single bass drum playing clearly from all the way across a football field. Average power of this kind of signal from a real group of instruments may actually be quite low (on AVERAGE) over long periods and across the entire frequency spectrum. Unfortunately compression and distortion from either a CD source (caused by mastering engineer) or from a the Hi-Fi system itself will turn the sound from a bunch of real instruments into highish energy for very long periods of time and over much of the frequency range and which leads to a very high AVERAGE power - so you are forced to turn the volume down and admit that it all sounds extremely loud and unpleasant. (which is apparently what Metallica, Garbage and many others are trying to achieve on their hypercompressed CD's - loud all the time at all frequencies - a complete and total assault on your ear and nerves)

To me this is the single biggest difference between live shows / real instruments, which sound beautiful and effortless (even when loud), and an overly stressed Hi-Fi or an overly compressed recording. Note that the distortion mechanism is different - in one case it is deliberately added by the mastering engineer and in the other case the hi-fi system cannot handle the true dynamics of real instruments.

Here is some explanation that illustrates the problem
When live music is recorded without amplitude compression or limiting, the resulting signal contains brief peaks of very much higher amplitude (20 dB or more) than the mean, and since power is proportional to the square of signal voltage their reproduction would require an amplifier capable of providing brief peaks of power around a hundred times greater than the average level. Thus the ideal 100-watt audio system would need to be capable of handling brief peaks of 10,000 watts in order to avoid clipping (see Programme levels).
The laymans article goes on to explain how tri-amping or quad-amping or by going to active speakers can get around the 10,000 Watts problem by dividing up the power demands across the frequency spectrum between drivers with dedicated amps. This is important on percussion where a brief instantaneous broad spectrum of frequencies leads to extremely high momentary power requirements. Another trick is circuitry such as momentary gain reduction to prevent blowing equipment up because of a crescendo.
Shadorne -

"Thus the ideal 100-watt audio system would need to be capable of handling brief peaks of 10,000 watts in order to avoid clipping (see Programme levels)."

That would is true if average level is insane 100W. In typical home audio system peaks are reaching 100W and average power is around 1W - same ratio.

We could look differently at these ratios. Half as loud means 1/10 of the power.
In typical home audio system peaks are reaching 100W and average power is around 1W - same ratio.

Yes - exactly - that was my point - this is barely beginning to compete with the dynamics of real instruments unless you have high efficieny horns and even then you would be obliged to add a large 1000 watt sub in most domestic spaces to cover below 90 Hz.

Speakers are woefully inefficient unless you go to horns...
Shadorne - With the amount of money some people spend on audio pursuit every year it might be cheaper to hire symphony orchestra for home performances - nothing beats real thing.

uhmmm... worry about your ears not the speakers.
guys, i really appreciate your input so far. i am surmising that 1. i need an spl meter and 2. i am hearing the distortion in the tweeter so maybe i am clipping the amp a bit, although i thought 40 watts of tube power would be more than enough to drive this fairly simple two way. feel free to continue the discussion and advice.
Djwilbourn said: " although i thought 40 watts of tube power would be more than enough..."
That, my friend, is why you need a SPL meter. Everything is just conjecture and speculation until you get a solid reference point for your particular flavor of "loud."

If you're trying to push 110 dB of chest-thumping bass and window-rattling volume from speakers of currently unknown efficiency, the odds of that are not on your side with 40 watts.

If 85 or 90 dB meets your definition of "loud" then chances are a lot better that your power is sufficient if your speakers are medium efficiency or better.

You've been given a wealth of information to work with. But now the ball is in your court and you've got some legwork to do.
At the end of the day it's your ears that determine the level of loudness they can take although measurements can be taken with an SPL meter on the range of dB you are getting. Everybody's tolerance towards loudness may not be similar. I would concur with advice from several folks in protecting your ears from potential damage, more so since you mentioned you like to listen to your music at high volume levels. Prolonged exposure to loud music may lead to tinnitus. Your ears are more valuable than the speakers, so don't worry too much about damaging the speakers. Just listen at a comfortable zone -your ears should be able to let you know.

I used to be like you listening at high volume levels but have toned down a lot after visiting the ENT specialist last year due to suspected tinnitus(vibration to my right ear). Fortunately I was told that I may be suffering from hyperacusis which was caused by listening to music at insane levels, not tinnitus. I was advised not to listen to music at insane levels to prevent recurrence of this "vibration".
As someone else mentioned - get an spl meter. As to hearing loss due to acoustic trauma - again, get an spl meter and take a look at reputable medical/audiology sites as to the level and duration of exposure that is unhealthy in this regard. What is subjectively loud depends on a lot of things, distortion will sound loud and distortion comes into play as to what will damage your speakers. Conversly, distortion does not come into play with what will damage your hearing. Actually , the highly distorted sound will likely cause you to turn the volume down prior to any damage to your hearing. It isn't the perceived loudness that damages your hearing, it is the force of the sound wave hitting the anatomical structures.
"If it's too loud, you're too old!!"

No really, if there is no clipping/distortion you should be fine. I have a very large room and I have not idea what level's I listen at, but, I know we cannot talk to each other in the room while the music is on.

The louder, the better. Well, as long as you don't hurt your hearing.
Well, I forgot to say, if there is distortion I agree you either need more power from an amp, or if you love your amp, more efficient speakers. I love the Tannoy and Klipsch Heritage sound with tubes!!
so when i get this spl meter; any tips on how to correctly do the measuring? from the listening chair? at 1 meter from 1 speaker? thanks
Specs for speakers are usually given at 1 meter from the speaker. As to your ears - the listening position.
Well guys i got that spl meter and did some measuring mostly at the listening position (6 feet away). my peaks seem to average in the low 80's db. does this sound reasonable for my speakers 8" two way floorstanders? i just want to be slightly conservative on driving these as i like the sound of them and want to keep them damage free. thanks for all the input thus far.
80 dB peaks is a very conservative listening level, particularly if you are listening to music with a wide dynamic range. Even for highly compressed music, 80 dB is conservative. The room is not large, the measurement was taken at a meaningful distance and if your amp was so underpowered as to have drastic clipping you would hear the distortion. Based on the above, it is highly unlikely that you are going to damage the drivers at that level.