15 watts & 94 db eff. speakers: how loud?

With a Trends 15 watt t-amp and small tekton design speakers, with 6 inch fostex 167es, rated @ about 94db, i can get about 93-4 db sustained average (@ 1 meter per speaker) with peaks around 96-7. It sounds perfectly good, nice and clean, no treble break up, nothing different than @lower volumes, only louder.

BUT, at ANY higher volume the amp starts to clip. One hears of many such rigs with even lower wattage 300Bs and such, which is why i wanted the efficiency of the speaker (as well as its single driver design). I've never really used a solid state, much less digital amp before. I'm wondering, is this the nature of hard clipping in digital amps, to begin before there is any real noticeable distortion or is something wrong with the amp? Is this generally how solid state clips? How loud should speakers of this efficiency go with this many t-watts? Finally, how many watts do I need to have some more head room (let's face it, I'm only comfortable with my rig when I know I can accidentally destroy the speakers late one night) : )

Thanks in advance!
I'm wondering, is this the nature of hard clipping in digital amps, to begin before there is any real noticeable distortion or is something wrong with the amp?

Yes this is normal. SS amps generally clip all of a sudden and they can sound very bad when clipping. The main advantage of tubes is that they "soft clip" - a much more pleasant and often cherished sound. As a general rule you should try to ensure that SS amps do not clip with tubes it is a matter of taste - a bit of clipping can add significantly to their rich sound.


All The Best
thanks for the responses (rafael: thanks, the article was very interesting but a bit past my technical grasp of audiophilia and not quite to the point, but thanks, very useful for me overall though). it seems strange i would get no distortion, then clipping, and the clipping doesn't sound "very bad" shadorne, as i thought it would. it sounds like "nothing," like more of a momentary cut off, like the skipping of a record (it's not the cd player). anyway, i can accept that this is how the clipping manifests itself. but is this (about 93-4 db sustained average @ 1 meter per speaker, with peaks around 96-7) about the loudness i can expect from 15 digital watts and a 94 db efficient speaker? i've seen in other threads how loudness levels can be calculated with these parameters. it is really pretty loud and sounds very good but the speakers seem like they could go somewhat louder. the volume nob on the amp is barely over 1/4 of its travel!

anyway, thanks again guys
Speaker efficiency has bearing on the loudness ONLY. You complained on "... at ANY higher volume the amp starts to clip" and the artilce I referred to explains to you that its the speaker load, specifically its reactive load put demands on the amplifier. Amplifier power in rms is also meaningless - its peak voltage, peak current, their DURATION and heat dissipating capability of amplifier output stage - these are parameters which define when and if your amplifier will clip.

All These parameters can be found from the manufacturer of your amplifier and manufacturer of your speakers - if not on web site then by asking them directly.

Its obvious from your story that speakers/amplifiers is a poor match in rperoduction of musical peaks so do one of the following:

a) play at low volume (chamber music, country music etc)
b) change speakers
c) change amplifier

All The Best
Thomp9015, are you measuring the SPL to be 97db when you hear the clipping?

While 97db SPL does present a doubling of sound pressure from 94db, it will not sound twice as loud to you. It takes about a 10db increase in sound pressure for human to perceive something to be twice as loud.

thanks again raphael, i think i see your point in that what makes the amp clip is a complex of the factors you mentioned, i.e., durations of peak voltage and current, heat dissipation, etc. trends audio sends no reference material with their cheap little amps, i could find out i suppose but i am keeping the speakers anyway as they seem the better product, so i will as tekton about these parameters and amp suggestions. i might buy a cheap 30 watt creek 4230 amp to see how that works.

i just thought this simple design w/fostex 167e drivers would already have some pretty well known good low wattage amp matches. i was also trying to find out if the peaks i was getting were reasonable for that type of speaker, i.e., how much louder can i really expect to go regardless of how well the amp matches. thank you though for your patient clarification.

pauly, yes the clipping sets in around 97 db peaks, around 94 db average. btw, i was not perceiving or expecting any particular degree of quantitative change in my measures.

thanks again guys
I have found speaker and amplifier ratings to be misleading. You really just have to hear it for your self.

I easily drove 88db Trentes with a 18wpc Soro amplifier, they rocked! and when I switched to 94db AN speakers it did not seem much louder.

Of course a 3 db increase is not supposed to be audible to the human ear so maybe 6db is just a bit louder.
For the sake of argument, let's assume that RMS measurements aren't meaningless. Taking audio science at face value, there is a reason for your clipping problem.

The math goes like this: If 1 Watt produces 94db at 1M, then...

97db requires 10 Watts
100db requires 100 Watts

so your amp is behaving quite normally if it clips when the speakers are at SPLs higher than 97db.

As I understand it, it is the behavior near clipping that give many amps their characteristic sound. Triodes are supposed to sound "glorious" when distorting.

Clipping, however, doesn't sound good coming from any amp, tube, digital, or solid state.

If you need over 97db peaks in your room, basic audio physics rules say you need a more powerful amp. I'd try something that has peaks at 100 watts or more to get the dynamics you want.
Philjolet - huh? 3dB increase can be detected by most.

Joelv - huh? each 3dB increase requires around (not exact) double the power, not tenfold. so 97 requires 2 watts, 100 requires 4 watts.
3DB twice as loud. 1 watt 97db if 8 ohms. 2 watts 100db, 4 watts 103db. A fe166e in a BLH is a much diferant beast can play louder more dynamic than a fe167e in BR. The BR versions of fostex horn drivers are poor performing unless used in nearfield or at low volumes more power will not help. A SET tube amp might give a wee bit more SPL before sounding hard. You just reached the max SPL that this fe167e driver in the BR cabinet can produce before sounding poor. 1 reason we offer no BR fostex fullrange except f200a. Our FE126e and fe166e are all BLH. As they should be.
Johnk: 3dB = ~1,4x as loud. 6 dB = twice as loud. You know that, of course! It's sound *pressure* he's talking about.

Back on topic: in theory, your amp clips at ~103-104 dB. That's quite loud, btw!
I believe all seem to be wrong here, DOUBLE or twice as loud I belive is 10 db... So if your playing at a volume of 90 db 100 db would be necessary output to double it.. 3 db louder is notable, but not a TON louder, 6 db is a pretty solid increase but not double as loud.

Double "The power" wattage is required to do 3 db louder, but will not do 10 db louder in order to get double as loud.
rockadanny - I read (in TAS I think) that 3db is not detectable to the human ear and that 10db sounds like double the volume even though 3db is actually double when instruments are used.
thanks everyone, i'm in touch with the speaker manufacturer and working on an amp solution. johnk, fyi, to repeat the speakers never sound hard or poor or even distorted before clipping, they sound very good and then they begin cutting off and back on which i can only assume is clipping as it only happens at these higher volumes....from the sound, i am fairly certain they can play somewhat (not a lot)louder. obviously the question doesn't have the clearest of answers. i think it depends on the particulars of the amp, but i guess few have experience with the Trends 10.1 amp.
from http://www.enjoythemusic.com/magazine/manufacture/0907/

Secrets of Amplifier And Speaker Power
Requirements Revealed!
Alan Lofft as supplied by Axiom Audio

As audio/video hobbyists, most of us grew up thinking that if we have an amplifier with 50 watts of rated output power into 8-ohm speakers, and that combination produces reasonably clean and loud music, then by doubling the amplifier power to 100 watts per channel, the system would then play twice as loud. Many readers likely still believe that. Not so.
Although it's not the easiest thing to comprehend, doubling the amplifier power does not double the loudness. In the above example, the sound from the speakers would not be "twice as loud"; it would only be "a little louder," an increase of 3 decibels. How loud is that? Hearing tests with large groups of people have revealed that a one-decibel (1 dB) change in loudness is approximately the smallest audible step that the average listener can detect, so an increase of 3 dB most listeners term "slightly louder."
So why doesn't that 100-watt amplifier always sound twice as loud? Because the acoustic decibel--the decibel (dB) being the unit of measurement used worldwide to quantify the acoustic loudness of sound--has a peculiar relationship to amplifier power output measured in electrical watts. That relationship is called "logarithmic." If that word gives you an instant headache (nightmares of high-school math), then here's a simpler explanation:
If a sound gets louder by 3 decibels or "slightly louder," it takes twice as much electrical power from your receiver or amp to produce that modest increase. Therefore, a 100-watt amplifier will produce sound only slightly louder than a 50-watt amplifier.
So far, so good. But what if it's party time, and you're listening to music "very loud," a level defined as about 90 dB Sound Pressure Level (SPL), and your speakers are gobbling up swings of 15 to 20 watts per channel on those musical peaks.
Drink in hand, you advance to the volume control on your receiver thinking, "I'll just crank this up to make the music twice as loud," and you turn up the volume control until there's a 10 dB increase in the sound level. Now your party-time goal of "twice as loud" will make huge electrical demands on your nice little multi-channel receiver or power amp. The receiver must deliver ten times as much power to double the subjective loudness. Between 6 dB and 10 dB is double the volume level, where 6 dB is four times the power and 10 dB is 10 times the power. In the aforementioned example, the amp must produce 150 to 200 watts per channel for those peaks in loudness. Therefore, every 10-dB increase in acoustic loudness--from 80 dB to 90 dB, or 90 dB to 100 dB--requires ten times as much electrical power in watts.
That's all very well if you have a monster amplifier or multi-channel A/V receiver with huge reserves of power output (most of us don't). If not, watch out. Your receiver or amp may "clip" or distort (or both), which will put a clamp on the output of the amp. When you push your amplifier into overload or "clipping," several things may happen. First, the top and bottom of the waveforms (representing the audio signals) are clipped off, generating distortion. Next, the amplifier's protection circuits are activated, removing those portions of the signal that are causing the overload, generating distortion. And finally, the amplifier's power supply may fluctuate according to the demands of the music signals....

Simon Thacher's article in http://www.enjoythemusic.com/magazine/manufacture/0708/index.html

describes the distortions associated with reporduction of musical peaks - clipped or not clipped.

Print these two articles and keep for your references

All The Best
Apologies for my lecture on incorrect math- no more drinking and posting, I promise!

My numbers were supposed to be based on the general rule of 6db increments, not 3db, and for that, it obviously doesn't make sense that the amp is clipping. I even sounded so smug, how embarrassing. I'm terribly sorry to have added to the confusion.

I read (in TAS I think) that 3db is not detectable to the human ear and that 10db sounds like double the volume even though 3db is actually double when instruments are used.

I believe we can all agree that 3db is extremely "detectable" though. I believe 1db is the smallest increment the average human ear is supposed to be able to detect.

Just for reference, I'm a recording engineer by education. I promise you can hear a 3db increase. even from just one instrument.

You just won't need 10x as much power :)
rockadanny - I read (in TAS I think) that 3db is not detectable to the human ear and that 10db sounds like double the volume even though 3db is actually double when instruments are used.

Good critical ears can detect about 0.2 db SPL differences provided it is over a broad range of frequencies in the midrange (as would be the case with volume). Adjustment of treble, for example, by 0.2 db SPL is probably not audible for most people - around 1 db SPL change in treble would become audible to many.
"My numbers were supposed to be based on the general rule of 6db increments, not 3db, and for that, it obviously doesn't make sense that the amp is clipping." joelv

not sure why it doesn't make sense, could you elaborate for the technically challenged. thanks again for your help and no worries about your mistake, whatever it was : )
Thomp9015 and anyone interested -

I had posted, incorrectly, that:
The math goes like this: If 1 Watt produces 94db at 1M, then...

97db requires 10 Watts
100db requires 100 Watts

so your amp is behaving quite normally if it clips when the speakers are at SPLs higher than 97db.

Which should have read:

97db requires 2 Watts
100db requires 4 Watts

so it, in fact, does not make sense that a 15-Watt amp would clip when driving the speakers to 98 watts.

Thanks for the chance to redeem myself. :)
98 db, not Watts. Sheesh!
thank you again joelv, i must say that of everything written so far, and most all of it very useful, yours seems like the best answer to my original question, which is essentially: is this clipping to be expected, and you seem to be saying that it does not appear to be. although i'm about the last to know, my impression is that you are probably correct.

i've emailed both the amp distributor and speaker manufacturer...it may take some time but i will at least get some sort of straight forward response from them both and relay them to you. thanks thanks
Most people are blissfully unaware of compression from speakers. It is possible that your amp was actually putting out around 15 watts during transients and therefore clipping - it is simply that these transients did not translate to the peaks you expected to observe but were limited to 96-97 db SPL.

Explanations for this are - limited Xmax or thermal compression from the driver. Generally about 97% of what you throw at a speaker ends up as heat. The Xmax on this driver is a mere 0.6 mm - a tiny 1 inch voice coil ( no bigger than a tweeter voice coil) I mean $%#^& - what can you possibly expect out of a driver like this????

I have written several times in A'gon forums about the issue of prevalent use of cheap drivers (often used in expensive speakers). They work great at lower volumes but you cannot expect miracles. Soundstage (who do lab tests ast Canada's National Research Council facilities) state that the do not even test speakers with signals above 100 db SPL as this would DAMAGE MOST OF THEM!!!
shadorne, i see what you are saying, i've read a lot of your posts on this topic, just two unversed to put 2 and 2 together. it just seemed like the speaker was able to do more spls when it was clipping (no noticeable harshness or distortion). it does seem like a delicate little driver but compared to some others, it doesn't seem all that cheap. but within its limits it still sounds very nice for what it is. thanks, this has all helped me feel less in the dark.

I am not saying it is a bad driver. At $65 retail (probably less wholesale or in bulk) this is a great and well respected driver and will sound awesome at lower volumes than 97 DB SPL.

All I am really saying is not to expect too much - after all to get good clean loud sound above 100 db SPL you are probably looking at something much bigger - a three way or something with perhaps $600 or more worth of drivers. You know - don't expect miracles - or don't believe the math that suggests that a small 94 db SPL full range driver should be able to easily play 110 db spl comfortably (with pure theory suggesting that all you need is a big power amp).

Of course amplifier manufacturers often neglect to mention this as they are often trying to sell you higher end amps with more watts...in a sense they are competing with speaker manufacturers for a piece of your overall "system budget."
shadorne, you're absolutely right, don/t worry, i really love the speaker for what it is, i guess i'm really just trying to find that final volume margin of good sound from them, i know i'm very close, maybe already there, always looking past the horizon perhaps.

still, i would like to have enough headroom with an amp to hear some distortion from the speaker before the amp clips, i can't say why though, since i wouldn't listen to it distorting, i just want to make sure the amp is not the limiting factor in quality output (and also simply trying to understand the system's interrelationships), maybe i just have too much time on my hands : )
fwiw, eric alexander of tekton told me that he felt the amp is likely malfunctioning, as he said the speaker should go substantially louder with 15 watts, even 10 should be more than enough for peaks over 100dbs. i don't know if he is going on any more than the rated wpc or if he knows more about the Trends 10.1 t-amp. i've also contacted the amp distributor and will see what they have to say. i wish i could simply measure its output.
fyi, after much back and forth and many many opinions, it turns out the trends t-amp was faulty, though the exact problem remains indeterminate. audiomagus went above and beyond to try and determine the problem, even though they could not reproduce it on their bench. so they just sent me a a new one, even though i've had it well past the warranty period. anyway, this one works exactly as it should: it plays much louder with the volume knob going up well past 12:00 rather than the 9:00 on the old one. it really sounds very very good for the money. i KNEW those speakers would play much louder and i KNEW the amp must be faulty...oh ye of little faith ;) most of all, audiomagus really worked with me in real time over the computer to put in some quality time. i was very surprised considering what a modest purchase it was. well worth the effort from both a product and customer service standpoint. i hope they continue to prosper and encourage everyone to check out their small selection of gear...it is unusual stuff but this amp is exactly what i needed. thanks for everyone's help.

I owned an Audio Nte Meishu (9watts) with Avantgarde UNOs (91dB) and drove them to pretty loud volume where needed (Rock, Pop etc)

Flg2001 the Meishu is an extremely robust 9 watts fwiw