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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!
thomp9015
dob
577 posts
 
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
Rafael
pauly
456 posts
 
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.

Regards
Paul
thomp9015 OP
79 posts
 
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
philjolet's avatar
philjolet
2,262 posts
 
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.
joelv's avatar
joelv
102 posts
 
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.
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