[Russell Dawkins]

Good advise from JLM re: headroom allowances. Those are approximately the numbers I would choose. It is important to realize that power levels shown on a mechanical meter, or even a string of LEDs, can be as much as 15dB shy of brief transients, even on high end professional gear. I have been caught out on this recording piano which can be both  dynamic and smooth at the same time, the dynamics triggering overload distortion and the smoothness allowing it to be clearly heard. Makes you understand why the piano is classed as a percussion instrument.

[bhobba]

IMO the amp must provide a commanding grip over the speakers in order to reproduce the bass control and dynamics of real music.  I've listened to several SETs, other tube amps, digital amps, and of course solid state up to 200 wpc with speakers ranging from 86 dB/w/m to 104 dB/w/m.  It doesn't take 110 dB continous spls or anything close to a golden ear to hear what a commanding grip is like.

I must say except on speakers that are a difficult load like my old Gale 402's and Axis LS88's I have never heard it.  And even for difficult loads I have found passive biamping to usually be a good fix.  Pity I did not know that for my old Gales - I lived with not being able to get the most out of them for years.  However I did learn the virtues of flea powered amps and listening at low levels from them.  And from responses I have heard from others it seems I am not the only one with this opinion ie that low powered amps into moderately efficient speakers is fine as long as they are not a difficult load - I have never heard this 'grip' you are talking about except at higher volume levels.  But hey - what would life be if everyone thought the same.

Public service annoucement: Extended exposure to 85 dB or more will lead to permanent hearing loss and possible permanent pain. So I critical listen (mostly jazz) at around 75 dB averages and less for classical. The spl meter taught me that most live classical music is below 60 dB. Size your amp to provide 10 dB headroom over your rock music playback levels, 15 dB over your jazz playback levels, and 25 dB over your classical playback levels (for your given speaker efficiency).

Could not agree more.  I wish others would also post the facts.  Sane listening levels should never exceed 80db average at your listening position - 75db is even better IMHO.  And while classical music can reach levels of 105db peak in a concert hall with orchestra and chorus it is rare.  Levels of 60 db are much more common.  Grand pianos can reach up to 109db peak at the piano - but who listens at the piano?  Is the pianists view a particularly good one?  Installers comment that people rarely exceed 110 db peak at the speakers.  I believe sane listening would usually not exceed 100db (which is only half a loud as 110db anyway).  In fact I have found I never exceed 80db average at 1 meter from the speakers - usually less.  I was recently having a discussion with someone who purchased a pair of SP continuums which are 91db efficient when fed with the standard 8ohm watt (ie 2.81v).  I was asking him to at least give a Charlize a try:
http://diyparadise.com/charlize.html
For $90 - what a bargain.  Nope - he was influenced by others who claimed you need heaps of power - 600W or more.  Using your figures however reveals a different story.  He listens at 2 meters so it is 6db down from 1 meter.  For a stereo pair this would correspond to 94 db when fed with 1 watt in both channels - or 88 db at the listening position.  Using your figures we have:
For rock and 80db average with 10 db headroom - less than 2W.  Wind it up to the max 85 db and we have about a majestic 6w.
For Jazz - 75db average with 15db headroom - less than 2 watts again.
For classical - 60 db average with 25 db headroom - less than 1 watt.

Food for thought.

Thanks
Bill

[kfr01]

Public service announcement:  for most ears it takes over 3 hours of exposure at 85db to have a permanent hearing loss effect.  (and this is being very conservative) (http://www.dangerousdecibels.org/hearingloss.cfm)

I agree with the 75db listening level, most of the time.

However, sometimes I like to sit down with a sipping drink and recreate a live jazz club atmosphere-me in the front row.  Sometimes I like to slip away to a hard rock or heavy metal concert.  Now we're talking some louder listening-and don't forget the transients.  I'm not going to damage my hearing when listening at a 90db average for an hour or so.  Combine the fact that my ceilings are very tall, listening room very open, speakers ~86db efficient and 3 meters away, and I need some decent power.  Not 600watts, but more than 6w if I want the transients to be controlled.  

A low wattage amplifier would suit me; most of the time.  But for those times when I want to open her up a bit, I like having a healthy dose of headroom.

[bhobba]

Hi

I agree with the 75db listening level, most of the time. However, sometimes I like to sit down with a sipping drink and recreate a live jazz club atmosphere-me in the front row. Sometimes I like to slip away to a hard rock or heavy metal concert. Now we're talking some louder listening-and don't forget the transients. I'm not going to damage my hearing when listening at a 90db average for an hour or so. Combine the fact that my ceilings are very tall, listening room very open, speakers ~86db efficient and 3 meters away, and I need some decent power. Not 600watts, but more than 6w if I want the transients to be controlled. A low wattage amplifier would suit me; most of the time. But for those times when I want to open her up a bit, I like having a healthy dose of headroom.

Yes. But let us look at the economics of it.  An audiophile quality low power amp such as those nifty 8w jobs from Boulder or a Chlarize and a sanely priced high power job like a Panny x55 (all up about $600.00) would be a reasonable compromise and cheaper than say two Nuforce amps ($1600.00). Then simply switch amps if you want higher power.  No prizes for guessing for the route I am thinking about.  I will get a Panny to get it working then invest in a fully tricked out Chlarize for critical listening.  Later I am interested in a DEQX - the price is bit high up front for me at present.

Thanks
Bill

[JoshK]

But economics assumes all the participants are rational....    

I agree with your logic Bill, but I think many audiophiles aren't into swapping out amps for the type of music the feel like playing, even though it is relatively simple and would cut back significantly on cost. They would rather rationalize (?) what they want based on irrational logic. That is what hobbies are about I guess.  I am not different.

[Rocket]

Hi Guys,

Just thought i'd say that i've been reading this thread with interest and it seems like you guys really know what your talking about.

I've had a few amplifiers thru my system this year which include;

aksa 100 nirvana plus
ps audio hca - 2 (which includes tricked out mods)
sonic impact (running on ac)
odyssey khartago
spread spectrum technologies 'son of ampzilla'

Anyway just thought i'd say that i liked the little sonic impact in my system but it kept clipping at the levels i like to hear music in my system.  My speakers are relatively efficient 90db they dip below 4 ohms and i find that the little amplifier just doesn't give me enough power to drive them properly

I always seem to go back to about 100 watts per channel in my system and it works well for me.  There are lots of different affordable amplifiers that you can buy on the secondhand market.  The nuforce amps in australia retail for about $2800au which aren't cheap but they do sound very nice.

If you can solder i would suggest an aksa amplifier.  I'll have to buy an spl meter and find out if i'm damaging my hearing   .

Regards

Rod

btw how much can you buy a panasonic digital amp for in australia?  i saw an xr55 for $800au last year here in perth for sale.

[bhobba]

Hi Rocket

Nice to hear from you again.

Anyway just thought i'd say that i liked the little sonic impact in my system but it kept clipping at the levels i like to hear music in my system. My speakers are relatively efficient 90db they dip below 4 ohms and i find that the little amplifier just doesn't give me enough power to drive them properly

I have recently heard it as well and agree - although in the system I heard it did not clip - at least to my ears.  However the Chlarize for example is supposed to drive loads better than the sonic impact - and you cant go wrong at the price.
http://www.tnt-audio.com/ampli/tripath_amps_e.html
http://www.diyaudio.com/forums/showthread/t-66269.html
http://www.diyaudio.com/forums/showthread/t-65780.html
'Charlize do very well with low efficiency speakers, at least at low and moderate level. I use it with some big 3-way (85dB, 4 ohm) with great result.'
People have been driving Gale 402's with them no problem - and they are terrible speakers to drive.  Simply add a battery or an el chepo SMPS.  Having said that though dips below 4 ohms are not good for any amp but passive biamping sometimes helps.

btw how much can you buy a Panasonic digital amp for in australia? i saw an xr55 for $800au last year here in perth for sale.

Contact JB Hi Fi - $600 - $700 Australian and it allows bi amping as well.

Thanks
Bill

[JLM]

System matching must also be considered.  Reportedly the Sonic Impact variants don't like low impedance/low efficiency speakers.  My experience with the Clari-T is that it clips very "softly" (continuing to turn up the volume "too much" has almost no effect).

With my 89 dB/w/m, 8 ohm, 30 - 20,000 Hz, very amp friendly single driver speakers (Bob Brines FTA-2000) I'm definitely not suffering with my 6 wpc Clari-T amp, but the extra 8 dB of gain that Teac offered blew me away.  Hearing the difference was an epathany and would have been to anyone close to being called an audiophile.  Many musical forms don't have enough dynamic range and some speakers just don't have power handling/dynamic capabilities to take advantage of additional power.  This is particularily true of low efficiency designs, such as those with small sealed cabinets.  My speakers are large transmission line designs and being single driver based, are by default active designs with the advantages of direct driver/amp connection.  So they should be able to take full advantage of extra power.  The NuForce amps would provide an additional 8 dB of gain over the Teacs, but their cost is also significantly higher too and cannot be modded for battery powered use.

Listening levels do introduce lots of variables, but the marketing hype behind "needing" huge amps and extreme spls grinds me.  Most of the time folks are listening with less than 1 wpc.  Similar to cars, most of the time folks are only using 25 horsepower or less, yet there are times when additioned horsepower is needed (more often wanted).  For audio, my goal is around 100 dB, for cars about 20 pounds/hp.

I prefer to rate amps in terms of decibels of gain, not watts as that is what we hear (and isn't that the bottom line anyway?).  So 1 wpc is 0 dB of gain (that's what the speaker efficiency rating is based on).  Every doubling of power adds 3 dB of gain (sounding half again as loud) and every tenfold increase in watts adds 10 dB of gain (sounding twice as loud).  So a 600 wpc amp can play twice as loud as a 60 wpc amp and 4 times as loud as my little 6 wpc Clari-T.  So obviously speaker efficiency can make more of a difference than wattage ratings.  And the difference between 40 and 50 or 80 and 100 wpc is only 1 dB (the smallest incremental difference in volume that can be humanly preceived), so we can get over those small differences too.

[ctviggen]

The smallest increase in volume that can be perceived varies depending on a number of factors.  See:

http://www.audioholics.com/techtips/roomacoustics/HumanHearingAmplitude.php

Toward the bottom.  Human hearing is complex!