Why you need 500Wpc for good sound

[jdm56]

Where you need those kilowatt amps is on direct radiator subwoofers to keep up with the 50 watt amplifier on horns, which are 20 db more efficient, at least.

Amen to that! I think I could get by with 10 clean Watts on my LS2's. But my subs, that's another story! Give me all the power I can get!!

[WMcD]

Mike B. makes a good point about what happens when there are simultaneous sine waves and what it might mean about power, or voltage. Somewhat the subject of confusion. If our speaker and amps are hit with signals at 40 Hz, and 80 Hz, and 160 Hz, and 320 Hz and 640 Hz etc, we need a heck of lot of power as these add up. Is this why we need headroom and big amps? NO.

= = = =

BTW, MIke B., your comments about poop clothes distresses me. You are a full Jedi Knight with your EE. Don't doubt yourself, or the power of your mind. Smile.

= = = =

But let me suggest we think things through with waveforms and time.

Suppose we start with a mixer board with 10 inputs. We feed the inputs with sine waves of a common freq, in phase, at 0.707 volts rms. That would be 1 volt peak or 2 volts peak to peak. (This p-p is the 1.volt peak and -1 volt negative of the sine.) So we get 7.07 rms at the output. That means 10 volt on a peak or 20 volts peak to peak.

Further, if every input is limited to 0.707 volts rms with complicated music, the combined outputs will never add up to exceed 7.07 volts rms, or 20 volts peak to peak. A worst (or best) condition. In time.

But note well that this is the situation at the mixer board. It is not, repeat, not, the situation in our playback of recordings and playback.

That peak to peak limit is what is sent to the recording. That voltage analog is all we have to work with.

The recording has the same overall limits of voltage analog. And that is what we're feeding to an amp. Say on a CD we hit the "0 dB" maximum limit with all 16 bits turned on. That is the voltage limit.

Let us assume that our CD player and amplifer just happens to be set up so that the 7.07 voltage output of the mixing board results in the same 7.07 volt input to a speaker. Really loud but it makes the math easy. [Corrected from 70.7 originally posted to 7.07]

Now it is fairly clear that any overlapping tones (sines) from instruments in the recording (in different freq bands) can never goose up the the peak voltage demands on the amp or the speaker. That was set at the recording or the mixing board.

The worst case condition is that the music amounts to a square wave. Here the rms value is the peak voltage. It may put demands on the current available from the power supply, but the voltage is not goosed up by simultaneous tones on the recording.

Headroom and dynamics are not affected by how many tones are played except to the extent they add up to a square wave.

- - - -

Here is something to noodle with. Suppose we have 400 channels of TV on the cable. Every band limited signal comes in at 1 volt rms. Does that mean the system has to to pass 400 volts?

Smile,

Gil

[pauln]

Thanks Gil, I suspected that an analysis that took the extreme case of approaching a square wave might clarify the limits of what could happen

In your example you meant that the output is 7.07, not 70.7, right?

[jacksonbart]

Might as well, cause you're gonna be deaf or dead soon enough.

[Don Richard]

Any how PWK told me that you only need 17 db. headroom in amplifier power and that Khorns with a Belle in the middle (like he had) in a large living room only required that much headroom vs. a nominal 1/4 Watts of average power. He was running Crown D-60 and BGW-100 amplifiers.

Those figures were likely for LPs or reel-to-reel tape, which Dave Mallette in a recent post stated a measured dynamic range less than 60dB, IIRC. CDs possess a dynamic range capability of 96dB or so.

Also, if 6dB of EQ is used, power requirements are increased 4 fold. Any loudspeaker used in a room will benefit from the use of EQ. There is an excellent article in this month's TAS on DSP loudspeaker correction that explains how and why.

As for me, I'd rather have it and not need it than need it and not have it. [6]

[WMcD]

Thanks pauln. I've corrected that little matter of being off by a factor of 10!

WMcD

[ClaudeJ1]

Any how PWK told me that you only need 17 db. headroom in amplifier power and that Khorns with a Belle in the middle (like he had) in a large living room only required that much headroom vs. a nominal 1/4 Watts of average power. He was running Crown D-60 and BGW-100 amplifiers.

Those figures were likely for LPs or reel-to-reel tape, which Dave Mallette in a recent post stated a measured dynamic range less than 60dB, IIRC. CDs possess a dynamic range capability of 96dB or so.

Also, if 6dB of EQ is used, power requirements are increased 4 fold. Any loudspeaker used in a room will benefit from the use of EQ. There is an excellent article in this month's TAS on DSP loudspeaker correction that explains how and why.

As for me, I'd rather have it and not need it than need it and not have it.

I agree with your last comment. There's a big difference between 1 Watt and 500 (27 dbWatts to be exact). I'm trying to be realistic but people tend to exagerrate either way sometimes. By design, my MWM stack (see my avatar) exist precisely because I want extreme dynamics, high definition, and low distortion. It's much better to get that with more efficient, all-horn systems, than to try and do it with direct radiator woofer sections, which only gets you to about 98 db/Watt efficiency (typically), whereby the horn section has to be brough down about 10 db to meet with the woofer. I prefer the full 108 db/watt efficiency of my setup (4 db more efficient than my Khorns ever were). Since the woofer section sucks most of the amplifier power, it's always the weakest link in the chain, so you need the horns there the most, yet, because of size and cost, that the first place that people go with Direct Radiators. So the most expensive horn to build is the woofer horn, and the one that takes a huge amount of space (even when folded).

Back in the 70's, my local Klipsch dealer used to express frustration over their "typical" customer who would buy Heresy's (94 db efficiency) with a 300 Watt amplifier instead of LaScalas, which required 1/10th the power and were 30X cleaner with only a 25 Watt receiver. The LaScalas were more dynamic, could play louder, with less distortion, at approsimately the same frequency response, at roughly the same COST, but people were "into watts" back then.

The more things change, the more they stay the same. As for me, I have about 90 Watts per channel on my horn stacks, and 200 Watts per channel on my subwoofers, but I have 6 of them, so about 1,000 Watts total.

It's much better to pursue ACOUSTIC POWER with the efficiency of horns (especially in the woofer section) rather than kilowatts on Direct Radiators.

[Islander]

As for me, I have about 90 Watts per channel on my horn stacks, and 200 Watts per channel on my subwoofers, but I have 6 of them, so about 1,000 Watts total.

So that's about 500Wpc? I'm sure it sounds great, with real authority and no clipping, ever. [Y][H]

[ClaudeJ1]

As for me, I have about 90 Watts per channel on my horn stacks, and 200 Watts per channel on my subwoofers, but I have 6 of them, so about 1,000 Watts total.

So that's about 500Wpc? I'm sure it sounds great, with real authority and no clipping, ever.

My average power runs about -35 to -40 db from full output on the mains. There are 6 channels for the subs, all fed one mono signal, 8 voice coils total. I would use smaller amplifiers on the mains, but they just don't make them in 5.1 receivers. LOL.

[Guest " "]

This reminds me of my DJ days when I used to haul out a pair of SAE P501 amps and operate them in bridge mode so I would have 750 watts continous available per channel. These were real watts that needed 30 AMP lines to feed.

The largest venues I ever played covered areas the size of football feilds and typically had 3000 folks in the audeince. During such times, my led meters would rarely show usage of more than 64 watts.

Later in the game I down sized to smaller 100WPC amps and found no difference in sould and power usage.

I think what we have here is the basic sales issues of what one wants vs what one needs.

[ClaudeJ1]

This reminds me of my DJ days when I used to haul out a pair of SAE P501 amps and operate them in bridge mode so I would have 750 watts continous available per channel. These were real watts that needed 30 AMP lines to feed.

The largest venues I ever played covered areas the size of football feilds and typically had 3000 folks in the audeince. During such times, my led meters would rarely show usage of more than 64 watts.

Later in the game I down sized to smaller 100WPC amps and found no difference in sould and power usage.

I think what we have here is the basic sales issues of what one wants vs what one needs.

I still use my Hafler DH-220's, which were used on a pair of LaScalas for parties, etc. on my third and final DJ system. They could play pretty loud. They were rated at 120 W./channel into 8 ohms, so the approx. dynamic power into the LS's 6 ohm average impedance was probably in the order of 23 dbWatts, added to the 104 db efficiency would yield 127 db peaks at 1 meter. I don't think we ever got close to that loud without complaints. This was in typical halls, etc.

My first system (in 1974, before the disco craze), built at 19 years old consisted of two EV eliminators with SRO woofers and an Altec 511B/808-8a driver in seprate cabs. The other pair was DIY bass reflex cabs 2x2.5x4 feet containing Altec 421-8h woofers, 511B/808-8a drivers, and EV-T35 tweeters. They were driven with a Southwest Tech Products power amp that had the nasty gritty "solid state" sound that drove me to use tubes when I used the system at home. For that, I had a Harman-Kardon Citation Mk III. The big SS amps were 250 W/ch. into 8ohms, but probably did twice that into the parallel load of 4 ohms. The biggest gig I ever did was a college Halloween party for 600, when the driking age in Mich. was 18. Later, those amps were replace with Dynaco 400's, which I wired up from kits. I sold off the entire system except for the amps, which I used for my home system a short while when I got Khorns and a middle LS. I built my own LED power meter and realized that 200 WPC was ridiculous on a Klipsch 2PH3 array.

I sold the Dynacos and went to a recapped Marantz Model 8 (15 dbWatts) that could do 119 db peaks, along with 1/2 of a used 10 dbWatt Sansui SS integrated amp for the mono LaScala in the middle

[ricktate]

Has anyone ever done a blind test using 10watts and 250 watts or 500watts playing music or movies to see if the testers could tell a difference in the amps? Seems to me that this would be good information to have.Rick

[psg]

This one's easy when you use dbW(atts), which is why I'm making my point about this. 5W is 7 dbW, so you would add 7+20=27dbW, or 500 Watts of PEAK amplifier power.

500W for a single frequency. Make that 16 frequencies of equal amplitude and now you're looking at another 20dB for crest factor...

Coming in very last to this discussion, but...

DrWho, why are you adding another 20 dB on top of cliamed requirement for 20 dB headroom? You are up from 20 dB to 40 dB just from musical content from 16 frequencies?

[DrWho]

Because dynamic transients consist of more than one frequency.

Btw,
I'm being pushed into making some red herring arguments to get the
point across...I'm not suggesting that a 110dB speaker is going to need
10,000W for accurate reproduction of most source material. I'm trying
to point out that there is more involved when dealing with music. The
sensitivity calculations are absolutely true when dealing with single
frequency test tones, but the single frequency condition doesn't hold
true for music.

I am saying, however, that even 10W doesn't cut it for even a 110dB speaker.

Btw,
I would love for 10W to be enough because it makes the amplifier design
incredibly easier. Also, the resolution of the system always increases
with decreasing gain in the amplifier (assuming a system with enough
headroom). That said, I don't think you'll see me making any amps with
less than 50W power handling and you'll probably always find me with at
least 100W in my living room (assuming 110dB speakers). But hey, I like
very dynamic music at full (not loud) volumes...

[seti]

I hear what your saying but 8wpc SET sounded incredible on my Belles in my room. I'd say listening sessions 85db - 100d. Kaiser is a SS guy and he was suprised at the bass from the lowly SET. It sounded great with a wonderful detailed soundstage. Are we delusional? Don't answer that. You can show me numbers all day long but if it doesn't jive with the ears something must be amiss. When I read the content of this thread it makes sense but it doesn't match listening experience. Now I have 38wpc PP which is abit more than I need imo but I don't think it sounds better than 8wpc SET. Now I did try to like 10wpc tripath but in the end it had to go after a long evaluation. I guess we'll have to agree to disagree. Trust the ears.

[fenderbender]

Ah, the ears have it...I'm omrdering a Nelson Pass First Watt F5, 25 WPC class A....I must be delusional also [] For that kind of scratch the field is way open for high quality high wattage amps.......Simple circuit, only 2 gain stages, ultra low noise, ultra low distortion....I doubt that I'll ever use 1/4th of the amps power....

[DrWho]

I hear what your saying but 8wpc SET sounded
incredible on my Belles in my room. I'd say listening sessions 85db -
100d. Kaiser is a SS guy and he was suprised at the bass from the lowly
SET. It sounded great with a wonderful detailed soundstage. Are we
delusional? Don't answer that. You can show me numbers all day long but
if it doesn't jive with the ears something must be amiss. When I read
the content of this thread it makes sense but it doesn't match
listening experience. Now I have 38wpc PP which is abit more than I
need imo but I don't think it sounds better than 8wpc SET. Now I did
try to like 10wpc tripath but in the end it had to go after a long
evaluation. I guess we'll have to agree to disagree. Trust the ears.

It just means you're listening to boring source material [][]

I
bet if I picked the source material and we used speakers that actually
played low enough that you would be able to notice your 8W clipping at
about 80dB (even with better sensitivity than your belles). I'm
betting that you might have become accustomed to your ears using the
upper harmonics to fill in the lower notes not being reproduced, which
is going to be a similar exeperience to when your SET amp clips
"softly". The increase in inner detail and all that schnazz is just the
quieter information becoming relatively louder...

I'll open up my place for a shootout...we got an oscilliscope handy so we can measure all the transient clipping
while listening to it happening [] I'm actually dead serious though.
If my laptop HD hadn't bit the dust, I would have just posted the
measurements I took last year. I've got an interesting amp topology on
hand where we can just turn a knob to change the voltage rails...and
thus change the hard clipping point. We can all sit around and turn the
knob until we notice the clipping and then see what power levels and
percentage of clipping we were at. It's an eye opening experience
actually. Reality is so much more fun than theory...

[seti]

I hear what your saying but 8wpc SET sounded
incredible on my Belles in my room. I'd say listening sessions 85db -
100d. Kaiser is a SS guy and he was suprised at the bass from the lowly
SET. It sounded great with a wonderful detailed soundstage. Are we
delusional? Don't answer that. You can show me numbers all day long but
if it doesn't jive with the ears something must be amiss. When I read
the content of this thread it makes sense but it doesn't match
listening experience. Now I have 38wpc PP which is abit more than I
need imo but I don't think it sounds better than 8wpc SET. Now I did
try to like 10wpc tripath but in the end it had to go after a long
evaluation. I guess we'll have to agree to disagree. Trust the ears.

It just means you're listening to boring source material

I
bet if I picked the source material and we used speakers that actually
played low enough that you would be able to notice your 8W clipping at
about 80dB (even with better sensitivity than your belles). I'm
betting that you might have become accustomed to your ears using the
upper harmonics to fill in the lower notes not being reproduced, which
is going to be a similar exeperience to when your SET amp clips
"softly". The increase in inner detail and all that schnazz is just the
quieter information becoming relatively louder...

I'll open up my place for a shootout...we got an oscilliscope handy so we can measure all the transient clipping
while listening to it happening I'm actually dead serious though.
If my laptop HD hadn't bit the dust, I would have just posted the
measurements I took last year. I've got an interesting amp topology on
hand where we can just turn a knob to change the voltage rails...and
thus change the hard clipping point. We can all sit around and turn the
knob until we notice the clipping and then see what power levels and
percentage of clipping we were at. It's an eye opening experience
actually. Reality is so much more fun than theory...

I assure that my source material is as varied as it gets from simple to complex. [:-*] I love music from many genres and cultures. Check out the music and dvd recommendations part of the forums. It is probably the least busy part of this site.

I don't have the funds to stockpile gear the way some do. Unfortunately I sold my SET gear and Wright preamp to try some other gear and tube topologies. Did this mostly out of curiosity thinking I may be missing something. I tried some SS, McIntosh MC30 monoblocks and now 38wpc Onix Melody. While these higher power amps sounded good they didn't have that 3D soundstage and instrument seperation that SET did. When I get another Canary Audio SET system I'd love to have you check it out. However I think you should listen first and measure later. Now I'd love to have my room measured. I'd be willing to pay for that service. That would be super cool. Come down before the next pilgrimage we'll grill steaks and listen to tunes then head to Hope the next day. I'm in Little Rock so it is a short trip to Hope I'll drive.

I know how good SET sounded in my room with my speakers and measurements will likely not convince me that I was some how delusional. It sounded killer. I had musician friends from a couple local bands bringing their music over because they wanted to hear it on my system because they said it extracted detail better than anywhere else they heard it. Now I had heard my SET amps sound bad. This was in Hope 2004 at the goat roper. The room was too big. The preamp was not what I use. The cornwalls just weren't efficient enough. SET really need fully horn loaded speakers and not mearly effecient speakers but this is just my opinion.

If it sounds good and measures bad your measuring the wrong thing or something else is a factor Could there be something else at play with SET that we are missing?

[Coytee]

Kaiser is a SS guy and he was suprised at the bass from the lowly SET. It sounded great with a wonderful detailed soundstage. Are we delusional? Don't answer that

You're not, but Kaiser.... well, you did say to not answer...[]

[Coytee]

Could there be something else at play with SET that we are missing?

OTL sound? [A]

I gotta say... maybe OTL has its flaws and out of my ignorance I'm too dumb to know it but...with that said.

The OTL's that I had (and I've only heard the SE-OTL's) sounded better and more natural than my MC-30's, MC-2102, Wright 2A3's, Jolida (forget model) and numerous solid state amps. I would have happily sold all of them & kept the OTL's if the OTL's had more oomph.

If it weren't for the counfounded 4 stupid watts they had, they'd been a no brainer.

To perhaps try to draw an analogy.... if someone has Heresy's and then steps up to Jubilees, you might have an idea of the huge impact and difference in sound. Pretty straight forward and large difference.

If on the other hand, someone went from say... a K69 driver to the TAD 4002 driver on their Jubilees.... if you were able to hear them back to back (as I once did while at Mikes [Y]) you might notice a distinct and big difference between the two HF drivers. However, in my opinion, you'd have to do a side by side to hear the large part of the difference.... I'd suggest that if I were to walk into Mikes room, I'd not be able to tell right off the bat which one he's hearing. If we did an A/B, then I could. So the differnce between the two HF drivers isn't as grand as the difference between the two speakers themselves.

In my experience, the OTL's & other amps were more like the difference of HF drivers on the K402 instead of being more like the difference in Heresy's to Jubilees.

Anyone make a 500 watt OTL amp?

Oh yeah....drats.... I forgot that I'd need 4 of them suckers.... never mind.

[:S]