Amplifier power and efficient speakers, Is more power better?

doug s. · « **Reply #40 on:** 29 Nov 2009, 05:53 pm »

Quote from: AmpDesigner333 on 29 Nov 2009, 05:45 pm

Another few comments about power...

I seem to be drawn to the sound qualities of low efficiency speakers! Maybe this is because it is easier to design a speaker when efficiency is not so high up on the list of concerns --- when you can waste power on better damping or flattening out the response of the drivers.

As far as amps go, give me a 1000W super low noise+distortion amp over a 10W amp any day. If the power output capability of amps had no effect on the other measurable (and unmeasurable) parameters, than there would be no discussion. Coming as close as possible to recreating a live performance is very important to me, and doing so with 10W, even with 120dB/1W speakers is more or less impossible for most music sources, especially if there is any bass.

what you say is exactly why i tri-amp. i love my single-ended 5wpc tube amp on my 100db-efficient horns. but, they are only doing frequencies >300hz - i have a 30wpc gainclone for the 15" 100db-efficient horn-loaded pro-audio drivers that do 80-300hz, and 150wpc for my 96db-efficient subwoofers that do everything below 80hz.

ymmv,

doug s.

*Scotty* · « **Reply #41 on:** 29 Nov 2009, 06:27 pm »

Here is another link to a pdf doc that explains the problem seen in the waterfall plot that doug posted.http://www.slsloudspeakers.com/media/docs/RibbondriverWhitepaper.pdf What the waterfall plots show are breakup modes that are associated with the horns metal diaphragm. These breakup modes come with the territory and may be a partial explanation for doug's preference for the sound of ribbons. I also prefer the sound of ribbons to horns. I am not a fan of the resonances that are endemic to the horns structure either.
So far I've never met a horn I didn't dislike.
Scotty

doug s. · « **Reply #42 on:** 29 Nov 2009, 07:40 pm »

hey scotty, don't get me wrong - while i like ribbons, i also like horns. aa

doug s.

konut · « **Reply #43 on:** 29 Nov 2009, 08:48 pm »

*Scotty*, are you referring to all horns, or just horns with compression drivers?

*Scotty* · « **Reply #44 on:** 29 Nov 2009, 09:30 pm »

Compression drivers have this problem. The throat of a horn is a high pressure area and I don't know what kind of demands this places on a driver that was not engineered for the application. Until a waterfall plot is taken of the driver/horn combination the extent of any breakup behavior is an unknown quantity. If you are not bothered by what you hear from a horn than this is a non-issue for you.
Scotty

konut · « **Reply #45 on:** 29 Nov 2009, 11:12 pm »

FWIW, I have been bothered by the sound of compression drivers as well. I would not condemn horns though. While its true that there are badly designed horns, cone and dome drivers can be mated to horns to good effect. I have not seen waterfall plots of such combos though, and that would be useful to see. Do you know of any such plots?

doug s. · « **Reply #46 on:** 29 Nov 2009, 11:20 pm »

the horns i use obviously do not utilize compression drivers; i am presently using a decware iteration of the fostex fe206e driver. whatever frequency anomalies they may have are ameliorated by my use of a deqx x-over/dsp processor... a low power tube amp is plenty to drive them with; again, they are crossed over at 300hz...

doug s.

*Scotty* · « **Reply #47 on:** 30 Nov 2009, 01:12 am »

Here is a link to a Decware white paper featuring waterfall graphs and frequency response graphs. http://www.decware.com/paper79.htm This makes for some very interesting reading. I can't find any waterfall plots of domes mated to wave guides.
Scotty

konut · « **Reply #48 on:** 30 Nov 2009, 01:34 am »

It doesn't appear that those plots are taken with the horn attached. Am I wrong?

*Scotty* · « **Reply #49 on:** 30 Nov 2009, 03:22 am »

I don't believe there are any horn applications measured.
Scotty

NewBuyer · « **Reply #50 on:** 30 Nov 2009, 09:52 am »

Quote from: *Scotty* on 29 Nov 2009, 03:17 am

As quoted Benchmark Media's recommendation regarding amplifier power does not make any sense to me. If the you are operating at 75 to 95 percent of the amplifiers rated power on a continuous basis you have only 25 to 15% of the amplifiers remaining reserve power for peaks. It makes more sense to be operating at 75 to 95% on the worst case peaks thereby hopefully minimizing the possibility of clipping...

I think you must be right about this. Benchmark's Elias Gwinn further recommends that ideally, an amp will have an input sensitivity low enough to handle more than the line-level source's max output voltage (e.g. for unbalanced, more than the 2.75v rms, 7.8v peak-to-peak output of the DAC1), which I had understood must thus eliminate potential amp clipping due to overdriving the inputs(?) From there, he also advises the amp should ideally produce a comfortable listening level with your preferred music when the source signal coming into the amp is only minimally attenuated - i.e. as close to 0db source-attenuation as possible - while still allowing a reasonable amount of (but not too much) headroom. This is because the amp's input circuitry will always have its own noise, which also gets amplified along with the source's input signal - thus the stronger (less attenuated) the input signal can be when it arrives right at the amp inputs, while still being within the comfortable listening level (not too loud) from your speakers, the better by definition the resulting signal-to-noise ratio (SNR) of the result. This (if I have correctly understood it) is why he recommends using very-high-quality but lower-powered amps (with the above-stated qualifications regarding input sensitivity etc) whenever possible - that is, in order to achieve the best SNR, as well as dynamic range, in the result.

Yourself and others here, certainly seem to have a much better understanding of these aspects than I do however! So if you wish, I (for one) would be greatly interested in everyone's further thoughts on such advice... is Benchmark's reasoning faulty somehow, or do you agree with it?

Niteshade · « **Reply #51 on:** 30 Nov 2009, 12:02 pm »

I prefer amplifiers with low input sensitivity. They're quieter and allow more travel on a preamp's volume control. They sound better since external and internal influences are minimized.

Dan Banquer · « **Reply #52 on:** 30 Nov 2009, 01:43 pm »

Quote from: JoshK on 29 Nov 2009, 04:21 am

Quote from: konut on 29 Nov 2009, 03:23 am
Were that it was so easy. High efficiency drivers, typically, are less linear that lower efficiency drivers. Not all lower efficiency drivers compress. Its easy to make generalisations, but knowing how to evaluate individual components goes a long way towards putting together a system that will satisfy the end user.

I don't have any desire to get into a debate on the issue, but I am not so sure I buy the less linear statement. If you mean as in less flat FR, well sometimes that is true but many modern HE drivers don't fit that generalization. There are more and more HE drivers meant for other application than ultimate SPL that measure quite flat, as good as many low eff drivers.

"Not all lower efficiency drivers compress." I haven't seen one that doesn't. Even the best of the bunch ScanSpeak revelators compress when asked to produce peaks over 100db. There just can't be enough copper in the motor to not heat up, and if there were, they'd have so much inductance there would be no top end. There is no replacement for 10db of sensitivity.

Well that is my opinion anyway.

Thanks Josh; You are essentially correct that no amount of amplifier power will really help driver compression. Most 90db/spl speakers have their upper limit at 110db/spl, which translates to a 100 watt peak from the amp.
To this day I am amazed at how much misinformation there still is on this subject.
Regards;
Dan Banquer

*Scotty* · « **Reply #53 on:** 30 Nov 2009, 05:19 pm »

I think this limitation goes unnoticed by most people due to the compression present on almost all of our recordings. If our recordings had little to no compression we would be more likely to notice the more subdued and less lifelike quality the music has due to driver compression. This also may be a case where people can't see the forest for the trees. If virtually all piston type mid-range and tweeter drivers exhibit this problem then most people never hear a speaker system that doesn't have power compression. When people don't know that any alternative to this condition exists they accept the flawed speaker system as normal and it becomes the new standard.
That being said I think most people never ask their system to do much that requires them to bump up against this limitation in the course of normal operation.
Scotty

Dan Banquer · « **Reply #54 on:** 30 Nov 2009, 05:31 pm »

Quote from: *Scotty* on 30 Nov 2009, 05:19 pm

I think this limitation goes unnoticed by most people due to the compression present on almost all of our recordings. If our recordings had little to no compression we would be more likely to notice the more subdued and less lifelike quality the music has due to driver compression. This also may be a case where people can't see the forest for the trees. If virtually all piston type mid-range and tweeter drivers exhibit this problem then most people never hear a speaker system that doesn't have power compression. When people don't know that any alternative to this condition exists they accept the flawed speaker system as normal and it becomes the new standard.
That being said I think most people never ask their system to do much that requires them to bump up against this limitation in the course of normal operation.
Scotty

I'll agree; The compression is so heavy handed that any reasonable attempt at fidelity is negated by the source. I'll take it a step further to say I predicted this about 5 years ago when I said that the public is being brainwashed to accept hyper compression as the new norm. My worst fears are being realized.

Regards;
Dan Banquer

Russell Dawkins · « **Reply #55 on:** 30 Nov 2009, 05:41 pm »

Quote from: *Scotty* on 30 Nov 2009, 05:19 pm

I think this limitation goes unnoticed by most people due to the compression present on almost all of our recordings. If our recordings had little to no compression we would be more likely to notice the more subdued and less lifelike quality the music has due to driver compression. This also may be a case where people can't see the forest for the trees. If virtually all piston type mid-range and tweeter drivers exhibit this problem then most people never hear a speaker system that doesn't have power compression. When people don't know that any alternative to this condition exists they accept the flawed speaker system as normal and it becomes the new standard.
That being said I think most people never ask their system to do much that requires them to bump up against this limitation in the course of normal operation.
Scotty

I disagree. I think the limitation does not go unnoticed with those who have a highly dynamic combination of amp and speakers. The advantages of this set up are obvious with any recording, including over-compressed ones, because it isn't all about instantaneous dynamics; part of the advantage is about simple loudness-without-distortion capability.

It goes unnoticed because of the point you made that I highlighted.

NewBuyer · « **Reply #56 on:** 2 Dec 2009, 04:55 am »

Quote from: Niteshade on 30 Nov 2009, 12:02 pm

I prefer amplifiers with low input sensitivity. They're quieter and allow more travel on a preamp's volume control. They sound better since external and internal influences are minimized.

Blair, I was just now looking at the very nice equipment you have on your site.

Do you have any lower-powered amps that would fit Elias Gwinn's advice (please see my above post) as being a good match with their DAC1, i.e. having an (unbalanced) input sensitivity low enough to handle more than the 2.75v rms, 7.8v peak-to-peak output of the DAC1?

Also please, out of curiosity: How is input sensitivity actually created in an amp - is it simply a particularly chosen resistor behind its inputs (i.e. a simple voltage-divider), or is input sensitivity a more complicated aspect than this?

AmpDesigner333 · « **Reply #57 on:** 2 Dec 2009, 01:39 pm »

About driver compression... More drivers equals less compression. There's no cheating physics, and depending on the music, you may need to move lots of air to imitate reality. There's no substitute for headroom. 2 more cents...

rollo · « **Reply #58 on:** 3 Dec 2009, 05:36 pm »

I'm using speakers with[ 9 ]5" mids and [24] 1" dome tweeters per side. Rated at 94db. Using a 22W SET. Now when I switch to a 250W triode amp the music is effortless, fuller, no compression detected and a more powerfull midbass. Why?

charles

Dan Banquer · « **Reply #59 on:** 3 Dec 2009, 05:42 pm »

Quote from: rollo on 3 Dec 2009, 05:36 pm

I'm using speakers with[ 9 ]5" mids and [24] 1" dome tweeters per side. Rated at 94db. Using a 22W SET. Now when I switch to a 250W triode amp the music is effortless, fuller, no compression detected and a more powerfull midbass. Why?

charles

Measue your 22 watt unit for power to confirm whether it's doing it's rated power or not. You should also take a look at it's output imedance vs. frequency response, and if the unit has no negative feedback check it's output impedance connected to the loudspeaker from 20Hz to 20kHz.
Regards;
d.b.