Questions About Ascend Speaker Measurements

[N Boros]

I was looking at the Specifications page for the Sierra 2 speakers and it mentions that the maximum continuous power is 150 Watts and the maximum short term peak power is 300 Watts. I understand what this is saying but I am a little confused about the "Unclipped peaks" that are mentioned in the asterisk.

I'm not sure if this is a warning that they can only accept this amount of power safely if it is clean in terms of THD less than say 0.01% for the 150 Watts delivered continuously and say less than 1% THD for short term peaks of 300 Watts. Or is this is saying that in the case that you are cleanly delivering 150 Watts continuously and up to 300 Watts in short term peaks, that the speaker is playing cleanly, in other words with low THD + noise.

So, I guess I will ask my question. Say that I have an amplifier that can deliver 150 W continuously with THD less than 0.01% and short term peaks of 300 W at less than 1% THD. Will the Sierra 2s produce an output that has low THD + noise (in the low single digits) when it is pushed close to these limits?

[curtis]

I think it just means they won't blow up with that kind of power.

[davef]

I was looking at the Specifications page for the Sierra 2 speakers and it mentions that the maximum continuous power is 150 Watts and the maximum short term peak power is 300 Watts. I understand what this is saying but I am a little confused about the "Unclipped peaks" that are mentioned in the asterisk.

I'm not sure if this is a warning that they can only accept this amount of power safely if it is clean in terms of THD less than say 0.01% for the 150 Watts delivered continuously and say less than 1% THD for short term peaks of 300 Watts. Or is this is saying that in the case that you are cleanly delivering 150 Watts continuously and up to 300 Watts in short term peaks, that the speaker is playing cleanly, in other words with low THD + noise.

So, I guess I will ask my question. Say that I have an amplifier that can deliver 150 W continuously with THD less than 0.01% and short term peaks of 300 W at less than 1% THD. Will the Sierra 2s produce an output that has low THD + noise (in the low single digits) when it is pushed close to these limits?

I am sorry but I don't follow your question. The power spec for the Sierra-2 has nothing to do with amplifier THD. If an amplifier clips it produces a distorted square wave which even at low power can destroy speaker components. Clipping distortion is a combination of many different types of distortion, it also produces odd order harmonics that are not part of the source material -- these harmonics can cause components to quickly over heat. Amplifier specifications really do not give any insight as to how the amplifier will behave when it clips, or when it will start clipping as there are far too many variables involved.

[N Boros]

I am sorry but I don't follow your question. The power spec for the Sierra-2 has nothing to do with amplifier THD. If an amplifier clips it produces a distorted square wave which even at low power can destroy speaker components. Clipping distortion is a combination of many different types of distortion, it also produces odd order harmonics that are not part of the source material -- these harmonics can cause components to quickly over heat. Amplifier specifications really do not give any insight as to how the amplifier will behave when it clips, or when it will start clipping as there are far too many variables involved.

Okay so the "unclipped peaks" is not referring to the amplifier. So it must be referring to the output of the speaker when one is driving it near the limits of 150 W continuously and with 300 W peaks. Just doing some rough calculations at my seating distance of 10 feet away, to hit 105 dB peaks for reference volume, the Sierra 2s need about 300 W.

In the Sierra Sat thread you mention that the Sats can hit about 99 dB peaks at about 10 feet away without any compression to your ears. So will the Sierra 2s be able to hit 105 dB peaks cleanly (without high distortion or compression)? It this what you are referring to my "unclipped peaks"?

[sludgeogre]

Okay so the "unclipped peaks" is not referring to the amplifier. So it must be referring to the output of the speaker when one is driving it near the limits of 150 W continuously and with 300 W peaks. Just doing some rough calculations at my seating distance of 10 feet away, to hit 105 dB peaks for reference volume, the Sierra 2s need about 300 W.

In the Sierra Sat thread you mention that the Sats can hit about 99 dB peaks at about 10 feet away without any compression to your ears. So will the Sierra 2s be able to hit 105 dB peaks cleanly (without high distortion or compression)? It this what you are referring to my "unclipped peaks"?

Unclipped peaks just refers to music that has big, loud passages which do not clip, IE they don't go above 0 dB. In these loudness wars between label companies there have been some releases that contain clipped signals and this can wreak havoc on a good system. I very rarely run into it with music, though.

105 dB seems pretty intense, though. I don't know why you want to run your speakers that loud, but I don't see why the Sierra 2 wouldn't be able to handle it. I play my Sierra towers pretty loud and they have not lost composure on me even once. I power them with an Emotiva XPA-5 Gen 2 so they get a decent amount of juice, 300 watts into 2 channels or 200 into 5. I can tell you that I have never, ever given them the full juice they can take. It'll melt your ears off your head with how loud it'll get.

[theophile]

NB,

I apologize if my comments below are already understood, but thought I'd put this out there for members that may still have some questions relating to amplifier power needs versus transducer ratings.

In the real world, audio music\soundtrack playback can\does generate up to +10db of dynamic headroom peaks (http://www.audioholics.com/room-acoustics/the-decibel-db). In the case of the Sierra 2's, if your playback levels are averaging 87db with 1 watt of power, then you will need 10 watts of clean power to safely cover the musical peaks (logarithmic facts state 10db=10X power). Thus you need an amp that has a "clean 10 watts of power output"! In this scenario, the dynamic musical waveforms are smooth and unclipped with S2 playback that has natural and clean dynamics as per the genre of music.

Continuing with the Sierra 2's (in the real world), their maximum continuous unclipped power rating of 150 watts means that your sustained maximum S2 playback levels will only handle "15 continuous watts" of amplifier power, which still yields 150 watts of unclipped, clean dynamic musical peaks! At this point if your power amp has a clean continuous power output per channel of 150 watts, the theoretical musical output of the S2's would be 98.5 db, with 108.5 db of CLEAN, UNDISTORTED Musical Peaks...all is good!!!

Dave also rates the S2's as being able to handle maximum short term peak power of 300 watts. Assuming your amp is rated for continuous clean 300 watts per channel, then the S2's could (during short duration playback levels), give clean dynamic peaks of 111.5db!! :eek:

As Dave has clearly stated, amplifiers pushed past their clean power ratings, [such as when attempting to cover the +10db of headroom to cover real-world musical peaks], DO go into extreme waveform clipping distortions, generating tremendous heat in the driver voice coils that quickly can destroy the speakers. I've seen it happen in tweeters and woofers...Not Pretty!

If music playback starts to sound harsh, strained or fatiguing, probably a good indication that the amp is being driven into dynamic peak distortions...turn it down or you may end up needing to replace drivers!

Again "in-the-real-world", driving speakers with low powered amps can quickly create a Much Greater Risk of damaging (blowing) speaker drivers due to entering into clipping amplifier waveforms while attempting louder playback levels. Matching, or slightly exceeding the max clean power rating of the amp to the speaker rating goes a long way to enjoying your HT or Stereo for a much longer time. Either way, still be cautious of maintaining "Clean Amplifier Peak" playback levels!

Hope this was clear and possibly helpful,

Ted

[sludgeogre]

Extremely well written post there, theophile! Thanks for explaining it so well. Much better job than I could ever do.

You have to agree with using an amp that covers every situation with plenty of power. Many people end up damaging their speakers simply by driving them too hard with crappy receivers.

[theophile]

Extremely well written post there, theophile! Thanks for explaining it so well. Much better job than I could ever do.

You have to agree with using an amp that covers every situation with plenty of power. Many people end up damaging their speakers simply by driving them too hard with crappy receivers.

Thanks Alex!

Plenty of "Clean Power" is almost Never a problem. Over driving an amplifier, usually because it is under-powered for the intended musical use (being a receiver or a stand-alone high quality power amp=no difference) is suspect 99% of the time with damaged drivers! Low clean power (<50 watts)...be very cautious of volume playback. High clean power (>100watts), Enjoy the Music!!

Ted

[sludgeogre]

Thanks Alex!

Plenty of "Clean Power" is almost Never a problem. Over driving an amplifier, usually because it is under-powered for the intended musical use (being a receiver or a stand-alone high quality power amp=no difference) is suspect 99% of the time with damaged drivers! Low clean power (<50 watts)...be very cautious of volume playback. High clean power (>100watts), Enjoy the Music!!

Ted

Absolutely, clean power is the key. Indeed it doesn't matter if it's separates or a receiver, it just seems like those cheap class D sections in low-tier receivers seem to be the culprit most of the time. I know the only time I've ever blown a speaker was with one of those. I could also see people doing it with those awful little Tripath amps that you can get for like 30 bucks, wow do those sound distorted when you push them. Personally I've been going back and forth on whether I want to upgrade to an Emotiva XMC-1 and another amp for Atmos or just go with an Anthem receiver... decisions, decisions... Won't be for a couple years anyway.

[N Boros]

NB,

I apologize if my comments below are already understood, but thought I'd put this out there for members that may still have some questions relating to amplifier power needs versus transducer ratings.

In the real world, audio music\soundtrack playback can\does generate up to +10db of dynamic headroom peaks (http://www.audioholics.com/room-acoustics/the-decibel-db). In the case of the Sierra 2's, if your playback levels are averaging 87db with 1 watt of power, then you will need 10 watts of clean power to safely cover the musical peaks (logarithmic facts state 10db=10X power). Thus you need an amp that has a "clean 10 watts of power output"! In this scenario, the dynamic musical waveforms are smooth and unclipped with S2 playback that has natural and clean dynamics as per the genre of music.

Continuing with the Sierra 2's (in the real world), their maximum continuous unclipped power rating of 150 watts means that your sustained maximum S2 playback levels will only handle "15 continuous watts" of amplifier power, which still yields 150 watts of unclipped, clean dynamic musical peaks! At this point if your power amp has a clean continuous power output per channel of 150 watts, the theoretical musical output of the S2's would be 98.5 db, with 108.5 db of CLEAN, UNDISTORTED Musical Peaks...all is good!!!

Dave also rates the S2's as being able to handle maximum short term peak power of 300 watts. Assuming your amp is rated for continuous clean 300 watts per channel, then the S2's could (during short duration playback levels), give clean dynamic peaks of 111.5db!! :eek:

As Dave has clearly stated, amplifiers pushed past their clean power ratings, [such as when attempting to cover the +10db of headroom to cover real-world musical peaks], DO go into extreme waveform clipping distortions, generating tremendous heat in the driver voice coils that quickly can destroy the speakers. I've seen it happen in tweeters and woofers...Not Pretty!

If music playback starts to sound harsh, strained or fatiguing, probably a good indication that the amp is being driven into dynamic peak distortions...turn it down or you may end up needing to replace drivers!

Again "in-the-real-world", driving speakers with low powered amps can quickly create a Much Greater Risk of damaging (blowing) speaker drivers due to entering into clipping amplifier waveforms while attempting louder playback levels. Matching, or slightly exceeding the max clean power rating of the amp to the speaker rating goes a long way to enjoying your HT or Stereo for a much longer time. Either way, still be cautious of maintaining "Clean Amplifier Peak" playback levels!

Hope this was clear and possibly helpful,

Ted

Hi Ted,

Thanks for this explaination. This is helpful to me and others.

I did want to make just one small correction and expand on this a bit. To add 10dB of output we need to multiple the amplifer power by 10. That is correct. Also, if we want to vary the distance from the sensitivity spec, where it was measured at 1 meter away from the speaker we need to subtract about 3dB (in a room) for every doubling of the distance. Or to get a 3 dB gain we need to double the power. With these three things in mind we can take the sensitivity and figure out how loud the speakers can get in our seat.

One small correction on the sensitivity though. Since this is a nominal 6 ohm speaker it is actually 1.33 Watts to produce 87 dB at 1 m away from the speaker.

Double the distance: 1.33 W gives 84 dB at 2m
10 times power: 13.3 W gives 94 dB at 2m
10 times power: 133 W gives 104 dB at 2m
Double the distance: 266 W gives 104 dB at 4m

My main seating area is only about 3 meters away from the speakers, but I will have a second row at about 5 meters away. My main concern is to be able to hit reference volume for movies, which is 85 dB average and up to 105 dB peaks. That is the loudest I would ever crank up an action movie and this would be a rare occurrence. But, I just want to make sure that I can cleanly hit it and maybe set the volume limiter in the receiver or processor at this level. So if I calculated this correctly I guess that this is not problem. I just need to get an amplifier that can cleanly put out 250 W to 300 W peaks.

Back to my original question. If our amplifier can cleanly put out 300 W peaks, is the output from the speaker still clean at those 300 Watt peaks (Note that a 105 dB peak will be very close to needing 300 Watts at 4m away.)? Or would we be hearing distortion or compression when the speaker is driven with that amount of power?

[theophile]

...So if I calculated this correctly I guess that this is not problem. I just need to get an amplifier that can cleanly put out 250 W to 300 W peaks.

Back to my original question. If our amplifier can cleanly put out 300 W peaks, is the output from the speaker still clean at those 300 Watt peaks (Note that a 105 dB peak will be very close to needing 300 Watts at 4m away.)? Or would we be hearing distortion or compression when the speaker is driven with that amount of power?

NB,

You are in the right church, right pew!!

A good amp capable of clean 300 watts\channel (from 6 to 8 ohms output) will meet your peak HT audio realism goals! I see no problem with the S2's (barring any severe room nulls or response voids) maintaining their response integrity with 105db musical peaks. On the other hand, Your Ears may start distorting (becoming fatigued\ringing) due to excessive high noise (music, sound, volume) with long term listening (105db safe "continuous" unprotected sound exposure is under 15 minutes-as per OSHA)?! :eek:

Ted

[N Boros]

Ted,

I do not at all plan to listen to 105dB on average. I am only talking about peaks at a fraction of a second. Per OSHA 85 dB on average with 105 dB peaks is supposedly safe for up to 8 hours per day. The recording engineers for movies that aren't deaf in their older age give some weight this these figures. My plan to make sure that I can cleanly play at 85 dB on average with 105 dB peaks because that is the absolute loudest I would ever listen to a movie. Usually I might be at -15 or -20 dB under 85 dB average volume, but every now and then we might crank things up and I want to be sure that my equipment is safe in doing so.

I'm hoping that Dave might be able to let me know that if we push the Sierra 2 close to the 300 W for peaks that if the peaks are clean in terms of no distortion or compression going on there. I'm still trying to understand what "unclipped peaks" mean.

[davef]

One small correction on the sensitivity though. Since this is a nominal 6 ohm speaker it is actually 1.33 Watts to produce 87 dB at 1 m away from the speaker.

Incorrect, minimum impedance is not nominal impedance. The minimum impedance of the Sierra-2 is ~6.3 - ~6.4 ohms. This meets IEC impedance specifications of being a nominal 8 ohm impedance speaker.

It is a bit more complicated than this as one must / should also look at the speaker's reactance at its minimum impedances and in the case of the Sierra-2, reactance is mild - making it an exceptionally easy nominal 8 ohm load.


Back to my original question. If our amplifier can cleanly put out 300 W peaks, is the output from the speaker still clean at those 300 Watt peaks (Note that a 105 dB peak will be very close to needing 300 Watts at 4m away.)? Or would we be hearing distortion or compression when the speaker is driven with that amount of power?

Nick, the problem here is that you are asking for a definitive answer to a question that simply can not be definitively answered. It is basically the same as asking if the car I am buying, which is rated at 30 mpg highway, will I also get 30 mpg when I am driving it?

There is nearly an impossible number of variables here.

First off, amplifier power ratings are determined using purely resistive loads. Speakers present a reactive load to an amplifier - and how that amplifier will react to the complex impedance of a specific is unknown, as every model speaker presents its own unique load. An amplifier might be "clean" at 300 watts into a static 8 ohm load (I am not sure what your definition of "clean" is) - but this same amp may very well start to clip under a reactive load, even at well under rated power - or produce distortion that the speaker in question does not handle well.

As far as hearing distortion or compression, it is entirely unknown at what percentage of distortion is typically audible with human hearing. There are also many different types of distortions - some more audible than others.

I believe, theoretically, what you are asking is if at an amplifier's peak power delivery of 300 watts, how different will the output of a speaker be compared to the source?

Assuming the source is bandwidth limited pink noise (limited to the real world capabilities of the speaker), and the speaker is a purely resistive 8 ohm load, and the amp is rated at 300 watts peak at 8 ohms, and the speaker is rated at 300 watts peak (and a peak is defined by a typical 1.414 crest factor over a max of 5ms) - the speaker should "cleanly" reproduce this peak.

But what is defined as clean? Also, music and home theater sources are not bandwidth limited pink noise. Hit any ported speaker with a frequency below port tune, and the power handling of that speaker will drop considerably (as will the reactance presented to the amplifier). The converse is also true -- high frequency switching noise of class D amps is typically not a problem for any dome tweeter as they can't reproduce it and it is just dissipated as heat in the voice coil - but true ribbon tweeters are different and will try to reproduce it, and this can be problematic as well.

I hope you see my point. The only way to answer your question is to actually match your amp with the speakers in question, combined with an appropriate source signal and test - or simply just listen for yourself and if you hear distortion or mechanical distress, turn the volume down.

We have had no issues reaching 105dB peaks with a pair Sierra-2 crossed to a sub at 80Hz at ~11ft with a well designed 150 watt class A/B amplifier.

And just to add to the complexity of this, Ted's post (which is very good) does not factor in variances in room / boundary gain. We are overly conservative with our in-room sensitivity specification - real world scenarios would typically add 3-5dB to our anechoic sensitivity spec - and this will vary considerably regarding different placements within that room.

Hope this makes sense

[sludgeogre]

This has quickly turned into a great thread! Lots of information here.

I have to say that with 300 watts behind my towers, they will absolutely terrify you with how crazy loud they can get. When I first got them and was getting used to them, I kept finding scenes in movies with clipping and I could hear it. I thought something was wrong with the speakers or setup at first, but it only happened on certain scenes, so it turned out to be the movie tracks themselves and not the speakers. Play that same movie on a less resolving speaker and you don't hear any clipping at all.

The Sierras will effortlessly reproduce whatever you throw at them, be it clean or dirty or anything in between, so you have to be careful with confusing things that you're hearing with equipment specs. I thought I was providing a clean signal all the time, but it turned out that Hollywood isn't always as careful as they should be. Just keep this in mind when you start playing your music really loud and you hear things that you don't think you should be. If your gear is operating as it should and is capable of doing what you're asking, the problems you hear are from the source material and you're just hearing it the way it actually exists for the first time.

[N Boros]

Dave and Ted,

Thanks for the replies! This has been very helpful in understanding the limitations of measurements and specs in some cases. The fact that I didn't look as carefully as I should have and thought that the minimal impedance was the nominal impedance is actually helpful though, after thinking about it a bit. These frequencies with the lowest impedance present the most difficult challenge to the amplifier. So if I can just about hit the reference volume peaks at my seat with that impedance, then it is likely that it should be no problem for the rest of the frequencies.

Your gas mileage example gives a great analogy to help understand what is going on. It is funny. I drive an older Honda Civic that according to the EPA testing standards should get 30 mpg for city and 40 mpg for highway. At my previous house I had about a 50/50 mixture of city and highway driving and usually I would get around 35 mpg. Now, I have a very very short commute to work and just about everywhere else I drive to is a similar short distance. Now I am only getting between 25 and 30 mpg. At first I was upset and thinking something might be wrong with my car. But, after thinking about it a bit I realized that I wasn't driving under the conditions that the car was driven in where the EPA tested it under. This is exactly what some of the measurements for the Sierra 2 mean. They can be a good for guidelines to get us in the ballpark of where we want to be. But, likely they are not going to perfectly tell us how the speaker is going to perform in my particular room. There are simply too many variables to know for sure. It does sound promising that by the theoretical calculations I can hit the peaks that I would like and from your experience in your rooms you have hit 105 dB peaks with only a good 150 Watt amp. So it is likely that I should at least get close to being able to do so as well. Thanks again!