Axiom Home Page Forums General Discussion Technical Questions hk 3480 modification: science or wishful hearing?

Just a guess, but perhaps the minimum wattage spec refers to a recommended minimum rated power for the receiver/amp driving the speakers?

That's what JohnK said above. And I said 10W for the M80s would be a reasonable minimum for most material if you listen to them at 1/8 watt on average.

>>With regard to cone control and precision of movement, I am curious how RickSean confirmed that a higher power amp provides an improvement in this area.

I think this is the damping factor argument. Big-ass amplifiers tend to have lower effective resistance in the output stages, which IIRC should result in slightly tighter control of the cone movement. Same idea as braking in a full hybrid car, where placing a heavy load (battery charger) on the motor/generator makes it act as a brake.

Either Alan or Ian mentioned that the damping factor argument had been debunked recently although I didn't have time to get the details. Debunked or not, my understanding is that there is a point of diminishing returns, so that the audible difference between a "pretty good" amplifier and a "really good big-ass amp" is negligible.

A not-so-good amp with high output impedence (low damping factor) could presumably result in looser bass, in the same way as having speaker wires which are MUCH too thin could introduce enough resistance to affect the sound.

Just a note to Randy from another thread -- the "Big-ass Amplifier Club" is for people with high power, high quality amplifiers. The "Big Ass Amplifier Club" is something which you may want to avoid.

Probably re-debunked recently, John. Gene published this study in Audioholics by speaker designer Dick Pierce a few years ago and more recently in Audioholics Mark Sanfilipo covered the point. It appears that amplifier damping has very little to do with "controlling" the speaker, almost nothing until the low single digits that some tube designs exhibit. Anything much beyond the start of the double digits seems to be mostly hot air and even inexpensive solid state designs run around 50 or more.

Well, I have to admit this has been an interesting side discussion. I did end up by writing to Axiom Audio, out of curiosity, and a very nice gentleman, JC, did write me back. I would like to post excerpts of his response to my email. I would still argue that the methods used in Mojo’s experiment to prove a Sony Boombox is as good as Denon are highly flawed. Again, I am not a fan of Denon equipment (particularly newer pieces, as I feel the older equipment was actually better sounding). Below are excerpts of JC answers to my questions with my own comments.


In response to my question as to the efficiency of the M80s being able to play at 91db at 1 meter with 1 watt of power and how the woofers would be powered, JC first explained that the speakers would technically play at 91db at 1 meter away with 1 watt, but this was not a constant, unchanging 1 watt of power for the entire frequency range, as was inferred by Mojo. JC stated: “We tend to talk of speakers and amplifiers in static load terms but this is not how they work. A speaker will have (or at least should have) a constant and equal output at each frequency at each wattage level of input. This being said a speaker load is not static in that it changes with frequency. So when we are talking one watt that will be one watt at one frequency (generally 1 kHz), or if broadband then 1 watt at the lowest point on the impedance curve. So the amplifier is not actually putting out one watt at all frequencies. Generally it will be the lower frequencies that consume the most power (resonance point exce!
pted) so hence the concept you are pointing out that the bass driver will be harder to drive than the tweeter.” This is what I had thought previously, as most people know that the bass frequencies are what consumes the vast amount of power.

JC further comments on something which I had wondered about as well, considering how Mojo says he listens to movies at “a few watts.” JC states: “To add another twist to this is the dynamics of music and movies. There is no such thing as playing music or movies at 1 watt; this number would really just be some sort of average power required. Given, lets say a 12 db dynamic peak occurred from your average of 1 watt this peak would require 16 watts of power. Now if you were sitting 26 feet back from a pair of speakers that had an anechoic output of 91 db per watt at 1 meter. You would add say 3 db for the room gain and another 3 db for the second speaker. Now you have 97 dB of output at one watt per channel and one meter back. At 26 feet back you would have 79 dB due to the inverse square law. So if you wanted to have your 91 dB at 26 feet back you would need to put in an average of 16 watts to achieve this. Now your 12 dB peak would require 256 watts to reproduce. This is why so much power is required, especially in a large space.” This is also about what I had already knew. If Mojo is listening to movies at “a few watts,” they had better be very low in volume and be lacking in dynamics, in a rather small room and in close proximity to the speakers. Dynamic range itself would take more than “a few watts.”

In response to my question of whether a person could play the M80s at adequate enough fidelity to conduct a test between two receivers at only a quarter of a watt, JC’s reply was: “That is partially true and it would applied only under certain conditions: an exceedingly small listening room space – a very low volume level – a source material which contain very limited dynamics.” This is actually about what I suspected. Also, by Mojo not testing what is going on below 40 hz and not running a subwoofer also puts in jeopardy the validity of his “test.” To be able to test out two pieces of equipment, you not only need to compare dynamics, but also most people would want to compare how clean or tight it runs the bass, especially low bass (aka below 40hz). Some receivers may sound fine on the upper frequencies and possibly even midrange, but will tend to sound either “boomy” or light or muddy in the bass, and to be able to tell this, you need to be able to hear it. Mojo can make all the charts he wants, but I think he is missing the point of what he is trying to do in the first place. This isn’t a contest as to “what is the least amount of watts I can get away with?” The question really is about comparing low cost pieces of equipment to the more expensive pieces. I have done the same a number of times and the high-end piece does not necessarily win out. If he wants to compare a low priced piece and compare it to a more expensive piece and say that there is no sound difference, he should find something that puts out a low, but decent amount of wattage, instead of putting out wattage at below 3 watts. I do not think it is a very fair way how to compare two receivers if you are merely playing them at one fourth of a watt, with rather low volume and lacking dynamic range, which requires higher wattage to be reproduced correctly. This tells you nothing about the character of the receivers, how they react to dynamics, and the clarity of their sound (especially how they deal with low bass).

As to the current discussion of minimum watts rating JC responded: “Again, the 10 watt rating is for a very small room but also for people running tube amps. Tube amps have a very soft sort of analog clipping which means you can get away with lower power and not have the harsh attributes of output device clipping.”

I personally, always run my speakers at a much higher wattage than the minimum and, as stated earlier, have found that it helps performance. I can tell my speakers are more under control with more power available, proven by listening (a foreign concept to some people around here it seems). When I added a dedicated line (increasing power capacity available and less interference from other circuits), and when I inserted my modified HK 3485 receiver into the system (150 watts for 4ohm, thereby, allowing my already very efficient speakers and subwoofers to have more power available), I noticed in both occasions tighter bass, clearer highs, which would be accounted for by the amplifier being able to control the cone movement to a greater degree. This is what damping factor describes; the ability of a receiver to control the speakers cone movement. A very interesting online article speaking of this and how you really do need more watts to reproduce realistic sound is found below. It was actually posted by another Axiom Audio gentleman.

http://forum.ecoustics.com/bbs/messages/34579/109138.html

In in it he talks about the relationship between SPL, wattage and live sound and attempts to reproduce live sound. Near the end of his rather lengthy post he states: “From all this you can see the huge power requirements inherent in reproducing real-life acoustic sound levels in average or big rooms…. It's the distortion that makes it sound "loud" in a domestic setting…. The lesson in all this is that you can never have too much power, and that big amplifiers rarely damage speakers. Little amplifiers driven into clipping burn out speakers. In the scheme of high fidelity, that last barrier to realism is having enough power and being able to approximate real-life loudness levels.”

by Alan Lofft, Axiom Audio

The article was very interesting and I think would be a good read for anyone. I have personally found that by having a clean, higher wattage receiver, that my “air,” overall definition and stage have improved. The audio is not audibly “louder” by a great degree. In fact, harshness as noticeably decreased.

RickSean

Now that's the kind of post that elevates a discussion from "roll your eyes while reading" to "hey, this is actually getting interesting and educational." Thanks for contributing and not running away screaming when many of us weren't taking you seriously.

For the most part, I have to agree with what you (and JC) say. It's not the average power consumption that's important, but the peaks. That's where the true tests of equipment are. Randy (sirquack) drove this point home very firmly when he was unable to get his new Emotiva amp to perform up to snuff in his "underground cavern" of a basement.

I must point out a flaw in some of your reasoning, however.

Quote:

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Also, by Mojo not testing what is going on below 40 hz and not running a subwoofer also puts in jeopardy the validity of his “test.” To be able to test out two pieces of equipment, you not only need to compare dynamics, but also most people would want to compare how clean or tight it runs the bass, especially low bass (aka below 40hz). Some receivers may sound fine on the upper frequencies and possibly even midrange, but will tend to sound either “boomy” or light or muddy in the bass, and to be able to tell this, you need to be able to hear it.

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Most subwoofers have onboard amps. When you enable the sub out on a receiver, it peels off the audio signal below the crossover point and sends it out the line level sub output -- unamplified. This results in a lighter, more easier to drive load going to the high level speaker outputs to which the rest of the speakers are connected.

I believe he got better results by not including the subwoofer in the test.

From Ian

"Over the years I have always found the sound differences between amplifiers to be subtle when compared to the differences found in speakers. Hence if budget is a concern you are probably better to cut a little deeper on the amp side. The main reason for this is that amplifiers (with the exception of some bizarre designs out there) do not colour the tonal balance of the performance nor have any bearing on the off axis response. This does not mean that all amplifiers sound the same but that different factors come into play. Without question the big one is the amount of power available to play dynamic peaks. Wid was commenting earlier about the statement that at normal listening levels you do not need more than a watt or two and I agree with him that this statement is, in practical terms, false; though granted in mathematical terms under certain conditions it can be proved true. The power required to bring home a great performance can get pretty large if you want even just moderate listening levels in a large space without any clipping in the dynamics. The reality is that when most people want to crank up their system they rarely achieve the volume level they truly want; instead they go to the level of clipping distortion in the dynamics that they can put up with (which sounds painfully harsh and loud even if it isn’t)."

Thanks Peter, Peter, Peter, Peter, oh sorry I was down in my cavern and it echos a lot, no wonder I have treatments.

I'm starting to believe that it is not ALL about power (watts). I'm starting to believe Klaus from Odyssey Audio more and more about the importance of Capacitance reserve. I can really tell now that when listening to music with lots of dynamics at higher levels my new Odyssey Monoblocks just don't run out of gas or show any signs of stress.

Oh yeah, they have a great damping factor as well.

ps: Rick, we all know that guy Alan very well.