I'd like to address Rick and Sean's last post. Although I agree with the spirit of most points, some details require clarification.

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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.



The purpose of my original "test" wasn't to compare the Denon against the Sony. Rather, it was to compare the two at the same power level. To that end, I'd say my "test" was designed fairly and nothing that has been posted to date proves otherwise as I will argue below.

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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.



I am not sure what the above is getting at but from the test I conducted, it was obvious that the Sony and Denon could equally provide the power demanded by the M80s. By the way, bass frequencies do not consume the vast amount of power. They do however demand higher current than higher frequencies. Power is not a function of the frequency; current and voltage are however. The source material could demand 50 watts at any frequency.

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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).



I agree with the spirit of the above. At no time would I ever encourage anyone to purchase an amplifier of a half watt for music and a few watts for movies. These are of course nominal values and dynamics require much more power than this. And this leads to an omission on my part and I do apologize for any confusion that I may have caused newbies. I should have pointed out that these power levels are nominal values.

As I have posted elsewhere on these boards, if you listen at a nominal level of 1/4 watt to music, a 10W amplifier is adequate giving you about 16dB of headroom. And for movies, if you listen at a nominal level of 2 watts, a 64W amplifier should be fine with about 15dB of headroom. So those of us that buy 90W/channel amps should be quite satisfied. And for those with Denon amps, you can be quite sure that you can hit peaks of twice rated continuous power before square-waving takes place. And for those of you that have been reading my posts, you know that these are the typical power levels in my 4,000 cubic foot home theater and they give rise to nominal sound pressure levels of 85-90 dBC. 4,000 cubic feet is not an "exceedingly small listening room".

As to the argument about low bass, I think pmbuko summed it up. A sub-woofer would have placed less of a load on the amps.

I just want to point out again that I was not comparing the Denon against the Sony in an absolute manner. It was a relative test at the same power levels that I typically experience in my home theater while listening to music. If it was an absolute test, the Denon would win hands down.

Rick & Sean stated that they like to run their speakers at a much higher wattage than the minimum. I assume that they are referring to nominal power levels. If I was to run my M80s at a nominal level of 10 watts (their minimum), I would go deaf in my room. I already enjoy nominal sound pressure levels of 85dB to 90dB with nominal levels of a quarter to a half watt.

So my primitive but nonetheless effective test still shows that two amplifiers, when operated within their spec, sound the same. But we're still back to square one on the effect of after-market component tweaks on sound quality. Rick and Sean, both of you obviously have considerable passion for this subject and are in a perfect position to convince us using a combination of technical tests using measuring instruments as well as properly structured A/B listening tests. Imagine the positive impact that irrefutable proof would have on your business. I and others on this site are anxious to see the results.

BTW, I don't know why some text in the quoted sections is garbled.