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#288970 - 01/27/10 11:03 PM Re: Distortion [Re: JohnK]
htnut
Unregistered


 Originally Posted By: JohnK
Nut, yes all receivers do put out their rated power; this is governed by FTC regulations, and failure to do so would be a violation of the law.

Certainly one who "wishes to listen" at 115dB would need on the order of 1000 watts for that with speakers of typical sensitivity(such as the Axioms). However that listening level would be tantamount to aural suicide.


Thanks JohnK, I didn't realize FTC regulated receivers. Do they stipulate the conditions of the power output rating?

I see one channel, two channel, five channels, and seven channels driven power output results being bandied about for receivers and some five and seven channel driven numbers are lower than the receiver's rated power output. Is it simply a case of the FTC only requiring manufacturers to meet the power rating with one or two channels driven?

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#288972 - 01/27/10 11:07 PM Re: Distortion [Re: ]
Ken.C Online   content
shareholder in the making

Registered: 05/03/03
Posts: 17789
Loc: NoVA
AFAIK, the FTC only requires manufacturers to meet it with one channel driven.
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#288976 - 01/27/10 11:13 PM Re: Distortion [Re: JohnK]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6721
Loc: The Peoples Republic of Il.
 Originally Posted By: JohnK
Nut, yes all receivers do put out their rated power; this is governed by FTC regulations, and failure to do so would be a violation of the law.


If this is so how do manufactures get away with things like this.

Onkyos published specs for the 807.

135 W + 135 W (8 ohms, 20 Hz–20 kHz,
0.08%, 2 channels driven, FTC)
Center 135 W (8 ohms, 20 Hz–20 kHz, 0.08%,
2 channels driven, FTC)
Surround L/R 135 W + 135 W (8 ohms, 20 Hz–20 kHz,
0.08%, 2 channels driven, FTC)
Surround Back L/R 135 W + 135 W (8 ohms, 20 Hz–20 kHz,
0.08%, 2 channels driven, FTC)
Dynamic Power 300 W (3 ohms, 1 ch)
250 W (4 ohms, 1 ch)
150 W (8 ohms, 1 ch)
THD (Total Harmonic Distortion) 0.08% (Rated power)

Then it tested like this.

Onkyo TX-NR807 A/V Receiver:

HT Labs Measures

Five channels driven continuously into 8-ohm loads:
0.1% distortion at 105.5 watts
1% distortion at 122.0 watts

Seven channels driven continuously into 8-ohm loads:
0.1% distortion at 29.9 watts
1% distortion at 33.0 watts


This isn't a bit misleading? Is it all in the wording from the manufacture? In each case Onkyo rated the specs with 2 channels driven.

One would be thinking they would be getting a true 135 watt (all channels driven) receiver but in reality they wouldn't unless it was with only 2 channels driven.
_________________________
Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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#288977 - 01/27/10 11:13 PM Re: Distortion [Re: Ken.C]
htnut
Unregistered


 Originally Posted By: kcarlile
AFAIK, the FTC only requires manufacturers to meet it with one channel driven.


Ahh, I see. I'll have to remember to qualify my statement next time with "under normal or common listening conditions."

I guess from their (FTC) standpoint it does make sense since they are regulating power for safety reasons.

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#288987 - 01/28/10 12:07 AM Re: Distortion [Re: bdpf]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10403
Bruno, 85dB and 105dB are absolute loudness level numbers(at the listening position), they're not in "reference" to something else. The reason I happened to pick those two was that 85dB(at most)is what can be used for a long term average listening level without causing permanent hearing loss(note the EPA/WHO suggested limits here for "community" sound, not in the workplace(first two tables) where some long term loss is considered acceptable(by some). The most dynamic recordings may have peaks as much as 20dB above the average level and this is the reason for the 105dB number. Note that it's largely classical items(some of which I have)that may have that wide a dynamic range. Many almost uniformly loud pop recordings have a very small dynamic range. Rather amusing was an article in my AES Journal a few months ago which described tests of various recordings to measure the thermal stress their dynamics imposed on speakers. One very loud pop recording measured out with a dynamic range of essentially zero dB.

The dB volume can't typically be referenced to 0dB in most cases. Movies are supposed to have a maximum level in the speaker channels of 105dB when the receiver is properly calibrated at the 0 point. Of course, most of the time the level of movie sound is far below that maximum and during a relatively low level segment the sound level with the receiver at 0 might be 50dB. Typically, few listen to movies at the "reference" 0 level at home, but at 10dB or so lower than that. Music, as compared to movies, has no established reference level and different discs can have widely different sound levels if someone listened with the volume at 0.

So, as was said, volume can be measured with an SPL meter, but can't be very accurately judged from receiver volume settings.
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Enjoy the music, not the equipment.



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#288989 - 01/28/10 01:00 AM Re: Distortion [Re: ]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10403
Nut, first you're mixing the FTC regulations up with UL(Underwriters Laboratories)testing for fire safety. The FTC regs are purely a "truth in advertising" movement to combat inflated power claims which were rampant in the 1970s. What's rather ironic is that this is the only area in audio which is governed by relatively specific and mandatory regulations which we can rely upon, yet some audiophiles who're willing to take seriously unsupported claims about the "sound" of amplifiers, players or even pieces of connecting wire view with suspicion amplifier power ratings.

The text of the regs can be found here . There's no specific number of channels which have to driven simultaneously given in the text, but the FTC interpretation in practice is to require that it be at least two(one isn't acceptable)and most manufacturers follow that for their basic rating, so two is to be presumed unless stated otherwise. They're free to base their rating on an "all channels driven" and the few that do, make it clear that they've done so. In real world home use the all channels driven number is unrealistic and all channels are never driven at full power for five continuous minutes. Audioholics, for example, makes this clear and tests with one and two channels driven as being more in accord with actual requirements outside a testing lab.

Tests of receivers by Sound&Vision, Home Theater Magazine, etc. almost without exception show that they meet the official(usually two channel)rating.
_________________________
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Enjoy the music, not the equipment.



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#288991 - 01/28/10 01:15 AM Re: Distortion [Re: Wid]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10403
Rick, discussion similar to the two replies above has taken place quite a few times over the years here. The published Onkyo specs clearly(more clearly than many others, in fact)state the two channel driven basis for the rating. The HT Labs test on that basis(which you didn't quote)show that the spec was met. Those who don't study what is meant by a power rating have no right to use their own interpretation of what it should mean.
_________________________
-----------------------------------

Enjoy the music, not the equipment.



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#288995 - 01/28/10 03:11 AM Re: Distortion [Re: JohnK]
Ukiah Offline
enthusiast

Registered: 10/17/09
Posts: 38
Loc: Ontario
"Those who don't study what is meant by a power rating have no right to use their own interpretation of what it should mean."

Would you please explain this comment.
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#289001 - 01/28/10 07:41 AM Re: Distortion [Re: bdpf]
Murph Offline
axiomite

Registered: 10/05/06
Posts: 6860
Loc: PEI, Canada
 Originally Posted By: bdpf
Like I said, this is not my typical listening level due to my room size (20x11ft). I was just curious. But lets assume I would take my setup to a party with a bigger space, let's say 200x200ft, in that case I would need this kind of level to fill up the room, so I guess in that case I would need separate amps.

JohnK, when you talk about 85dB or 105dB, what is the reference used? How does that translate related to whatever is displayed on the receiver? Typically, what is the volume in dB when the receiver is displays 0dB? I apologize if that seems very basic but I am very new to this and am trying to understand. Thanks.


Hello Bruno and welcome. I didn't see an answer to your first question her so I'll chime in.

M80s are POWERFUL and robust speakers for the home audio market. They can handle clean power output from just about any amp out there designed for normal home usage. That being said, the scenario you describe above, a 200x200 foot room (thus probably also a high ceiling too)is not a 'home environment.' At least not a reasonable definition for the term home audio.

As good as the M80s are, if you are looking for gear for such large spaces, perhaps to DJ weddings, party's etc., then you need Professional audio speakers and professional audio gear designed for large areas. Picture a wedding you have been at with a professional DJ (not a basement living teen making a buck, no offense to basement dwellers. \:\) ) You will see large heavy speakers, professional amps of large sizes and balanced cables hooking it all together.

I'll also attempt to simplyify the in depth discussion above since I too have the advantage of being relatively new to this field.

A xxx Watt amp will cause distortion in any speaker if it is driven to try and produce loudness levels that it wasn't designed to do. This is a limitation of the amp, not necessarily the speaker as the amp begins to clip when it's pushed too far and this clipping from the amp can actually damage your speakers.

Your speakers are rated for 400 watts and tested for actually well beyond that so you can't kill them by hooking up a more powerful 'home' amp and letting it blast (although it will kill your ears.) However, you can kill the speakers by trying to go louder than your amp is capable of playing.

Also, for the last question. zero db on one amp is not the same sound level as on another amp. Also, when you set your amp at zero, the measurable sound level will vary depending on how close you are to the speakers and a lot of other factors. Also, it can vary depending on the CD or DVD you are playing. Recordings tend to vary greatly as to how much volume they produce so you often have to adjust when you change material.

Thus the question of what sound level is produced at zero is not really answerable. I suggest you do what I did. Purchase a db meter for 30 dollars or so, sit in your listening position and turn the amp volume to zero.

Personally, in my small room, my particular amp and speakers, I can not tolerate the loudness at a zero level. I think I might even be able to detect a little clipping there at that level with my 130 Watt/channel amp. That, or my ears are just rebelling against the insane loudness. The loudest I ever push my particular system is about -15 and even then, not for long. But again, these numbers mean nothing to you and your setup. It will be very different.

It's not the accurate detail of the above posters but hopefully it helps to simplify things a bit.

While not entirely accurate because every room and scenario is different, this wattage calculator is fun to play with to display how little power you need to listen at 'safe' listening levels and how the math works against us to require ridiculous amounts of power to play at extremely loud levels or when distance comes into play.


_________________________
With great power comes Awesome irresponsibility.

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#289007 - 01/28/10 09:26 AM Re: Distortion [Re: Murph]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6721
Loc: The Peoples Republic of Il.
So as long as the Onkyo is used as a two channel receiver they meet the specified specs and have met the FTC regulations, nice.

We all know we can trust the government to keep thing on the up and up.

Here's the omitted part which shows they do indeed meet their stated specs.

 Quote:
This graph shows that the TX-NR807’s left channel, from CD input to speaker output with two channels driving 8-ohm loads, reaches 0.1 percent distortion at 143.6 watts and 1 percent distortion at 168.7 watts. Into 4 ohms, the amplifier reaches 0.1 percent distortion at 240.2 watts and 1 percent distortion at 267.9 watts.

_________________________
Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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