Axiom Home Page Forums General Discussion Technical Questions Distortion

Hi,

I've had my M80s for 3 weeks now. Tonight, being alone, I finally got an opportunity to push them to see how loud they could get. I have the Denon AVR-890 which is 105W/channel. Depending on what I was playing, I found the sound to start distorting anywhere from +3dB to +8dB. I asked in a previous thread why would some people use an external amp (usually more powerful) instead of their AVR amp, what was the benefit, if it was to prevent distortion at high level. JohnK was kind enough to respond with the following:


So now my question is if 100W/ch is enough, why are my M80s starting to distort? My receiver goes up to +18db, why can't I push them to this level without distortion?

Don't get me wrong, +3db is more than I need for my room size, and I will have them very rarely at this level, however if I would have a much bigger room, that would have been a problem.

Also, I played at +5dB for about 45min (neighbor, if you're reading this, I apologize ) and even though the receiver didn't shut off, it got very hot. Is this normal?

Thanks,

Bruno

Wow, that is loud. I don't think JohnK realized you were playing that loud (he said ~ 85dB was OK but you are well exceeding that). You will need an amp.

No one needs any more than a 100 watt receiver, it has been said, so it is so

Bruno, the numbers on the receiver volume control don't accurately measure the actual sound level that's being achieved. This has to be measured with an SPL meter. If you do this it's highly likely that you'll find that peaks played at a safe level(say about 105dB)are handled well by your 890. And no, you certainly can't assume that you can turn the volume up to +18 just because that number is on the scale. With some input levels(whispers would be okay)that could far exceed the capability of the receiver(and your ears as well).

Maybe in theory, but not all receivers put out their "rated" power in reality. If one wishes to listen at 115dB levels then 100W won't cut it. Not everyone is sitting 1m / 3ft from their speakers either.

If you know me you know I wasn't serious. I have 2 300 watt amps connected to my M80s. I am and always have been an advocate of buying as much power as you can comfortably afford.

My apologies, I am still new here and getting to know everyone :).

No problem and no need to apologize.

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.

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.

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?

AFAIK, the FTC only requires manufacturers to meet it with one channel driven.

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.

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.

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.

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.

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.

"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.

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.

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.

bdpf,

Welcome to the forum. Your M80s are capable of handling 1100-1200W continously as tested by Axiom, and I can tell you first hand that they can produce prodigious SPLs without distortion (I run them with the A1400-8). It sounds to me that your are getting clipping distortion when turning up your receiver too high. You can damage the tweeters in the M80s that way so I would not recommend doing this. Your receiver should be able to provide measured spl of 75-85dB in your room without distortion.Remember that each 3dB increase in volume will require twice more power from your receiver even though the difference you hear may be small. If you are getting distortion at 85dB as well, unloading some of the power requirement to sub(s) will help the internal amps of your receiver to better reproduce transient dynamic peaks. Wid, JohnK, and Murph have also made excellent points (some of which should be a sticky but there is no provison for this here, unfortunately).

Hi Bruno,

Much good advice already given, but I'll address a couple of your questions. Your Denon gets very hot when you are driving it to very loud levels because the output transistors are driving 4-ohm loads, the M80s, so more current flows through the output stage and it heats up (power is measured by both voltage and current).

The Denons do not seem to have thermal sensors on the output stage, which is why they will drive the M80s whereas some other brands historically will not. Older Onkyos used to shut down very quickly when driving M80s, either because of overly jittery protection circuitry that sensed too much current flow or because the output stage got hot. Newer Onkyos are better.

Consider "0 dB" on your volume readout as a rough guideline that you should not exceed, or if you do, you may risk "clipping" the output stage or incurring increasing distortion that may become audible.

Manufacturers still get away with a lot. In the old 2-channel days, most all receivers drove 4-ohm loads without difficulty.

In current av receivers, there are 7 internal amplifiers, not two, and dissipating heat is a big issue, so many manufacturers will recommend you do not connect 4-ohm speakers, or they set the protection circuitry to shut it down, on include an impedance switch that on the 4-ohm setting severely limits the power/current flow through the output stage (much reduced power output).

As to subjective volume sound levels measured at your seat, "85 dB" is interpreted by most listeners as "quite loud"; "95" dB as "very loud" or "twice as loud" as 85 dB; and over 100 dB, extremely loud. By the way, the levels I've measured of orchestra and chorus in New York at Carnegie Hall or various opera houses, never exceed peaks of 105 dB SPL (sound pressure level).

Rock concerts can be absurdly loud--dangerously so--and may approach 122 dB, not far from the threshold of pain.

Oh, ignore specs of "Dynamic Output"; this is totally bogus. It's quoted to get the numbers up. No regard to distortion, always a single frequency. Useless.

The correct spec is Dynamic Headroom and is quoted in dB, which most consumers do not understand, so it's never quoted.

Regards,
Alan

I know you do not have an SPL meter (measures dB basically) but those speakers at + anything must be ridiculously loud. I have the same receiver (2310) and only little W22's and the loudest I have ever had it for about 30 seconds was +3. Normal loud listening is around -5 to 0, and even that is somewhat rare.

I do have to agree you are probably limited by the amp in the 890, as opposed to the speakers. Really though, listening that loud over time won't be good.

EDIT: I just saw Alan's point about rock concerts... I've been to more than a few, and they are freakishly loud, but I must admit they don't seem as loud as about ten years ago. One show, I was at a small venue and I was standing beside (two feet away or so) one of the floor speakers beside the stage for a good hour. Being so close and not wearing earplugs was stupid, my right ear was ringing for four days, no joke. Don't want to go through that again

I tried cranking my 2809, well into "+" territory, but it became nearly unlistenable as it clearly became too much for the amp, too much for the room, and too much for my ears. With a separate it most surely would have sounded better, but it would still have been too much for my room and ears.

I was just putzing around on Peavey's website and and came across this chart that I thought I'd pass along since many people have discussed or. in fact, warned others about high noise levels. It reads...

The US Gov't Occupational and Health Administration(OSHA) has specified the following noise level exposures:

Duration Per Day in Hrs....Sound Level dBA, Slow Response

8.....................................90
6.....................................92
4.....................................95
3.....................................97
2....................................100
1 1/2...............................102
1....................................105
1/2.................................110
1/4 or less.........................115


*** They also cautioned that everyone is a little different, and some may be more prone to higher noise levels, the chart is a guideline.

Thank you all for the great input. As many of you said, I was probably experiencing clipping from the amp and as Alan said it's probably why the receiver got very hot.



Thanks, I didn't know that, I always thought it was the opposite, that you could damage the speaker if giving them more power than what they are rated for. Now let's say if a 100W amp is able to provide let's say 100dB without clipping, is it correct to say that a 400W amp would only be able to provide 106dB without clipping?


It might have been a good idea for the Receiver manufacturer to limit it to 0dB if they cannot handle more to avoid ignorant people like me damaging their speakers.



Indeed it was . It would have probably been bearable in a room 3x my size. Usually, the loudest that I will have it on will be -10dB and not for too long as it is already very loud.

Adrian, those numbers should be ignored if the topic is listening to music in the home. As I commented in my earlier reply, those workplace numbers accept some level of long term hearing loss, while this should be totally unacceptable in the context of home listening. The EPA and World Health Organization numbers that I linked are substantially lower for "community" levels rather than the workplace. For example, at 115dB the limit is zero.

I missed your link the first time John, just saw it now. Regardless what statistics are used, 115 db is dangerous...I can't imagine what sound levels the concerts were that I used to go to in high school.

Gotta agree on the insane concert levels. My problem with it is that I wear earplugs, which attenuate high frequencies more than lower ones, so the concert doesn't sound as good as it might.

Etymotic make linear ear plugs... they also make excellent headphones and headsets, like the HF2 set I have for my iPhone.

Oh, that is sweet. If I was still going to concerts, I'd buy those in a heartbeat. But now I am old and have small children.

That just means you take the small children to the concert!

I got free Motley Crue tickets and saw them on Sunday night, lots of kids there, it was awesome. Mullets and 80's hair galore, even head bands... It was magnificent. I won't get into the "women" there.

Old, I will trade ya Ken, your not in the 40's club yet. lol