Confused about dB's, Sensitivity....

[joel2762]

I was recently looking at a Decibel level chart. I tried to upload but it was too big. This chart states that 90 Db can be dangerous under constant exposure. Okay. So my speakers are rated at 89 dB/1 watt. Does this mean that at one watt from my reciever my speakers can almost damage my hearing!? What's all the extra power there for then?? I don't get this...There must be something more to it that I don't get here but i'd like to know what it is. Thanks in advance!

[This Guy]

After 8 hours 90 decibels will hurt your hearing. Most of your listening is done with one watt or less of power. And don't tell me you don't crank those speakers on occasion. Look at it this way, to go twice as loud (10 decibels) as 1 watt you need 10 watts, and to go twice as loud as that you need 100 watts. That will make your speakers 110 decibels loud with a 100 watts, at one meter. Subtract 6-8 dB because of dispersion (distance) and add maybe 2-3 decibels for room gain and your speakers are about 104 decibels max at your listening position. You can listen this loud for like an hour or so on occasion and get temporary hearing loss. If you do this every day you'll get permnent hearing loss is certain frequencies.

-Joey

[RGA]

Yes 1 watt will achieve 90db at 1 meter away. Most people listen 2-3 meters back and you can roughly subtract 3db with each meter.

Basically if you are seated 3 meters back you'd need about 4-10 watts to get 90db at your listening position. This is a gross generalization and depends on how big your room is and the type of speaker.

This is why the 10 Watt Sugden A21 sold from 1968-1989 and then when speakers became hard to drive Sugden used new better heat handling parts to increase the pure class A solid state amp to 25 Watts which quite happily drive the Totem Arro's 4ohm 86db sensitive at quite solid volume levels.

Watts are the biggest crapola spec on the market especially when the Sugden has bass control and depth with speakers that my old 125Watt Pioneer Elite Reciever would flab up and just plain suck the life out of music.

[poneal]

Well stated RGA! I get chagrined when people post that they need 200+ watts because it just dont play loud enough. I'm pretty sure if they use all that power on a regular basis they are having hearing loss.

[Woochifer]

I was recently looking at a Decibel level chart. I tried to upload but it was too big. This chart states that 90 Db can be dangerous under constant exposure. Okay. So my speakers are rated at 89 dB/1 watt. Does this mean that at one watt from my reciever my speakers can almost damage my hearing!? What's all the extra power there for then?? I don't get this...There must be something more to it that I don't get here but i'd like to know what it is. Thanks in advance!

You're learning! All that extra wattage makes for great marketing print, even if in reality the capability is never used. Also, keep in mind that those wattage figures,especially for multichannel amps is rarely if ever expressed with all channels driven. So, that 100 watt x 7 channel receiver you see advertised at most stores is not really a 700 watt receiver (the power consumption stat on the back of the unit is usually a dead giveaway that it's a physical impossibility for the unit to output 700 watts). In addition, there are myriad ways for stat sheets to distort the actual output figures, like posting output levels with high distortion or using low impedance tests. The thing to look for is a 20 Hz-20 kHz test done at 8 ohms impedance -- that's the standard FTC test used for mono and stereo amps.

As stated earlier, it's true that your speakers will output to very high levels with just one watt of output. The only time you'll really need a lot of wattage is if you're going with a low efficiency speaker or you're in a large room.

The perceived loudness basically doubles with every 10 db increase, but in order to get that doubled loudness, the wattage demand increases tenfold. Normal listening levels are about 75-85 db, typical speakers need less than one watt per channel to drive to that point. Getting that same speaker up to a concert level volume of 95-105 db would require between 10 and 100 watts per channel. That range is really where the extra wattage is needed. But, for everyday listening with relatively efficient speakers, the amp will make a minimal difference in the overall sound quality compared to differences between speakers and room acoustics.

[joel2762]

Thanks alot, I get it now. That's pretty interesting though because you'd think you'd need more than a watt to drive speakers loud. But I guess that's not true! My reciever manual states that the volume control increases by 1 dB each step. I listen to it around 45-50 depending on the level of the recording pretty much everyday. I don't crank it to dangerous levels, it'[s only a small room but every now and then on the weekend might put it a little louder for a little while. I just like bass, before I had my subwoofer, I could not achieve the bass I wanted from my speakers without having it too loud. Now I have a sub it all blends in.

[kexodusc]

This was a really good thread, I don't think this question gets asked enough, especially by newer audio enthusiasts or people looking to build their first systems.
I get people asking me all the time and I hear it at places like BestBuy and Sears, "is it worth that extra hundred bucks to get that extra 10-20 watts?"
They perceive the difference between 80 watt and 100 watt receivers as a factor of 20%...You wouldn't believe how many people drop 100-200 bucks extra here thinking they need it.
I always tell them that unless there's some other features that they absolutely need or like on the receiver, if everything else is equal, they've got better places to spend that 100-200 bucks on than going to 100 watts per channel. Geez, I love it when newbies look at Harmon Kardon receivers with 35 or 45 watts/channel and think "rip-off", then proceed to buy the 120 watt/channel Kenwoods.

Why would you drop 200 bucks for more power that isn't going to make a big impact and you don't really need?
Some brands are really bad, they up the power by 5 watts, add 1 more a/v connection, a DSP or two, and charge 150 bucks more for the receiver.

[magictooth]

Hi!

I thought that I should post a slightly contrarian point of view. While I agree with everything that the above posters have said, you should be aware that the extra watts are not absolutely wasted.

For the most part you have a desired listening level - say 75 dB. However, the one thing that the other posters haven't mentioned is the dynamic range that most movies have. You may like listening to conversation at 75 dB, but there will be times when you get a spike in volume level such as in an explosion or even something simple like a heated argument. At those times, you want to have the extra power available to fully express the dynamics in the soundtrack.

[kexodusc]

Hi!

I thought that I should post a slightly contrarian point of view. While I agree with everything that the above posters have said, you should be aware that the extra watts are not absolutely wasted.

For the most part you have a desired listening level - say 75 dB. However, the one thing that the other posters haven't mentioned is the dynamic range that most movies have. You may like listening to conversation at 75 dB, but there will be times when you get a spike in volume level such as in an explosion or even something simple like a heated argument. At those times, you want to have the extra power available to fully express the dynamics in the soundtrack.

That's a good point magictooth, and I agree with your logic, I'm just not convinced that a 5 or even 10 watt per channel difference will be of much value once you get over the 40 watt range for spikes in volume in most "moderate" sized home theater or stereo setups.
I'm only basing this on my past experience with 2 of my Marantz receivers...I ugraded to an extra 15 watts per channel from 90 to 105, and didn't notice a difference at all in performance or anything, and was kind of disappointed that I dropped money on the extra power after I realized I rarely ever come anywhere close to using it's full potential. I could be wrong because I never compared the receivers back and forth playing the same movie against each other, I was just expecting the extra power to improve sound quality or really shake the house.

[joel2762]

I see now, so the extra power really doesn't matter that much in most cases. My Sony is 100 watts per channel. I know that it's not really that powerful but it does job and plays loud enough for me. I noticed with the old Realistic reciever we used to have before upgrading to surround, it sounded more like. Powerful. Like real power. But the Sony's still good all the same. It's cool though, I never would have thought that speakers could go that loud with 1 watt! But one thing that's confusing me...If my speakers say 15-120 watts, how can they go to nearly dangerous levels with only a watt. What's going on that i'm not getting...

[F1]

Every increment of 3dB you need to double the power, so here goes
1W - 89dB (at 1 meter)
2W - 92dB
4W - 95dB
8W - 98dB
16W - 101dB
32W - 104dB
64W - 107dB
128W - 110dB

As already stated, you need to substract few dB if you listen farther away from the speaker. The wattage rating on the speaker is probably exagerated to compensate exagerate rating of common amplifier/receiver. If your speaker is rated at max 120W, it probably means that the speaker can handle a burst of around 110dB before it breaks.

[kexodusc]

Some Sony's aren't too bad. The problem most people have with Sony is their inconsistency across product lines. They've really started to cheapen some of their products lately too, but they don't market themselves as "high-end" really anyway. I've been burned a few times by some of their products but some aren't bad. I bought my mom and dad an older Sony STR DE635(I think) off e-bay to replace my older pro-logic Marantz...it really sings in stereo mode, 80 Watts/channel both channels driven, 20Hz-20kHz low THD and would go toe-to-toe with that Marantz easily....the power really dies once you drive all 5 channels, and the distortion rises but it's still more than loud enough for them and the distortion is more than tolerable for HT playback anyway. It does have cheap feel compared to my Marantz and Yamaha gear, the back is quite flimsy etc, but it works, was a steal for me and they're happy.
What really ticked me off is Sony decreased the dynamic range on it's replacement products to 40hz with more distortion. They lowered the price and addes some more DSP's and inputs. The power supplies appear to be cheaper too, but I think this line is made more for entry level HTIB setups now than larger speakers.
If you ever have a technical problem though, Sony's got some "issues" to say the least.

Joel2762: It's never easy matching speakers to amplifiers according to power ratings. Too many variables are often used to arrive at the desired numbers. I destroyed a set of old Wharfdales that were supposedly good up to 80 watts with a 35 watt Harmon Kardon amp way back. My own fault, but it was hard lesson that tought me not to always rely on specs. If you really feel the need to crank your system, don't just give it the juice, go up in small steps for a good 5-10 minutes at a time...if you notice any clipping or funny sounds cut back the juice immediately.

[Sir Terrence the Terrible]

Before we get locked into believing we don't really need that much power, you have to think in term of frequency versus power. If you are talking about 1khz as being the reference tone, then F1 power chart makes since. But as you plummet in frequency, in order to hear the same volume as the one attained at 1khz, the power must increase dramatically. 100 watts at 20hz doesn't produce nearly the same amplitude as 100 watts at 1khz.

At this point you now have to think of headroom. Especially with film soundtracks which can have extreme amplitudes swings(as much of you complain about so frequently) especially in the deep bass area(film soundtracks are the only audio genre to have very deep bass frequently and very loud). A full scale explosion may require ten to twenty time the power demand to reproduce the deep bass frequencies cleanly, with no compression or clipping.

I alway tell my clients don't think of getting just enough, you always need just a little more to play cleanly during peaks. Just enough during peaks will get you compression, just a little more will keep distortion down, clarity up, and compression out.

[kexodusc]

Sir Terrence, I agree with your points. However I would point out that most setups I've seen today can be classified in one of two situations:
1) The sytem includes a subwoofer which generally has it's own amplifier, reducing the need for power
2) The system includes main speakers which are very capable of reproducing low, extended bass frequencies - I would suggest this scenario often finds audiophiles with more expensive, better performing speakers, which almost certainly have a more powerful amplifier anyway.
Not to discount what you said, but I certainly wouldn't want to mislead people who are buying a home theater in a box system that that extra 200 bucks to get to 100 watts per channel is worthwhile when their small cube speakers will have difficulty with 80 watts.

It happens too often in my opinion, and let's face it, us men are generally impressed with "more" of just about anything, especially power. I can't really blame a salesperson for trying to earn a buck.
At the same time, having more power probably gives you more upgrading options, and from what I've seen, often means a better power supply, which isn't a bad thing.

[spacedeckman]

Numbers make the most convenient comparisons for audio products.
Numbers are typically the most useless for comparisons of audio products.

As soon as you start getting hung up on numbers when you buy audio products, that is when you start screwing up. You see, different companies see different things when they publish specifications. Some see a marketing opportunity, some see an opportunity to fudge a bit, and others try to convey something useful. Unless you know where the manufacturer is headed, you are chasing the wind.

Speaker sensitivity is a bit misleading as a concept to the uninitiated, but is a very common place for very respectable speaker companies to "fudge" a bit. A couple of dB between friends doesn't really hurt anything, but often you will find something on the lines of double that which is starting to make a difference. As Terrence brought up, that 1k thing kind of gets in the way too. As you go deeper, your power demands increase, but still, you can go a long ways on a handfull of watts, even if the hand was involved in an industrial accident and a finger or two is missing. Speaker power ratings? Give me a break. Take a 400 watt speaker. Hook it up to a 100 watt receiver. Crank it up. Toss the tweeter. What did that rating gain you? NOTHING. It can be useful with small speakers, or when you are employing big amplifiers at silly volumes for extended periods of time. Other than that...not very useful. How many people does the number help? A fraction of a percent. Speaker frequency response? The raw number is often bogus enough, but how many companies put the size of the "window". A speaker that is 30-20k +/- 20dB is sure to be a real "winner", so the +/-20dB "conveniently isn't listed. Impedance? Nominal is really cool...sort of (only a hint of sarcasm here) Many companies are really good with this, and with mainstream speakers it is getting to be much less of an issue. Most of these companies have really worked on "dummying down" impedance curves to work with the current generation of fairly crappy receivers.

Receivers? 100watts...sure...at 1k. What the heck kind of rating is that? I remember being disgusted with a Sony entry level piece 17-18 years ago that listed 40-20k. 1k is not only a whole lot worse, it is far more openly accepted by those who don't have a clue. I vote for a total ban, same for power ratings at 6 ohms. Panasonic has one that does both. 100watts/1k/6ohms/1%THD...think we may have some engineering problems here? What's wrong with calling it a 60 watt receiver, or even 50 and make it work? Idiots want 100 watts. MARKETING!!!! I've spent most of my audio existence with 50 watts or less, and I bought my first real system 24 years ago when I was in college. I still have the 20 watt receiver I bought back then. I've nearly doubled to 35 watts today. So what!!! I only wish it was possible to go back to the days when it was okay to make a 40 watt receiver that could actually drive a real world speaker load and make some bass. The world was a better place then. Quality over quantity, because quantity is a bunch of crap. While you are at it, make sure your video switching isn't goofing up your video quality, and the things you paid for actually do what you expected. You are most often much better served with a smaller receiver from a reputable "upscale" company than a "big" one from a mass market company.

So Joel, the more time you spend fretting about numbers, is less time you spend listening to your system. Don't sweat the Sony. Sony is all about learning curve. If you like audio, you've already made that mistake and you will be ready to move on in the future. For now, it works, and enjoy it. A better piece lies ahead. If you are perfectly happy with it, please be so, and don't worry about the numbers stuff. If you are hanging out here, you have already started a journey that could bring you places you never imagined. This is all about fun. But, this was a good question because the more you know, the more fun you will have in the future...and the more you will understand how much more there is to learn. Also, beware those who know everything, they are too dumb or closed minded to realize there is always a ton of stuff we don't understand. Discovery is one of the best things about audio. And, thanks for letting me vent. I feel better now.

[Sir Terrence the Terrible]

Sir Terrence, I agree with your points. However I would point out that most setups I've seen today can be classified in one of two situations:
1) The sytem includes a subwoofer which generally has it's own amplifier, reducing the need for power
2) The system includes main speakers which are very capable of reproducing low, extended bass frequencies - I would suggest this scenario often finds audiophiles with more expensive, better performing speakers, which almost certainly have a more powerful amplifier anyway.
Not to discount what you said, but I certainly wouldn't want to mislead people who are buying a home theater in a box system that that extra 200 bucks to get to 100 watts per channel is worthwhile when their small cube speakers will have difficulty with 80 watts.

It happens too often in my opinion, and let's face it, us men are generally impressed with "more" of just about anything, especially power. I can't really blame a salesperson for trying to earn a buck.
At the same time, having more power probably gives you more upgrading options, and from what I've seen, often means a better power supply, which isn't a bad thing.

Kex,

My point was not to get our fellow hometheaterans(is there such a word?) to run out and buy a amp that is 200watts+5 for a subsat system. My point is to simply illustrate that because of the fletcher munson curve we have to consider looking at how many watts are required by FREQUENCY, and not just by some arbitrary numbers, or by what is reproducing the bass(whether its mains or a sub)

There is a reason why most sub amps wattages lie in between the 125-250 watt range and above. That is because the power requirements for bass frequencies are so much more than for treble frequencies because of our hearing insenstivities at the freguency extremes.
So whether you use a sub, or have full frequency mains, you still need substantial power for clean low bass reproduction. If you look at it this way, then asking a cube that struggles with 80 watts to be used with a 100watt amp is unecessary. You know the cube won't be able to reproduce deep bass anyway!!

I am not for power just for the sake of power. I am for power where it is needed. No use in having a Porsche if you only drive it on city streets, right?

[joel2762]

Hey everyone. Thanks for all the comments. I belive my Sony drives 40Hz-20Khz with 0.09% THD...It sounds good enough for now. It's only a small room, it does fine in here. I can't drive it to clipping because i'd go deaf! It's a great system anyhow. Might not be the audiophile gear but it sounds great! It does sound a little clearer in 2CH mode rather than DPLII. But it still sounds good. I crank it lots of the time but never into distortion. I don't think it can be played that loud in this room anyway but sometimes the bass can get distorted at high levels but that's just waht happens! Thanks for all the help I learned a lot!

[joel2762]

As spacedeckman mentioned about the video swithcing goofing it up. It only has composite switching, but when I got it, I knew I wasn't going to use the internal switching anyway. I have my DVD player hooked directly to my tv using S-Vid, hopefully going to change that to Component soon. I use the reciever switching for my VCR and the A/V cord from a digital camera.

[kexodusc]

Sir Terrence,
I totally agree with you...I think we're just making 2 different points...I had on older H/K receiver that was only 20 watts or something...I bought it at a yard sale for 20 bucks, I still have it in my garage and I'm pretty sure it still works, anyway...it was great in my bedroom, but when I put it into a living room, my volume requirements went up and the bass did suffer substantially. I thought it was my speakers, but an upgrade in that department still left me wanting in the bass frequencies.
Lesson learned.

Anyway, we should have audiophile police or something that goes to BestBuy and Sears to advise people not to put their faith (and money) into the hands of part-time salespeople.

Man, if the internet was around in the early 90's I would have saved hundreds of dollars on audio gear!!!

Just out of curiosity, what is the lowest frequency the average human ear can detect?
I've never owned a 40Hz-20,000Hz amplifier, mine have all been 20 to 20...do they really lack that much bass?

[F1]

...........
Just out of curiosity, what is the lowest frequency the average human ear can detect?
I've never owned a 40Hz-20,000Hz amplifier, mine have all been 20 to 20...do they really lack that much bass?

I think it's not like the receiver has no output below 40Hz, but the company try to minimize THD number. 40 - 20K Hz @ 0.09% THD may translate to 20 - 20K Hz @ 0.2% THD or bigger, which doesn't look good.

[kexodusc]

Ahhh...okay...maybe that's the case then, F1, the bass just gets really sloppy below 40Hz. I've just assumed it was cutoff below 40Hz.
Does anyone know if that would make difference if the bass is cutoff below 90 Hz and output through a subwoofer. I have an opportunity to buy a new Sony Receiver for dirt cheap, I was thinking I'd give it to my little brother, he's moving out this year.
If the Sony's really lacking in that frequency range I'll give him my Marantz when I buy my RX-V1400 soon, but it's a pretty pretty bare-bone HT receiver, decodes DTS few DSP's...limit connection options.
Alternatively, he could output the bass from his DVD player straight...it's basic panasonic, I don't know how that would sound.
Anybody have any advice? Thanks.

[spacedeckman]

Sloppy bass isn't due to rating, but could be poor amplifier, speakers, room problem, or a combo of the three.

The Sony is doing what it can with what it has available. It doesn't have a good power supply, nor does it have very good output devices, it doesn't have the best circuit design (designed for fewest parts and high tolerance for component values) to contain cost. That's what makes them a beginners piece, and many people graduate to better stuff.

If your speakers are easy to drive, your room is small, and you are using a sub (and rolling off mains as you stated) you will get the best you can get from it.

Happy listening.

[kexodusc]

So...what you're saying is "how much do I like my brother?"
He's only getting an HTIB kit, my Marantz would be overkill for his purposes, and I could probably hawk it for some good coin on e-bay.
Aw, man, since you put it like that, I'd feel guilty doing that now!

[joel2762]

Kex, human ear detects down to 20 Hz. But anyway. I find the Sony really good. It might not be audiophile quality, but if you can get one dirt cheap, it's definetly worth it. I find mine great. Okay so it might not have the best power supply or whatever, but I really like mine. The four-position button let's you adjust settings easier than any other reciever i've seen. As for the 40Hz-20Khz stuff, My front speakers only go to 50 Hz anyway so the amp's rating doesn't matter, I have a subwoofer and my system goes fairly low, and sounds great with music. IT might not be the best for large rooms but for smaller rooms it's great. If it's dirt cheap, go ahead I say

[kexodusc]

Well, it's not quite dirt cheap, but he's only running a satellite/sub system off it anyway...I can sell my Marantz for about 100 more than it'll cost to buy me this. STRDE845 is the model number I think. That extra hundred is going towards my new Yammie.

He'll be happy with it I'm sure, he's only got a Kenwood bookshelf-system right now anyway.